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Thread: Clock Pendulum Needs Bigger 'PUSH'

  1. #21
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    correction some clocks have two windings which is used to pulse both ways ie north /south they normally have three connections to the coil just check this ???

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    Quote Originally Posted by hinekadon View Post
    cant draw the circuit for you but the transister pulses and with cap it discharges slower than with out it so it holds the mag flux for a longer period if you have a long duration ( timebase) oscillorscope you can see the oscillations they are timed charge/discharge to match the pendulums actual natural rythm any over mag will slow the pend ,any to fast will increase mag and the hang time is worked to assist in a minor way to maintain this rythm . hope your lost now lol?????/don
    Yeah you did !!!
    Nah I get what you're saying, but the way I figured it, (can't tell too well in those photos) looks like the coil is centre tapped which makes two coils. One to repel the passing pendulum and one to fire the transistor. So the battery would charge the cap during the dwell time via the resistor (to save the battery), The pendulum magnet passes the coil inducing current to fire the transistor's base then in turn allows the cap to dump it's load instantly in the other coil which pushes the pendulum away.

    So what's the ceramic cap for ?

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    suppresion of the magnetic spike on the transitor backwards

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    SOLVED!! Well sort of solved, but it is fixed and now swinging quite happily...

    After converting it to 3v and the thing slowing down to a stop, not even a slow swing, I decided to play with it once last time.

    For some unknown reason I reversed the arm (put it on backwards - so brass shiny sides facing inwards), and (with a push), I got it swinging. Came back in 30mins and still swinging!! huh?
    I turned it around again (slight push), and in 5mins it had stopped.
    Reversed it again, and it was ok. I checked the level of the clock and it is flat.


    When reversed the disc was 4cm away from the back. When facing correctly it was about 6cm.

    I bend the upper metal like a S'ish shape and got the disc to 4.5cm and it has been swinging away all night quite happily and is still swinging this morning at a normal speed...

    So once again, many thanks for all the help and advice people.

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    Quote Originally Posted by GT250 View Post
    SOLVED!! Well sort of solved, but it is fixed and now swinging quite happily...

    After converting it to 3v and the thing slowing down to a stop, not even a slow swing, I decided to play with it once last time.

    For some unknown reason I reversed the arm (put it on backwards - so brass shiny sides facing inwards), and (with a push), I got it swinging. Came back in 30mins and still swinging!! huh?
    I turned it around again (slight push), and in 5mins it had stopped.
    Reversed it again, and it was ok. I checked the level of the clock and it is flat.


    When reversed the disc was 4cm away from the back. When facing correctly it was about 6cm.

    I bend the upper metal like a S'ish shape and got the disc to 4.5cm and it has been swinging away all night quite happily and is still swinging this morning at a normal speed...

    So once again, many thanks for all the help and advice people.
    Hmmm ... magnet facing the wrong way ?

  • #26
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    Quote Originally Posted by GT250 View Post
    SOLVED!!
    Quote Originally Posted by GT250 View Post

    For some unknown reason I reversed the arm (put it on backwards - so brass shiny sides facing inwards), and (with a push), I got it swinging. Came back in 30mins and still swinging!! huh?
    I turned it around again (slight push), and in 5mins it had stopped.
    Reversed it again, and it was ok. I checked the level of the clock and it is flat.


    When reversed the disc was 4cm away from the back. When facing correctly it was about 6cm.

    I bend the upper metal like a S'ish shape and got the disc to 4.5cm and it has been swinging away all night quite happily and is still swinging this morning at a normal speed...
    I am assuming that the centrifugal force of the disc (weight) is pushing the magnet a little bit outwards (away from the coil) when it is swinging.
    This is kind of confirmed when you reverse the weight towards the back, the centrifugal force pushes the magnet closer and it works better.

    A solution would be to add an extra small ballast behind the disc, when you have it facing the right way again. Example a fishing sinker glued at distance (maybe 2 cm) on a tiny piece of wood stuck behind the Disc so it's CoG is shifted backwards.
    Not too much that it starts scraping the coil when the pendulum reaches full amplitude, but you will notice that.

    Of course if you are not disturbed with the optics of a bent pendulum arm, your solution does the same and you might as well leave it like that.

    Do not change that 47F timing cap. It is designed for the maximum push at the right amplitude (velocity of the magnet when it passes the coil).
    Last edited by nomeat; 17-07-18 at 06:17 PM.
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