If the plan is to drive a mechanical clock, I assume long term stability is more important than phase noise. Many small microcontrollers (I use 8051's from Silabs) have a built-in PLL that can be set to run at 15 MHz from an external 10 MHz reference (applied to the external oscillator input), and use the program space to implement a divider that will give you exactly 60 Hz. That is a one chip solution. The processor will accept the sinewave from the reference oscillator without extra shaping circuit.
Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -----Original Message----- From: Bruce Griffiths <[email protected]> Sender: [email protected] Date: Sun, 20 Mar 2011 09:30:03 To: Discussion of precise time and frequency measurement<[email protected]> Reply-To: Discussion of precise time and frequency measurement <[email protected]> Subject: Re: [time-nuts] 50/60 Hz clocks 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. Bruce Bob Camp wrote: > Hi > > 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. > > Bob > > 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! >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
