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Thread: is it ok to wire it that way?

  1. #1
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    is it ok to wire it that way?

    hi,

    when you wire some potentiometers, is it ok to wire the GND/3.3V-pins from each to each potentiometer?

    like this:
    Click image for larger version. 

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    my problem is, that I have wired it that way and now when I connect the pot-outputs or the GND/3.3V-lanes to my "main-pcb" (where the teensy is on), the teensy stops working and the serial-port is gone.. I then have to re-connect the teensy (which only sometimes works).

    or maybe, could it be that the wires used for the outputs are too thin? .. i don't know, but I have ordered me this here:
    https://www.amazon.de/gp/product/B07...?ie=UTF8&psc=1
    and the inner wires are really thin.. reaaaaally thin.

  2. #2
    Senior Member PaulStoffregen's Avatar
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    Usually this sort of wiring is perfectly fine. If the pots are ordinary resistance like 10K, they're much, much higher than the resistance of even very thin wires.

    my problem is, that I have wired it that way and now when I connect the pot-outputs or the GND/3.3V-lanes to my "main-pcb" (where the teensy is on), the teensy stops working and the serial-port is gone.. I then have to re-connect the teensy (which only sometimes works).
    That sounds like a mistake in the wiring, probably mistakenly connecting GND or 3.3V to the center pin of the pot.

  3. #3
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    Quote Originally Posted by PaulStoffregen View Post
    That sounds like a mistake in the wiring, probably mistakenly connecting GND or 3.3V to the center pin of the pot.
    I have checked all connections with a multimeter, everything fine here.

  4. #4
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    Paul's original statement stands that something is drawing to much current and shutting down the Teensy and it would most logically be in the thing that you are connecting.

    Suggested steps are:
    Test your3.3V/gnd connections for resistance, should measure at the size of the puts divided by the number of pots (because they are in parallel).
    Then with meter connected adjust each pot in turn through the full range. Nothing should change in the power/return resistance

    If at any point you measure less than 50 ohms or so that is why things go wrong when you connect the Teensy. If these are the normal 10K pots you should never see less than 1.2K

    If nothing is coming to light there connect back to the teensy (or better a bench power supply limited to 0.1 Amps) and adjust the pots and watch for the 3.3V rail to fall off or otherwise glitch.

    Edit: Do not read German well enough to find the technical specs (if even there given this is Amazon) on that linked wiring but if it is standard ribbon cable intended for 0.1 headers it should be capable of carrying an Amp or two just fine. This circuit should never have more than .003 Amps flowing if wired correctly so plenty of head room.

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