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Thread: Ten turn potentiometer

  1. #1
    Junior Member
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    Ten turn potentiometer

    I am making an audio device using teensy 3.2

    I was hoping to use ten turn pots to control some of the parameters,
    example:
    https://www.amazon.com/JANSANE-Poten...1357245&sr=8-3

    but when I change from standard pots the print monitor shows all sorts of unexpected behaviour.
    example:
    https://www.amazon.com/uxcell-Carbon...357326&sr=8-56

    I expected the ten turn pots to behave in the same way, but this is a surprise.
    The sketch works with the standard breadboard mount pots, but then things stop making sense with the ten turn pots substituted.
    Has anyone else come across this problem, and are there any suggestions to try so it will behave like other pots??

  2. #2
    Senior Member PaulStoffregen's Avatar
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    The best way to troubleshoot is with a multimeter. It's possible these pots have their pins in a different order. Or they could just be defective.

    The easiest way to check is first put the meter in ohms mode and look for the 2 pins which don't change resistance as you turn the knob. Then apply power to those pins and measure the DC voltage between GND and the other unused pin. If it isn't changing smoothly as you turn, then the pot is probably defective.

    After you get the hardware checked with a your multimeter, then connect to Teensy.

  3. #3
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    Thanks for the advice - I have tested a number of pots from the batch I bought and found that there were a few with issues.

    There were a number which showed print monitor readings which were always fluctuating, yet they would settle when read with the multimeter.

  4. #4
    Senior Member PaulStoffregen's Avatar
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    What is the pot's resistance?

    For higher values (over 25K), you might try adding a small ceramic capacitor between the analog pin and AGND. Capacitors between 470 pF to 0.1 uF work fine.

    Lower value pots, between 1K to 10K, give the best results.

  5. #5
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    I've just finished going through all the ten-turn pots I have available with the multimeter.

    Most of the ten-turn pots (x15) are 5k, these are the ones showing clear issues,
    from no variety (sticking at 5k) to sometimes jumping to unexpected values at the extremities (jumping to over 5k when it should be 0k).
    Others (x5) are 10k and 100k, no issues!

    Is your capacitor suggestion to smooth the behavior in the digital circuit?
    I'm going to see if I get similar results by putting them into the circuit/sketch and check what the print monitor output is showing.

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