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Timers are very useful both for industrial applications and household appliances. The PC Based Timer circuit interfaces with a computer through a D25 pin male connector to switch ON/OFF a device for a particular time interval. The program of the PC Based Timer is written in C language & compiled using the Turbo C compiler. The maximum timing for which the circuit can operate a device is 18 hours. No. of ICs used: 1
Things which you will learn :
*Application of the optocoupler IC MCT2E.
*Application of the NPN transistor for switching.
*Application of diodes for freewheeling/flyback.
The PC Based Timer uses a simple program and interface circuit to switch on/off the appliance via the relay circuit. The circuit is interfaced with the PC with a D25 pin male connector.
The circuit uses the IC MCT2E(optocoupler) which isolates the PC and the relay driver circuits. The MCT2E prevents the PC from any short circuit that may occur in the relay driver circuit or appliance. The glowing of a red LED in the circuit indicates that the appliance is turned on while the NPN transistor BC548 is used as the relay driver.
The program code is written in ‘C’ language and compiled using ‘Turbo C’ compiler. When the program is run, it prompts the user to input the time duration in seconds or minutes to control the appliance.