用51单片机实现频率恒定，占空比可变的PWM波形-Compared with 51 singlechip microcomputer frequency constant and variable PWM waveform

基于51单片机能实现流电机的驱动，带原理图对初学者有帮助-Based on 51 single chip microcomputer to achieve the flow of the motor drive, with a schematic diagram of the help for beginners