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Need to light different LEDs when polarity is reversed

Discussion in 'LEDs and Optoelectronics' started by xpnctoc, Jun 2, 2017.

  1. xpnctoc

    xpnctoc

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    Jun 2, 2017
    Hi, kind of a newbie here. I'm making a control panel for a hobby project. The panel includes a DPDT switch wired to act as a polarity reverser (to reverse directions on a motor). I understand how to do that, but I also want to add 2 LEDs on the control panel which light up to indicate which "on" position the switch is in. I can't figure this part out since ultimately there is only one circuit that comes out of the switch. And, of course, there is the problem that LEDs are polarity sensitive. So is it even possible to do this? Is there some kind of component that switches between 2 outputs based on the polarity of the input? Or can someone provide a circuit diagram that could accomplish this? Thanks!
     
  2. duke37

    duke37

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    718
    Jan 9, 2011
    You can use a diode in series with the led to allow it to light if the polarity is correct.
    You can use a pair of leds in reverse parallel, one will light with one polarity and the other will light when the polarity is reversed. Each led protects the other from excess reverse voltage.
     
  3. xpnctoc

    xpnctoc

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    Jun 2, 2017
    Awesome! Thanks!
     
  4. AnalogKid

    AnalogKid

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    Jun 10, 2015
    What is the voltage across the motor?
     
  5. xpnctoc

    xpnctoc

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    Jun 2, 2017
    12VDC
     
  6. AnalogKid

    AnalogKid

    2,297
    646
    Jun 10, 2015
    Standard small red and green LEDs average around 2 V forward voltage drop. A 1 K resistor will deliver 10 mA. 470 ohms will deliver 21 mA, a safe max value.

    ak
     
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