In this project we will control speed of series wound motor with brushes. We are using 8051 Micro-controller to control the speed of motor. An LED display is used to display the speed.
AC motor speed is controlled by changing firing angle of TRIAC with the help of micro controller AT89C51. Varying speed of AC motor by means of changing firing angle of any thyristor is very widely used method. One very nice example is fan regulator in which a fan motor is an AC motor used and its speed is varied using TRIAC method.
A zero crossing detector circuit is used here to interrupt AT89C51 after every 10 ms. After getting an interrupt 89C51 will fire TRIAC after some delay from 1 to 9 ms. This will cut the current supplied to motor and so the speed of motor will reduce. Thus by varying the delay after which the TRIAC is triggered one can change the speed of motor.