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Ideas for my project

  1. Feb 17, 2009 #1
    I have recently in work been given a sort of mini project

    I have been handed what must be about 60 years old or so world time clock, this is one of those arrangements where you have an arrangement of small clocks in a cabinet with each clock representing the time of a different city in the world.

    The problem is however a lot of the wiring has been butchered and I don't even know what power supply this ran off, the cable last found in it was a simple two core cable and i'd expect the voltage to be either 24v DC or 240 AC but I don't know for sure as of yet.

    The biggest problem is though whatever generated the pulse for all these clocks to run is not there, one the back of each of the clocks there is a small mechanism connected to a solenoid, when the coil is energized once it engages the mechanism and the minute arm moves half a minute, i.e. i need a pulse to be generated once every 30 seconds but i'm not sure how to do it.

    I could use a PLC I suppose but there are 1 amp fuses all over the show with wiring connected to the clocks and on the back of the fuses there are snippets of multicore cable in the terminals, i'm assuming whatever was connected to these generated a pulse.

    Any ideas?
  2. jcsd
  3. Feb 17, 2009 #2
    could use a faster pulse, say 1hz and use a counting ic all u need do is hook up an AND gate on the relevant outputs...

    basically, a finely tuned astable should do the job, but it will be hard to make something that accurate...

    a microcontroller could do the job too, depending on the accuracy of ur programming...

    googling turned up this: http://www.dutchforce.com/~eforum/index.php?showtopic=22789
    mention of a 4060 from TI and a circuit diagram :P
  4. Feb 17, 2009 #3
    interesting and potentially useful idea, however the frequency of the pulse cannot be changed because of the way the coil mechanism works, as the coil pushes a small ratcheted gear, turning the clock arm half a minute, which I should have mentioned earlier.

    I was thinking of setting up a PLC and jus linking the common across all clocks from the output, but to throw another spanner in the works I suspect the voltage for the system is 240v.

    This is where my application of useful knowledge wears thin, Could I use the output of the PLC to activate a relay for say a 240V circuit? would a relay using such a small voltage be able to pull in a 240V supply?
  5. Feb 17, 2009 #4
    sorry, my knowledge of PLcs is low

    but yea a relay could be used fine... any logic output would be ok...

    just had a thought that u could use a voltage to pulse ic of some kinda and finely tune the input voltage....

    im not suggesting changing the input pulse to the clock, but u can use a binary counter or something to get reduce the frequency..
  6. Feb 17, 2009 #5
    btw make sure ur relay is rated for 240V and u use a transistor to switch it. and dont forget the feedback diode thing...
  7. Feb 17, 2009 #6

    What do you mean by using a voltage to pulse an ic (i'm assuming that stands for input controller?) I'm an apprentice so you'll have to forgive my lack of knowledge
  8. Feb 17, 2009 #7
  9. Feb 17, 2009 #8
    You suggested a pulse width modulator an engineer at work was discussing with me how they work etc. however i've just been lookign on the internet and I don't really understand how they work or what they do.

    I think i'm destined to be a failed electrical engineer, the more I see the less I know!
  10. Feb 17, 2009 #9


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    (It's been attributed to Socrates, but I can't find a definitive source.)

    Since I have a loving of them, might I suggest an RTC (Real-Time Clock) with temperature calibration, and a once per second pulse output? While it won't save you from having to get a (quality) 32.768 kHz (2^15) crystal, it would save you from having to construct an oscillator driver, and a counter. Since it's not really doing much else, you can also do this with a microprocessor / microcontroller and fine tune your output pulse.
  11. Feb 17, 2009 #10


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    Do you have any information on this old clock that could be searched for? Like who made it so you could see how it worked originally?
  12. Feb 17, 2009 #11
    what is the goal, again? to refurbish the clock? reverse engineering?
  13. Feb 17, 2009 #12
    good plan... rtc should do the job, didnt know of any with a simple 1hz output, only an I2C bus (although i havent ever personally wired one up...)

    also, can u see any power conversion on the 240v AC anywhere? or does it go straight into the clocks, im just thinking for possibly powering your own circuit....

    oh and a pulse width modulator is simple, the higher the voltage you input, the longer the gap between pulses that come out of it (or visa versa :P) im guessing that any IC u got would have a calculation on the datasheet for the time gap from the voltage, you could stick in ur required time value, and work out what voltage u need :)
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