Assembly & User Manual - Midnight Design Solutions
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1. a modular way to add stable DDS based signal generation to your next transceiver or VFO project How many ways can you use a Self contained high precision dc 60 MHz signal source contained on a 1 x 2 plug in circuit board How about as a stand alone VFO a signal generator for your bench a replacement LO for your Sierra or NC40 transceiver or perhaps as the heart of an antenna analyzer Control it with your favorite microcontroller or even hang it off the parallel port of your Any way you do it you ll be generating quality signals for less than 50 Ces 50 11 g 09851 U2 irs 0534 733256 1 id ve Ye Ve we DDS 60 Front Sid 005 60 Bottom Side NOTES R19 and C5 happen to be installed in reversed positions NOTES R7 and C4 positions are empty These components are on the board in this photo The circuit is electrically equivalent unused and are not provided in the kit R16 and the IC shown on the right are no longer provided in the kit Direct Digital Synthesis DDS captures the experimenter s imagination and excites like no other technology these days Exceptional signal precision accuracy stability programmability and signal quality are all easily and inexpensively achieved But two quite formidable problems still remain The first problem is that these surface mount DDS chips are so tiny with lead pitches as fine as 0 65 mm that it is nearly i2. JO 5 mace Ame 740 se jdeoxy 8106060 06 gi 001 o m 15 ST ST zty 91 51 9079 yo 2 o oy Fo rs yeubys 09 0 FO E Td vivd 0 ely GND ui A S 2005 2014 Midnight Design Solutions All rights reserved DDS 60 Assembly and User Manual v1 4 DDS 60 Daughtercard Parts List QTY Designator Description 712 7777 560 1265 00 1 8 7 500 540 2 Resistor 5 6K SMT 1206 R11 R19 Resistor 24 1206 SMD R13 R14 R15 Resistor 10K 1206 SMT integrated circuit 08008 DDS integrated circuit 28 pin SSOP Integrated circuit 5V voltage reg SOT 223 Oscillator 30 MHz SMT Pin Header 0 17 8 PC Board Assembly Steps 1 Need help assembling all these small components See the comments in the Notes section about Kit Builders Attach all SMT integrated circuits For each location tin pad 1 carefully position the IC observing orientation and solder pin 1 in place Solder the opposite corner pin while ensuring that all pins are over the respective pads Solder remaining pins to pads If needed remove excess solder with solder braid Solder the larger ground tab of U3 to the pad opposite the three smaller
3. 005 685 1 68 REF 18 8 ATT ds _ E_blank 1888 AUG A al START 18 MHz STOP 1 MHz DOS 66 5 1 66 8PRE REF 18 dEn _ _ AVG A 58 5 START MHz STOP i886 MHz 2005 2014 Midnight Design Solutions All rights reserved 005 6875 1 68 REF 188 dEn di A_norrn a EB_blank 18 98 AUG 5845 AUG A TIMES Le ET ee EE TL HI cm AIM La 288 ris START 18 MHz STOP MHz Controlling the DDS It won t be too long before you consider ways to use the DDS 60 Well you in for a real treat as there are a whole bunch of convenient and powerful techniques already developed that can be employed to provide a user interface and controller for this RF signal generator module In general the AD9851 DDS chip needs to be sent a control word by an external controller before the DDS 60 is capable of generating a signal No matter what controller you use it must serially send a 40 bit control word to the DDS 60 on the DATA line P1 pin 3 The controller clocks each bit into the DDS chip by the toggling the CLK control line P1 pin 2 To complete the sequence the accumulated control word is loaded into another internal DDS register by a toggling of the LOAD line P1 pin 1 thus instr
4. minimal hardware arrangement needed for dumb terminal like on a Windows PC or ProComm on a handheld computer to command the HC908 to generate frequencies in effect the HC908 and DDS daughtercards become a remotely controlled signal generator DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved Parallel port control from your You can even control the DDS Daughtercard directly from your PC All that s needed is to wire the daughtercard to the printer port cable and run one of several public domain custom software programs to have the PC serve as VFO controller The programs from KA2ZUPW or WA6UFW WA6FXT located on the project website each have an attractive display screen that offers specific frequency entry phase settings and even scanning controls DDS Daughtercard 3 Clock Load 18 Gad _ If you wire the DDS Daughtercard to the PC s parallel port connector and a power supply as shown in this diagram any signal from 0 1 Hz to 30 MHz may be generated by the software application running on the PC H TEKTAONDS 465M Here is shown the PC VFO assembly being controlled by a PC over its parallel printer port The DDS Daughtercard is housed in a rugged die cast aluminum enclosure with connectors for the parallel port control lines RF output on a BNC and power input on a coaxial power connector Switches provide power cont
5. pins Attach trimpot R8 by tinning one pad first then carefully hold the trim pot in place with tweezers and re heat the pad Solder the other two pads Measure about 250 ohms from wiper pad to either end pad to ensure successful connection Attach all SMT resistors Sequentially attach each value group to the board according to the order arranged on the SMT Card For each resistor location tin one pad hold resistor in place and reheat that pad to attach Solder other end to pad DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved Attach all SMT capacitors in the same manner as above Attach inductors L1 and L2 in the same manner as above Attach capacitor C8 silver can in same manner as above Side without black mark goes to pad 2 Attach oscillator U4 with notched end up See photo 10 Attach pinheader to the top of board see photo 11 Install jumpers at the a set of pads The b set of pads are for an option that is no longer offered Solder wire jumpers as shown red on the pads to select the trimpot to adjust 20 5 L1 edi U2 4 Initial Test amp Adjustment 1 Observe P1 connections and apply 8 12V dc power 2 Observe approx 5V p p clock waveform at U4 output 3 While driving DDS 60 card with appropriate controller generating 10 MHz waveform observe 200mV at DDS output and at R1 C1 inpu
6. that contains much useful kit information If you still have questions or need technical assistance after consulting this online resource contact George Heron N2APB n2apb midnightdesignsolutions com or Joe Everhart N2CX n2cx verizon net 2 DDS 60 Kit may be purchased from Midnight Design Solutions Refer to the DDS 60 project web page for all current technical and ordering details http www midnightdesignsolutions com dds60 3 Details of the NJQRP QuickieLab project be found at www nijgrp org quickielab 4 Details of the HC908 Daughtercard project can be found at http midnightdesignsolutions com HC908VFO DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved
7. 60 card is plug compatible on the PIC EL hardware DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved QuickieLab The 005 60 is ready made for plugging into the NJQRP QuickieLab which is an experimenter s platform provided several years ago in kit for hobbyists to easily build up circuits on a plugboard and connect them into various standard circuits provided on the board for audio amplification A D conversion and LCD display So all you need to do is plug the DDS 60 into the appropriate socket on the QuickieLab and use some of the canned software that s provided to have the hardware serve as a basic VFO The programming sequence 15 easily accomplished In one of his renowned Joe s Quickies columns in QRP Quarterly magazine N2CX uses the following three lines to instruct the BASIC Stamp controller to produce a 7 040 MHz signal with the DDS 60 plugged into the QuickieLab shiftout 7 8 0 8F 2F 03 0A 01 out9 1 out9 0 The first instruction line shifts out the 40 bit 5 byte value on port P7 using P8 as the clock The Mode we use for the shiftout command is 0 meaning that the LSB gets shifted out first for each data byte listed parentheses starting with the first byte listed 8F and ending with the last byte 01 This is the bit programming order specified for the AD9850 and AD9851 serial mode The second and third instruction lines toggle the LOAD pin go
8. dance measurements in the Micro908 Antenna Analyst and other demanding applications A trimpot allows precise manual control of the desired output level The design provides a good signal using supply voltages from 12V all the way down to 8V thus conveniently allowing for battery operation The amplified signal is then available for use as a 50 ohm source input signal If not used as an input to any other component or module the output should be terminated with a 50 ohm load for the stated specifications to be realized Specifications Power requirements 8 12V DC at 120 ma typ RF Output fully adjustable up to 15 dBm about 3V pp Output signal unaffected by varying V supply voltage great for battery operation Near constant output level from 1 60 MHz Good signal purity harmonics down approximately 40 dB from the fundamental VVVVV DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved abeyoed LNS ZHIN 06 51 payddns 20121050 dig pessu gpn 20128250 LNS JO sused Sulg PNO Ri po 9 2 ON Iu tee HN SI 0 gt 4 000 1 9 ul 590065169 2 140 spesejooid syayjo 4
9. de is probably correct Even my guitar calloused fingers cannot be pressed on either of these chips for longer than 10 seconds without a severe Ouch But this is normal and okay as long as the ambient temperature stays below 195 degF yes an almost boiling room temperature will exceed the max Tj of these components The packages are made for this our fingers are not 3 If you want to reduce the operating temperature of the voltage regulator U3 try supplying the DDS card with a lower voltage The card is designed to operate with a voltage source as low as 8V Using this level of power supply will significantly lower the operating temperature of the regulator PS Voltage current and temperature measurements were made with a Metex ME 11 DVM with a Fluke 80T 150U temperature probe DDS Signal Quality Jim Kortge K8IQY performed some signal quality measurements using his lab quality soectrum analyzer and he captured the screen views for us Jim writes Guys thought you might like to have the latest plots at 10 30 and 60 MHz using the latest PIC EL 5 1 code and my 005 60 also just a test to make sure that the manual gain pot could be used to adjust the 60 MHz amplitude to that of the 10 MHz signal Works like a dream think this DDS 60 board is a true winner and works very well DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved DDS 60 Assembly and User Manual v1 4
10. g conducted in the online PIC Elmer 160 course The course material is geared around use of common I O components pushbuttons LEDs LCD display rotary encoder and speaker It has a built in serial programmer that allows the user to download new programs directly from the PC and burn them into the PIC microcontroller and we provide an ability for the user to plug in the inexpensive and ubiquitous DDS 60 card that produces signals up to 60 MHz A rotary encoder dial allows one to use the PIC EL as a stable signal general a super precise VFO or perhaps even as a signal source for receiver calibration BNC connector 15 also provided in the kit to help enable these common uses The PIC EL can measure the frequency of an input signal presented on the BNC connector Stereo 1 8 jacks allow you to plug in your iambic paddles and have the project board serve as a keyer with adjustable speed weighting and multiple memory buffers The onboard speaker serves as a side tone and you can connect the output signal to your rig by cabling from the other 1 8 jack and you ll be able to key your rig with the PIC EL project board bes 82 fe ____ __ peng 7 1 SHES ber Li J e 1 fe DDS card plugged into the PIC EL project board The DDS card shown here is the original DDS 30 Daughtercard the new DDS
11. ing to the DDS at which point the RF signal is generated at the output of the DDS 60 If you do use the DDS Daughtercard with the NJQRP QuickieLab remember to cut the 5V trace on the bottom of the QuickieLab pc board that leads to P1 pin 4 on the DDS 60 socket This is because the DDS 60 produces its own internal 5V supply and doesn t require the QuickieLab to supply it aa 3 D 1 ar 77 77 0099 Je Here s the QuickieLab set with the DDS Daughtercard the previous version DDS 30 is shown in the socket located just above the white plugboard The BASIC Stamp processor located on the main board beneath the LCD commands the DDS chip on the daughtercard in order to generate RF signals that are pumped out the BNC connector on the right side of the board DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved Closeup of the DDS Daughtercard plugged into the Note that DDS card used here is one of the original ones that used the MMIC amplifier on the right side of the card The MMIC amplifier has been replaced by the addition of the AD8008 in the current DDS 60 design DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved Butterfly Controller Board Software currently exists for the AVR Butterfly card to present a sim
12. le looking for the voltage 5 If you do not see a signal there on Uta pin 1 then the problem is farther back toward the DDS But if you do see a Signal the problem is somewhere between the two amplifiers Ula and Uib Carefully look for wrong components placed improperly soldered components missing broken components 6 Next look for a 200 mV p p signal 0 07 Vdc on your RF Probe DVM at the output of the Low Pass Filter The output of the LPF is on the through hole pad below the right end of C1 If you see the signal there the problem is probably in the first amplifier stage U1a Again check components etc as previously instructed 7 Next look for the raw DDS output signal also 200 mV p p at the top of R12 If you do not see a signal there then the DDS is not DDS ing 8 Next check to see that your reference clock is producing the required 30 MHz signal to the DDS chip Probe the larger through hole pad to the left of C19 and expect to see a whopping signal of about 4 Vp or 1 4 with your RF probe and DVM If not seen your reference clock isn t attached properly or it is defective either of which would inhibit your DDS card from working Temperature Analysis some builders of the DDS 60 card are surprised at how hot the components operate particularly the DDS chip U2 and the 5V voltage regulator device U3 In quick summary these components will indeed get pretty warm in fact too warm to hold your fi
13. mpossible to homebrew with them using conventional techniques It is quite difficult to tack solder a fine wire onto one of these small SOIC package leads let alone putting 16 wires to the chip The second problem is that these DDS chips must be interfaced to a microcontroller that provides that frequency programmability A 40 bit control word must be loaded into the DDS chip to command it to generate a specific frequency There are many projects around that control a DDS chip with a PIC an Atmel controller a BASIC Stamp an SX chip and so on don t know about you but the VFO will ultimately need is likely to use some controller that don t technically know and cannot program This makes it tough to use that controller for anything but commanding the DDS thus raising the cost of the entire project increasing the amount of board real estate needed and raising the power needs for the entire project The Solution get past these two problems we designed the DDS 60 a self contained functional module that generates a top notch RF signal by using a small pc board to contain just the bare DDS essentials an Analog Devices AD9851 DDS chip a clock oscillator a 5th_order elliptic filter and an adjustable level RF amplifier Additionally an onboard 5V regulator is provided so you only need provide a single 12V battery or power supply ranging anywhere from 8 12V DC The three digital control lines the power supply and the
14. nger it for more than 5 10 seconds but this is quite normal and here is how we determine that DDS 60 card Input 13 4 volts 128 ma Don t forget there s a diode between the power connector amp card amounting to a 0 2 volt drop This current is for fully operating DDS chip with PLL turned on effectively creating a 180 MHz ref clock Regulator Input 13 4 volts Output 5 volts 97 ma Tj max 150 degC Theta JA 53 degC AD9851 Power 650 mW worst case from spec sheet 180 MHz 5V Tj max 150 degC Theta JA 82 degC Ambient Temp 21 1 degC Theta JA Thermal resistance from junction to ambient DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved The all important equation for Tj temp of internal semiconductor junction Tj Tambient PWR x Theta JA So for the REGULATOR Tj 21 1 13 4 5 x 097 x 53 64 3 degC therefore compared to Tj max of 150 we are well within spec And for the 09851 Tj 21 1 650 x 82 74 4 degC therefore again compared to Tj max of 150 we are well within spec Temperature Measurements Tambient 21 1 degC 70 degF Regulator case 71 1 degC 160 degF Regulator heatsink tab 76 6 degC 170 degF AD9851 case 63 9 degC 147 degF Conclusions 1 The DDS 60 is operating within component thermal and power specifications 2 The too hot to touch observation that some have ma
15. output signal are all available on a pin header at the board edge This 8 position pin header serves to allow the DDS 60 to be plugged into and used in many projects on your bench regardless of which microcontroller is employed Just provide a single strip socket e g a 16 IC socket split lengthwise on the project board and plug the DDS 60 A cable connected to the parallel printer port of your can even be used in conjunction with public domain DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved PC software to control the 005 60 See the Controller section in the full manual for number of custom solutions illustrating easy control of the DDS 60 Once your controller of choice serially loads the control word into the DDS the raw waveform is generated and presented to an elliptic filter that removes unwanted high end frequency components resulting in a signal of sufficient quality to serve as a local oscillator for a transceiver We regularly see great signal quality with harmonic content typically more than 40 dB below the fundamental The signal generated by the DDS 15 quite small so we use an AD8008 low power amplifier to provide about 18 dB of gain to boost the signal to about 2V to 3Vpp which is quite usable in a variety of applications This amplifier chip offers unconditional stability k gt 1 and yields spectrally clean signals It is an ideal signal source for making impe
16. ple user interface for frequency entry and display and to command the DDS Daughtercard to generate those frequencies See http www atmel com dyn products tools card asp tool id 3146 for more information on the Butterfly controller card Steve Weber KD1JV developed the DDS card driver software and has it on his website located at http www qgsl net kd1jv bfydds H TM AVR Butterfly AMEL 322222 The Butterfly controller card from Atmel is a convenient and inexpensive way to get a fairly powerful processor on card with some universal I O of an LCD and joystick pushbutton being used to navigate gt gt 47 _ 1 z 11 TA y cum celi 2 gt 4 5 m 7 A pee OP S amp S gt 2 7 is pictured the DDS Daughtercard plugged into ERCOS Butterfly Carrier board which allows the Atmel processor to control circuits interfaced to the Butterfly board The additional circuit card on the right is an earlier version of the SoftRock40 SDR receiver project described elsewhere in this issue of Homebrewer In this application the Butterfly controller board controls the DDS Daughtercard to generate RF being used as the local oscillator for the little receiver card The ERCOS Carrier Kit can be found at http www ecrostech com Products Butterfly Int
17. ro htm DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved Micro908 The DDS Daughtercard is already incorporated into the Micro908 kit from the AmQRP Club is integrally used to make the instrument function as an antenna analyzer So if you are able to write a specific VFO program for the Micro908 or perhaps just use the VFO function provided with the AA 908 software load on the Micro908 you can use the instrument to generate signals right out of the box 73 The DDS Daughtercard identified by the white circle in the photo above Is controlled by the HC908 Daughtercard on the Micro908 motherboard It plugs into an 8 pin right angle connector that holds the DDS card up off the motherboard above the reflectometer circuits of the Micro908 DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved HC908 Daughtercard You may also plug the daughtercard into the HC908 Excerciser board described in the Digital QRP Breadboard project and use the software provided with that project to have it serve as a programmable VFO The HC908 Daughtercard controller is a popular and recurring component with the DDS Daughtercard Together they make a flexible combination of modules that can be used in many different applications using a common set of software libraries Subroutines The configuration of the two modules shown in the right photo is the
18. rol and the ability to switch a 50 ohm load resistor in out of the circuit The oscilloscope display in the background shows the nice and clean 10 MHz signal currently being generated by the DDS card as commanded from the PC screen DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved Custom Controller Of course you can also design the DDS Daughtercard into your own custom project using your favorite microcontroller chip as the brains be it PIC Atmel Ubicom or 8051 derivative processor The possibilities are limitless This photo shows the DDS Daughtercard included in a circuit call the Exerciser It is a test fixture that all HC908 Daughtercards get plugged into for test and programming with the appropriate software before shipping The Exerciser schematic and software program are located in the HC908 Daughtercard manual DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved Conclusion This simple DDS Daughtercard solves both of the problems described at the beginning of this article It enables the homebrewer to easily take advantage of the positive attributes of the DDS chip to produce a high quality homebrew variable frequency signal source Let us know how you end up using your DDS card NOTES 1 Technical Support We maintain a Builders Notes page on the main DDS 60 web page http www midnighidesignsolutions com dds60
19. t to RF amp 4 Adjust R8 to obtain approx 2V to 3V pp at RF Out Troubleshooting Here are some checks you might try if you think your DDS 60 card is not functioning 1 You should ideally have a 2V p p RF signal at the output of the board when driving a 50 ohm load The signal can be adjust from near zero all the way up to over 3V p p the default initial mid position DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved trimpot setting will yield about 2V as seen on an oscilloscope or using RF probe on your DVM this will be somewhere between 0 7 Vdc and 0 4 Vdc RMS depending on the frequency of the sine wave the type of RF probe you have and the input impedance of your DVM to which the RF probe is attached 2 Carefully turn the trimpot throughout its range while looking for the signal If you do not see a signal there on P1p6 then your DDS 60 card is not generating a signal 3 Probe backwards through the circuit to see where you do see the signal You should have that same signal level 0 4 to 0 7 RMS at the output of U1b pin 7 If you do the problem is between there and the board output 4 If you do not check the next amp output back in the chain pin 1 You should expect to see about half of what the expected board output was about 0 9V or 0 3V DC with your RF probe again depending on the RF probe and DVM used And again carefully turn the trimpot whi
20. ucting the DDS chip to generate the frequency just loaded Then bingo the new frequency appears at the RF Output of the DDS 60 card 1 6 The AD9851 data sheet and an Interactive Design Tool applet on the Analog Devices website htto www analog com Analog Root static techSupport design Tl ools interactive ools dds ad9851 provide all the details on how to construct the five byte 40 bit control word with your microcontroller of choice Just select 5V operation enter 30 MHz in the reference clock field select the 6x multiplier and the desired operating frequency The applet will display the five control bytes that you need to send serially to the DDS 60 in order for it to generate that frequency There are many software programs available that already accomplish sending the control words to the DDS card thus enabling it to serve as a general purpose VFO Any of the techniques outlined in the next section may be adopted if you plan on using the specific processors in your project They are also great examples on which you can model a software program using a different microcontroller Here are some great ways for you to build up a project using the DDS 60 card to generate AF and RF signals DDS 60 Assembly and User Manual v1 4 2005 2014 Midnight Design Solutions All rights reserved PIC EL The PIC EL is a multi function PIC16F84A based project board that serves as the basis for the instruction and experiments bein
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