On 2/26/15 20:39, Charles Steinmetz wrote:
ben wrote:
I'm going to have to build one of these. Assume you have some sort of
circuit that converts low-voltage AC from a transformer secondary to
a pulse train, start a timer, and count x amount of pulses?
Here is a zero-cross detector designed for this purpose:
<http://www.ko4bb.com/manuals/download.php?file=02_GPS_Timing/Simple_AC_Mains_Zero_Crossing_Detector.pdf>
Most mains-nuts feed the ZCD pulse to the DCD line of a PC's RS232
port and use the computer to time-stamp the crossings and append them
to a file of such time stamps.
If we all did this, then I realize that we could identify the different
power grids. However, I wonder if there is any interesting variation
*within* a grid. As the electricity flows vary throughout the day, it
seems possible that the phase difference between two people on the same
grid would actually change (a bit).
Has anybody done this experiment?
Philip
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