Very simple thermistor circuit- help needed..

Discussion in 'The Projects Forum' started by LaZyLuke, May 21, 2009.

  1. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
    Hi everyone.
    I'm back with a question about a very simple thermistor circuit project. I am trying to make a circuit that will turn on three 12V fans (computer power supply fans) when the temperature of the thermistor reaches over 70~80*C. I found some schematics:
    the dual fan setup looks very nice and i will be interesting in making something like that in the future, however for now I am trying to design something simple (like described above), the second schematic seems simple but is it the simplest i can use? (also there is no value of the temperature that this heat sensor will turn on at). Please any suggestions will be greatly appreciated. Thank you, Luke.
  2. hgmjr

    Retired Moderator

    Jan 28, 2005
    Of the two circuits to which you have provided links, the second may be your best approach as it does not use a microcontroller. The circuit using the ATTINY is a bit more involved than I would expect a beginner to tackle.

    The second circuit provides an adjustment in the form of a multiturn potentiometer so that you can calibrate the trip-point temperature. You can take a thermometer to get the temperature at which you want the fan to turn on. You can then adjust the potentiometer until the fan just turns on.