Tiny DDS – Open source DDS generator




Description

The homemade function generator is a quite common project on the internet. We can find different ways to do it:

– The quick & dirty way based on a DDS module bought on eBay
– The analog version based on a MAX038 / XR2206
– The “clean” way based on a FPGA and a fast DAC (e.g. http://www.circuitben.net/node/14)
– The software way (e.g. Arduino + R/2R DAC)

From my side, I wanted a small one which could fits my needs without being too expensive. According to me, such generator should at least:

Tiny DDS – Open source DDS generator




– Be easy to use
– Output a signal from 1Vpp to 10Vpp (+/-5V), from 0 to 1MHz
– Have a low profile
– Without electric hazard (shall work on a 12V DC)

Choosing the DDS chip

I first started to look for a cheap DDS chip on eBay; you have to be careful because most of DDS chips have only a sinusoidal output. Since I also want a triangular output, I have chosen the AD9834. According to its datasheet, this component is able to output a frequency of 37.5MHz from a clock of 75MHz… But do not expect a clean waveform at such frequency: without an internal PLL, this signal would be defined by only 2 points.

From my personal experience, I consider that a waveform shall be defined by 10-20 points to be well restituted. Relying on a 75MHz clock, the maximal output frequency would be 7.5MHz… This is not a very good performance for a professional equipment (even if the cheapest generators do not go above 4MHz), but it is quite reasonable for a hobbyist project.

The AD9834 can be found at $5 on eBay.

 

For more detail: Tiny DDS – Open source DDS generator




Leave a Comment

*
= 3 + 9

Read previous post:
Large Current Relay Driver
Large Current Relay Driver

This is a large current Relay module with single pole double throw switch which provides normally closed and normally open...

Close
Scroll to top