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Thread: Willing to look stupid to save one wire...

  1. #1

    Willing to look stupid to save one wire...

    I appreciate this is a really remedial question - and I thank you for your patience.

    I have a teensy 4.0 which I am just wiring up an on/off switch for. (Yep, long press connects on/off to gnd to turn off, short press connects on/off to gnd to turn back on).

    The momentary switch I am using also contains an LED indicator light, and an internal resistor (I don't know the resistance or forward drop).

    So, the switch has 4 lugs
    2 for the LED which connect to 3.3v and GND.
    2 for the button which connect to On/Off and GND.

    You can probably guess my question.

    Can I get away with just three wires if I bridge the LED- and the GND lug of the switch?
    Or does this end up applying LED voltage to the ON/OFF pin when the switch is connected?

    Now the I've typed that out - it sounds like a bad plan - but it would simplify the wiring to only use the end pins of the board.

    Many thanks

  2. #2
    Senior Member
    Join Date
    Jul 2020
    Posts
    472
    Should be fine. An LED + resistor is a load, not a short circuit, so it won't overcome ground which will be 0V
    whatever. I'd double check there's no internal connections with a multimeter though - its always worth checking
    pin-outs for things like switches just to be sure.

  3. #3
    Thank you very much for the prompt advice @MarkT

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