Laser Intruder Alarm System

[LASER BASED SECURITY ALARM SYSTEM]
This Document contains Project Report of Autumn 2012 of Course CT-111.

PROJECT REPORT LASER BASED SECURITY ALARM
 An Alarm is a type of security equipment that can be used to safeguard houses and property.  Now a days Burglar Crimes are continually rising with each passing day.  Many have lost homes and families through violent burglaries in many countries  Some of them lost most precious things such as Jewelry, Vehicles, huge investments in banks etc..  This led to the development of ALARM SYSTEM

Basic circuit

Alarm Interface:
 We used LDR to detect Laser Light.  LDR pin was Fed to Op-Amp input leg.  Clock pulse to 4017 was taken from Op-Amp output pin.

Light Dependent Resistor (LDR)
 LDRs or Light Dependent Resistors are very useful especially in light/dark sensor circuits. Normally the resistance of an LDR is very high, sometimes as high as 1000 000 ohms, but when they are illuminated with light resistance drops dramatically.  Which acts as an sensor for our circuit.

Op-Amp-741
 The OP AMP is a ‘Linear Amplifier  Its main purpose is to amplify (increase) a weak signal  The OP-AMP has two inputs, INVERTING -2nd pin and NONINVERTING - 3rd pin, and one output at pin 6

1. An inverting amplifier
 Leg two is the input and the output is always reversed. In an inverting amplifier the voltage enters the 741 chip through leg two and comes out of the 741 chip at leg six. If the polarity is positive going into the chip, it becomes negative by the time it comes out through leg six. The polarity has been ‘inverted’.

2. A non-inverting amplifier
 Leg three is the input and the output is not reversed. In a non-inverting amplifier the voltage enters the 741 chip through leg three and leaves the 741 chip through leg six. This time if it is positive going into the 741 then it is still positive coming out. Polarity remains the same.

How it helps ?
 When the illumination on LDR stops its resistance increases so the leg 2