[time-nuts] Re: Small PCB for measuring zero crossings of AC power (possible group buy?)

[Tom Van Baak]

Jeremy,

You'll have fun with that project. Thanks for sharing.

I use a simple 5 or 12 VAC wall-wart and 10 k resistor directly to a MCU 
GPIO pin. The combo of PIC Schmitt trigger input & protection diodes 
plus picPET timestamping does the job without any other components. I 
capture 60 timestamps per second, and summarize or decimate on the PC 
doing the logging. I suspect your PCB would give better results for tau 
0.01 to tau 1 but beyond that perhaps not much. Let me know if you have 
some sample data to confirm that hunch.

Short-term and long-term ADEV of mains:

http://leapsecond.com/pages/mains/mains-adev-mdev-gnuplot-g4.png

A mains example from a picPET:

 Â Â Â  http://leapsecond.com/pic/pp06.htm

A cross-country Western grid synchronization experiment -- similar to your:

 Â Â Â  http://www.leapsecond.com/pages/mains-cv/

Cheapest zero-crossing detector (YMMV):

 Â Â Â  http://leapsecond.com/pages/ac-detect/

A time-lapse cesium & webcam method to monitor and visualize mains wall 
clock time drift:

 Â Â Â  http://leapsecond.com/pages/tec/mains-clock-ani.gif

/tvb


On 5/12/2023 1:17 AM, Jeremy Elson via time-nuts wrote:
> Greetings,
>
> Recently I've been interested in doing long-term measurements of the mains
> power frequency (e.g.,
>