[time-nuts] Regulating a pendulum clock (Jim Palfreyman)

J. Forster jfor at quik.com
Sun Aug 8 15:03:19 UTC 2010


That's why I suggested killing the BW of the opamps in the partial H
bridge configuration previously suggested. Transient response is almost
unneeded.

-John

==============


> On 08/08/2010, mike cook <mike.cook at orange.fr> wrote:
>> Check out Bryan Mumfords page.
>> http://www.bmumford.com/clocks/em2/index.html
>
> I did not want to kick the pendulum with a pulse each swing as the
> drive would be part and parcel of the existing clock mechanism. What I
> was interested in was Don Mimlitch's description of how the Riefler
> Pendulum and Warren Telechron Master Clocks work. The control of
> constant current to the electromagnet under the pendulum seems quite
> similar to an EFC and could perhaps be used in a PLL to sync with a
> reference source, as Jim was originally proposing.
>
> Of course, retrofitting a conventional clock like this would require
> the attachment of a magnet to the pendulum, necessitating reducing the
> weight of the pendulum to account for it, installing an electromagnet
> under the pendulum and arranging for each swing of the pendulum to
> produce some form of pulse signal. Of course, the timing in pulses per
> second of the original clock would have to be determined and the
> frequency standard divided down to match this rate before both signals
> are fed to a comparator and LPF to provide the 'EFC' voltage to
> control the electromagnetic current.
>
> Steve
>
>> Le 08/08/2010 11:14, Steve Rooke a écrit :
>>> I was rather more thinking of the setup that Don was suggesting as not
>>> many domestic clocks have a seconds pendulum and it would otherwise
>>> take dividing down a referenced oscillator to the correct frequency.
>>>
>>> Cheers,
>>> Steve
>>>
>>> On 08/08/2010, Neville Michie<namichie at gmail.com>  wrote:
>>>
>>>> Not many clocks are set up with the gear to modulate the rate,
>>>> but they are all still sensitive to injection locking.
>>>> A tiny rare earth magnet on the pendulum (say 1/2 way down the
>>>> pendulum rod)
>>>> and a coil fed with a stretched (say 250ms long) PPS or for a seconds
>>>> pendulum
>>>> PP2S pulse will pull the pendulum into phaselock with a surprisingly
>>>> small amount of power.
>>>> In fact if you turn off the drive it would keep the pendulum swinging.
>>>> Cheers, Neville Michie
>>>>
>>>> On 08/08/2010, at 6:00 PM, Steve Rooke wrote:
>>>>
>>>>
>>>>> This is very interesting and I wonder if the capabilities of this
>>>>> system being applied to any clock pendulum. If this sort of control
>>>>> any pendulum, then I wonder if it's possible to sync it to some
>>>>> standard.
>>>>>
>>>>> Steve
>>>>>
>>>>> On 08/08/2010, Don Mimlitch<donmeis at yahoo.com>  wrote:
>>>>>
>>>>>> Jim Said:
>>>>>>
>>>>>>> It also has a coil mounted near the pendulum and a fixed magnet
>>>>>>> on the
>>>>>>> pendulum bar and this coil connects to a box down below with a
>>>>>>> meter
>>>>>>> and a knob. They are labeled in sec/day. The electronics in the box
>>>>>>> are not clear (being quite old) but by measuring the current in the
>>>>>>> coil it quite simply increases the current one way to slow the
>>>>>>> clock
>>>>>>> and the other way to speed it up. (I'll admit the physics of this
>>>>>>> doesn't make sense to me - but it works!)
>>>>>>>
>>>>>> I have a Warren Telechron Master Clock used in Power Stations in
>>>>>> the 20's to
>>>>>> regulate the 60 Cycle so that household clocks using synchronous
>>>>>> motors
>>>>>> would be accurate to seconds a day.
>>>>>>
>>>>>> This clock has a similar permanent magnet at the end of the
>>>>>> Pendulum and
>>>>>> a battery connected to a potentiometer to adjust the current flow
>>>>>> positive
>>>>>> or negative in an electro-magnet below the pendulum..
>>>>>> If the bottom of the magnet in the pendulum is "north" and the
>>>>>> current in
>>>>>> the electromagnet is flowing such that its top face is North, then
>>>>>> this will
>>>>>> repel the pendulum causing its swing to be wider and contrary to
>>>>>> common
>>>>>> knowledge the swing of a fixed length pendulum is not constant
>>>>>> regardless of
>>>>>> the swing. (Huygens discovered this in 1670 an found by forcing
>>>>>> the arc of
>>>>>> the swing to be cycloid instead of circular he could produce uniform
>>>>>> oscillation) Thus if the arc is longer the swing takes more time
>>>>>> and the
>>>>>> clock runs slower.
>>>>>> If the current flows in the opposite direction and the two magnets
>>>>>> attract
>>>>>> then the arc is shortened and the clock runs faster. Of course my
>>>>>> master
>>>>>> clock isn't as accurate as a Riefler pendulum clock. Also the
>>>>>> magnet in my
>>>>>> clock has lost it's magnetism over time and I can't use this
>>>>>> regulation.
>>>>>>
>>>>>> So the goal of your adaptation is to have precision control of the
>>>>>> current
>>>>>> flow in the positive or negative direction. Others on the list are
>>>>>> better
>>>>>> then me at describing how you might achieve this.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
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>>>>>>
>>>>>>
>>>>>
>>>>> --
>>>>> Steve Rooke - ZL3TUV&  G8KVD
>>>>> The only reason for time is so that everything doesn't happen at
>>>>> once.
>>>>> - Einstein
>>>>>
>>>>> _______________________________________________
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>>>>
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>>>
>>
>>
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>
>
> --
> Steve Rooke - ZL3TUV & G8KVD
> The only reason for time is so that everything doesn't happen at once.
> - Einstein
>
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