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Size of Potentiometer

Discussion in 'Electronic Design' started by [email protected], Aug 28, 2007.

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  1. Guest

    What size of potentiometer do I need to use if I'm wanting to take a
    9V battery down to anywhere from 3.5V back up to 9V?
     
  2. Joel Kolstad

    Joel Kolstad Guest

    How much current do you need? What are you using that output for? This
    question is pretty much impossible to answer without more information. (It's
    underconstrained -- any potentiometer can adjust 9V all the way from 0V to 9V,
    but using, e.g., a 1 ohm potentiometer will just kill your battery in a few
    seconds. :) )
     
  3. Guest

    Oh, I see. I'm regulating one led for brightness and eventually a
    series of them.
     
  4. default

    default Guest

    Small adjustable standard or low dropout three terminal regulator
    would work well. With a drop of 2.5 volts per led you can't put many
    in series (conserves more battery power)

    Depends on how long the battery has to last etc..

    Adjustable current source may work better or drop less voltage - or
    current mirrors to work several series strings.
     
  5. GregS

    GregS Guest

    You cannot precicsly control the voltage, but all you need to do is control
    current. The potentiometer can be series wired, along with a limiting resistor
    for the max brightness, also in series. You ned to know the current range of
    the LED, and the voltages needed for series strings. You can only use a
    small number of series LED's before you run out of voltage. A 2K pot with
    a 270 ohm resistor would get you going.

    greg
     
  6. Guest

    Thank you everybody!
     
  7. Tam/WB2TT

    Tam/WB2TT Guest

    This may not be obvious to the OP, but I think what you are saying is to use
    the pot as a variable resistor, with connections to 2 of the terminals only.
    Using it as a pot wastes power.

    Tam
     
  8. Robert Baer

    Robert Baer Guest

    No more than two inches in diameter...
     
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