Laser Intruder Alarm System

Topics: Operational amplifier, Amplifier, Output Pages: 10 (3274 words) Published: November 20, 2012
This Document contains Project Report of Autumn 2012 of Course CT-111.

 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.

 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 of Op-Amp gets less voltage.  Then it acts as non-Inverting amplifier.  It gives high voltage to transistor which ultimately passes current to buzzer and the buzzer buzzes.

 The 4017 decade counter has ten outputs which go HIGH in sequence when a source of pulses is connected to the CLOCK input and when suitable logic levels are applied to the RESET and ENABLE inputs.  Internally, the 4017 contains five bi-stable subunits. These are interconnected in a pattern known as a Johnson counter. The outputs of the bi-stables are decoded to give the ten individual outputs.

Operating voltages and currents of 4017 Timer:
 Minimum-6v  Maximum-15v  Max current-15mA  Max speed of operation-5MHz

Pin Configuration:

Output waveforms of 4017 Timer:

Sensor Interface..
 What if some Authentic Person want to enter into say some Bank-Locker system in some Banks.  Here we will provide a unique Identification card.  We used a sensor to recognize and electronic prototyped platform to switch off the Alarm system.

Basic Circuit for Slot Sensor:

Slot Sensor Working Principle:
 It contains an Infrared Light Emitting Diode and an photo transistor.  When power is supplied to the IR-LED it emits IR rays towards the photo transistor.  There is a finite voltage drop across resistor.  In the absence of light, output carrier has high voltage.

What is arduino?  It is an open-sourced free electronic prototyping platform.  In our project we used the arduino uno microcontroller.  Uno has five analog inputs.  Six pwm signal outputs.  In our project Uno facilitates the use of the slot sensors. Code:  The code consists of two parts, both mandatory o o    1.setup() 2.loop()

setup() is used to set the various ports of the uno as i/o. loop()- this part of the code is run indefinetly. void setup() { pinMode(8,OUTPUT); pinMode(A0,INPUT); pinMode(A1,INPUT); pinMode(A2,INPUT); pinMode(A3,INPUT); Serial.begin(9600); } //...
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