Rotating pendulum clock circuit

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We've long had a clock somewhat similar to this


I don't know whether that's a real torsion pendulum clock, but ours was  
a pretend version, with an ordinary electronically driven clock dial,  
and an entirely seperate mechanism (with a separate battery) to make the  
pendulum rotate.

The other day I had a reaon to take the thing apart (one of the hands  
had fallen off), and I took a look at the mechanism that drives the  
pendulum. We'd long since stopped putting batteries in it, since they  
seemed to run down quite quickly, and when I tried it, it no longer worked.

As far as I could see, the circuit consisted of a transisor, a resistor,  
and two electrolytic capacitors. There was no mechanical connection  
between the circuit and the pendulum drive. There is magnet mounted on  
the drive, suggesting that the circuit produces magnetic pulses - but  
there's no coil.

I eventually surmised that the required magnetic field is being  
generated by a track on the circuit board. It doesn't seem very  
efficient, and perhaps that's why the batteries ran down so quickly.

Anyone familiar with the technique?


Re: Rotating pendulum clock circuit
On 22/08/2013 12:43 PM, Sylvia Else wrote:
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I'd have expected an electromagnet too. I don't imagine a PCB magnet  
coil would be worth SFA.

Try poking around here;

Re: Rotating pendulum clock circuit
On 22/08/2013 8:02 PM, Gonadicus wrote:
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On further examination, the circuit makes no sense, there being nothing  
connected to one side of one of the capacitors. I can see a small piece  
of a very fine wire protruding from one of the other solder points (the  
thing looks to have been hand soldered). I speculate that there was once  
a fine coil there, also connected to the otherwise unconnected capacitor  
terminal, that has broken off and been lost. This would explain the  
failure of the mechanism years ago.

Getting the back off this thing to replace the battery is frequently a  
difficult task. That coupled with what looks to have been a fragile  
mechanism was clearly asking for trouble.


Re: Rotating pendulum clock circuit

. . .

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Makes me think of various faux perpetual motion toys.

Here is a an old patent for those:

The circuit is shown there but it is simpler than the one in your
clock, consisting of the battery, one transistor, the coil, and, ...
nothing else.

Andy Wood

Re: Rotating pendulum clock circuit
On 24/08/2013 7:25 AM, Andy Wood wrote:
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A nice example of why the patent system needs a revamp.

Even the patent holder appears to have realised that the patent is  
worthless, given the failure to pay the maintenance fee.


Re: Rotating pendulum clock circuit

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Take some clear pictures of the pcb/drive and post a link.

Torsional pendulum clocks require very little power,
spring versions are called 400 day clocks - they run that
long on one winding of the spring. An interesting
variant (Atmos) runs just from variations in atmospheric

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