PIR Sensor Based Security System

The below circuit is a very cheap in price and very highly secure electronic system.Which can be used in bank and other high security areas.
As we know a normal security system has a transmitter and receiver.Transmitter sends out an IR laser and the signal receiver received this signal and thus receiver activate the alarm.But these system has very major disadvantages like limited range and poor line of sight.And these major advantages are eliminated through this PIR sensor security system.

We are using PIR(Passive Infrared Radial) sensors instead of infrared or laser transmitter and receiver in this project.This PIR sensor is basically a pyroelectric device.when the device exposed to infra radiation, it generates electric charge.When the change in amount of infrared striking the element,there will be a change in the voltage generated which is measured by an on-board amplifier.

                                                               The device contains a special filter called a Fresnel lens, which focuses the infrared signals onto the element. As the ambient infrared signals change rapidly, the on-board amplifier trips the output to indicate motion. We can say that the PIR sensor is a human body sensor because it is only activated when a human or animal walks past the sensor. The PIR sensor is the heart of the project. We can design the project in such a manner that as soon as the burglar or intruder walks past the sensor, the alarms would turn on and the whole lighting system could turn on.  

Circuit Diagram







Block diagram of the PIR based security system

PIR Sensor

*   D204B PIR sensor is used in this project. The PIR sensor is the heart of the project.
     Two Stage Amplifiers

Two stage OP-amp

*    LM 324 is used as two stage amplifier. The signal from the PIR sensor is very low so this   signal is amplified by using LM324.LM324 is a quad OP-amp. First two op-amps act as          amplifiers. 

Comparator 

*    The comparator compares the signal from the amplifier and a reference voltage.3rd and 4th OP-amp of LM 324 act as comparator. 

Transistor Switch

*    Whenever the output of comparator make HIGH Q1 transistor gets ON and relay will be energized causing the alarm and lamp to turn ON. 

Power Supply

*    Power supply converts 230 Volt AC into 12 Volt DC and 5 Volt DC. IC 7812 is used as the 12 Volt voltage regulator and a 5v zener diode act as the 5 Volt voltage regulator.