Author: Dean Souleles, KK4DAS Revision: 1.0, 25-Jan-2020
The signal generator outputs a sine wave from DC to ~62 MHz using an Arduino Nano and Analog Devices AD9850 Direct Digital Synthesizer. A 10K linear taper potentiometer is used as a variable attenuator. The display is 16x2 I2C LCD. The control is a Rotary Digital Encoder with push button. Turn the encoder to change frequency Push the button to select the tuning increment.
There are various versions of this floating around the internet. This is my implementation
Download the Arduino DDS Library by Paul Darlinton, M0XPD and install using the Arduino IDE library manager.
https://github.com/m0xpd/DDS
http://m0xpd.blogspot.com/2014/03/dds-and-duedds-libraries.html
Create a folder called KK4DASSigGen and install the the source files there. The main sketch is KK4DASSigGen.ino. Open it in the
Arduino IDE. It should compile with no errors.
A schematic and Fritzing diagram are included for reference.
Arduino Nano
DDS Signal Generator Module - any one of the AD9850 boards should work. I used each of these at different times:
https://www.amazon.com/HiLetgo-AD9850-Generator-0-40MHz-Equipment/dp/B01J7XPWNU/
https://www.amazon.com/gp/product/B082143FD9
Data sheet: https://www.analog.com/media/en/technical-documentation/data-sheets/AD9850.pdf
16x2 I2C LCD display
https://www.amazon.com/JANSANE-Arduino-Display-Interface-Raspberry/dp/B07D83DY17
Rotary Encoder with switch
https://www.mouser.com/ProductDetail/652-PEC11R-4020F-S24
10K Linear Taper Potentiometer
https://www.mouser.com/ProductDetail/Bourns/PDB181-K415K-103B?qs=Zq5ylnUbLm7hRcKeZmRxRw%3D%3D
Enclosure - 4"x3" plastic enclosure
https://www.mpja.com/4in-X-3in-X-16in-Black-Plastic-Box-Enclosure/productinfo/15523+BX/
Panel mount BNC Connector
https://www.mpja.com/BNC-Type-Connector-UG-1094-Female-Single-Hole-Mount/productinfo/20507+RC/
PCBs = two Adafruit 1/4 sized breadboard PCBs, one for the Arduino and one for the AD-9850 module
https://www.adafruit.com/product/589
Mounting hardware - 4-40 standoffs and spacers, machine screws, washers and nuts
Optional - 0.1" female headers on the breadboard make it easy to wire the components up in the case
| AD9850 | Arduino |
|---|---|
| W_CLK | Pin 8 - connect to AD9850 module word load clock pin (CLK) |
| FQ_UD | Pin 9 - connect to freq update pin (FQ) |
| DATA | Pin 10 - connect to serial data load pin (DATA) |
| RESET | Pin 11 - connect to reset pin (RST) |
| VCC | +5 |
| Gnd | Gnd |
| Encoder | Arduino |
|---|---|
| A | 2 - Encoder pin A D2 (interrupt pin) |
| B | 3 - Encoder pin B D3 (interrupt pin) |
| BTN | A3 - Encoder push button |
| LCD/I2C | Arduino |
|---|---|
| SDA | 4 |
| SCL | 5 |
| VCC | +5 |
| Gnd | Gnd |
| Pot | Connects to |
|---|---|
| 1 | AD-9850 Sin B |
| 2 | Wiper goes to center pin of BNC |
| 3 | Gnd |