[time-nuts] 50/60 Hz clocks
bruce.griffiths at xtra.co.nz
Sat Mar 19 16:30:03 EDT 2011
An OTT solution might employ a regenerative divider to generate a 15MHz
signal from a 10MHz input followed by a digital divide by 250,000 circuit.
One could employ an inexpensive Gilbert cell mixer in the regenerative
divider to keep the cost down.
Bob Camp wrote:
> Most likely the lowest parts count is to divide to a narrow(ish) 20 Hz square wave and then drive a resonated transformer with a pulse. The output won't look pretty, but it should drive a small clock motor just fine. Done properly, there should be very little power involved.
> If you are going to use anything complicated, just run a gizmo that lets you have a PLL at a factor of 3 times the input. Once that's done - problem solved.
> On Mar 19, 2011, at 3:01 PM, Michael Poulos wrote:
>> 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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