I have been tasked with retrofitting some small fans to an old car, to help move heated air into the footwells. Being a computer-type, I immediately bought some standard computer cooling fans.
The fans are DC, and the only rating information is 8-12V.
It was my hope that a basic potential divider with knobbed potentiometer would provide a voltage-based fan control:
simulate this circuit – Schematic created using CircuitLab
I only ask because any search for "Fan Control" leads to pulse-width-modulation. Is it possible to control fan speed using this basic circuit above?
Best Answer
PWM is used because it wastes much less heat than "linear" methods like that shown in your schematic. A TO-92 voltage regulator and a DIL8 microcontroller is all you need to read the voltage from a 10kohm pot and then generate a PWM signal to put through a power MOSFET on the low side of the fans. You could even substitute a 555 and associated passives, but the MCU will give you better control.
simulate this circuit – Schematic created using CircuitLab