PMW control by temperature

Discussion in 'General Electronics Chat' started by mdcarvalho, Sep 14, 2008.

  1. mdcarvalho

    Thread Starter New Member

    Jun 13, 2008
    2
    0
    Hi new here if I don't know how to procedure I do apolidise
    I would like to know if anybody could help me how could I control the duty cycle of a pmw modulator (555 Ic for instance) by temperature with a ntc
    Thermistor
    thank you
    Marcus
    [​IMG] [​IMG]
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    There are a number of example circuits on the web such as this one.

    I bit of googling can uncover quite a few 555 based PWM controllers with temperature control.

    Of course, some alterations will be needed to get the functionality consistent with your application.

    hgmjr
     
  3. mdcarvalho

    Thread Starter New Member

    Jun 13, 2008
    2
    0
    yes I have seen those circuits on the net as a matter of fact the one I am using is similar to the one you point me to I was think of a circuit that would uses two transistor (NPN & PNP) instead of those two diodes and the 100 kΩ pot please see atachment . Than control the base of the two transistor with the thermistor that way I would not change the frequency. only the duty cycle
    but I don't have the enough knoledge to design the circuit
    Thank you for your interest I really appreciate
    Marcus
     
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