IR Based Burglar Alarm

There are various security systems available in the market, but they are very costly like the one from the leading manufactures like godrej etc. 

The product offered by these is no doubt good but is really expensive for the middle class families, in our project we aim to develop a system which is extremely low at cost, small in size and provide an extremely secure way to detect the intruders.

This project can be used on doors in homes or in corporate offices or in safes etc.

Whenever a person tries to interrupt between the transmitter and receiver the buzzer will blow, indicating the alarm.

This is illustrated in the following figure:

Block Diagram without Intruder

Block Diagram with Intruder

The above figure shows how this IR Based Burglar Alarm works, when some person came in the path between transmitter and receiver the Buzzer will blow and a Green Led on the board will glow.

The project is basically divided into three parts

• Power Supply Section
• Transmitter Section
• Receiver Section

Power Supply Section:

Power Supply section provides, the supply to the receiver and transmitter (right now, separate battery for transmitter is provided by 9V Battery, but we can use our Power Supply to power transmitter section also).

Receiver Section:

Receiver Section consist of IR-Receiver IC TSOP1738 which detects the IR Rays, and with the help of this the buzzer and green led is blown when someone interfere the path between receiver and transmitter.

Power Supply and Receiver

Transmitter Section:

Transmitter Section is used to transmit the IR-Signal at a frequency of 38KHz using a 555 IC and two IR-Led’s along with some additional components to adjust the frequency and duty cycle.

Transmitter

Above figures shows how the Transmitter and receiver looks, at component level the detailed circuit diagrams for Power Supply, Receiver and Transmitter are shown in the following sections.

POWER SUPPLY CIRCUIT:

Power Supply Section

The Power Supply Circuit Diagram is shown above, it consist of a step down transformer which scales down the 220V transformer into 18V, than a full-wave rectifier, made by using 4-Diodes is used for rectification Purpose, then after that a 1000uf/25V capacitor is used to stabilize the supply i.e to smooth the supply to make it nearly equal to DC supply, then two IC 7805 and 7812 are used to convert the input supply to exact DC supply of 5V and 12V.

TRANSMITTER CIRCUIT:

The main objective of transmitter circuit is to transmit Infra-Red Led’s at a frequency of 38KHz. For this purpose a 555 Timer IC is used, which is configured in Astable Multivibrator Mode and with the help of this the 38KHz pulse is generated at the pin 3 of 555 IC. A simple combination of transistor BC547 and two Infra-Red Led’s are used as shown in above to generate the Infra-Red light of 38KHz frequency.

Transmitter Section

RECEIVER CIRCUIT:

The receiver circuit consist of a TSOP1738 IC and associated circuitry for IR Based Burglar Alarm, TSOP1738 gives Low output(0V) when there is IR falling on it at a frequency of 38KHz and gives output of (1V) when no IR ray falling on it, we are utilizing this property of TSOP1738 IC and Infra-Red rays to construct a receiver. The receiver circuit is shown in following figure:

Receiver Section

Component List:

Transmitter Side:
R1 = 1.8KOhm
R2 = 18KOhm
R3 = 3.5Ohm
R4 = 150 Ohm
C1 = 1nF
C2 = 0.1uF

Receiver Side:
R1 = 2.7KOhm
R2 = 150Ohm
C1 = 10uF
C2 = 4.7uF

Video Demonstration: