Control circuit for a 1925 3 floor dumbwaiter

Discussion in 'The Projects Forum' started by rabutera, Oct 25, 2011.

  1. rabutera

    Thread Starter New Member

    Sep 26, 2011
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    I have been working on a old electromechanical dumbwaiter that was installed around 1925 using a 120 V control line for a three phase 204V motor and have everything working but the at floor indicator ckt. The one on the 1st floor works but the upper floors do not. The bulbs are ok but no power is there. I have been looking for a wiring diagram used in that time period. Would appreciate any help available.
     
  2. chrisw1990

    Active Member

    Oct 22, 2011
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    you could try checking the continuity of the wires?
    could be the sensor? or whatever it uses to say "hi im here" so to speak?
     
  3. Georacer

    Moderator

    Nov 25, 2009
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    A relative question: How do you check a 10m wire embedded in the wall for continuity?

    Is there a more clever option than getting another 10m wire to connect your multimeter?
     
  4. chrisw1990

    Active Member

    Oct 22, 2011
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  5. crutschow

    Expert

    Mar 14, 2008
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    To connect continuity you just measure the resistance between the two wires going to the bulb. You should measure the bulb resistance, which would be small. You don't really need to know which wire might be broken if there is no continuity. Replacing a wire pair is basically just as easy as replacing a single wire.
     
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  6. Georacer

    Moderator

    Nov 25, 2009
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    That could work, unless your load isn't a bulb but some sensor or switch...

    In which case you could short the sensor and do what you said.

    Hey! I 'm answering my own questions here! Way to go!
     
  7. Adjuster

    Well-Known Member

    Dec 26, 2010
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    There are various testers such as the old-fashioned (and maybe just a little hazardous) neon screwdriver, which rely on the operator holding one end of the contraption, so supplying a sort of ground. If the wire is connected to a sufficiently high voltage supply (referenced to Earth), the detector should give an indication if the wire is unbroken. Unfortunately, the indications can be a bit ambiguous, as the contraption has to have a very high impedance to work at all without frying the operator, who himself may present a varying impedance to ground.
     
  8. Georacer

    Moderator

    Nov 25, 2009
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    High voltage isn't my main concern. I have often needed to lay down thin signal wire over a long distance.
    When troubleshooting, I can never reject a possible wire failure. What's the plan in that case?
     
  9. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I find myself in this situation all the time. usually wires going through conduit. in that case, if I can see the other end of the conduit where the wire comes out, I just tug on the wire and see which one moves. if I can't see, then I put a resistor (for example 100ohm) from the wire in question to ground. then I go test all the wires to ground until I find the one with 100ohms. This worked well for me on oil rigs, where a wire may originate in a room 2 levels below the drill floor, and end up in the top of the derrick (tower). Especially if I were sorting more than one wire; label say 20 wires 1-20 and assign them different resistor values, then go to the other side (wherever that may be) and start testing, and label them 1-20 according to the resistances you read. I also have a "fox 'n hound" (telecom tonal tracer) which works well, when it works. the problem with it, is that I'm usually dealing with control systems full of relays & all of the wires are somewhat connected through something, so they all ring.
     
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