The full name of width modulation is: Width Modulator, or PWM for short. Because of 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 width modulation (PWM). Using this to control the motor speed has two advantages: 1. It mainly changes the duty cycle of the output 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 width modulation (PWM) to achieve dimming/speed regulation is the energy of the supply can be fully utilized and the efficiency of the circuit is high. For example: when the output is a 50% wave, the source energy by the width modulation (PWM) circuit is also 50%, is, almost all energy is converted into load output. When the common resistor step- speed regulation is used, to make the load obtain 50% of the maximum output of the supply, the supply must more than 71% of the output , of which 21% is by the voltage drop and heat consumption of the resistor. 2. The width modulation (PWM) can make the load get the full 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 of similar products on the market, which can meet the needs of 150W motors. 1. the cord, the positive and negative switches are in the middle position, the DC supply, the DC supply voltage range is greater than 10V, less than 36V, and the output of the supply meets the needs of the motor. Do not the positive and negative terminals of the DC supply in reverse, otherwise The governor may be damaged. 2. 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 position, the motor stops. 4. Potentiometer knob. Adjusting the potentiometer knob can change the output duty 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 the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.