The full name of pulse width modulation is: Pulse Width Modulator, or PWM for short. Because of its special performance, it is often used as a lamp dimming in a DC loop or a DC motor speed control. This circuit is a motor controller made using the principle of pulse width modulation (PWM). Using this method to control the motor speed has two advantages: 1. It mainly changes the duty cycle of the output square wave to change the average on-time on the load from 0-100% to achieve the purpose of adjusting the brightness/speed of the load. The advantage of using pulse width modulation (PWM) to achieve dimming/speed regulation is that the energy of the power supply can be fully utilized and the efficiency of the circuit is high. For example: when the output is a 50% square wave, the power source energy consumed by the pulse width modulation (PWM) circuit is also 50%, that is, almost all energy is converted into load power output. When the common resistor step-down speed regulation is used, to make the load obtain 50% of the maximum output power of the power supply, the power supply must provide more than 71% of the output power, of which 21% is consumed by the voltage drop and heat consumption of the resistor. 2. The pulse width modulation (PWM) method can make the load get the full power supply voltage when working, which is beneficial to overcome the internal coil resistance of the motor and make the motor generate greater torque. The products are equipped with external speed control knobs. Forward and reverse control, (forward, stop, reverse) products are equipped with forward and reverse switches. The chip is used, and the filter capacitor is a monolithic capacitor, the circuit is stable and reliable. The heat sink area used by this speed governor is more than twice that of similar products on the market, which can meet the needs of 150W motors. 1. Connect the power cord, that the positive and negative switches