Automatic temperature control and speed regulating device for electric fans

The automatic temperature control speed regulator of electric fans can automatically adjust the speed of electric fans according to the temperature changes. The circuit can be adjusted and can also be used to control other electrical equipment.
1. Circuit working principle
The circuit principle is shown in the figure below.
The IC in the figure is a 555 time base circuit, which forms a multivibrator with components such as R2, R3 and C2, and can send a rectangular wave signal with adjustable duty cycle. When the temperature changes, the resistance of the thermistor changes, which changes the duty cycle of the square wave output by the multivibrator, adjusts the conduction angle of the bidirectional thyristor VT, thereby changing the voltage at both ends of the fan electrode and automatically adjusting the speed of the electric fan.
2. Component selection
The integrated circuit IC uses the NE555 time base circuit, and models such as LM555 and TLC555 can also be used. VT is a bidirectional thyristor, its withstand voltage should be above 400V, and the rated current should be reasonably selected according to the capacity of the electric fan to be controlled. Resistors R1~R5 can be ordinary 1/8 or 1/4W carbon film resistors; Rt is a negative temperature coefficient thermistor, which can be a thermistor with a resistance of about 10KΩ at room temperature. Capacitor C1 uses an ordinary aluminum electrolytic capacitor; capacitors C2 and C3 use polyester capacitors. VD is a voltage-stabilizing diode with a voltage value of 9.1V.

3. Production and debugging methods You
can make your own printed circuit board or use a universal printed circuit board. After the circuit is installed, you can manually change the temperature of the thermistor Rt and observe the speed of the fan motor. If the temperature control effect is not ideal, you can appropriately adjust the resistance value or temperature range of the thermistor.