The project described here is a switch mode fan speed controller for use with brushed or brushless DC motors. Temperature-proportional speed control is accomplished using pulse width modulation (PWM). 10K Ohms NTC is used to sense the temperature. The project is built using TC648 chip and configured with auto-shutdown mode. In Auto-Shutdown mode, fan operation is automatically suspended when the measured temperature is lower than 25 degrees centigrade. The fan is automatically restarted and proportional speed control is restored when the temperature exceeds 25 degrees centigrade. An integrated Start-Up Timer ensures reliable motor start-up at turn-on, or when coming out of Shutdown mode. MOSFET Q1 is provided to drive the Fan up to 3A of load. A few fans require a PWM signal to work. Use gate of MOSFET to take out the direct PWM signal.