29-08-2017, 02:47 PM
In many applications, it is important to control the speed of the DC motor where accuracy and protection are essential. Here we will use a technique called PWM (pulse width modulation) to control the speed of the DC motor. The DC motor speed controllers are very useful for controlling the movement of robotic and industrial automation systems. The controller presented here uses the pulse width modulation (PWM) technique. The PWM wave for speed control is generated using the Atmel AT89C52 microcontroller. To control the speed of the DC motor, you need a variable voltage DC power supply. When the DC motor is on, it takes some time to reach full speed. As soon as the power is turned on, the DC motor starts to gain speed and if the power supply is turned off before it reaches the maximum rated speed, it starts to decrease. If the ignition and switch-off are carried out in rapid succession, the engine will rotate at a slower speed between zero and maximum rated speed. This is what makes a controller based on a PWM technique: it connects the motor 'on' and 'off' with a train of impulses. To control the motor speed, it varies (modulates) the width of the pulses, hence the pulse width modulation. When the engine is turned on for a short time and turned off for a long time, the engine turns slowly. When the engine is turned on most of the time and turned off only for a short time, it will rotate at a faster speed, say at near maximum (maximum) maximum speed.