I am going to control a fan using PWM signal. PWM is generated by a 555 IC. The duty cycle rate of the PWM is controlled by a PTC thermistor. And an NTC thermistor decides when to turn on and off the fan by generating a digital signal by using a comparator.

How do I interface the comparator output and the 555? I feel like it will be done through the "control" pin of the 555, but I can't find how to.

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Note: The resistor and capacitor values have not calculated yet. Please ignore those all 100k\$\Omega\$ values.


1 Answer 1


You can add a pull-up resistor to the /reset input, and drive that with the output of your open-collector comparator.

Pulling it low will drive the 555 output low.

  • 1
    \$\begingroup\$ Note that when /RESET is low, OUT will also be low. \$\endgroup\$ Apr 28, 2021 at 14:32

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