Can a clock pendulum be slowed by adding a resistor to the PSB?

I'm looking for advice, please. I’m a manufacturer, not an engineer, and not very technically minded, sorry!

I manufacture and sell wall clocks that have a swinging pendulum. The pendulum mechanisms are made overseas and designed for the pendulum to swing approximately 60 times per minute.

I would like to slow down that swing to approximately 30 or even 20 swings per minute.

Hopefully attached are photos of the pendulum mechanism (which fits on the back of the wall clock), showing the PCB, and capacitor.

Could you advise, please, on what's involved in slowing down the pendulum swing? Is it a simple case of installing a resistor, or different size capacitor? (The existing capacitor is 47uf16v).

I have 1000 of them that need to run slower, instead of at the 60 per minute.

Many thanks,

Richard

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Hi

Generally, I think the factors that affect pendulum speed is the length and weight. I'm not an expert about this but maybe you can control it by the power gears on the clock itself.

I have a few questions though. I noticed that this is ran by batteries, right? Also it the swinging of the pendulum synchronous with the turning of the clock?

I read this article about "pendulum("")":http://www.explainthatstuff.com/how-pendulum-clocks-work.html, maybe it can help.

Hi Kevin,
Thanks for your reply.
My situation here is somewhat different to the usual pendulum scenario.

There's no actual clock... the pendulum mechanism has a battery, and it makes the pendulum swing.

And yes, as you say, normally a pendulum swing can be altered by changing the weight and length of the pendulum, but in this case, I cannot add any more weight, or any more length.

So, if there is a solution, it will have to be something else... but what... ah, that is the question

Hi, frequency of the pendulum is determined by the osc circuit in the clock by the xtal,cap,and the resistor in the tuned circuit you can vary this in your circuit by varing
the resistor value here instead of 560k resistor change that by a 1 meg preset and adj to get the required freq you want. you can also try varing the capacitance by trimmers but make sure that they come parallel to the the coil . first measure the present freq and note itt here you require only half of it. by varing the resistor or cap value in the rc net work you can change the freq dont try to series any resistor to cap,try to reduce or increase the value of the components avalible in the ckt, it is better to fix cap value in the ckt same and vary the resistor value.
pl dont forget to review my rating.

Thanks

V.Sambath kumar.

Hi there Sambath and Richard. I think that will just reduce the arc of swing.
30 swings per minute is like 1 swing per 2 seconds.
If the above doesn't work, would lowering the voltage of the battery do the trick?

Thanks. I'm interested to know the sol'n to this problem.

Hi Justin,
Lowering the battery voltage will not help you ,because the power taken by the coil to produce the magnetic field to move the gear wheels to move the pendulum is taken from the battery voltage if that voltage is reduced it will stop working.
What we are doing is reducing or increasing the speed of the oscillator circuit to produce magnetic field accordingly,if we want fast movment the freq should be more so we require fast switching of the osc circuit. pl ref the file attached this will help you. don,t forget to review my rating.

Good Luck.


V. Sambath kumar

Thanks for the replies, guys!

There are no gear wheels... this is not an old fashioned mechanical pendulum mechanism. The photos hopefully show the workings, or lack, thereof.

The power source has to be a standard AA battery... these mechanisms are already manufactured... the only option I'm hoping for is something like adding a resistor to the PSB...

You are trying to change a natural response, dictated by the length, to a forced one. I don't think this is as easy as it seems. The battery doesn't make the pendulum swing, gravity acting on the mass does, all the battery does is provide the extra energy kick in synchronization with the swing of the pendulum to keep it swinging, since it is a damped system, and would eventually stop,
Cheers,
Richard

Richard is correct. The frequency of a pendulum's swing is determined by it's length and weight.

https://en.wikipedia.org/wiki/Pendulum
This article will provide the formula for calulating the frequency from the length and mass.

The battery powering mechanism does not affect the frequency. It just provides a tiny amount of energy boost on each swing (to overcome the slowing effect of air resistance), but only keeps the pendulum swinging at it's natural frequency.

The only ways to slow the pendulum are:
1) increase the length (distance from the fulcrum to the weight's centre of mass);
2) increase the weight at the end.

Have you ever sat on a swinging seat out in the garden, or a swing in a park. Put some energy into the system, it will swing at its natural frequency, dictated by the length of the seat from the pivot point. Doesn't matter what energy you put into it, it has no impact on the frequency you are swinging at. Your pendulum is the same. Sometimes, there are swings near by for small children, which are much shorter, you may have noticed the difference in the frequency if you have been on a longer one near by. Just thought I would add that as it is something that most of us have done sometime in our past, and the laws of physics haven't changed in the meantime,
cheers,
Richard

Thank you for the replies, guys!

Yes, I suspect I'll have to accept that there's no easy way to solve the problem. I have made the pendulum length as long as possible, and the weight as heavy as possible.

I'm not giving up just yet, though. I still can't fully accept that making a change to either the capacitor, the coil, the PSB, or even some mechanical alteration, won't do the trick.

In the meantime, I can still use the existing pendulum mechanisms, with their standard swing :)

Thanks, guys