# Electronically Impulsing a pendulum for a clock

Discussion in 'General Electronics Chat' started by markelectro, Apr 8, 2007.

1. ### RolfMember

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Different set op........

In order to not show anything from the outside of the case (at least on my grandfather clock), I think I might try a setup like this:

Because of the lesser mechanical leverage I would pulse it on each swing.
Hope the drawing is clear enough to illustrate what I mean, I newer took drafting.

2. ### RODALCOWell-Known Member

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Rolf,

That principle you drawn up should work fine.
Good idea to pulse it every second, because of more torque required.
You may have to experiment with the voltage to get a strong enough pull from the magnet.
Perhaps use a 2N2222 switching transisitor instead of a BC 547.
Keep us posted with the results.

Kind regards
Raymond

3. ### markelectroNew Member

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jcox
To get this topic going again I would like to ask about the theory for the Natural Frequency of the pendulum.
this sounds a very important factor to determin the correct amount of forced impulse the pendulum requires,Could you please advise on how this is measured?

Regards Mark

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5. ### markelectroNew Member

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To all

Thanks to ray and the input of others I am now about to construct a circuit for impulsing a pendulum using ray's methods.When I acctually construct somthing to show I will post the results for you all to see.

I would welcome any other thoughts/methods you have on this topic.

Regards Mark

6. ### RODALCOWell-Known Member

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Natural frequency of pendulum

It is calculated via the formula

T = 2 x PI X sqr rt( l / g )

Where T = time to swing back and forth
PI = 3.1415926
l = length in metres
g = gravity force as 9.81 NM ( Newton metres )

1 second is around 1 metre
3/4 second is around 0.6 metres
2/3 second is around 0.4 metres
1/2 second is around 0.25 metres

7. ### markelectroNew Member

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Ray
cheers for that.

For the benefit of all the none electro educated people, myself included I have tried to re-draw you schema using livewire. Unfortunately I could not get the circuit to work in the programme but I feel this is due to catalogue of parts in livewire do not act in simulation as the real circuit would.

Again for the benefit I have detailed some of the parts in the circuit so we can find Data on the web.

Could you or someone please advise on some of the components in the circuit just so we understand what is happening to give us the end result of a pulse every three seconds.

what do these parts do for the circuit. Not really looking for data of a particular part just what each part does for the circuit, just to help understand what is happening.

1).The 4.19mhz crystal oscillator
2).The 4n35 optotransistor optocoupler
4). the 4081 Quad 2-input AND gate

Ray if you could tell me if any of the parts of the schema I have done wrong I will change them.

The circuit is to drive a 3/4 sec pendulum I will have to adapt the schema to drive my 1 sec pendulum. Any advise on how best to do this will be welcome.

regards Mark

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8. ### Nigel GoodwinSuper ModeratorMost Helpful Member

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There doesn't seem to be anything in that circuit to do what you want?, and for a start there's no oscillator in it!. Assuming the 'xtal' is actually a full oscillator circuit (and you've shown it connected completely wrong), then it's much, MUCH, too high a frequency.

9. ### markelectroNew Member

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Nigel thanks for that!!

Thought I was going fine,just proves how my lack of knowledge in this subject shows in not understanding how the circuit components go together.

As you are probably aware I am in the leaning stages of this and would ask if you could put me on the right tracks.I knew that there could be a good chance that id did something wrong when re-drawing the circuit.
Please find the circuit I did try to copy from attached. I may have miss understood it when re-drawing.

If you could help me I would be pleased.

Regards Mark

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10. ### RODALCOWell-Known Member

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Thanks Mark for posting the schema, and Nigel for commenting on a drawing error.
Mark, where you put the crystal oscillator there should be the complete clock cct. eg the Quartz movement.

As most quartz movements run on a 1.5 volts supply, it is possible to drive them from any dc supply more than 1.5 volts as long as there is a suitable series resistor to limit the current flow.
In my circuit a value of 560 or 680 ohms is fine for a 6 - 8 volts supply.
Important is to put across the quartz movement a 1.7 - 2.2 volts led, and a capacitor. ( 100µF 10Volts )
I have omitted the led and use a 4N35 which has a opto led in it and added one or two 1N914 or 4448 diodes to get an approx 2 volts drop across the quartz movement.
The 4017 is used for dividing out a 3 second impulse.
The 4081 is used to AND the 1 second pulse and 3 second pulse together and give a pulse to the coil.
For a 1 second clock you could do away with the 4017.

The best way of trying your quartz source is.
Get a accurate quartz movement for 1.5 volts, experiment with one from a gutted kitchenclock or whatever other clock you can get your hands on.
Where the 1.5 battery goes put a red LED and capacitor in parallel.
Then fit a 560 ohms series resistor and run it from a 6 volts supply.
It should go and the LED blinks at 1 second interval.

11. ### RODALCOWell-Known Member

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Attached is the schema from the quartz clock oscillator i use.

This part goes in the box marked clock circuit.

Should make it clear to understand i hope

Cheers

Ray

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12. ### markelectroNew Member

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Ray

Thanks very much!!!

This is the point of these forums, firstly it brings on people like me who have a burning desire to get into electronics and goes a little astray with the knowledge and secondly it brings us with common interests together even when we are far across the globe from each other.

Just shows you how wrong it can get when you have little experience. I must have got crossed wires somewhere. Now everything getting clearer.I would have never guessed that an acctual quartz movement was involved (shame on me)

Anyway ray I will get me head back down again and re-studdy the drawing again.

Regards Mark

I will get my head back down

13. ### markelectroNew Member

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Ray n all
Going back a few steps.You use this to sync together your two clocks.Can the same circuit be used to impulse a free pendulum without the aid of a mechanical impulse?

What alterations if any would be made to suit this?

Regards Mark

14. ### RODALCOWell-Known Member

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In principle the circuit should work fine.
I use it for synchronising 2 pendulums at the moment which i will expand to 4 when time allowes.
Each driver has its own driver transistor and coil taken from the same supply, with a 2200 µF capacitor near the 547 to minimise any dips in the supply rail.

I like also to try instead of the steel nut on the pendulum rod, the rectangular bar which is used by the FAVAG clock. I think that way you will get better torque if the timeconstant of the penulum is out too much.

Bear in mind that the Bürk clocks have graham escapements and ± 98 % of the energy comes from the movement, and may be 2 % is used for correction, in case of excessive temperature drift or barometric pressure changes. ( just a guess )
The rod is from Invar, which is an alloy between nickel and steel which hardly expands or contracts with temperature changes.

If you require all the energy to come from the coil then you need to try to experiment with the amount of turns, or supply voltage.

Look at it as the child on a swing principle. You give a push each swing cycle, swing keeps going, you also can give it a harder push each second cycle, swing keeps going.
You push the swing to early extra torque is required, correction in progress.
you push the swing to late, hardly any effort is required and things are running fine. ( It gives the approx. idea how it works )

Any impulsing circuit should work, as long there is a driver which can supply an impulse to a coil.

I have access to precision quartz movements from old power board time switches which have less drift than 2 seconds a month, so these were choosen.

If you have access to radio signal impulses like Frankfurt 1500, I can't see any problem in decoding a 1 second impulse from that to synchronise a clock from that too.

15. ### markelectroNew Member

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Ray

great point.I wish I knew what a precision quarts movement was and who sold them as I would buy one.

What I do have is an SR250-

As you will see this unit recieves a signal from time transmitters in the UK. and is primerally used to impulse to slave clocks.It can deliver 1 sec and 30sec pulses to your slave.

Do you think this can be used for the project and were would it fit in?
or do you know of an web sorce for the precice quartz/can you supply me one?

Regards Mark

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19. ### RODALCOWell-Known Member

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I wouldn't mind getting one of those myself, a discrepancy meter.

If you get stuck, i can post you a quartz time base to be used for the clock circuit.

Any one second timing circuit should be able to be converted to drive a coil at 1, 2, 3, 4, 5, 6 ...... seconds.

20. ### markelectroNew Member

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The meter in the link was mine!! infact all the clocks and bits in the links were or are the ones I own.
Unfortunatly the Descrepany meter I sold somtime ago and now wished that I hadn't as you can imagine.:-(

If you want to get your head around another project I have wanted to create a Discrepancy meter of my own.Got to get brain storming and come up with a solution.I want to run this from a master and again compare it to a accurate time base like in a quartz clock or a radio sinal or frequancy singal via the mains.

One idea is it could be consructed using stepper motors one from master time and one from accurate time base to give the comparison.This would be a good addition to any master clock.

Any thoughts?

Well this is very kind of you If I require one I will contact you.

Regards Mark

21. ### markelectroNew Member

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Ray

Been looking for info on the - RM 3451/pca 15115p part in the Schema.Could you tell me what this is as I googled without success.

Mark