Potentiometer In Parallel

Discussion in 'The Projects Forum' started by ilnar, Jun 18, 2012.

  1. ilnar

    Thread Starter New Member

    May 8, 2012
    16
    0
    here is my potentiometer and it's wiper is connected in parallel with 12k resistor.
    my wiper also serves as an output . so... how do i order this circuit to output 2.1 volts?
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,089
    3,027
    You need to separate the wiper from ground, and extract whatever voltage you want from the wiper.
     
  3. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    632
    Get the right value for the pot and you will have 2.1 volts when at 80%. The rest is left as an exercise.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,089
    3,027
    shortbus likes this.
  5. cork_ie

    Member

    Oct 8, 2011
    348
    58
    R= total pot resistance and assuming it is a linear potentiometer

    2.1 Volt is dropped across 20% of your pot,
    2.9 Volt across 12K & 80% of your pot in parallel.

    [0.2R= 2.1/I ] & [ 1/ (1/.8R + 1/12000)] = 2.9/I =>

    10.5/R = I = [2.9 x (1/.8R +1/12000)] = [2.9/.8R + 2.9/1200]

    = 3.625/R + 2.9/12000 =>

    6.875/R = 2.9/12000 =>

    R= (12000x 6.875)/2.9 = 28.448K

    Theoretical Pot size to get 2.1V at the wiper as in your drawing is 28.448K
    In practice you are unlikely to get one outside a standard value
     
    ilnar likes this.
  6. ilnar

    Thread Starter New Member

    May 8, 2012
    16
    0
    you are the GOD of Pots :))) thank you very much.
     
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