Pulse clock - unusual design and interface required

Discussion in 'Electric Horology' started by puffernutter, Aug 20, 2019.

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  1. puffernutter

    puffernutter Registered User

    Aug 13, 2015
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    Two years ago you were all very helpful and I now have (and had for 2 years) a Gents Pulsynetic clunking away in the hall and driving two slaves.

    On a bit of an impulse buy (sorry about the pun!) I purchased a double faced clock that looked as if it had a pulse type mechanism. It arrived last week and I finally got to play with it last night.

    It is German (at least the instructions for voltage setting are in German). It has no provenance (I was hoping it might be a railway clock, but nothing shows where it might have been used, or even its age). It appears to work off DC at either 2v, 24v or an unspecified voltage (I haven't experimented with that setting yet).

    Interestingly it needs the polarity reversing after each pulse to continue the movement. Two pulses of the same polarity and after the first movement it doesn't move again (until polarity is reversed),.

    So, has anybody heard or seen this type of clock/mechanism and is there any way I could interface it to the pulse from the Gents master clock. I could use a very high resistance relay, but my problem is figuring out how to reverse the polarity after each pulse.

    Cheers

    Peter
     
  2. rogerj

    rogerj Registered User

    Dec 21, 2014
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    retired broadcast engineer
    Cornwall
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    Hi..You didn't say if you know whether the slave need alternate seconds or 30 seconds. If you need a pulse every second the simplest way - and the method used by Hope-Jones - is to fit a very small magnet to the rod and a miniature reed relay to the case - placed at BDC.
    Either way, the rest of the solution is easy if you are OK with electronics at a hobbyest level. Basically you need to divide by 2 and use an H bridge. There is a circuit here: http://www.rogerj.co.uk/clock.htm scroll down until you find the alternate drive section...Is this enough to get you started ?.. Roger
     
  3. puffernutter

    puffernutter Registered User

    Aug 13, 2015
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    Sorry, my error and thanks for the reply. Polarity reversed pulsed every 30 seconds.

    Peter
     
  4. rogerj

    rogerj Registered User

    Dec 21, 2014
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    retired broadcast engineer
    Cornwall
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    Ok..that simplifies it a bit..I believe most European clocks ran off 24v - some were one pulse per minute I think. Before the days of solid state electronics, the alternating polarity pulse function was often done with relays (ugh:-() I imagine you would need three and one would need to be wired to latch. I can't offer a circuit however and haven't been able to find one by Googling..
    Due to the popularity of motor driven servos there are loads of H Bridges on eBay and are very cheap. You (or someone that could assist you) would need to find one with a suitable voltage rating.
    Perhaps someone else will pop up with a relay circuit if that's more "doable"
     
  5. ElectricTime

    ElectricTime Registered User
    NAWCC Business

    Sep 28, 2002
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    24VDC (and 12VDC) reverse polarity slave clocks are the European standard. Our standard 99B Tower Clock control provides +- 24VDC but only at a 1 PPM output.

    I believe the reverse polarity was used so a double bounce from a switch or relay contact would not advance the clock.
     
  6. rogerj

    rogerj Registered User

    Dec 21, 2014
    129
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    18
    retired broadcast engineer
    Cornwall
    Country Flag:
    Double stepping was indeed an advantage of reverse polarity dials but in general use they were also known for their silent operation and so were always used, for example, in Radio and TV studios.
     
  7. Snapper

    Snapper Registered User

    Nov 30, 2014
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    There is a UK producer of an electronic pulse generator which looks suitable for your clock. I have been using another of their generators for several years to drive the Gents GPO clock you see in my avatar.

    I would post a link but I think it is frowned upon to do so. Please send me a PM and I will give you the link. I have no connection with the supplier other than as a satisfied customer.
     

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