• Temperature Regulating Fan System





    PC Fans come in 3 main types, these are:
    •  2 Pin fans - 1 pin for power and 1 for ground. The fan is either on and off.
    •  3 Pin fans. Three pin fans have 1 pin for power, 1 for ground and a feedback tacho pin. The feedback can be used to calculate the speed of which the fan is spinning.
    •  4 pin fans. These fans have the same features as the 3 pin fans and a 4th pin used for PWM, allowing you to control the speed of which it spins.
    In this project I use PWM to control the speed of which a 3 pin fan spins. Ive used the tacho pin to work out if the fan gets jammed and an alarm circuit sounds a siren if its not turning when it should be.
    The fan is turned on and off automatically using a temperature sensing subsystem. A variable resistor has been used to allow the user to control the temperature of which it turns on.

    The entire circuit can be turned on and off with a SR Latch.

    Ive used an arduino nano to work out when the fan is turning. Using the PulseIn() command the arduino returns the width of the pulse in milliseconds. In the future I plan to add some 7 segment displays its frequency.