Help understanding fan controller circuit

Discussion in 'General Electronics Chat' started by bitrex, Dec 28, 2009.

  1. bitrex

    Thread Starter Member

    Dec 13, 2009
    79
    4
    I'm looking at the circuit at http://sound.westhost.com/project42.htm. I understand that when the op amp output goes low, the transistor switches on the fan, and that it's controlled by the decrease in voltage drop across the diodes as they heat up, but I'm unclear as to how the op amp in that configuration works to detect the voltage change. Any help would be appreciated!
     
  2. zhgart

    New Member

    Dec 28, 2009
    19
    1
    the op works at invetion mode. when the dirde heated up, the voltage on it will change (up or down depend on the feature of diode) r1 r2 pffer a bias current of diode. the diode voltage will be amp about 100times. that's all.
     
  3. bitrex

    Thread Starter Member

    Dec 13, 2009
    79
    4
    I see it now. Thank you!
     
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