This is DC 12V motor speed motor controller circuit. such as SCR DC motor speed control circuit using IC-CMOS. You can adjust the rotation speed of the spindle motor from 5-60 cycles per minute.
The circuit work, the IC1- (CD4081) is nand the type of gate IC. Accepts the bridge diode voltage BD1. But there is no filter to smooth the current. The other on pin 2. The VR1, C1 and R1 is a phase change or delay time, the voltage from pin 3 to the triggers pin the SCR1 gate to work. Or drive the motor, turning it. Motor speed, can be achieved by adjusting VR1.
The input pin of the IC1 power supply 14 is filtered to smooth the current through D2 and C2. The D1 prevents engine noise. and D3 is the reverse voltage protection of the motors. This may cause damage to the circuit. If the circuit is used with a motor that consumes more energy. The heat sink must be connected to BD1, D1 and SCR1, because they heat up. It may cause damage to the equipment.