Re: Regulate pendulum clock with quartz crystal?

Newsgroups: sci.physics
From: Bill Bowden <wrongaddr...@xxxxxxx>
Date: Mon, 05 Nov 2007 20:59:21 -0800
Local: Mon, Nov 5 2007 8:59 pm
Subject: Regulate pendulum clock with quartz crystal?

Is it possible to regulate pendulum clocks for quartz crystal accuracy
without adjusting the length of the pendulum? Does it require a motor
to adjust the pendulum length with a moving weight, or can it be done
by some magnetic means of a permanent magnet on the pendulum and fixed
electromagnet driven with an accurate pulse from a crystal?

-Bill


The methods previously specified, such as an electromagnet under the
pendulum, etc. are crude and use lots of power. And if the power goes
your clock instantly loses it's accuracy.

The best way to do this is to put a sensor on the end of the bob,
such as a small dicrete coil, which passes over a magnet below it, and
provides timing impulses to low power circuitry installed in or behind
the bob. Said circuitry times the sensor pulses and controls a small
stepper motor, which drives a jackscrew that moves up or down a small
weight that effectively modifies the length of the pendulum.

All the circuitry, including the AA battery, fits behind the bob.
Once reaching the optimum set point, very little adjustment or
updating is needed and hence very little power is drawn from the
battery. In the event of lost power, such as the battery dieing, the
last setpoint is maintained and your clock is still very accurate!

As far as the clock mechanism itself is concerned it's still a true
grandfather clock. It uses no electricity whatsoever.

Timing reference can be quartz or external shortwave.

-Bruce
bbowen@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx



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