26-05-2012, 05:00 PM
dc motors
ABSTRACT
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.In this technique we use duty cycle concept for controlling the speed. If motor is given a supply for 10 milli second and it is not given a supply for 90 milli second by using PWM then motor will move with speed 10% of its rated speed and like wise 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. In this project we can vary the speed of motor by pressing the buttons. That means motor will rotate with more speed when the firing angle of SCR is less and speed will decreases as the firing angle increases 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..