Pot Resistance Question

Discussion in 'General Electronics Chat' started by Joster, Sep 30, 2013.

  1. Joster

    Thread Starter Member

    Jun 12, 2013
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    0
    Hi All,

    I'm analyzing a circuit that has a pot. There are three pins. The resistance between the outer pins is fixed. Is the resistance between the outer pins and the wiper in parallel ?

    Hopefully this pic helps to show what my question is...

    Thanks!

    -Joe
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,421
    3,355
    What??????
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,507
    2,367
    Single resistance with a 'slider'.
    Also the resistance read by the slider WRT to either end can be logarithmic or linear, depending on the application.
    Max.
     
  4. crutschow

    Expert

    Mar 14, 2008
    12,988
    3,226
    A pot is a single resistor with a wiper that makes electrical contact along that resistance from one end to the other, as determined by the wiper position. The resistance from the wiper to either end of the pot is thus a percentage of the total pot resistance. For example if the wiper is 25% from the bottom of a 1kΩ pot then the resistance measured from the bottom to the wiper would be 250Ω and the resistance from the top to the wiper would be 750Ω. If you measured from both ends in parallel to the wiper, the resistance would be the parallel value of those two resistances or 187.5Ω.
     
  5. Veracohr

    Well-Known Member

    Jan 3, 2011
    549
    75
    Only if the outer pins are connected to the same point will the two resistance sections be in parallel. They usually aren't.
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,987
    3,733
    A potentiometer is technically a 'voltage divider'. Think of it as two resistors and the wiper is a connection to that midpoint.

    You can connect a potentiometer like a rheostat, and make it a current limiter (or variable resistor) by connecting the wiper to one of the other two pins.
     
  7. Austin Clark

    Member

    Dec 28, 2011
    409
    44
    Yes, that is correct.
    You should have labeled your pins and made the resistors horizontal though, for clarity.
    Using your picture on the right, as you turn the pot, the sum of the resistors remains the same, but the resistance at either resistor will vary back and forth. At either extreme all the resistance will be on one resistor while the other will act close to a short. Typically this is used to divide the voltage between the two outside terminals down and output it on the center terminal.
     
  8. Joster

    Thread Starter Member

    Jun 12, 2013
    95
    0
    Wow! Thanks for all the help!! I got it now :)
     
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