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Two potentiometers on a pulse width modulator

Discussion in 'General Electronics Discussion' started by Madsalts, Jul 1, 2015.

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  1. Madsalts

    Madsalts

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    Sep 25, 2014
    I have a pulse width modulator with a dual-ganged potentiometer. I've seen other PWMs with two potentiometers, rather than the single dual-ganged. What two parameters are controlled by the potentiometers? I'm using mine on a trolling motor. If I were to decouple the parameters by using two pots instead of one, what would the effect be? Would this be desirable?
    This isn't a situation where I'd be finding one ideal pulse width and sticking to it. I'd be adjusting this to speed/slow the motor. Thanks.
     
  2. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    My first thoughts are to control the mark and the space durations, but not sure without a circuit diagram. Do you have a circuit diagram or can you link to a similar one.
    Adam
     
  3. signalman72

    signalman72

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    Jan 26, 2014
    Well, it appears that one set is being used as an adjustable voltage divider and the other as an adjustable resister.
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    A standard PWM doesn't require two potentiometers - unless you want to control mark and space independently (Adam's post #2), but in this case you'd like to have independent potentiometers, not a coupled one.
    .
    Are you sure the second part of this potentiometer is a potentiometer? There are only 2 wires coming from this part. It could be a switch to completely turn-off the controller in the lowest setting.
     
  5. signalman72

    signalman72

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    Jan 26, 2014
    Ah, that makes more sense! Id nearly forgotten about those switch/pot combos. They were very popular on those little pocket "transistor radios" when I was a kid.
     
  6. poor mystic

    poor mystic

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    Apr 8, 2011
    [QUOTE="Are you sure the second part of this potentiometer is a potentiometer? There are only 2 wires coming from this part. It could be a switch to completely turn-off the controller in the lowest setting.[/QUOTE]

    Harald's conjectural switch certainly is in the power supply.
     
  7. Madsalts

    Madsalts

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    Sep 25, 2014
    Thanks for the replies. I'll have to mess around with this. I might decouple the two, since it might be useful to have a killswitch. Furthermore, I can actually find a waterproof pot, whereas I can't find a waterproof dual-gang pot or a waterproof pot/switch combo.
     
  8. Minder

    Minder

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    Apr 24, 2015
    I agree, if you look close at the pot rear side, there only appears to be two outer terminals. (switch).
    M.
     
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