MICROCONTROLLER BASED OPEN-LOOP SPEED CONTROL SYSTEM FOR DC MOTOR

This paper presents open loop speed control scheme for the speed control of a permanent magnet DC motor using an AVR Microcontroller. The microcontroller has been programmed to automatically vary the duty cycle of the H-bridge chopper depending upon the set/required speed of the motor. The chopper is driven by a high frequency PWM signal. Controlling the PWM duty cycle is equivalent to controlling the motor terminal voltage, which in turn adjust directly the motor speed. The PC interfacing has been done using serial port (DB9 Connector). Experimental results show that proposed system is suitable for different industrial applications such as trolley buses, subway cars, or battery-operated vehicles.