Find out what potentiometer I need

Discussion in 'General Electronics Chat' started by XOIIO, Mar 4, 2013.

  1. XOIIO

    Thread Starter Member

    Mar 1, 2013
    Hey all, I'm actually a bit new to potentiometers, but I have an LCD display that measures voltage coming soon, so I figured it's time to make a variable power supply. Thing is, I'm not sure how to find out what potentiometer I need. I need one that can bring 12 volts all the way down to 0 (well, 10 since thats all the display can handle). Anyways, what value/range (if that's right) potentiometer will I need. Also, what's an easy way to figure it out for future refference?
  2. bug13

    Well-Known Member

    Feb 13, 2012
    from what I understand, if you want to make a simple variable power supply, you need a lm317 (page 7), but if you just want to test your LCD module which measures voltage, all most all potentiometers will do.
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    Put a 10k or larger potentiometer across a 12V supply. The full value is typically the outside pins of the potentiometer. Connect one end to + and one end to GND.

    Connect the wiper (typically middle pin) of the potentiometer to the V+ input of the Voltmeter
    Connect the Ground of the Power supply to the GND of the Voltmeter

    The pot wiper then acts as a tap on a voltage divider. When at one extreme, the wiper will be at GND, and at the other extreme, the wiper will be at 12V. In between, the voltage will be in between those two extremes.

    This is useful for getting a voltage to measure, NOT for powering circuits. Typical potentiometers cannot carry much current. This is the reason a 10k pot is suggested, so only 1.2mA is drawn from the supply. If more is drawn from the wiper, such as powering a circuit, the voltage will drop due to the amount of resistance.

    If you need a variable supply for powering circuits, you'll need a regulator like the LM317, which can adjust from 1.25V to Vsupply - ~2V, that regulator can supply up to about an amp of current reliably, provided the input source can as well.
    bug13 likes this.
  4. bug13

    Well-Known Member

    Feb 13, 2012
    Opps, didn't think about the value of the potentiometer, thanks for correcting me :)