This is a design for fan controller regulator circuit. This circuit will automatically control the speed of the fan according to the temperature in surrounding the fan. The circuit is use two thermistors (R1 and R2) are used to sense the temperature. This is the figure of the circuit.
Operation of the circuit is done, if the potentiometer is replaced by the thermistors. When the temperature is increasing the resistance of NTC thermistor (R1) decreases and at the same time the resistance of PTC thermistor (R2) increases. At the same time, rate of change of the resistance will be different for R1 and R2.This action is similar to a potentiometer used in a conventional Triac based fan regulator. When the resistance is varied the firing angle of the triac changes and so do the speed of the fan. L1 can be a 70uH inductor. The capacitor C1 and C2 must be rated at least 200V and C3 must be rated at least 600V. The triac BT136 can safely handle up to 4A load current. The two thermistors must be mounted as close as possible. This circuit is powered using AC voltage.
Operation of the circuit is done, if the potentiometer is replaced by the thermistors. When the temperature is increasing the resistance of NTC thermistor (R1) decreases and at the same time the resistance of PTC thermistor (R2) increases. At the same time, rate of change of the resistance will be different for R1 and R2.This action is similar to a potentiometer used in a conventional Triac based fan regulator. When the resistance is varied the firing angle of the triac changes and so do the speed of the fan. L1 can be a 70uH inductor. The capacitor C1 and C2 must be rated at least 200V and C3 must be rated at least 600V. The triac BT136 can safely handle up to 4A load current. The two thermistors must be mounted as close as possible. This circuit is powered using AC voltage.
