AD9850 DDS VFO

DDS VFO based on AD9850
design by VU3CNS, modified by me with help of VU2AOR.

A DDS VFO based on the Article published in hamradioindia website by VU3CNS. (http://www.hamradio.in/circuits/dds.php).

The same circuit has been modified to be used with the AD9850 modules, available in ebay in very cheap rate, Rs450 in my case.(the rate was in 2013, when I purchased them)

I decided to build a fresh PCB artwork at first, but it could have take time, so directly went on making the PCB published in the DDS page by OM Niras. Latest PCB designs can be found here: (http://pcb.hamradio.in/).

Meanwhile VU2AOR, OM Sameer sir made the VFO working on a vero board and that put the green signal for us to go on with the design as it works fine with the module.
After etching and preparing the PCBs, there we made some modifications.
As we using the 4X4 matrix keypad instead of 4X3 in original design we have to connect the 4th column of keypad using a 1N4148 diode, you can see here in the schematic how we have connected the no 8 pin of Keypad.

Secondly, for modules having 125Mhz Oscillator, we must use 5Volt, however if you are using 100Mhz or less Oscillator, please use 3.3 volt only.
One of the interesting thing is that, the Rotary Encoder is not a popular part in local electronics component shops here in India, so we got a plan, we used some mechanical encoder from damaged computer mouse from scraps, dismantled  the encoder and used for our purpose. This does not have a switch so have to externally use a switch for step size change. However if Rotary encoder is available, you may use it.
For calibration use the same method described in the original project page.
The test results are on the path.....

 

The above two images depicting our PCB etched by me, and calibrated by  AOR, later I went to order some Professional PCBs with my design using layout editor. The PCB has arrived and cost Rs220 each for me. I tested one of PCBs with all components and 9850 module on board, it was accurate and takes less space instead of the PCB published on the original at hamradioindia. However I have omitted the 2nd PIC which can be added with a small PCB in future. I have also made the change in the design to plug and play the ebay module, 7805 Voltage regulator, Rotary Encoder and the 4X4 keypad. I am sharing my pcb design here for personal and non commercial use only. 

 The test photos will be posted shortly....... keep checking for update, you can contact me on gurudattabam@gmail.com for PCB file to etch your own PCB.


Update:

Those who have got the pcb file from me,  note that, there is a error in the pcb design. As per schematic the Pin-19 (W-CLK) of DDS should be connected to LCD's PIN-12, but I have connected it to Pin-13, so make note of it and rectify yourself.

Hi all,
Some problem found with power section. The Voltage regulator heats up fast. I tried to use 78L05 instead of 7805. I suggest you should not use that, it gets too hot. Stick to 7805 with a heat-sink until any solution is made.
regards
Guru