On 1/25/2007 12:50:46 PM, Mark Amos ([EMAIL PROTECTED]) wrote:
> Time-nuts
>
> I appreciate the comments regarding horological obsession. Mine started
> with a desire for an accurate master
> oscillator for my ham shack (built and use a couple Shera
> GPSDO's) and has blossomed into a much broader interest
> in time (Ex tempus, sapientia?)
>
> This has led me to a silly quest. I'd
> like to use a traditional clock face and hands as an output device for a
> 1PPS signal from my GPSDO.
>
> I know this is a very broad question, but does anyone have advice on where
> I might start hacking (or making) a
> mechanical clock face to accomplish this? Is there a simple clock design
> that I could start with to build my own?
> Maybe replacing a pendulum or escapement with a solenoid? Any examples to
> work from?
>
> Mark
>
1. Obtain a cheap quartz clock movement. Cut the at least one trace to the
drive coil.
2. Place a 50-100 microfarad capacitor (electrolytic is ok) in series with the
clock drive coil.
You may have to fuss with the value to get it right.
3. Drive the clock coil-capacitor with the output of pin 4 of U8 of the Shera
circuit.
A typical quartz clock movement requires a 10-20 msec long 1-1.5 V pulse on the
coil to step the
clock one second. But each second is opposite polarity. Pin 4 of U8 is the
heartbeat pulse.
The capacitor takes the derivative of the heartbeat giving the necessary
alternateing sign pulse train.
Note that positive pulses will correspond to odd(even) seconds and negative
pulses to even(odd)
seconds. If the clock is odd number of seconds in error, then reverse the
polarity to the clock.
I have had a Shera circuit running three quartz wall clocks for months at a
time. They only get
out of time if I mess with them.
This is a brute force, cheap (elegant) physicists solution, not a fancy
electrical engineers
solution.
Bill Beam, NL7F
Bill Beam
NL7F
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