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Electronically Impulsing a pendulum for a clock

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

  1. markelectro

    markelectro New Member

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    Hello
    I am very new to electronics but I do love for clocks especially master clocks or electrically driven clocks.I have long wished to create a clock of my own.

    This clock would be using both mechanical and electrical component's first step of my project is the Pendulum.

    I have a std. Master clock pendulum with a heavy bob. I would like to impulse this pendulum electronically.The pendulum would be fixed by a suspension at the top and would be free to swing.

    The question is what options do I have to keep this pendulum moving in a precise motion?

    I see this as the first step and I will take one step at a time.so if you can advise me on the possibilities I would be very grateful.

    Cheers Mark
     
  2. j.p.bill

    j.p.bill New Member

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  3. Cabwood

    Cabwood New Member

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    I was thinking of an optical sensor which detects the passage of the pendulum. The pendulum could break a light beam, causing an electromagnet to energise. If positioned carefully, a ferrous or magnetic object on the pendulum's arm would experience a small pull, and the pendulum would receive a small top-up of kinetic energy.

    You would need to do this only once each cycle of the pendulum (not in both directions), meaning that some method to determine the direction of the pendulum's swing, and enable the electromagnet only on clockwise (or counter-clockwise) passes.

    Then you must consider the amplitude of the swing. Another optical sensor (perhaps) could determine if the pendulum is swinging enough, or not enough, and enable or disable the electromagnet accordingly.
     
  4. dave

    Dave New Member

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  5. markelectro

    markelectro New Member

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    j.p.bill

    Ya thanks for that link.I do like that website unfortunatly brian (the site owner)does sell his projects but unfortunatly for me he is not doing so at the moment so I decided to try and gain the knowladge to build such devices for myself.Much more fun but with little to no experiance it's going to be a long slog for me but I'm sure I will have fun on the way.

    I see brian uses a permanant magnet below the pendulum,that the simple bit but what does the electronics do? and where can I get diagrams from to try it out for myself?
    Thanks for the post.
    Regards Mark
     
    Last edited: Apr 8, 2007
  6. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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    Never mind.
    Others posted what I had in mind while I was editing.
     
    Last edited: Apr 8, 2007
  7. markelectro

    markelectro New Member

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    cabwood

    Sounds very interesting using an opto sensor.I had a thought of using a Reed Relay I suppose using the same method.

    Your sugestion sounds good but could you please explain in some detail the electronics beind the system?
    Ijn other words what would be required to build this other than the opto sensor?
    I am also looking at pic for this project.Using a pic to do the work of watching the pendulums swing and calculating when it would require som impulse.Please advise because it's only a therory I don't know how to put it together.

    Thanks for the reply.Regards Mark
     
    Last edited: Apr 8, 2007
  8. markelectro

    markelectro New Member

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    3V0
    Thanks for your reply.
    I thinks also you are sugesting an opto sensor.So does this mean the opto sensor can act the same as a switch? when the pendulum reaches it the sensor would turn on the electro magnet thus providing the slight magnetic pull?
    Sorry to sound a bit simple but this is not that simple for me as I'm not quite sure what componants are capable of.


    Thanks for your reply.Regards Mark
     
  9. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    The magazine EPE did a project a little while back, actually April 06.
     
  10. Leftyretro

    Leftyretro New Member

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    "Sorry to sound a bit simple"

    Well the detection of the pendulum and activating a electromagnet is simple, however the what is not so simple is the timing of when to activate the magnet (and for how long) now becomes the timebase for the clock and has to correct for too fast or too slow conditions. A crystal controlled time base would be most likely needed and some kind of comparison circuit to keep the pendulum in sync with the electronic time base would have to be designed.

    In effect this type of project would relief the pendulum of timing responsiblites so that it's function would be just to supply the mechanical energy for the clock works. The electronics support via the electromagnet would be the timebase and correction function.

    Neat idea and hope you share what you might come up with.

    Lefty
     
  11. Rolf

    Rolf Member

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    You will need a highly accurate electronic time base (crystal osc.) divided down to the half the period of your pendulum. This time base output has to deliver a short pulse, compared to the pendulums period of swing, maybe 10%. This pulse is amplified and delivered to a electromagnet at the center bottom of the pendelums swing. A small ferrous metal piece must be fastened to the bottom of the pendulum for it all to work.
    How will it work? If the pendulum gets to the electro magnet slightly late, the magnet will pull and and speed it up until the pull and the drag is equal for each swing. This will of cause take some time but it will happen.
    If the pendulum arrives early then the pulse will drag it to a slower rate until the pull and the drag is equal for each swing.
    So when the pull and drag is equal during each pendulum swing it will be in synchronization with the electronic time base.

    Edit. Of cause this will only work with an escapment type of mechanical clock.
    Maybe the same scheme would work for a free swinging pendulum if the electro magnet was moved up to the end of the swing, I don't know.
     
    Last edited: Apr 8, 2007
  12. markelectro

    markelectro New Member

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    lefty n rolf

    So to simplify we are at the moment looking at -

    Pendulum activation via an electro magnet

    pendulum control via electronic time base (crystal osc.)

    A ferrous piece of metal fitted to the bottom of the pendulum for the electro magnet to work with.

    That sounds all so good.What hard ware (electonic parts)would also be required.Does the crystal osc. do all the calculations?

    Regards Mark
     
  13. markelectro

    markelectro New Member

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    Nigel
    I will take a good luck at your site on pic programming.It's an area I would very much like to get in touch with.
    I looked through the web and came up with a site-

    http://brunningsoftware.co.uk/index.htm

    This man provides what is required for me to start learning.I am at the moment considering purchasing some of his products.Unless you can point me in another direction or advise of a better route?Would like to hear from you on that.

    Regards Mark
     
  14. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I've never had any dealings with his products, but they certainly appear to be OK - only drawback is the cost, it's quite expensive.

    However, it is a 'one stop' solution, and presumably starts from a lower point than my tutorials.
     
  15. CheapSlider

    CheapSlider Member

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    The OP said that they have a "std. Master clock pendulum with a heavy bob" and they are looking for a way to maintain the pendulum using electricity (rather than the more traditional weights ?)

    This is known as an electrically maintained pendulum. (The link is more mechanically oriented than electronics)
     
  16. RODALCO

    RODALCO Well-Known Member

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    Markelectro
    Great topic !
    I am currently working on a similar idea but in my case it is to synchronise two Bürk 3/4 sec. master clock pendulums so they stay exactly in step.

    I have a FAVAG 2/3 sec masterclock with Hipp Toggle.
    The Hipp Toggle priciple is best one to use in your case.
    The activation switch detects the decrease in swing of the pendulum and will provide a closing contact impulse to the pendulum which has a iron bar underneath which will be attracted by the coils which are mounted underneath.
    This happens approx every 20 swings.
    The Hipp Toggle can probably be made with an opto electric pick up as well, to detect it.

    edited for typo's RF.
     
    Last edited: Apr 8, 2007
  17. RODALCO

    RODALCO Well-Known Member

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    Also I'm working at the moment on a external very accurate timebase upon a 4.19 MHz crystal, in Crystal oven.

    ( Pendulum clocks with invar rods are very accurate, but occasionally may drift a couple of seconds a week. )

    4.194.304 MHz divide by 22 gives one Herz.

    For a 3/4 seconds pendulum i need 4 complete, or 8 half swings for one impulse per 6 seconds. ( I choose this value because i may use it for 2/3 seconds clocks as well )
    I have not got a 1 second pendulum clock at the moment because of the hughe shipping costs to New Zealand $1000 NZ or 700$ US .

    I'm thinking along the line of using a CMOS 4017 which counts the 1 seconds impulses from the 4017. decode the 6 seconds, and provide a synchronising impulse to the pendulum.
    The 1 second impulse is about 0.2 seconds long.
    By AND gating the 0.2 and 6 seconds impulse together to a driver transisitor (2N2222) a impulse can be put into the coil to drive the pendulum.

    I haven't got this far yet because of 2 young children at home and long working days, and too much time on the forums i admit, but I will get onto it now sooner because of your interest in this great topic too.

    This impulse can't be to strong, because the pendulum is already driven through the graham escapement from the electrically wind clockwork.

    What country are you from BTW ?

    Regards, Raymond
     
  18. ljcox

    ljcox Well-Known Member

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    No-one seems to have mentioned that the natural frequency of the pendulum (ie. it's frequency when it is swinging without the electrical assistance) needs to be as close as possible to the frequency that it is to run at when electrically driven.

    Otherwise, it will be impossible to make it sync with the electrical signal from the crystal oscillator (divided down of course).

    Instead of a 4017, you could use a presettable counter such as the 74HC161.

    This has a synchronous preset. Configure it to preset to 10 (ten) when it reaches 15 (ie. when Tc (pin 15) goes high. It will then be preset to 10 at the next clock pulse. Thus it is a modulo 6 counter.

    The advantage of this is that you can use the Tc output (gated with say 0.2 sec) to drive the pendulum pulse.

    If you wanted say a modulo 7 counter, then preset to 9, etc.
     
  19. bobledoux

    bobledoux Member

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    There is a design that uses the magnetic drive coil as the sensor, as well as the "motor." The pendulum holds a magnet. As the magnet approaches the coil it induces a voltage in the coil. This voltage turns on a switching transistor that discharges a capacitor into the coil to drive the pendulum.

    Solarbotics.com sells a "SunSwinger Pendulum Kit" for $30 that is powered by a small solar cell. The drive circuit consists of two transistors, two capacitors, two resistors, a coil, diode and solar cell. You can download the manual for the kit at their website.

    This design certainly has promise for driving a clock pendulum.
     
  20. markelectro

    markelectro New Member

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    RODALCO

    Thanks for the reply.

    I have long been interested in master clocks but like you my mind tells me to make one or some of my own.Differance between us is I don't have any Electronic's experiance at all so It's a case of asking those that have what my possibilities are.

    I do have a GPO.36 Master with hip n toggle.This is a very good and practical solution BUT!! I did want to try a more electronic route.

    Shame you can't get a 1 sec beating master closer to home but keep on trying.
    Thanks for everything,if you can help with electro advice for this project I would like to hear from you.

    Regards Mark
     
  21. markelectro

    markelectro New Member

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    Ray
    again thanks thanks for the info.I will read through your post and see what I can pick out of it.but it seems to closer to what I am looking for with my project.

    I am from the Uk. but I will swap you places if you like
     

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