[time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)
holrum at hotmail.com
Mon Mar 20 19:43:08 EDT 2017
The "DAC" was PWM based, but used a separate voltage regulator for the "reference". I never tried it using the USB power as the reference.
The OCXO (+board) uses less than 500 mA warming up (which it does rather quickly). It's in a small hermetic package about twice the size of a standard DIP-14 oscillator package. There was a Ebay seller several years ago offering them at $15 each or 10 for $100.
The Chinese "Arduino" board (it's not really and Arduino, just a MEGA 328 and a proto area) has a micro-USB connector for power input but does not implement USB data. I used the processor serial port with a level shifter dongle. The firmware was a cheap and dirty hack and I didn't implement much in the way of control or monitoring... never got around to improving it. The project was basically "Hey, I forgot I had those parts... Hmmm, one could build a simple GPSDO... why not?
> Did you use the Arduino's PWM output plus a LPF for the DAC, or a separate
DAC? If PWM, did you have problems with noise or sensitivity to the
USB-provided supply voltage?
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