Introduction to speed control technique:
There are several techniques for controlling the speed of DC motor. Some of techniques used are rheostat and chopper control technique which are not that much effective. In this project we are going to employ PWM technique for controlling the speed of DC motor. The AT89C52 microcontroller generates required PWM wave.
A step down transformer is used to obtain the required voltage for the dc motor from the given 230V. A bridge rectifier is used to regulate the voltage generated. Capacitor is used to filter the generated voltage an IC7806 is used to bypass the ripples. The micro controller by using the timer 0 it generates the required PWM waveform. Two switches are connected to interrupt pins of micro controller, when these are pressed it changes the duty cycle of the dc motor. The generated variable pulse is given to drive the circuit which controls the speed of the motor. The PWM pulse is varied in 10 discrete pulses in the software program. The programming is written in c and keil software is used for compilation.
To obtain the required speed of the DC motor , certain tests are performed to check the speed of the motor. First the PWM circuit is tested the waveform is tested for each discrete pulse of the output voltages so that the changes occurred can be rectified. Then the speed of the motor is tested for varying voltages and the varying speed of motor is noted for every rise in voltages. Thus we conclude that the PWM technique is the most efficient for controlling the speed of the DC motor.
Download Micro controller Based Dc Motor Speed Control System Project Report.