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
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