24 February 2014

AD9850 board and temperature

My AD9850 DDS chip and the 125 MHz canned oscillator run pretty warm to the touch. No info were found online, so here you are my values in room temperature (23°C): both stabilise between 45 and 48 °C.

I let it run for few hours and it didn't break nor catch fire.

Chip temperature is not output-frequency dependant, but output-frequency depends on the oscillator temperature. Touch the canned oscillator and it will change of few Hz. I am wondering if I should add a small heatsink to the oscillator. Is it worth?!

18 February 2014

Arduino controlled AD9850 DDS signal generator

Been blog-silent for a while, but my AD9850 DDS is now complete. The Arduino (Nano) code evolved day-by-day while assembling the circuit. I re-assigned some pins to simplify wire routing and implemented an easily extensible menu. My code is based on AD7C work and it is available on request.

I have added a scan function with user settable lower/upper frequency limits.

I have added a menu driven with a resistive potentiometer, which requires only one button for confirming the action and theoretically can host dozens of functions. While it is not an innovative idea, it is very comfortable to use as long as there are 5-to-10 total choices.

I am now using a TWI/I2C interface to the display, which uses 4 instead of 8 total wires.

DC is provided with a step-down regulator. I will add DC filtering capacitors near the Arduino and DDS boards.

That's two knobs and one display that now require a suitable housing.