[time-nuts] webcam app to watch for and time stamp changes
jimlux at earthlink.net
Sun Mar 3 09:46:12 EST 2013
On 3/3/13 1:00 AM, Poul-Henning Kamp wrote:
> Content-Type: text/plain; charset=ISO-8859-1
> In message <657D7F7CC03849419A2A90752E6A60A6 at pc52>, "Tom Van Baak" writes:
>> 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.
> Most LCD and LED clocks have a shielding metal-coating on the front
> glass, exactly to eliminate all EMI/EMC issues.
Yes, but perhaps there's enough leakage to make this work. After all,
the EMI requirement (assuming it's running at 32 kHz) isn't particularly
stringent and because the fob is small, the radiated field at any
distance is going to very small. OTOH, I can put a probe or coil right
on or around the fob.
I'll let you all know what I detect when I try it tomorrow.
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