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

Magnus Danielson magnus at rubidium.dyndns.org
Sat Mar 2 19:50:07 EST 2013

On 03/03/2013 01:39 AM, Jim Lux wrote:
> 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...

Thanks. It's physics applied, knowing the basics and work from there.

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

Most probably. You would probably enjoy having a JFET amplifier in there.


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