系统上电，液晶显示小直流电机的运行方向和速度等级，K3键使电机进入运行状态，电机正转运行8秒停3秒后反转运行8秒停3秒，循环往复，复位后使电机停止。在电机运行过程中，K2键和K3键可调整小直流电机的运行速度。控制原理是PWM（脉宽调制）。-System, electricity, liquid crystal display a small DC motor direction and speed grades, K3 keys to enter the motor running so that the electrical is run to eight seconds after the inversion stops three seconds to run 8 seconds stop 3 seconds, cycle after the reset so that the electrical停止. Running in motor, K2 and K3 key small button adjustable speed DC motor. Control principle is PWM (Pulse Width Modulation).