01-09-2012, 03:08 PM
DC MOTOR SPEED CONTROL SYSTEM USING AT89S52 MICROCONTROLLER
DC MOTOR SPEED.docx (Size: 61.05 KB / Downloads: 92)
Description:
There are several applications with dc motors in our daily life. We require different speeds at different instants depending on the applications. There are several techniques to control the speed of dc motor; PWM technique is one in those. PWM stands for pulse width modulation. Pulse width modulation (PWM) is a powerful technique for controlling analog circuits with a processor's digital outputs.
PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. By controlling analog circuits digitally, system costs and power consumption can be drastically reduced. At any given instant of time, the full DC supply is either fully on or fully off. The voltage or current source is supplied to the analog load by means of a repeating series of on and off pulses. The on time is the time during which the DC supply is applied to the load, and the off time is the period during which that DC supplies is switched off. By giving sufficient bandwidth, any analog value can be encoded with PWM.
In this technique we use duty cycle concept for controlling the speed. If motor is given a supply for 10 mille second and it is not given a supply for 90 mille second by using PWM then motor will move with speed 10% of its rated speed and likewise the speed of the motor can be vary by varying the ON period and OFF period of supply. For this application we are connected keypad to the microcontroller for varying the speed. When we press different buttons motor will rotate at different speeds.
For measuring the speed of the motor at which it is rotating we are using slot sensor. The output of slot sensor is given to microcontroller and that will be displayed on LCD.