[time-nuts] synch for pendulum clock....
jim77742 at gmail.com
Sun Dec 11 18:16:37 EST 2011
I acquired an old pendulum regulator from about the 30's-40's and it had an
electromagnetic coil and a small magnet attached to the pendulum. Some old
electronics passed a constant (but adjustable) current through the coil
either pushing or pulling the pendulum slightly to make its amplitude
bigger or smaller. This enabled you to make slight adjustments in its
period, so you could speed it up or slow it down gently.
I disconnected those electronics and instead passed a small current through
from a digital clock built from a microcontroller and a cheap ebay
rubidium. This current was periodic so it gave the pendulum a very slight
nudge every swing (like pushing a child on a swing).
This worked extremely well and the clock's second hand was spot on (to the
eye) for months.
Then I moved house and the clock was no longer inside but relegated to the
garage where the temperature varies quite a bit (10-30 depending on time of
year). The temperature variations overpowered the slight nudges and it no
longer keeps good time.
I'm seriously toying with the idea of putting a small heater in the
cabinet, so I can have an OCPO - oven controlled pendulum oscillator.
On 12 December 2011 09:13, Don Latham <djl at montana.com> wrote:
> and similar stuff found by googling "driving pendulum clock"
> Lots of food for thought. Mumford has put some thought into it.
> A lot depends on why you want to drive the thing; e.g. measuring
> perturbations in the gravitational field, a sensitive barometer,
> temperature sensor, etc. etc.
> Brian, WA1ZMS
> > This was talked about several years ago, but did anyone get a fully
> > functional design running using electromagnets to synch at one or both
> > ends of the travel?
> > In the meantime I am using a sensor to measure the time period of the
> > pendulum for this particular new grandmother wall clock and from that, I
> > can synthesize a pulse train from one of the 10MHz lab clocks to drive
> > the electromagnets to cause a subtle synch at the end(s) of the pendulum
> > travel. The pulse train freq is custom for a given clock.
> > Anyway...... that's my scheme for now.
> > Feedback welcome.
> > -Brian, WA1ZMS
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