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, ensure that the positive and negative switches are in the middle zero position, connect the DC power supply, ensure that the DC power supply voltage range is greater than 10V, less than 36V, and ensure that the output power of the power supply meets the needs of the motor. Do not connect the positive and negative terminals of the DC power supply in reverse, otherwise The governor may be damaged. 2. Connect the motor, the motor wire can be positive or negative. 3. Regulating switch, forward and reverse switch is used to control the direction of motor speed, when the switch is at the zero position, the motor stops. 4. Potentiometer knob. Adjusting the potentiometer knob can change the output duty ratio of the governor and the motor speed. size:73.5x45.5x27mm Material:ABS+pc colour:Green+black Package Contents: 1 * DC motor speed controller Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.