[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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