Motor electronic speed regulation circuit

This circuit is simple and easy to make, and can be used to control the speed of small single-phase AC motors.

After the 220V AC voltage is stepped down by C3, rectified by VD3, filtered by C1 and stabilized by VS, it provides +12V DC working voltage for the IC. After the ultra-low frequency oscillator is powered on, it outputs an ultra-low frequency pulse signal with a frequency of about 1Hz from pin 3 of the IC. This pulse signal is added to the control end (positive end) of the solid-state relay KN, and the VTH is controlled by controlling the on and off of KN (when the pulse signal is a positive pulse, KN is on; when the pulse signal is a negative pulse, KN is off) conduction angle.

Adjusting the resistance of RP can change the duty cycle of the IC's pin 3 output pulse signal. The greater the duty cycle of the pulse signal, the longer the conduction time of VTH per unit time, the higher the operating voltage of the motor M and the faster the operating speed.