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Thread: global questions on potentiometers

  1. #1
    Senior Member
    Join Date
    Nov 2016

    global questions on potentiometers


    - can someone explain the difference between common potentiometers with 4 pins, and thos with 4 pins?

    - I need 38 potentiometers in my project, and I am looking for good (reliable) ones, which are both .. pcb-mount, and also panel-mount.. those seem to be "a bit" more costly.. can someone recommend good models/manufacturers and maybe a source where to get them?... I mostly looked on ebay/amazon/alibaba/aliexpress for now.

    - i use linear 100K pots.. a time ago, in a other thread, someone wrote that the resistors used, affect the rest of the circiut (which is one of the reasons for decoupling) .. should I use smaller R on the pots?

  2. #2
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012
    For Teensy 3.x analog inputs, usually 5K or 10K pots are best.

    Normally pots have 3 pins.

    Maybe you could be more specific, like links to datasheets or product pages for these ones for a 4th pin? Maybe others here will know (or guess) which products you mean, but I have no idea. All the ones I normally use have 3 pins.

  3. #3
    Senior Member
    Join Date
    Nov 2016
    Hi Paul,


    I mean for example this B10K18.. sorry i can't find the datasheet.
    Click image for larger version. 

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    .. i experimented a bit and found out, that the right outer pin seems to be a dummy.. when i look from left and connect my 3 pins as usually, it works .. but it gives me raw-values of 0-682 that normal?

  4. #4
    Senior Member
    Join Date
    Apr 2017
    In my admitedly limited experience most 4 pin potentiometers have what's called a center tap on that fourth pin that I believe allows you to change the resistance of the pot for some reason or another. Although they might be from the same series but lack the center tap so it may be just a dummy leg, as far as normal my experience with 4 legged pots is somewhat mixed. The one I have appears to not use or have the center tap, so I wire it up like normal, values seem to be normal, everythings good, however when I connected other pots that were only 3 pin to the same controller suddenly it lost most of it's values. You would turn the knob and once you turned it past about 70% then the value would change from 0 and finally start rising like you would expect it to, really strange behavior that I could never figure out.

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