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EPE 2002-05 - Parent Directory

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1. Simple boxes are fine for projects that require a small to medium size enclo sure but they are often a bit awkward when applied to larger projects Instrument cases are usually the better option for larger projects Apart from the fact that they look the part they gener ally provide better access to the interior of the case which makes it easier to work on larger and more complex projects Instrument cases vary considerably in design but many have a base sec tion combined with front and rear pan els The lid and sides are combined in another section Ideally the case should have removable front and rear panels as this makes working on the panels very much easier While it is normally acceptable to use any case that is large enough it is as well to read the construction notes in the article There may be other consid erations and in some applications plastic cases are not suitable while in others a metal case must not be used Some projects rely on the metal cas ing to act as a heatsink or to provide screening or earthing Other projects such as radios require plastic cases that do not provide screening It is important to heed the advice when an article stipulates a certain type of case In most instances the exact type of case used is unimportant and it is then a matter of choosing one that is big enough and within your price range In general simple boxes are substantially cheaper than instrument cases an
2. made up kits are supplied ready to start The top up kit is for readers who have already purchased kit 1a or 1u The kits do not include the book Hardware required All systems in this advertisement assume you have a PC 386 or better and a printer lead The experiments require no soldering Experimenting with the PIC16F877 The second PIC book starts with the simplest of experiments to give us a basic understanding of the PIC16F877 family Then we look at the 16 bit timer efficient storage and display of text messages simple frequency counter use a keypad for numbers letters and security codes and examine the 10 bit A D converter The 2nd edition has two new chapters The PIC16F627 is introduced as a low cost PIC16F84 We use the PIC16F627 as a step up switching regulator and to control the speed of a DC motor with maximum torque still available Then we study how to use a PIC to switch mains power using an optoisolated triac driving a high current triac 138 The Street Little Clacton Clacton on sea Brunning Software Essex CO16 9LS Tel 01255 862308 Everyday Practical Electronics May 2002 355 Constructional Project WASHING READY INDICATOR TERRY DE VAUX BALBIRNIE Has the washing machine finished Avoid those washday blues UR OLD washing machine gave long O faithful service Unfortunately when it did eventually fail it was not possible to repair it economically DREAM MA
3. Card NO o 4 5 2 cee 2 3 a eet 2 50a ete bdr Ge Ooh buns hee pion ce dy doe Sarees Oi i it pla i ct i i eS dil i il tS a The Virtual PIC Interested i in 1 programming PIC microcontrollers Learn with PiCtutor This highly acclaimed CD ROM by John Becker together with the PlCtutor experimental and development board will teach you how to use PIC microcontrollers with special emphasis on the PIC 16x84 devices The board will also act as a development test bed and programmer for future projects as your programming skills develop This interactive presentation uses the specially developed Virtual PIC Simulator to show exactly what is happening as you run or step through a program In this way the CD provides the easiest and best ever introduction to the subject Nearly 40 Tutorials cover virtually every aspect of PIC programming in an easy to follow logical sequence HARDWARE Whilst the CD ROM can be used on its own the physical demonstration provided by the PICtutor Development Kit plus the ability to program and test your own PIC16x84s really reinforces the lessons learned The hardware will also be an invaluable development and programming tool for future work Two levels of PICtutor hardware are available Standard and Deluxe The Standard unit comes with a battery holder a reduced number of switches and no displays This version will allow users to complete 25 of the 39 Tutorials The Deluxe Development Kit is supplied
4. Thanks Barry nice to hear from you again And yes July 01 Incidentally folks Barry also drew our atten tion to a web site devoted to the history of BBC equipment and those who helped run it of whom Barry was one The site is well worth a visit and is at www roger beckwith btinternet co uk bh menu htm INTERRUPTING THE Z BIT Dear EPE The article by Malcolm Wiles on Programming PIC Interrupts Mar Apr 02 was of interest and I was surprised to see the query raised over the use of the instruction MOVE Status W i e what will be the bit in W corresponding to the Z bit of the Status regis ter Will it be the value in the Status register at the start of the instruction or the value at the end of the instruction A simple consideration of the hardware of registers will indicate what happens The flip flops of W will have the Status regis ter routed to it and it will be clocked into the flip flops at the same time that the output of the Zero detection logic is being clocked into the Status register Hence the old value of the Status regis ter is clocked into W and the zero condition of the old value of the Status register is reflected in the new Z bit which is clocked into the Status register Ken Naylor via email Malcolm replies As a software engineer I would never presume to guess or assume how Microchip have imple mented their hardware Just because there is a simple or obvious maybe even textbook way o
5. tion is provided by fully louvered back door and double skinned top section with top and side louvres The top panel may be removed for fitting of integral fans to the sub plate etc Other features include fitted castors and floor levelers prepunched utility panel at lower rear for cable connector access etc Supplied in excellent slightly used condition with keys Colour Royal blue some grey available CALL Can be supplied in many other configurations 33U 42U 47U Order as BC44 Order as DT20 Order as RV36 External dimensions External dimensions External dimensions mm 1625H x 635D x mm 2019H x 635D x mm 2019H x 635D x 603 W 64 H x 25 603 W 79 5 H x 25 603 W 88 H x 25 D x 23 W D x 23 W D x 23 W Only Only Only Call for shipping quotation Undoubtedly a miracle of modern technology amp IG our special buying power A quality product fea AV p turing a fully cased COLOUR CCD camera at a amp give away price Unit features full autolight sensing for R use in low light amp high light applications A 10 mm fixed focus wide angle lens gives excellent focus and resolution from close up to long range The composite video output will connect to any composite monitor or TV via SCART socket and most video recorders Unit runs from 12V DC so ideal for security amp portable applica tions where mains power not available Overall dimensions 66 mm wide x 117 deep x 43 high Supplied BRAND NEW amp
6. 00 268 5 07 g Meter 269 4 36 EPE SOFTWARE EPE Moodloop AUG 00 271 5 47 Quiz Game Indicator 272 4 52 Software programs for EPE projects marked with a single asterisk are available on Handy Amp 273 4 52 3 5 inch PC compatible disks or free from our Internet site The following disks are Active Ferrite L T SEPT 00 274 74 67 available PIC Tutorial Mar May 98 PIC Toolkit Mk2 V2 4d May Jun 99 EPE Disk 1 Apr 95 Dec 98 EPE Disk 2 1999 EPE Disk 3 2000 EPE Disk 4 2001 x Remote Control IR Decoder Software only Z EPE Disk 5 Jan 2002 issue to current cover date EPE Teach In 2000 EPE PIC Dual Channel Virtual Scope OCT 00 Spectrum EPE Interface Disk 1 October 00 issue to current cover date amp PIC Handclap Switch NOV 00 270 3 96 Toolkit TK3 software Nov 01 is on CD ROM The 3 5 inch disks are 3 00 each PIC Pulsometer Software only UK the CD ROM is 6 95 UK Add 50p each for overseas surface mail and 1 each for airmail All are available from the EPE PCB Service All files can be down T dg Star loaded free from our Internet FTP site ftp ftp epemag wimborne co uk Festive Fader Motorists Buzz Box Doster est EPE PRINTED CIRCUIT BOARD SERVICE Monitor Unit Static Field Detector Multi project PCB Order Code Project Quantity Price Two Way Intercom JAN 01 UFO Detector and Event Recorder Magnetic Anomaly Detector Event Recorder Audio Alarm Us
7. Passive Components resistors capacitors inductors transformers Semiconductors diodes transistors op amps logic gates Passive Circuits Active Circuits The Parts Gallery will help students to recognise common electronic components and their corresponding symbols in circuit diagrams Selections include Components Components Quiz Symbols Symbols Quiz Circuit Technology Included in the Institutional Versions are multiple choice questions exam style questions fault finding virtual laboratories and investigations worksheets Circuit simulation screen Hobbyist Student 000 c eee eee ee 45 inc VAT Institutional Schools HE FE Industry 000 000005 99 plus VAT Institutional 10 user Network Licence 005 199 plus VAT Institutional Site Licence 00c eee eee eee 499 plus VAT UK and EU customers add VAT at 17 5 to plus VAT prices details Also contains a FREE 30 day PiCtutor CD ROM HARDWARE evaluation of Paint Shop Pro 6 Hobbyist Student 000000es 45 inc VAT Standard Development Kit 47 inc VAT Paint Shop Pro image editing tips Institutional Schools HE FE Industry 99 plus VAT Deluxe Development Kit 99 plus VAT and on line help included Institutional 10 user Network Licence 199 plus VAT Deluxe Export Version 96 plus VAT Price 19 95 inc VAT UK and EU customers add VAT at 17 5 to plus VAT prices ELECTRO
8. SAVE s RCB UNITS Inline IEC lead with fitted RC break er Installed in seconds Fit to any computer monitor office equip ment and make it safe Pack of 10 just 9 98 Ref LOT5B INFRA RED REMOTE CONTROL WATCHES 16 99 VIBRATING WATCHES vibrate when your phone rings 16 99 PULSE WATCHES display your pulse 16 99 www quemex co uk MINIATURE TOGGLE SWITCHES These top quality Japanese panel mounting toggle switches measure 35mm x 13mm x 12mm are 2 pole changeover and will switch 1A at 250V a c or 3A at 125V a c Complete with mounting washers and nuts Supplied as a box of 100 switches for 29 95 Ref SWT35 or a bag of 15 for 4 99 Ref SWT34 STEPPER MOTORS Brand new stepper motors 4mm fixing holes with 47 14mm fixing centres 20mm shaft 6 35mm diameter 5V phase 0 7A phase 1 8 deg step 200 step Body 56mm x 36mm 14 99 each Ref STEP6 pack of 4 for 49 95 BASIC GUIDE TO LOCKPICKING New publication gives you an insight 6 Ref LPK NEW HIGH POWER MINI BUG With a range of up to 800 metres and 3 days use from a PP3 this is our top selling bug Less than 1in square and a 10m voice pick up range 28 Ref LOT102 IR LAMP KIT Suitable for CCTV cameras enables the camera to be used in total darkness 6 Ref EF138 INFRA RED POWERBEAM Handheld battery powered lamp 4in reflector gives out powerful pure infra red light Perfect for CCTV use nightsights etc 29 Ref PB1 YOUR HOME COULD BE SELF SU
9. VARTRAF Where k is a physical constant known as Boltzmann s Constant 1 38 x 10 22JK Joules per Kelvin T is the temperature in Kelvin K R is the resistance in ohms Q Af is the bandwidth of interest in Hertz Hz i e the range of frequencies over which you are measuring the noise Af is pronounced delta f the delta symbol means change in and so Af repre sents a range of frequencies The fact that a bandwidth has to be speci fied in order to get a noise voltage means that noise figures are often expressed in volts per bandwidth unit form rather than simply as voltages have a look on data sheets for i c s such as op amps and you will see noise figures expressed this way This value is known as noise density If we divide both sides of the first equa tion by the square root of the bandwidth VAP we get VN rms W4KTR VAf The value V4kTR has units volts per root Hertz often written as V Hz 2 or V VHz So for example the noise from a 100kQ resistor at 20 C 293K is V4 x 1 38 x 10 23 x 293 x 100 x 10 40nV Hz 2 If we were interested in a bandwidth of say 20kHz the thermal noise voltage from this resistor would be 40nV x V20 x 10 5 7uV Statistical analysis of the properties of thermal noise shows that the instanta neous peak noise voltage will be less than five times the r m s average value for 99 per cent of the time The equation for thermal noise indicates
10. and IC1 does not need to be repeated if additional banks of drivers are added The software allows two additional banks of eight digits a total of 24 digits to be controlled without modification to the program Readers who are familiar with PIC and QB programming could modify the software to cope with multiplexing up to 64 digits if an additional 74HC237 mul tiplexer is used see later Segment selection is provided by a 3 bit code fed to multiplexers IC4 and ICS These in turn control segment sink drivers IC6 and IC7 respectively Only seven out puts of these multiplexers are used The two multiplexers are under chip select CS control by separate CS1 lines pins 6 so that segment On or Off control is achieved not only in respect of the 3 bit code but also in terms of current sinking pulse duration more later SELECT BANK 1 SELECT BANK 2 SELECT BANK 3 DIGITS SELECT 12V POWER 3 BIT CODE gt DIGIT 8 BIT CODE CONTROL SBT CODE gt SELECT 7 SEGMENT 3 BIT CODE SEGMENT 7 BIT CODE DIGIT 2 BIT CODE SELECT SEGMENT ON OFF Fig 5 Multiplexed control logic Everyday Practical Electronics May 2002 ALL BANKS DIGIT 1 12V DIGIT 2 12V SELECT RBO AO Y2 DIGIT 3 12V At 74HC237 1 AO Y2 DIGIT RB1 DIGIT 4 12V A2 FROM IC8 RB2 4 5 12 13 LE CS2 ALL BANKS DIGIT 5 12V DIGIT 6 12V DIGIT 7 12V BANK SELECT DIGIT 8 12V RAO FOR BANK 1 RA1 FOR BANK 2 RA2 FOR BANK 3 E 4 5 12 13 i
11. but B cannot it would just look like an 8 Also note that any letters having diago nals cannot be represented such as K M N Z nor can T It is worth experimenting to see what characters can be represented and what compromises you might have to 330 FROM SEGMENT CONTROL I C s ON FROM IC6 OFF FROM IC7 IGNORE UNMARKED CONNECTION POINTS TO OTHER DIGITS 12V FROM SELECTED POWER CONTROL I C Fig 13 Wiring details for a single digit Interwiring between the two digits used during development make You may recall that the author s Teach In 2000 series demonstration soft ware illustrated the principle of 7 segment control Having established the segment code required the PIC then has to send the cor responding data to the segments individu ally From within a loop the PIC reads each data bit position to see whether a seg ment should be On or Off At each position it uses another look up table TABLE2 see Listing 2 for the code needed to send to multiplexers IC4 and IC5 in order to control that bit The code also takes into account that the p c b tracks are connected to the three con trol pins in the opposite order than might normally be expected this was done for p c b design simplicity Only bits 6 to 4 are of importance in this table LISTING 2 TABLE2 addwf PCL F retlw 01000000 retlw 00100000 retlw 01100000 retlw 00010000 retlw 01010000 retlw 00110000 retl
12. cies below 150Hz or so Feeding low fre quencies to speakers of this kind only overloads them causing distortion and loss of clarity Indeed if the amplifier is being used primarily for speech clarity can be much improved by rolling off the frequency response below 300Hz and an even lower value of coupling capacitor say 100uF or even 47uF would be of benefit Readers seeking quality music reproduction at low power via a speaker of reasonable size should increase the coupling capacitor to say 1000UF This relationship between coupling capacitors and frequency response will be considered more fully in the next article DEVICE PROTECTION The integrated circuits covered here are electrically robust but they are by no means indestructible The TDA7052 LM380 and the TDA2003 incorporate protection against overload and output short ciruits the other devices do not However Ree even with this pro wo tection excessive sup ply voltage will result in gp immediate failure and shorting the output when the amplifier is being driven hard and or when the sup ply voltage is close to the operational max imum will quickly ruin the device SUPPLY VOLTAGE Suitable mains power supplies will be covered in a later article but it should be mentioned now that off load d c output voltages rise to 1 4 times the a c voltage delivered by transformer secondaries When using unregulated mains power sup plies care
13. etc so we need a 3 bit Gray coded disc The circuit diagram is shown in Fig 7 26 The outputs of the sensors are amplified by transistors TR1 to TR3 and input to a 3 to 8 line decoder IC1 The decoder takes a 3 bit binary input and sets the corresponding output low For example if the input is binary 000 output YO goes low an input of binary 110 causes output Y6 to go low Table 7 5 Relationship between Outputs and Compass Points for Lab 7 3 Output L E D Compass point YO D1 South East Y1 D2 West Y2 D3 East Y3 D4 North West Y4 D5 South Y5 D6 South West Y6 D7 North East Y7 D8 North The decoder has three enables two active low and one active high In this cir cuit they are set to permanently enable the device Each output is connected to an l e d to indicate whether or not it is low Since the disc is Gray coded the outputs YO Y7 do not correspond to successive points on the compass as they would if the disc were binary coded Use Table 7 5 to connect the l e d s in the correct order Photocopy the disc in Fig 7 8 Mount the sensors in a similar manner to Lab 7 1 Everyday Practical Electronics May 2002 Example of a reflective sensor as used in the wind vane RER T ikae ial Breadboard assembly mr a sides reui in T 7 26 Individual l e d s may z used in place of the bargraph display and discrete resistors in place of the resistor module WEIGHT TO COUNTER BALANCE VANE OLD FELT PEN TUBE
14. fully guaranteed with user data 100 s of applica tions including Security Home Video Web TV Web Cams etc etc OrderasLK33 ONLY 79 00 or 2 for 149 00 B NT4 WorkStation complete with service pack 3 and licence OEM packaged ONLY 89 00 B ENCARTA 95 CDROM Not the latest but at this price 7 95 DOS 5 0 on 3 disks with concise books c w QBasic 14 95 Windows for Workgroups 3 11 Dos 6 22 on 3 5 disks 55 00 Windows 95 CDROM Only No Licence 19 95 Wordperfect 6 for DOS supplied on 3 disks with manual 24 95 shipping charges for software is code B Visible red 670nm laser diode assembly Unit runs from 5 V DC at approx 50 mA Orginally made for continuous use in industrial bar code scanners the laser is mounted in a removable solid aluminium block which functions as a heatsink and rigid optical mount Dims of block are 50 w x 50d x 15h mm Integral features include over tem perature shutdown current control laser OK ouput and gated TTL ON OFF Many uses for experimental optics comms amp lightshows etc Supplied complete with data sheet Order as TD91 ONLY 24 95 a Virtually every type of power supply you can imagine Over 10 000 Power Supplies Ex Stock Call or see our web site RELAYS 200 000 FROM STOCK Save s by choosing your next relay from our Massive Stocks covering types such as Military Octal Cradle Hermetically Sealed Continental Contactors Time Delay Reed Mercury Wett
15. gain could be set between 40 and 230 High frequency response is determined by capacitor C6 The response at the 3dB points for different capacitor values is also listed in the table If desired the value of C6 can be increased to reduce the upper frequency response even more In this application the speaker LS1 is have made provi circuit the signal connected to the positive supply rail as this reduces the component count a capacitor and resistor are saved CIRCUIT BOARD The printed circuit board component layout wiring details and full size copper foil master pattern are shown in Fig 6 This board is available from the EPE PCB Service code 345 TBA820M Finished LM380N circuit board A twin heatsink may be required for this chip A heatsink should be fitted if the device is to be operated other than intermittently at output levels in excess of 1W Without a heatsink the suggested maximum supply voltages are with a 4 ohm speaker with an 8 ohm speaker Frequency response 12V 15V up to 100kHz 345 O 9V TO 18V SUPPLY VOLTAGE V NOT CONNECTED OUTPUT GROUND OV AND HEATSINK OUTPUT GROUND OV AND HEATSINK INPUT NOT CONNECTED INPUT GROUND OV SIGNAL OUT TOP VIEW OF LM380N Fig 7 Circuit diagram for the LM380N Amplifier COMPONENTS LM380N AMPLIFIER Resistors R1 297 0 25W 5 carbon film Potentiometers VR1 10k rot
16. ity reception 1000m range 6 12V DC operation Size jm 70x15mm 3032KT 9 95 ea AS3032 18 95 MMTX MICRO MINIATURE 9V TRANSMITTER The ultimate bug for its size performance and price Just 15x25mm 500m range 9V Good stability 6 18V operation 3051KT 8 95 AS3051 14 95 VTX VOICE ACTIVATED TRANSMITTER Operates only when sounds detected Low standby current Variable trigger sen sitivity 500m range Peaking circuit supplied for maximum RF out put On off switch 6V operation Only 63x38mm 3028KT 12 95 AS3028 21 95 HARD WIRED BUG TWO STATION INTERCOM Each station has its own amplifier speaker and mic Can be set up as either a hard wired bug or two station intercom 10m x 2 core cable sup plied 9V operation 3021KT 15 95 kit form only TRVS TAPE RECORDER VOX SWITCH Used to automati cally operate a tape recorder not supplied via its REMOTE sock et when sounds are detected All conversations recorded Adjustable sensitivity amp turn off delay 115x19mm 3013KT 9 95 AS3013 21 95 en 700W power PCB 48mm x 65mm Box provided 6074KT 17 95 3 INPUT MONO MIXER Independent level con trol for each input and separate bass treble controls Input sensitivity 240mV 18V DC PCB 60mm x 185mm 1052KT 16 95 NEGATIVE POSITIVE ION GENERATOR Standard Cockcroft Walton multiplier circuit Mains voltage experience required 3057KT 10 95 LED DICE Classic intro t
17. s drawings reviewed in EPE March 1998 issue The program could create automatically from a circuit diagram a layout either for stripboard or a plug in solderless breadboard I occasionally get emails asking me what happened to Stripboard Magic Well just as the program was starting to gain acceptance it is believed that Ambyr sold the exclusive distributorship to a mail order company The program and its web site sank without trace and Ambyr Ltd was dissolved in December 1999 according to Companies House Online at www companieshouse gov uk Lochmaster 2 0 However I am very grateful to reader Branko Zupan in Slovenija who has brought to my attention a German stripboard design package called Lochmaster This is produced by Abacom and an English version is downloadable from www abacom online de The demo allows ten elements to be positioned and print and save functions have been disabled It appears to be a very good tool for helping to design layouts by hand although it does not automate the total design process as Stripboard Magic did The component library is comprehensive and incorporates all the usual discrete and integrated devices semiconductors plus a good range of hardware including fasteners pin headers and d i 1 sock ets New components can also be added to the library Stripboards are designed by placing components on the board rotating and linking as necessary and making breaks in the copper track using the Split com
18. seventy different Input Processor and Output modules are illustrated and fully described together with detailed information on construction fault finding and components including circuit symbols pinouts power supplies decoupling etc Single User 19 95 inc VAT Multiple User 34 plus VAT UK and EU customers add VAT at 17 5 to plus VAT prices Minimum system requirements for these CD ROMs Pentium PC CD ROM drive 32MB RAM 10MB hard disk space Windows 95 98 NT 2000 ME XP mouse sound card web browser Note The CD ROM is not included in the Development Kit prices i ORDERING ALL PRICES INCLUDE UK POSTAGE Note The software on each version is the same unless stated otherwise only the licence for use varies Student Single User Standard Version price includes postage to most countries in the world EU residents outside the UK add 5 for airmail postage per order rii L Aah PITENEE Card expiry date ee50b The leading magazine for vintage radio enthusiasts e VINTAGE COMS FAIR A gt hias S N E C BIRMINGHAM Radio oF SUNDAY 5 MAY 02 5 re 10 30 a m Rejuvenation of a Codar ATS Firing Up a C Transmitter Radar Al Mea Night Fighter WHETHER your interest is in domestic radio and TV or in amateur radio in military aeronautical or marine communications in radar and radio navigation in instruments in broadcasting in audio and recording or in professional
19. tem 3121KT 24 95 3V 1 5V TO 9V BATTERY CONVERTER Replace expensive 9V batteries with economic 1 5V batter ies IC based circuit steps up 1 or 2 AA batteries to give 9V 18mA 3035KT 5 95 STABILISED POWER SUPPLY 3 30V 2 5A Ideal for hobbyist amp professional laboratory Very reliable amp versatile design at an extremely reason able price Short circuit protection Variable DC voltages 3 30V Rated output 2 5 Amps Large heatsink supplied You just supply a 24VAC 3A transformer PCB 55x112mm Mains operation 1007KT 16 95 ters can be received on an ordinary VHF FM radio between 88 108MHz Available in Kit Form KT or Assembled amp Tested AS TELEPHONE SURVEILLANCE MTTX MINIATURE TELEPHONE TRANSMITTER Attaches anywhere to phone line Transmits only when phone is used Tune in your radio and hear both parties 300m range Uses line as aerial amp power source 20x45mm 3016KT 8 95 AS3016 14 95 TRI TELEPHONE RECORDING INTERFACE Automatically record all conversations Connects between phone line amp tape recorder not supplied Operates recorders with 1 5 12V battery systems Powered from line 50x33mm 3033KT 9 95 AS3033 18 95 TPA TELEPHONE PICK UP AMPLIFIER WIRELESS PHONE BUG Place pick up coil on the phone line or near phone earpiece and hear both sides of the conversation 3055KT 11 95 AS3055 20 95 HIGH POWER TRANSMITTERS 1 WATT FM TRANSMITTER Easy to construct Delivers a
20. that we can reduce noise voltage by reduc ing resistance source or internal resistance in the case of a sensor or by reducing bandwidth Reducing source resistance may not be possible as it will often be fixed for a particular sensor However effective reduction in bandwidth can be achieved by making many measurements and averaging or measurement over a longer period of time Why does making multiple measure ments reduce effective Af If we make a measurement over a certain period of time those random variations which occur many times during this period will be averaged out However variations much longer than our period of making measurements will not be seen by our measurement process Thus we have effectively removed some of the noise in the high frequency end of Af reducing its range and hence reducing the noise This approach is useful but of course we pay for it by reduction in the speed with which we make our measurement We also cannot extend our measurement period for longer than the time for which the quantity being measured will have a constant value and as we increase measurement time other errors such as drift become more significant Everyday Practical Electronics May 2002 SHOT NOISE When current flows through a resistance it will generate additional white noise above the thermal noise due to the quantum nature of electric current at the atomic level Electric current is the flow of discrete
21. 4 Comparator with hysteresis 369 change of the comparator s output voltage as it switches is known as its slew rate Any op amp may be used as a compara tor but the best performance is obtained by using devices that have been specifically designed as comparators COMPARATOR HYSTERESIS A comparator with a single threshold value may switch states many times as a noisy slowly changing input crosses the threshold This is often undesirable for example if the number of threshold cross ings is to be counted The problem may be overcome by using two thresholds e g Vry and Vay The difference between V and V is called the hysteresis When the input increases past Vy the comparator switch es but it does not switch if the input decreases past Vy The input must decrease past a lower threshold Vg before the comparator switches again This is illustrated in Fig 7 2 If the input noise level is known the hys teresis can be set slightly larger than this The comparator will then not switch as a result of the noise Fig 7 3 and Fig 7 4 show the result of applying the same noisy signal to a simple comparator and one with hysteresis REGENERATIVE COMPARATORS Comparators with hysteresis are also known as regenerative comparators and Schmitt triggers A comparator with hys teresis can be made using a single thresh old comparator by setting the threshold depending on the comparator s present out put state The c
22. 99 00 5 HP C3010 2 Gbyte SCSI differential RFE tested 195 00 8 NEC D2246 85 Mb SMD interface New 99 00 8 FUJITSU M2322K 160Mb SMD I F RFE tested 195 00 8 FUJITSU M2392K 2 Gb SMD I F RFE tested 345 00 Many other floppy amp H drives IDE SCSI ESDI etc from stock see website for full stock list Shipping on all drives is code C TEST EQUIPMENT amp SPECIAL INTEREST ITEMS MITSUBISHI FA3445ETKL 14 Ind spec SVGA monitors 245 FARNELL 0 60V DC 50 Amps bench Power Supplies 995 FARNELL AP3080 0 30V DC 80 Amps bench Suppy 1850 KINGSHILL CZ403 1 0 50V DC 200 Amps NEW 3950 1kW to 400 kW 400 Hz 3 phase power sources ex stock POA IBM 8230 Type 1 Token ring base unit driver 760 Wayne Kerr RA200 Audio frequency response analyser 2500 INFODEC 1U 24 port RJ45 network patchpanels TH93 49 3COM 16670 12 Port Ethernet hub RJ45 connectors LD97 69 3COM 16671 24 Port Ethernet hub RJ45 connectors 89 3COM 16700 8 Port Ethernet hub RJ45 connectors NEW 39 IBM 53F5501 Token Ring ICS 20 port lobe modules POA IBM MAU Token ring distribution panel 8228 23 5050N 45 AIM 501 Low distortion Oscillator 9Hz to 330Khz IEEE I O 550 ALLGON 8360 11805 1880 MHz hybrid power combiners 250 Trend DSA 274 Data Analyser with G703 2M 64 i o POA Marconi 6310 Programmable 2 to 22 GHz sweep generator 4500 Marconi 2022C 10KHz 1GHz RF signal generator 1550 HP1650B Logic Analyser 3750 HP3781A Patt
23. AC mains powered Only 79 00 D Tiny shoebox sized industrial 40 Mhz 386 PC system measuring only mm 266 w X 88 h X 272 d Ideal for dedicated control appli cations running DOS Linux or even Windows Steel case con tains 85 to 265 V AC 50 60 hz 70 Watt PSU a 3 slot ISA passive backplane and a Rocky 318 PC104 standard single board com puter with 8 MByte NON VOLATILE solid state Disk On Chip RAMDISK System comprises Rocky 318 PC104 SBC ISA card with 40MHz ALi 386SX CPU 72 pin SIMM slot with 16 Mbyte SIMM AMI BIOS battery backed up real time clock 2 x 9 pin D 16550 serial ports EPP ECP printer port mini DIN keyboard con nector floppy port IDE port for hard drives up to 528 MByte capacity watchdog timer and PC 104 bus socket The 8 MByte solid state disk on a chip has its own BIOS and can be fdisked formatted amp booted Supplied BRAND NEW fully tested and guar anteed For full data see featured item on website Order as QG36 100 s of applications inc firewall routers robotics etc Only 99 00 0 Unless marked NEW items in this section are pre owned HP6030A 0 200V DC 17 Amps bench power supply 1950 Intel SBC 486 125C08 Enhanced Multibus MSA New 1150 Nikon HFX 11 Ephiphot exposure control unit 1450 PHILIPS PM5518 pro TV signal generator 1250 Motorola VME Bus Boards amp Components List SAE CALL POA Trio 0 18 vdc linear metered 30 amp bench PSU New 550 Fujitsu M3041R 600 LPM
24. Build the circuit on breadboard but with the sensor mounted on a small bit of strip board and set the oscillator period to about one second using VR1 Use the Picoscope to measure the period Monitor the voltage at point A in Fig 7 22 and rotate the disc The output should be similar to that in Fig 7 24 If it is not then try moving the sensor closer to the disc Fig 7 24 Example of output pulses at point A in Fig 7 22 Once you get a good series of pulses at point A connect a voltmeter or the Picoscope to the output of the circuit You should get a voltage which changes approx imately once per second and which is pro portional to the speed of rotation Fig 7 25 Fig 7 25 Output of anemometer show ing wind speed variation 376 IC1 74HC138 DIRECTIONS Fig 7 26 Circuit diagram for the wind direction sensor shows a typical output captured using the Picoscope note that the noise is due to the limited resolution of the Picoscope ADC 40 and not the DAC If the oscillator is set to 1 016s then 0 1V at the DAC s output should be roughly equal to Ims i e 3 0V equals 30ms Accurate calibration is not easy as dis cussed earlier in the theory section Lab 7 3 Wind Direction Meter Measuring wind direction can be done using a binary or Gray coded disc and mul tiple sensors In this Lab we show you how to build an instrument to indicate eight points on the compass north north east east
25. Cats THE latest Jackson Brothers catalogue of variable capacitors and drives has been received from Mainline Electronics These 30 pages will be a highly useful source of information when looking for that vital radio component Prices are quoted as a separate 4 page supplement Also received is Mainline s Flyer a 32 page catalogue of over 850 new products on offer They say they have bought over 250 pallets of new surplus stock and have many very unusual items plus the usual freebies The components are varied too categorise here so get a copy of the two cats Contact Mainline Electronics Dept EPE Unit 1A Cutters Close Coventry Road Narborough Leicester LE19 2FZ Tel 0116 286 5373 Fax 0116 286 7797 Email surplus mainlinegroup co uk Smaller DVD Cassettes By Barry Fox SONY thinks the world needs a new video format At the IFA electronics show in Berlin Sony unveiled MicroMV a tape cassette 70 per cent smaller than existing Mini DV digital video cassettes The tape runs for an hour and the cassette has 64KB of onboard solid state memory that auto matically indexes every shot and tells what is on a tape by instantly displaying still images taken from the start of the shots 323 Constructional Project PIC BIG DIGIT DISPLAY JOHN BECKER Microcontroling giant segment displays ECENTLY Dave Fisher of Display Electronics told EPE that he had acquired several thousand electro mechanic
26. In 2002 Making Sense of the Real World our multi part series created to help construc tors adapt and use many types of environ mental sensors within their own projects We hope that there is something in this Teach In 2002 series to suit everyone as we said right at the beginning one often gets the impression that the world has gone completely digital in nature with tele phones television music photography and radio all following this trend None of this allows us to escape the fact that the real world is actually ana logue a world in which many electron ics applications must obtain information from their environment and condition it correctly before it can be handed over for digital processing Our series out lines many fundamental principles of operational amplifiers instrumentation amplifiers low noise techniques includ ing a lot of material not covered before in EPE SEE TEXT TR1 2N3906 In Isolation How to optically isolate an analogue sig nal is something I put to Dr David Chesmore one of the Teach In 2002 co writers and closely involved with the Biomedical Engineering Research Group at the University of York Dave has pro duced most of the environmental monitor ing material of our series and he suggest ed that most opto isolators can be operated linearly since they contain 1 e d s and usu ally phototransistors R6 R5 470 68k HCNR200 Fig 1 Circuit for a high speed lo
27. O4 p agea Measurements Radio Computers Valves and Manufacturers Data etc F undamental pr inciples PRACTICAL SKILLS Learn how to identify Electronic Components Avoid Static lt Troubleshooting techniques Hazards Carry Out Soldering and Wiring Remove and Replace Components o Ser vicMY techniques TEST EQUIPMENT How to Choose and Use Test Equipment Assemble a Toolkit Set pi ite and using test guipment Up a Workshop and Get the Most from Your Multimeter and Oscilloscope etc SERVICING TECHNIQUES Th lar Suppl ts include vital guideli how t eee The regular Supplements include vital guidelines on how to TA Service Audio Amplifiers Radio Receivers TV Receivers Cassette Recorders Video a ae runes Recorders Personal Computers etc j Clear and simple lay out TECHNICAL NOTES Commencing with the IBM PC this section and the regular e UA Sary PrOGAUNONS Supplements deal with a very wide range of specific types of equipment radios TVs e Professionally written cassette recorders amplifiers video recorders etc Regular Supplements REFERENCE DATA Detailing vital parameters for Diodes Small Signal Transistors e Sturdy gold blocked ring binder Power Transistors Thyristors Triacs and Field Effect Transistors Supplements include Operational Amplifiers Logic Circuits Optoelectronic Devices etc ELECTRONICS SERVICE MANUAL ESM Printed version only Basic Work Contains around 900 pages of information Edited by Mike
28. Oct 2000 is now available on CD ROM Plus the Teach In 2000 interac tive software covering all aspects of the series and Alan Winstanley s Basic Soldering Guide including illustrations and Desoldering Teach In 2000 covers all the basic principles of elec tronics from Ohm s Law to Displays including Op Amps Logic Gates etc Each part has its own section on the interactive software where you can also change compo nent values in the various on screen demonstration cir cuits The series gives a hands on approach to electronics with numerous breadboard circuits to try out plus a simple computer interface which allows a PC to be used as a basic oscilloscope ONLY 12 45 including VAT and p amp p PROJECT CONSTRUCTION PRACTICAL REMOTE CONTROL PROJECTS Owen Bishop Provides a wealth of circuits and circuit modules for use in remote control systems of all kinds ultrasonic infra red optical fibre cable and radio There are instructions for building fourteen novel and practical remote control projects But this is not all as each of these projects provides a model for building dozens of other related cir cuits by simply modifying parts of the design slightly to suit your own requirements This book tells you how Also included are techniques for connecting a PC toa remote control system the use of a microcontroller in remote control as exemplified by the BASIC Stamp and the application of ready made type approved
29. Other AVOs from GOODWILL GVT427 Dual Ch AC Millivoltmeter 10mV 300V in 12 ranges Freq 10Hz 1MHz 100 125 SOLARTRON 7150 DMM 6 2 digit Tru RMS IEEE SOLARTRON 7150 Plus HIGH QUALITY RACAL COUNTERS 9904 Universal Timer Counter 50MHz 9916 Counter 10Hz 520MHz 9918 Counter 10Hz 560MHz 9 digit WAYNE KERR B424 Component Bridge RACAL AIM 9343M LCR Databridge Digital Automeasurement of R C L Q D HUNTRON TRACKER Model 1000 FLUKE 8050A 4 5 Digit 2A True RMS FLUKE 8010A 3 5 Digit 10A FLUKE 8012A 3 5 Digit 2A SOLARTRON 7045 Bench Multimeter ONLY 4 5 Digit Bright L E D with leads Portable Appliance Tester f e180 Megger Pat 2 Only H P 6012B DC PSU 0 60V 0 50A 1000W 1000 FARNELL AP60 50 1KW Autoranging FARNELL H60 50 0 60V 0 50A FARNELL H60 25 0 60V 0 25A Power Supply HPS3010 0 30V 0 10A FARNELL L30 2 0 30V 0 2A FARNELL L30 1 0 30V 0 1A Many other Power Supplies available Isolating Transformer 240V In Out 500VA 40 STEWART of READING z 110 WYKEHAM ROAD READING BERKS RG6 1PL ms Telephone 0118 9268041 Fax 0118 9351696 s VISA il www stewart of reading co uk Callers welcome 9am 5 30pm Monday to Friday other times by arrangement FRUSTRATED Looking for ICs TRANSISTORS A phone call to us could get a result We offer an extensive range and with a world wide database at our fingertips we are able to source even more We specialise in devices with the fol
30. SS SS Ee Se ee ee eee Our June 2002 issue will be published on Thursday 9 May 2002 See page 307 for details Everyday Practical Electronics May 2002 Projects and Circuits FREEZER ALARM by Humphrey Berridge 316 How to prevent your food from defrosting unexpectedly PIC BIG DIGIT DISPLAY by John Becker 325 Control the giant ex British Rail platform clock 7 segment digits that are now available on the surplus market INGENUITY UNLIMITED hosted by Alan Winstanley 338 Battery Discharger Emergency Light SIMPLE AUDIO CIRCUITS 1 Power Amplifiers by Raymond Haigh 340 A compendium of useful audio amplifier circuits for the experimenting constructor WASHING READY INDICATOR by Terry de Vaux Balbirnie 356 Has the washing machine finished Avoid those washday blues Series and Features NEW TECHNOLOGY UPDATE by lan Poole 320 Dye molecules improve solar cell efficiency PRACTICALLY SPEAKING by Robert Penfold 335 A general look at using enclosures with your projects NET WORK THE INTERNET PAGE surfed by Alan Winstanley 360 Stripboard designing software CIRCUIT SURGERY by Alan Winstanley and lan Bell 362 Linear opto coupling Dog and Cat Scarer circuit details TEACH IN 2002 7 Comparators and digital optical sensing 368 plus more on Noise with experiments by lan Bell and Dave Chesmore Regulars and Services ELECTRONICS MANUALS 310 Essential reference works for hobbyists students and service engineers EDITORIAL 315 NEW
31. TEKTRONIX 2465B 4 ch 400MHz delay cursors etc 1500 TEKTRONIX 2465 4 ch 300MHz delay cursors etc 900 TEKTRONIX 2445 A B 4 ch 150MHz delay cursors etc 500 900 TEKTRONIX 468 Dig Storage dual trace 100MHz delay 450 TEKTRONIX 466 Analogue Storage dual trace 100MHz 250 TEKTRONIX 485 dual trace 350MHz delay sweep TEKTRONIX 475 dual trace 200MHz delay sweep TEKTRONIX 465B dual trace 100MHz delay sweep PHILIPS PM3217 dual trace 50MHz delay GOULD 0S1100 dual trace 30MHz delay HAMEG HM303 dual trace 30MHz component tester HAMEG HM203 7 dual trace 20MHz component tester FARNELL DTV20 dual trace 20MHz component tester 125 Many other Oscilloscopes available MARCONI 2022E Synth AM FM Sig Gen 10kHz 1 01GH2z l c d display etc H P 8657A Synth sig gen 100kHz 1040MHz H P 8656B Synth sig gen 100kHz 990MHz H P 8656A Synth sig gen 100kHz 990MHz R amp S APN62 Synth 1Hz 260kHz sig gen balanced unbalanced output c d display PHILIPS PM5328 sig gen 100kHz 180MHz with 200MFz freq counter IEEE RACAL 9081 Synth AM FM sig g en 5kHz 1024MHz H P 3325A Synth function gen 21MHz MARCONI 6500 Amplitude Analyser H P 4192A Impedance Analyser H P 4275A LCR Meter 10kHz 10MHz H P 8903A Distortion Analyser WAYNE KERR 3245 Inductance Analyser H P 8112A Pulse Generator 50MHz MARCONI 2440 Frequency Counter 20GHz H P 5350B Frequency Counter 20GHz H P 5342A 10Hz 18GHz
32. The Washing Ready Indicator works by responding to the sound and or vibration that occurs while the washing machine motor is operating When correctly adjust ed other sources of sound have only a minimal effect unless they are particularly loud Even if they do have some temporary effect this should not prevent the circuit from giving a proper warning The sensor consists of an electret micro phone insert that is the working part without the external case While the motor is turning this provides an electrical signal which is passed to the main unit While the machine vibrations continue the warning does not sound When it stops the warning continues to be held off for a further preset time and after that the buzzer sounds HOLD OFF TIME This hold off time is necessary because the motor in a washing machine is not operating all the time during the washing cycle The drum turns in alternate direc tions to prevent the clothes tangling and there will be several seconds of silence between each movement There may also be longer quiet times when the machine is filling with water The hold off time must be sufficient to take account of all these factors and will be set by the user for best effect at the testing stage Everyday Practical Electronics May 2002 LONG SILENCE To prevent the warning being given while the washing machine is not in use obviously a long period of silence the unit must be switched on and
33. The circuit for the Freezer Alarm project uses the baby of the PIC family the one time programmable PIC12C508 microcontroller The rest of the components should be readily available For those readers unable to program this type of PIC a ready pro grammed PIC12C508 microcontroller can be purchased from Magenta Electronics amp 01283 565435 or www magenta2000 co uk for the inclusive price of 5 90 each overseas add 1 p amp p The software is available on a 3 5in disk EPE Disk 5 from the EPE Editorial Office for the sum of 3 each UK to cover admin costs for overseas charges see page 379 It is also available Free from the EPE web site ftp ftp epemag wimborne co uk pub PICS PICfreezer Simple Audio Circuits 1 We do not expect any component buying problems to be encountered when shopping for parts for the various amplifier modules called up in this month s Simple Audio Circuits projects All the audio amp i c s should be shelf items All the small printed circuit boards are available from the EPE PCB Service See page 379 for individual ordering codes and prices MAKE IT A GIFT EVERY MONTH AND SAVE UP TO 68p AN ISSUE NEXT MONTH DON T MISS OUT Xx BIOPIC HEARTBEAT MONITOR amp amp WORLD LAMP amp X SIMPLE AUDIO CIRCUITS 2 Annual subscription rates 6 Months UK 15 Overseas 18 standard air service 27 express airmail 1 Year UK 28 50 Overseas 34 50 stan
34. This data shows sev eral ways to put subjects under your control Included is a full vol ume reference text and several construction plans that when assembled can produce highly effective stimuli This material must be used cautiously It is for use as entertainment at parties etc only by those experienced in its use 15 set Ref F EH2 GRAVITY GENERATOR PLANS This unique plan demonstrates a simple electrical phenomena that produces an anti gravity effect You can actually build a small mock spaceship out of simple mate rials and without any visible means cause it to levitate 10 set Ref F GRA1 TESLA COIL LIGHTNING DISPLAY GLOBE PLANS Produces up to 750 000 volts of discharge experiment with extraordinary HV effects Plasma in a jar St Elmo s fire corona excellent science project or conversation piece 5 set Ref F BTC1 LG5 COPPER VAPOUR LASER PLANS Produces 100mW of visible green light High coherency and spectral quality similar to argon laser but easier and less costly to build yet far more efficient This particular design was developed at the Atomic Energy Commission of NEGEV in Israel 10 set Ref F CVL1 VOICE SCRAMBLER PLANS Miniature solid state system turns speech sound into indecipherable noise that cannot be under stood without a second matching unit Use on telephone to prevent third party listening and bugging 6 set Ref F VS9 PULSED TV JOKER PLANS Little handheld device utilises pulse technique
35. Tooley BA Regular Supplements Unlike a book or encyclopedia this Manual is a living work continuously extended with new material If requested Supplements are sent to you on approval approximately every three months Each Supplement contains around 160 pages all for only 23 50 2 50 p amp p You can of course return any Supplement within ten days which you feel is superfluous to your needs You can also purchase a range of past Supplements to extend your Base Manual on subjects of particular interest to you Presentation Durable looseleaf system in large A4 format Price of the Basic Work 39795 SALE PRICE 24 95 to include a recent Supplement FREE Offer ends May 31st 2002 g m a Our 30 day money back guarantee gives you complete peace of mind If you are not entirely happy with the Electronics Service Manual for whatever reason simply return it to us in good condition within 30 days and we will make a full refund of your payment no small print and no questions asked All we ask is that you pay the return postage Overseas buyers also have to pay our overseas postage charge Sorry but we can only make exchanges on the Modern Electronics Manual CD ROM version if the CD ROM is faulty we cannot offer a money back guarantee on this product as the content can be printed out fl p p p elele fee en et ee eee ee ee et en eee ee eee fet et eee eee eed eed ee fet et et et eed ede ee fen en eee eed fee ee
36. W 405mW 720mW 32 20mW 60mW 90mW 225mW W 390mW a Quiescent current 6mA Input resistance 5M ohms Input sensitivity for 680mW SPRING output 8 ohm load 9V supply FREQUEN 8 RIPPLE REJECTION a VR2 set for maximum resistance 56mV r m s gain 40 b VR2 set for minimum resistance 10mV r m s gain 230 Absolute maximum supply voltage BOOTSTRAP SUPFLY VOLTAGE EV beyond which damage will occur 16V SIGNAL OUT Suggested maximum supply voltage TOP VIEW OF TBA820M with a4 ohm speaker 9V with an 8 ohm speaker 12V High frequency response at 3dB point samt ik Ni with C6 220pF 20kHz Fig 5 Circuit diagram and pinout details for the TBA820M with C6 680pF 7kHz power amplifier See right for general performance details 344 Everyday Practical Electronics May 2002 COMPONENTS TBA820M AMPLIFIER See R1 22Q OLP R2 1Q S All 0 25W 5 carbon fim TALK age Potentiometers pag VR1 10k min rotary carbon log 100Q enclosed carbon preset Resistors VR2 Capacitors C1 4u7 radial elect 25V 220u radial elect 25V 2 off 100n disc ceramic 100u radial elect 25V 47u radial elect 25V 390p ceramic 220n polyester C2 C8 C3 C4 C5 C6 C7 Semiconductor IC1 TBA820M audio power amp i c Miscellaneous LS1 4 to 32 ohm loudspeaker see text Printed circuit board available from the EPE PCB Service code 345 TBA820M case optional size and type to choice 8
37. a quiet domestic setting the power fed to the speaker will hover around 50mW 0 05W and this is ample for the operator of a communications receiver whose ears are closer to the sound source During the valve era ten watts was considered adequate for the realistic reproduction of orchestral music and some experts suggested a figure as low as five One watt of power delivered to a TDA2003 Collection of simple i c power amplifier modules left to right top to bottom Single TDA2003 Amp Twin TDA2003 Amp 7DA7052 Amp 7BA820M Amp LM380N Amp LM386N 1 Amp Everyday Practical Electronics May 2002 reasonably efficient speaker will produce a loud sound a continuous five watts is becoming deafening and ten will rattle windows This assumes single channel or mono reproduction in a normal living room The impact is of course greater with a stereo system This is at odds with the high power rat ings of many of the quality amplifiers cur rently advertised The desire for a big reserve of power the low efficiency of some modern speakers and different ways of measuring output may account for the difference Output is variously rated as music power sustained music speech and music and sinewave power To add to the confu sion the figures are quoted at different dis tortion levels The standard most often used when valves were commonplace and the one adopted in this article is the r m s root m
38. added to these prices see their advertisement in this issue for details The 7 stage Darlington line driver type ULN2004A was also pur chased from Rapid see above code 82 0622 It is also listed by RS 01536 444079 or rswww com code 652 825 For those readers unable to program their own PICs a ready pro grammed PIC16F84 microcontroller can be purchased from Magenta Electronics amp 01283 565435 or www magenta2000 co uk for the inclusive price of 5 90 each overseas add 1 p amp p The software is available on a 3 5in PC compatible disk EPE Disk 5 from the EPE Editorial Office for the sum of 3 each UK to cover admin costs for overseas charges see page 379 It is also available Free from the EPE web site ftp ftp epemag wimborne co uk pub PICS PICbigdigit The printed circuit board is available from the EPE PCB Service code 341 see page 379 Finally the optional 4x4 matrix data entry keypad came from RS see earlier code 331 304 Washing Ready Indicator Some readers may experience difficulty in tracking down the specified quad op amp used in the Washing Ready Indicator project We have found that the Harris Semiconductors CMOS ICL7642ECPD quad op amp is stocked by RS code 630 623 and can be ordered through any bona fide stockists including some of our advertisers You can order direct credit card only from RS on 01536 444079 or through the web at rswww com A post and handling charge will be made The
39. allowed to ride a bike after a heart attack We need a machine that we can carry around and measure distances accurately We use 30 metre tapes at present I built the Earth Resistivity Meter Jan Feb 97 but the archeol ogist that wanted it has not yet built the frame I built a magnetometer last year that worked first time We have used it but found nothing so far If you can design a measuring wheel I would appreciate it That reminds me of a tale when I was in local government White lines were paid for by the yard One day an engineer had to measure a road about one mile long using the measuring wheel On that day he had been in the pub for lunch He was somewhat incapable so he called on a van driver to let him lay down in the back and he put the wheel down at the start of each line and lift ed it off at the end Unfortunately the driver decided that he was going too slow and the wheel started going faster and faster When they got to the end of the road they had measured enough white lines to stretch from London to Brighton Philip I m sorry to hear you can t enjoy the pleasures of pushbikes although I m on the verge of feeling that age is gradually putting a spoke in my wheels My PICagoras though can be used with any wheel and its diameter can be easily pro grammed into the unit using a signal generator I still think it might do for you but regret I can t offer to do it for you What a delightful tale It r
40. and badly thought out It might even produce a 90 per cent complete project that can be taken no further Without planning it is easy to pro duce projects that are fine apart from the fact there is insufficient space for the battery or the lid of the case can not be fitted into place Another popular mistake is to miss out a control or sock et which then has to be fitted in as best you can At best this produces some odd looking panel layouts At worst you find that one or two controls cannot be adjusted when the headphones are plugged in or something of this nature Project Cases Although there are many different types of project cases in use at pre sent they break down into two main categories The cheapest are the sim ple boxes that are normally of plastic construction but can be made of metal or a mixture of plastic and metal Instrument cases are generally larger and more expensive The simple boxes consist of a five sided main section plus a removable lid although the latter is often used as the front panel The more expensive metal types are of diecast aluminium construction and are very tough They also have good screening properties that prevent radio signals from entering or exiting The cheaper metal boxes use folded aluminium construction While nothing like as tough as the diecast variety they are more than adequate for most projects Z Dn s pE Instrument cases are a better choice for larger projects
41. and power coils chokes and trans formers Practically every possible type is discussed and calculations necessary are given and explained in detail Although this book is now twenty years old with the exception of toroids and pulse transformers little has changed in coil design since it was written Order code 160 4 49 OPTOELECTRONICS CIRCUITS MANUAL R M Marston A useful single volume guide to the optoelectronics device user specifically aimed at the practical design engineer technician and the experimenter as well as the electronics student and amateur It deals with the subject in an easy to read down to earth and non mathematical yet comprehensive manner explaining the basic principles and characteristics of the best known devices and presenting the reader with many practical applications and over 200 circuits Most of the i c s and other devices used are inexpensive and read ily available types with universally recognised type numbers Order code NE14 15 99 96 pages 182 pages OPERATIONAL AMPLIFIER USER S HANDBOOK R A Penfold The first part of this book covers standard operational amplif er based building blocks integrator precision rectifier function generator amplifiers etc and considers the ways in which modern devices can be used to give superior perfor mance in each one The second part describes a number of practical circuits that exploit modern operational amplifiers such as hig
42. as an oscillator using a method that is often overlooked by constructors It utilises one feedback tim ing resistor between the output pin 3 and the threshold pin 6 and a capacitor to control the frequency If the CMOS 7555 version is used then the fact that it switches from rail to rail means that you can obtain a 50 per cent duty cycle the main advantage of this type of circuit The result is a square wave appearing at pin 3 Everyday Practical Electronics May 2002 Turning to the H bridge arrangement this uses four power transistors wired in complementary opposing pairs When IC1 output goes high this turns on the npn transistor TR1 but the pnp transistor TR3 does not conduct The output of IC also triggers the mono stable IC2 the trig ger pin 2 needs to be taken low for the timer O IC1 PIN3 IC2 EQUIVALENT to trigger So with C1 output high IC2 trigger input is pulled high so C2 output remains low This allows the pnp transistor TR4 to conduct because its base is pulled low so with the pair TR1 and TR4 conducting hard current flows through the ultrasonic sound transducer LS1 as shown in Fig 3 The designer mentioned a current flow of 4 amps when using a bench power supply which I can well believe the Power Siren shown in Circuit Surgery June 1997 uses a ZSD100 siren chip and an H bridge driver to produce an ear splitting and highly effi cient loudspeaker siren When
43. batt TBI MIC1 SK1 PL1 Approx Cost Guidance Only Everyday Practical Electronics May 2002 the negative OV of the supply that is to TB1 3 The other one is connected to TB1 2 Connect the PP3 battery snap or as appropriate to TB1 1 and TB1 4 taking care over the polarity Insert the cells in their holder apply the battery snap and switch on Adjust Sensitivity preset VR1 to the point where the test l e d D1 is just off If the microphone is touched or the table top is tapped the l e d should flash momentarily Adjust VR1 so that this hap pens reliably The battery should now be disconnected and C2 inserted into its socket observing the anti static precautions mentioned earli er for IC1 It is best to leave the l e d in cir cuit for the moment Positioning of components inside the plastic case With no sound detected buzzer WD1 should operate Sound should make the buzzer stop but begin again as soon as it stops This might not work properly unless preset VR2 is adjusted slightly clockwise to give a small hold off time If that works adjust VR2 to provide a longer hold off time of say 30 seconds Check that if sounds are made periodi cally within this time the sound is held off This will provide an approximate setting but final adjustments to the presets can only be made with the unit under actual operating conditions BOXING UP Remove the temporary sensor wires from termin
44. character display data all components and software to include in your own programs Ideal development base for meters terminals calculators counters timers Just waiting for your application PIC 16F84 MAINS POWER 4 CHANNEL CONTROLLER amp LIGHT CHASER WITH PROGRAMMED 16F84 AND DISK WITH SOURCE CODE IN MPASM ZERO VOLT SWITCHING MULTIPLE CHASE PATTERNS OPTO ISOLATED 5 AMP OUTPUTS 12 KEYPAD CONTROL SPEED DIMMING POT HARD FIRED TRIACS Kit 855 39 95 8 CHANNEL DATA LOGGER As featured in Aug Sept 99 EPE Full kit with Magenta redesigned PCB LCD fits directly on board Use as Data Logger oras a test bed for many other 16F877 projects Kit includes programmed chip 8 EEPROMs PCB case and all components KIT 877 49 95 inc 8 x 256K EEPROMS ICEBREAKER noooo0o0o0000 INCLUDES 1 PIC16F84 WITH DEMO PROGRAM SOFTWARE DISK PCB INSTRUCTIONS AND 16 CHARAC TER 2 LINE LCD DISPLAY Now features full 4 channel chaser software on DISK and pre programmed PIC16F84 chip Easily re programmed for your own applica tions Software source code is fully commented so that it can be followed easily LOTS OF OTHER APPLICATIONS PIC Real Time In Circuit Emulator Icebreaker uses PIC16F877 in circuit debugger Links to Standard PC Serial Port lead supplied Windows 95 Software included Works with MPASM and MPLAB Microchip software 16 x 2 L C D Breadboard Relay I O devices and patch leads
45. charge carriers e g electrons rather than a continuous flow This noise is known as shot noise and like thermal noise is due to fundamental physics and cannot be reduced For an applied current of J in amps A the shot noise is given by IN pms V2eLAf rms where e is the electronic charge charge on one electron 1 6 x 10 719C Coulombs and Af is the bandwidth as before For a current of 14A this is 0 S7pA Hz 2 which is about 80pA over a 20kHz bandwidth 80pA noise on luA is a variation of 0 008 which is an SNR signal to noise ratio of around 82dB For very low currents the effect of shot noise becomes increasingly significant limiting the accuracy of low level measure ments Shot noise is an important source of noise in semiconductor devices such as diodes and transistors YET MORE NOISE In addition to thermal noise and shot noise resistors and active devices produce yet more noise for various and often com plex reasons This noise is called flicker noise also known as 1 f noise or pink noise as it typically has a 1 f relationship with frequency f as defined last month Unlike thermal and shot noise flicker noise in resistors and other devices depends on the component type and manu facture and can even vary quite widely for components of same type For a decade bandwidth frequency range of 1 to 10 times the flicker noise for typical resistors varies from tens of nanovolts to a few mic
46. crystal Printed circuit board available from the EPE PCB Service code 341 RW44 10 inch 7 segment electromechanical display big digit quantity to suit see text 4 x 4 data entry keypad optional see text stranded colour coded con necting wire individual wires or ribbon cable 12V d c power source min 500mA output 1mm terminal pins or pin headers 16 pin d i l socket 7 off see text 18 pin d i l socket printer port con nectors to suit optional see text sol Approx Cost der etc Guidance Only 20 excluding hardware required to constantly provide around 40mA due to the two L293DN devices It is thus likely to get a bit warm especially if the source power is 12V or greater If it is found to shut down through exces sive heat it is thermally regulated change it to a standard 7805 5V 1A device It is per haps prudent to switch off power during long periods of digit inactivity Note that the digits themselves only con sume power during the brief pulse that changes their segment display position Capacitors C1 C2 C6 and C7 help to maintain powerline stability CONSTRUCTION Printed circuit board component and track layout details are shown in Fig 8 This board is available from the EPE PCB Service code 341 Assemble in order of link wires first including the one marked Bank 1 Link this will be discussed under Expansion Note that some links go under the i c 32
47. easiest way is to use a standard printer cable with pre attached connectors The printer end of the cable has a 36 way male D type Centronics con nector which requires a matching female type at the unit end The latter should be hardwired to the board at the designated points using short lengths of insulated stranded wire The pinouts for a right angled female connector are shown in Fig 10 9 a 8B amp 4 S 2 il REAR VIEW Fig 9 Keypad connection details HANDSHAKE PIN 9 CONNECT TO OV Alternatively the unit can be hardwired to a separate 25 way D type male connec tor plugged into the back of the computer 10 way ribbon cable would be ideal The connector s pinouts are shown in Fig 11 Note that the Error line connects to the board pin situated near IC8 Error is the name given in respect of that line s normal purpose when interfaced to a printer Before inserting the d 1 1 1 c s do a thor ough examination of the board for faulty assembly and soldering Then only insert them after you have established that regu lator IC9 is correctly supplying 5V at its output Check this again once the i c s have been inserted Be aware that they are CMOS devices and require the nor mal handling precau tions discharging sta tic electricity from your body by touch ing the bare metal of something earthed before handling them Adjust preset VR1 to a fully clockwise setting maximum pulse
48. high speed band printer 1950 Fujitsu M3041D 600 LPM printer with network interface 1250 Siemens K4400 64Kb to 140Mb demux analyser 2950 Perkin Elmer 299B Infrared spectrophotometer 500 Perkin Elmer 597 Infrared spectrophotometer 3500 VG Electronics 1035 TELETEXT Decoding Margin Meter 3250 LightBand 60 output high spec 2u rack mount Video VDA s 495 Sekonic SD 150H 18 channel digital Hybrid chart recorder 1995 B amp K 2633 Microphone pre amp 300 Taylor Hobson Tallysurf amplifier recorder 750 ADC 8200 Carbon dioxide gas detector monitor 1450 BBC AM20 3 PPM Meter Ernest Turner drive electronics 75 ANRITSU 9654A Optical DC 2 5G b waveform monitor 5650 ANRITSU ML93A optical power meter 990 ANRITSU Fibre optic characteristic test set POA R amp S FTDZ Dual sound unit 650 R amp S SBUF E1 Vision modulator 775 WILTRON 6630B 12 4 20GHz RF sweep generator 5750 TEK 2445 150 MHz 4 trace oscilloscope 1250 TEK 2465 300 Mhz 300 MHz oscilloscope rack mount 1955 TEK TDS380 400Mhz digital realtime disk drive FFT etc 2900 TEK TDS524A 500Mhz digital realtime colour display etc 5100 HP3585A Opt 907 20Hz to 40 Mhz spectrum analyser 3950 PHILIPS PW1730 10 60KV XRAY generator amp accessories POA VARIACS Large range from stock call or see our website CLAUDE LYONS 12A 240V single phase auto volt regs 325 CLAUDE LYONS 100A 240 415V 3 phase auto volt regs 2900 ee 6 CS CS ALL MAIL TO 18 Milli
49. is going on The state machine then controls the position counter A state machine is a sequential logic sys tem whose outputs depend on the previous and present inputs as in a counter for instance as opposed to processes that are functions of present inputs alone Fortunately incremental position sensor decoder i c s are available for example the HCTL 200xx series from Agilent Technologies formerly Hewlett Packard These chips also include simple digital fil ters to remove glitches from the input waveforms Specialist motion control processors such as the LM628 from National Semiconductor also have built in quadrature decoders and counters OPTICAL ENCODING SENSORS As we have seen it is possible to detect the rate and angle of rotation using special ly designed discs and optical sensors There are several techniques and a number of readily available sensors that we can use Photodiode or phototransistor and l e d AS shown in Fig 7 12 the l e d and photosensor are mounted on oppo site sides of the encoding disc that has alternating transparent and opaque areas The photosensor will detect light shining through the transparent area TRANSPARENT SECTION OF DISC PHOTOTRANSISTOR OR PHOTODIODE EDGE ON DISC Fig 7 12 Sensing using a separate l e d and photosensor Slotted optosensors A slotted optosen sor has a built in phototransistor and l e d mounted facing each other across a smal
50. its input and source current out when it s high You could perhaps force the inverter Operation more by ensuring the mono stable period is even shorter still Overall it s quite a cunning design and I look for ward to constructing one myself My thanks to Dave Stringwell in Scunthorpe for submitting the design ARW 363 ELECTRONICS CD ROMS ELECTRONICS PROJECTS gale Probe testing Electronic Projects is split into two main sections Building Electronic Projects contains comprehensive information about the components tools and techniques used in developing projects from initial concept through to final circuit board production Extensive use is made of video presentations showing soldering and construction techniques The second section contains a set of ten projects for students to build ranging from simple sensor circuits through to power amplifiers A shareware version of Matrix s CADPACK schematic capture circuit simulation and p c b design software is included The projects on the CD ROM are Logic Probe Light Heat and Moisture Sensor NE555 Timer Egg Timer Dice Machine Bike Alarm Stereo Mixer Power Amplifier Sound Activated Switch Reaction Tester Full parts lists schematics and p c b layouts are included on the CD ROM ANALOGUE ELECTRONICS Sea etree ied Complimentary output stage Counter project Analogue Electronics is a complete learning resource for this most difficult b
51. level Vppp in Fig 7 1 sometimes called the thresh old and the other input is connected to the signal of interest e g from a sensor A real op amp may not switch when the input is at exactly Vppp due to offsets Furthermore for a range of input volt ages the op amp will be in normal lin ear mode and will output intermediate voltages see Fig 7 1lc This range of inputs is very small however and the sit uation is much better using an op amp than say a single transistor as we will see in this month s Lab Work Fig 7 2 Response of an inverting regenerative comparator The simplest use of a comparator with a sensor is to switch a load on or off when the sensor output goes above or below a partic ular level For example to produce an over or under temperature alarm A window comparator uses two comparators to indi cate when a signal is between two levels These circuits are often used to determine if a measured value is between acceptable limits An ideal comparator would switch instantaneously when the input signals cross the comparison threshold A real comparator takes a finite time before it reacts This time is known as the propaga tion delay An ideal comparator s output voltage switches between its two possible output states instantaneously Again a real com parator takes a finite time The rate of Fig 7 3 Comparator without hysteresis Everyday Practical Electronics May 2002 Fig 7
52. may be able to see the hysteresis better by replac ing the 1 d r with a 100kQ variable resistor potentiometer which will allow you to vary the input voltage in a controlled way 374 ee LETI Breadboard assembly for circuit in Fig 7 18 Breadboard assembly for circuit in Fig 7 20 If you compare the results from this experiment with the transistor based light switch in Part 2 then it is obvious that a well designed comparator is much better Lab 7 2 Anemometer using an Optical Sensor For this anemometer we use the incre mental encoder disc in Fig 7 10 and a sin gle reflective optosensor to measure wind speed in a similar manner to that used with the magnetic sensor design in last month s Teach In The general principle of operation was illustrated in Fig 7 16 where a counter is used to accumulate pulses over a known period of time and then the count is con verted into an analogue voltage using a dig ital to analogue converter DAC The complete circuit diagram of the anemome ter is shown in Fig 7 22 The output of the photosensor X1 is amplified by transistor TR1 and then input to an 8 bit binary counter formed using the two 4 bit counters ICla and IClb The counter increments on the positive going edges received at ICla s clock input CPOA pin 1 When Cla rolls over from 15 to 0 overflow the negative going output at OA3 pin 6 triggers the second counter IC1b via its CP1B input pin
53. num ber giving us an angular resolution of 45 degrees AVOIDING UNCERTAINTY This seems fine but actually it is not a sensible way of patterning the disc The problem is that unless the sensors are perfectly aligned as we move from one Fig 7 7 a Disc patterned with binary code b arrangement of sensors segment to the next the bits which change may not do so at the same instant leading to unwanted intermediate codes The worse case in the Fig 7 7 example is the change from 000 to 111 or vice versa where any 3 bit number or even a sequence of two numbers could appear as an intermediate code The solution is to pattern the disc so that only one bit changes as we move from one segment to the next as shown in Fig 7 8 This type of binary code is called a Gray code and a 3 bit Gray code is shown in Table 7 1 We can use a logic circuit to con vert it to standard binary numbers as shown in Pig 7 9 Using code patterned discs is useful where the disc position is simply an angle but if the movement of the disc over multiple revolutions must be measured it is less use ful Furthermore if high resolution is required the printing of the disc becomes complex and difficult and a potentially large number of sensors is required one per bit Fig 7 8 Gray coded disc Everyday Practical Electronics May 2002 Table 7 1 3 bit Gray Code Output Codes A B C 0 0 0 0 0 1 0 1 1 0 1 0 1 1 0 1 1 1 1 0 1
54. off manual ly The user is unlikely to forget to switch it off because the buzzer will continue to sound until this has been done However he or she will need to remember to switch it on at the beginning of the washing cycle whenever a warning is required HOW IT WORKS Basic operation of the Washing Ready Indicator is best illustrated by the block diagram shown in Fig 1 It will be seen that this comprises seven main parts vibration sensor audio amplifier level detector integrator Schmitt trigger invert er slow astable low frequency oscillator and piezo buzzer The complete circuit diagram is shown in Fig 2 MICI is the electret microphone insert of the type specified in the parts list This has an inbuilt f e t preamplifier which requires its own power supply This is derived from the 6V battery pack B1 through resistor R1 Operational amplifier op amp IC1 is a quad device it contains four identical units ICla IC1b IC1c and IC1d although only three of these are actually used ICla is used for the audio amplifier IC2b for the level detector and Clc for the Schmitt trigger inverter Taking Cla first this is used in a c inverting mode For this the signal arriv ing from the sensor MICI is applied via coupling capacitor Cl and input resistor R2 to the inverting input pin 2 Capacitor C1 allows the alternating cur rent a c component that 1s the signal to pass while blocking the passage of dir
55. printed as part of the magazine or in inserts The Publishers regret that under no circum stances will the magazine accept liability for non receipt of goods ordered or for late delivery or for faults in manufacture TRANSMITTERS BUGS TELEPHONE EQUIPMENT We advise readers that certain items of radio transmitting and telephone equipment which may be advertised in our pages cannot be legally used in the UK Readers should check the law before buying any transmitting or telephone equipment as a fine confiscation of equipment and or imprisonment can result from illegal use or ownership The laws vary from country to country readers should check local laws als Constructional Project FREEZER ALARM HUMPHREY BERRIDGE Simply protect your food learn about using the amp pin PIC12C508 and about applying the Watchdog Timer OME modern freezers contain alarms which sound if you leave the door open and allow the internal space to warm up However they do not work if the freezer suffers a power failure which is a bit of a drawback Making a temperature sensitive circuit which can sound an alarm is not too diffi cult a typical example was the Ice Alert in Feb 01 but what is required here is a low cost circuit which can run on batteries for a very long time This design uses a circuit based on a PIC using a feature about which little has been written namely the ability to send it to sleep The circuit is extrem
56. radio systems fixed or mobile RADIO BYGONES is the magazine for you ARTICLES on restoration and repair history circuit techniques personalities reminiscences and just plain nostalgia you ll find them all Plus features on museums and private collections and a full colour photo feature In every issue IT S MOSTLY about valves of course but solid state whether of the coherer and spark gap variety or early transistors also has a place FROM THE DAYS of Maxwell Hertz Lodge and Marconi to what was the state of the art just a few short years ago There is also a selection of free readers For Sale and Wanted advertisements in every issue Radio Bygones covers it all THE MAGAZINE is published six times a year and is available by postal subscription It is not available at newsagents TO TAKE OUT a subscription or to request a sample copy please complete the form below and return it to RADIO BYGONES Wimborne Publishing Ltd 408 Wimborne Road East Ferndown Dorset BH22 9ND Tel 01202 873872 Fax 01202 874562 Web sites www radiobygones co uk www radiobygones com RADIO BYGONES ORDER FORM TaT a My card number is A SAMPLE Copy of Radio Bygones Add 70p for overseas Airmail postage SUBSCRIPTIONS post paid 1YEAR 2 YEAR UNITED KINGDOM 18 50 35 00 REST OF EUROPE AIRMAIL 20 50 39 00 Expiry date Switch Issue No REST OF THE WORLD AIRMAIL 24 50 47 00 My name is J Yes I woul
57. relates that value to a binary sequence in respect of the digit segments to be turned on The sequence is in the right to left order bit O to bit 7 of segment A to segment G For example binary 01111111 turns on all segments resulting in the 7 segment dis play of numeral 8 Binary 00000110 on the other hand only turns on segments B and C resulting in numeral 1 being dis played The full table is shown in Listing 1 LISTING 7 TABLE addwf PCL F retlw 00111111 retlw 00000110 retlw 01011011 retlw 01001111 retlw 01100110 retlw 01101101 retlw 01111101 retlw 00000111 retlw 01111111 retlw 01100111 retlw 01110111 retlw 01111100 retlw 00111001 retlw 01011110 retlw 10000000 14 blank retlw 01000000 15 GFEDCBA ooNOoQaGAAOMN O Note that bit 7 in the 14th jump is set at 1 This prevents the PIC from returning a zero value from this location which would otherwise be recognised as no data entered from keypad Whilst it is suggested that decimal dis play values from 0 to 9 are retained other segment arrangements could be provided for the other six positions by readers hav ing their own PIC assembly programming facilities such as the author s Toolkit Mk3 TK3 Oct Nov 01 It is also worth recognising that 7 seg ment displays cannot in many instances be used to represent alphabet characters For example capital letter A can be represent ed but lower case a cannot Conversely b can be
58. supplied As featured in March 00 EPE Ideal for beginners AND advanced users Programs can be written assembled downloaded into the microcontroller and run at full speed up to 20MHz or one step at a time Full emulation means that all I O ports respond exactly and immediately reading and driving external hardware Features include Reset Halt on external pulse Set Breakpoint Examine and Change registers EEPROM and program memory Load program Single Step with display of Status W register Program counter and user selected Watch Window registers KIT 900 34 99 POWER SUPPLY 3 99 STEPPING MOTOR 5 99 Fax 01283 546932 Tel 01283 565435 Everyday Practical Electronics May 2002 EPE PIC TOOLKIT 3 e THE LATEST TOOLKIT BOARD 8 18 28 AND 40 PIN CHIPS e MAGENTA DESIGNED P C B WITH COMPONENT LAYOUT AND EXTRAS e L C D BREADBOARD AND PIC CHIP INCLUDED e ALL TOP QUALITY COMPONENTS AND SOFTWARE SUPPLIED KIT 880 34 99 with 16F84 39 99 with 16F877 PIC TOOLKIT V2 SUPER UPGRADE FROM V1 18 28 AND 40 PIN CHIPS READ WRITE ASSEMBLE amp DISASSEMBLE PICS SIMPLE POWER SUPPLY OPTIONS 5V 20V ALL SWITCHING UNDER SOFTWARE CONTROL MAGENTA DESIGNED PCB HAS TERMINAL PINS AND OSCILLATOR CONNECTIONS FOR ALL CHIPS e INCLUDES SOFTWARE AND PIC CHIP KIT 878 22 99 with 16F84 29 99 with 16F877 EPE PIC Tutorial At last A Real Practical Hands On Series e Learn Programmi
59. technique used in the project does not match that of the original Enigma machine As mentioned in the article my design was never meant to be a simulation of the original howev er to the untrained eye the coded message would still be difficult to crack I am sure that if you wanted to make the encryption technique more secure it would be quite straightforward to alter the software I would certainly be interested to know if anybody tries it Don t forget that the message could be made more secure if the user transfers the encrypted message into the match box memory unit By using this method the would be cracker would first need to know how to retrieve the data out of the PIC s EEPROM memory which of course is in encrypted binary format and then attempt to decipher the message How this affects the possibility of cracking the code is practically immeasurable Nick Dossis WEATHER MONITORING Dear EPE I came across your magazine quite by chance with the February issue For some time now I have been wanting to put together a weather sta tion just for my own records I am more mechanical hydraulic orientated but have sort of taught myself a bit about the electrical side Am currently doing a course with Colu to make me Mech Elect Have looked at some of the off the shelf jobs just plug in as it were but my good ness what a price Wonder if NASA can afford them Do you perhaps know where I can purchase stand alone units se
60. ten years of research into the new cell there is still plenty that needs to be done However success will bring with it large returns because there is a growing aware ness of global warming and new initiatives like these are likely to pay off the research and development costs many times over Other groups are also investigating simi lar technologies For example Bell Labs have produced a solar cell that is based around pentacene an organic semiconduc tor Reports indicate that this achieved effi ciency levels of around 4 but they still need to investigate many aspects such as the effect of ultraviolet light on the organic semiconductor These new developments often take ten to fifteen years to be completed but reports indicate that the new solar cells could be available in five years or so Everyday Practical Electronics May 2002 A roundup of the latest Everyday electronics PICS BREAK 1MB BARRIER MICROCHIP S new Flash microcontrollers are the first the break the one megabit memory barrier The PIC18F6620 PIC18F8620 PIC18F6720 and PIC18F8720 offer field programmability larger memory a higher pin count and the most feature rich peripheral set that Microchip has produced so far Programming times allow a 1 megabit array to be fully erased and pro grammed in under two seconds The 620s feature 64K bytes of Flash memory while the 720s have 128K bytes 1Mbit The 8620 and 8720 also have a linear address c
61. to be covered by solar cells to enable a useful amount of electricity to be generat ed This means that the costs are prohibi tively high for most applications The raw silicon from which the solar cells are made is plentiful and cheap Unfortunately the processing costs mean that the completed cells are expensive especially considering the areas that have to be covered to collect a useful amount of light for conversion If solar generated elec tricity is to become common then cheaper methods of converting the sunlight into electricity are needed Photosynthesis In the search for more efficient and cost effective methods of converting sunlight into electrical energy scientists have investigated the way in which plants convert solar energy into chemical energy to explore any leads that could be followed and utilised for elec trical energy conversion This line of research was first investigated in the 1970s The basic idea that was adopted was to use a layer of dye molecules that are high ly absorbent to light This is placed onto the surface of a semiconductor and once the dye is excited it delivers an electron into the conduction band By adopting this approach the operation of the device is no longer dependent upon the absorption level of the semiconductor but the dye over which there is more control The drawback of using this approach is that the electrons move very slowly through the dye layer and this reduces the effi
62. transparent film or photopa per or consider large Avery invisible clear inkjet labels and affix it to your project The whole point of such software pack ages of course is that you can play around on screen to your heart s content without doing any damage to that precious anodised aluminium panel See you next month you can email Alan at alan epemag co uk or visit his web site at http homepages tcp co uk alanwin Everyday Practical Electronics May 2002 Regular Clinic CIRCUIT ALAN WINSTANLEY and IAN BELL Pere WU Val E ITT s 5 Our monthly feature of readers queries looks at analogue opto couplers and a timely problem Linear Opto coupler My thanks to Dave Larner who writes by email I found the March instalment of Teach In 2002 with the practicalities of the instru mentation amplifier very informative and helpful I wondered if you could give me a pointer of where to look for a linear opto coupler I have been experimenting with some of the biofeedback circuits dating back to Practical Electronics May 1987 I would like to connect these to my oscil loscope or maybe some kind of recorder This would leave the biofeedback circuit battery powered for reasons of safety and electrical noise I have tracked down a number of data sheets but the applications all seem to be for coupling digital circuits Are there specialist types available We re pleased you re enjoying Teach
63. 1 0 0 A inner ring of Fig 7 8 B middle ring of Fig 7 8 C outer ring of Fig 7 8 BINARY O Fig 7 9 Gray code to binary code converter INCREMENTAL ENCODING An alternative approach called an incre mental encoder uses two sensors that gen erate a quadrature signal that is two waveforms offset by a 90 degree phase shift Movement is indicated by the output of either sensor switching and direction is indicated by the relative phase plus or minus 90 degrees of the signals These signals can be used to control a counter to obtain a binary representation of position As this approach unlike the Gray code disc does not directly indicate absolute location a third sensor may be used to provide an index or reference point Fig 7 10 motion sensing a disc pattern b sensor locations Incremental encoder for Everyday Practical Electronics May 2002 An incremental encoder disc pattern and its sensor locations are shown in Fig 7 10 The quadrature signal is obtained from sen sors A and B and the reference signal from sensor I The spacing of the alternate black and white zones determines the resolution with which location can be measured The sepa ration distance between sensors A and B is half the length of the black and white sec tions The waveforms obtained from the sensors are shown in Fig 7 11 CLOCKWISE Fig 7 11 Quadrature signals from the incremental encoder in Fig 7 10 We can b
64. 10 causing it to increment The eight outputs are connected to a TLC7524 8 bit DAC IC2 connected to pro duce an output voltage at its pin 15 REF As discussed in the tutorial section the output voltage is SV x D 256 where D is the digi tal input value between 0 and 255 In the prototype the photosensor used was a type SG 2BC chosen for its small size Other common reflective optosensors that could be used include the SY CR102 and OPB706B TIMING The circuit based around the four 2 input Schmitt NAND gates within IC3 performs all timing logic N B Some components See are repeated between Lab viene S IOR LDR1 ORP12 light dependent resistor Resistors R1 to R4 0 25W 5 carbon film Semiconductors D1 BZY88C 2 7V Zener diode IC1 OP177 op amp Lab 7 2 Resistors R1 56002 R2 56k R3 390Q R4 4k7 R5 10k R6 R7 39k 2 off All 0 25W 5 carbon film Potentiometer VR1 22k preset min round Capacitors 47u tantalum 16V 10n ceramic 2 off Semiconductors TR1 BC548 or similar small signal npn transistor IC1 4520 dual binary counter IC2 TLC7524 8 bit digital to analogue converter IC3 4093 quad 2 input Schmitt NAND gate Miscellaneous X1 SG 2BC reflective photointerrupter see text Lab 7 3 Resistors R1toR3 560 3 off R4toR6 56k 3 off R7to RQ 390 3 off R10 to R12 4k7 3 off R13 to R20 470Q 8 off All 0 25W 5 carbon film Semiconductors D1itoD
65. 13 Ignore the unused pads Whereas the 14 segment wires of each harness are connected in parallel to each digit each digit needs its own separate 12V power supply wire originating from the control unit p c b as shown in Fig 8 Make the 12V connections in numerical order in relation to the digit positions in the proposed display Before you fully interwire the digits though it is recommended that you just wire up for the first one and check out the system VIEWED FROM REAR OF SOCKET PLUGGED INTO COMPUTER PARALLEL PORT Fig 11 Alternative connections via a 25 way male D type 329 KEYPAD OPERATION The software has been written so that on power being switched on the PIC sets its Port B for input with the input pull up resistors active A check is then made to see if the inputs are connected to any source that pulls them low Under keypad control with no keys pressed there is nothing to pull the pins low and so the PIC assumes that a keypad is the data entry source Having established that fact the soft ware goes into a perpetual loop scanning the keypad for keypresses The software routine used is a variant of that described in the author s Using PICs with Keypads of Jan O1 In response to any keypresses look up tables are used to relate that input value to the data to be sent to the digits The first table VALUE allocates the keypress data to a numerical value between O and 15 Another table TABLE then
66. 15 PC CONTROL DATA OPTIONS Because of the greater variety of seg ment codes that can be generated via the PC than with the keypad there is the option to program the PC software with any segment combination required The data is held in a look up table which can be added to by readers who have QBasic or QuickBASIC resident on their PC The data is held as in the format extract example shown in Listing 3 in the bit order of segments ABCDEFG the opposite order used by the PIC software s table 332 DATA 01111110 DATA 10110000 DATA 21101101 DATA C1001110 DATA c0001101 DATA D0000000 DATA d0111101 DATA K0000000 DATA k0000000 DATA 0000000 When the program is started all data statements are Read and analysed The first character in each data string holds the keyboard character that represents the following 7 bit segment data Its ASCII value is taken and the remaining seven bits in the data are stored in a string array seg x at the address corresponding to the ASCII value For example in the first case 01111110 the leading 0 is the first character Its ASCII value is 48 and so the rest of the data string 1111110 is stored at string array position seg 48 In the fourth case C is the character having the ASCII value 67 so its 7 bit string data is stored at seg 67 Note that some data statements have had to be enclosed in quotes so that the pro gram recognises the
67. 2 49 Ref HA1 CROOKES RADIOMETER Fascinating glass bulb contains blades driven around by the sun 9 99 Ref SC120B GIANT TV OR PC VIEWING SCREEN Turn your TV into a super size screen converts small screens into a super size 26in 26 99 Ref SVGA2 RADIOSONDES Made by Valsala unused they measure pres sure temperature and humidity Model RS80 good stripper at 15 Ref SONDE AIR WIND POWER MODULE Produces nearly 400 watts of power from the wind 1 14m blade 12V d c output 3 year war ranty built in battery regulator 549 Ref AIR1 WORMERIES The ideal solution for your kitchen waste Supplied complete with worms Turn your rubbish into liquid feed Two sizes available small ideal for 1 2 people 25 45 Ref WM2 and a large one ideal for 4 or more 42 44 Ref WM1 COMPLETE WIRELESS CCTV SYSTEM Includes monitor cam era up to 100m range audio and video UK legal complete with infra red lights 169 Ref WMS333 PELTIER MODULES 56W 40mm x 40mm 16V sealed edges new and boxed Supplied with 18 page Peltier design manual fea turing circuit designs design information etc 1 module and manu al is 29 99 Ref PELT1 pack of 4 modules and manual is 99 99 Ref PELT2 The manual on its own is 4 Ref PETS DC MOTOR 12V d c general purpose model motor 70mm x 50mm 12V d c permanent magnet 4mm x 25mm shaft 6 Ref GPM1 pack of 10 is just 40 Ref GPM2 180R P M MAINS MOTOR Induction type 90m
68. 20mA even when the outputs are in a high impedance state The enable inputs do not place the device into a qui escent state in high impedance mode unlike many logic devices that you may be familiar with Regrettably it is not cheap OUTPUT INPUTS OUTPUT L LOW X IRRELEVANT Z HIGH IMPEDANCE OUTPUT OFF Fig 4 L293DN pinouts and logic table Do not use any other type of L293 device The L293DN note the DN suffix is a 16 pin device with diode protection Other L293 device types may not have the same characteristics the L293E for instance has 20 pins and cannot be used MULTIPLEX CIRCUIT A simplified block diagram of the con trol requirement is shown in Fig 5 The circuit diagram showing the multi plexing and digit drive devices is given in Fig 6 Control data originates from a PIC16F84 microcontroller discussed presently in relation to Fig 7 Through multiplexer C1 3 bit control data selects which digit is to be powered via source drivers IC2 or IC3 As shown in Fig 6 and designed on the printed circuit board to be described later eight digits one bank can be controlled by these two drivers Additional digit source drivers can be added separately if required on stripboard for example although no constructional details on this are offered If fewer that five digits are to be con trolled IC3 can be omitted The eight outputs of IC1 are common to all digit drivers
69. 3872 On Line Editor ALAN WINSTANLEY EPE Online Internet version Editors CLIVE MAX MAXFIELD and ALVIN BROWN READERS ENQUIRIES E mail techdept epemag wimborne co uk We are unable to offer any advice on the use purchase repair or modification of commercial equipment or the incorporation or modification of designs published in the magazine We regret that we cannot provide data or answer queries on articles or projects that are more than five years old Letters requiring a personal reply must be accompanied by a stamped self addressed envelope or a self addressed envelope and international reply coupons All reasonable precautions are taken to ensure that the advice and data given to readers is reliable We cannot however guarantee it and we cannot accept legal responsibility for it COMPONENT SUPPLIES We do not supply electronic components or kits for building the projects featured these can be supplied by advertisers see Shoptalk We advise readers to check that all parts are still available before commencing any project in a back dated issue ADVERTISEMENTS Although the proprietors and staff of EVERYDAY PRACTICAL ELECTRONICS take reasonable precautions to protect the interests of readers by ensuring as far as practicable that advertisements are bona fide the maga zine and its Publishers cannot give any under takings in respect of statements or claims made by advertisers whether these advertise ments are
70. 4 below Component layout interwiring and full size copper foil master for the TDA7052 Amp Semiconductor IC1 TDA7052 power amp i c 1 2IN 30 5mm Miscellaneous LS1 4 to 32 ohm loudspeaker see text SCREENED INPUT LEAD Printed circuit board available from the POW EROUESEE YE EPE PCB Service code 344 TDA7052 case optional size and type to choice 8 pin d i l socket multistrand connecting wire audio screened cable solder pins solder etc Approx Cost cg 50 Guidance Only a excluding case amp speaker POWER SUPPLY VE OV TO SPEAKER LS1 VR1 FRONT VIEW WV EOM AMPLIFIER A circuit diagram incorporating the TBA820M audio amp i c which is manufactured by SGS Thomson together with a general performance guide is given in Fig 5 The input arrangements supply line bypassing speaker coupling and Zobel network are conventional and the relevant components can be identified from previous circuit descriptions Gain can be controlled by shunting an internal negative feedback loop which is accessed at pin 2 Preset potentiometer VR2 placed in 2 Completed TBA820M 3V TO 12V amplifier module a LS1 s 5 TBA820M POWER AMPLIFIER n R M S power output just before the onset IC1 H of waveform clipping TBA820M Speaker Supply Voltage Impedance Ohms 3V 4 5V 6V 9V 12V 4 10mW 320mW 405mW W 980mW 8 20mW 200mW 300mW 680mW 1 1W 16 30mW 115mW 180mW
71. 418MHz radio transmitter and receiver modules to remote control systems 160 pages Order code BP413 6 49 PRACTICAL ELECTRONIC MODEL RAILWAY PROJECTS R A Penfold The aim of this book is to provide the model railway enthusiast with a number of useful but reasonably sim ple projects that are easily constructed from readily available components Stripboard layouts and wiring diagrams are provided for each project The projects covered include constant voltage controller pulsed con troller pushbutton pulsed controller pulsed controller with simulated inertia momentum and braking automatic signals steam whistle sound effect two tone horn sound effect automatic two tone horn effect automatic chuffer The final chapter covers the increasingly popular sub ject of using a computer to control a model railway lay out including circuits for computer based controllers and signalling systems Order code BP384 5 49 A PRACTICAL INTRODUCTION TO SURFACE MOUNT DEVICES Bill Mooney This book takes you from the simplest possible starting point to a high level of competence in handworking with surface mount devices SMD s The wider subject of SM technology is also introduced so giving a feeling for its depth and fascination Subjects such as p c b design chip control soldering techniques and specialist tools for SM are fully explained and developed as the book progresses Some useful constructional projects are also include
72. 52 is approximately 220mA or almost double under these conditions In all cases the signal input pin has been connected to the slider moving con tact of the Volume control potentiometer via a blocking capacitor in the case of the TDA2003 This minimises hum and noise and ensures that a more or less con stant impedance is presented to the signal source Potentiometers of 4700 ohms or 10 kilohms 10k are usual but the value can be increased to 100k to raise input impedance This will however make the circuits more vulnerable to mains hum r f interfer ence and instability and the value should be kept as low as the signal source imped ance permits This applies particularly to the TDA7052 where the value of the Volume control should if possible be no more than 10k Earlier comments regard ing stability are of relevance here LINES SEIN AMPLIFIER A circuit diagram for a simple amplifier using the low voltage LM386N 1 power amplifier i c is shown in Fig 1 Also shown are the general performance and electrical characteristics of the circuit Blocking capacitor C1 prevents any disturbance of the d c con ditions in the signal source and potentiometer VR1 the Volume control sets the input level The manufacturers of the chip National Semiconductor suggest an input network to roll off high frequencies and resistor R1 and capacitor C2 perform this function The unused non inverting input pin 3 is grounded to avo
73. 8 Aa ey _ wees HEF Z BANK 3 CTL RA1 BANK 2 CTL RA2 ERROR LINE SK1 3 O ee po O1 KBD1 DAO KBD2 DA1 KBD3 DA2 KBD4 DA3 KBD5 DA4 KBD6 DA5 KBD7 DA6 KBD8 DA7 KBD9 0V q qQ OqQOQO QBN Ooa A O hp TO IC2 3 OF OTHER BANKS 2 SEGMENTS AON BON 12V TO DIGITS 3 1IN 78 7mm 4 OIN 101 6mm 238838 BERT REE 4 Fig 8 Component layout and full size underside copper foil master track pattern positions Follow with the d i l dual in line i c sockets and then continue in any convenient order Insert 1mm terminal pins at the external connection points but omit those alongside IC1 which are only needed if more than eight digits are to be controlled There are two choices of data input as said earlier They are connected to the board at the pins to the left of resistors R1 to R8 If using the data entry keypad connect its pins as shown in Fig 9 to the similarly numbered points on the board Keyboard Everyday Practical Electronics May 2002 Prototype display controller board during development testing using a plug in breadboard to temporarily connect a data keypad and a PC via a Centronics con nector mounted on the p c b used with Teach In 2000 Part 4 Feb 00 pin 9 is a ground OV connection for the pad s frame If using a PC as the data source it needs to be connected from its parallel printer port to the board The
74. 8 red l e d 8 off see text TR1 to TR3 BC548 or similar small signal npn transistor 3 off IC1 74HC138 or 74LS138 3 to 8 line decode Miscellaneous Materials for wind cups and vane see 15 excl hardware Approx Cost Guidance Only IC3a is configured as an oscillator with a period of one to three seconds controllable by preset VR1 a fixed resistor was used in the test model Its output is passed to IC3b via a pulse shaping C R capacitor resistor network formed by C2 and R6 This causes the output of IC3b to go low for a short peri od about 5ms when the input to C2 goes high this is the Write signal for DAC IC2 Everyday Practical Electronics May 2002 Prototype homemade anemometer assembly Similarly IC3c produces a short negative going pulse having a period set by C3 and R7 when the output of IC3b goes high This is inverted by IC3d and produces the Reset pulse for the counters ANEMOMETER MECHANICS The anemometer is constructed using three half ping pong balls to make the cups they can easily be cut using a hacksaw con nected to a central hub with short lengths of plastic as shown in Fig 7 23 Larger cups may be used if you require One suggestion is to use plastic scoops available with washing powder The basic rule for calculating how far the cups should be away from the hub is that the distance from the hub to the centre of the cup should be equal to the cup s diameter The hub is
75. 9V 12V 15V 2 6 25W 10 5W 4 3 78W 8W 12 5W 8 2W 5W 8 2W Quiescent current 80mA Input sensitivity for 8W output 4 ohm load 12V supply 70mV r m s gain 40 See single TDA2003 for details of absolute maximum ratings TO SPEAKER LS1 SCREENED INPUT LEAD 348 POWER SUPPLY VE POWER SUPPLY VE OV Everyday Practical Electronics May 2002 The printed circuit board component LM386 are usually referring to the N 1 on the p c b to act as an orientation layout wiring and copper foil master are version guide This should be followed by the lead detailed in Fig 12 Again combined or sep The TDA7052 is sometimes given the off solder pins and then the smallest com arate heatsinks must be fitted to the inte suffix A This indicates that the chip con ponents resistors working up to the grated circuit s metal tabs The p c b is tains a d c volume control and is not suit largest electrolytic capacitors and presets obtainable from the EPE PCB Service able for the circuit described here Finally the lead off wires including the code 348 Twin TDA22003 Some suppliers give the LM380 the suf screened input cable off board Volume fix 14 to indicate the 2 5W 14 pin ver control and loudspeaker should be attached HEATSINKS sion and the suffix 8 for the 8 pin to the p c b A large area metal heatsink is required 600mW alternative When ordering make On completion check the board for poor for t
76. A 4 yes set bit 4 low to discharge cap Note that it will be per again to ch alae Ico aa bef TRISA 4 set bit 4 as output PAGEO standard 7805 5V 1A type if additional nop brief wait discharge capacitor ies of IC2 IC3 PAGE added Bor oe bsf TRISA 4 set bit 4 as input chip adds about PAGEO 20mA to the power decfsz PULSECNTF _ repeat for set delay loop time drawn from the 5V goto PULSE2 return line see earlier QB programmers will recognise that the multiplexing circuit could be controlled directly from the PC s printer port data lines omitting the PIC entirely The port s other control lines could then be used in place of the RAO to RA2 connections The QB software would largely need to be rewritten of course VALEDICTUM DIGITALIS Two digits were sent to the author for experimentation As described in this arti cle the resulting design is intended to drive up to at least 24 digits and up to 64 with modification Obviously this ability has not been fully proved in practice However extensive bench tests and simulations have been made using the two digits and it is believed that the claims are valid If you find any aspect that does not justify this belief let the author know via EPE HQ NOT via the Chat Zone as messages post ed there may be overlooked The author hopes that readers will find ways in which the PIC and QB programs can be enhanced and write additional routines to suit their own n
77. Adobe Acrobat format Clear and simple layout Comprehensive subject range Professionally written Regular Supplements EVERYTHING YOU NEED TO GET STARTED AND GO FURTHER IN ELECTRONICS The revised CD ROM edition of the Modern Electronics Base Manual MEM contains practical easy to follow information on the following subjects Electronic Components and their Characteristics 16 sections from Resistors and Potentiometers to Crystals Crystal Modules and Resonators Circuits Using Passive Components 10 sections Power Supplies The Amateur Electronics Workshop The Uses of Semiconductors Digital Electronics 6 sections Operational Amplifiers Introduction to Physics including practical experiments Semiconductors 5 sections and Digital Instruments 3 sections There s nothing to beat the satisfaction of creating your own projects From basic principles like soldering and making printed circuit boards to the tools needed for circuit building the Modern Electronics Manual and its Supplements describe clearly with appropriate diagrams how to assemble a radio loudspeaker circuits amplifiers car projects a computer interface measuring instruments workshop equipment security systems medical and musical circuits etc The Base Manual describes 12 projects including a Theremin and a Simple TENS Unit Extensive tables on diodes transistors thyristors and triacs digital and linear i c s Should you come across a techn
78. Amex Diners Club or Switch minimum mastereara card order 5 Send your card number and card expiry date plus Switch Issue No with your order Everyday Practical Electronics May 2002 3 7 VIDEOS ON ELECTRONICS A range of videos selected by EPE and designed to provide instruc tion on electronics theory Each video gives a sound introduction and grounding in a specialised area of the subject The tapes make learning both easier and more enjoyable than pure textbook or magazine study They have proved particularly useful in schools colleges training departments and electronics clubs as well as to general hobbyists and those following distance learning courses etc BASICS VT201 to VT206 is a basic electronics course and is designed to be used as a complete series if required VT201 54 minutes Part One D C Circuits This video is an absolute must for the begin ner Series circuits parallel circuits Ohms law how to use the digital multimeter and much more Order Code VT201 VT202 62 minutes Part Two A C Circuits This is your next step in understanding the basics of electronics You will learn about how coils transformers capacitors etc are used in common circuits Order Code VT202 VT203 57 minutes Part Three Semicon ductors Gives you an exciting look into the world of semiconductors With basic semicon ductor theory Plus 15 different semiconduc tor devices explained Order Code VT203 VT204 56 minu
79. B7 are used by the soft ware to achieve handshaking with the PC when the unit is under computer control Pin RA4 is used in a manner possibly not seen by readers before It is used in oscillatory mode under software control and at a rate set by preset VR1 and capaci tor C5 It allows the segment control pulse width to be varied The controlling soft ware routine will be discussed towards the end of this article As usual with the author s PIC designs on board programming can be performed via a 4 pin connection TB1 Adverse Everyday Practical Electronics May 2002 effects on the 5V power line are prevent ed during programming control by the inclusion of resistor R9 and diode D1 POWER SUPPLY Power for the digits needs to be 12V d c This may be provided from any source capable of supplying at least 500mA to provide headroom when a segment is activated It does not need to be stabilised A 12V car battery is suitable The prototype was found to operate with a supply voltage as low as 9V with resul tant reduction in current consumption IC8 PIC16F84 PSEe TE 4 MCLR TO 4 x 4 MATRIX KEYPAD OR PC PARALLEL PORT DATA DA PINS O 1 lt ULN2004A but can be modified to control 64 digits RAO RA1 RA2 RA3 TOCKI RA4 DIO RB7 i Whilst the 13 5V or so of a fully charged battery seems acceptable it would appear to be unwise to allow the supply to significantly exceed this v
80. BOT VOICE EFFECT Make your voice sound similar to a robot or Darlek Great fun for discos school plays theatre productions radio stations amp playing jokes on your friends when answering the phone PCB 42x71mm 1131KT 8 95 AUDIO TO LIGHT MODULATOR Cortrols intensi ty of one or more lights in response to an audio input Safe modern opto coupler design Mains voltage experience required 3012KT 8 95 MUSIC BOX Activated by light Plays 8 Christmas songs and 5 other tunes 3104KT 7 95 20 SECOND VOICE RECORDER Uses non volatile memory no battery backup needed Record replay messages over amp over Playback as required to greet customers etc Volume control amp built in mic 6VDC PCB 50x73mm 3131KT 12 95 TRAIN SOUNDS 4 selectable sounds whistle blowing level crossing bell clickety clack amp 4 in sequence SGO1M 6 95 FACTOR PUBLICATIONS THE EXPERTS IN RARE amp UNUSUAL INFORMATION Full details of all X FACTOR PUBLICATIONS can be found in our catalogue N B Minimum order charge for reports and plans is 5 00 PLUS normal P amp P SUPER EAR LISTENING DEVICE Complete plans to build your own parabolic dish microphone Listen to distant voices and sounds through open windows and even walls Made from readily available parts R002 3 50 LOCKS How they work and how to pick them This fact filled report will teach you more about locks and the art of lock picking than many books we ha
81. CHINE The replacement washing machine is a famous brand renowned for its high quality and long life However after using it for the first time it became apparent that something that old faithful had was lacking in its suc cessor This was a lamp that came on when it had completed the washing The only way of knowing whether it has finished or not is to look closely at the pro gram switch or listen until the machine has not made a sound for some time Taking the washing out promptly is important if you wish to re load the machine or if you want to dry the laundry as quickly as possible A further point is that if the washing machine is situated in a garage or other place remote from the house even a warn ing light will be of little help You would have to visit it periodically to check whether it had finished its work LAUNDRY DONE The washing machine alarm circuit described here will give an audible signal in the form of high pitched bleeping when the washing cycle has finished If the machine has been left on a rinse hold 356 setting it will give a signal when the pro gram has reached this point This will prevent the user from forget ting about it and leaving the washing overnight in a machine filled with water Readers may find the circuit useful for other similar appliances and it has been tested successfully with tumble driers VIBRATION AUDIO LEVEL SENSOR AMPLIFIER DETECTOR INTEGRATOR H
82. E amp ON OFF ce FROM IC8 RB3 seament RBS Dag AO Rae SELECT lt RB6 A1 E FROM IC8 A2 RB7 l2 gads Ai DIGIT POWER CONTROL TO IC2 IC3 OF OTHER BANKS Fig 6 Circuit diagram for the multiplexed control of the digits basically for eight MICROCONTROLLER Because of the multiplexing arrange ment a PIC16F84 microcontroller is read ily suitable for this design see Fig 7 It is capable of being user controlled either via a 16 key 4 x 4 data entry keypad or via a PC compatible computer running under MS DOS or Win95 98 ME The PIC is run at 4MHZz as set by crys tal X1 Port pins RBO to RB2 control digit selection via ICI Fig 6 pins RB4 to RB6 control segment selection via IC4 and ICS RB7 controls selection of IC4 segment On control and RB3 controls selection of IC5 segment Off control Port pins RAO to RA2 perform bank selection As shown they can control up to three banks of eight digits If they are used to control another 74HC237 1 of 8 multiplexer however they could control eight banks with suitable software modification Port B pins are also used for inputting data from a 16 key keypad or from a PC Note that it is unwise to connect a keypad and PC simultaneously since one might adversely affect the other The PIC itself is protected against its Port B pins being undesirably affected by external PC key pad control by the inclusion of buffer resis tors R1 to R8 Pins RA3 and R
83. EE l Scottish Highlands l Po ees POSTCODE ictiwwiticawnedees UK Islands amp Eire 7 each i Europe EU 23 each l SIGNATURE eenaa nE eal ee EA E EA EA eee ae as Europe Non EU 23 each 30 each eae USA amp Canada 28 each 39 each l _ enclose cheque PO in UK pounds payable to Wimborne Publishing Ltd Far East Austalasia 35 each 43each _ Please charge my Visa Mastercard Amex Diners Club Switch Switch Issue No Rest of World 28 each 52each l Please allow four working days for UK delivery l l Card NO biccia s sasaran nnn AR a see ee wel ee ees Card Exp Date NOTE Surface mail can take over 10 weeks to some parts of l the world Each ESM weighs about 4kg when packed i baii ec pa pmi a i a epee ape a ia ai i a a pe y aaia a a inii ia San jaa hia ini aai mem cd GENT ELECTRONI C S Tel 01283 565435 Fax 546932 http Awww magenta2000 co uk E mail sales magenta2000 co uk LTD EE237 135 Hunter Street Burton on Trent Staffs DE14 2ST All Prices include V A T ADD 3 00 PER ORDER P amp P 6 99 next day MAIL ORDER ONLY e CALLERS BY APPOINTMENT EPE MICROCONTROLLER P I TREASURE HUNTER The latest MAGENTA DESIGN highly stable amp sensitive with I C control of all timing functions and advanced pulse separation techniques High stability drift cancelling e Easy to build amp use No ground effect works in seawater e Detec
84. ETURNS As we will see later noise may cause a comparator to switch multiple times as a threshold is crossed Furthermore offsets and other errors may shift the threshold level Last month we introduced the fact that there is noise that originates from within the components themselves We now move many applications we use sensors to 368 on to see that there is a variety of types of noise generated within electronic sensors and associated circuitry these are thermal noise shot noise flicker noise burst noise and avalanche noise We will have a quick look at each of them in turn THERMAL NOISE Thermal noise also known as Johnson noise is a fundamental property of resis tors including the internal resistances of sensors and semiconductor devices which results in a white noise voltage across its in circuit terminals This is a fundamental property of any resistor and therefore sets the lower limit of the noise from any sensor whatever we do we cannot get lower noise than the ther mal noise Thermal noise cannot be reduced by improved component manufacture However as it is temperature dependent reducing the temperature will reduce the noise Cooling sensors to very low temper atures may be appropriate for some situa tions such as physics experiments but in most cases it would be too difficult and expensive to be justifiable The thermal noise r m s voltage across a resistor is given by Vy rms
85. FFICIENT IN ELECTRICITY Comprehensive plans with loads of info on designing systems panels control electronics etc 7 Ref PV1 200 WATT INVERTERS plugs straight into your car cigarette lighter socket and is fitted with a 13A socket so you can run your mains operated devices from your car battery 49 95 Ref SS66 THE TRUTH MACHINE Tells if someone is lying by micro tremors in their voice battery operated works in general conversation and on the phone and TV as well 42 49 Ref TDS AIR RIFLES FROM LESS THAN 40 CROSSBOWS WIDE RANGE OF BB GUNS AMMO TARGETS PISTOLS REPLICA GUNS UZI MACHINE GUN REPLICAS BB REPEATERS LASER SIGHTS ELECTRIC BB GAS BB www airpistol co uk E a D ra INKJET CARTRIDGES FROM JUST 3 AT I www officebits co uk lt a EE ED INFRA RED FILM 6in square piece of flexible infra red film that will only allow IR light through Perfect for converting ordinary torches lights headlights etc to infra red output using only stan dard light bulbs Easily cut to shape 6in square 15 Ref IRF2 or a 12in square for 29 95 Ref IRF2A HYDROGEN FUEL CELLS Our new hydrogen fuel cells are 1V at up to 1A output hydrogen input easily driven from a small elec trolysis assembly or from a hydrogen source our demo model uses a solar panel with the output leads in a glass of salt water to produce the hydrogen Each cell is designed to be completely taken apart put back together and expan
86. Frequency Counter H P 1650B Logic Analyser 80 channel MARCONI 2035 Mod Meter 500kHz 2GHz RADIO COMMUNICATIONS TEST SETS MARCONI 2955 2995A ROHDE amp SCHWARZ CMT 0 1 1000MHz SCHLUMBERGER 4040 H P 6063B DC Electronic Load 3 240V 0 10A 250W H P 66312A PSU 0 20V 0 2A H P 66311B PSU 0 15V 0 3A H P 66309D PSU Dual 0 15 0 3A 0 12 0 1 5 H P 6632B PSU 0 20V 0 5A H P 6623A PSU triple output ranging from 0 7V 0 5A to 0 20V 0 4A H P AGILENT 34401A DMM 67 digit H P 3478A DMM 5 digit FLUKE 45 DMM dual display KEITHLEY 2010 DMM 71 2 digit KEITHLEY 617 Programmable Electrometer H P 4338B Millionmmeter RACAL Counter type 1999 2 6GHz H P Counter type 53131A 3GHz H P AGILENT 33120A Func Gen ARB 100uHz 15MH 900 1000 SONY TEKTRONIX AFG320 Arbitary Func Gen H P 8904A Syn Function Gen DC 600kHz 1000 1250 BLACK STAR JUPITOR 2010 Func Gen 0 2Hz 2MHz with frequency counter H P 8116A Pulse Generator 1mH 50MHz H P 8657B Syn Sig Gen 0 1 2080MHz CO AXIAL SWITCH 1 5GHz IEEE CABLES SPECTRUM ANALYSERS H P 8561B 50Hz 6 5GHz H P 8560A 50Hz 2 9GHz synthesised H P 8594E 9kHz 2 9GHz H P 8591E 1MHz 1 8GHz 75 Ohm H P 853A with 8559A 100kHz 21GHz H P 8558B with Main Frame 100kHz 1500MHz H P 3585A 20Hz 40MHz H P 3580A 5Hz 50kHz ADVANTEST R4131B 10kHz 3 5GHz EATON AILTECH 757 0 001 22GHz MARCONI 2382 100Hz 400Mkz high resolution MARCONI 2370 30Hz 110MHz H P 182 with 8557 10k
87. Hz 350MHz H P 141T SYSTEMS 8553 1kHz 110MHz 8554 500kHz 1250MHz 8555 10MHz 18GHz TEKTRONIX 491 10MHz 12 4GHz H P 8443 Tracking Gen Counter 110MHz H P 8444 OPT 059 B amp K 2033R Signal Analyser H P 5372A Frequency amp Time Interval Analyser H P 8754A Network Analyser 4MHz 1300MHz H P 3557A Network Analyser 5Hz 200MHz H P 53310A Mod Domain Analyser Opt 001 003 ONO SOKKI CF300 Portable FFT Analyser Used Equipment GUARANTEED Manuals supplied This is a VERY SMALL SAMPLE OF STOCK SAE or Telephone for lists Please check availability before ordering CARRIAGE all units 16 VAT to be added to Total of Goods and Carriage SQUIRES MODEL amp CRAFT TOOLS A COMPREHENSIVE RANGE OF MINIATURE HAND AND POWER TOOLS AND AN EXTENSIVE RANGE OF ELECTRONIC COMPONENTS FEATURED IN A FULLY ILLUSTRATED 528 PAGE MAIL ORDER CATALOGUE 2002 ISSUE SAME DAY DESPATCH FREE POST AND PACKAGING Catalogues FREE OF CHARGE to addresses in the UK Overseas CATALOGUE FREE postage at cost charged to credit card NEW SHOP EXTENSION OPENING SOON Squires 100 London Road Bognor Regis West Sussex PO21 1DD TEL 01243 842424 FAX 01243 842525 SHOP NOW OPEN Sy VISA 539 Constructional Project SIMPLE AUDIO CIRCUITS Part 1 Introduction and Power Amplifiers RAYMOND HAIGH A selection of pic n mix low cost audio circuits from preamplifier to speaker ATEVER their particular area of Wire
88. IC1 output goes low then TR3 conducts instead of TR1 and C2 is now triggered at pin 2 The monostable timer output goes high which supplies base cur rent to TR2 Current therefore passes through TR2 LS1 and TR3 to OV Thus two opposing transistors are switched alternately in order to supply high currents through LSI Exactly the same principle is often used to control the direc tion and speed of powerful d c motors and special driver chips are available for this Buffered Solution You asked how IC2 works as a buffer amplifier It is wired as a monostable sin gle shot timer with a short period Once triggered by ICI the monostable will start timing and it will ignore any more trigger signals until it times out However if a trig ger signal is present when the monostable tries to time out then a 555 will carry on timing until the trigger is removed when the output will go low at the same time A quick 555 breadboard experiment will demonstrate this build the monostable of Fig 4 briefly trigger it and watch the l e d time out automatically after a second or two Then keep it triggered for several sec onds the output will go low as soon as the trigger is removed Taking a brief look at the timing of the circuit in theory the on time of C2 is cal culated approximately by 1 1 R2 C4 which is llus If IC1 is said to run at 40kHz then by using frequency 1 t the period t of its output is 25us These figures do n
89. ION SENSING Consider a rotating disc marked with black and white sections above which an optical sensor has been placed see Fig 7 6 Assume that light is shining onto the disc so that when the sensor is above a white area we get a relatively large signal compared to when it is above a black area Fig 7 6 Optical sensing of motion The grey bar represents the fixed sensor mounting and the black dot indicates the location of the sensor The disc is free to rotate past the sensor Assume that this signal is passed through a suitable comparator circuit so that a clean digital output signal is obtained with O rep resenting a black area and 1 a white area As the disc rotates we will get an alternat ing 1 and O the frequency of this pulsed signal indicating the speed of rotation We are not restricted to rotary motion with this technique we can pattern a lin ear bar and measure movement in a similar way We can also use holes in the disc or bar or other object rather than black and white areas to switch the level of light falling on the sensor as movement occurs More sophisticated measurement of the disc s movement can be achieved by using more complex patterns on the disk and multiple sensors If we use several sensors and arrange the black and white areas appropriately we can provide a_ binary coded output that indicates the location angle of rotation of the disc Fig 7 7 pro vides an example of this using a 3 bit
90. M unused 12 FARNELL AMM255 Automatic Mo Meter 1 5MHz 2GHz unused 525 425 FARNELL DSG1 Low Frequency Syn Sig Gen distortion 0 001Hz 99 99kHz low TTL Square Pulse Outputs etc 95 FLUKE 8060A Handheld True RMS DMM 4 digit As new 150 used 95 BECKMAN HD110 Handheld 3 digit DMM 28 ranges with battery leads and carrying case 40 H P 3310A Function Gen Sine Sq Tri Ramp Pulse FARNELL LFM4 Sine Sq Oscillator 10Hz 1MHz low distortion TTL output Amplitude Meter 125 H P 545A Logic Probe with 546A Logic Pulser and 547A Current Tracer FLUKE 77 Multimeter 3 2 digit handheld FLUKE 77 Series 11 HEME 1000 L C D Clamp Meter 00 1000A in carrying case Racal 9008 ONLY Automatic Modulation Meter AM FM 1 5MHz 2GHz Datron 1061 High Quality 5 5 Digit Bench Multimeter True RMS 4 wire Res Current Converter IEEE Datron 1061A High Quality 6 digit Bench Multimeter True RMS 4 wire Current Converter Racal Receiver RA1772 50kHz 30MHz L E D Display Basically working 0 005Hz 5MHz 125 D MARCONI 2019A AM FM SYNTHESISED SIGNAL GENERATOR 80 kHz 1040MHz NOW ONLY MARCONI 893C AF Power Meter Sinad Measurement Unused 100 Used 60 MARCONI 893B No Sinad MARCONI 2610 True RMS Voltmeter Autoranging 5Hz 25MHz 19 GOULD J3B Sine Sq Osc 10Hz 100kHz low distortion 75 125 AVO 8 Mk 6 in Every Ready case with leads etc 80
91. NICS IN CONTROL Two colourful animated courses for students on one CD ROM These cover Key Stage 3 and GCSE syllabuses Key Stage 3 A pictorial look at the Electronics section featuring animations and video clips Provides an ideal introduction or revision guide including multi choice questions with feedback GCSE Aimed at the Electronics in many Design amp Technology courses it covers many sections of GCSE Electronics Provides an ideal revision guide with Homework Questions on each chapter Worked answers with an access code are provided on a special website Single User 29 inc VAT Multiple User 39 plus VAT Student copies available only with a multiple user copy 6 plus VAT UK and EU customers add VAT at 17 5 to plus VAT prices MODULAR CIRCUIT DESIGN Contains a range of tried and tested analogue and digital circuit modules together with the knowledge to use and interface them Thus allowing anyone with a basic understanding of circuit symbols to design and build their own projects Version 3 includes data and circuit modules for a range of popular PICs includes PICAXE circuits the system which enables a PIC to be programmed without a programmer and without removing it from the circuit Shows where to obtain free software downloads to enable BASIC programming Essential information for anyone undertaking GCSE or A level electronics or technology and for hobbyists who want to get to grips with project design Over
92. NTER PIN 5 REACHED LOGIC 1 END ROUTINE Fig 6 Measuring the resistance of the thermistor 318 t Fig 7 Output waveform b the piezo device used here has a very sharp resonance 1 e the sound output is very much higher at a specific frequency than at others Different devices have dif ferent resonances and even those tested of the same type had frequencies which var ied quite a bit By sweeping the frequency through the resonance one can be sure of making the most irritating noise In this design the frequency sweeps from approx imately 2kHz to 8kHz To make a PIC generate an oscillating signal is quite simple Referring to the waveform in Fig 7 you take the output high wait for a short time t take the output low wait for a short time t and then repeat the process The result is a square wave driving the piezo sounder If for instance we made tye 0 5ms the period would be 2 x ty 1 Oms and the sound would have a fre quency of 1kHz Sweeping the frequency may be accom plished by gradually changing the value of tye Which can be done using the fact that delays in microcontroller systems are often made by time waster loops where a counter counts down to zero By changing the value loaded into a reg ister in the first place the time taken can be varied Fig 8 shows the program segment responsible For each specific frequency eight cycles are generated The whole
93. Ne SHAFT PLASTIC OR METAL BOX GRAY CODED a E DISC Above Stripboard assembly mounting for the wind vane SENSORS SECTION OF PEN TUBE i F f STRIPBOARD GLUED TO BASE OF BOX Right Fig 7 27 Basic format for a suggested wind vane TO HOLD SHAFT assembly see text There are three points to note in this par ticular design 1 The outputs from the sensors are inverted by the transistors so that the black areas correspond to a logic 1 This may not be correct if you use different sensors 2 The disc in our design faced upwards when the sensor was completed thus mak ing everything occur in the opposite way If your disc faces down swap west for east north west for north east and south west for south east in Table 7 5 3 In our prototype we demonstrated the direction indicating principle using an l e d bargraph but if you choose to use individ ual l e d s instead we suggest you arrange them in a circle Most of the construction of the wind vane is the same as for the anemometer but using the Gray coded disc instead The vane itself is a horizontal length of alu minium or plastic rod to which is attached a vertical vane at one end and a counterbal ance weight at the other The photograph of a commercial vane should give you a good idea of the design Having completed construction the only thing left to do is use a compass to align north on the disc centre of the black black black area to magnetic nort
94. RED L E D s Hewlett Packard red I e d s 5V operation available in a pack of 50 for 8 Ref SS200 or 500 for 29 95 Ref SS201 MICROSOFT TRACKBALL AND MOUSE Called the Microsoft Ballpoint this has 4 buttons a trackball and PS2 connector Will work with most PCs 5 99 Ref EP50 MAXON WALKIE TALKIES up to 2 mile range UK legal 300 channel 2 x walkie talkies 74 95 Ref Maxon1 Chargers 14 Ref Maxonc battery packs 12 Ref Maxonb otherwise uses AAA batteries 2 WAY MIRROR KIT Contains enough material to make up to a 500mm x 2200mm mirror excl glass full instructions 19 95 Ref WFO001 22 AIR RIFLE Under lever type powerful Chinese training rifle 38 26 Ref A1047 500 pellets 2 68 Ref A1091 22 AIR RIFLE STANDARD TYPE Chinese training rifle on legal limit for air rifles 29 75 Ref A1040 Pellets 2 68 Ref A1091 SHUT THE BOX Check out www bullybeef co uk for a range of pub games and magic tricks WANT TO MAKE SOME MONEY STUCK FOR AN IDEA We have collated 140 business manuals that give you information on setting up different businesses you peruse these at your leisure using the text editor on your PC Also included is the certificate enabling you to reproduce and sell the manuals as much as you like 14 Ref EP74 ANICS CO2 GAS POWERED PISTOL Russian handheld pistol powered by Sparklets CO2 cylinders give approx 70 shots fires steel BB Pistol 58 22 Ref AGA101 tub of 1 500 BB sho
95. RING An affordable circuit which sweeps the incoming water supply with hc WATER variable frequency electromagnetic DESCALEA signals May reduce scale formation a dissolve existing scale and improve lathering ability by altering the way salts in the water behave Kit includes case P C B coupling coil and all components High coil current ensures maximum effect L E D monitor KIT 868 22 95 MICRO PEsT SCARER Our latest design The ultimate scarer for the garden Uses special microchip to give random delay and pulse time Easy to build reliable circuit Keeps pets pests away from newly sown areas play areas etc uses power source from 9 to 24 volts e RANDOM PULSES e HIGH POWER e DUAL OPTION POWER UNIT 3 99 Plug in power supply 4 99 KIT O6 tee rete a ee wee ees 19 99 KIT SLAVE UNIT 0 00000e 32 50 WINDICATOR A novel wind speed indicator with LED readout Kit comes complete with sensor cups and weatherproof sensing head Mains power unit 5 99 extra DUAL OUTPUT TENS UNIT As featured in March 97 issue Magenta have prepared a FULL KIT for this excellent new project All components PCB hardware and electrodes are included Designed for simple assembly and testing and providing high level dual output drive KIT 866 Full kit including four electrodes 32 90 1000V amp 500V INSULATION TESTER Superb new design Regulated output efficient circ
96. S Barry Fox highlights technology s leading edge 322 Plus everyday news from the world of electronics BACK ISSUES Did you miss these Many now on CD ROM 350 READOUT John Becker addresses general points arising 353 CD ROMS FOR ELECTRONICS 364 A wide range of CD ROMs for hobbyists students and engineers SHOPTALK with David Barrington 367 The essential guide to component buying for EPE projects ELECTRONIC VIDEOS Our range of educational videos 378 PRINTED CIRCUIT BOARD AND SOFTWARE SERVICE 379 PCBs for EPE projects Plus EPE software DIRECT BOOK SERVICE 380 A wide range of technical books available by mail order ADVERTISERS INDEX 384 Readers Services Editorial and Advertisement Departments 315 305 Visit our website www distel co uk GIANT 10 7 SEGMENT DISPLAYS A bulk purchase enables us to bring to you these GIANT 7 segment digital displays at a now affordable price The 10 character size gives exceptional read ability at long distances and enables a host of applica tions including score boards digital clocks coun ters event timers etc As the units are a simple electromechanical device and operate from 12V DC simple switching via switches relays PIC or PC may be used to control single or multiple digits Units feature integral Zero Power memory which greatly simplifies desgn For an excellent DIY practical article see the May issue of Everyday Practical Electronics magazine Ideal School Colle
97. Solar Powered Rain Alarm Everyday Practical Electronics Wimborne Publishing Ltd 408 Wimborne Road L E D Super Torches Red Main X Digitimer Main Board R F Board Perpetual Projects Uniboard 2 East Ferndown Dorset BH22 9ND Tel 01202 873872 Fax 01202 874562 Display Red E mail orders epemag wimborne co uk On line Shop www epemag _ White L E D wimborne co uk shopdoor htm Cheques should be crossed and made payable to X Sync Clock Driver Everyday Practical Electronics Payment in sterling only Water Monitor NOTE While 95 of our boards are held in stock and are dispatched within Camcorder Power Supply OCT 01 318 5 94 seven days of receipt of order please allow a maximum of 28 days for delivery PIC Toolkit Mk3 319 8 24 overseas readers allow extra if ordered by surface mail Perpetual Projects Uniboard 4 Gate Sentinel Solar 305 3 00 Back numbers or photostats of articles are available if required see the Back powered Bird Scarer and Solar Powered Register Issues page for details Teach In 2002 Power Supply Please check price and availability in the latest issue Lights Needed Alert Boards can only be supplied on a payment with order basis Pitch Switch Capacitance Meter Main Board double sided PROJECT TITLE Order Code Display Board double sided Vibralarm NOV 99 230 6 93 K K PIC Toolkit TK3 Software onl Demister One Shot 245 6 78 4 Channel Tw
98. Spectrum Analyser What he says about the lack of anti aliasing filters and the problems with signals greater in frequency than half the sampling rate Nyquist frequency causing aliasing of the signals is absolutely correct It has been accepted as a fact that in signal analysis it is not possible to retrieve signals which are greater than half of the sampling fre quency This premise is clearly stated in all textbooks on this subject as the Nyquist Criteria or as Shannon s Sampling Theory For example with a sampling frequency of 2kHz it is not possible to retrieve signals in excess of 1kHz Any frequencies greater than this 1kHz value will appear as a false or aliased signal and a considerable amount of research and commercial activity has emerged to eliminate such signals by filtering them out from the signal presentation However it has now been proved through a research program undertaken by myself and Dr R F McLean that the above premise is false and that the limitation of the Nyquist Criteria can easily be overcome A theoretical study along with a simple capturing device has been developed which can retrieve signals in excess of 2000 times this hitherto limitation in frequency The system also dispenses with the need for any form of filtering of the incoming signal For example by sampling at no greater than 2kHz frequencies of up to 2 4GHz are unambiguously retrievable PIC MINI ENIGMA Dear EPE The M
99. TIAL nfreq VALUES time MAKE OUTPUT HIGH nfreq REDUCED BY 1 RELOAD nfreq MAKE OUTPUT LOW nfreq REDUCED BY 1 TIMES LOOP REDUCED BY 1 nfreq RELOADED nfreq REDUCED BY 1 YES END ROUTINE Fig 8 Flowchart for the piezo sweeper The whole sequence takes approxi mately 130ms Everyday Practical Electronics May 2002 This may not seem very long but what TESTING matters in conserving power is the ratio of The circuie will the time taken to run the measurements work quite happily at compared and the time remaining asleep room temperature If for instance it takes 50ms to take the Once ihe batieties are measurements the circuit is asleep for 98 connected it seems to per cent of the time with a resulting work well on 6V extension of battery life ae The OPTION register has eight bits ea a which must be set up in order to control the recommended WDT and prescaler The functions are Gently rotate pre shown in Table 2 For this application the set VPE wati the SR eneen OPTION register must be set to contain the fhreshold is found NEE N NE N binary byte 11001111 The short main between the alarm e00 00000000000000 program section is shown in Fig 9 yg A o Be eae bleating or not Set it Efe o 00 0Q 000000008 Note that during a Sleep period the acy dat me Alois SORES G Ee CEES Cle000 0QM 000000000 I O ports maintain the same conditions that they had immediately beforehand T a Ther
100. V VCR remote control unit to switch onboard 12V 1A relay on off 3058KT 10 95 SPEED CONTROLLER for any common DC motor up to 100V 5A Pulse width modulation gives maximum torque at all speeds 5 15VDC Box provided 3067KT 12 95 3 x 8 CHANNEL IR RELAY BOARD Control eight 12V 1A relays by Infra Red IR remote control over a 20m range in sunlight 6 relays turn on only the other 2 toggle on off 3 oper ation ranges determined by jumpers Transmitter case amp all components provided Receiver PCB 76x89mm 3072KT 52 95 PRODUCT FEATURE COMPUTER TEMPERATURE DATA LOGGER PC serial port controlled 4 channel temperature meter either deg C or F Requires no external power Allows continuous temperature data logging of up to four temperature sensors located 200m from motherboard PC Ideal use for old 386 486 comput ers Users can tailor input data stream to suit their purpose dump it to a spreadsheet or write your own BASIC programs using the INPUT command to grab the readings PCB just 38mm x 38mm Sensors con nect via four 3 pin headers 4 header cables supplied but only one DS18S20 sensor Kit software available free from our website ORDERING 3145KT 23 95 kit form AS3145 29 95 assembled Additional DS18S20 sensors 4 95 each SOUND EFFECTS GENERATOR Easy to build Create an almost infinite variety of interesting unusu al sound effects from birds chirping to sirens 9VDC PCB 54x85mm 1045KT 8 95 RO
101. Vol 31 No 5 w D ie ae ie 7 Copyright 2001 2002 Wimborne Publishing Ltd 408 Wimborne Road East Ferndown Dorset BH22 9ND UK and Maxfield amp Montrose Interactive Inc PO Box 857 Madison Alabama 35758 USA All rights reserved WARNING The materials and works contained within EPE Online which are made available by Wimborne Publishing Ltd and Maxfield amp Montrose Interactive Inc are copyrighted You are permitted to make a backup copy of the downloaded file and one 1 hard copy of such materials and works for your personal use International copyright laws however prohibit any further copying or reproduction of such materials and works or any republication of any kind Maxfield amp Montrose Interactive Inc and Wimborne Publishing Ltd have used their best efforts in preparing these materials and works However Maxfield amp Montrose Interactive Inc and Wimborne Publishing Ltd make no warranties of any kind expressed or implied with regard to the documentation or data contained herein and specifically disclaim without limitation any implied warranties of merchantability and fitness for a particular purpose Because of possible variances in the quality and condition of materials and workmanship used by readers EPE Online its publishers and agents disclaim any responsibility for the safe and proper functioning of reader constructed projects based on or from information published in th
102. a room or we may be using it in a more complex way for example to control the environment of an enclosure This may require sophisticated manipu lation of the sensor data using a microcon troller or PC In other cases we do not need to know the value measured by the sensor but simply have to switch an output when the level crosses a preset threshold e g to switch on lights at night COMPARABLE Such applications often require com parators which will form one of the topics of our discussion this month The sensor comparator combination provides a digital signal which has uses beyond that of the simple level switching just mentioned and provides a means of measuring quanti ties other than those directly detected by the sensor The most common use of this approach is in motion sensing e g position direc tion and speed and the sensors most com monly used are optical sensors hence the phrase Digital Optical Sensing in this part s sub title Although magnetic sensors are also used in this way digital optical sensing is Our main sensor topic this month and we will be building wind speed and direction instruments You may be thinking that digital sensing and use of comparators rather than accurate amplification and measurement of a sensor signal means that we can relax and forget about the nasty problems of noise and errors that we have discussed in the last few parts Unfortunately this is not the case NOISE R
103. ady been argued but individual con structors will of course decide whether or not it will meet their needs 347 VAVN VA COMPONENTS TWIN TDA2003 POWER AMP See ge SHOP TALK Resistors 10Q 2 off 4702 All 0 25W 5 carbon film P 9 Potentiometers VR1 10k rotary carbon Capacitors Ci C2 C9 4u7 radial elect 50V 3 off 100n disc ceramic 2 off 22u radial elect 50V 100n polyester 2 off 10u radial elect 50V 220u radial elect 50V C3 C8 Semiconductor IC1 IC2 TDA2003 audio power amp i c 2 off SCREEN Miscellaneous LS1 2 to 8 ohm loudspeaker see text Printed circuit board available from the F 10 11 ab ove EPE PCB Service code 348 TDA2003 Circuit diagram case optional size and type to choice for the Twin heatsink see text audio screened cable TDA2003 Power multistrand connecting wire solder pins Amplifier Approx Cost c1 4 Guidance Only excluding case amp speaker Fig 12 below Component layout off board inter wiring and full size copper foil master for the Twin TDA2003 Amp You will need a heatsink for these devices Twin TDA2003 Amplifier circuit board component layout TOV TMORHISV Q ah C10 C8 100n oo IC1 TDA2003 2 c9 Co 4u7 O OV TWO TDA2003 BRIDGE CONFIGURATION POWER AMP R M S power output just before the onset of waveform clipping Speaker Supply Voltage Impedance Ohms
104. al big digits These had previ ously graced the platforms of British Rail as 6 digit 7 segment clocks Yes they were the familiar click click digits that surely any would be passenger has watched mesmerised while waiting for that where IS it train to arrive In the course of conversation the question of EPE designing a suitable electronic inter face for these digits came up Would Tech Ed be interested Certainly was the author s timely response to a novel design idea DISPLAY RESULTS The resulting basic design is capable of driving from one to eight digits with expansion up to 64 digits possible as dis cussed later They can be controlled via a standard 4 x 4 data entry keypad or via a PC compatible computer running under MS DOS or Win95 98 ME A PIC16F84 microcontroller is the con trolling device between the PC or keypad and the multiplexed digits The PC soft ware is written in QBasic QuickBASIC but can be run as a standalone program with out the need for QB to be installed The digits are ideal for use in any situa tion that requires a large electronically controlled display where the data is to be input intermittently Applications that Everyday Practical Electronics May 2002 come to mind are sporting scoreboards ticket draw results display of outdoor tem perature in public arenas well you ve seen where large digits can be used think up your own applications MONSTERS S
105. al block TB1 Place the p c b and battery holder on the bottom of the box to find their best positions If the unit is to be wall mounted remember to allow space for the holes which will be used to attach it Mark through the holes for the various parts also mark positions for on off switch S1 and the 35mm mono jack socket which is used for sensor MIC1 connection Measure the buzzer position and drill a hole in the lid directly above this If the buzzer is to be mounted remotely mark the position for a further socket say a small power in or a 2 5mm mono jack type for this to be connected Remove all these parts drill the holes and attach them Use plastic stand off insu lators for p c b mounting to bring the buzzer up to level of the hole in the lid Everyday Practical Electronics May 2002 2 95 in 75mm x 1 88 in 48mm Fig 3 Printed circuit board component layout full size copper foil master and wiring to off board components Refer to Fig 3 and complete the wiring using light duty stranded connecting wire If buzzer WD1 is mounted remotely con nect the buzzer pads on the p c b to the buzzer output socket taking account of the polarity SITING THE UNIT Decide on a suitable position for the main unit This should be placed fairly close to the washing machine say within 4 metres Make the sensor connection using light duty single screened wire micro phone cable This is be
106. alised in that pins are set up either as outputs or inputs We then have to measure the charging times of the capacitor first for the preset resistor VRI then for the thermistor R1 In order to give a reasonable number of steps to do the counting and improve the range of accuracy of the measurement two registers are used together to form a 16 bit value The technique used for measuring resis tance is shown in Fig 6 and involves the following 1 First the capacitor needs to be com pletely discharged To do this pin 5 is set as an output and then set at logic O zero volts This effectively shorts the capacitor A delay of approximately 5ms makes sure it is fully discharged 2 Next the two registers used to store the count time for the thermistor are set to zero 3 Then pin 6 is set as an output and reset to logic 0 Pin 5 is swapped to being an input pin and then pin 6 taken to logic 1 At this moment the capacitor begins to charge up 4 The program now starts to loop incre menting the counter registers as it goes Each time around the loop pin 5 is checked for having reached the voltage threshold at which it is considered to be at logic 1 5 As soon as this happens the routine ends and the counter registers then con tain the final time count This process is repeated for the variable resistor VR1 using a different set of counter registers and pin 7 instead of pin 6 After both measurements have been made the
107. ally common It was found that there were many options available if a source current of no more than 100mA were required especial ly as the current would be pulsed intermit tently However the requirement for at least 280mA presented a seemingly unsolvable problem unless discrete tran sistors were used which the author was determined not to resort to Quite simply no ideal i c devices could be found Briefly power op amps such as the L272 dual device seemed a possible solu tion but that was not deemed tidy Eventually it was decided to accept a less than optimum option to use an L293DN quadruple Half H driver This has four devices that can each be set to sink or source a current of up to 1A ata voltage from 4 5V to 36V It also has two enable inputs which allow pairs of drivers to have their outputs placed into a high imped ance state see Fig 4 Additionally it too has in built diode protection The device is intended for reversible motor and solenoid control The term Half H refers to the bridge configuration in which the pairs of drivers can be operated It seemed suitable for this application since no other appropriate device format could be found Consequently two L293DN devices are used in the main circuit each providing power for four multiplexed digits They are under combined control of another 74HC237 1 of 8 controller The L293DN however has the unfortunate side effect of consuming around
108. amplified computer speakers will provide a true 100W or more output if you don t believe me just take a look at the output avail able from the plug top power supply they normally use and ask yourself if you can get 100W output with less than 10W 12V 800mA input Nice trick if you could really do it It is of course all a marketing con trick AVAILABILITY Copies of EPE are available on subscription anywhere in the world see below from all UK newsagents distributed by COMAG and from the following electronic component retailers Omni Electronics and Yebo Electronics S Africa EPE can also be pur chased from retail magazine outlets around the world An Internet on line version can be purchased and downloaded for just 9 99 US approx 7 70 per year available from www epemag com Kiet fers tener re Everyday Practical Electronics May 2002 SUBSCRIPTIONS Subscriptions for delivery direct to any address in the UK 6 months 15 12 months 28 50 two years 52 Overseas 6 months 18 standard air service or 27 express airmail 12 months 34 50 standard air service or 52 express airmail 24 months 64 standard air service or 99 express airmail Online subscriptions for downloading the magazine via the Internet 9 99 US approx 7 70 for one year available from www epemag com Cheques or bank drafts in sterling only payable to Everyday Practical Electronics and sent to EPE Subs Dept Wimbor
109. an accurate timing within the software A 70ms pulse length is generated with preset VR1 at a roughly midway setting The maximum pulse length that can be set is about twice that These figures are based on the PIC being run at 4MHz Once you have ascertained the correct response of the segments using a long pulse set via VR1 it is worth experiment ing to find the lowest VR1 setting at which the segments will respond This will speed the rate at which the displays can be changed The digits will not respond if the resis tance is set too low An intermediate stage may also be found in which some digits respond but not others Avoid setting VR1 to a nil resistance position which will over load RA4 when it is in output low mode the PIC is internally protected against brief overloads but do not sustain this condition It is worth noting that the software has also been written to speed segment changing The status of each segment is recorded in the PIC s memory When a new character is to be displayed on a particular digit the digit s current segment status is checked against the segment requirement for the new character If any segments match they are ignored by the output rou tine so saving one pulse duration which can be a significant saving when many digits are in use SCHMITT PULSING This now brings us to a software hard ware aspect that has not been used before in an EPE project analogue control of fre
110. aneous LS1 4 to 32 ohm loudspeaker see text Printed circuit board available from the EPE PCB Service code 347 TDA2003 case optional size and type to choice heatsink see text audio screened cable multistrand connecting wire solder pins 11 Approx Cost Guidance Only excluding case amp speaker frequency response is set by capacitor C5 in conjunction with resistor R1 The response can be extended by reducing the value of C5 Supply line ripple rejection is afforded by capacitor C6 The outputs which can be delivered at various supply voltages are tabulated in the accompanying table The current drawn from a 15V supply when 4W are dissipat ed into a 4 ohm load is around 500mA The 2 ohm load is obtained by connecting two 4 ohm speakers in parallel At these power levels the device must of course be connected to an adequate heatsink and this is discussed later The printed circuit board component layout wiring and full size copper foil master pattern for the single chip TDA2003 amplifier are shown in Fig 10 This board is available from the EPE PCB Service code 347 TDA2003 TWIN TDA2003 AMPLIFIER A circuit diagram using two TDA2003 chips in a bridge configuration is shown in Fig 11 together with a general perfor mance guide Drawing around 1 7A from a 15V sup ply this combination will deliver a clean 12 5W into a 4 ohm load The case for this being adequate for domestic listening has alre
111. apability of 2Mbytes Microchip has also released a low cost in circuit debugger and programmer The PC based MPLAB ICD 2 supports the PIC16F and PIC18F devices As new devices become available users will be able to download new software into MPLAB ICD 2 at no cost creating a highly adaptable tool MPLAB ICD2 is available as a stand alone unit or as an evaluation kit that includes a demonstration board and samples of the 18F452 and 16F877 The board features a 2 x 16 l c d temperature sensor EEPROM memory I e d s piezo sounder and RS232 interface For more information browse www microchip com FARNELL COMBATS OBSOLESCENCE COMPONENT distributors Farnell have launched Product Watch an obsolescence service which gives customers advance notice of when components are about to become obsolete and of any end of line and end of stock items It sounds an excellent innovation Few of us can claim to have never been afflicted by designing a circuit whose components become obsolete or no longer attainable on the day the design is completed For more information email Farnell at productwatch farnell com 322 WCN SUPPLIES CAT THE 32 page catalogue from WCN Supplies is another that enterprising hobby ists should have in their library Component categories run from audio batteries cables chargers and connectors through the alpha bet via models including some delightful ones from Humbro motors passive c
112. arm The inverters give an audible warning signal when the battery voltage is lower than 10 5V 21V for the 24V version The inverter automatically shuts off when the battery voltage drops below 10V 20V for the 24V version Fuse protected input circuitry C A COMPLETE RANGE OF A Complete range of regulated inverters to power 220V and 240V AC B q INVE RTE R S equipment via a car lorry or boat battery Due to their high performance Order Code Power Voltage Price ace 651 581 150W Continuous 12V 36 39 651 578 150W Continuous 24V 36 39 651 582 300W Continuous 12V 50 64 651 585 300W Continuous 24V 50 64 651 583 600W Continuous 12V 101 59 651 593 600W Continuous 24V 101 59 651 587 1000W Continuous 12V 177 18 651 597 1000W Continuous 24V 177 18 651 602 1500W Continuous 12V 314 52 651 605 1500W Continuous 24V 314 52 651 589 2500W Continuous 12V 490 54 651 599 2500W Continuous 24V 490 54 CUS AATION SHOWN IS 651 583 600W VERSION Many uses include Fetes Fairgrounds Airshows Picnics ae EL ee ee Ee E ae Camping Caravans Boats Carnivals Field Research and Amateur ETC PRICES ARE INCLUSIVE OF V A T SALES COUNTER VISA Radio field days Powering Desktop amp Notepad Computers AND ACCESS ACCEPTED BY POST PHONE OR FAX OR EMAIL E ad US AT SALES BKELEC COM ALTERNATIVELY SEND CHEQUE a ng pecan O OR POSTAL ORDERS MADE PAYABLE TO BK ELECTRONICS JEJ B K ELECTRONICS aaa For Fu
113. ary carbon log Capacitors C1 4u7 radial elect 50V C2 C5 220u radial elect 50V 2 off C3 C6 100n disc ceramic 2 off C4 10u radial elect 50V Semiconductor IC1 LM380N audio power amp i c Miscellaneous LS1 4 to 32 ohm loudspeaker see text Printed circuit board available from the EPE PCB Service code 346 LM380N case optional size and type to choice 14 pin d i l socket heatsink see text multistrand connecting wire audio screened cable solder pins solder etc excluding case amp speaker Approx Cost Guidance Only is applied to the inverting input pin 6 and to avoid instability the non inverting input pin 2 is grounded OV The manufacturers quote a minimum supply voltage of 10V The sample test ed worked with a 9V supply but perfor mance became erratic at lower voltages Quiescent current although modest is double that of the other low power devices and this together with the higher operating voltage makes the i c more suitable for mains powered equipment CIRCUIT BOARD Details of the printed circuit board component layout wiring and copper foil master are given in Fig 8 This board is also available from the EPE PCB Service code 346 LM380N Although the board has been kept small as much copper as possible has been retained to afford some heatsinking DZO AMPLIFIER Produced by SGS Thomson the TDA2003 low cost 1 c is mainly for use in car radios Al
114. associated character correctly the last character in the above list cause the degrees symbol to be dis played when the is pressed as in 20 C The one before it is for the space bar turns off all segments in a digit You will see instances where the charac ter may be in upper or lower case and in some cases both If the value following the character contains one or more 1 s the equivalent character can be generated on a 7 segment display In the other cases all zeros the character cannot be formed using a 7 segment display If a character is not included in the table a value of zero is returned if its key is pressed All unacceptable keypresses are ignored ALLOCATING SEGMENTS For such unacceptable keys however a segment or PIC control code can be allocat ed separately For instance the program allo cates the code 00000001 when the lt ENTER gt key ASCII 13 is pressed The PIC has been programed to recognise this bit combination as the command to reset the digit number count to Digit 1 in a similar way to that in which it responds when the D key on the 4 x 4 data keypad is pressed You could for example allocate specif ic codes for the PC s forwards backwards cursor keys The PIC could then be told to step the digit count value backwards or forwards without causing the display data to change Then on pressing another key its character would be displayed at the new
115. ate division ratio 111 for WDT ratio of 1 128 same that the device has at its operating e threshold c An important design consideration concerns the value of the capacitor C1 Once the resistance of the appropriate sen sor is known the variable preset resistor needs to have the same value However the counter which waits for the capacitor to charge to its threshold must not overflow This will happen after 320ms with this design s value for C1 Therefore ensure that C u F x R kQ lt 320ms d The circuit is remarkably accurate and stable Because of the timing method of comparing the two resistors any changes in the supply voltage within the parame ters above or changes in the capacitance value caused by temperature or ageing have virtually no effect ACKNOWLEDGEMENTS The author expresses his thanks to Mrs Jan Edwards for her help in this project 319 New fechnology Update With a growing awareness of global warming scientists are looking at ways of using dye molecules to produce more efficient solar cells reports lan Poole olar cells might seem to be an ideal way of generating electricity They convert the plentiful supply of sunlight that is freely available in many areas of the world into useful electricity Whilst this may seem to be an excellent idea in theory reality has been quite differ ent and very few solar cells are used The main reason for this is that a large area needs
116. attached to a length of plastic or aluminium rod which passes through the barrel of an old felt pen If the hub is made of plastic then it should ride on the pen with little friction The pen is attached to a box which contains the disc and electron ics The bottom of the shaft should reach the base of the box and Everyday Practical Electronics May 2002 IC2 TLC7524 PLAN VIEW HALF A PING PONG BALL ee OEDIEEET PEN TUBE aS SHAFT PLASTIC OR METAL BOX lt SEGMENT CODED DISC SENSORS SECTION OF PEN TUBE GLUED TO BASE OF BOX SIE Sia alo TO HOLD SHAFT Fig 7 23 Basic format for a suggested anemometer assembly see text 315 Mounting of the sensor in the prototype anemometer a short length of pen tube is used to stop the shaft from moving sideways The encoded disc is secured to the shaft at a position a couple of millimetres away from the top of the sensor You should note that the design is very crude and many modifications can be made For example using a ball race as the top bearing to ensure that the friction is low and the shaft is secured in our design the cup assembly can simply be lifted off the rest SENSOR DISK Since the sensor is a reflective type we can use a black and white disc such as that in Fig 7 10 We suggest you get an enlarged photocopy of the disc and paste it onto a piece of stiff card The sensor needs to be within a few millimetres of the surface of the disc
117. available from RS including the IL300 which may be worth investigating A practical example of a low cost ana logue isolator is shown in Fig l while Fig 2 shows a suggested precision ana logue isolation amplifier Low noise and shielding techniques using BNC and tri axial connectors are also covered in Teach In 2002 and may be helpful in applications like these The Agilent data sheet contains more practical circuits and detailed theory Thanks for letting us know ARW Dog and Cat Scarer An interesting circuit recently appeared in our readers circuits feature Ingenuity Unlimited March 2002 p163 The Dog and Cat Scarer prompted a letter from reader Martin Stubbs who emails A device such as the Dog and Cat Scarer would be extremely useful to us as we enjoy walking particularly on holiday as last year we were harassed by dogs in Greece I am intrigued to know how the two 555 timers used in the circuit work I cannot determine how IC is set up as an oscilla tor or IC2 as a buffer amplifier Perhaps Circuit Surgery could dedicate a few lines of explanation as to how it works Referring back to the March MVU first of all an unfortunate error crept into the cir cuit diagram note that the connections to pin 2 and pin 3 of IC2 should be reversed The circuit s operation then makes a whole lot more sense We also stated that it should NOT be relied upon as a defence against aggressive dogs First IC1 is configured
118. be integrated almost as a library file It is suggested that 1 c d control is basi cally via Port B with the exception of the l c d E line which is better suited to con trol by the otherwise unused pin RA3 it is only used when under PC control Line E cannot be satisfactorily con trolled by Port B as all pins are in use for other purposes which would cause unde sirable I c d response It is only Line E that is critical in this context COMPUTER CONTROL When under computer control data is fed to the PIC via the same connections as Everyday Practical Electronics May 2002 the keypad but preferably in the keypad s absence It is in a different coding format to that used with the keypad however Because of the full range of keys on a PC keyboard is it is possible to send a much greater variety of data to the digits On recognition by the PIC that a PC is con nected to it see earlier it goes into a dif ferent monitoring routine COMPROG Synchronisation between the PIC and PC is maintained by using two handshake lines at the PIC end of the system pins RA3 and RA7 as mentioned earlier Port B pull up resistors are turned off in this mode The first significant handshake action the PIC takes following switch on for PC mode is to set pin RA3 high This indi cates to the PC that the PIC is ready to receive data The PIC then sits in a holding loop until acknowledgement from the PC is received The PC
119. cause ordinary wire could pick up stray mains hum and could result in the injection of unwanted signals into the circuit It is possible that this could hold off the warning in the absence of any vibration When connecting the jack plug to the sensor wire solder the outer sleeve terminal to the screening Mount the microphone insert inside a small plastic box a potting box was used in the prototype To do this drill a hole to make a push fit for the microphone insert Secure it using a little quick setting adhesive Drill a further hole in the side of the box for the connecting wire to pass through Pass the wire through the hole and allow ing a little slack apply a tight cable tie to provide strain relief Twist and sleeve some of the screening braid and solder the wires to the microphone pads The pad which is connected to the metal case of the microphone should be the one which is connected to the screening If the buzzer is to be mounted remotely the connecting wire may be of any conve nient length and be of any light duty stranded twin type FINAL TESTS With the main unit in position route the screened sensor wire between it and the washing machine and plug it in Make some tests with the sensor in various posi tions observing the l e d A suitable place should be found where the drumming nois es of the washing machine case cause the le d to flash brightly When satisfied about this make further adjustme
120. ch has a Rubidium frequency source as its reference and has an accuracy of one part in 10 The primary virtue of this design is its phenomenal accuracy and stability There will not usually be many really accurate standards of any kind in the workshop of a home constructor since they are usually prohibitively expensive This design provides an exception to this rule by bringing a national frequency standard right onto the amateur s bench It should prove useful for checking and adjusting the calibration of frequency meters oscilloscopes and any other equipment used for measuring or generating frequency of any kind DON T MISS AN ISSUE PLACE YOUR ORDER NOW Demand is bound to be high JUNE 2002 ISSUE ON SALE THURSDAY MAY 9 Everyday Practical Electronics May 2002 307 Established 1990 uasaR ELECTRONICS LIMITED PO Box 6935 BISHOPS STORTFORD Herts CM23 4WP TEL 01279 467799 FAX 07092 203496 ADD 2 00 P amp P to all orders or 1st Class Recorded 4 Next day Insured 250 7 Europe 5 00 Rest of World 10 00 We accept all major credit cards Make cheques PO s payable to Quasar Electronics Prices include 17 5 VAT MAIL ORDER ONLY FREE CATALOGUE with order or send 2 x 1st class stamps refundable for details of over 150 kits amp publications SR WWW QuasarElectronics comnm PROJECT KITS Our electronic kits are supplie
121. chnician or keen amateur who has previously worked with audio circuits The princi ples and practices of digital audio owe little or nothing to the traditional linear circuits of the past and are much more comprehensible to today s computer engineer than the older generation of audio engineers This book is intended to bridge the gap of understand ing for the technician and enthusiast The principles and methods are explained but the mathematical background and theory is avoided other than to state the end product 128 pages Order code PC102 8 95 PROJECTS FOR THE ELECTRIC GUITAR J Chatwin This book is for anyone interested in the electric gui tar It explains how the electronic functions of the instrument work together and includes information on BOOK ORDERING DETAILS All prices include UK postage For postage to Europe air and the rest of the world surface please add 1 per book For the rest of the world airmail add 2 per book Send a PO cheque international money order sterling only made payable to Direct Book Service or card details Visa Mastercard Amex Diners Club or Switch to DIRECT BOOK SERVICE WIMBORNE PUBLISHING LIMITED 408 WIMBORNE ROAD EAST FERNDOWN DORSET BH22 9ND Books are normally sent within seven days of receipt of order but please allow 28 days for delivery more for overseas orders Please check price and availability see latest issue of Everyday Practical Electronics before order
122. cien cy of these devices considerably even if the dye layer is made very thin Initially effi ciency levels of only 0 01 were achieved and this is far less than that achieved by the traditional semiconductor techniques To overcome this problem a new approach was adopted by the Swiss Federal Institute of Technology Using their method they believe the new cells will offer the possibili ty of a significant reduction in the cost of solar generated electricity due to the very simple construction of the cell In the new cell light absorption occurs in what is termed a mono layer of dye This is adsorbed chemically at the surface of a semiconductor forming a layer that is only lum thick Instead of using one continuous 320 layer the new cell uses small particles that are held in a colloidal solution When the dye is excited by a photon of light the dye is able to transfer an electron to the semiconductor If an external circuit is connected to the cell a current will flow as a result of the potential that is created by the transfer of the electrons The potential is a function of the structure of the semi conductor and of the dye The solar cell itself consists of two con ducting glass electrodes in a sandwich con figuration with an electrolyte separating the two see Fig 1 During the fabrication of the cell a layer of titanium dioxide is deposited onto one of the electrodes This is achieved by using a colloidal preparatio
123. ck out www mamodspares co uk SUPER WIDEBAND RADAR DETECTOR Whistler 1630 Detects both radar and laser X K and KA bands speed cameras and all known speed detection systems 360 degree coverage front and rear waveguides 1 1in x 2 7in x 4 6in fits on visor or dash new low price 99 Ref WH1630 Other models available at www radargun co uk BUG DETECTORS A new detector at a sensible price Detects bugs hidden in rooms computers etc between 1 200MHz adjustable sensitivity 9V PP3 battery required 29 95 Ref BDET2 GIANT WEATHER BALLOONS made by Totex we blew one up to 7ft diameter then it popped due to stones on the ground 13 99 Ref TOTEX PHILIPS VP406 LASER DISC PLAYERS sale price just 9 95 Scart output just put your video disk in and press play standard audio and video outputs 9 95 Ref VP406 12V DC SIRENS Very loud suitable for indoors or outdoors two tone 160mm x 135mm finished in white with bracket 4 99 Ref SIR2A FREEZER MAINS FAIL ALARMS Designed to fit around the mains cable on a freezer this alarm will sound if the device is unplugged from the mains supply battery operated cased built in sounder Ideal for TVs Hi Fi equipment etc 7 01 Ref FRE2 BARNET CROSSBOWS We stock the entire range of crossbows check out our web site at www xbows co uk HOT AIR BALLOON KITS Everything you need to build a 1 7m high 4 5m in circum hot air balloon launch over a small burner or heater 1
124. component layout interwiring to off board switch and jack socket and full size underside copper foil master pat tern are shown in Fig 3 Begin construction by drilling the two mounting holes and soldering the i c sock ets and p c b mounting terminal block TB1 in position Solder the jumper wire to link points A and B Follow with the resistors and capacitors including preset potentiometers VR1 and VR2 Now add the polarity sensitive compo nents which are the electrolytic capacitors l e d D1 diode D2 and buzzer WD1 if this is to be mounted on board taking care over the orientation of these components Adjust preset VR1 to approximately mid track position and VR2 fully anti clock wise as viewed from the bottom edge of the p c b This gives a near zero hold off time Finish construction of the circuit board by inserting C1 but not IC2 at this stage into its socket taking care with the orientation Since this is a CMOS component it is vul nerable to damage by static charge which may be present on the body To avoid any such problems touch something which is earthed such as a metal water tap before removing the i c from its packaging TESTING It will be found convenient to make a basic test on the unit before the p c b is mounted in its box In this way errors are more easily corrected and the preset poten tiometers are more accessible Cut off a short piece of light duty twin wire to connect the microp
125. crisp clear signal Two stage circuit Kit includes microphone and requires a simple open dipole aerial 8 30VDC PCB 42x45mm 1009KT 14 95 4 WATT FM TRANSMITTER Comprises three RF stages and an audio preamplifier stage Piezoelectric microphone supplied or you can use a separate preampli fier circuit Antenna can be an open dipole or Ground Plane Ideal project for those who wish to get started in the fascinating world of FM broadcasting and want a good basic circuit to experiment with 12 18VDC PCB 44x146mm 1028KT 22 95 AS1028 34 95 15 WATT FM TRANSMITTER PRE ASSEMBLED amp TESTED Four transistor based stages with Philips BLY 88 in final stage 15 Watts RF power on the air 88 108MHz Accepts open dipole Ground Plane 5 8 J or YAGI antennas 12 18VDC PCB 70x220mm SWS meter needed for alignment 1021KT 99 95 SIMILAR TO ABOVE BUT 25W Output 1031KT 109 95 STABILISED POWER SUPPLY 2 30V 5A As kit 1007 above but rated at 5Amp Requires a 24VAC 5A transformer 1096KT 27 95 MOTORBIKE ALARM Uses a reliable vibration sensor adjustable sensitivity to detect movement of the bike to trigger the alarm amp switch the output relay to which a siren bikes horn indicators or other warning device can be attached Auto reset 6 12VDC PCB 57x64mm 1011KT 11 95 Box 2011BX 7 00 CAR ALARM SYSTEM Protect your car from theft Features vibration sensor courtesy boot light voltage drop sensor and bonnet boot earth
126. d Whilst the book is mainly intended as an introduction it is also an invaluable reference book and the browser should find it engrossing Order code BP411 5 49 FAULT FINDING ELECTRONIC PROJECTS R A Penfold Starting with mechanical faults such as dry joints short circuits etc coverage includes linear circuits using a meter to make voltage checks signal tracing techniques and fault finding on logic circuits The final chapter covers ways of testing a wide 151 pages 120 pages 380 DIREC I BOOK SERVICE The books listed have been selected by Everyday Practical Electronics editorial staff as being of special interest to everyone involved in electronics and computing They are supplied by mail order direct to your door Full ordering details are given on the last book page FOR A FURTHER SELECTION OF BOOKS SEE THE NEXT TWO ISSUES OF EPE All prices include UK postage range of electronic components such as resistors capacitors operational amplifiers diodes transistors SCRs and triacs with the aid of only a limited amount of test equipment The construction and use of a Tristate Continuity Tester a Signal Tracer a Logic Probe and a CMOS Tester are also included Order code BP391 5 49 136 pages TEST EQUIPMENT CONSTRUCTION R A Penfold This book describes in detail how to construct some simple and inexpensive but extremely useful pieces of test equipment Stripboard layouts are provided for all design
127. d they are perfectly adequate for most small projects For larger projects it is probably worthwhile paying the extra for an instrument case The finished unit will probably look much better in an instrument case and it will be easier to build as well Size Is Important How do you work out whether or not a likely looking case will actually S ae S 335 accommodate your latest project Measurements taken from the circuit board and other large components might give some guidance but even this early in the proceedings it is really advisable to give some thought to the general layout of the project There is otherwise a risk of buying a case that is big enough to take the components but not with the components positioned sensibly Most component catalogues give both the internal and external dimen sions for cases It is the internal dimen sions that are of most importance Where no internal size is given deduct ing about 8 millimetres from the exter nal dimensions usually provides figures that are quite close to the internal ones There is a slight problem in that most cases have internal obstructions that effectively reduce their internal dimen sions For example most cases have mounting pillars and or guide rails for printed circuit boards and threaded pil lars for the lid mounting screws Many cases have mouldings that seem to serve no purpose at all and make it difficult to fit in even the sim ple
128. d complete with all components high quality PCBs 2 x 25W CAR BOOSTER AMPLIFIER Connects to the output of an existing car stereo cassette player CD player or radio Heatsinks provided PCB 76x75mm 1046KT 24 95 3 CHANNEL WIRELESS LIGHT MODULATOR No electrical connection with amplifier Light modu lation achieved via a sensitive electret microphone Separate sensitivity control per channel Power handing 400W channel PCB 54x112mm Mains powered Box provided 6014KT 24 95 12 RUNNING LIGHT EFFECT Exciting 12 LED light effect ideal for parties discos shop windows amp eye catching signs PCB design allows replacement of LEDs with 220V bulbs by inserting 3 TRIACs Adjustable rotation speed amp direction PCB 54x112mm 1026KT 15 95 BOX for mains opera tion 2026BX 9 00 DISCO STROBE LIGHT Probably the most excit ing of all light effects Very bright strobe tube Adjustable strobe frequency 1 60Hz Mains powered PCB 60x68mm Box provided 6037KT 28 95 NOT cheap Tripad strip board and detailed assembly operating instructions ANIMAL SOUNDS Cat dog chicken amp cow Ideal for kids farmyard toys amp schools SG10M 5 95 3 1 2 DIGIT LED PANEL METER Use for basic voltage current displays or customise to measure temperature light weight movement sound lev els etc with appropriate sensors not supplied Various input circuit designs provided 3061KT 13 95 IR REMOTE TOGGLE SWITCH Use any T
129. d like a sample copy of RADIO BYGONES J Yes I would like to take out a subscription for J One year 6 issues J Two years 12 issues I enclose a cheque Eurocheque PO for payable to Wimborne Publishing Ltd J Please debit my card Please print clearly and check that you have the number correct My address If you do not wish to cut your magazine send a letter or a copy of this form 366 Everyday Practical Electronics May 2002 with David Barrington PIC Big Digit Display It is important that constructors keep to the specified semiconductor devices when putting together parts of the PIC Big Digit Display project The L293DN 16 pin Half H driver chip also known as a stepper motor driver i c was purchased from Rapid Electronics amp 01206 751166 or www rapidelectronics co uk code 82 0192 The D denotes it is a 16 pin device and has diode protection Do not use other L293 device types as they may not have the same characteristics for instance the L293E has 20 pins and cannot be used Check out the Texas web site at www ti com Bulk purchasing has enabled Display Electronics 0208 653 3333 or www distel co uk to offer the British Rail giant 10 inch 7 segment electromechanical display at a very reasonable price claimed to be less than 30 per cent of the original A single display module code RW44 cost just 29 95 plus VAT and 99 plus VAT for four units code PH26 A carriage charge will need to be
130. dard air service 52 express airmail 2 Years UK 52 00 Overseas 64 00 standard air service 99 express airmail To Everyday Practical Electronics Wimborne Publishing Ltd 408 Wimborne Road East Ferndown Dorset BH22 9ND Tel 01202 873872 Fax 01202 874562 E mail subs epemag wimborne co uk Order from our online shop at www epemag wimborne co uk shopdoor htm International MAKE SURE OF YOUR COPY NOW enclose payment of cheque PO in sterling only Diners Cub Payable to Everyday Practical Electronics BUA AACL VISA EE a Mastertard My card number iS scssctecnsssietncencasdcantnisanscccunkslaionaisnenatedeethganmateindenaed Please print clearly and check that you have the number correct Signature Card Ex Date Switch Issue No Subscriptions can only start with the next available issue For back numbers see the Back Issues page If you do not wish to cut your issue send a letter or a copy of this form Everyday Practical Electronics May 2002 367 EPE Tutorial Series TEACH IN 2002 Part Seven More on Noise plus Comparators and Digital Optical Sensing IAN BELL AND DAVE CHESMORE Making Sense of the Real World Electronics to Measure the Environment measure the quantity that they are sensi tive to temperature humidity strain etc We may simply be interested in moni toring or recording this value e g the tem perature of
131. ded to whatever capaci ty you like up to 10 watts and 12V per assembly Cells cost 49 Ref HFC11 SMOKE ALARMS Mains powered made by the famous Gent company easy fit next to light fittings power point Pack of 5 15 Ref SS23 pack of 12 24 Ref SS24 CCTV CAMERAS FROM 25 Check out our web site at www cctvstuff co uk and www home cctv co uk 14 WATT SOLAR PANELS Amorphous silicon panel fitted in an anodised aluminium frame Panel measures 3ft by 1ft with 3m leads for easy connection 3ft x 1ft solar panel 79 Ref MAG45 Unframed 4 pack 8 9W 3ft x 1ft 99 Ref SOLX 35 watts of solar power for just 99 4 panels each one 3ft x 1ft and pro ducing 8W min 13V Pack of four 99 Ref SOLX NEW 12V 12in SQUARE SOLAR PANEL Kevlar backed 3 watt output copper strips for easy solder connections 14 99 Ref 15P42 Pack of four just 39 95 Ref 15P42SP NEW UNIVERSAL SOLAR CHARGER Charges AAAs AAs Cs and D type NiCads 9 99 Ref UNISOL 12V SOLAR POWER WATER PUMP Perfect for many 12V d c uses from solar fountains to hydroponics Small and compact yet powerful works direct from our 10W solar panel in bright sun Max HD 17ft max flow 8 Lpm 1 5A Ref AC88 18 99 SOLAR MOTORS Tiny motors which run quite happily on voltages from 3V 12V d c Works on our 6V amorphous 6in panels and you can run them from the sun 32mm dia 20mm thick 1 50 each MAMOD STEAM ENGINES and a full range of spare parts Che
132. details of component buying for this project ACKNOWLEDGEMENT The author thanks Display Electronics www distel co uk for providing the Big Digits for experimental use in the develop ment of this project Everyday Practical Electronics is published on the second Thursday of each month and distributed S O R by COMAG Make sure of your copy of EPE each month cut out or photostat this form fill it in and hand it to your newsagent Everyday Practical Electronics May 2002 i ie PRACTICALLY SPEAKING Robert Penfold looks at the Techniques of Actually Doing It SS project construction is certainly a technical hobby but it is not only a matter of test equipment PIC programming and electronic theo ry It is not just soldering irons elec tronic components and circuit boards either There is also a nuts and bolts side to the hobby Having completed a circuit board successfully you are by no means home and dry There is usual ly a fair amount of work to do before you are ready to show off your new masterpiece You should not find things too difficult if you have a reasonable selection of tools and often undertake DIY jobs around the house On the other hand project construction and general DIY jobs are certainly different Electronic project construction requires a more gentle approach The hammer and tongs approach usually ends in disaster with a lot of time and materials being wasted Most proj
133. digit address Such a facility would be of help in a dis play having many digits and where only one or two might need to be changed at any time This would remove the need to key in data for all digits in the full display when only a few might need changing LISTING 3 DATA 41100011 Another option open to those who are familiar with QB programming is to write a code routine that allows a string of char acters to be entered via the keyboard as a sentence using INPUT instead of INKEY This would not be transmitted to the PIC until the lt ENTER gt key had been pressed Each character would then be sent automatically in sequence to suc cessive digits as required SETTING PULSE LENGTH So far the discussion has assumed that the length of the control pulse that activates the segment coils is correct Setting preset VRI earlier to a fully clockwise position sets the length to the maximum design limit It is likely that the pulse can be short ened so speeding segment changes The simple data sheet received indicated that a pulse length of about 0 25 seconds was required Experiments with the digits showed that it could be much shorter Although there was a slight variation in minimum operational pulse length for the various segments the requirements were typically found to be about 70 millisec onds but cannot be guaranteed in other assemblies hence the need for user adjust ment rather than specifying the length as
134. ding Inductors The Schmitt Trigger Part 5 Circuit Surgery Interface e New Technology Update Net Work The Internet Page APRIL 01 PROJECTS e Wave Sound Effect e Intruder Alarm Control Panel Part 1 Sound Trigger EPE Snug Bug Pet Heating Control Centre FEATURES e The Schmitt Trigger Part 6 e Practically Speaking Ingenuity Unlimited Circuit Surgery Net Work The Internet Page e FREE supplement An End To All Disease MAY 01 PROJECTS e Camcorder Mixer PIC Graphics L C D Scope D C Motor Controller Intruder Alarm Control Panel Part 2 FEATURES e The Schmitt Trigger Part 7 Interface Circuit Surgery Ingenuity Unlimited New Technology Update Net Work The Internet Page JUNE 01 PROJECTS Hosepipe Controller In Circuit Ohmmeter Dummy PIR Detector Magfield Monitor FEATURES e Controlling Jodrell Bank e PIC1687x Extended Memory Use e Practically Speaking Ingenuity Unlimited e New Technology Update Circuit Surgery Net Work The Internet Page JULY 01 PROJECTS e Stereo Surround Sound Amplifier e PIC to Printer Interface Perpetual Projects 1 Solar Powered Power Supply and Voltage Regulator MSF Signal Repeater and Indicator FEATURES e The World of PLCs Ingenuity Unlimited Circuit Surgery New Technology Update Net Work The Internet Page PROJECTS e Digitimer Lead Acid Battery Charger Compact Shortwave Loop Aer
135. e previous experience of electronics The PIC processors have plenty of useful features but they are still reasonably simple and straightforward to use This book should contain everything you need to know Topics covered include the PIC register set numbering systems bitwise operations and rotation the PIC instruc tion set using interrupts using the analogue to digital converter clock circuits using the real time clock counter RTCC using subroutines driving seven segment dis plays Order code BP394 6 49 166 pages PRACTICAL OSCILLATOR CIRCUITS A Flind Extensive coverage is given to circuits using capacitors and resistors to control frequency Designs using CMOS timer i c s and op amps are all described in detail with a special chapter on waveform generator i c s Reliable white and pink noise generator circuits are also includ ed Various circuits using inductors and capacitors are cov ered with emphasis on stable low frequency generation Some of these are amazingly simple but are still very useful signal sources Crystal oscillators have their own chapter Many of the circuits shown are readily available special i c s for simplicity and reliability and offer several output frequen cies Finally complete constructional details are given for an audio sinewave generator 133 pages Order code BP393 5 49 PRACTICAL ELECTRONIC CONTROL PROJECTS Owen Bishop Explains electronic control th
136. e signals of interest It therefore ensures greater accuracy in diagnosing machinery defects Also with its high frequen cy potential it will be suitable for use in the field of communication data encryption and associated disciplines The above technique and equipment has already been successfully used within indus try There is a patent pending on this technique and more information can be seen on our web site at www HolisticSignals co uk Stephen H Alsop Sands Systems Ltd Sheffield via email Thanks Stephen Historically I under stand that Nyquist was a radio engineer investigating the most economically reliable method for transmitting speech data It was in this context that his ratios were estab lished with 2 1 being the absolute minimum but 3 1 being considered better for adequate intelligibility Although I know that stable waveforms can be accurately sampled at frequencies well below their fundamental I assume your tech niques are far superior In which case you have an amazing breakthrough a bit like breaking the light barrier or turning the arrow of time backwards you and your classmates at school probably even written using invisible lemon juice ink Thats how we felt Mini Enigma would find appeal as a modern equivalent Nick himself replies It is nice to hear from someone who also takes an interest in encryption techniques I appreciate your comments pointing out that the encryption
137. ean square value of a continuous sinewave This gives the lowest rating and is the most realistic expression of the amplifier s ability to deliver power into a load speaker An increase in output power is reflected as much if not more in the cost of the power supply as it is in the actual amplifi er Because the theme of this article is good performance at modest cost the most powerful amplifier described is rated at 12 5W rm s DISTORTION Manufacturers of power amplifier inte grated circuits and modestly priced hi fi systems which invariably incorporate devices of this kind usually rate the max imum power output at 10 per cent distor tion At this level there is a very noticeable roughness to the sound and clipping of the waveform on loud passages The power output levels quoted here have been measured just before the onset of clipping or any noticeable distortion of the output waveform They are somewhat lower than the figures quoted by the i c manufacturers but they do represent the highest output free from audible distor tion that the device can deliver for a par ticular supply voltage and load NOISE Modern power amplifier i c s have a very low noise level Manufacturers usual ly define this internally generated electri cal noise as an equivalent signal voltage at the input but this doesn t give the average experimenter an immediate impression of its audible effect Accordingly the devices describ
138. ect current d c This prevents it interfering with the d c conditions of the op amp STANDING CONDITIONS As far as d c is concerned the op amp non inverting input pin 3 is held at one half of supply voltage 3V nominally by the potential divider action of equal value resistors R3 and R4 Regarding the a c signal it is at OV since the impedance of Component layout on the finished circuit board capacitor C2 is very small at the audio fre quencies involved The standing d c volt age at the output pin 1 is equal to that at the non inverting input that is nominal ly 3V The gain of the amplifier is determined by the ratio of feedback resistance R5 to input resistance R2 In fact the gain is negative but this has no practical conse quence here With the values specified the gain is therefore fixed at 220 The result is that a voltage of some 1V peak to peak will exist at the output pin 1 and this will be superimposed on the standing d c voltage Capacitor C3 connected in parallel with the feedback resistor R5 provides a low impedance path at higher frequencies but a much higher one at the typical frequencies of vibration It thus has little effect at the intended frequencies but the gain is much reduced at higher ones The circuit is therefore less sensitive to much of the normal sound in the vicinity of the washing machine ON THE LEVEL The level detector based on IC1b loo
139. ects are housed in plastic or aluminium cases that are easily damaged Some cases are actually quite tough but many of the plastic cases are prone to cracking and it is easy to dent or distort most aluminium cases Bear in mind that most cases have finishes that are easily spoiled With the nuts and bolts side of construction it is definitely advisable to proceed carefully and always use the minimum amount of force Look Before You If you look through a selection of pro ject articles you will find detailed instruc tions for building the circuit boards and completing the hard wiring Articles are usually more sketchy about the mechan ical side of construction This is simply because most constructors prefer to do their own thing with this aspect of project building You can try to produce an exact copy of the original each time you build a project but it is more interesting and sat isfying if you do things your own way You A wide range of inexpensive plastic boxes are available they are well suited to most small projects Everyday Practical Electronics May 2002 have greater freedom when doing your own thing but the chances of ending up with a complete mess are greatly increased It is fair to say that careful planning is important when building anything and electronic projects are certainly no exception Simply making it up as you go along is likely to produce an end result that looks muddled
140. ed Solid State Printed Circuit Mounting etc CALL or see our web site www distel co uk for more information Many obsolete types from stock Save s ALL ENQUIRIES 0208 653 3333 FAX 0208 653 8888 LECIRGINICS All prices for UK Mainland UK customers add 17 5 VAT to TOTAL order amount Minimum order 10 Bona Fide account orders accepted from Government Schools Universities and Local Authorities minimum account order 50 Cheques over 100 are subject to 7 working days clearance Carriage charges A 3 50 B 6 50 C 10 D 15 00 E 18 00 F CALL Allow approx 3 days for shipping faster CALL All goods supplied to our Standard Conditions of Sale which can be viewed at our website and unless stated guaranteed for 90 days All guarantees on a retum to base basis All rights reserved to change prices specifications without prior notice Orders subject to stock Discounts for volume Top CASH prices paid for surplus goods All trademarks tradenames etc acknowledged Display Electronics 2002 E amp O E Est 26 Years BIOPIC HEARTBEAT MONITOR The Biopic monitors heartbeats across the chest using simple electrodes and outputs the display to a PC compatible computer via an electrically isolated serial data link Pulse rates can be monitored separately by a handheld sensor that detects the opacity of the thumb which changes as blood pulses through it Based on a PIC16F876 microco
141. ed here were tested by disconnecting the signal source turning the input or volume control to maximum and then listening to the out put on a pair of sensitive Walkman type earphones In all cases the noise was no more than barely audible The two devices which can be configured for high gain LM386N and TBA820M did produce a faint but audi ble hiss when the gain was set at maxi mum The hiss was also noticeable with a loudspeaker connected However when the gain preset was turned back a little these i c s became as silent as the rest Some constructors may need the highest possible gain and details will be given later of measures which can be taken to eliminate the noise Everyday Practical Electronics May 2002 STABILITY Provided a few basic precautions are observed the amplifiers are all uncondition ally stable Most 1 c s of this kind have a ground connection for the input circuitry and a separate ground pin for the output stage The printed circuit board p c b layouts have been designed to maintain this isola tion and care should be taken to ground the signal inputs and connect the negative power supply lead to the designated points on the board Failure to do this could result in motor boating low frequency instability Input leads should be screened to avoid mains hum and radio frequency r f sig nal pick up Speaker leads should be twist ed together to minimise external fields Input and outp
142. ed identically to those in Bank 1 refer ring to Fig 6 The connection points on the p c b are those alongside IC1 previously left unused The difference is that their enable pins 1 and 9 need to be controlled by a different Port A pin RAI for Bank 2 and RA2 for Bank 3 It is permissible to omit IC3 in the final bank if the digit count does not require it If more than three Banks are needed more than 24 digits pins RAO to RA3 should be wired into another 74HC237 mounted on stripboard at its pins AO to A2 The outputs would then be used as the Bank Select lines for up to eight pairs of C2 and IC3 If using the extra 74HC237 remove the p c b link wire marked Bank 1 Link Connect point Y to pin YO of the new mul tiplexer Point X then becomes the point to be regarded as the RAO connection The software for the PIC and the PC will need to be modified to cope with more than three banks of digits For this reason only readers highly familiar with programming in both PIC and QB languages should undertake this option To such experi enced programmers the changes required should be obvious PULSEIT movlw 00010000 LISTING 4 Send pulse to segment control number of cycles required but the author cannot pie PULSECNT ffer advi it N can advice be offered btfss PORTA has bit 4 gone high cap charged on a breadboard lay up enough out for any additional goto PULSE2 no repeat check chips added bef PORT
143. eeds His intention has been to show with this design how the Big Digits can be controlled and to provide an elemen tary framework within which readers can work to suit their own needs and the number of digits actually used Readers who do not wish to tailor the pro grams though will find that the software is perfectly usable as it stands and that it NEWSAGENTS ORDER FORM Please reserve deliver a copy of Everyday Practical Electronics for me each month provides a reasonable method of controlling the digits whether just one is used or many more We would be interested to know how many you use and in what applications RESOURCES The software for this design is available on 3 5in disk for which a nominal han dling charge applies from EPE Editorial office or free via the EPE ftp site path PUB PICS bigdigit The easiest route to the ftp site is via the link at the top of the main EPE web page at www epemag wimborne co uk The PIC software is supplied as a source code ASM TASM grammar HEX code MPASM and OBJ code TASM It was developed using EPE Toolkit Mk3 TK3 The PC program is supplied as a stand alone program EXE and as QBasic Quick BASIC source code BAS The PIC configuration required is XTAL XS POR on WDT off This is embedded in the ASM and HEX codes but readers using the TASM OBJ code must configure the PIC in the usual separate manner Ensure that you read this month s Shoptalk page for
144. eee feed ed ee et eleele eee eee eee eet et eee eee eee eee Wimborne Publishing Ltd Dept Y5 408 Wimborne Road East Ferndown Dorset BH22 9ND Tel 01202 873872 Fax 01202 874562 Online shop www epemag wimborne co uk shopdoor htm me me e e e e e e e e e e e e e e e e e e e e e e e m m e e e e e m e e e e m m m e e e P LEAS E send me VISA op ORDER FORM Simply complete and return the order form with your payment to the following address Wimborne Publishing Ltd Dept Y5 408 Wimborne _ THE MODERN ELECTRONICS MANUAL CD ROM version only r I I I I I I ELECTRONICS SERVICE MANUAL plus a FREE SUPPLEMENT Printed version only Road East Ferndown Dorset BH22 9ND l enclose payment of 24 95 for one Manual or 39 90 for both Manuals saving another We offer a 30 day MONEY BACK GUARANTEE 10 by ordering both together plus postage if applicable Offers end May 31st 2002 on ESM see the panel above for details i I also require the appropriate Supplements four times a year These are billed separately i i and can be discontinued at any time Please delete if not required POSTAGE CH ARG ES FOR ESM i i MEM CD ROM POST FREE TO ALL COUNTRIES FULL DOA aicy wit eek ow ah a een he nA Ste ae Qc ee we ce See Note we use the VAT portion of the MEM CD ROM payment PLEASE PRINT to pay for overseas postage l ADDRESS ee Price PER ESM PRINTED MANUAL l Postal Region Surface Air l Mainland UK FR
145. efore to minimise the current drawn all the pins are made inputs high impedance before the Sleep command CONSTRUCTION Fig 9 Main program Construction is very simple The sug Main program start gested stripboard component layout and track cut details are shown in Fig 10 gpio The thermistor can be soldered to a short b 00000111 length of wire such as thin audio coax An i i improvement would be to waterproof the thermistor connections by dunking it in O f B thermistor in your fingers to warm it up and the alarm O Fig 10 Stripboard layout for the Freezer Alarm should sound let go to allow the thermistor to cool again to room temper ature and the alarm should stop pio Once you are convinced all is well put b 11001111 the thermistor in the freezer and after wat and prescaler allowing time for the temperature to sta initialise I O polyurethane varnish The wire can be fed setup bilise increase the resistance on the preset into the freezer via the door seal delay settle down gt D Sa threshold is set where you It is important to resist the temptation to measureR E add a light emitting diode as a battery indi measure T In fact the best way to find out if the cator the Led would take about a thou compare batteries are OK is to let the thermistor sand times more power than the rest of the once sale rice warm up a bit when you open the freezer circuit gt ifco s
146. ell matching adaptors that plug into the reader slot Music On Time By Barry Fox RECORD companies want radio and club DJs to have new releases ready to play on official release day But if records go out in advance some DJs break the embargo So Warner Music in the US has patented a sys tem for enforcing the embargo electronical ly WO 01 15428 A batch of music CDs for DJs will be encrypted so they play back only on a modified player The encryption is time coded and the key tied to the official release date To stop DJs cheating by advancing the player clock the time code comes from GPS satellites So everyone in the world gets to play their records for the first time at the same time National Vintage Communications Fair THE National Vintage Communications Fair will be held at N E C Birmingham on Sunday 5 May 2002 It is the Tenth Anniversary Special and doors open from 10 30am to 4 00pm at an entry price of 5 Do come and have a chat with our sister publication Radio Bygones on their stand All visitors will receive a free copy of the Sound amp Vision Yearbook s Collector s Guide This useful directory is really the book of the show but contains information that will be useful long after the show has closed For more information contact N V C F 13 Belmont Road Exeter Devon EX1 2HF Tel 01392 411565 Email sun press btinternet com Web www anglefire com tx sunpress index html Mainline s
147. ely simple and the software uses several techniques which could be useful in other projects BABY PIC The design uses the baby of the PIC family the PIC12C508 This is an extra ordinarily versatile device and in its OTP one time programmable version is very inexpensive It is housed in an 8 pin d i l package see Fig 1 and has the same set of 33 RISC instructions as its big brothers S 316 Vb gt 1 8 Vss GP5 OSC1 CLKINa gt 2 7 GPO GP4 0SC2 lt gt 3 6 lt GPI GP3 MCLR Vpp gt 4 5 lt GP2 TOCK1 _ fa data RAM available program memory is 512 bytes There are two internal timers one of which is a Watchdog and it can drive output devices with currents up to 50mA This little PIC is extraordinarily versa tile and for many applications provides adequate microcontroller power Of course the more powerful versions such as the PIC16F84 can be programmed to Operate in just the same way with few changes to the software but why use a sledge hammer to crack a nut Fig 1 above The Bes pin diagram for the PIC12C508 micro oe controller RIES 10k N T C Fig 2 right Circuit diagram for the Freezer Alarm OV IC1 120508 OP PIEZO SOUNDER Two pins are used for power between 2 5V and 5 5V the remainder can be con figured as five I O input output pins and one input only pin An in built oscillat
148. eminds of when my wife and I were in Zante one of the Greek islands Cycling along a main road that had recently been white lined the painting gang had not bothered to avoid a snake in their path which was now also painted but dead of course Incidentally I m soon to start testing an Earth Resistivity Logger that I think I have designed for archeology TK3 AND PIC16F74 Dear EPE Is it possible to modify the TK3 software to incorporate the PIC16F74 I have several for my private use but no means to program them as yet It would seem they are not as popular as their 8K cousins Peter Barratt Australia via email It appears to be pin compatible with the F874 7 series and should program OK in TK3 just treat it as being from that family although its configuration bits may not be the same Reading its data sheet via www microchip com should give you the 74 s full details Everyday Practical Electronics May 2002 Learn About Microcontrollers PIC Training amp Development System The best place to start learning about microcontrollers is the PIC16F84 This is easy to understand and very popular with construction projects Then continue on using the more sophisticated PIC16F877 family The heart of our system is a real book which lies open on your desk while you use your computer to type in the programme and control the hardware Start with four very simple programmes Run the simulator to see how they work Te
149. en register it with your local DVLC HYDROPONIC GROWING SYSTEMS Complete everything you need apart from plants and light contains grow tank nutrients pump tester etc GT205 710mm x 390mm NFT system 31 45 Ref GT205 GT424 1070mm x 500mm NFT system 58 65 Ref GT424 ELECTRIC BIKES 679 Viking built in indicators radio lights 13mph 5 hour charge Shimano gears up to 50 mile range horn 26in wheels suspension no licence needed key operated 679 Ref VIKING PIR PCBs These contain a standard PIR detector circuit with all components easy to wire up and use Pack of 4 6 Ref PIR8 NEBULISER WATER ATOMISER Ultrasonic module that you place in water atomises the water into a very fine mist many applications from special effects to scientific 69 Ref NEB6 PORTABLE X RAY MACHINE PLANS Easy to construct plans on a simple and cheap way to build a home X ray machine Effective device X ray sealed assemblies can be used for exper imental purposes Not a toy or for minors 6 set Ref F XP1 TELEKINETIC ENHANCER PLANS Mystify and amaze your friends by creating motion with no known apparent means or cause Uses no electrical or mechanical connections no special gimmicks yet produces positive motion and effect Excellent for science projects magic shows part demonstrations or serious research and development of this strange and amazing psychic phenomenon 4 set Ref F TKE1 ELECTRONIC HYPNOSIS PLANS amp DATA
150. eory in simple non mathe matical terms and is illustrated by 30 practical designs suitable for the student or hobbyist to build Shows how to use sensors as input to the control system and how to provide output to lamps heaters solenoids relays and motors Computer based control is explained by practical exam ples that can be run on a PC For stand alone systems the projects use microcontrollers such as the inexpensive and easy to use Stamp BASIC microcontroller 198 pages Temporarily out of print PRACTICAL ELECTRONICS HANDBOOK Fifth Edition lan Sinclair Contains all of the everyday information that anyone working in electronics will need It provides a practical and comprehensive collection of circuits rules of thumb and design data for professional engineers students and enthusaists and therefore enough background to allow the understanding and development of a range of basic circuits Contents Passive components Active discrete components Circuits Linear C s Energy conversion com ponents Digital C s Microprocessors and microprocessor systems Transferring digital data Digital analogue conver sions Computer aids in electronics Hardware components and practical work Microcontrollers and PLCs Digital broad casting Electronic security 440 pages Order code NE21 16 99 COIL DESIGN AND CONSTRUCTIONAL MANUAL B B Babani A complete book for the home constructor on how to make RF IF audio
151. er Design which includes an expert system and filter synthesis tool for the design of low pass high pass band pass and band stop Bessel Butterworth and Chebyshev op amp filters DIGITAL WORKS 3 0 Digital Works Version 3 0 is a graphical design tool that enables you to construct digital logic circuits and analyze their behaviour It is so simple to use that it will take you less than 10 minutes to make your first digital design It is so powerful that you will never outgrow its capability Software for simulating digital logic circuits Create your own macros highly scalable Create your own circuits components and i c s Easy to use digital interface Animation brings circuits to life Vast library of logic macros and 74 series i c s with data sheets e Powerful tool for designing and learning ELECTRONICS CAD PACK PCB Layout Electronics CADPACK allows users to design complex circuit schematics to view circuit animations using a unique SPICE based simulation tool and to design printed circuit boards CADPACK is made up of three separate software modules These are restricted versions of the full Labcenter software ISIS Lite which provides full schematic drawing features including full control of drawing appearance automatic wire routing and over 6 000 parts PROSPICE Lite integrated into ISIS Lite which uses unique animation to show the operation of any circuit with mouse operated switches p
152. er the number of digits to be controlled and press lt ENTER gt The program then enters its full opera tional mode first drawing on screen the same number of boxes as the number of digits specified These boxes represent the 7 segment digits and display the same characters Next the program sends data for numer al 8 to all digits required It then sends a reset command to the PIC resetting it for Digit 1 after which it sends data to clear all required digits again followed by a reset command This action has three functions to syn chronise the PIC with the computer s order of digits to prime the PIC so that it knows which segments are in which state and thirdly to clear any existing display data In the latter context it is worth recog nising that the segments can be set by hand without damaging them They are only balanced on light duty pivots freely responding to the electromagnetic fields generated by their coils It is quite possi ble that someone could have set them by hand to random positions In a field Situation it is advisable to enclose the digits to prevent this happening and of course to protect them from the elements From this point onwards pressing any recognised key causes the data to be dis played sequentially with the count return ing to zero Digit 1 after the final digit or on pressing lt ENTER gt as described earlier An example PC screen display is shown in Fig
153. er with all components except box and PC cable 12VDC PCB 70x200mm 3074KT 31 95 2 CHANNEL UHF RELAY SWITCH Contains the same transmitter receiver pair as 30A15 below plus the components and PCB to control two 240VAC 10A relays also supplied Ultra bright LEDs used to indicate relay status 3082KT 27 95 TRANSMITTER RECEIVER PAIR 2 button keyfob style 300 375MHz Tx with 30m range Receiver encoder module with matched decoder IC Components must be built into a circuit like kit 3082 above 30A15 14 95 PIC 16C71 FOUR SERVO MOTOR DRIVER Simultaneously control up to 4 servo motors Software amp all components except servos control pots supplied 5VDC PCB 50x70mm 3102KT 15 95 UNIPOLAR STEPPER MOTOR DRIVER for any 5 6 8 lead motor Fast slow amp single step rates Direction control amp on off switch Wave 2 phase amp half wave step modes 4 LED indicators PCB 50x65mm 3109KT 14 95 PC CONTROLLED STEPPER MOTOR DRIVER Control two unipolar stepper motors 8A max each via PC printer port Wave 2 phase amp half wave step modes Software accepts 4 digital inputs from exter nal switches amp will single step motors PCB fits in D shell case provided 3113KT 17 95 12 BIT PC DATA ACQUISITION CONTROL UNIT Similar to kit 3093 above but uses a 12 bit Analogue to Digital Converter ADC with internal analogue multiplexor Reads 8 single ended channels or 4 dif ferential inputs or a mixture of both Analogue i
154. ern generator amp HP3782A Error Detector POA HP6621A Dual Programmable GPIB PSU 0 7 V 160 watts 1800 HP6264 Rack mount variable 0 20V 20A metered PSU 475 HP54121A DC to 22 GHz four channel test set POA HP8130A opt 020 300 MHz pulse generator GPIB etc 7900 HP A1 AO 8 pen HPGL high speed drum plotters from 550 HP DRAFTMASTER 1 8 pen high speed plotter 750 EG G Brookdeal 95035C Precision lock in amp 1800 Keithley 590 CV capacitor voltage analyser POA Racal ICR40 dual 40 channel voice recorder system 3750 Fiskers 45KVA 3 ph On Line UPS New batteries 4500 Emerson AP130 2 5KVA industrial spoec UPS 1499 Mann Tally MT645 High speed line printer 2200 Intel SBC 486 133SE Multibus 486 system 8Mb Ram 945 MPUTER MONITOR SPECIALS Surrey CR7 8PD Open Mon THE ORIGINAL SURPLUS WONDERLAND THIS MONTH S SELECTION FROM OUR VAST EVER CHANGING STOCKS IC s TRANSISTORS DIODES OBSOLETE SHORT SUPPLY BULK 10 000 000 items EX STOCK For MAJOR sav nGs CALL or see web site www distel co uk CO 14 59 00 Legacy products High spec genuine multysync CGA EGA VGA SVGA Mitsubishi FA3415ETKL 14 SVGA Multisync colour monitor with fine 0 28 dot pitch tube and resolution of 1024 x 768 A vari ety of inputs allows connection to a host of computers including IBM PC s in CGA EGA VGA amp SVGA modes BBC COMMODORE including Amiga 1200 ARCHIMEDES and APPLE Many feature
155. ese materials and works In no event shall Maxfield amp Montrose Interactive Inc or Wimborne Publishing Ltd be responsible or liable for any loss of profit or any other commercial damages including but not limited to special incidental consequential or any other damages in connection with or arising out of furnishing performance or use of these materials and works YUASA ENDURANCE 6V 100AH sealed lead acid batteries 59 each or 10 for 499 GAS MASKS RUSSIAN new and boxed standard NATO filter 39 LOW COST NIGHT VISION system Russian handheld complete with infra red illuminator 0Om range Runs on 2 AA batteries just 109 95 COBRA NIGHT VISION equipment also stocked more info on our web site at www cobra optics co uk ELECTRIC SCOOTERS 18kph 24V motor 6 hour charge time 22kg weight max load 90kg running time up to 1 hour range 15km 8 5A motor 24V direct drive Our Price 229 95 Ref ESCOOT VOICE CHANGERS Hold one of these units over your phone mouthpiece and you can adjust your voice using the controls on the unit Battery operated 15 Ref CC3 EMMINENCE LOUDSPEAKERS 12in dia 50W nom 100W peak 16 ohm impedance Pack of 4 just 39 95 Ref SPEAK39 PIR SECURITY SWITCHES These brand new swivel mounting PIR units will switch up to 2 kilowatts Adjustable sensitivity light level and time delay 9 seconds to 10 minutes 15m detection range mains operated waterproof 5 99 Ref PIR1PACK or a pack of 5 fo
156. ess smoke alarm 49 00 Wireless glass break alarm 49 00 Wireless alarm control panel 99 00 Wireless alarm control panel with digital voice dialler 149 00 Distributors Welcome All prices exclude VAT and carriage All transmitters are licence exempt working on 433 92Mhz All transmitters work with rolling code technology Bitz Technology Ltd sales bitztechnology com 44 0 1753 522 902 Everyday Practical Electronics May 2002 3937 missions for U via E mail Battery Discharger Out im a Flasin TE circuit diagram of Fig 1 discharges any rechargeable 1 5V cell and the light emitting diode D3 starts to flash when the battery connected across the test terminal is sufficiently discharged The design uses a two transistor astable multivibrator operating at a fre quency of about 25kHz When transistor TR2 conducts a current flows through the 4 7mH inductor L1 whereupon energy is stored in the resulting electromagnetic field When TR2 is cut off the surrounding electromagnetic field collaps es which produces a back e m f at a level that exceeds the forward voltage about 1 6V of the l e d D3 A current then flows through the l e d which appears to be continually alight in normal operation Diode D2 prevents the current flowing through resistor R6 and capac itor C2 This process is halted only when the battery voltage no longer provides a sufficient base potential for the transistors and the battery can now be
157. esult in the output pin 7 switching between high and low states at the frequency of vibration The length of the on times will depend on how much the a c wave falls below the voltage at pin 5 as set by preset VR1 This preset therefore provides the Sensitivity control Note that as the supply voltage falls in the process of battery ageing this makes no difference to the operating point This is because the voltages applied to both IC1b inputs vary in the same proportion Ignoring the connection from the output of IClb at pin 7 to resistor R8 for the moment the signal from the output of the level detector can be directed to the light emitting diode l e d D1 using a jumper wire on the circuit board The operating current is limited to some 10mA by series resistor R9 The l e d is used to check operation of the circuit up to this point because it will flash when vibration is picked up It is also used to make a reasonably correct adjust ment to preset VR1 At the end of testing the jumper wire will be cut to prevent the l e d from working and so reduce the cur rent requirement of the circuit INTEGRATION Returning now to the output from the level detector IC1b at pin 7 consider the current flowing through fixed resistor R8 and diode D2 This allows capacitor C4 to charge up and provides the integrator aspect of the circuit While pulses are given by IC1b output pin 7 the relatively small value of resis
158. etotelarimnl if it is working and the alarm sounds the f J J 1 1 The PIC should be plugged into the alarm batteries are fine board via an 8 pin d i l socket The circuit b 11111111 PEEN and batteries can be housed in a plastic box gpio T ire ag it ODI i 1 a T A O 7 er to sit outside the freezer a small hole being p S mentioned earlier the techniques provided to glue the piezo sounder behind explained allow simple modifications to You should not need to replace batteries until reawakened change how the circuit operates very often by wat oa To make the alarm work if something with a reset kiss is too cold rather than too warm for exam a a ee ple as a greenhouse frost alarm simply A head ascii mone goto start should never reach swap over the connections to pins 6 and 7 optatk here Alternatively make the appropriate swaps in the software b The method can be adapted for any Table 2 Option Register Bits resistance changes for example the Bit 7 GPWU Enable 0 or disable 1 wave up on pin change alarm could be made light sensitive by Bit 6 GPPU Enable 0 or disable 1 weak pull up resistors using an l d r light dependent resistor Bit 5 TOCS Timer O clock source instead of a thermistor Whatever thermis Bit 4 TOSE Timer O edge select tor or other device is used VRI needs to Bit 3 PSA Prescaler assignment Assigned to WDT 1 or to Timer O 0 have a resistance which can be set to the Bits 2 0 Prescaler r
159. f Radio Interface Ingenuity Unlimited Circuit Surgery New Technology Update Net Work The Internet Page 2001 Annual Index BACK ISSUES JAN 02 PROJECTS e PIC Magick Musick Time Delay Touch Switch Versatile Bench Power Supply Forever Flasher FEATURES e Teach In 2002 Part 3 Practically Speaking Ingenuity Unlimited New Technology Update Circuit Surgery Net Work The Internet Page PROJECTS PIC Spectrum Analyser Guitar Practice Amp HT Power Supply Versatile Current Monitor FEATURES e Teach In 2002 Part 4 Ingenuity Unlimited Russian Space Shuttle Revisited e Circuit Surgery Interface New Technology Update Net Work The Internet Page PROJECTS e MK484 Shortwave Radio PIC Virus Zapper RH Meter PIC Mini Enigma FEATURES e Teach In 2002 Part 5 Ingenuity Unlimited Programming PIC Interrupts 1 Circuit Surgery Practically Speaking New Technology Update Net Work The Internet Page APR 02 PROJECTS e Electric Guitar Tuner e PIC Controlled Intruder Alarm Solar Charge and Go e Manual Stepper Motor Controller FEATURES e Teach In 2002 Part 6 Interface e Programming PIC Interrupts 2 Circuit Surgery e Ingenuity Unlimited New Technology Update e Net Work The Internet Page FREE Giant Op Amp Data Chart BACK ISSUES ONLY 3 30 each inc UK p amp p Overseas prices 3 80 each surface mail 5 25 each air
160. f doing something does it necessarily follow that every implementa tion does it that way If the spec or data sheet doesn t explicitly state something I think it is safest from a software point of view not to make any assumptions The situation is almost identical with instruc tions in which W is both the source of data and its destination e g SUBWF f W The hardware functions as required because the old value of W at the start is processed with the contents of f and the result clocked back into W to give a new value Hence the new value does not circulate round giving another new value in the same clock cycle Malcolm Wiles INTERRUPTS CONTEXT Dear EPE I wonder if I have misunderstood the concept of changing memory bank as part of the context in Malcolm Wiles Using PIC Interrupts Referring to Listing 2 page 171 it is neces sary to select BANK 1 prior to initiating the read ing of EEPROM by instruction BSF EECONI RD Now what if the interrupt is acti vated between these two instructions One of the actions inside the interrupt service routine at ISR is to set its own context and select BANKO I 354 can t see how the bank selected by the main pro gram is reinstated prior to return at the RETFIE instruction It looks as though the return contin ues to thread main program code but with BANKO still selected Is there some implicit re selection of the main program s required BANK for examp
161. from 0 sound in air depends on the relative direc representing calm to 12 representing hurri tion of the sound in relation to the direc cane force The scale actually goes to 17 tion of the wind and to a lesser degree on 126mph to 136mph but such high wind temperature and barometric pressure speeds are extremely rare Table 7 3 gives the basic Beaufort Scale and corresponding wind speeds in miles per hours It is often useful to be able to convert between the other different wind speed units act Ca eee prea te this is given in Table 7 4 To use the table E Pars 8 Fig 7 15 a Schematic of slotted choose the units e g 30mph to change to Hao p n a n os optosensor and b connections kph read the FROM TO multiplication fac heed T ee ie a T a tor 1 609 and multiply 30mph 48 3kph E Fig 7 14 We use this type of sensor in the To convert back use the TO FROM multipli OPTICALLY MONITORED Lab Work experiments this month er e g 100kph 360ms ANEMOMETER It is possible to use ultrasonic pulses to measure changes in sound velocity and hence determine wind speed These Another application of reflective optosen There ae ane commercial Wee sae Last month we designed a simple rota sors is for proximity sensing i e to sense n B EnA EOMER M tion speed circuit using a magnetic sensor when an object is close to the sensor POR a and a pulse width to voltage converter The schematic diagram of a typical Table 7 3 Beaufo
162. g pole and put it vertically out of a car win dow and drive at a known speed The anemometer needs to be away from the slip stream of the vehicle This requires considerable care remember you are not jousting Ed WIND DIRECTION SENSING Measuring wind direction requires a binary or Gray coded disc and multiple sensors the more bits in the code the higher the resolution but the more complex the circuit The main part of a wind direc tion sensor is a vane and counter weight to ensure balance The vane points into the wind and turns a coded disc All one needs to do is ensure the code s origin is aligned with North and the instrument can be calibrated in relation to the number of bits and the angular dis placement that each represents We discuss wind sensing in a practical sense in Labs 7 2 and 7 3 First though we experiment with comparators TEACH IN 2002 Lab Work 7 DAVE CHESMORE Comparator and Optosensing Experiments plus Anemometer Assembly Lab 7 1 Comparators N this Lab we examine the characteris tics of comparators by building an op amp version of the light switch in Part 2 Fig 7 18 shows the circuit diagram using an OP177 op amp and a light depen dent resistor l d r Since we are using a single 5V supply rail rather than a dual 5V supply we Everyday Practical Electronics May 2002 need to generate a reference voltage This is achieved using Zener diode D1 to give a 2 7V refere
163. g settings made in the ISR itself Recall the discussion in the article which noted that once STATUS has been so restored only non STATUS affecting instructions e g SWAPF can be used in any further ISR code Malcolm Wiles NOTABLY SENIOR Dear EPE This year I will become an official Senior Citizen and although a long time reader of EPE and PE before that I have never written to the magazine before so would you indulge me for a moment and allow me to say Thank you and all contributors for a splendid magazine I have had many hours of pleasure education and also some frustration due to my shortcomings not EPE s In particular the relatively recent interest in PIC s has certain ly given my grey matter a bashing that s not a bad thing and your Toolkit Mk3 is a joy Following the PIC Tutorials has enabled me to modify Bart Trepak s excellent Xmas Lights Dimmer a wonderfully informative article Dec 98 to suit my taste you are definitely never too old to learn My circumstances are such that I am not able to buy EPE every month and this sometimes leaves me with a problem regarding the Please Take Note messages Of course gremlins creep in occasionally that is understood but if I can t afford to buy the mag for a month or two after I ve built a project I miss any error corrections that appear Would it be possible for all error correction notes to be put onto the Web site Of course it wo
164. ge con struction project Supplied in good RFE condition complete with data sheet Less than 30 Only 29 95i8 or 4 99 00 0 of makers price Order RW44 Order PH26 THE AMAZING TELEBOX TV SOUND amp d C Pp Toye eee VIDEO TUNER CABLE COMPATIBLE a ee Converts your colour monitor into a QUALITY COLOUR TV The TELEBOxX is an attractive fully cased mains powered unit containing all electronics ready to plug into a host of video monitors or AV equipment which are fitted with a composite video or SCART input The composite video output will also plug directly into most video recorders allowing reception of TV channels not normally receivable on most television receivers TELE BOX MB Push button controls on the front panel allow reception of 8 fully tuneable off air UHF colour television channels TELEBOX MB covers virtu ally all television frequencies VHF and UHF including the HYPERBAND as used by most cable TV operators Ideal for desktop computer video sys tems amp PIP picture in picture setups For complete compatibility even for monitors without sound an integral 4 watt audio amplifier and low level Hi Fi audio output are provided as standard Brand new fully guaranteed TELEBOX ST for composite video input type monitors 36 95 TELEBOX STL as ST but fitted with integral speaker 39 50 TELEBOX MB Multiband VHF UHF Cable Hyperband tuner 69 95 For overseas PAL ve
165. ges in a ring binder and details a broad selection of remote control systems including Microchip s Keeloq encoders and decoders radio telemetry systems pager control r f modems and radio modules principally based on the standard frequencies of 315 433MHz although modules operating at other frequencies are available Amongst the other products offered are Microchip PIC emulator tools compil ers and programmers an r f pocket meter and radio evaluation boards There is also a 150 page book entitled An Introduction to Low Power Radio which is aimed at the practical engineer and concentrates on discussing theoretical radio matters in an easy to understand manner It is interesting to note that R F Solutions has complimented its range of PIC emulation products with the introduction of a compact low cost programmer The MEL EPICA enables quick and easy programming of 8 pin and 18 pin mid range PIC devices It runs within Win95 98 NT or DOS and is able to integrate with MPLAB There is also a C compiler for quick and easy coding of PICs For more information contact R F Solutions Ltd Unit 21 Cliffe Industrial Estate South Street Lewes E Sussex BN8 6JL Tel 01273 488880 Fax 01273 480661 Email sales rfsolutions co uk Web www rfsolutions co uk BUBBLE TIME By Barry Fox CALTECH the Californian Institute of Technology is patenting a new eye catch ing method of billboard advertising using bubbles WO 01 35379 w
166. get 151 5pps The output of the DAC is determined by Vx D N where V is the maximum voltage that the DAC can output frequently but not always the same voltage as on the positive supply line D is the digital input value usually in binary form N is the number of input bits that the DAC has been designed to accept typical ly having a decimal value range of 0 to 255 8 bit although DACs having other input ranges are available Using an 8 bit DAC as we do in Lab Work to achieve an output voltage of 3 0V for 30ms the input value required is D 3 x 256 5 154 to the nearest inte ger This means we need to count 154 puls es every interval to make the output read 3 0V at 30ms which makes the interval very close to one second precisely calcu lated as 1 016s WIND SPEED CALCULATION Unfortunately wind speed is not the eas iest parameter to calibrate unless you pos sess a wind tunnel The main reason for CLOCK COUNTER RESET Fig 7 17 above Timing diagram of anemometer circuit Fig 7 16 left Block diagram of anemometer circuit this is that the relationship between cup design and rotation speed with wind speed is not straightforward so we cannot per form simple calculations There are two main options for calibration Compare with a commercial anemome ter This is the way we determined the number of pulses per second in the Lab Work design Place the anemometer on a lon
167. ggestion of relay control No it had to be semiconductors in integrated circuit form Anyone familiar with controlling 4 digit 7 segment light emitting diode displays will know that they can easily be controlled by multiplexed signals a common 7 line bus feeding identically to all segments of all digits and then separate power supply lines each feeding to its own digit The technique required then is to send out seg ment control data along the common bus and to only turn on digit power lines indi vidually at the appropriate moment However data sheet browsing suggested that switching seven segments simultane ously at a total of 2A or so could present a significant problem Perhaps switching segments individually at about 280mA would be more sensible There are many chips that can provide l of 8 output selection in response to a 3 bit control code Such chips include the 74HC138 whose outputs are normally high but go low individually when selected by the appropriate control code The 74HC237 operates with the opposite output logic nor mally low but going high when selected Although the outputs of these devices cannot handle the sinking or sourcing of 280mA or a voltage of 12V they are capa ble of driving intermediate high current buffers The question then became one of which buffers were available LINE DRIVER After considerable research it was decided to use the 7 stage line driver type ULN2004A to activa
168. gives cleaner holes that require less deburring With metal panels you will still need to do a certain amount of deburring using a miniature file or there are special tools for this task Be careful when dealing with steel panels Any raised edges around holes are likely to be quite sharp so do not feel for them using a fingertip Look carefully for any projections and imme diately remove any that are found Everyday Practical Electronics May 2002 Video Surveillance C MOS B W Camera 15mm 15mm 29 00 C MOS Colour Camera 15mm 15mm 65 00 PCB B W Camera 32mm 32mm 24 00 PCB Colour Camera w Audio 32mm 32mm 65 00 23cm 1 3GHz Video Audio Transmitter 35 00 13cm 2 4GHz Video Audio Transmitter 35 00 1 2 Watt 2 4GHz Video Audio Transmitter 120 00 4 TFT Boxed Colour Monitor w Audio 110 00 Video to VGA Converter 65 00 VGA to Video Converter 90 00 External USB Video Capture Box 55 00 All prices exclude VAT Many more products on our website WWW BITZTECHNOLOGY COM Tel 01753 522 902 Fax 01753 571 657 RC 11 UC 216 3 channels RC 11 Key fob 3 channels receiver with 2 relays Control Transmitter with output oe from 9V to l2vdc e Rolling Code technology UC 216 with learning mode and rolling code technology RC 11 Price 14 99 UC 216 9 l2Vdc 29 00 UC 222 240 Vac 29 00 Also Wireless pager alarm PG 4W 125 00 Wireless PIR alarm JA 60S 49 00 Wireless door magnet alarm 39 00 Wirel
169. h NEXT MONTH In Part 8 next month we examine control feedback closed loop systems filters sensor actuator combinations with reference to smoke and gas detectors Example of a commercial wind vane EPE BINDERS KEEP YOUR MAGAZINES SAFE RING US NOW This ring binder uses a special system to allow the issues to be easily removed and re inserted without any damage A nylon strip slips over each issue and this passes over the four rings in the binder thus holding the magazine in place The binders are finished in hard wearing royal blue p v c with the magazine logo in gold on the spine They will keep your issues neat and tidy but allow you to remove them for use easily The price is 5 95 plus 3 50 post and packing If you order more than one binder add 1 postage for each binder after the initial 3 50 postage charge overseas readers the postage is 6 00 each to everywhere except Australia and Papua New Guinea which costs 10 50 each Send your payment in s sterling cheque or PO Overseas readers send sterling bank draft or cheque drawn on a UK bank or pay by card to Everyday Practical Electronics Wimborne Puublishing Ltd 408 Wimborne Road East Ferndown Dorset BH22 9ND Tel 01202 873872 Fax 01202 874562 E mail editorial epemag wimborne co uk Web site http Avww epemag wimborne co uk Order on line from www epemag wimborne co uk shopdoor htm i We also accept card payments Mastercard Visa
170. h slew rate ultra low noise and low input offset devices The projects include Low noise tape preamplifier low noise RIAA preamplifier audio power amplifiers d c power controllers opto isolator audio link audio millivolt meter temperature monitor low distortion audio signal generator simple video fader and many more 120 pages Order code BP335 5 45 A BEGINNERS GUIDE TO CMOS DIGITAL ICs R A Penfold Getting started with logic circuits can be difficult since many of the fundamental concepts of digital design tend to seem rather abstract and remote from obviously useful applica tions This book covers the basic theory of digital electronics and the use of CMOS integrated circuits but does not lose sight of the fact that digital electronics has numerous real world applications The topics covered in this book include the basic concepts of logic circuits the functions of gates inverters and other logic building blocks CMOS logic i c characteristics and their advantages in practical circuit design oscillators and monostables timers flip flops binary dividers and binary counters decade counters and display drivers Order code BP333 5 45 119 pages AUDIO AND MUSIC INTRODUCTION TO DIGITAL AUDIO Second Edition lan Sinclair The compact disc CD was the first device to bring digital audio methods into the home This development has involved methods and circuits that are totally alien to the te
171. he PIC the point at which a logic 0 changes to a logic 1 which is about 3 0V say The mathematics of this charging process produces a very simple relation ship namely that the time taken to reach a certain voltage is directly proportional to the value of R so the time we have count ed out until the voltage rises to 3 0V is an accurate representation of the value of the resistor So all we need to do is to time how long it takes for the capacitor to charge via the thermistor then time how long it takes to charge via the preset resis tor If the first time is shorter than the sec ond the thermistor is too warm and we ought to sound the alarm Fig 3 Simple circuit to demonstrate capacitor charging Everyday Practical Electronics May 2002 0 10 20 30 40 50 60 TIME ms Fig 4 Capacitor charging curve INITIALISE MEASURE VR1 MEASURE R1 TIME DELAY SLEEP Fig 5 Flow chart for the main program What makes it possible for the PIC to do this is that not only can we force pins to go high or low but we can also change whether a pin is an output or an input as the program is running Using this fact we can both switch between the two resistors and discharge the capacitor between our readings This is described in the section on programming MAIN PROGRAM The way the program operates is straight forward as illustrated by the flow chart in Fig 5 First the PIC is initi
172. he TDA2003 Fig 9 and Fig 11 it clear that the 14 pin chip is required soldered joints or bridged tracks Check the Because the device incorporates overload The suffix P or V is sometimes orientation of the electrolytic capacitors protection the actual size is not too critical added by suppliers to the TDA2003 to indi and the i c s the i c will shut down when it begins to cate that it is for vertical and H for hor If using a mains power supply make overheat but sustained high output will izontal mounting There is no electrical sure the voltage delivered does not exceed only be developed if the heatsink is ade difference but the p c b s illustrated here the safe working voltage of the amplifier quate At the very least use 40sq cm have been designed for vertical chips for the load impedance being used 6 5sq in of 16s w g aluminium per chip If all is in order connect the power sup or fit a proprietary heatsink with a thermal CONSTRUCTION ply and check the quiescent current con resistance not greater than 7 C per watt All the amplifiers covered in this part are sumption Inject a signal and re check the The i c s are arranged on the p c b see assembled on printed circuit boards and current drain and supply voltage Fig 10 and Fig 12 so that they can be bolt construction is reasonably ed to the back of a metal case by their straightforward The use of Next Month Transistor preamplifiers metal tabs A 50mm
173. hich is sure to set constructors thinking The system can be scaled down to dis play time on a domestic clock A contain er like a very thin fish tank is filled with transparent viscous liquid On the rear side of the tank a matrix of piezoelectric pump holes release globs of coloured liq uid with slightly different viscosity As the globs escape they float slowly up or down like bubbles The pump holes are in groups like the light sources of a digital display to create alphanumeric characters or graphics Caltec says the system works well with coloured detergents Experimenters will doubtless come up with their own varia tions on the new theme Everyday Practical Electronics May 2002 PLUG IN AND FLASHGO By Barry Fox THE computer industry uses five different miniature memory card formats for digital cameras handheld computers PDAs and MP3 players Compact Flash Smart Media Multimedia Card Secure Digital and Memory Stick as well as IBM s tiny Microdrive hard disk Users must use pro prietary leads and software to connect each device to a PC The law of cussedness ensures the right lead for the job is the one lead you have not got Imation a spin off from 3M is now selling a reader with a single slot and matrix of contacts that mates with any known card The reader connects to a PC by single USB lead and all purpose control software FlashGo costs around 60 If more formats emerge Imation will s
174. hoice 8 pin d i l socket multistrand connecting wire audio screened cable solder Fig 2 Printed circuit board component layout full size cop per foil master and interwiring for the LM386N 1 Amp pins solder etc Approx Cost Guidance Only WZ Philips have adopted a bridge arrange ment for the TDA7052 s output stage This enables the chip to maintain a good output at low supply voltages and eliminates the need for a speaker coupling capacitor Gain is fixed internally no provision is made for ripple rejection and there is no Zobel network This reduces the external component count to the d c blocking capacitor C1 Volume control VR1 and the supply line bypass capacitors C2 and C3 The full circuit diagram together with a TDA7052 POWER AMPLIFIER R M S Power output just before the onset of waveform clipping Speaker Supply Voltage Impedance Ohms 3V 4 5V 6V 9V 12V 4 70mW 500mW 780mW 8 60mW 455mW W 640mW 1W 16 40mW 235mW W 450mW 112W 32 24mW 145mW W 250mW 600mW 1 26W Quiescent current 5mA Input resistance 100k ohms Input sensitivity for 1W output 8 ohm load 9V supply Absolute maximum supply voltage 40mV r m s gain 70 specification guide for the TDA7052 amplifier is shown in Fig 3 Protection against output short circuits is built in and the device shuts down when the dissipation becomes excessive This explains the small rise in sus tainable outpu
175. hone insert sen sor MICI temporarily to the terminal block at points TB1 2 and TB1 3 Look carefully at the microphone connecting pads The one which is connected to the metal case of the device must be taken to Using screened audio cable to connect the electret microphone to the main unit COMPONENTS Resistors R1 R2 R3 R4 See 1k 2 off 47k 2 off 3 R5 R12 220k 2 off R6 R7 470k 2 off TALK R8 10002 page R9 3909 R10 10k R11 390k R13 R15 10M 2 off R14 100k All 0 25W 5 carbon film Potentiometers VR1 470k sub min enclosed carbon preset vert 4M7 sub min enclosed carbon preset vert VR2 Capacitors C1 10 radial elect 16V C2 47u radial elect 16V C3 5n ceramic C4 22u radial elect 16V C5 22n ceramic Semiconductors 3mm red l e d 1N4148 signal diode ICL7642 quad op amp ICM7555IPA CMOS timer Miscellaneous WD1 miniature solid state buzzer 3V to 24V operation at 10mA maximum 4 way p c b screw terminal block 5mm pin spacing miniature two terminal electret microphone insert 3 5mm mono panel mounting jack socket with plug Printed circuit board available from the EPE PCB Service code 342 plastic box size 143mm x 82mm x 44mm 8 pin i c socket 14 pin i c socket battery holder and four AA size alkaline cells PP3 type battery snap or as required light duty screened wire multistrand connecting wire solder etc excluding
176. ial Perpetual Projects 2 L E D Flasher Double Door Buzzer FEATURES e Controlling Power Generation e Ingenuity Unlimited Interface Circuit Surgery e New Technology Update Net Work The Internet Page 350 DID YOU MISS THESE SEPT 01 PROJECTS e Water Monitor L E D Super Torches Synchronous Clock Driver Perpetual Projects 3 Loop Burglar Alarm Touch Switch Door Light Solar Powered Rain Alarm FEATURES e Controlling Flight Ingenuity Unlimited Practically Speaking Circuit Surgery e New Technology Update Net Work The Internet Page OCT 01 Photostats onl PROJECTS e PIC Toolkit Mk3 Camcorder Power Supply 2 Valve SW Receiver Perpetual Projects 4 Gate Sentinel Bird Scarer In Out Register FEATURES e Traffic Control Ingenuity Unlimited e New Technology Update e Circuit Surgery Interface Net Work The Internet Page Free 2 CD ROMs Microchip 2001 Tech Library NOV 01 PROJECTS e Capacitance Meter Pitch Switch e Lights Needed Alert Teach In 2002 Power Supply FEATURES e Teach In 2002 Part 1 Practically Speaking Circuit Surgery New Technology Update e Ingenuity Unlimited Net Work The Internet Page Free 16 page Supplement PIC Toolkit TK3 For Windows DEC 01 PROJECTS e Ghost Buster PIC Polywhatsit Twinkling Lights Mains Failure Alarm FEATURES e Teach In 2002 Part 2 Marconi The Father o
177. ical word phrase or abbreviation you re not familiar with simply look up the glossary included in the Manual and you ll find a comprehensive definition in plain English The Manual also covers component and equipment The most comprehensive reference work ever produced at a price you can afford the CD ROM edition of THE MODERN ELECTRONICS MANUAL provides you with all the essential information you need and provides web links to Revised CD ROM Edition of Basic Work Contains over 800 pages of information in Adobe Acrobat format Edited by John Becker Regular Supplements Additional CD ROMs each containing approximately 500 pages of additional information on specific areas of electronics will be available for 19 95 each Information on the availability and content of each Supplement CD ROM will be sent to you as they become available Presentation CD ROM suitable for any modern PC Requires Adobe Acrobat Reader which is included on the MEM CD ROM Price of the Basic Work 29 95 OFFER PRICE 24 95 POST FREE Offer ends May 31st 2002 ELECTRONICS SERVICE MANUAL PRINTED VERSION ONLY EVERYTHING YOU NEED TO KNOW TO GET STARTED IN The essential work for SAFETY Be knowledgeable about Safety Regulations Electrical Safety and First Aid e lectron ic equip me nt UNDERPINNING KNOWLEDGE Specific sections enable you to Understand Electrical e Around 900 and Electronic Principles Active and Passive Components Circuit Diagrams Circuit
178. id instability when gain is set high Capacitors C3 and C4 connected across the supply rails prevent low and high frequency instability FEEDBACK An internal negative feedback path can be accessed via pin 1 and pin 8 Bypass capacitor C5 reduces the feedback and increas es the gain of the chip from 23 to 170 times as measured samples will vary Preset potentiometer VR2 wired as a variable resistor controls the bypassing effect of C5 and enables the gain to be set within these limits Bypass capacitor C6 makes the device more immune to supply line ripple and C8 couples the output to the speaker LS1 The Zobel network formed by resistor R2 and capacitor C7 ensures that the speaker always presents a resistive load to the amplifier Without these components there is a risk of high level transients causing damage to the output transistors Tabulated power output levels for various supply voltages and speaker impedances are included below the circuit diagram Sustained operation at more than 300mW is not recommended Completed LM386N 1 circuit board 342 CIRCUIT BOARD The printed circuit board component layout wiring details and full size copper foil master pattern are shown in Fig 2 This board is available from the EPE PCB Service code 343 LM386N 1 Q 3V TO 12V SCREEN SET GAIN SET GAIN SUPPLY VOLTAGE RIPPLE REJECTION SUPPLY VOLTAGE V SIGNAL OUT TOP VIEW OF LM386N 1 Fig 1 Circuit diagram and p
179. ince the digits were only large versions of 7 segment displays reasoned the author before starting the design they could be simply driven by a PIC through a minimal bit of multiplexing No problem or so it seemed until two arrived The digits are monsters in several sens es Overall they measure 12in high 9in wide and 2 25in deep 30 5cm x 23cm x 5 5cm The angled display area is effec tively 10in high x 7in wide 25 5 x 18cm and comprises seven bright yellow hinged segments In the absence of fully informative data the first task was to establish some criteria about controlling the display segments Basically all that was known from a rudi mentary data sheet was that a pulse of 12V d c for about 0 25secs was required to turn segments on and off and that the pinouts of a built in connector were shown There was no mention of the current required although there was a warning not to con nect d c to the segments for long periods otherwise damage heating will occur The original manufacturer s name was printed on the rear of the digits Bodet D4 D3 O 1N4001 1N4001 D1 AND D2 ARE BUILT INTO DIGIT UNIT EACH COIL 439 APPROX OV Fig 1 Basic circuit for controlling one segment Fig 2 Each digit has 15 connections 12V power input and two on off con trols for each segment along with the message Made in France Doing a www google com search revealed the company at www bodet com but no elec
180. ing PICs and Keypads Software only Ice Alarm Graphics L C D Display with PICs Supp Using the LM3914 6 L E D Bargraph Drivers Multi purpose Main p c b Relay Control L E D Display PC Audio Power Meter Software only cheque PO in sterling only to Doorbell Extender Transmitter 292 Receiver 293 Trans Remote 394 HU Everyday op Rec Relay 295 pemi EPE Snug bug Heat Control for Pets APR 01 296 6 50 P ract cal E ectro n ICS l Intruder Alarm Control Panel DENAI Main Board 297 6 97 an MasterCard Amex Diners External Bell Unit 298 4 76 i E Camcorder Mixer MAY 01 299 6 34 Club Visa or Switch PIC Graphics L C D Scope 300 5 07 Hosepipe Controller JUNE 01 301 card NO sccaanononssaeoncartacsatomnesctiaetiosieimechestnineahiseiautaeinteetiadion Magfield Monitor Sensor Board 302 Dummy PIR Detector 303 K PIC16F87x Extended Memory Software only Card Exp Date Stereo Surround Sound Amplifier JULY 01 Perpetual Projects Uniboard 1 Signature Solar Powered Power Supply amp Voltage Reg MSF Signal Repeater and Indicator NOTE You can also order p c b s by phone Fax E mail or via our Repeater Board Internet site on a secure server Meter Board PIC to Printer Interface http www epemag wimborne co uk shopdoor htm Everyday Practical Electronics May 2002 379 EPE TEACH IN 2000 CD ROM The whole of the 12 part Teach In 2000 series by John Becker published in EPE Nov 99 to
181. ing from old lists For a further selection of books see the next two issues of EPE Tel 01202 873872 Fax 01202 874562 E mail dbs epemag wimborne co uk Order from our online shop at www epemag wimborne co uk shopdoor htm BOOK ORDER FORM Full NAME ocsccdcsccccedeeccacsdedecdsitcaccestaceiddonetictaeconededs PROTOSS Se EA Post code Signature assccascecsescddeesteyesccasceezaccaseehcbacceducedesocceduseeee EEE Telephone NO sch cccancicanscsaasetrencciansaemanseroneenss Please continue on separate sheet of paper if necessary Everyday Practical Electronics May 2002 the various pickups and transducers that can be fitted There are complete circuit diagrams for the major types of instrument as well as a selection of wiring modifications and pickup switching circuits These can be used to help you create your own custom wiring Along with the electric guitar sections are also included relating to acoustic instruments The function of specialised piezoelectric pickups is explained and there are detailed instructions on how to make your own contact and bridge transducers The projects range from simple preamps and tone boosters to complete active controls and equaliser units 92 pages Order code BP358 5 45 VALVE AMPLIFIERS Second Edition Morgan Jones This book allows those with a limited knowledge of the field to understand both the theory and practice of valve audio amplifier design such tha
182. ini Enigma Mar 02 is an intriguing idea from Nick Dossis but please bear in mind that your encryption is not as secure as the orig inal Enigma It is worst case figures eight times more complex than a simple substitution cipher Like the original Enigma no letter codes to itself so for each of the first eight characters there are 25 possible resulting encryptions these eight being the maximum codeword length This gives rise to 258 possibilities Daunting per haps but not outside the scope of modern com puting equipment The example BYEBYE only appears to have no repetition as the codeword in your article is four characters ABCD If instead a 3 character codeword was applied then repetition would be immediately apparent bad news for attempted secrecy I found a software emulation of the original machine on the Internet at www ugrad cs jhu edu russell classes enigma Godfrey Manning Edgware Middlesex via email Hello again Godfrey You are reading more into Nick s design than you should Don t you recall passing coded messages on paper between Everyday Practical Electronics May 2002 The technique has been used in vibration condition monitoring and it removes the need for the analyst to predict the maximum fre quency of interest in a signal and thus removes the need to predict the maximum sampling frequency nor does the analyst need to consider filtering which could inadvertent ly filter out th
183. inkling Lights DEC 01 Ginormous Stopwatch Part 1 246 7 82 Ghost Buster ae Ginormous Stopwatch Part 2 DEC 99 PIC Pol ais igi ywhatsit Digital Giant Display 247 7 85 Analogue Serial Port Converter 248 3 96 Forever Flasher JAN 702 330 pol ued asi 4 44 1 time Delay Touch Switch 331 Scratch Blanker JAN a PIC Magick Musick 332 Flashing Snowman Multi project PCB 932 3 00 Versatile Bench Power Suppl 333 Video Cleaner FEB 00 251 5 63 xk PIC Spectrum Analyser FEB 02 334 7 13 Find It 252 4 20 Versatile Current Monitor 335 4 75 x Teach In 2000 Part 4 253 4 52 Guitar Practice Amp 336 5 39 High Performance 254 255 PIC Virus Zapper MAR ey 337 Regenerative Receiver 256 RH Meter 338 EPE Icebreaker PCB257 programmed PIC Mini Enigma Software only PIC16F877 and floppy disc Set only Programming PIC Interrupts Software onl Parking Warning System 258 K PIC Controlled Intruder Alarm APR 02 Micro PICscope APR 00 259 4 99 x PIC Big Digit Display MAY 174 Garage Link Transmitter 261 Washing Ready Indicator Receiver 262 sSet 5 87 Audio Circuits 1 LM386N 1 Versatile Mic Audio Preamplifier MAY 00 TDA7052 PIR Light Checker TBA820M x Multi Channel Transmission System Transmitter LM380N Receiver TDA2003 Interface Twin TDA2003 x Canute Tide Predictor JUNE 00 3 05 K PIC Gen Frequency Generator Counter JULY
184. inout details for the LM386N 1 Power Amplifier LM386N 1 POWER AMPLIFIER R M S power output just before the onset of waveform clipping Speaker Supply Voltage Impedance ohms 3V 4 5V 6V 9V 12V 4 60mW 150mW 320mW 500mW 8 26mW 105mW 200mW 560mW 900mW 16 15mW 6OmW 110mW 320mW 605mW 32 35mW 62mW 170mW 330mW Quiescent current 6mA Input resistance 50k ohms Input sensitivity for 560mW output 8 ohm load 9V supply a VR2 set for maximum resistance b VR2 set for minimum resistance Absolute maximum supply voltage 90mV r m s gain 23 12mV r m s gain 170 beyond which damage will occur 15V Suggested maximum supply voltage with a 4 ohm speaker 6V Frequency response up to 300kHz Everyday Practical Electronics May 2002 POWER SUPPLY VE COMPONENTS LM386N 1 AMPLIFIER SCREENED INPUT LEAD Resistors 1 470Q All 0 25W 5 carbon film R2 100 Potentiometers VR1 10k min rotary carbon log VR1 FRONT VIEW VR2 10k enclosed carbon preset Capacitors 4u7 radial elect 25V 1n disc ceramic 220u radial elect 25V 2 off 100n disc ceramic 10u radial elect 25V 2 off 47n polyester POWER SUPPLY VE TO SPEAKER LS1 2 OIN 50 8mm Semiconductor IC1 LM386N 1 audio power amp i c Miscellaneous LS1 4 to 32 ohm loudspeaker see text Printed circuit board available from the EPE PCB Service code 343 LM386N 1 case optional size and type to c
185. ity BACK ISSUES CD ROM VOL 3 Please send me quantity BACK ISSUES CD ROM VOL 5 l l l l l l l Price 12 45 each includes postage to anywhere in the world _ Please charge my Visa Mastercard Amex Diners Club Switch D aonar hoe es eee oe eee ee een eee ee ee ees Card No Expiry Date cos aac dane ee ears ed Switch Issue No l l l l l l l i SEND TO Everyday Practical Electronics l Wimborne Publishing Ltd 408 Wimborne Road East Ferndown Dorset BH22 9ND Tel 01202 873872 Fax 01202 874562 l E mail orders epemag wimborne co uk 1 Payments must be by card or in Sterling cheque or bank I draft drawn on a UK bank l Normally supplied within seven days of receipt of order l Send a copy of this form or order by letter if you do not wish to i cut your issue READOUT E mail editorial epemag wimborne co uk wohn Becker addresses some of the general points readers have raised Have you anything interesting to say Drop us a line WIN A DIGITAL MULTIMETER A 31 digit pocket sized I c d multime ter which measures a c and d c volt age d c current and resistance It can also test diodes and bipolar transistors Every month we will give a Digital Multimeter to the author of the best Readout letter x LETTER OF THE MONTH x ANALYSING NYQUIST Dear EPE I read with interest the email from Mr Nick de Smith in EPE March 02 concerning the PIC
186. ks at the voltages applied to its inverting and non inverting inputs pin 6 and R8 D2 1000 IN4148 a k LINK SEE TEXT VR2 4M7 HOLD OFF TIME pin 5 respectively If the voltage at pin 5 exceeds that at pin 6 the op amp will be on with the output pin 7 high Otherwise it remains low The signal provided by the output of the audio amplifier ICla pin 1 is applied direct to IC1b inverting input pin 6 A certain preset voltage is applied to the non inverting input pin 5 by the potential divider network made up of R6 VR1 R7 Preset potentiometer VRI will be adjusted at the end so that the voltage at pin 5 is slightly lower than that at pin 6 that is less than 3V when no vibration is detected The state of the level detector output pin 7 will therefore be low when no vibration exists Fixed resistors R6 and R7 narrow the range of adjustment of VR1 to the middle one third of the voltage range nominally 2V to 4V and this simplifies setting up at the end RAPID SWITCHING When vibration is detected the voltage at IClb pin 6 rises on the positive half cycles and falls on the negative ones The former have no effect However on the negative excursions the voltage at pin 6 will fall below that at Fig 2 Complete circuit diagram for the Washing Ready Indicator The battery pack B1 is made up of 4 x AA alkaline cells Everyday Practical Electronics May 2002 357 pin 5 and this will r
187. l gap as indicated in Fig 7 13 Again a disc that has alternating trans parent and opaque areas is used The sensor is mounted at the edge of the disc so that the light beam is interrupted when the disc rotates Another name given to this type of sensor is a photointerrupter TRANSPARENT SECTION OF DISC PHOTOTRANSISTOR Fig 7 13 Slotted photosensor Reflective optosensors These also have a built in l e d and phototransistor but which are mounted side by side on one side of the disc only which does not need to be transparent Light is reflected back to the phototransistor by a reflective sur face placed close to the sensor as shown in a1 lamps so precautions Table 7 2 Data for the SG 2BC Reflective must still be taken to Photointerrupter reduce ambient light as much as possible Parameter Value A typical circuit for L E D Forward Voltage I 4mA 1 2V max Len H gt sor is shown in Peak Wavelength 940nm Fis 715 wh the Phototransistor Collector Dark Current 0 1uA PHOTOTRANSISTOR oa he i pe pene Light Current diode current 4mA 100uA via resistor R1 the Leakage Current 0 1uA REFLECTIVE value of which depends ls Ogee lg 00 aous SURFACE 7 on the required current iE for th P d tvvicall Falltime as above 30us or the l e d typically Collector Current 20mA max SmA to 20mA The Collector emitter Voltage 30V max phototransistor can be Emitter collector Voltage 3V max used with its collector connec
188. l stereo mixer Dynamic noise limiter DNL Automatic audio fader Video faders Video wipers Video crispener Mains power supply unit 109 pages Order code BP356 5 45 SETTING UP AN AMATEUR RADIO STATION I D Poole The aim of this book is to give guidance on the decisions which have to be made when setting up any amateur radio or short wave listening station Often the experience which is needed is learned by one s mistakes however this can be expensive To help overcome this guidance is given on many aspects of setting up and running an effi cient station It then proceeds to the steps that need to be taken in gaining a full transmitting licence Topics covered include The equipment that is needed Setting up the shack Which aerials to use Methods of construction Preparing for the licence An essential addition to the library of all those taking their first steps in amateur radio 86 pages Order code BP300 4 45 EXPERIMENTAL ANTENNA TOPICS H C Wright Although nearly a century has passed since Marconi s first demonstration or radio communication there is still research and experiment to be carried out in the field of antenna design and behaviour The aim of the experimenter will be to make a measure ment or confirm a principle and this can be done with relatively fragile short life apparatus Because of this devices described in this book make liberal use of card board cooking foil plastic bottles cat f
189. le through the STATUS word As an aside and as I ve said before it s been a revelation starting to read EPE again keep up the good work and don t change any of it Let me also put in a good word for BBC Basic for Windows not just because it s developed by a fellow licensed radio amateur Limitations it has just as with any language but its use must not be underestimated and its new lease of life under Windows is a boon At its quoted price it s also excellent value Godfrey Manning G4GLM Thanks Godfrey for your continued apprecia tive interest in us Malcolm Wiles replies to your question Reference to the PIC data sheets will show that the Bank select bits RPO and RP1 are phys ically part of the STATUS register bits 5 and 6 respectively So their setting on entry to the ISR is preserved along with Z C DC TO PD and IRP when the STATUS register is saved by the SWAPF STATUS W MOVWF SAVES sequence at the beginning of the ISR After that has been done the ISR can safely change any of these flags because they will all be reinstated to the values they had on entry to the ISR by the POP SWAPF SAVES W MOVWE STATUS instructions at the end of the ISR This reinstatement includes the values of RPO and RP1 so at this point Bank 1 will again be selected if it was the setting on entry to the ISR Clearly the ISR must not subsequently contain any code which depends on Bank or other STA TUS register fla
190. length before testing the system IC8 RA3 UNDERSIDE VIEW LOOKING AT PINS ERROR Fig 10 Connections to a 36 way D type Centronics female connector used in conjunction with a standard PC parallel port cable Everyday Practical Electronics May 2002 connector PIN FUNCTION ARROW ON CONNECTOR DENOTES PIN 1 y 15 0 06000000 0 i 16 0O O O O O O 0 0 2 VIEW LOOKING INTO 16 WAY CONNECTOR Fig 12 Pinouts for the connector mounted as part of the digit assembly DIGIT WIRING Monstrous is again a term that can be used in respect of the digit connection requirements The digits need to be wired in parallel back to the control board However although the manufacturers have provided a single connector on each digit this only allows for one set of the 15 con nection wires needed One would have expected two connec tors one for the cable harness arriving from the control board another for the har ness that then has to be connected to the next digit The author offers no recommendations about using the digits own connector although for the sake of good order its pinouts are shown in Fig 12 It was decided that it was easier to hard wire the connections to solder pads at var ious positions on the back of the digits They are the pads to which the manufac turer s rectifier diodes mounted inside the digit box are soldered The correct con nection points were found experimentally and are shown in Fig
191. ll Specifications View our web site at TEL 44 0 1702 527572 FAX 44 0 1702 420243 PLALALA 1 MANAR Ae Everyday Practical Electronics May 2002 349 TICAL Bec RONUES ELECTRONICS TODAY INTERNATIONAL We can supply back issues of EPE by post most issues from the past three years are available An EPE index for the last five years is also available see order form Alternatively indexes are published in the December issue for that year Where we are unable to provide a back issue a photostat of any one article or one part of a series can be purchased for the same price Issues from Jan 2001 onwards are also available to download from www epemag com JAN 01 PROJECTS e Versatile Optical Trigger UFO Detector and Event Recorder Two Way Intercom PIC Monitored Dual PSU Part 2 FEATURES e Using PICs and Keypads e The Schmitt Trigger Part 3 New Technology Update e Circuit Surgery Practically Speaking Ingenuity Unlimited e CIRSIM Shareware Review Net Work The Internet PROJECTS e Ice Alert Using LM3914 6 Bargraph Drivers Simple Metronome e PC Audio Power Meter FEATURES e The Schmitt Trigger Part 4 Ingenuity Unlimited e Circuit Surgery New Technology Update Net Work The Internet Free 16 page supplement How To Use Graphics L C D s With PICs MAR 01 PROJECTS e Doorbell Extender Body Detector e DIY Tesla Lightning Circuit Tester FEATURES e Understan
192. lowing prefix to name but a few 2N 2SA 2SB 2SC 2SD 2P 2SJ 2SK 3N 3SK 4N 6N 17 40 AD ADC AN AM AY BA BC BD BDT BDV BDW BDX BF BFR BFS BFT BFX BFY BLY BLX BS BR BRX BRY BS BSS BSV BSW BSX BT BTA BTB BRW BU BUK BUT BUV BUW BUX BUY BUZ CA CD CX CXA DAC DG DM DS DTA DTC GL GM HA HCF HD HEF ICL ICM IRF J KA KIA L LA LB LC LD LF LM M M5M MA MAB MAX MB MC MDAJ MJE MJF MM MN MPS MPSA MPSH MPSU MRF NJM NE OM OP PA PAL PIC PN RC S SAA SAB SAD SAJ SAS SDA SG SI SL SN SO STA STK STR STRD STRM STRS SV1 T TA TAA TAG TBA TC TCA TDA TDB TEA TIC TIP TIPL TEA TL TLC TMP TMS TPU U UA UAA UC UDN ULN UM UPA UPC UPD VN X XR Z ZN ZTS many others We can also offer equivalents at customers risk We also stock a full range of other electronic components Mail phone Fax Credit Card orders and callers welcome Cricklewood Electronics Ltd 40 42 Cricklewood Broadway London NW2 3ET Tel 020 8452 0161 Fax 020 8208 1441 Everyday Practical Electronics May 2002 GOULD OS300 Dual Trace 20MHz Tested with Manual OSCILLOSCOPES TEKTRONIX TDS350 dual trace 200MHz 1G S Unused 1500 TEKTRONIX TDS320 dual trace 100MHz 500M S TEKTRONIX TDS310 dual trace 50MHz 200M S LECROY 9400A dual trace 175MHz 5G S HITACHI VC6523 d trace 20MHz 20M S delay etc Unused 600 PHILIPS PM3092 2 2 ch 200MHz delay etc 800 as new 950 PHILIPS PM3082 2 2 ch 100MHz delay etc 700 as new 800 TEKTRONIX TAS465 dual trace 100MHz delay etc 750
193. m x 70mm 50mm x 5mm shaft 12A continuous rating thermal protected 22 Ref MGM1 SOLID STATE RELAYS P C B mounting these relays require 3 32V d c to operate but will switch up to 3A a c mains Pack of 4 5 Ref SPEC1B 12V RELAYS 2 x 2 c o 16A contacts p c b mount will fit Vero tray of 25 relays for just 9 95 Ref SPEC1 VENNER TIME CONTROLS Designed to be wired in permanent ly they will switch up to 16A 240V a c motorised with dial and pins New and boxed 15 Ref VTS GYROSCOPES We siill sell original 1917 design hours of fun for all the family complete with stand string box and info 6 Ref EP70 INNOVATIONS We also sell a wide range of innovative products for the home these are at www seemans com INVERTERS Convert 12V d c into 240V mains modified sine wave 300 watt 150 watt continuous 59 95 Ref VER3 600 watt model 330 watt continuous 79 97 Ref VER4 10 WATT SILICON SOLAR PANEL 10 year life waterproof 365mm x 365mm x 26mm 14V 10W 1 8kg framed 84 99 Ref PAN BULL ELECTRICAL UNIT D HENFIELD BUSINESS PARK HENFIELD SUSSEX BN5 9SL TERMS CASH PO OR CHEQUE WITH ORDER PLUS 5 00 P amp P UK PLUS VAT 24 HOUR SERVICE 7 50 UK PLUS VAT OVERSEAS ORDERS AT COST PLUS 3 50 ACCESS VISA SWITCH ACCEPTED phone 01273 491490 Fax 491813 Sales bull electrical com STICKY LABELS Small address labels etc are very useful and can be ordered online at www stickon co uk
194. mail We can also supply issues from earlier years 1998 except Jan to May July Nov Dec 1999 2000 except Feb July 2001 except Oct Where we do not have an issue a photostat of any one article or one part of a series can be provided at the same price ORDER FORM BACK ISSUES PHOTOSTATS INDEXES L Send back issues dates L Send photostats of article title and issues date L Send copies of last five years indexes 3 30 for five inc p amp p Overseas 3 80 surface 5 25 airmail L_ 1 enclose cheque P O bank draft to the value of L_ Please charge my Visa Mastercard Amex Diners Club Switch Card No Card Expiry Date SEND TO Everyday Practical Electronics Wimborne Publishing Ltd 408 Wimborne Road East Ferndown Dorset BH22 9ND Tel 01202 873872 Fax 01202 874562 E mail orders epemag wimborne co uk On line Shop www epemag wimborne co uk shopdoor htm Payments must be in sterling cheque or bank draft drawn on a UK bank Normally supplied within seven days of receipt of order Send a copy of this form or order by letter if you do not wish to cut your issue Everyday Practical Electronics May 2002 STORE YOUR BACK ISSUES ON MINI CD ROMS VOL 1 CONTENTS BACK ISSUES November 1998 to June 1999 all the projects features news Us etc from all eight issues Note No advertisements are included PIC PROJECT CODES All the available codes for the PIC based project
195. mal entry is 3 although concessions for wheelchair dis abled and children will be priced at 2 50 For more information contact Brian Cannon G8DIU 38 Sandringham Road Worcester Park Surrey KT4 8UJ Tel 020 833 0092 10am 6pm Mon Fri Fax 01737 279108 24 hours Email Brian Cannon btinternet com MAPLIN S C3 CAT MAPLIN Electronics have introduced a mini variant of their large paper based cat alogue It is free and is described as being their new specialist catalogue focusing on their most popular lines from the world of components cables and connectors The C3 is said to contain all the essential items for your hobbyist projects or commercial applications David O Reilly Maplin s Marketing Director says I would like to draw your attention to a number of new features first ly the extended price breaks for volume enquires plus the launch of our new information centre which will help you with some key technical principles and cal culations for your specific application For more information contact Maplin Electronics through any one their nation wide stores or telephone 0870 264 6000 Fax 0870 264 6001 Email customerservice maplin co uk Web www maplin co uk Everyday Practical Electronics May 2002 R F SOLUTIONS aiiis RADIO communications modules in various forms are at the heart of the prod uct range for R F Solutions Ltd Their latest catalogue consists of 70 A4 size pa
196. mand Different views are available the component side of course plus an X ray mode and a solder side flipped view The views are zoomable and usefully a Components List can be created and printed from the board design 360 Tea i N i I a T i F 7 f F a i TEET T bE EEE Es LES ETETETT O Eley J Hm lel p Top view of a small sample board created in Lochmaster 2 0 New pages can be added to a project design each page having its own tab A very handy feature is the Test command which liter ally highlights a route taken by a conductor throughout the board including wire jumper links but not through components You can therefore reveal a path of interconnections to prevent unwanted short circuits to other components or strips You still need rather an agile mind to create stripboard layouts but this technique will suit many electronics enthusiasts absolute ly fine Lochmaster 2 0 is available direct from Abacom for 35 28 about 22 or US 30 Scale ar iitam Scale Assistant part of the Front Designer package creates complex scales for rotary controls Front Line Also worth checking out is Abacom s Front Designer package for drafting front panel layouts for your projects Amongst other things its Scale Assistant helps with the divisional markings for those pesky rotary switches and volume controls You can then print out the final design onto
197. mentals of fibre optic technology through cable manufacture to connectors transmitters and receivers Order Code VT501 VT502 57 minutes Laser Technology A basic introduction covering some of the common uses of laser devices plus the operation of the Ruby Rod laser HeNe laser CO gas laser and semiconductor laser devices Also covers the basics of CD and bar code scanning Order Code VT502 Each video uses a mixture of animated current flow in circuits plus text plus cartoon instruc tion etc and a very full commentary to get the points across The tapes are imported by us and originate from VCR Educational Products Co an American supplier We are the worldwide distributors of the PAL and SECAM versions of these tapes All videos are to the UK PAL stan dard on VHS tapes unless you specifically request SECAM versions Everyday Practical Electronics May 2002 PROJECT TITLE Order Code Lead Acid Battery Charger AUG 01 Shortwave Loop Aerial PCB SERVICE Scat L E D Flasher Double Door Buzzer Printed circuit boards for most recent EPE constructional projects are available from P foal Proiects Unibeard 4 the PCB Service see list These are fabricated in glass fibre and are fully drilled and pee lee awed roller tinned All prices include VAT and postage and packing Add 1 per board for Loop Burglar Alarm Touch Switch Door Light airmail outside of Europe Remittances should be sent to The PCB Service and
198. n lengths The TDA2003 incorporates short circuit and overload protection and is extremely rugged It will deliver a worthwhile output at modest supply voltages and the suitability of car batteries as a power source may make it of particular interest to some readers The SCREENED INPUT LEAD of 25mm x 0 4mm lin x 4in brass strip Make two shallow cuts 5mm 16in apart close to the centre and bend out a tag which can be soldered to the relevant pins of the i c Thin brass strip can be pur chased from almost all model shops circuit diagram of a single chip TDA2003 audio amplifier is given in Fig 9 Grounding the input pin 1 of this device would upset the internal biasing arrangements so a second blocking capacitor C2 must be provided The high POWER SUPPLY VE POWER SUPPLY VE TO SPEAKER LS1 3 4IN 86 4mm Fig 10 Printed circuit board component layout full size foil master and off board wiring for the single TDA2003 Amplifier Everyday Practical Electronics May 2002 COMPONENTS TDA2003 AUDIO AMPLIFIER Resistors 39Q 22002 202 1Q All 0 25W 5 carbon film Potentiometers VR1 10k rotary carbon log Capacitors Ci C2 4u7 radial elect 50V 2 off C3 220u radial elect 50V C4 100n disc ceramic C5 39n polyester C6 470u radial elect 50V C7 1000u radial elect 50V C8 100n polyester Semiconductor IC1 TDA2003 audio power amp i c Miscell
199. n be drawn up Perfect Marks Always check the final layout to make sure you have not overlooked some thing When you are sure everything is correct transfer the layout to the front panel but take due care when doing this Most project cases are made from soft plastics or aluminium that is easily worked but they are also easily chipped and scratched Mark the drilling points using some thing like a fibre tip pen that will not scar the case for life It is advisable not to use spirit based inks on plastic pan els The spirit in the ink might dissolve and seriously damage the case If in doubt try the pen on the inner surface of the panel where any damage will be of no consequence Very soft pencils about 5B or 6B work well on alumini um panels and should not cause any damage The lines can be removed using an ordinary eraser Some plastic panels are resistant to virtually all inks One option is to scratch the design onto the panel mak ing sure you only place marks in areas that will be cut or drilled away The more popular option is to fix paper onto the panel with double sided tape or a Pritt Stick This method is quite a good one using any case since it is easy to mark the layout very accurately and the paper gives some protection to the panel The paper is peeled off once work on the panel has been completed and any adhesive or paper that remains is easily washed off Use a centre punch to mark the cen tres
200. n Brown PhyzzyB COMPUTERS BONUS ARTICLE 2 Creating an Event Counter By Clive Max Maxfield and Alvin Brown INTERGRAPH COMPUTER SYSTEMS 3D GRAPHICS A chapter from Intergraph s book that explains computer graphics technology in an interesting and understandable way with full colour graphics EXTRA ARTICLE ON VOL 1 amp 2 THE LIFE amp WORKS OF KONRAD ZUSE a brilliant pioneer in the evolution of computers A bonus article on his life and work written by his eldest son including many previously unpublished photographs NOTE These mini CD ROMs are suitable for use on any PC with a CD ROM drive They require Adobe Acrobat Reader available free from the Internet www adobe com acrobat Everyday Practical Electronics May 2002 A great way to buy EPE Back Issues our mini CD ROMs contain back issues from our EPE Online website plus bonus articles all the relevant PIC software and web links Note no free gifts are included All this for just 12 45 each including postage and packing 1 2 45 each including VAT Order on line from www epemag wimborne co uk shopdoor htm or www epemag com USA prices or by phone Fax E mail or Post BACK ISSUES MINI CD ROM ORDER FORM l l l Please send me quantity BACK ISSUES CD ROM VOL 1 I Please send me quantity BACK ISSUES CD ROM VOL 2 l 1 Please send me quantity BACK ISSUES CD ROM VOL 3 l Please send me quant
201. n of mono dispersed particles The resultant layer of titanium dioxide is very porous and has a high surface area This allows the distribu tion of dye molecules into the titanium dioxide The layer is heat treated to enable the resistivity of the film to reduce to a suffi ciently low level to ensure resistance loss es are within accept able limits Then the electrode with the oxide layer is immersed in the dye solution for several hours The porous oxide absorbs the dye very efficiently giving an intense colour to the film The dye coated elec trode is put together with another conduct ing glass electrode and the space between them is filled with an organic electrolyte This second glass plate has a reflecting platinum plate to ensure light reaching it is reflected back into the cell After making provision for the electrical contacts with the two electrodes the assembly is sealed Greater Efficiency The absorption of light using only a sin gle molecular thickness of dye would be very low if it was not for the construction technique used The fact that a very rough porous structure is used instead allows for much greater levels of efficiency to be achieved because there is a far higher sur face area presented to the light A further advantage is gained from the fact that the semiconductor structure is nano crystalline and this spreads the light over the whole area further increasing the efficiency It might be tho
202. nce Resistor R2 provides suffi cient current for the Zener diode to reach its Zener voltage Build the circuit on your breadboard and connect the Picoscope to the op amp s out put You should be able to see the output change state when the light level changes sufficiently for the voltage at the op amp s non inverting input pin 3 to cross the ref erence threshold voltage at the inverting input pin 2 Use the Picoscope on a small sampling interval and see if the output changes like that shown in Fig 7 19 This rapid changing of state at the switching point is obviously not a good thing 513 Fig 7 18 Comparator circuit without hysteresis Fig 7 19 Typical noisy output from circuit in Fig 7 18 Now modify the circuit in Fig 7 18 to become that in Fig 7 20 and repeat the above experiments The multiple switching should have disappeared see Fig 7 21 You should also notice that the point at which the output changes state will be dif ferent when the light level increases to that when it decreases this is due to the hys teresis now introduced by the inclusion of resistors R3 and R4 Fig 7 20 Comparator circuit with hysteresis Fig 7 21 Typical clean switching output from circuit in Fig 7 20 You can vary the amount of hysteresis by changing the values of these resistors as described in this month s tutorial section Try increasing R4 to IMQ and then R3 to 100kQ2 and see the difference You
203. nders or where to get kits or plans to build my own units The parameters I am interested in are barometric pressure min max temperature including windchill wet bulb thermometer wind speed direction rain fall humidity I plan to download this info say every six hours into a datalogger if feasible or direct to PC and would also want the results out put as graphs I am also busy setting up to capture images from satellite to show what the sky is doing Maybe there are future articles planned I really enjoy reading the mag Albin Draper via email Well Albin my Met Office weather station was published in EPE issues Dec 95 Jan 96 However I am working on a_ sophisticated update for publication later this year PIC con trolled complete with logger and PC interface It will do all you mention except windchill which Id not thought about but might look into Wind sensing will be solid state I regret that I don t know of commercial sources although a general search via the web may help you No we ve nothing astronomical in the pipeline PiCtutor AND TK3 Dear EPE I recently bought a PlCmicro development board and the PIC Toolkit TK3 V1 1 I was under the impression that with these two I would be able to program the PICMicro on the board and run my own programs I also have Windows 2000 When I got the CD it told me that the Toolkit will not run on Windows 2000 and it also seems that I need to order more soft
204. ndown Dorset BH22 9ND We do not accept sub Your ideas could earn you some cash and a prize INGENUITY UNLIMITED WIN A PICO PC BASED OSCILLOSCOPE WORTH 586 100MS s Dual Channel Storage Oscilloscope Multimeter Frequency Meter If you have a novel circuit idea which would be PC based oscilloscope could be yours Every 12 months Pico Technology will be awarding an ADC200 100 digital storage oscilloscope for the best IU submission In addition a DrDAQ Data Logger Scope worth 69 will be presented to the runner up Ls TEk BE INTERACTIVE VOLS IU is your forum where you can offer other readers y Airi j the benefit of your Ingenuity Share those ideas earn x sy ha ir some cash and possibly a prize Ti EW pW p iy Binti AW 121 UNIPOLAR FOUR PHASE STEPPER MTOR Fig 2 Emergency Light circuit diagram Everyday Practical Electronics May 2002 SPECIAL OFFERS TEKTRONIX 2445A Se amp e 4 ch 150MHz delay Ei cursors etc Supplied ETET with 2 Tektronix probes ak 6 2 8 on E gt TEKTRONIX 2232 Digital Storage Scope Dual Trace 100MHz 100M S with probes H P 54501A Dig Oscilloscope 100MHz 4 Ch H P 3312A Function Gen 0 1Hz 13MHz AM FM Sweep Tri Gate Brst etc 300 FARNELL Dual PSU XA35 2T 0 35V 0 2A Twice QMD I c d Display 18 CIRRUS CRL254 Sound Level Meter with Calibrator 80 120dB LEQ 15 EDDYSTONE 1002 Receiver 150kHz 30MHz Brooadcast F
205. ne Publishing Ltd 408 Wimborne Road East Ferndown Dorset BH22 9ND Tel 01202 873872 Fax 01202 874562 Email subs epemag wimborne co uk Also via the Web at http www epemag wimborne co uk Subscriptions start with the next available issue We accept MasterCard Amex Diners Club Switch or Visa For past issues see the Back Issues page BINDERS Binders to hold one volume 12 issues are available from the above address These are finished in blue p v c printed with the magazine logo in gold on the spine Price 5 95 plus 3 50 p amp p for overseas readers the postage is 6 00 to everywhere except Australia and Papua New Guinea which cost 10 50 Normally sent within seven days but please allow 28 days for delivery more for overseas Payment in sterling only please Visa Amex Diners Club Switch and MasterCard accepted Send fax or phone your card number and card expiry date with your name address etc Or order on our secure server via our UK web site Overseas customers your cred it card will be charged by the card provider in your local currency at the existing exchange rate Editor MIKE KENWARD Deputy Editor DAVID BARRINGTON Technical Editor JOHN BECKER Business Manager DAVID J LEAVER Subscriptions MARILYN GOLDBERG Administration FAY KENWARD Editorial Admin 01202 873872 Advertisement Manager PETER J MEW Frinton 01255 861161 Advertisement Copy Controller PETER SHERIDAN 01202 87
206. ng Repair techniques are also illustrated throughout A large reference section provides a range of infor mation compiled from many contemporary sources and includes specialist dealers for valves components and complete receivers 288 pages Order code NE34 20 99 LOUDSPEAKERS FOR MUSICIANS Vivan Capel This book contains all that a working musician needs to know about loudspeakers the different types how they work the most suitable for different instruments for cabaret work and for vocals It gives tips on constructing cabinets wiring up when and where to use wadding and when not to what fittings are available finishing how to ensure they travel well how to connect multi speaker arrays and much more Ten practical enclosure designs with plans and comments are given in the last chapter but by the time you ve read that far you should be able to design your own Order code BP297 5 49 381 164 pages
207. ng from scratch using PIC16F84 e Start by lighting l e d s and do 30 tutorials to Sound Generation Data Display and a Securit System e PIC TUTOR Board with Switches I e d s and on board programmer PIC TUTOR BOARD KIT Includes PIC16F84 Chip TOP Quality PCB printed with Component Layout and all components not ZIF Socket or Displays Included with the Magenta Kit is a disk with Test and Demonstration routines KIT 870 27 95 Built amp Tested 42 95 Optional Power Supply 3 99 ZIF Socket 9 99 LCD Display 7 99 LED Display Reprints Mar Apr May 98 3 00 set 3 SUPER PIC PROGRAMMER e READS PROGRAMS AND VERIFIES e WINDOWS SOFTWARE e PIC16C6X 7X AND 8X e USES ANY PC PARALLEL PORT e USES STANDARD MICROCHIP HEX FILES e OPTIONAL DISASSEMBLER SOFTWARE EXTRA e PCB LEAD ALL COMPONENTS TURNED PIN 29 99 SOCKETS FOR 18 28 AND 40 PIN ICs e SEND FOR DETAILED Kit 862 Power Supply 3 99 DISASSEMBLER 11 75 INFORMATION A SUPERB PRODUCT AT AN UNBEATABLE LOW SOFTWARE PIC STEPPING MOTOR DRIVER Kit 863 18 99 PRICE FULL SOURCE CODE SUPPLIED ALSO USE FOR DRIVING OTHER POWER DEVICES e g SOLENOIDS INCLUDES PCB PIC16F84 WITH DEMO PROGRAM SOFTWARE DISC INSTRUCTIONS AND MOTOR Another NEW Magenta PIC project Drives any 4 phase unipolar motor up to 24V and 1A Kit includes all components and 48 step motor Chip is pre programmed with demo softwa
208. nputs read 0 4V Four TTL CMOS compatible digital input outputs ADC conversion time lt 10uS Software C QB amp Win extended D shell case amp all compo nents except sensors amp cable provided 3118KT 52 95 LIQUID LEVEL SENSOR RAIN ALARM Will indi cate fluid levels or simply the presence of fluid Relay output to control a pump to add remove water when it reaches a certain level 1080KT 5 95 AM RADIO KIT 1 Tuned Radio Frequency front end single chip AM radio IC amp 2 stages of audio amplification All components inc speaker provid ed PCB 32x102mm 3063KT 10 95 DRILL SPEED CONTROLLER Adjust the speed of your electric drill according to the job at hand Suitable for 240V AC mains powered drills up to WEB http www QuasarElectronics com email epesales QuasarElectronics com SURVEILLANCE High performance surveillance bugs Room transmitters supplied with sensitive electret microphone amp battery holder clip All transmit ROOM SURVEILLANCE MTX MINIATURE 3V TRANSMITTER Easy to build amp guar anteed to transmit 300m 3V Long battery life 3 5V operation Only 45x18mm B 3007KT 6 95 AS3007 11 95 MRTX MINIATURE 9V TRANSMITTER Our best selling bug Super sensitive high power 500m range 9V over 1km with 18V supply and better aerial 45x19mm 3018KT 7 95 AS3018 12 95 HPTX HIGH POWER TRANSMITTER High performance 2 Stage transmitter gives N greater stability amp higher qual
209. ntroller the design uses only five i c s The probes and contact pads used are those sold inexpensively by major chemists for use with proprietary TENS pain relief machines It can also be used as a handheld unit without a PC In this role an I c d shows the heart rate as a graphical waveform and provides a beats per minute count plus a real time pulse beat via a flashing asterisk The Biopic s PC software is written in QBasic but is self contained and does not require QB itself to be installed It can be run in DOS mode or under Windows 3 1 95 98 and ME WORLD LAMP THE quest for a battery powered lamp for lighting in poorer areas has presented an interesting and important design challenge for many years Such a lamp should ideally be cheap simple efficient and flexible all at the same time With this in mind the authors have designed a lamp that is made from inexpensive readily available stock parts and runs off a nominal 12V d c supply This is converted to a p w m pulse width modulated a c supply which will power any ordinary fluorescent lamp between 100mW and 15W It will power the equivalent of a GOW incandescent lamp for about 80 hours off a standard 12V car battery and can provide low cost lighting whenever or wherever there s no mains supply available FREQUENCY STANDARD GENERATOR A high precision selectable 1kHz to 100kHz frequency source derived from BBC Radio Four s transmission signal whi
210. nts to preset VR1 as required In some cases it will not be found neces sary for the sensor to touch the washing machine at all just placed close enough for it to pick up the noise However if doing this you may need to set the sensi tivity somewhat higher and this may make the unit more susceptible to the pick up of stray random noise Make some tests under real operating conditions Adjust preset VR2 for a suit able hold off time so that the buzzer is pre vented from operating under all silent conditions on all washing programs When satisfied about all aspects of operation cut the jumper wire on the p c b to prevent the l e d operating Happy washday 359 SURFING THE INTERNET rs NET WORK ALAN WINSTANLEY wre to Net Work our monthly column written for Internet users Have you visited our web site at www epemag wim borne co uk recently You can view a summary of all issues of EPE dating back several years with colour photographs and indexes of projects also available together with any Please Take Note correc tions for that year You can buy back issues books CD ROMs videos and p c b s online via our online shop shopdoor htm You can also download copies of the magazine from www epemag com our Online issue priced in US dollars Our Chat Zone message board is proving to be increasingly popular and is an easy way of posting plain text messages into a forum where you can communicate with o
211. o otherwise efficiency is compromised Once the stepper motor s common lead or leads have been identi fied the others can be identified through trial and error First take the common lead s to one terminal of the transformer s primary wind ings and try combinations of two wires on the other terminal until the tube lights up Then connect the remaining wires To obtain a good level of light for shorter term use consider using gears on the motor to avoid the need for any undue exertion 338 INGENUITY 2 UNLIMITED Our regular round up of readers own circuits We pay between 10 and 50 for all material published depending on length and technical merit We re looking for novel applications and circuit designs not simply mechanical electrical or software _ ideas Ideas must be the reader s own work and must not have been submitted for publication elsewhere The circuits shown have NOT been proven by us ngenuity Unlimited is open to ALL abilities but items for consideration in 50MHz Spectrum Analyser this column should be typed or word processed with a brief L circuit description between 100 and 500 words maximum and Signal Generator full circuit diagram showing all relevant component values Please draw all circuit schematics as clearly as possible of use to other readers then a Pico Technology Send your circuit ideas to Alan Winstanley Ingenuity Unlimited Wimborne Publishing Ltd 408 Wimborne Road East Fer
212. o electronics amp circuit analysis 7 LED s simulate dice roll slow down amp land on a number at random 555 IC circuit 3003KT 9 95 STAIRWAY TO HEAVEN Tests hand eye co ordi nation Press switch when green segment of LED lights to climb the stairway miss amp start again Good intro to several basic circuits 3005KT 9 95 ROULETTE LED Ball spins round the wheel slows down amp drops into a slot 10 LED s Good intro to CMOS decade counters amp Op Amps 3006KT 10 95 12V XENON TUBE FLASHER TRANSFORMER steps up a12V supply to flash a25mm Xenon tube Adjustable flash rate 3163KT 13 95 LED FLASHER 1 5 ultra bright red LED s flash in 7 selectable patterns 3037MKT 5 95 LED FLASHER 2 Similar to above but flash in sequence or randomly Ideal for model railways 3052MKT 5 95 INTRODUCTION TO PIC PROGRAMMING Learn programming from scratch Programming hardware a P16F84 chip and a two part practical hands on tutorial series are provided 3081KT 21 95 SERIAL PIC PROGRAMMER for all 8 18 28 40 pin DIP serial programmed PICs Shareware soft ware supplied limited to programming 256 bytes registration costs 14 95 3096KT 12 95 ATMEL 89Cx051 PROGRAMMER Simple to use yet powerful programmer for the Atmel 8901051 89C2051 amp 89C4051 uC s Programmer does NOT require special software other than a terminal emulator program built into Windows Can be used with ANY computer operating sys
213. oes not fall sufficiently for IClc out put pin 8 to go high When vibration is detected again the capacitor rapidly charges to its former value 358 TIME ADJUSTMENT The hold off time can be adjusted using preset VR2 between limits of almost zero and two minutes approximately The short est timing is provided simply for testing purposes The maximum timing could be extended if required by raising the value of capcitor C4 A CMOS version of the 555 timer i c IC2 is configured as a low frequency astable While vibration is detected the low state of IClc output pin 8 applies a similar state to IC2 reset input pin 4 This disables the device and it does nothing When the hold off time expires IClc pin 8 goes high and with IC2 reset input also high a stream of pulses are passed to IC2 output at pin 3 and hence to buzzer WD1 The frequency of oscillation is determined by the value of fixed resistors R14 and R15 in conjunction with capacitor C5 and with the values used this should be some 3kHz In fact it appears to vary with operating conditions and was much slower in the pro totype This may be seen as a benefit because it reduces the current requirement The buzzer connected to C2 output pin 3 therefore bleeps in sympathy CONSTRUCTION Construction of the Washing Ready Indicator is based on a single sided printed circuit board p c b This board is avail able from the EPE PCB Service code 342 The topside
214. of all holes in metal cases prior to drilling them The small indentations guide the drill bit and make accurate drilling much easier An automatic punch works well with aluminium Go carefully when using an ordinary punch with aluminium panels These buckle and distort quite easily as you will soon discover if due care is not taken Centre punches are unsuitable for many plas tic cases which could easily be cracked or more seriously damaged An indentation is still needed to stop the drill bit from wandering and this can be made using a pointed tool such as a bradawl together with a minimum of pressure Drilling Holes It is then a matter of using standard do it yourself tools to drill the holes file cutouts or whatever Due to the softness of the materials used for most cases it is best to drill slowly and very carefully If you use an electric drill that has some sort of speed con trol a low speed is best A hand drill is perfectly adequate for most project construction With an awkward case it might be necessary to enlist the services of a helper to keep it in place while the holes are drilled Normal clamping techniques can be used with most cases but use some cloth to protect the panels from damage Do not rely on any paper or plastic coverings to protect panels from clamps Always have a piece of scrap tim ber MDF etc under the work piece This supports the panel so that there is less risk of it buckling and it
215. oltage The volt age current and pulse duration limits for the digits are not known since Bodet did not respond to the author s request for information The digital control i c s require to be powered at 5V d c which must not be exceeded This is provided from the 12V line via regulator IC9 which can supply up to 100mA of sustained current Be aware though that on the prototype it was O 12V O 5V PULSE IC2 3 PINS 1 9 BANK 1 LENGTH IC2 3 PINS 1 9 BANK 2 IC2 3 PINS 1 9 BANK 3 PC HANDSHAKE SK1 ERROR IC1 PIN 1 SELECT IC1 PIN 2 DIGIT IC1 PIN3 IC5 PIN 6SEGMENT OFF SEGMENT IC4 5 PIN 1 IC4 5 PIN2 gt SELECT IC4 5 PIN 3 IC4 PIN 6 SEGMENT ON R1 TO R8 ANY 28 4 6 6 F 8 2 3 4 5 6 7 GND Fig 7 Circuit diagram showing the PIC 16F84 control connections plus power supply 327 COMPONENTS Resistors RItoR9 k Qoff See 5 All 0 25W 5 carbon film TALK page Potentiometer VR1 100k min preset round Capacitors C1 C2 C5 to C7 100n ceramic 0 2in pitch 5 off 10p ceramic 0 2in pitch 2 off C3 C4 Semiconductors IC1 IC4 IC5 74HC237 1 to 8 multiplexer see text 3 off L293DN 16 pin Half H driver see text 2 off ULN2004A 7 way Darlington line driver see text 2 off PIC16F84 microcontroller preprogrammed see text 78L05 5V 100mA or 7805 5V 1A regulator see text IC2 IC3 IC6 IC7 IC8 Miscellaneous X1 4MHz
216. om ponents resistors etc power supplies relays semiconductors and right on to Zircon drill sets For more information contact WCN Supplies Dept EPE The Old Grain Store Rear of 62 Rumbridge Street Totton Southampton S040 9DS Tel Fax 023 8066 0700 Email info wcnsupplies fsnet co uk EPSON RADIO FAIR SUNDAY 16 June 2002 is the date for Epsom Radio and Electronics Fair at Epson Downs Racecourse Grandstand 10am to 5pm The organisers Radio Fairs tell us that it had been perceived that there was a need for a major radio rally to be staged south of the Thames in the North Surrey area ostensibly to replace the Sandown Rally which is no longer held due to commercial restrictions The Epsom fair is a one day event and will consist of private and trade stalls with added attractions throughout the day Epsom Downs is considered to be an excel lent venue as it is easy to get to from any direction A car boot sale and a bring and buy sale will be incorporated into the rally Ken Macintosh and his band will provide enter tainment during the day As an added attraction to the event morse testing facili ties will be available It is hoped that Dr Bob Whelan president of the RSGB will open this new style event Refreshments and light meals are available Car parking is free Free admission tickets will be made available to schools and colleges in the south east to encourage new people to come into the hobby Nor
217. omparator has two output states so these can be used to set the two thresholds as required by using positive feedback hence the name regenerative A regenerative comparator can be made using an op amp as shown in Fig 7 5 The switching point V omp depends on Vppr and Vout Vepp will usually be fixed but Vout depends on the current state of the comparator One of two values can be taken by Vout that is V o basically the op amp positive and negative saturation voltages which for simplicity we will assume to have the same magnitude To follow the operation of the circuit start by assuming that V is less than v SO Vout Vo AS Vi 1S slowly increased this condition remains until V Veonp Vry upper threshold where ky Veet k R R yV O Poa H R R On switching at V omp Vry the output changes to Vout Va Changing the threshold to a new value V VIL lower threshold where Ry R R comp R Viep V VIL re o R R Vout Will now stay at V o until the input falls below the new V omp value The dif ference in the switching points 1 e the hys teresis Vy 1S Va Vry Vez o R R 370 Fig 7 5 Inverting regenerative com parator circuit An inverting version of the circuit is shown in Fig 7 5 A non inverting version can also be made The equations are slight ly different but the basic operation of the circuit is the same OPTICAL MOT
218. on Items On Line Now o o o ooo cess Seccoe coo Dept ae ce 35 rina Rd Secure ordering Pictures Information e o oo o6 E R ornton Hea iip bsos o ooo o eccc0ee o e WWW d stel n CO 7 u k Fri 9 00 5 30 email admin distel co uk Surplus always wanted for cash 19 RACK CABINETS Europe s Largest Stocks of quality rack cabinets enclosures and accessories Over 1000 Racks from stock This month s special 33 42 47 U High Quality All steel Rack Cabinets ee 2 se 7 Pa Sa Er Bica nr Made by Eurocraft Enclosures Ltd to the highest pos sible spec rack features all steel construction with removable side front and back doors Front and A T back doors are hinged for easy access and all A gt i lockable with five secure 5 lever barrel locks mA The front door is constructed of double walled j m steel with a designer style smoked acrylic front panel to enable status indicators to be seen through the panel yet remain unobtrusive Internally the rack features fully slotted rein forced vertical fixing members to take the heavi est of 19 rack equipment The two movable vertical fixing struts extras available are pre punched for standard cage nuts A mains dis tribution panel internally mounted to the bottom rear provides 8 x IEC 3 pin Euro sockets and 1 x 13 amp 3 pin switched utility socket Overall ventila
219. onverter employing a counter and a digital to ana logue converter DAC To illustrate the theory that we put into practice in Lab Work we can use a reflec tive optosensor and the disc shown in Fig 7 10 to create eight pulses per revolu tion These are counted over a defined interval by an 8 bit binary counter and the count is converted into a voltage using a DAC as indicated in the block diagram in Fig 7 16 We need to control the counter and DAC so that at the end of each timing period e g one second the value on the counter outputs is transferred to the DAC after which the counter is reset ready for the next counting interval as shown in Fig 7 17 A well designed circuit can produce a stable voltage output as a linear function of shaft rotation speed which changes at reg ular intervals However we need to work out several values before the circuit can be finalised These will depend on the intended output e g ms mph or kph the design of the anemometer cups number of cups relative size etc and the relationship between out put voltage and wind speed In the Lab Work design we produce an output voltage of 3 OV for a wind speed of 30ms From comparative measurements using the 3 cup anemometer and a com mercial device the number of pulses per 7 second pps obtained from the circuit is 30 3pps for a wind speed of 6ms which gives 5 O5pps per ms At the maximum wind speed of 30ms 67mph we
220. ood tins etc These materials are in general cheap to obtain and easily worked with simple tools encouraging the trial and error philosophy which leads to innovation and discovery Although primarily a practical book with text closely supported by diagrams some formulae which can be used by straightforward substitution and some simple graphs have also been included 72 pages Order code BP278 4 00 25 SIMPLE INDOOR AND WINDOW AERIALS E M Noll Many people live in flats and apartments or other types of accommodation where outdoor aerials are prohibited or a lack of garden space etc prevents aerials from being erected This does not mean you have to forgo shortwave lis tening for even a 20 foot length of wire stretched out along the skirting board of a room can produce acceptable results However with some additional effort and experimentation one may well be able to improve performance further This concise book tells the story and shows the reader how to construct and use 25 indoor and window aerials that the author has proven to be sure performers Much infor mation is also given on shortwave bands aerial directivity time zones dimensions etc 50 pages Order code BP136 2 25 Everyday Practical Electronics May 2002 CIRCUITS AND DESIGN AN INTRODUCTION TO PIC MICROCONTROLLERS Robert Penfold Designing your own PIC based projects may seem a daunting task but it is really not too difficult providing you have som
221. or runs at 4MHz Le an instruction every lus It has 25 bytes of CIRCUIT DESCRIPTION If you are the sort of person who enjoys the challenge of constructing complex cir cuits you will be disappointed The com plete circuit contains only five compo nents as shown in Fig 2 The clever stuff of course is provided by the PIC The temperature sensor used is a low cost disc thermistor R1 which can be attached via a length of 2 core cable A small preset variable resistor VR1 is used to set the operating point the tem perature threshold at which the alarm sounds Capacitor C1 is used to make the input circuit time dependant as described in the next section For the alarm a piezo sounder WD1 is used because it can make a relatively large amount of noise whilst using a very small amount of elec trical power The whole circuit will conve niently run off a 6V battery HOW IT WORKS Thermistors are basically temperature sensitive resistors normal n t c negative temperature coefficient ones have a high resistance when cold and a low resistance when hot and the change of resistance is a very large effect Everyday Practical Electronics May 2002 An easy way to test a thermistor is to place it in a freezer which is normally at about 18 C and connect it to a multime ter via leads of suitable length After a few minutes the thermistor will reach the tem perature of the freezer and with the meter on i
222. ot allow for component or formula tolerances and are only for illustration Let s think about this a bit more If we assume the astable has a 50 duty cycle then it is high for say 12 5us and low for 12 5us see Fig 5 Each negative going edge triggers the monostable for Ilus after which the monostable wants to time out but the trigger voltage is still there with 1 Sus still to go so the monostable Fig 3 In an H bridge driver opposing pairs of complemen tary transistors drive the load as shown by the path tint taken by the current One phase of full circuit is shown Fig 4 Circuit for testing the re trigger ability of a 555 monostable Keep switch S1 closed for several seconds and observe the I e d D1 LOW TRIGGERS IC2 IC2 CONTINUES WITH HIGH OUTPUT DUE TO IC1 PROVIDING A TRIGGER SIGNAL Fig 5 The monostable IC2 will con tinue to give a High output for as long as its trigger pin is held low by IC 1 IC2 can therefore be used as an inverter carries on timing until the trigger is removed when the monostable output will go low at the same time After a further 12 5us the monostable is triggered once again These timing values may not be quite the same in practice but you get the general idea The overall result is that the monostable simply inverts the astable s square wave It provides base current to both transistors TR2 and TR4 because the bipolar 555 is able to sink up to 200mA current into
223. ots etc The animation is compiled using a full mixed mode SPICE simulator ARES Lite PCB layout software allows professional quality PCBs to be designed and includes advanced features such as 16 layer boards SMT components and an autorouter operating on user generated Net Lists C FOR PICMICRO MICROCONTROLLERS C for PICmicro Microcontrollers is designed for students and professionals who need to learn how to use C to program embedded microcontrollers This product contains a complete course in C that makes use of a virtual C PICmicro which allows students to see code execution step by step Tutorials exercises and practical projects are included to allow students to test their C programming capabilities Also includes a complete Integrated Development Environment a full C compiler Arizona Microchip s MPLAB assembler and software that will program a PIC16F84 via the parallel printer port on your PC Can be used with the P Ctutor hardware see opposite Although the course focuses on the use of the PlCmicro series of microcontrollers this product will provide a relevant background in C programming for any microcontroller PRICES Prices for each of the CD ROMs above are Hobbyist Student c ccsccssceeeessesseeeeeseeesseeeseeeeees 45 inc VAT Institutional Schools HE FE Industry 99 plus VAT Institutional 10 user Network Licence 199 plus VAT Site GCI CC sass a ten
224. owever if the washing machine is situat ed in some place remote from the house the buzzer could be placed somewhere else in the kitchen for example For this to be done you would need to route a length of light duty twin wire between the main unit and buzzer position While operating under standby condi tions the prototype required just 500uA which may be regarded as negligible While actually sounding the current rises to a few milliamps depending on the SCHMITT SLOW PIEZO INVERTER ASTABLE BUZZER Fig 1 Block schematic diagram for the Washing Ready Indicator Being battery operated the circuit is safe to construct and in operation Also because no modifications are made to the appliance itself using the device will not invalidate any manufacturer s warranty The circuit consists of a main unit see photographs which is placed near the washing machine This contains the circuit panel and a 6V battery pack There is an on off switch on the front of the case and a socket on the side which is used to connect a sensor This is placed so as to make mechanical contact with some part of the washing machine The warning device a small piezo buzzer will normally be mounted on the circuit board with a hole drilled in the box to allow the sound to pass through buzzer used The internal 6V battery pack will provide several hundred operating hours and will probably give more than one year of service OVERVIEW
225. pin d i l socket multistrand connecting wire audio screened cable solder pins solder etc Approx Cost 1 0 Guidance Only excluding case amp speaker LINES AMPLIFIER An amplifier circuit diagram incorporating the LM380N audio i c is shown in Fig 7 A general specification guide is shown below The manufacturers National Semiconductor sion for optional heatsinking via some of the pins and this makes the package larger 14 pin The output is short circuit proofed and there is dissipation limiting Gain is fixed Again the purpose of the various components will be evident from earlier descriptions In this version of the LM380N POWER AMPLIFIER R M S power output just before the onset of waveform clipping Speaker Supply Voltage Impedance Ohms 9V 12V 15V 18V 4 400mW 1 12W 1 62W 8 275mW 720mMW 1 32W 2 25W 16 137mW 405mW 720mMW 1 32W 32 68mW 202mW 360mW 765mW Quiescent current 13mA Input resistance 150k ohms Input sensitivity for 720mW output 8 ohm load 12V supply Absolute maximum supply voltage beyond which damage will occur Everyday Practical Electronics May 2002 50mV r m s gain 50 22V SCREENED INPUT LEAD TO SPEAKER LS1 POWER SUPPLY VE POWER SUPPLY VE OV Fig 6 Topside component layout off board wiring details and full size copper foil master for the TBA820M Amplifier series with capacitor C4 controls the shunt ing effect and with the sample tested
226. place controls and sockets to give a neat and usable layout but such a layout might not be very practical It is best to avoid layouts that have long wires running all over the place This is not simply because layouts of this type tend to look rather scrappy With many projects it is best to keep the wiring short in order minimise problems with stray pick up of hum and other signals and to keep stray feedback to a minimum The article 336 Position control knobs etc on the front panel and move them around to find the best layout should point out any restrictions on the layout such as leads that have to be kept very short or components that should be mounted well apart It is advisable to keep inputs and outputs well separated Layouts normally look neater if the spacing between control knobs of the same size is constant On the other hand a purely mathematical approach to front panel layouts will not necessar ily produce the best looking results The neatest layout is the one that looks best in the flesh and not the one that looks best on paper The best way to try out layouts is to place the control knobs onto the front panel together with fixing nuts to rep resent things like toggle switches or sockets This way you get a very accu rate impression of what the finished project will look like When everything looks just right make careful measure ments so that a plan of the layout ca
227. process takes approximately 130ms WATCHDOG Not many published projects seem to use a PIC s Watchdog Timer WDT but when it comes to conserving power using the Sleep mode it is very useful Information can be found in Microchip s data sheets and other publications When a PIC is given the Sleep com mand it shuts down nearly all its functions and as a result consumes a very tiny amount of power it only draws about 4uA from the supply There are three ways in which it can wake up again a by a logic change on a pre defined pin b when the WDT times out and c by an external master Reset It is the second of these options that is used in this project Inside the PIC12C508 the WDT function has its own internal oscillator and counter and these continue to run even if the PIC is asleep When the WDT times out a system Reset is generat ed and the program restarts It should be noted that one bit of the con figuration word of the PIC enables or dis ables the WDT and this bit must be set when the chip is programmed So if we reset the WDT it will then start counting and when it times out 18ms later the program goes through a Reset and starts again That is not a very long time but fortunately we can use the inter nal pre scaler which can be used in con junction with the WDT To do this we use the OPTION register to extend the time out period to approximately 2 3 seconds PIEZO ROUTINE maxf minf SET INI
228. provided 3112KT 18 95 20 MHz FUNCTION GENERATOR Square tri angular and sine waveform up to 20MHz over 3 ranges using coarse and fine frequency adjust ment controls Adjustable output from 0 2V p p A TTL output is also provided for connection to a frequency meter Uses MAX038 IC Plastic case with printed front rear panels amp all components provided 7 12VAC 3101KT 69 95 30 in ONE Electronic Projects Lab Great introduction to electronics Ideal for the budding electron ics expert Build a radio burglar alarm water detector morse i code practice circuit simple computer circuits and much more NO soldering tools or previous electronics knowledge required Circuits can be built and unassembled repeatedly Comprehensive 68 page manual with explanations schematics and assembly diagrams Suitable for age 10 Excellent for schools Requires 2 x AA batteries Order Code EPL030 ONLY 19 95 phone for bulk discounts Everyday Practical Electronics May 2002 Secure Online Ordering Facilities Full Kit Listing Descriptions amp Photos Kit Documentation amp Software Downloads S S PACD HP J o N N 0 A 0 N N 0 0 THE MODERN ELECTRONICS MANUAL CD ROM VERSION ONLY Over 800 pages In depth theory Projects to build Detailed assembly instructions PRICE 9002 Full components checklists N Sis and Extensive data tables ja more Manufacturers web links Easy to use
229. quency via a digital input You are no doubt familiar with the type of circuit in which a single Schmitt trigger inverter is used with a resistor and capaci tor in order to generate a frequency an RC oscillator The technique used in Big Digit is similar The PICI6F84 has a Schmitt trigger input pin RA4 Referring to Fig 7 the Everyday Practical Electronics May 2002 resistance is provided by preset VR1 and the capacitance by C5 Initially software sets RA4 as an output set for logic 0 This discharges C5 RA4 is then set as an input allowing current to charge up C5 via VRI When the Schmitt threshold is reached the software responds to this as an input change from logic 0 to logic 1 It immedi ately sets RA4 as an output at logic 0 again discharging C5 and then resets RA4 as an input once more and so the cycle can continue for as long as the software requires it In this design 16 waveform cycles are used which allows a lower value capacitor to be used than with a single cycle It also increases the capacitor s discharge rate and reduces current flow when RA4 is briefly set low Listing 1 shows the full pulse delay generation routine The frequency of oscillation can be changed by varying VR1 or by using a different value for CS EXPANSION As said earlier additional banks of eight digits can be controlled In this case IC2 and IC3 need to be duplicated on a strip board layout Their pins should be con nect
230. ques payable to Direct Book Service Visa Mastercard Amex Diners Club and Switch orders accepted please give card number card expiry date and Switch Issue No Orders are normally sent within seven days but please allow a maximum of 28 days longer for overseas orders Send your order to Direct Book Service Wimborne Publishing Ltd 408 Wimborne Road East Ferndown Dorset BH22 9ND Tel 01202 873872 Fax 01202 874562 E mail dbs epemag wimborne co uk Online store www epemag wimborne co uk shopdoor htm 378 RADIO VT401 61 minutes A M Radio Theory The most complete video ever produced on a m radio Begins with the basics of a m trans mission and proceeds to the five major stages of a m reception Learn how the signal is detected converted and reproduced Also covers the Motorola C QUAM a m stereo system Order Code VT401 VT402 58 minutes F M Radio Part 1 FM basics including the functional blocks of a receiver Plus r f amplifier mixer oscillator i f amplifier limiter and f m decoder stages of a typical f m receiver Order Code VT402 VT403 58 minutes F M Radio Part 2 A con tinuation of f m technology from Part 1 Begins with the detector stage output pro ceeds to the 19kHz amplifier frequency dou bler stereo demultiplexer and audio amplifier stages Also covers RDS digital data encoding and decoding Order Code VT403 MISCELLANEOUS VT501 58 minutes Fibre Optics From the funda
231. r 22 95 Ref PIR5PACK or 10 for 39 95 Ref PIR10PACK 12V 18Ah SEALED LEAD ACID BATTERIES new and boxed unused pack of 4 69 95 Ref CYC7 or 21 95 each Ref CYC6 12V 6 5Ah SEALED LEAD ACID BATTERIES new and boxed pack of 5 34 95 Ref CYC65A or individually at 8 99 Ref CYC65B 12V 12Ah SEALED LEAD ACID BATTERIES 100mm x 150mm x 95mm 4kg 15 each Ref SSLB 6V 100Ah SEALED LEAD ACID BATTERIES 200mm x 208mm x 238mm 59 SEALED LEAD ACID CHARGER AND FLOAT CHARGER Complete unit will charge 12V lead acids and maintain them with an automatic trickle charge Charger on its own is 15 Ref LAC or charger and a 12V 12Ah battery all fully cased is 25 Ref ACB AERIAL PHOTOGRAPHY KIT This rocket comes with a built in camera It flies up to 500 feet 150m turns over and takes an aer ial photograph of the ground below The rocket then returns with its film via its parachute Takes 110 film Supplied with everything including a launch pad and 3 motors no film 29 98 Ref Astro BUILD YOUR OWN WINDFARM FROM SCRAP New publication gives step by step guide to building wind generators and propel lors Armed with this publication and a good local scrapyard could make you self sufficient in electricity 12 Ref LOT81 MAGNETIC CREDIT CARD READERS AND ENCODING INFO 9 95 Cased with flyleads designed to read standard credit cards Complete with control electronics p c b and manual cover ing everything you could want to know about wha
232. ranch of electronics The CD ROM includes a host of virtual laboratories animations diagrams photographs and text as well as a SPICE electronic circuit simulator with over 50 pre designed circuits Sections on the CD ROM include Fundamentals Analogue Signals 5 sections Transistors 4 sections Waveshaping Circuits 6 sections Op Amps 17 sections covering everything from Symbols and Signal Connections to Differentiators Amplifiers Single Stage Amplifiers 8 sections Multi stage Amplifiers 3 sections Filters Passive Filters 10 sections Phase Shifting Networks 4 sections Active Filters 6 sections Oscillators 6 sections from Positive Feedback to Crystal Oscillators Systems 12 sections from Audio Pre Amplifiers to 8 Bit ADC plus a gallery showing representative p c b photos DIGITAL ELECTRONICS V2 0 Digital Electronics builds on the knowledge of logic gates covered in Electronic Circuits amp Components opposite and takes users through the subject of digital electronics up to the operation and architecture of microprocessors The virtual laboratories allow users to operate many circuits on screen Covers binary and hexadecimal numbering systems ASCII basic logic gates monostable action and circuits and bistables including JK and D type flip flops Multiple gate circuits equivalent logic functions and specialised logic functions Introduces sequential logic including clocks and clock circui
233. re then write your own and re program the same chip Circuit accepts inputs from switches etc and drives motor in response Also runs standard demo sequence from memory All prices include VAT Add 3 00 p amp p Next day 6 99 E mail sales magenta2000 co uk 313 TEN MAGAZINE FOR ELECTRONICS TECHNOLOGY amp COMPUTER PROJECTS Editorial Offices EVERYDAY PRACTICAL ELECTRONICS EDITORIAL WIMBORNE PUBLISHING LTD 408 WIMBORNE ROAD EAST FERNDOWN DORSET BH22 9ND Phone 01202 873872 Fax 01202 874562 Email epe wimborne co uk Web Site http www epemag wimborne co uk EPE Online www epemag com EPE Online Shop www epemag wimborne co uk shopdoor htm See notes on Readers Enquiries below we regret lengthy technical enquiries cannot be answered over the telephone Advertisement Offices EVERYDAY PRACTICAL ELECTRONICS ADVERTISEMENTS MILL LODGE MILL LANE VOL 31 No 5 MAY 2002 THORPE LE SOKEN ESSEX C016 OED Phone Fax 01255 861161 Email epeads aol com MAGIC POWERS The start of this month s new series on Simple Audio Circuits raises a question that always annoys me I guess it is a pet hate of mine To put it in simple terms I hate to see audio output powers quoted by manufacturers that are frankly fairy tales If you see a set of small computer speakers with internal amplifiers quoted as having 100W or greater output then I suggest you simply buy from a more honest manufacturer How do man
234. removed However the addition of the forward bias of D1 about 0 3V means that the final discharge voltage of the battery is raised to 0 9V to 1 0V Additional resistors R3 and R5 ensure that sufficient current flows through D1 It should be noted that the battery is discharged sufficiently when the l e d begins to flash When the discharge is complete 1 e to 0 9V the l e d goes out altogether Total discharge may damage Nickel Cadmium or Nickel Metal Hydride cells and is not recommended ARW The flashing of l e d D3 when the battery is nearing the recom mended discharge level is caused by the increasing internal resistance of the battery lowering the terminal voltage to below the threshold level Then when no current flows the internal resistance is of no con sequence since the terminal voltage rises to the threshold voltage by taking some energy from the battery Liao Jian Mei Singapore Emergency Light A Wimd up TE circuit diagram shown in Fig 2 offers a stepper motor powered Emergency Light When spun rapidly between the fingers a small four phase stepper motor will produce an a c voltage of around 5V at 25mA per phase If all four windings are paralleled up to 100mA can therefore be produced If this is stepped up with a small 230V to 6V OV 6V centre tapped mains transformer a small stepper motor is capable of powering a 6 inch 4W fluorescent tube The transformer must be a small one around 250mA or s
235. rogram the screen shown in Fig 14a will be displayed The three possible printer port registers address es are displayed at the top It is necessary to select the one appro priate to your PC s configuration Most likely it will be address 378 hex but could be hex 278 or 3BC Select the address by pressing 0 1 or 2 pressing any other key including lt ENTER gt always selects 0 i e address 378 If you do not know which address your PC uses try all three The system will show you have the correct one when it proves that it can send data to the displays The PIC board must be free of assembly errors of course Having selected the register the screen changes to that in Fig 14b Underneath the main title you are asked to enter the num ber of digits that you wish to be controlled with a range of to 24 Values outside this range are not accepted At the bottom of the screen are dis played the characters which can be sent for display via the 7 segment digits With the exception of the control keys mentioned next this represents the full range of keys that are functional Any others will be ignored by the program although you can add to the range as discussed later To either side of the screen are quoted the commands available when the program is in full control mode The lt ESC gt escape key causes the program to restart from its beginning and may be used at any time Pressing the lt CTRL gt and lt BRK g
236. rovolts depending on type and quality Carbon composition resistors produce the highest flicker noise and wirewound resistors the lowest As flicker noise is more prominent at lower frequencies unlike white noise its effect is not reduced by longer sampling times Burst noise also known as popcorn noise occurs in transistors and results in pulses often in the audio frequency range V signal Fig 7 1 Comparator input output characteristics a schematic b ideal response c realistic response which can lead to a popping sound hence the name popcorn noise Avalanche noise is produced by Zener diodes or other diode junctions undergo ing Zener or avalanche reverse breakdown Avalanche noise is much larger than shot noise and so Zener diodes can introduce a lot of noise into a circuit For this reason they should be avoided in low noise circuits even though they are a temptingly easy way to produce a stable voltage reference COMPARATORS Earlier in the series we discussed how an op amp that is used without negative feed back has very high gain Thus for all but a small range of input voltage differences the output will be saturated see Fig 7 1 These two voltages e g V at and V ap may represent logic O and 1 and will indi cate which of the two inputs is at the high er voltage An op amp used in this way is known as a comparator One input of the comparator is usually connected to a fixed reference
237. rsions state 5 5 or 6 mHz sound specification For cable hyperband signal reception Telebox MB should be con nected to a cable type service Shipping on all Telebox s code B State of the art PAL UK spec UHF TV tuner module with composite 1V pp video amp NICAM hi fi stereo sound outputs Micro electronics all on one small PCB only 73 x 160 x 52 mm enable full tuning control via a simple 3 wire link to an IBM pc type computer Supplied complete with simple working program and documentation Requires 12V amp 5V DC to operate BRAND NEW Order as MY00 Only 39 95 code B See www distel co uk data_my00 htm for picture full details HARD DISK DRIVES 21 2 14 2 TOSHIBA MK1002MAV 1 1Gb laptop 12 5 mm H New 59 95 2 2 TOSHIBA MK4313MAT 4 3Gb laptop 8 2 mm H New 105 00 2 TOSHIBAMK6409MAV 6 1Gb laptop 12 7 mm H New 98 00 2 TOSHIBA MK1614GAV 18 Gb laptop 12 mm H New 149 95 2 to 3 conversion kit for Pc s complete with connectors 15 95 3 COMPAQ 313706 B21 IBM 9 gb ULT SCSI3 New 199 00 3 FUJI FK 309 26 20mb MEM I F RFE 59 95 3 CONNER CP3024 20 mb IDE I F or equiv RFE 59 95 3 CONNER CP3044 40 mb IDE I F or equiv RFE 69 00 3 2 QUANTUM 40S Prodri ve 42mb SCSI I F New RFE 49 00 5 MINISCRIBE 3425 20mb MFM I F or equiv RFE 49 95 5 SEAGATE ST 238R 30 mb RLL I F Refurb 69 95 5 CDC 94205 51 40mb HH MFM I F RFE tested 69 95 5 HP 97548 850 Mb SCSI RFE tested
238. rt Scale for Wind Speed ae fao a two reflective optosensor which consists of an Beaufort Scale Description mph we infra red IR l e d and a phototransistor is 0 eal 1 One pulse per revo shown in Fig 7 15a The components are 1 light air 1 3 lution means that mounted in a plastic that is transparent to 2 slight breeze 4 7 low speeds are diffi IR so as to reduce interference from ambi 3 gentle breeze 8 12 cult to measure as ent light e g a c powered room lighting 4 moderate breeze 13 18 the voltage on the This does not mean that they are totally 5 fresh breeze 19 24 capacitor in the fre immune to ambient light since there is quite 6 strong breeze 25 31 quency to voltage a lot of IR around especially in tungsten 7 near gale 32 38 converter will decay 8 gale 39 46 and the output will 9 strong gale 47 54 not be a linear func 10 storm 55 63 tion of rotation rate 11 violent storm 64 72 12 hurricane 73 82 The frequency to E voltage converter Table 7 4 Conversion between Wind Speed Units does not follow Unit 1 Unit 2 From To To From oe 1a emages in rotation rate mph kph 1 609 0 621 mph ms 0 447 2 237 We can overcome mph knots 0 869 1 151 these problems by ms knots 1 944 0 514 increasing the number Typical examples of slotted and reflec ae g a ee ree of pulses per revolution tive photosensors n os O _ Sd sin a dilereni 372 Everyday Practical Electronics May 2002 SENSOR AMPLIFIER type of frequency to voltage c
239. s Etched faceplate text switching and LOW RADIATION MPR specification Fully guaranteed in EXCELLENT little used condition Tilt amp Swivel Base 4 75 VGA cable for IBM PC included Order as meud Only 129 E caz3 External cables for other types of computers available CALL Generic LOW COST SVGA Monitors We choose the make which includes Compaq Mitsubishi IBM etc Supplied ready to run with all cables Standard RTB 90 day guarantee 15 17 69 00 79 00 Supplied in good used condition Shipping code D PHILIPS HCS35 same style as CM8833 attractively styled 14 colour monitor with both RGB and standard composite 15 625 Khz video inputs via SCART socket and separate phono jacks Integral audio power amp and speaker for all audio visual uses Will connect direct to Amiga and Atari BBC computers Ideal for all video monitoring security applications with direct connection to most colour cameras High quality with many features such as front concealed flap controls VCR correction button etc Good used condition fully tested guaranteed Dimensions W14 x H1234 x 15 D Only 99 00 E PHILIPS HCS31 Ultra compact 9 colour video monitor with stan dard composite 15 625 Khz video input via SCART socket Ideal for all monitoring security applications High quality ex equipment fully tested amp guaranteed possible minor screen burns In attrac tive square black plastic case measuring W10 x H10 x 13 D 240 V
240. s most electronics enthusi asts encounter the need to amplify and reproduce audio signals The final stages of radio receivers intercom units security and surveillance installations or just a hankering for a big sound from a Walkman or portable CD player all involve audio amplification and a speaker system And the amplification usually goes hand in hand with some form of signal processing Music reproduction calls for a wide frequency response and tone control cir cuitry Speech communication especially LM386N 1 340 TDA7052 under difficult conditions is greatly clarified if the frequency response is curtailed This short series of articles describes simple but effective ways of meeting these different requirements Although the circuits are capable of a good standard of reproduction they will particularly interest the constructor who looks for plenty of performance per pound or dollar We begin with the power amplifier Six alternatives are given and with the require ment of maximum performance for mini mum cost and effort they are all based on widely available integrated circuits 1 c s TBA820M LM380N HOW MUCH POWER Before considering the various circuits it is worthwhile to reflect on the amount of power actually needed Clear reproduction in Walkman type earphones of reasonable sensitivity can be achieved with a miserly milliwatt 0O 001W When listening to talk pro grammes in
241. s together with wiring diagrams where appropriate plus notes on construction and use The following designs are included AF Generator Capacitance Meter Test Bench Amplifier AF Frequency Meter Audio Mullivoltmeter Analogue Probe High Resistance Voltmeter CMOS Probe Transistor Tester TTL Probe The designs are suitable for both newcomers and more experienced hobbyists Order code BP248 4 49 AUDIO AND 104 pages MUSIC VALVE amp TRANSISTOR AUDIO AMPLIFIERS John Linsley Hood This is John Linsley Hood s greatest work yet describ ing the milestones that have marked the development of audio amplifiers since the earliest days to the latest sys tems Including classic amps with valves at their heart and exciting new designs using the latest components this book is the complete world guide to audio amp design Contents Active components Valves or vacuum tubes Solid state devices Passive components Inductors and transformers Capacitors Resistors Switches and electrical contacts Voltage amplifier stages using valves Valve audio amplifier layouts Negative feedback Valve operated power amplifiers Solid state voltage amplifiers Early solid state audio amplifiers Contemporary power amplifier designs Preamplifiers Power supplies PSUs Index Order code NE24 21 99 AUDIO AMPLIFIER PROJECTS R A Penfold A wide range of useful audio amplifier projects each project features a circuit diagram an e
242. s published in these issues VOL 2 CONTENTS BACK ISSUES July 1999 to December 1999 all the projects features news lUs etc from all six issues Note No advertisements are included PIC PROJECT CODES All the available codes for the PIC based projects published in these issues VOL 3 CONTENTS BACK ISSUES January 2000 to June 2000 all the projects features news lUs etc from all six issues PIC PROJECT CODES All the available codes for the PIC based projects published in these issues VOL 4 CONTENTS BACK ISSUES July 2000 to Dec 2000 all the projects features news lUs etc from all six issues PROJECT CODES All the available codes for the programmable projects in these issues VOL 5 CONTENTS BACK ISSUES January 2001 to June 2001 all the projects features news lUs etc from all six issues PROJECT CODES All the available codes for the programmable projects in these issues including those for Interface EXTRA ARTICLES ON ALL VOLUMES BASIC SOLDERING GUIDE Alan Winstanley s internationally acclaimed fully illustrated guide UNDERSTANDING PASSIVE COMPONENTS Introduction to the basic principles of passive components HOW TO USE INTELLIGENT L C Ds By Julyan llett An utterly practi cal guide to interfacing and programming intelligent liquid crystal display modules PhyzzyB COMPUTERS BONUS ARTICLE 1 Signed and Unsigned Binary Numbers By Clive Max Maxfield and Alvi
243. s that will completely disrupt TV picture and sound Works on FM too Discretion advised 8 set Ref F TJ5 BODYHEAT TELESCOPE PLANS Highly directional long range device uses recent technology to detect the presence of living bodies warm and hot spots heat leaks etc Intended for security law enforcement research and development etc Excellent security device or very interesting science project 8 set Ref F BHT1 BURNING CUTTING CO2 LASER PLANS Projects an invisible beam of heat capable of burning and melting materials over a con siderable distance This laser is one of the most efficient convert ing 10 input power into useful output Not only is this device a workhorse in welding cutting and heat processing materials but it is also a likely candidate as an effective directed energy beam weapon against missiles aircraft ground to ground etc Burning and etching wood cutting plastics textiles etc 12 set Ref F LC7 www bullnet co uk ISSN 0262 3617 PROJECTS THEORY NEWS COMMENTS POPULAR FEATURES VOL 31 No 5 MAY 2002 Cover illustration by Jonathan Robertson ELECTRONICS TODAY INTERNATIONAL www epemag wimborne co uk EPE Online www epemag com Wimborne Publishing Ltd 2002 Copyright in all drawings photographs and articles published in EVERYDAY PRACTICAL ELECTRONICS is fully protected and reproduction or imitations in whole or in part are expressly forbidden e SSS SSS
244. should therefore be taken to ensure that the off load voltage is always less than the maximum safe working volt age of the amplifier Never connect a working power supply to an amplifier without first checking its output voltage ELECTRICAL CHARACTERISTICS The electrical characteristics of the various devices are tabulated alongside the circuit diagrams except one for easy reference Power output figures are based on measurements taken on a single randomly purchased sample For reasons already given they are somewhat lower than the figures quoted by the manufacturers Recommendations are made regarding the speaker impedances to use with various sup ply voltages in order to keep the dissipation of the devices within reasonable limits The input resistance maximum voltage ratings and frequency response details are those supplied by the manufacturers 341 AMPLIFIER PROJECTS In use there is little to distinguish between the four low powered amplifiers all perform well There are however dif ferences which make one device more suit able than another for a particular application Low current consumption is important when equipment is powered from dry bat teries Quiescent current drawn by the small amplifiers is in the region of 6mA 13mA for the LM380 In the case of the LM386N TBA820M and LM380 current rises to around 120mA when 500mW is being delivered into an 8 ohm load Current consumed by the TDA70
245. software in its turn holds its printer port output DA7 low and waits for the RA3 high signal to arrive via its printer port Error line Having received this signal however it takes no immediate action but waits for a keyboard key to be pressed Having received a keypress the PC relates it to a lengthy look up table that holds segment data in respect of keypress es If segment data has been allocated to that key it is output as seven bits same relationship as with keypad data plus bit 7 set high It then remains in another holding loop until the Error line goes low The PIC recognising that its RB7 pin has gone high accepts the incoming 7 bits of RBO RB6 data as valid It immediately acknowledges this to the PC by setting line RA3 low The PC having accepted this acknowl edgement is now free to wait for another keypress but will not send it until the PIC signals that it is ready Between accepting bytes of data the PIC sends the segment data serially to the selected digit in a similar fashion to that described earlier On completion of each digit s output the PIC again sets hand shake line RA3 high asking for more PC data DIGIT COUNT SELECTION The PC program has been written so that it can be set to the exact number of digits in use unlike the keypad software which always expects 24 digits It also provides the facility to select which printer port register address is used On running the p
246. st of projects Be especially careful with cases having fixing screws that penetrate several millimetres into the open area inside the case Many metal instrument cases fall into this category It is easy to produce a plausible look ing layout that actually results in a fixing screw going straight into the battery or a circuit board when the lid of the case is fitted in place Where a case is supplied with fixing screws that are clearly longer than necessary it is probably worthwhile replacing them with shorter ones It is not a good idea to make every project as small as possible If a project really needs to be of diminutive propor tions then try to work out a layout that will give a really compact finished arti cle It is otherwise better to err on the side of caution and choose a case that seems to be slightly too large This avoids making construction unneces sarily awkward and will probably result in a finished unit that looks neater and is easier to use It is certainly a good idea to place the circuit board battery and any other large components inside the case before you start the cutting and drilling Alternatively make some careful mea surements and some drawings This should enable you to establish that everything fits and that the controls circuit board etc are not vying for the same space Long and Short of it When designing layouts you are often faced with conflicting require ments You would like to
247. st them with real hardware Follow on with a little theory Our complete PIC training and development system consists of our universal mid range PIC programmer a 306 page book covering the PIC16F84 a 212 page book introducing the PIC16F877 family and a suite of programmes to run on a PC The module is an advanced design using a 28 pin PIC16F872 to handle the timing programming and voltage switching requirements The module has two ZIF sockets and an 8 pin socket which between them allow most mid range 8 18 28 and 40 pin PICs to be programmed The plugboard is wired with a 5 volt supply The software is an integrated system comprising a text editor assembler disassembler simulator and programming software The programming is performed at normal 5 volts and then verified with plus and minus 10 applied to ensure that the device is programmed with a good margin and not poised on the edge of failure Requires two PP3 batteries which are not supplied Universal mid range PIC programmer module Book Experimenting with PIC Microcontrollers Book Experimenting with the PIC16F877 2nd edition Universal mid range PIC software suite etek PIC16F84 and PIC16F872 test PICs 157 41 UK Postage and insurance 7 50 Europe postage amp Insurance 13 00 Rest of world 22 00 Experimenting with PIC Microcontrollers This book introduces the PIC16F84 and PIC16C711 and is the easy way to get started for anyone
248. sub miniature omni directional electret microphone insert used in the model was obtained from Maplin 01283 565435 or www maplin co uk code FS43W You could possibly use their ultra miniature version code QY62S This has not been tried in the unit The same company also supplied the 3V to 24V d c 10mA max piezoelectric buzzer code KU56L Most of our components advertisers should be in a position to offer an identical buzzer The small printed circuit board is available from the EPE PCB Service code 342 see page 379 Teach In 2002 Lab 7 Like most of the Lab Works in the Teach In 2002 series it s the sen sor elements that are usually specials and cause most purchasing problems However this is not the case with the first simple comparator demonstration circuits Lab 7 1 where the light dependent resistor I d r type ORP12 is needed This is widely stocked and advertisers such as ESR Bardwell Bowood Cricklewood and Sherwood Electronics should be able to supply For the Anemometer Wind Speed Force Lab 7 2 and the Wind Direction Indicator Lab 7 3 the miniature reflective opto switch type SG2BC was ordered from Farnell 0113 263 6311 or www farnell com code 491 366 They also supplied the TLC 7524 8 bit DAC chip code 397 246 It may be well worth investigating the possibility of using the wind cup hardware stocked by Magenta Electronics 01283 565435 or www magenta2000 co uk Freezer Alarm
249. switch sensor Entry exit delays auto reset and adjustable alarm duration 6 12V DC PCB 47mm x 55mm 1019KT 11 95 Box 2019BX 8 00 PIEZO SCREAMER 110dB of ear piercing noise Fits in box with 2 x 35mm piezo elements built into their own resonant cavity Use as an alarm siren or just for fun 6 9VDC 3015KT 10 95 COMBINATION LOCK Versatile electronic lock comprising main circuit amp separate keypad for remote opening of lock Relay supplied 3029KT 10 95 ULTRASONIC MOVEMENT DETECTOR Crystal locked detector frequency for stability amp reliability PCB 75x40mm houses all components 4 7m range Adjustable sensitivity Output will drive external relay circuits 9VDC 3049KT 13 95 PIR DETECTOR MODULE 3 lead assembled unit just 25x35mm as used in commercial burglar alarm systems 3076KT 8 95 INFRARED SECURITY BEAM When the invisible IR beam is broken a relay is tripped that can be used to sound a bell or alarm 25 metre range Mains rated relays provided 12VDC operation 3130KT 12 95 SQUARE WAVE OSCILLATOR Generates square waves at 6 preset frequencies in factors of 10 from 1Hz 100KHz Visual output indicator 5 18VDC Box provided 3111KT 8 95 PC DRIVEN POCKET SAMPLER DATA LOG GER Analogue voltage sampler records voltages up to 2V or 20V over periods from milli seconds to months Can also be used as a simple digital scope to examine audio amp other signals up to about 5KHz Software amp D shell case
250. t 5 10 Ref A1015 pack of 5 CO2 cartridges 3 50 Ref GAS5 33 KILO LIFT MAGNET Neodynium 32mm diameter with a fixing bolt on the back for easy mounting Each magnet will lift 33 kilos 4 magnets bolted to a plate will lift an incredible 132 kilos 15 Ref MAG33 Pack of 4 just 39 Ref MAG33AA BSA METEOR AIR RIFLE UK made 22 rifle top quality profes sional air rifle 84 15 Ref BSAMET 500 Lazapell pellets 5 Ref LAZAPELL MAMOD 1313 TE1A TRACTION ENGINE Attractive working model of traditional steam engine 85 Ref 1313 MAMOD STEAM ROADSTER white magnificent working steam model car 112 Ref 1319 MAMOD STEAM WAGON Working model steam wagon finished in blue 112 Ref 1318 Brown version with barrels 122 Ref 1450 POCKET SPY MONOCULAR Clever folding monocular with 8 x 21 magnification made by Helios with case 14 99 Ref MONOC KEVLAR BRITISH ARMY HATS Broken or missing straps hence just 8 each Ref KEV99 CCTV SYSTEMS 24 99 Complete with camera 20 metres of cable p s u and info simple connection to scart 24 99 Ref CCTVCAN2 FM BROADCAST BAND HIGH POWER TRANSMITTERS can be viewed and bought online at www veronica kits co uk TONER CARTRIDGES FOR COPIERS AND PRINTERS can be bought online at www nationaltoners co uk VELOSOLEx Traditional French style two stroke moped engine over front wheels black only 695 Ref VELO Delivered direct in a box you need to fit the pedals etc th
251. t keys simultaneously causes the program to end This is the only way in which it can be halted and exited Otherwise all keyboard characters shown in the bottom line are available for output to the digits Acceptable keypresses are responded to immediately and data is output to the digits in sequence the PIC s digit count being incremented following receipt of each character When the final digit in the sequence has been triggered the count automatically recommences from Digit 1 When entering data for output to the dig its pressing lt ENTER gt causes the PIC to reset the digit count back to Digit 1 Pressing the space bar causes the next digit to be cleared no segments showing PC FIRST PIC SECOND In the mid screen area you are told that you should switch on the PIC unit now As said earlier when the PIC program is first switched on the PIC examines Port B to see whether its pins are high or low If high keypad control is assumed On run ning the PC program however its first activity is to set its printer port lines low On reading Port B being low the PIC knows that PC control is required Fig 14 Sections of Big Digit PC program setup screens a printer port selection b digit quantity selections 331 Fig 15 Example of PC screen during digit control Consequently do not switch on the PIC unit until you see the screen now being dis cussed When you have switched on the PIC then ent
252. t s hidden in that magnetic strip on your card Just 9 95 Ref BAR31 77 KILO LIFT MAGNET These Samarium magnets measure 57mm x 20mm and have a threaded hole 5 16th UNF in the cen tre and a magnetic strength of 2 2 gauss We have tested these on a steel beam running through the offices and found that they will take more than 170lb 77kg in weight before being pulled off Supplied with keeper 19 95 ea Ref MAG77 HYDROGEN FUEL CELL PLANS Loads of information on hydro gen storage and production Practical plans to build hydrogen fuel cell good workshop facilities required 8 set Ref FCP1 STIRLING ENGINE PLANS Interesting information pack covering all aspects of Stirling engines pictures of home made engines made from an aerosol can running on a candle 12 STIR2 12V OPERATED SMOKE BOMBS Type 3 is a 12V trigger and 3 smoke cannisters each cannister will fill a room in a very short space of time 14 99 Ref SB3 Type 2 is 20 smaller cannisters suitable for mock equipment fires etc and 1 trigger module for 29 Ref SB2 Type 1 is a 12V trigger and 20 large cannisters 49 Ref SB1 BRAND NEW NATO ISSUE RADIATION DETECTORS SALE PRICE JUST 69 95 Current NATO issue standard emergency services unit Used by most of the world s military personnel New and boxed Normal retail price 400 Bull s bargain price just 69 95 Ref PDRM BASIC GUIDE TO BIO DIESEL How to make diesel fuel from used kitchen oil 6 Ref BIOF
253. t they can analyse and modify cir cuits and build or restore an amplifier Design principles and construction techniques are provided so readers can devise and build from scratch designs that actually work The second edition of this popular book builds on its main strength exploring and illustrating theory with practical applications Numerous new sections include output trans former problems heater regulators phase splitter analysis and component technology In addition to the numerous amplifier and preamplifier circuits three major new designs are included a low noise single ended LP stage and a pair of high voltage amplifiers for driving electrostatic transduc ers directly one for headphones one for loudspeakers 488 pages Order code NE33 26 99 VALVE RADIO AND AUDIO REPAIR HANDBOOK Chas Miller This book is not only an essential read for every profes sional working with antique radio and gramophone equipment but also dealers collectors and valve tech nology enthusiasts the world over The emphasis is firm ly on the practicalities of repairing and restoring so technical content is kept to a minimum and always explained in a way that can be followed by readers with no background in electronics Those who have a good grounding in electronics but wish to learn more about the practical aspects will benefit from the emphasis given to hands on repair work covering mechanical as well as electrical aspects of servici
254. t when the speaker imped ance is increased to 16 ohms with a 9V supply Although usually costing a little more than the other low power chips this is the device of choice when the supply voltage SIGNAL INPUT SUPPLY VOLTAGE V INPUT GROUND 10 50 excluding case amp speaker 7 052 AMPLIFIER has to be low a good output is required and high gain is not important Current consumption for a given output power is however almost twice that of the LM386N and the TBA820M CIRCUIT BOARD The printed circuit board component layout wiring details and full size copper foil master pattern are shown in Fig 4 This board is available from the EPE PCB Service code 344 TDA7052 O rel MO arily 8 SIGNAL OUT NOT CONNECTED 6 OUTPUT GROUND beyond which damage will occur 18V NOTCONNECTE SIGNA our Suggested maximum supply voltage with a 4 ohm speaker 6V Tp Wenge T with 8 or 16 ohm speakers 9V Frequency response at the 3dB points 25Hz 20kHz Everyday Practical Electronics May 2002 Fig 3 Circuit diagram and pinout details for the TDA7052 Amp See left for performance guide 343 COMPONENTS TDA7052 AMPLIFIER Capacitors See C1 10g radial SKRIO elect 25V C2 100ndisc TALK ceramic C3 220u radial PA8 elect 25V Only four components are mounted on the TDA7052 p c b Potentiometers VR1 4k7 min rotary carbon log Fig
255. te the segments It can sink 500mA per stage and is capable of handling voltages up to 50V This device also has the benefit of hav ing built in diodes across each output which inhibit back e m f generation when switching inductive loads such as the segment coils see Fig 3 ULN2004A Fig 3 Schematic of one stage within a ULN 2004A 7 stage line driver 326 It is a bipolar fabricated Darlington device that requires a positive voltage at each input to turn on the respective open collector output Conveniently each input has its own 10 5kQ series resistor remov ing the need for external resistors such as required in the control line feeding into the base of a normal discrete transistor The inputs are also diode protected Using a 74HC237 multiplexer the seven segments can readily be controlled direct ly through the ULN2004A driver COMMON ANODE That took care of current sinking through the segments The problem then became that of providing multiplexed power to each digit If you relate the con cept to a common anode 7 segment l e d matrix the individual segment cathodes had now been catered for it was the com mon anode current control that was now required In other words a current source was needed at a minimum of 280mA It had been expected that as multiple high current sinking paths were available in one i c as with the ULN2004A so mul tiple high current sourcing devices would be equ
256. ted to the power supply voltage and the emitter to ground via resistor R2 as shown The value of R2 can be calculated from SURFACE datasheets the relevant data for the reflec P A tive device we will be using this month is on the separate cups concept the cups given in Table 7 2 are replaced by an S shaped arrange PLASTIC In Lab Work we illustrate the use of wane Cup A ews from E a See eee optosensors and describe a rotation sensor Slap ee AOW Deke VOLO ICHON that uses one in a circuit for measuring i e they will not start until a particular wind speed Before that though let s dis minimum wind speed Fig 7 14 Reflective photosensor Cup anemometers These are probably the most familiar and operate by the wind blowing three or sometimes four cups around on a spindle In a variation cuss a few basics about wind sensing Hot wire anemometers If a wire is heat CATHODE ANODE EMITTER COLLECTOR WIND SPEED ed to a given temperature and air is MEASUREMENT allowed to flow across the wire some of aa the heat will be removed Hot wire The speed of the wind is measured in anemometers use this principle and can be distance per unit time such as miles per extremely sensitive They are however hour mph kilometres per hour kph quite fragile since the wire is very thin metres per second ms or knots Another subjective measurement uses the Beaufort Acoustic anemometers The speed of Scale a numbering system that goes
257. tes Part Four Power Supplies Guides you step by step through different sections of a power supply Order Code VT204 VT205 57 minutes Part Five Amplifiers Shows you how amplifiers work as you have never seen them before Class A class B class C op amps etc Order Code VT205 VT206 54 minutes Part Six Oscillators Oscillators are found in both linear and digi tal circuits Gives a good basic background in oscillator circuits Order Code VT206 34 95 2 inc VAT amp postage Order 8 or more get one extra FREE Order 16 get two extra FREE VCR MAINTENANCE VT102 84 minutes Introduction to VCR Repair Warning not for the beginner Through the use of block diagrams this video will take you through the various circuits found in the NTSC VHS system You will follow the signal from the input to the audio video heads then from the heads back to the output Order Code VT102 VT103 35 minutes A step by step easy to follow procedure for professionally clean ing the tape path and replacing many of the belts in most VHS VCR s The viewer will also become familiar with the various parts found in the tape path Order Code VT103 DIGITAL Now for the digital series of six videos This series is designed to provide a good ground ing in digital and computer technology VT301 54 minutes Digital One Gates begins with the basics as you learn about seven of the most common gates which are used in almost every digital circ
258. ther readers if you are looking for advice or help from fellow electronics enthusiasts why not ask them by posting your message into the EPE Chat Zone We are very grateful to the regular readers who support us and help out with queries in the Chat Zone Strip Teaser In the March 02 issue of EPE Net Work I pointed the way to a simple Stripboard Designer graphics program that is available as shareware from www geocities com stripboarddesigner The principle of shareware is very simple you download the demo for free and if you like the product you buy it If you don t like it you haven t lost anything Some of the world s best programs such as JASC Paint Shop Pro started out as modest shareware so by sup porting shareware honestly you encourage software authors to develop their ideas further One of the tasks I still enjoy is the creation of stripboard layouts which I always found to be a stimulating mental exercise followed by all the troubleshooting afterwards For decades I used quadrille squared paper and after some frenetic scribbling and erasing I would finally develop a layout that I could take to the workbench Nowadays computers can help a lot by allowing layouts to be created and edited on screen also the design can be saved and printed for future reference Probably the first commercial program to help with this task was Ambyr s Stripboard Magic which my fellow contributor Andy Flind who creates many of EPE
259. though chips designed specifically for hi fi amplifiers are available they usually require higher voltage and or split rail power supplies This makes them less easy and more expensive to use Q 6V TO 15V Component layout on the TDA2003 p c b TDA2003 POWER AMPLIFIER R M S power output just before the onset of waveform clipping Speaker Supply Voltage Impedance Ohms 9V 12V 15V 2 2 25W 4W 5 75W 4 1 28W 2 6W 3 9W 8 720mW 1 44W 21W SCREEN Quiescent current 45mA TYPE No Input sensitivity for 2 6W output 4 ohm load 12V supply 42mV r m s gain 80 SUPPLY VOLTAGE V METAL TAG oe eae SIGNAL OUT Absolute maximum supply voltage PIN 3 GROUND oe beyond which damage will occur 28V INPUT Absolute maximum operating voltage 18V FRONT VIEW OF TDA2003 Frequency response 40Hz to 15kHz at the 3dB points The upper frequency limit can be extended by reducing the value of C5 Fig 9 Circuit diagram for a single TDA2003 Amp 346 Everyday Practical Electronics May 2002 SCREENED INPUT LEAD VR1 FRONT VIEW HEATSINK POWER SUPPLY VE POWER SUPPLY VE OV TO SPEAKER LS1 2 5IN 63 5mm Fig 8 The LM380N printed circuit board component layout off board interwiring and full size copper foil master pattern Note the heatsinks HEATSINKS For those readers who wish to get the most out of the chip a suitable heatsink for the LM380 Fig 7 and Fig 8 can be formed from two 40mm 1 i
260. tor R8 allows the capacitor to charge to almost supply voltage in a very short time In fact it will not quite reach this value because it is being constantly drained by the network comprising fixed resistor R10 and preset VR2 When the pulses stop the capacitor gradually discharges in a time dependent on the adjustment of VR2 It cannot drain back into IClb pin 7 because diode D2 is reverse biased Note that without R10 and VR2 capaci tor C4 could only discharge by leakage and this would take a very long time This is because the input resistance of op amp IClc whose purpose will be explained presently is extremely high INVERTING EFFECT Op amp section Clc gives a Schmitt trigger inverting effect It works like this The voltage existing across capacitor C4 is applied to the inverting input pin 9 The non inverting input pin 10 is maintained at approximately 2V by the potential divider action of resistors R11 and R12 While pulses are detected the inverting input voltage which is close to supply pos itive voltage will exceed the non inverting one and Clc output pin 8 will be low When the pulses stop and sufficient time has elapsed to discharge C4 below the 2V level the conditions reverse and pin 8 will go high Resistor R13 provides some posi tive feedback and sharpens the switching between the output on and off states When the machine vibration stops for a short time the voltage across capacitor C4 d
261. tronic specifications could be located other than a schematic for one segment see Fig l and Fig 2 An email to Bodet for data produced no response Time for experiments Briefly connecting an ammeter between a segment and a 12V power supply revealed the current required to activate the mechanical flap around 280mA What Surely not An ohms check across the var ious controlling coils showed a typical d c resistance of 430 Wow yes indeed that unscientific test had shown a current figure in the right ball park Furthermore there were seven segments to be controlled about 2A per digit and users would probably need several digits More used to dealing with liquid crystal dis plays needing only a handful of milliamps rather than two thousand milliamps the 323 author recognised that the digits were more than just monsters in size RESEARCHING DESIGN Having numerous data books and CD ROMs is always to be recommended These days so is Internet access Using a mixture of sources a couple of evenings were spent researching the type of semi conductors that were available to handle such currents in a multiplexed situation It was a foregone conclusion that they need ed to be capable of being PIC controlled Any idea of using any form of discrete transistor power FET or otherwise was rejected Such techniques were fine years ago but hardly today s technology when multiplexing even less so regarding any su
262. try counters binary coded decimal and shift registers A D and D A converters traffic light controllers memories and microprocessors architecture bus systems and their arithmetic logic units Sections on Boolean Logic and Venn diagrams displays and chip types have been expanded in Version 2 and new sections include shift registers digital fault finding programmable logic controllers and microcontrollers and microprocessors The Institutional versions now also include several types of assessment for supervisors including worksheets multiple choice tests fault finding exercises and examination FILTERS Filters is a complete course in designing active and passive filters that makes use of highly interactive virtual laboratories and simulations to explain how filters are designed It is split into five chapters Revision which provides underpinning knowledge required for those who need to design filters Filter Basics which is a course in terminology and filter characterization important classes of filter filter order filter impedance and impedance matching and effects of different filter types Advanced Theory which covers the use of filter tables mathematics behind filter design and an explanation of the design of active filters Passive Filter Design which includes an expert system and filter synthesis tool for the design of low pass high pass band pass and band stop Bessel Butterworth and Chebyshev ladder filters Active Filt
263. ts cncessaesnowetebennecesetendeeneelaansused 499 plus VAT UK and EU customers add VAT at 17 5 to plus VAT prices ee ee ee ee ee eee ee ee ee ee Please send me CD ROM ORDER FORM LJ Electronic Projects 1 _ Analogue Electronics Version required C1 Digital Electronics V2 0 Hobbyist Student Filters LI Institutional 1 L Digital Works 3 0 O Institutional 10 user L Electronics CAD Pack _ Institutional 1 L C For PiCmicro Microcontrollers site licence LJ PlCtutor L Electronic Circuits amp Components V2 0 l L PiCtutor Development Kit Standard 1 L PlCtutor Development Kit Deluxe L Deluxe Export l i L Electronic Components Photos O Electronics In Control Single User Note The software on each version is _ Electronics In Control Multiple User the same only the licence for use varies 1 L Modular Circuit Design Single User LI Modular Circuit Design Multiple User F l pame gate sadaa p 2 04642 aida eas be oR ee de Oe ee de EE l POMS ersari es eet oltee epi heads otters bites ares I i KOE kE EOP OSOE EE ee EOE EOE BOE GOE aA EEA GOEREE EEEE EEE REEERE de a ee ee ee ELENE Post code Tel No I PSUS 5 5 4 cages aos dh e card ay hw We oad as oder aa Ha Greed naa ere ee Bae l L enclose cheque PO in sterling payable to WIMBORNE PUBLISHING LTD for Please charge my Visa Mastercard Amex Diners Club Switch
264. ts gold silver ferrous amp non ferrous metals e Efficient quartz controlled microcontroller pulse generation e Full kit with headphones amp all hardware KIT 847 PORTABLE ULTRASONIC PEsT SCARER A powerful 23kHz ultrasound generator in a compact hand held case MOSFET output drives a special sealed transducer with intense pulses via a special tuned transformer Sweeping frequency output is designed to give maximum output without any special setting up KIT 842 sisssisissveaiesssaes 22 56 DEVELOPMENT 68000 TRAINING KIT e NEW PCB DESIGN e 8MHz 68000 16 BIT BUS e MANUAL AND SOFTWARE 2 SERIAL PORTS e PIT AND I O PORT OPTIONS e 12C PORT OPTIONS gt kIT 621 Pm 99 95 e ON BOARD 5V REGULATOR e PSU 6 99 e SERIAL LEAD 3 99 Stepping Motors MD38 Mini 48 step 8 65 MD35 Std 48 step 9 99 MD200 200 step 12 99 MD24 Large 200 step 22 95 MOSFET MkII VARIABLE BENCH POWER SUPPLY 0 25V 2 5A Based on our Mk1 design and preserving all the features but now wit switchin pre regulator for much higher effi ciency Panel meters indicate Volts and Amps Fully variable down to zero Toroidal mains transformer Kit includes punched and printed case and all parts As featured in April 1994 EPE An essential piece of equipment 312 Kit No 845 64 95 PIC PIPE DESCALER e SIMPLE TO BUILD e SWEPT e HIGH POWER OUTPUT FREQUENCY e AUDIO amp VISUAL MONITO
265. ts resistance range you will be able to measure the approximate value of resis tance at this temperature The thermistor used here has a resis tance of around 1k 2 at room temperature see Table 1 Other types of n t c thermis tor could equally well be used with minor alterations to the circuit which are explained later Table 1 Thermistor temperature resistance Temperature Resistance Room 22 C 90022 Fridge 2 C 2k3 Freezer 20 C 11k2 The microcontroller circuit needs to measure this resistance in order to eval uate whether the thermistor is too warm we do not need to know its actual value just whether it is higher or lower than a preset value This can conveniently be done by comparing the resistance of the thermistor to that of a preset resistor VR1 The PIC12C508 is basically a digital device so we need a cunning plan to make it capable of measuring resistance The method is to use the PIC as a timer which can count how long it takes a small capac itor C1 to charge up to a certain voltage If we consider a very simple circuit Fig 3 consisting of just a capacitor C and a resistor R we can see that if the switch is closed the voltage V across the capacitor is zero and it is uncharged As soon as the switch is opened the capacitor charges via the resistor and the voltage rises along an exponential curve Fig 4 In our circuit we time how long it takes to go from zero to the logic threshold of t
266. two answers are compared all we need to do is to subtract one number from another we just want to know which process took the longer Depending upon the outcome we either go directly into the Sleep mode or sound the alarm for a short time before again going to sleep ALARMING Generally speaking a piezo device is not a buzzer it has to be driven by an oscillating signal to make the alarm COMPONENTS Resistor See R1 n t c disc S O D thermistor 10k 1k at temperature Page Potentiometer VR1 10k min enclosed carbon preset horiz Capacitor C1 100n ceramic disc Semiconductor IC1 PIC12C508 preprogrammed microcontroller see text Miscellaneous WD1 piezo sounder 3V to 24V Stripboard 10 strips x 17 holes plastic case size and type to choice battery holder AA size batteries 4 off battery clip 8 pin d i l socket connecting wire solder etc Approx Cost o Guidance Only excluding case amp batts 317 sounds There are two reasons for using a swept frequency alarm sound using the software a Changing sounds such as beepers sirens etc stand out much better from background noises and MEASURE R ROUTINE MAKE PIN 5 OUTPUT MAKE PIN 5 LOGIC 0 DISCHARGE CAPACITOR SHORT TIME DELAY 5ms RESET BOTH COUNTER REGISTERS OUTPUT PIN 6 l LOGIC 0 CHANGE PIN 5 TO INPUT MAKE PIN 6 START CHARGING LOGIC 1 INCREMENT COU
267. ty for which PIC wise users could write a software routine In this case it is suggested that key B is intercepted Backwards in a similar way to which letters C and D are intercepted Each time the digit number is stepped for ward the software increments a 24 value counter rolling over to again following 24 This not only provides information on which digit is selected from 1 to 8 but also on which Bank it is in Bank 0 to 2 using yet another look up table This results in Port A pins RAO RAI or RA2 being selected as appropriate in Bank order Referring back to Fig 6 again it will be seen that IC2 and IC3 are shown to be under selection control by pin RAO If additional IC2 and IC3 devices are used they would be allocated to one of the other Port A pins RAI or RA2 in that order of Bank In this way 24 digits can be stepped through by pressing key D the required number of times Yes it tests the user s counting ability but seemed the best solu tion considering the limited number of keys available The provision of monitoring via an alphanumeric liquid crystal display was considered but was rejected on the grounds of adding complexity to a moder ately simple design PIC knowledgeable readers could prob ably add l c d facilities if needed There are numerous examples of I c d control in many of the published EPE PIC projects especially in the author s designs Such a routine could
268. ufacturers dream up these totally unrealistic figures Well this is how it s done courtesy of Jake Rothman writing for our Modern Electronics Manual Say the true r m s output of an amplifier is 10W this expresses the power of an unclipped sinewave as a d c voltage producing the same power into a given say 8 ohm resistance The first stage of the trick is to use the term peak power which derives the power from the peak voltage so our 10W becomes 20W The next stage is to specify the output into 4 ohms so now we have 40W note that 90 per cent of speak ers are 8 ohm impedance Step 3 is to call it music power which because music is not continuous like a sinewave allows the output to be doubled again giving 80W Finally the two stereo channel outputs are added together to give 160W peak music power stereo you will usually see this quoted simply as 1 60W PMPO peak music power output As you can see it s a con try dividing it by 16 to get the true output In some cases manufacturers have gone even further and I have seen claims like 480W PMPO quali fied by 12W 12W r m s output at least they quoted the r m s figure So if you see audio output specifications that are not based on continuous sinewave r m s figures at a stated level of distortion then I suggest that you simply do not believe them You can tell the quality manufacturers by the way they quote their output figures There is basically no way that miniature
269. ught that the hetero geneuos structure of the semiconductor TITANIUM OXIDE PARTICLES WITH DYE Peete would lead to a high level of resistance within the device and large losses However the reverse is true and electrons are able to diffuse in the bulk matter towards the supporting conductor with almost no energy loss Also it does not suffer the same problem of a reduced percentage efficiency under low light conditions that traditional semiconduc tor cells suffer Traditional cells suffer from hole electron recombination in the semicon ductor and this reduces the efficiency par ticularly when light levels are low Now that the basic idea has been proven more research is ongoing to find some solid state substitutes for the liquid elec trolyte as this will make its manufacture much easier It will also enable the complete solar cell to be far more robust than it can currently be made Some ideas have already been tried and results using conductive polymers such as those used in light emit ting diodes may prove to be promising CONDUCTIVE GLASS PLATINUM MIRROR Se BOSS ELECTROLYTE X CO soe LOO FOO I 3 CIOS R EI OIA MORO TOO OOOO Oreh CONDUCTIVE GLASS Fig 1 Structure of the solar cell using organic dye and titanium oxide particles Another problem that is facing the researchers is that purifying some of the materials used in the new processes is nei ther cheap nor easy at the moment After
270. uild logic circuits to determine the direction of movement from the A and B signals in Fig 7 11 The simplest approach is to look at the level of say B when there is a positive edge on A i e at the instant that it changes from low to high Checking Fig 7 11 will show that a O indicates clockwise and a 1 indicates anti clockwise in this arrangement We can check the direction at any of the edges of the two waveforms in this way Each edge also represents a definite indica tion of movement and can therefore be used to increment or decrement a counter circuit depending on the direction The binary value in the counter will then represent the relative movement of the disc since the counter was last set to a particular value e g reset RESPONSE TIME The logic design for an incremental encoder can be a little tricky due to the need to prevent races between the direction discrimination and the counting It is fur ther complicated by the need to distinguish between definite movement in a particular direction and vibration about a basically fixed point which can continuously switch one of the sensors The latter problem prevents us from using the simple solution of connecting say A to the clock of an up down counter and B to the up down control The best approach is to sample the quadrature wave form using an external clock running at a faster rate than the fastest possible input signals and use a state machine to work out what
271. uit Dual scale meter compact case Reads up to 200 Megohms 4 spare electrodes 6 50 Kit includes wound coil cut out case meter scale PCB amp ALL components KIT 848 32 95 EPE PROJECT Programmed PICs for all EPE Projects 16C84 18F84 16C71 All 5 90 each 10 inc VAT amp postage TO HUMANS some projects are copyright KIT 812 TEACH IN 2000 Full set of to components for this educa tional series All parts as specified by EPE Kit includes breadboard wire croc clips pins and all components for experiments as listed in introduction to Part 1 Batteries and tools not included TEACH IN 2000 KIT 879 44 95 MULTIMETER 14 45 SPACEWRITER ty An innovative and exciting project LS Wave the wand through the air and ve your message appears Programmable to hold any message up to 16 digits long Comes pre loaded with MERRY XMAS Kit includes PCB all components amp tube plus instructions for message loading KIT 849 quality NEW 12V EPROM ERASER A safe low cost eraser for up to 4 ERPROMS ata time in less than 20 minutes Operates from a 12V supply 400mA Used extensively for mobile work updating equipment in the field etc Also in educational situations where mains supplies are not allowed Safety interlock prevents contact with UV KIT 790 29 90 SUPER BAT DETECTOR 1 WATT O P BUILT IN SPEAKER COMPACT CASE 20kHz 140kH
272. uit plus Binary notation Order Code VT301 VT302 55 minutes Digital Two Flip Flops will further enhance your knowledge of digital basics You will learn about Octal and Hexadecimal notation groups flip flops counters etc Order Code VT302 VT303 54 minutes Digital Three Registers and Displays is your next step in obtaining a solid understanding of the basic circuits found in today s digital designs Gets into multiplexers registers display devices etc Order Code VT303 VT304 59 minutes Digital Four DAC and ADC shows you how the computer is able to communicate with the real world You will learn about digital to analogue and ana logue to digital converter circuits Order Code VT304 VT305 56 minutes Digital Five Memory Devices introduces you to the technology used in many of today s memory devices You will learn all about ROM devices and then proceed into PROM EPROM EEPROM SRAM DRAM and MBM devices Order Code VT305 VT306 56 minutes Digital Six The CPU gives you a thorough understanding in the basics of the central processing unit and the input output circuits used to make the system work Order Code VT306 ORDERING Price includes postage to anywhere in the world OVERSEAS ORDERS We use the VAT portion of the price to pay for airmail postage and packing wherever you live in the world Just send 34 95 per tape All payments in sterling only send cheque or money order drawn on a UK bank Make che
273. uld be best if I could buy the mag every month I wish but I expect some other read ers may have the same problem and using the already excellent site would really help I now intend to construct the EPE Virtual Scope Jan Feb 98 Without asking you to give too much away should I go ahead or do you have any news of an updated version in the pipeline perhaps using your mastery of VB is flattery ok Derek Waite via email I wholeheartedly agree Derek that keeping the grey cells active is vital and enjoyable I m pleased to know we ve helped to inspire you and flattery is always welcome We shall actively consider putting Please Take Note on our FTP site thanks for the suggestion My Virtual Scope is the most advanced of all those I ve done There have been some simpler versions based around PICs since then but they are more limited than the VS I ve no plans to do another scope unless technology takes a quan tum leap forward again in some way regarding the hardware VB would only offer a cosmetic advantage not a physical one WHEELS A TURNING Dear EPE We need to measure distances on archeologi cal sites Did I see a project for a measuring wheel in EPE some time ago Philip Vallis via the net I replied to Philip that I had designed a PIC unit for use on my pushbike for distance etc and that it was published as PICagoras in two parts Apr May 97 Philip came back saying I am not
274. und knowledge Flashing LEDs digital to analogue converters simple oscilloscope charging curves temperature graphs and audio digitising Kit now supplied with our 32 bit assembler with 84 page supplement detailing the new features and including 7 experiments PC to PIC communication Flashing LEDs writing to LCD and two way data using 3 wires from PC s parallel port to PIC16F84 Book Experimenting with PCs 21 50 Kit 1a made up with software 52 00 Kit 1u unmade with software 45 00 C amp C for the PC Experimenting with C amp C Programmes teaches us to programme by using C to drive the simple hardware circuits built using the materials supplied in the kit The circuits build up to a storage oscilloscope using relatively simple C techniques to construct a programme that is by no means simple When approached in this way C is only marginally more difficult than BASIC and infinitely more powerful C programmers are always in demand Ideal for absolute beginners and experienced programmers Book Experimenting with C amp C 24 99 Kit CP2a made up with software 32 51 Kit CP2u unmade with software 26 51 Kit CP2t top up with software 12 99 The Kits The assembler and C amp C kits contain the prototyping board lead assemblies components and programming software to do all the experiments The
275. ut leads should be spaced as far apart as possible this is particularly important when the LM386N and TBA820M are set for high gain All of the circuits include high and low fre quency bypass capacitors across the supply rails The former minimise the possibility of r f oscillation the latter avoid low frequency instability when long power supply leads are used or when batteries are ageing HIGH FREQUENCY RESPONSE The bandwidth of the amplifiers extends into the r f spectrum and this makes the devices vulnerable to r f interference Some of the i c s pro vide for the connection of an external capacitor in a negative feedback loop to roll off the high frequency response Selecting an appropriate value for this component will help to make the device immune The problem of r f pick up invariably manifests itself when a high value more than 10 kilohms input potentiometer VR1 is used to match the amplifier to the impedance of a signal source If the poten tiometer or volume control must have a high resistance connecting a InF or at most 1OnF capacitor across its track will shunt unwanted r f to ground LOW FREQUENCY RESPONSE The low frequency response of three of the lower powered amplifiers has been curtailed a little by fitting a 220uF speak er coupling capacitor Amplifiers of this kind are invariably used with small inex pensive speakers which are incapable of producing an audible output at frequen
276. ve seen at 4 times the price Packed with information and illustrations R008 3 50 RADIO amp TV JOKER PLANS We show you how to build three different circuits for disrupt ing TV picture and sound plus FM radio May upset your neighbours amp the authorities DISCRETION REQUIRED R017 3 50 INFINITY TRANSMITTER PLANS Complete plans for building the famous Infinity Transmitter Once installed on the target phone device acts like a room bug Just call the target phone amp activate the unit to hear all room sounds Great for home office security R019 3 50 THE ETHER BOX CALL INTERCEPTOR PLANS Grabs telephone calls out of thin air No need to wire in a phone bug Simply place this device near the phone lines to hear the conversations taking place R025 3 00 CASH CREATOR BUSINESS REPORTS Need ideas for making some cash Well this could be just what you need You get 40 reports approx 800 pages on floppy disk that give you information on setting up different businesses You also get valuable reproduction and duplication rights so that you can sell the manuals as you like R030 7 50 308 PC CONTROLLED RELAY BOARD Convert any 286 upward PC into a dedicated auto matic controller to independently turn on off up to eight lights motors amp other devices around the home office laboratory or factory Each relay output is capable of switching 250VAC 4A A suite of DOS and Windows control programs are provided to geth
277. w 01110000 retlw 00000000 Q ro QA0 0 D The code is output on the 3 line com mon bus feeding to C4 and IC5 Which of these 1 c s is activated depends on whether the segment needs to be turned on or turned off To turn on C4 segment On bit 7 in the code is set high If IC5 is required seg ment Off bit 3 is set high Everyday Practical Electronics May 2002 It is also necessary to specify which of the digits is the target for the segment information This data is set into the code s bits 0 to 2 representing the number 1 to 8 of the digit in the allocated bank and des tined for IC1 see Fig 6 DIGIT SELECTION VIA KEYPAD Because the digits might be located away from the controlling keypad and not be visible to the user it was decided to allocate two keypad keys as digit stepping controls At switch on digit 1 is the default target and any numeric data keyed in con tinues to be routed to it To choose Digit 2 instead press keypad D Digit step This changes the control code fed to IC1 incrementing it from binary 000 to binary 001 so selecting digit 2 Display data is now repeatedly fed to this digit Pressing D repeatedly steps through each digit position in turn irre spective of whether the digit physically exists in the system To return to Digit 1 at any time press C Clear back to start It is not possible to step back individually from digit to digit This though is a facili
278. w cost analogue opto isolator using the HCNR200 Courtesy Agilent TR1 2N3906 7 6 SEE TEXT 4 D3 O BNC Fig 2 Circuit for a precision analogue isolation amplifier based on the HCNR200 Courtesy Agilent 362 Everyday Practical Electronics May 2002 It would be worth putting a variable volt age onto such an l e d and observing the out put The Toshiba 4N29 for example has an le d and a photo Darlington transistor which means the transistor output with load resistor from emitter to ground and collector to positive supply will produce an output proportional to the Le d s drive current Subsequently Mr Larner reverted with more details of an interesting device he had found after consulting Agilent the opto electronics offshoot of Hewlett Packard The Agilent HCNR200 is a high linearity analogue opto coupler containing a high efficiency l e d that illuminates two close ly matched photodiodes see Fig 1 The input side photodiode D1 can be used to stabilise the light output of the l e d D2 so that the non linearity and drift of the l e d can be eliminated The Agilent HCNR200 claims 0 25 non linearity and the higher spec HCNR201 0 05 maximum non linearity You can download the data sheet from www agilent com They are available from RS Components rswww com e g the HCNR200 Part No 801 465 is listed at 2 47 excluding VAT and P amp P Other lin ear opto couplers are also
279. ware in order to use the PlCmicro development board I also now notice that the PICTutor software does not appear to work on Windows 2000 either Chris Ringrow Linden Alhampton Somerset via email Chris you have misunderstood PICtutor and Toolkit are not related to each other PICtutor is to teach about PICs with reference to the PICI6F84 which the Tutor board will handle Toolkit 3 is for those who are experi enced PIC programmers for use in developing their own programs As said in the article Toolkit does not run under Win2000 although we have an article in the pipeline which gives details of using it with 2000 and XP PICtutor runs under any Windows format but if you have problems you should contact the manu facturers Matrix Multimedia 353 MSF WWVB AND BBC Dear EPE Andy Flind s answer to Steve Davenport s email Mar 02 prompted me to look up the original article which was July 01 not July 98 as quoted Since WWVB broadcasts on the same frequency as MSF 60kHz there seems every chance that the MSF repeater will work with WWVB without modification I wonder if Steve is aware of www boul der nist gov timefreq stations wwvb htm It wasn t until I did a Google search on WWVB and spent 30 minutes trawling through this splendid site which although not totally relevant unless you live in the US has some excellent info about time and related topics Barry Taylor Rickmansworth via email
280. who is new to PIC programming We begin with four simple experiments the first of which is explained over ten and a half pages assuming no starting knowledge except the ability to operate a PC Then having gained some practical experience we study the basic principles of PIC programming learn about the 8 bit timer how to drive the liquid crystal display create a real time clock experiment with the watchdog timer sleep mode beeps and music including a rendition of Beethoven s Fur Elise Finally there are two projects to work through using the PIC16F84 to create a sinewave generator and investigating the power taken by domestic appliances In the space of 24 experiments two projects and 56 exercises the book works through from absolute beginner to experienced engineer level Ordering Information Telephone with Visa Mastercard or Switch or send cheque PO for immediate despatch All prices include VAT if applicable Postage must be added to all orders UK postage 2 50 per book 1 00 per kit maximum 7 50 Europe postage 3 50 per book 1 50 per kit Rest of World 6 50 per book 2 50 per kit Web site www brunningsoftware co uk Mail order address NEW 32 bit PC Assembler Experimenting with PC Computers with its kit is the easiest way ever to learn assembly language programming If you have enough intelligence to understand the English language and you can operate a PC computer then you have all the necessary backgro
281. with a plug top power supply the Export Version has a battery holder all switches for both PIC ports plus I c d and 4 digit 7 segment I e d displays It allows users to program and control all functions and both ports of the PIC All hardware is supplied fully built and tested and includes a PIC16F84 ELECTRONIC COMPONENTS PHOTOS A high quality selection of over 200 JPG images of electronic components This selection of high resolution photos can be used to enhance projects and presentations or to help with training and educational material They are royalty free for use in commercial or personal printed projects and can also be used royalty free in books catalogues magazine articles as well as worldwide web pages subject to restrictions see licence for full Deluxe PiCtutor Hardware ELECTRONIC CIRCUITS amp COMPONENTS V2 0 Provides an introduction to the principles and application of the most common types of electronic components and shows how they are used to form complete circuits The virtual laboratories worked examples and pre designed circuits allow students to learn experiment and check their understanding Version 2 has been considerably expanded in almost every area following a review of major syllabuses GCSE GNVQ A level and HNC It also contains both European and American circuit symbols Sections include Fundamentals units amp multiples electricity electric circuits alternating circuits
282. x 150mm x 200mm an i c holder will permit the 2in x 6in x 8in aluminium box would substitution and checking of be more than adequate as a heatsink the low power amplifiers Insulating washers are not required but a However if reliance is to be smear of heat transfer compound should be placed on the p c b foil for applied minimal heatsinking of the LM380 the device should be COMPONENTS soldered directly in place Slight differences in the i c type num Solder pins inserted at the bers can cause confusion The LM386N 1 lead out points will simplify has the lowest power rating of this group of off board wiring devices The suffixes N 3 and N 4 It may help to start con indicate devices rated at 700mW and 1W struction of the chosen cir respectively The suffix M indicates sur cuit board by first placing face mounting Suppliers offering the and soldering the i c holder gt 90 the inverters generate very little heat The high stability of the Aerucioncs 150W TO 2500W 12V amp 24V output frequency 1 makes them equally suitable to power sensitive devices These inverters generate a modified sine wave which are considerably superior to the square waves which are produced by most other inverters Due to this superior feature they are capable of powering electrical equipment such as TV s videos desktop amp notepad computers microwave ovens electrical lamps pumps battery chargers etc Low Battery Al
283. xplanation of the circuit operation and a stripboard layout diagram All constructional details are provided along with a shop ping list of components and none of the designs requires the use of any test equipment in order to set up properly All the projects are designed for straight forward assembly on simple circuit boards Circuits include High impedance mic preamp Low impedance mic preamp Crystal mic preamp Guitar and GP preamplifier Scratch and rumble filter RIAA preamplifier Tape preamplifier Audio limiter Bass and treble tone controls Loudness filter Loudness control Simple graphic equaliser Basic audio mixer Small 300mW audio power amp 6 watt audio power amp 20 32 watt power amp and power supply Dynamic noise limiter A must for audio enthusiasts with more sense than money Order code PC113 10 95 250 pages 116 pages RADIO TV VIDEO ELECTRONIC PROJECTS FOR VIDEO ENTHUSIASTS R A Penfold This book provides a number of practical designs for video accessories that will help you get the best results from your camcorder and VCR All the projects use inexpensive components that are readily available and they are easy to construct Full construction details are provided including stripboard layouts and wiring dia grams Where appropriate simple setting up procedures are described in detail no test equipment is needed The projects covered in this book include Four channel audio mixer Four channe
284. z NEW DESIGN WITH 40kHz MIC A new circuit using a full bridge audio amplifier i c internal speaker and headphone tape socket The latest sensitive transducer and double balanced mixer give a stable high perfor mance superheterodyne design KIT 861 ALSO AVAILABLE Built amp Tested 39 99 ULTRASONIC PEsT SCARER Keep pets pests away from newly sown areas fruit vegetable and flower beds children s play areas patios etc This project produces intense pulses of ultrasound which deter visiting animals e KIT INCLUDES ALL COMPONENTS PCB amp CASE e EFFICIENT 100V TRANSDUCER OUTPUT PIC16F877 now in stock e COMPLETELY INAUDIBLE iS magos U L T H fa a a H I e UP TO 4 METRES RANGE e LOW CURRENT DRAIN Everyday Practical Electronics May 2002 SIMPLE PIC PROGRAMMER INCREDIBLE LOW PRICE Kit 857 12 99 Power Supply 3 99 EXTRA CHIPS PIC 16F84 4 84 INCLUDES 1 PIC16F84 CHIP SOFTWARE DISK LEAD CONNECTOR PROFESSIONAL PC BOARD amp INSTRUCTIONS Based on February 96 EPE Magenta designed PCB and kit PCB with Reset switch Program switch 5V regulator and test L E D s and connection points for access to all A and B port pins PIC 16C84 DISPLAY DRIVER Kit 860 19 99 Power Supply 3 99 FULL PROGRAM SOURCE CODE SUPPLIED DEVELOP YOUR OWN APPLICATION Another super PIC project from Magenta Supplied with PCB industry standard 2 LINE x 16

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