Monday, July 1, 2013

"e-Bay" DDS Oscillator

Sorry for the long delay...been working on other things lately.  Riding my bike, playing with my new FT817...

Now, I have started to get back into it again.  My newest challenge...running the PICAXE on 3.3V yet running the display at 5V.   Actually - that turned out to be less of a challenge than I feared.  It seems that the 5V LCD Display works just nicely with the 3.3V input as long as you current limit the interface, which I have done.

With that, I have constructed another AXE401 shield which is connected to an AD9850-based DDS oscillator which has proliferated on eBay for almost a year.  I bought 4 of them for $5 each - and the postage cost as much as the boards.  In spite of that, I still came out ahead.

The reason for the urgency of the 3.3V - the 125MHz reference oscillator is a 3.3V oscillator, so I had to turn down the voltage. 

It does work, though it is harmonic rich.  May have picked the wrong output...two are square-wave, one is unfiltered sine wave, and one is filtered sine wave. 

Better quality photos soon to be coming later.   Hoping to have this ready to show at the "Solder-something" meeting of Vienna Wireless Society on the 4th Friday of July.