[time-nuts] webcam app to watch for and time stamp changes

Tom Van Baak tvb at LeapSecond.com
Sun Mar 3 03:10:40 EST 2013

> Well, considering that actively "driving" a LCD segment involves passing 
> an AC field over it, in electrostatic drive, you could detect the 
> existence of AC or not on a segment, but you would have to "mask out" 
> that of other segments. On the other hand, you can expect a multiplexed 
> drive. An E-field detector as such would be able to pick up the shifts. 
> Wonders if the multiplexing is done by the same clock or a free-running 
> clock. If it is the same clock, just picking up the E-field from the 
> multiplex suffice to detect the clock ticking.


That is indeed a clever idea. I'm sure the AC drive is derived from the same clock so if Jim can see the LCD segment/backplane waveform he's got a handle on the clock.

When playing with watches a while ago I tried to pick up any 32 kHz signal but failed. Those with 1 Hz stepper motors were easy, but LED or LCD displays were too electro/magnetic/acoustic quiet for me to ever detect anything.

Do you have suggestions on what sort of "antenna" to use to pick up the LCD AC E-field? I'd expect the LCD drive current to be vanishing small.


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