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

Jim Lux jimlux at earthlink.net
Sat Mar 2 19:39:31 EST 2013


On 3/2/13 4:12 PM, Magnus Danielson wrote:
> On 03/03/2013 01:00 AM, Peter Gottlieb wrote:
>> Perhaps you can detect EMI from the device especially if you put it it a
>> shielded metal box with pickup antenna. You might be able to get the
>> clock right from that.
>
> 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.
>

OH, ho.. this is clever.. Time to get the scope probe out.. Find the big 
peak, work out a quick and dirty analog filter, run it to the counter...


I would suspect that the multiplexing comes off the same oscillator, the 
whole thing probably runs off a 32 kHz clock crystal.


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