Design of 8051 Microcontroller Based Security System with a Laser Beam Network

This article describes a low cost microcontroller based security system using a laser beam for use in highly restricted office areas, buildings etc. The laser beam from the laser diode is directed to fall on an LDR by reflecting the beam using four mirrors placed at the four corners of the door. As the beam is interrupted by the intruder, a buzzer raised to the circuit goes ON. The system also has a password lock and entering the wrong password too triggers the buzzer to go ON. An 8 bit password can be programmed in to the microcontroller. On entering the correct password, the shutter, driven by a stepper motor connected is Port0 of 8051 microcontroller through the buffer IC ULN2003, is opened the control programs have been developed using 8051microcontroller assembly language.