LC Meter User Guide for V1.2 PCB
Contents
1. ooooccconnncccconccccoccococcoconoonnnanronnananonnnnnnos 29 Power SUDDIY SO CHO recat tude p 29 CS GIN ATOR taa 30 Microprocessor SSCUOIN ict a pads eri 31 FG SOT AN asana E pem n na E na KA aa acco eu de einai a Da ANG dan DUI a a aka ae 32 Appendix A L C Meter V1 2 Schemaltlo eoe ads 34 Appendix B1 PGB VT 2 Parts Listones 35 Appendix B2 Additional Parts List eleeeeeeeeeeeeeeeee esee e eene enne nnn 36 al A AS 36 Appendix C1 PCB V1 2 Unassembled ccooonccccccccccccccnccccconacononcncnnnrononaronannnnnannnrnnanenannos 37 Appendix C2 PCB V1 2 Assembled 0cccocnccconocicocococonoconcnnocnnanonnnronnnnronnnnronnnnrnnannnrnnarenanns 38 Appendix D PCB V1 2 Copper Pattern not to scale 39 Appendix E Box Top Drill Drawing eeeseeesseeeee eene eren nene nnne nennen 40 Appendix F Side Panel Drill Drawing ee eese eeeee eene 40 Appendix G Resistor Colour Code Chart 1 eeeceeeeeeeee eene eene nnne nnn nn 41 Document History Issue Date Changs O 12 June 2009 13 July 2009 Assembly step 5 16 changed cable to cable tie 1 November 2009 Assembly step 5 13 added alternate orientation marks for K1 Issue 3 Copyright O Debug Innovations Ltd 20092. L C Meter User Guide Page 32 of 41 U1 is a PIC microprocessor which runs the meter software U3 is a latch which is used to increase the number of I O pins on the PIC Pins RBO 3 are treated like a data bus and are labelled DO 3 on the circuit The bus goes to the LCD display and U3 LCD_EN goes high when the software wants to send data to the LCD and LATCH_EN goes high when the software wants to send data to U3 In this way DO 3 are used for two purposes effectively adding 4 pins to the micro less LATCH_EN gives a net gain of 3 pins This only works because we never read from the LCD pin 5 R W is tied to GND VR1 controls the contrast of the LCD display R11 reduces the range of VR1 so that the display text is still visible at any setting of VR1 Y1 and C10 C11 are connected to the PIC s internal oscillator circuitry to produce a 4MHz CPU clock This PIC also has an internal clock but it is not stable enough for this application as we are measuring the oscillator frequency using the CPU clock frequency as a reference SW2 zero button and R1 are connected to one of the PIC s digital inputs PIC Software With this project the real magic happens in the software A full description is beyond the scope of this section but the basic principles are described To measure the oscillator frequency one of the PIC s internal counters we will call it OSC is connected to the output of COMP2 see oscillator section and another is conne
3. R6 R8 47K 100K dug C4 zen Li 68uH 10uF R10 5 4K7 gt J1 1 C5 18 Comp 2 680pF gt FOSC Y GND We need to change the configuration because putting low value inductors in parallel with L1 would result in unacceptably high resonant frequencies over 100MHz which are outside the comparator s capabilities With this configuration adding inductance reduces the frequency as did adding capacitance in C mode The function of C6 shown on the full circuit is to calibrate the oscillator It is the only precision component in the circuit and sets the basic accuracy for the meter Relay K1 switches the capacitor in and out of circuit as if it were a component under test in C mode The calibration procedure is described in detail in the PIC Software section below Diodes D2 and D3 conduct away the high voltage inductive switching spikes which occur when the relays are switched off and could otherwise damage U3 Microprocessor Section LATCH EN U3A FALS75 POWER HOLD VCC R11 10K 10K aa VCE e ZERO BUTT VRI A x2 of B R10 6 ZERO sa d E 2 PIC 16F 648 4 sad 9 m 6 DO BE AA A El E A GND A a RAZ AN2 VREF dd SS E RA3 AN3 CMPI1 RB3 CCP1 10 LCD EN E gt RA4 TOCKI CMP2 RB4 PGM 11 LATCH EN RAS MCLR VPP RB5 12 LCD RS RA6 OSC2 CLKOUT RB6 TIOSO TICKI PGC 4 RB7 TIOSI PGD 13 Yi MEG 4MHz 14 V I GND c10 C11 22pF 22pF Issue 3 Copyright Debug Innovations Ltd 2009
4. LCD Display L C Meter User Guide Page 3 of 41 L C Meter User Guide This section explains how to use your L C Meter If you have not yet built the meter proceed to the Kit Assembly Instructions section If you have any questions or are unsure about what is meant by anything please email support debuginnovations com and we will be pleased to assist you Overview An L C meter is a very useful piece of test equipment Most people have access to a multi meter which can measure resistance Some multi meters have a basic capacitance measuring facility and low cost commercial capacitance meters are also available However inductance L measurement is a lot trickier Most low cost commercial inductance meters are designed for measuring power transformers and the like with inductances in the milli Henry and Henry range For RF work we need a meter that works down to micro and even nano Henrys This meter is specifically designed for measuring small value capacitors 1uF and inductors 100mH These are the types of components used in RF designs The meter works by measuring the resonant frequency of an LC circuit where either the L or the C is the component to be measured This method has the advantage that very small values can be measured accurately L s down to a few nH and C s to a few pF It also means that the L C is measured at high frequencies the sort of frequency you are going to use them at Although similar to
5. GND The oscillator is formed by COMP1 COMP2 is just used as a buffer so that loading on FOSC has no effect on the oscillator frequency R6 and R7 bias the non inverting comparator inputs to half the supply Feedback keeps the other comparator inputs within the operating range C4 prevents L1 shorting out the bias and isolates the bias from the component under test L1 and C5 form an LC parallel resonant circuit with a resonant frequency of around 700KHz In C mode the component under test adds capacitance in parallel with L1 C5 reducing the frequency With large capacitors the frequency can get quite low so C4 needs to be a high value requiring an electrolytic capacitor However we also need good high frequency performance so we have to use a high quality low ESR capacitor COMP1 switches on every cycle of the sine wave from the LC circuit As the output switches the fast edge sends a spike of energy through C12 to keep the LC circuit oscillating Positive feedback from R8 keeps the oscillator running and the network formed by R9 and C3 ensures the inverting input of COMP1 lags behind the non inverting input At switch on C3 takes time to charge up ensuring COMP1 has a known starting state and the oscillator starts reliably Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Page 31 of 41 In L mode relay K2 reconfigures the circuit so that L1 is in series with the component being tested as shown below VCC C12 5pF X
6. using a non conductive tool Larger leaded devices should have their leads bent at right angles to the connector bar this will stop the component sliding along the connector as pressure is applied Be careful not to touch the component leads or any conductive parts of the component as this will change the reading If you have to touch the leads e g when testing variable capacitors where the shaft is connected to one side make sure it is the ground side as indicated by the ground symbol on the PCB see photo Measuring Capacitance To measure a capacitor first switch to capacitance mode press the L C button until you see C on the left of the display With no component connected the display should read OpF if it doesn t press the zero button Next connect your capacitor to the component connector taking care not to touch the leads The value will be shown on the display The range is automatically chosen and the value is displayed in the appropriate units If the component is on the borderline between two ranges the meter may switch ranges as you move the component in the connector but built in hysteresis ensures the meter will not hunt between ranges Electrolytic capacitors do not resonate well in an LC circuit and will not give a reliable reading with this meter Non electrolytic capacitors can be measured from a few pF up to about 1uF Over Range is indicated at 1 5uF Capacitors with significant ESR or inductive connecti
7. 765 br aS KA s mu Y e e e MAS 4 ON Solder the display end of J2 to the LCD display Cut off the excess length of J2 with wire cutters at the display end the bit poking up from the display PCB The 2 display mounting screws at the right hand side of the photo above need to be shortened to avoid fouling the edge of the box Cut the excess length off with a hacksaw or bolt cutters or even an old pair of wire cutters Be careful that the loose piece doesn t fly off and hurt someone put your hand over the job and wear safety goggles Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 24 of 41 Step 7 Testing amp Calibration After assembly the unit needs to be tested before use as follows 1 With the PCB out of the box and on an insulating surface attach a battery and press SW1 The power should come on you may also see something on the LCD Measure the voltage between U1 pin 14 and GND It should be approximately 5V If it is not there is a fault with the power supply on the board first check the battery is good then check D1 is fitted the correct way round If you see a very low voltage on pin 14 check for a short between VCC and GND If you get 5V only when SW1 is pressed down refer to the power supply description in the circuit operation section Peel off the protective film from the LCD display and adjust VR1 for the best contrast At one extreme the background wi
8. V1 2 S N 0002 Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 8 of 41 un 2 2 a E m 3 2 AS Qu Once opened you should have the following items Ensure you have all the items before proceeding 1 An envelope containing the top panel artwork 2 The pre cut box includes battery clip and box screws 3 A peg used for soldering the component connector 4 The PCB V1 2 5 The LCD display 6 The 74LS75 chip 7 Relay K2 8 The PIC chip its socket and relay K1 9 A bag containing the mechanical parts 10 A bag containing the rest of the electronic components Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Step 2 Component Identification First check you have the correct PCB version V1 2 The version number is shown on the Page 9 of 41 solder side of the PCB etched in the copper as shown below PCB Version Number Open the bags and check you have all the components on both parts lists see Appendices B1 amp B2 Resistors All the resistors are through hole types There are 4 different values Appendix G shows the Q resistor colour codes If in doubt measure them with a multi meter Issue 3 Copyright O Debug Innovations Ltd 2009 Ro Jak L C Meter User Guide Page 10 of 41 Variable Resistors You should have one preset potentiometer VR Capacitors All the capacitors should be identifiable from their markings They may n
9. both small capacitors and inductors it is very important to keep your hands well away from the connector to avoid stray capacitance affecting the reading Test Mode To enter test mode start with the unit turned off Hold down the zero button and turn on the unit After a few seconds the display will show Test Mode and then display the oscillator frequency Pressing the zero button will toggle between Fosc and Fecal Fosc is the oscillator frequency with the calibration capacitor disconnected from the circuit Fcal is the oscillator frequency with the calibration capacitor connected to the circuit Pressing the L C button will exit test mode and go into normal operation mode WARNING Auto power off does not function in test mode the unit will stay on until the battery goes flat Error Messages If the unit fails you may get one of the following error messages Oscillator Fail is displayed when the oscillator doesn t start at power on This may happen if you leave a component connected or a short develops on the component connector Calibration Fail is displayed if the calibration capacitor doesn t have the expected effect on the oscillator frequency during the calibration process Again it can be caused by components on the component connector If this happens and you are sure there is no interference from external components put the unit in test mode and check the frequency with the calibration capacitor in and out of ci
10. is higher than in C mode The ratio of the two frequencies is given by l m gt A CFC Stray where C Deliberate Capacitance and Cstray Stray Capacitance When measuring Fo C 680pF When measuring Fea C 1680pF i e 680pF the 1nF calibration capacitor Cstray is constant for our PCB layout We use this formula to obtain equivalent calibration frequencies for L mode based on the numbers we get in C mode Test modes and error messages are described in the User Guide section The rest of the software is straightforward Mode switching and zeroing using the buttons measurement auto ranging and driving the LCD display The only other thing worthy of merit is just how difficult it is to squeeze all the software into the chip It is all written in C and the maths takes up too much space so in reality the maths becomes even more complex because we cannot afford the luxury of square roots for example Issue 3 Copyright Debug Innovations Ltd 2009 Page 34 of 41 L C Meter User Guide Appendix A L C Meter V1 2 Schematic qo Lina OT sa do1 Na HOLVT YAMOd Taso Tu 91 vV8r949TOId In SES TRL din SLOT RL en Aadzz 1950 LXV ora 92A JUDOT JIAN TOU A001 La JJA 1 AUT 44089 Hip 902 o 64 Mir Ru A Anor r2 ads z12 001 ou IND 22A OYAZ ZAS ee 2 on Lind ONSZ LAS 2 MOI Tu Lind 21 Srl PNT sa 229A 8PIENT va MOI pu MOI JUDO JUD
11. measure them with a multi meter Fit inductor L1 68uH Refer to the component photographs to correctly identify L1 Fit diodes D1 to D3 1N4007 and D4 amp D5 1N4148 Ensure they are fitted the correct way round Fit the socket for U1 Even though it is a socket make sure the notch is at the correct end Fit capacitors C7 to C9 100nF C10 amp C11 22pF and C12 5pF Fit quartz crystal Y1 4MHz Fit Q1 BC337 Q2 BC327 and U2 78L05 Be careful as these devices are very similar Fit VR1 2K2 Preset Fit capacitors C5 680pF C6 1nF 196 Fit capacitor C4 10uF low ESR Do not mix this up with the other electrolytic capacitors It is brown in colour the others are black This is a polarised component that needs to be fitted the correct way round The long lead should be inserted through the hole marked on the PCB legend Copyright Debug Innovations Ltd 2009 Comp J1 L C Meter User Guide Page 22 of 41 11 Fit capacitors C1 10uF C2 100uF and C3 2 2uF These are polarised components that need to be fitted the correct way round The long lead should be inserted through the hole marked on the PCB legend 12 Fit relay K2 It only fits one way round Solder two corner pins first and check it is flat to the PCB before soldering the rest of the pins 13 Fit reed relay K1 Depending on the make the package has a sloped end or a dot cutout similar to an IC identifying pin 1 P
12. 9 Accurately cut the two straight edges to the correct size for the recess in the top of the box The right hand edge of the display is lined up exactly with the edge of the recess so first cut the right hand side exactly along the edge of the display bezel s black printing Then place the label in the box recess to judge where to cut the left hand edge 10 Peel off the other side of layer c and carefully press the label into place on the box Start by pushing the edge of the label against the right hand edge of the recess then lay the label down at this point the bezel of the display should be completely covered by the label and the buttons should line up with their legends on the label 11 Using a small screwdriver or the back of a knife press the overlapping label edges into the edges of the box s label recess Then run a scalpel along the edge to cut the label to fit the curved edges 12 Clean any fingerprints etc from the finished label You may also need to unscrew the lid of the box and clean the back of the display window and or the LCD display itself Finally you will probably need to clean the scissors knife blade with label remover fluid or similar to get rid of the glue residue Finally check the unit still operates as expected Your L C Meter is complete We hope you enjoyed building this project Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 29 of 41 L C Meter V1 2 Circuit Operatio
13. L C Meter User Guide Page 1 of 41 caphrc y Y i vn m G Um T a L C Meter User Guide Important Always use or print this document in colour as there are references to the colours of components Errors may occur otherwise Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Page 2 of 41 Contents COMENS a a ene ces 2 DOCUMENE HISTO Vd 2 L C Meter User Guld mee ios 3 OVEIVIe Wesce E D E E eer ee met a 3 POWE POMO aana E 4 Basic Op ration seinne TE ia 4 Measuring Capacitance in ios 4 Measuring Indtctance mida 5 The Zero BULA 5 Measuring Low Value Components occccconnncccccnncocncnncoconcnnnonanonnnnonnnononnnnnnnannnnnnonnnnnnonnnnnnnanos 5 Test Modena o a li do Ol akad 6 EGON WIGS SAG CS uta A 6 Replacing Ine Bale ia AAA iga 6 LC Meter V1 2 Kit Assembly Instructions ooocccconncccconcncoconconocnnnnccnnnancnnnnnanonnnnnnrrnnanaronananennas 7 SteD T UNPACKING OU e 7 Steb 2 Component IGSMtiiGatlOn aaa aaa nig aana ag tere et A Aa tet ja ees eee a 9 Step 3 Preparing For PCB Assembly cerei dia 16 Step 4 Component Connector Assembly saanane a nean e anana anaa anana naen e anna ane eee 19 Stepo Component ASSEMmDIY o 21 Step 6 LCD Display Assembly oi id 23 Step Testing CallBFallOl s aaa 2 erii a AS a os 24 Step Os BOX ASSOITIDD aaa asana ida 25 SEN The Box TOB Label arusa kasan so dao otro Geax 27 L C Meter V1 2 Circuit Operation How It Works
14. O ant cu 20 Lo oO q CO L DFNT ajeJqme2 L OFNT B T f TasOTU aNd A duo If Q O Temps OTL dL ee ZA JDA Hng9 VI IND de poseer NI ra ndi OF XUL 7a TIOH YAMOd Letoa 10 AND A ef LOOPNT Id Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Page 35 of 41 Appendix B1 PCB V1 2 Parts List Part Type Footprint Qty Part Number R1 R5 R11 AXIAL 0 4 6 RAP 62 0897 RS 148 736 R6 R7 100K AXIAL 0 4 RAP 62 0964 RS 148 972 R8 R9 AXIAL 0 4 RAP 62 0942 RS 148 893 AK7 AXIAL 0 4 RAP 62 0862 RS 148 663 VR1 2K2 PRESET 1 RAP 67 0220 CAP_RAD_2P_5D RS 475 9043 FN 945 2281 C2 100uF CAP RAD 2 5P 6 5D 1 RS 475 8826 o 1 EN1IS888 6 3535353535353 C 1mF T6 O 1 RSTIZ814FN 1413948 00 0 FN 941 1674 MEE AAA A IND_AXIAL 0 5 RAP 88 2830 FN 608 531 D1 D3 1N4007 DIODE 0 4 RAP 47 3142 FN 956 5051 D4 D5 1N4148 DIODE 0 3 RAP 47 3308 FN 956 5124 BC337 TO 92 FN 122 8215 BC327 TO 92 FN 109 7285 PIC16F648A DIP 18 RAP 73 2654 FN 976 0490 RS 623 0320 78L05 VREG 78LXX MS 512 LM78L05ACZX FN 146 7367 74LS75 DIP 16 RS 305 119 FN 110 6076 J3 NENNEN CAU PO E EE K1 Calibration Relay Reed Relay 1 DK 306 1062 ND FN 108 1682 RAP 60 0670 RS 479 1457 AS EE AA HO eee pT TOTAL COMPONENTS U1 needs to be programmed before assembly The blank part number is given above Parts supplied in the kit are already programmed Issue 3 Copyri
15. OKO tin can type can also contain other components notably capacitors in parallel with the inductors Obviously these will not give reliable readings Inductors from around 100nH to over 100mH can be measured accurately with this meter though stray inductance can be challenging at less than 1uH Try to measure close to the component body rather than at the ends of the leads One situation in which this meter is particularly useful is when winding your own coils A little known fact is that cores such as the popular toroid types used in amateur radio designs have quite a wide tolerance of 20 This means that you may have to wind 20 more or less turns to get the inductance you need something that can be very important for oscillators or filters This meter takes the guess work out of winding you own coils With a purely inductive component the accuracy of the reading is about 1 except for values at the extreme ends of the range e g lt 100nH The Zero Button The zero button has several uses It can be used to zero out small inaccuracies when measuring low value components see next section or it can be used for deliberate adjustments For example to select matching components from a batch of 1nF capacitors first measure a capacitor then with the component still connected press the zero button When you remove the capacitor the display will read 1nF Connect the next capacitor and the display might read say 10pF which means t
16. ar but they are clearly marked with the part number Be careful not to confuse them with U2 which also looks the same Q1 BC337 Q2 BC327 Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Page 13 of 41 Integrated Circuits You should have three ICs and an IC socket The ICs are marked with their part numbers U1 PIC16F648A Programmed 18 pin IC socket for U1 U2 78L05 3 U 7T4LS75 U1 is supplied pre programmed and is fitted in the IC socket U3 must be soldered directly to the board to maintain clearance from the LCD display which is mounted above U3 Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 14 of 41 Crystal You should have one quartz crystal Relays You should have two relays K1 Reed Relay ce w EDR101A0500 Miniature Relay Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Switches You should have two push button switches Connectors There are 3 connectors Issue 3 Copyright Debug Innovations Ltd 2009 Page 15 of 41 SWI 8 SW2 Push button J1 Component Connector made from square section brass tubing Display Connector Battery clip Supplied with case L C Meter User Guide Page 16 of 41 LCD Display You should have an LCD display DISP1 16 x 1 line Alphanumeric LCD Pre drilled Case The case comes pre cut in 3 parts and is held together with a pair of self tapp
17. cted to the 4MHz CPU clock we will call it TIME The CPU clock is used to wait a fixed length of time about half a second after which the OSC counter is stopped The frequency is then calculated as OSC TIME Ordinarily we can calculate an L or C value from the frequency if we know one of the L C values However the accuracy of the meter would depend on how accurately we know the value of the L C This isn t too difficult with capacitors but precision inductors are expensive and inductors wound on metal cores are temperature sensitive To avoid this problem we use a calibration capacitor We can derive a formula which effectively compares the frequency with and without the known calibration capacitor against the frequency with the unknown component The clever thing about this formula is that since we are only making relative measurements and the value of L doesn t change between measurements L cancels out and we don t need to know the actual value of L This means we can use a cheap component for L1 and avoid the problem of knowing the value of L The software measures three oscillator frequencies Fo is the frequency with no component connected and no calibration capacitor Fa is the frequency when the calibration capacitor is switched in circuit F is the frequency with the unknown component connected In C mode we use this formula for finding the component value 2 PET el F C 5 XC LUN NE Du Issue 3 Copyright O Debug Inn
18. er doesn t work you may find it useful to read the circuit operation section to help with fault finding Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Page 25 of 41 Step 8 Box Assembly 1 Slide the end panel over the component connector and drop the PCB into the box You will find the PCB is a snug fit in the box and if you haven t taken care with the placement of the display spacers the end panel will bow out refit the display spacers if this happens EP ye late Asayjeg eujeyjy jeuorssojoJd 2 Screw the PCB in place with the 4 self tapping screws provided 3 Put the top on the case being careful not to squash the battery lead in the box edges Fix the top and bottom halves of the box together with the two long screws supplied Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Page 26 of 41 4 Next the button spacers must be fitted Carefully drop the spacers through the button holes in the box top on to the button shafts Using something flat press the spacers down until they are flush with the box top When released the spacers will poke through the box top by a small amount the button plunge length Li Pot gt 5 Put a drop of cyanoacrylate adhesive super glue in the middle of the spacer It will run round the button shaft by capillary action and form a strong bond If you push the spacer in too far and glue it in place you will never get the spac
19. er off again so make sure the spacer is in the correct place before gluing it Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 27 of 41 Step 9 The Box Top Label The label for the box top is made as follows 1 Find a clean well lit flat surface Before starting wash your hands any tiny bits of dirt will ruin the appearance of the front panel 2 The panel is made from 3 layers see photo above a A transparent film printed with the buttons and other text This is the top layer One side is smooth and shiny this side will become the final box top the side the user touches The other side is rougher and is printed with a reverse image Be careful not to touch the printing when making up the label b A white plastic sheet printed with a template for the display bezel One side is printed and the other has a self adhesive backing c A double sided adhesive sheet These layers will be referred to as layers a b and c below Make sure you know which layer is which and are clear about which side is which before starting 3 Peel off the backing on one side of layer c and stick it to the printed side of layer b i e cover up the printing The printing will still be visible through layer c Trim the excess sticky edge with scissors to make it easier to handle You now have a sandwich with a b and a c side 4 With a scalpel or very sharp knife cut a square hole for the LCD dis
20. ges Appendix F Side Panel Drill Drawing 94 Not to scale for guidance only All dimensions in mm Issue 3 Copyright O Debug Innovations Ltd 2009 Page 41 of 41 L C Meter User Guide Appendix G Resistor Colour Code Chart LEON AVDIO Be Edgeware Road Aldgate South mim 5154 Internet http Iw E OM AUG CO au Resistor Colour Code 2 MM 30 5 E o NN a 8 9 o HA EN 2 MN 3 p un 5 ES c NEN 4 8 Jamu o Bg 1 2 E 3 p 4 5 E o E 7 ES 8 jam 1 E 2 IN 3 p unn 5 E o NEN 9 Band Code 237KKA 1 1st circle 2nd circle 3rd circle 4th circle 5th circle 1stfigure 2nd figure 3rd figure number of tolerance zeros i EE 02 E TA 0396 ES 0 05 Uu NE 01 4 Band Code 060 Band Code 47K amp 5 Issue 3 Copyright Debug Innovations Ltd 2009
21. ght O Debug Innovations Ltd 2009 L C Meter User Guide Page 36 of 41 Appendix B2 Additional Parts List Part Number PCB Custom approx 100mm x 70mm pte Box ABS with PP3 battery compartment 1 MS 546 1553BGYBAT RAP 30 3096 FN 100 9442 RS 513 5296 HP Premium Transparency Film Label Top Inkjet 1 EurOffice HP C3835A Label Backing Mega Quick Laser Labels RAP 37 1782 Label Adhesive Double sided A4 adhesive sheets HandyHippo co uk Display Spacers M3 x 8mm nylon 4 RAP 33 3660 FN 666 889 Button Standoffs Standoffs for buttons M3x8 nylon 2 RAP 33 3660 FN 666 889 Note that the display spacers and button standoffs are identical i e you will find 6 of the same part supplied Parts List Key Designator A unique identifier for this part on the board e g R1 C1 Q1 etc This can be given as a range or list e g C1 C3 means C1 C2 and C3 The shape of the area on the PCB for the component Often this translates to the package style e g the same value of resistor comes in several different sizes transistors come in standard cases e g TO 92 and you can often get the same IC in a DIP or a surface mount package Quantity required on the PCB A blank indicates that the component is accounted for somewhere else A quantity of zero indicates that there is a space on the PCB but the component is not fitted in the standard build Part Number Part numbers are for guidance only and all part numbers shown are suitable howe
22. he second capacitor is 10pF lower in value than the first 990pF if the first capacitor was exactly 1000pF If the reading is 12pF that means the capacitor is 12pF higher than the first part When switching from L mode to C mode or vice versa any offset caused by pressing the zero button is automatically reset equivalent to switching the unit off and on again Measuring Low Value Components Theoretically the unit should read OpF on power on In practice the oscillator frequency drifts slightly and the reading changes in response If you are trying to measure components with very low values e g lt 10pF and lt 100nH leave the unit on for a few minutes you may have to keep switching it on after auto power off to stabilise the oscillator then recalibrate switch off and on then take the reading Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 6 of 41 With low values it is important to avoid stray inductance and capacitance Stray capacitance is calibrated out automatically by the meter at power on Stray inductance is compensated for by the software based on measurements of the PCB characteristics However this is not enough for measurements of inductors below about 100nH The best way is to warm up the unit as described above then zero the inductance range using a zero ohm resistor or piece of wire in the gap between the component connector bars Then the inductor under test can be measured When measuring
23. he state of SW1 is sensed by the microprocessor through D5 there is a pullup resistor inside the PIC on the signal LC BUTT When pressed LC BUTT goes low when released the pullup pulls LC BUTT high The software turns the power off by pulling POWER HOLD low This occurs after 2 minutes of non activity or when the user holds SW1 down for 2 seconds C1 decouples the input of U2 C2 provides bulk storage decoupling for the rest of the circuit Capacitors C7 C9 provide local decoupling for U1 U3 and the LCD display Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Page 30 of 41 Oscillator Section R R10 100K C12 5pF 1 4K7 C4 10uF LEEREN R8 47K PIC16F RI 47K 17 RADANO jai RIE ER PA ee ze a DS 2 mE C5 C6 680pF InF 1 RA3 AN3 CMP1 gt RA4 T OCKI CMP2 O VCC RAS MCLR VPP RA6 OSC2 CLKOUT D2 p 16 RATIOSCI CLKIN Calibrate 1N4007 2 2uF YI 4MHz 5 R7 VSS 100K 22pF 22pF V nLCSEL nCAL GND The oscillator is the heart of the L C meter It is not easy to understand from the real circuit diagram above because the active part of the circuit is inside the PIC The equivalent circuit is shown below using the same component designators as the real circuit The PIC pin numbers are also shown pin 1 being connected to both comparators inside the PIC VCC C12 5pF Sa R R8 47K 100K R9 47K C4 pi 10uF R10 x 4K7 Comp 68uH 680pF gt FOSC R7 100K o 2 2uF Y
24. in 1 goes at the shaded end of the legend 14 Fit buttons SW1 amp SW2 They snap into place with a little pressure Be careful to get them really flat to the PCB surface 15 Fit U3 74LS75 Ensure it is fitted the correct way round The pins may need teasing inward as they are supplied splayed outwards DO NOT use an IC socket U3 must be soldered directly to the board or it could foul the underside of the LCD display 16 Fit J3 Battery Clip First shorten the lead to remove some of the excess length the lead only has to reach as far as the battery compartment The correct length is approx 50mm Solder the ends to the board using the 2 pads marked J3 Bait The positive red lead should go to the square pad marked and the negative black lead to the round pad marked Make a strain relief for the battery cable with the supplied cable tie as shown in the photo below 17 Fit U1 programmed PIC16F648A in its socket Ensure it is fitted the correct way round The pins may need teasing inward as they are supplied splayed outwards Ty UP one Lec L y U a VV oy C mq Qt R5 9 RE TU IH Wits uat T 1 i 0 lt 0 Assembled PCB before LCD is fitted J2 has already been fitted in this photo which is the next step Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 23 of 41 Step 6 LCD Display Assembly The LCD display is fitted above some other components on the PCB a
25. ing screws Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 17 of 41 Mechanical Components The mechanical components bag contains the following parts Mounting screws for PCB to screw PCB to box base Display spacers x 4 Button standoffs x 2 These are the same part used in 2 different places LCD Display screws and nuts to screw the LCD display to the PCB Battery clip cable tie Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 18 of 41 Step 3 Preparing For PCB Assembly First read through the rest of the assembly instructions The build is not difficult and should be easily completed in a day Before starting PCB assembly ensure you have the following 1 2 A large clear well lit working area Use daylight if possible A fine tipped soldering iron and some thin solder There are no SMD components but care must still be taken A multi meter If you spot a suspect solder joint or break a track test it and repair it if necessary before moving on Use a PCB assembly jig if you have one Follow these basic tips for a good result 1 Make sure your PCB is clean If you have had your kit for a while the plated areas of the PCB may have started to tarnish This will make it harder to solder A simple way to remove the tarnish is to rub the board with a standard pencil eraser Use only as much solder as necessary particularly with the s
26. ll be black At the other extreme the text will be very faint The optimum contrast is the point at which the background just disappears so you can read the text but the background is not visible Next do some basic checks to get confidence that the unit is basically ok e Switch on the meter You should see a sign on message showing the software version followed by Calibrating on the LCD display After a couple of seconds the calibration procedure should be complete and the meter should be in C mode e he meter should read zero pF The reading will be changing slightly with time Bridging the component connector with your finger should cause the reading to go up Measuring a known value capacitor should give the expected result e Press SW1 again The meter should switch to L mode You may hear relay K2 clicking in and out when switching between C and L modes Measuring a known value inductor should give the expected result e Next test SW2 Measure a component then press SW2 The reading should go to zero Take the component away and the reading should go negative by the same amount For example if you measure a 100pF capacitor the reading should say 100pF After pressing SW2 the reading should be OpF When the capacitor is removed the reading should be 100pF e f you leave the meter for 2 minutes it should switch off automatically Alternatively holding down SW1 will also turn off the meter f your met
27. maller parts Assemble the smallest components first working up to the larger parts the assembly instructions keep to this order When soldering large metal parts turn up the iron temperature if possible and use a large bit then use molten solder to spread the heat more evenly Oh and remember not to touch the hot component for quite a while Observe anti static precautions Most importantly take your time Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 19 of 41 Step 4 Component Connector Assembly Before putting the regular components on the PCB you must first make and solder on the component connector This is the hardest part of the build and shouldn t be rushed 1 Take the brass bar and saw it in half with a hacksaw you will end up with 2 pieces each of which is approximately 25 30mm in length Cut file one end of each piece diagonally at 45 until they are 23 5mm long on the long side as shown below A 23 5 mm PO 4 Polish the brass bars to make them easier to solder The best thing to use is a polishing block such as Maplin part number HX04E shown to the right Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Page 20 of 41 Do Not Solder This Side 4 It is very important to solder the brass bars in exactly the right position on the board In the photo above the gap between the t
28. many designs on the internet this meter has completely new software and a unique connector for higher accuracy Auto calibration auto zeroing and auto ranging make this design simple and reliable The major parts of the L C Meter are shown below A a o Sk 4 E U v a On Off and Zero L C Select Button Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Page 4 of 41 Power On Off To turn on the meter press the L C button once The LCD display will show a sign on message with the software version followed by Calibrating During the calibration procedure do not touch or place any components on the component connector The meter starts up in capacitance measuring mode To turn off the meter hold down the L C button for 2 seconds When the display goes blank release the button If the meter is not used for 2 minutes it will turn off automatically to preserve the battery Basic Operation Basic operation is simplicity itself The L C button switches between inductance L measuring mode and capacitance C measuring mode The selected mode is indicated by an L or C at the left hand end of the display With no component connected in C mode OpF is indicated and in L mode is indicated The zero button zeros the display The component connector is designed to accommodate a wide range of different sized components Small surface mount devices can be pushed up to the point of the connector
29. n How It Works This section describes the circuit operation to help with troubleshooting and for general interest Appendix A shows the full schematic circuit diagram of the L C meter Power Supply Section 1N4007 BC327 78L05 5 M E IN OUT P Vcc B 3 GND ENS El EA 7 C7 C8 C9 b 10uF e 100uF 100nF 100nF 100nF GND MV GND R4 10K D4 1N4148 D5 1N4148 LC BUTT R2 10K IV POWER HOLD od SWI I C The unit is powered from a 9V battery which is connected to J3 D1 protects the circuit from an accidentally reversed battery Power is switched on and off by pressing SW1 the L C button This works as follows Initially R3 ensures Q2 is turned off and no power flows to U2 As a result there is no power on the microprocessor parts of the circuit ensuring that the signal POWER HOLD is low and Q1 is consequently in the off state D5 prevents current flowing to the microprocessor via R3 R4 D4 This ensures a negligible current drain when the meter is off less than 1uA to prevent battery drain D5 also prevents any part of the microprocessor internals drawing enough current to turn on Q2 while the microprocessor is powered down When the user presses SW1 Q2 is turned on via D4 and R4 Power flows to the 5V regulator U2 and 5V appears on the VCC line The microprocessor starts up and the software sets the POWER HOLD line high This turns on Q1 ensuring that Q2 is held in the on state after the user releases SWI T
30. nd is connected by J2 which is soldered at both ends Once fitted it is difficult to remove the LCD to get access to any components below Before fitting the LCD display inspect the area beneath the LCD for solder splashes and check that the correct value components are fitted and diodes are the correct way round To fit the LCD display 1 First fit J2 the display connector to the PCB This is a 14 pin connector which is soldered at both ends At the LCD display end there are 16 holes the connector goes in holes 1 14 Holes 15 16 are not used It should be impossible to get the connector in the wrong holes because mechanically it won t fit any other way when the display mounting screws are in place Put the 4 mounting screws through the holes at the corners of the LCD display and turn the display upside down so the screws stay in place Slide a spacer on to each of the 4 mounting screws Turn the PCB over and carefully place it on the upturned display making sure the connector goes through holes 1 14 Put a nut on each of the mounting screws and tighten The spacers are a loose fit on the screws and you must ensure the spacers are pushed inboard away from the PCB edge when the screws are tightened or they will foul the battery compartment and end panel and the PCB will not fit in the box see arrows below The screws don t have to be very tight you will squeeze down the nylon spacer with excessive force 9 o Q OF
31. ons or other impure capacitance will give erroneous readings This may happen with old components that have degraded or become leaky Most modern commercial components give reliable readings but you may be surprised how inaccurate they can be some capacitors have tolerances specifications like 80 20 which means they can be almost twice their nominal value With a purely capacitive component the accuracy of the reading is about 1 except for values at the extreme ends of the range e g lt 10pF WARNING Ensure that capacitors are fully discharged before trying to measure them Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 5 of 41 Measuring Inductance To measure an inductor a coil first switch to inductance mode press the L C button until you see L on the left of the display With no component connected the display should read Next connect your inductor to the component connector taking care not to touch the leads The value will be shown on the display The range is automatically chosen and the value is displayed in the appropriate units If the component is on the borderline between two ranges the meter may switch ranges as you move the component in the connector but built in hysteresis ensures the meter will not hunt between ranges Inductors with a low Q do not resonate well in an LC circuit and will not give a reliable reading with this meter Coils in packages such as the T
32. ot be identical to the photos and may have different voltage ratings as components from different manufacturers can look slightly different Markings Identification C1 10uF 10uF black in colour Ss short amp stubby Take care not to mix up with C4 We Markings Identification C2 100uF 100uF black in colour short amp stubby arkings Identification 2 2uF black in colour Markings Identification SN C4 10uF 10uF brown in colour low ESR Take care not to mix up a o with C1 Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 11 of 41 Markings Identification Cb J680pF 681J red in colour Markings Identification C6 1nF 196 1n0 on top edge blue in colour Markings Identification C7 C9 100nF 104 blue in colour Markings Identification C10 amp C11 22pF 22J orange in colour Take care not to mix up with C12 Markings Identification C12 5pF 5C orange in colour Take care not to mix up with C10 C11 Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 12 of 41 Inductor There is only one inductor It looks like a fat resistor and has the same coloured bands Diodes You should have five diodes two different types The diodes are marked with the part number around their body The striped end is the cathode D1 D3 1N4007 D4 amp D5 1N4148 Transistors There are two transistors They look very simil
33. ovations Ltd 2009 L C Meter User Guide Page 33 of 41 In L mode we use this formula for finding the component value 2 2 L FE 1 x Ho 1 iun p Fi Coal 27F Notice how the value of L1 isn t in either formula Notice also how the value of C5 isn t in either formula The only capacitor that features is the calibration capacitor C6 which is why we use a 1 tolerance type Now we have to consider the effect of stray capacitance and inductance on our results especially on small value components In C mode the method we use automatically removes the effect of stray capacitance because the absolute value of C is unimportant When we measure F the stray capacitance affects the value of C5 but C5 doesn t feature in our equations During calibration C6 is added to the circuit but C5 and Cgtray are still in circuit so the change is just the value of C6 In L mode when we change the configuration of the circuit the stray capacitance changes In C mode L1 is connected to GND The stray capacitance of the component connector and tracks are in parallel with the LC circuit i e they simply add to the C However when we are in L mode L1 is connected to the component connector which is shorted with the inductor under test This effectively isolates the stray capacitance of the component connector and its tracks The frequencies we measure during calibration are not the same as the values we get in this configuration the frequency with a zero nH short
34. play From the c side you will be able to see the bezel template stay slightly outside the bezel s inner edge so the hole is larger than required layer a will cover up the cut edge when finally assembled Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Page 28 of 41 5 Place layer a shiny side down on a flat surface i e the text will be mirror image It is important not to get any marks on the panel and not to transfer any surface lumps when it is pressed so put it on a pad of paper or something similar 6 Peel the backing off layer b and carefully stick it down on the printed rough side of layer a lining up the display window as closely as possible The hole in layer b and c will be larger than the black bezel printing on layer a so it is straightforward to line up the pieces When turned over the cut edge of the hole on layers b and c should be covered by the printing on layer a 7 Using something made from smooth hard plastic e g a screwdriver handle carefully rub over the whole of the shiny side of the label as you work the surface all the tiny glue bubbles will disappear Be careful the label stays flat and doesn t buckle while rubbing 8 With scissors cut the whole label to a rough rectangle slightly bigger than the recess in the top of the box Don t attempt to cut the curved sides at this point just cut them straight across but larger than the widest point
35. rcuit Fcal should be between 55 and 70 of Fosc Error messages are displayed for 20 seconds or until you press the L C button upon which the unit turns off Replacing The Battery The unit is powered from a 9V PP3 battery It is accessed through a slide out panel on the back of the box Simply open the panel pull the battery out and unclip the battery clip then replace with a new battery Battery life is very good as power consumption is low and the unit powers off automatically after 2 minutes of inactivity Issue 3 Copyright O Debug Innovations Ltd 2009 L C Meter User Guide Page 7 of 41 LC Meter V1 2 Kit Assembly Instructions This section gives step by step instructions on assembling and testing the kit It is not a difficult kit to build except for soldering the component connector which is a little tricky but can be done even by a novice if the instructions are followed carefully Most people should be able to build the kit in under 5 hours Seasoned builders will only require 2 to 3 hours There are no surface mount components unless you count the component connector If you have any questions or are unsure about what is meant by anything please email support debuginnovations com and we will be pleased to assist you Step 1 Unpacking Your Kit Your kit should come in a sealed package as shown below These instructions are for PCB V1 2 Please check that your kit label says PCB V1 2 L C Meter Kit PCB
36. ver part numbers are listed in order of preference usually because of price Part numbers are prefixed by supplier as follows Supplier Website Digi Key UK http dkc1 digikey com uk digihome html Mouser Electronics http uk mouser com Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 37 of 41 Appendix C1 PCB V1 2 Unassembled Jl o 09 O qgoo00090000 o O Q 2 00 a 9 0 00 9 a 9 o o N O O o MO CATU o0 6 000090000 O Q fo Mo Wo Ho No Mo No Ho e gt 009000000000000 O Solder Side Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Appendix C2 PCB V1 2 Assembled C2 n U2 C8 O 19 wa QU MEA Be LCD AZ 4 SEA 1 38 MA 1 W EE lt Heo Iie Hike gt The _ C n Sia E og AE X MAN SG m y Mg aes E US With LCD Display Issue 3 Copyright O Debug Innovations Ltd 2009 Page 38 of 41 L C Meter User Guide Page 39 of 41 Appendix D PCB V1 2 Copper Pattern not to scale Component Side 9101010 r ee JO Solder Side LC Meter V1 2 Copyright Debug Innovations Ltd 2009 Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 40 of 41 Appendix E Box Top Drill Drawing 100 83 8 Not to scale for guidance only All dimensions in mm Outer rectangle is label recess representing widest dimension on curved ed
37. wo bars inside the red circle should be as small as possible without touching As a guideline it should be possible to get a piece of paper in the gap but not a small wire The bars should be positioned close to the edges of the copper tracks marked by red arrows This edge will not be soldered the bars are held down by solder on the other side 5 To solder the bars use the wooden peg supplied to hold the bar in place First put the peg in the middle of a bar adjust the bar until it is in the correct position then solder the ends of the bar being careful not to move the bar You will need a hot soldering iron and a little patience as the bar and copper pattern have a high heat capacity Once the ends are soldered you can move the peg to one end and solder fillet the whole length of the bar Take your time soldering the component connector this is the hardest part of the build and the only part of the PCB that is visible when finished Issue 3 Copyright Debug Innovations Ltd 2009 L C Meter User Guide Page 21 of 41 Step 5 Component Assembly 0600000090 e R2 2 e Je 606060000 u hi uiis t cn GU 0 Uo Ay ay Turn the board so it looks like the diagram above and fit the parts in the following order The parts list is shown in Appendix B1 A fully assembled PCB is shown in Appendix C2 1 10 Issue 3 Fit all the resistors R1 to R11 being careful not to mix up the different values If in doubt
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