Temperature controlled Fan

I finally finished one of the outdoor Power Supply Boxes.  It contains 2x 350W SMPSs in it and will be situated in the garden.  The cabinet currently has a 12v computer fan to push air out of the box. Like all good computer fans this one makes a racket.

So I have set out to make a simple fan controller.

Design Requirement:

  • Operate of 12Volts
  • Keep fan OFF until needed
  • At 40degree ( this is my first guess) turn the fan ON slowly)
  • At 60degree and above make the fan go flat tack.
  • Between these two set point, the fan speed is to be set proportionally
  • Capable of driving 3 80mm or 120mm fans

the Temperature measurement can be super easy using a thermistor is a basic voltage divider. I have Atmel ATTiny 13 what have ADC and PWM functions.

Update 1:

I scraped the Thermistor idea and went straight toe Dalas DS18S20.  I have a number left over from a previous project.

Basic Schematic

Basic Schematic






 Now for the PCB Layout too

PWM Fan Controller PCB Design

PWM Fan Controller PCB Design


Partially Built Fan Controller

Partially Built Fan Controller

Lastly for the Code



Update:  Below are a several cooling options installed using this fan Controller.

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