Re: Re: question on LED clock operation

On Tue, 12 Dec 2006 10:00:01 +0000, me@xxxxxxxxxxx wrote:

As for much cheaper, I don't think so - at this point a quartz oscillator
circuit costs only pennies. Anything battery powered will have one

Anything with a digital display will have one.

I think that the correct statement will be "Anything with a digital
display will have a clock signal". But this clock signal does not need to be
generated by a crystal oscillator.

I have dismantled in the past some of these LED clocks and, in my
experience, they use to use the 50/60 Hz mains frequency as the clock signal
of the digital circuitry (this 50/60 Hz even controls the LED display
multiplexing). When the mains is offline an RC oscillator is turned on to
generate the timebase. I have sometimes trimmed this RC oscillator trying to
fix the big gains or losses of these clocks when offline.

Regards.
.