Fan frequency speed regulation circuit

The circuit is shown in Figure 1a. In the circuit, NE555 is connected as a square wave generator with adjustable duty cycle. The duty cycle can be changed by adjusting RW. During the period when the 3rd pin of NE555 outputs high level, the primary of the zero-crossing on-off optocoupler MOC3061 obtains about 10mA forward working current, which makes the internal GaSi infrared emitting diode emit infrared light, and turns on the photosensitive bidirectional switch in the zero-crossing detector when the mains passes zero, turning on the power supply of the electric fan motor, and the fan runs to deliver air. During the period when the 3rd pin of NE555 outputs low level, the bidirectional switch is turned off and the fan stops.

MOC3061 itself has a certain driving capability, and the operation of the electric fan motor can be controlled directly by using the internal bidirectional switch of MOC3061 without adding power driving components. RW is the duty cycle adjustment potentiometer, that is, the adjustment of the air supply time of the electric fan per unit time (the data of this circuit is about 20 seconds). Changing the value of C2 or the value of RW can change the control cycle.

The circuit in Figure 1b is a typical power expansion circuit of MOC3061. When controlling a motor with a large power, you should consider using a power expansion circuit. When making it, you can refer to the parameters in the figure to select the device. Since the power supply adopts a capacitor voltage drop method, please pay attention to safety when making it yourself, and the human body cannot directly touch the circuit board.