That's even simpler! You have to size the capacitor just right, but it's probably not too critical. Thanks Chuck
Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -----Original Message----- From: Chuck Harris <cfhar...@erols.com> Sender: time-nuts-boun...@febo.com Date: Wed, 18 May 2011 14:09:39 To: Discussion of precise time and frequency measurement<time-nuts@febo.com> Reply-To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Subject: Re: [time-nuts] Sidereal timekeeping It's been a while since I did it, but as I recall, a simple way of driving the typical motor on a dime store clock is: FF-Q-------------)|-------------MOTOR--------+ .............................................| FF-/Q----------------------------------------+ The capacitor charges up during the times when the FF's output is level, and produces a spike of alternating polarity when the FF toggles. You need 1 level transition every second, so the FF has to toggle at a 1/2 HZ rate. -Chuck Harris David Martindale wrote: > The motor is essentially a permanent-magnet stepper motor. The rotor > and stator have just 2 poles each, so the rotor has two stable > positions 180 degrees apart that provide holding torque. Thus, the > motor holds position with no input current for most of each cycle. To > move it, the drive applies a short current pulse to the motor. The > pulses are alternating positive and negative polarity, so you'll need > something like an H-bridge to drive it. Using a 3 volt supply instead > of the 1.5 that the motor was designed for would supply more power > than the motor needs if you keep the drive pulse the same width, but > you should be able to reduce the pulse width until the energy is about > the same as with 1.5 V drive and have the motor still operate. > > Without having actually tried it, I think you should be able to select > a suitable tradeoff between reliable motor operation and power > consumption just by adjusting the "on" time of the drive pulse - no > voltage regulator or voltage dropping resistor needed. > > There's only one stator coil to the motor, and one drive signal, so > you can't control motor direction. The magnetic structures are > apparently deliberately asymmetric to ensure that the motor always > rotates in one direction when it receives a pulse of the appropriate > polarity. (Get the pulse polarity wrong, and the motor just doesn't > rotate). > > Dave _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.