[time-nuts] 50/60 Hz clocks
Michael Poulos
poulosmd at gmail.com
Sat Mar 19 19:01:43 UTC 2011
Robert LaJeunesse wrote:
> Poor man's solution: Use an Arduino to read the Thunderbolt 1PPS and lock a 50Hz
> (or 60Hz) square wave to the 1PPS. Any resulting jitter can likely be kept in
> the tens of microsecond range, easily filtered out by the clock mechanics.
> Filter the square wave a bit and feed it into an audio amplifier (or two) of
> sufficient power to run the clock. (Possibly a 12V powered bridge amplifier at
> ~14W would be adequate?) Use some sort of audio output or filament transformer
> backwards to create the proper line voltage to run the clock. Maybe run the
> whole thing off a 12V battery with float charger for uninterruptible timing.
>
When using the power transformer "backwards" keep in mind the impedance
output of the amplifier. Audio amplifiers are rated in watts into an 8
ohm (or 4 ohm) load. So, what you want is a power transformer of desired
wattage and the low voltage side having a volt and amps rating that
would match an 8 ohm load or 4 ohm load. Then, you hook it "backwards"
(i.e. as a step-up transformer) to an audio amp of a rating higher than
the transformer then hook the signal to the input and use the volume
knob as a throttle. Turn up until desired voltage is reached.
Have fun!
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