[time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)

Mark Sims 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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