Thumbnail fan controller

[ElectronSurf]

I needed to add fan control capability for my 100W electronic load, It has to be small and easy to plug it in where the fan supply socket is.
So I came up with this design and thought I share with you, it's a simple and useful circuit to have.

I suggest to use a voltage reference to set the threshold voltage and also a flyback diode is needed, I think with a SMD MOSFET it can be even smaller than 25x18 mm.

Link to the simulator.



- Don't judge my soldering, I was debugging this board!

[mariush]

Or you could get a fan with PWM feature and a 6-8 pin micro can use ADC to read the resistor and adjust the pwm signal as needed.

Maybe even a 555 could be repurposed instead of a micro.

[shapirus]

What's the purpose of the upper op amp?

[ElectronSurf]

What's the purpose of the upper op amp?

Turning off the fan at a set temperature.