[time-nuts] Regulating a pendulum clock

paul swed paulswedb at gmail.com
Mon Aug 9 01:37:32 UTC 2010


Now I will get myself in a lot of trouble.
Why wouldn't a constant pulse at a 2 sec interval essentially lock the
pendulum after a bit.
If the pulse is always there and occurs just after the mid swing. I suspect
you do need to adjust current with a pot to get things settled. But
essentially open loop.
I have often thought about tinkering exactly like this if I ever ran across
a nice clock like the one at television network TVA in Montreal that used to
run network time. Unfortunately they would not part with it.
Good luck

On Sun, Aug 8, 2010 at 7:22 PM, Bruce Griffiths
<bruce.griffiths at xtra.co.nz>wrote:

> Mere fast blow fuses aren't usually precise enough to protect transistors
> against over current unless one uses rather large transistors.
> Overcurrent protected drivers are available and readily designed/built.
> Protection against di/dt transients due to external events is also
> advisable.
>
> Minimising the parts count isn't necessarily conducive to improved
> reliability when external hazards aren't taken into account.
>
> Merely resonating the coil without other filtering doesnt necessarily lead
> to low EMI when driving it with a voltage waveform having high edge slew
> rates.
> Some edge filtering to control the current flowing in the load capacitance
> is also advisable.
>
> Bruce
>
>
>
> Don Latham wrote:
>
>> fast blow fuse, resonate the coil to the pwm frequency. Parts count small,
>> tinkering in software instead of breathing lead fumes or whatever noxious
>> stuff the Europeans have forced us to use...
>> Don
>>
>> Bruce Griffiths
>>
>>
>>> No protection against external shorts or other undesired events.
>>> Extensive analog filtering to avoid creating an effective radiator of
>>> noise may also be necessary.
>>> Simple analog techniques are probably simpler/cheaper once the necessary
>>> filtering and protection are included.
>>>
>>> Bruce
>>>
>>> Don Latham wrote:
>>>
>>>
>>>> Hmmm lemme see. I think I'd use a 12 volt supply and two transistors
>>>> driven by two outputs on my Arduino,basic stamp,picaxe or other whizzie.
>>>> I'd then implement a PID controller essentially using the 1 sec pulse
>>>> from
>>>> the pendulum and the 1 sec pulse from my Rb, satellite receiver, crystal
>>>> clock, or whatever. The appropriate output pin will be brought to
>>>> ground,
>>>> and the other driven as a pdf with the rate given by the pid loop.
>>>> Temperature and even pressure corrections can be applied within the
>>>> gizzie
>>>> software. External parts, minimum. Opportunity to play with tuning,
>>>> maximum.
>>>> Don
>>>>
>>>> Bruce Griffiths
>>>>
>>>>
>>>>
>>>>> J. Forster wrote:
>>>>>
>>>>>
>>>>>
>>>>>> You are picking very unimportant nits.
>>>>>>
>>>>>> If there were a small noise spike from the opamp, it'd goose the
>>>>>> pendulum
>>>>>> a tiny amount. That would be corrected on the next swing.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>> Heuristic analysis of this type is counter productive.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> You are turning a trip to the corner store into an Apollo Moon
>>>>>> Mission.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>> Reliability is paramount in a circuit that may be required to work for
>>>>> decades.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> BTW, since the =drive does not to be bipolar, one of the NPN and PNP
>>>>>> transistors can be deleted. They never turn on. So you are left with
>>>>>> two
>>>>>> opamsa, =each with a simple emitter follower.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>> The original request was for a bipolar drive.
>>>>> The lack of short circuit protection is poor design practice when
>>>>> driving an external load.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> -John
>>>>>>
>>>>>> ==============
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>> Bruce
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
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>>
>>
>>
>
>
>
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