Design of a Microcontroller-Based Photo-Controlled Circuit for Adjusting the Speed of DC Motors


There are many approaches and methods for changing the speed of DCmotors. One of these approaches is through the intensity of light. In thispaper, a microcontroller-based control circuit for adjusting the speed of aDC motor by means of interrupting the incident light is proposed andimplemented. The adopted technique in this circuit uses two lightdependent resistors as photo-sensors to detect the illumination of light byproducing a prescribed digital sequence to activate one of the input portsof an 8051 microcontroller. An assembly program stored in the on-chipprogram memory of the microcontroller generates the proper PWM signalat an output port based on the received sequence. This signal is suppliedto the driving circuit of the motor in order to run it with the relevant speed.The circuit has been implemented and tested successfully in thelaboratory.