Potentiometer

Discussion in 'The Projects Forum' started by tami, Jan 22, 2013.

  1. tami

    Thread Starter New Member

    Nov 27, 2012
    1
    0
    Hi everyone,
    I am working with potentiometer.I want to connect it to FEZ Mini's analog Input pin(which is 3.3V max) to convert analog into digital. That analog input pin won't take voltage more then 3.3volts or it will blow the microcontroller up, so I want my potentiometer to connect to 3.3V instead of 5volts, which I am not sure about...? So my question is - Can I connect my 10k linear potentiometer to 3.3V instead of 5V to make it work with Fez mini's analgInput pin?
     
  2. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    yup, no problem...
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,087
    3,026
    Hard to follow without a drawing, but you'll want an external fixed resistor also, for insurance against the pot being turned all the way to one end, to zero ohms. You think it won't happen, but it will.

    I think you just need a voltage divider, so that a 5v input is scaled down to 3.3V. You may not even need a pot.
     
  4. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
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    As long as it is hooked up as it is here there should be no problem. The center tap will be what is connected to your ADC input and the two fixed points to your supplies...

    If it's connected properly, the supply will always see a 10kΩ resistance, regardless of where the wiper is...
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,087
    3,026
    Yes, but the ADC he is protecting could end up seeing 5V at one end of the wiper travel.
     
  6. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    Vcc = 3.3V
     
  7. wayneh

    Expert

    Sep 9, 2010
    12,087
    3,026
    Huh, guess I totally missed the point of the question. :confused: Wouldn't be the first time.

    I thought he wanted to use the pot to protect the input against ever seeing 5v.
     
  8. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    Ah, yes, then that would be a valid point!

    To be honest, I had to go back and re-read it to be sure ;)
     
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