Project is developed by David Cook, who decided to add two additional fans to its computer case that needs to be hidden in closed space where air doesn’t circulate very well.
Fan controller reads thermistor voltage drop via Attiny45 ADC channel and calculates environment temperature by using lookup table. Fans are controlled through two MOSFET transistors that are powered from 12V. As fan controller is inside computer case there is no need for additional power supply – it uses computer power supply. In order to avoid fans turning on and off at threshold level there is a 5 volt hysteresis programmed.
Author also has developed a professional version of dual fan controller with has 4x seven segment LED indication, three status LEDs, speaker for alarm. Professional version has many features like temperature reading, power voltage reading, motor current reading, screen saver, backing up settings in EEPROM memory. Check out the site for more details.