Design and Fabrication of Alarming System Based on Laser and LDR

Illegal crimes such as robbery, theft, and intrusion are common in the community nowadays. The use of locks and alarms on doors and windows is a common deterrent to burglaries of this type. In this research, a new security system is proposed, the proposed system is constructed based on a multi-laser alarm system and Light Dependent Resistors (LDRs). Multiple lasers are used to find movement in the location, just like the laser systems in action movies. This is based on the voltage divider circuit theory. When a laser beam is continually focused on an LDR, the voltage drop across it is extremely low as the LDR’s resistance decreases. When a laser beam is interrupted by an item or a barrier, the voltage drop across it increases due to a change in the resistance of the LDRs. This activates the circuit’s alarm or siren. The proposed system is described in detail. The results prove the proposed system works in detecting different objects.