Infrared Security Alarm

Wondering if you can setup a small and cheap alarm system for your home? Then you are at the right place because I present to you an infrared security alarm system that you can create at your home yourself easily by spending some small amount of money and making up a simple circuit if you have good enough knowledge about electronics.

An infrared security alarm system is based on the detection of an intrusion caused by the interruption of an infra-red (which is invisible to human being) light beam being emitted by an infra-red LED and falling on a matched IR sensor. Both the transmitter and the receiver portions separately operate on 6v supplies. The transmitter and the receiver’s circuits can be mounted in an aligned position on the two sides of a door to check intrusion or even on the two facing walls of inside of a locker to give you an alarm whenever an unauthorized person attempts a mischief. The circuit has a provision of both audio as well as visible indications. The audio indicator and the visible indication can be remotely located away from the location of gadget also. The IR based system is very much advanced and works very much accurately. This type of devices are designed and marketed by the different multinational companies.

I have tested this circuit by myself on a vero board and it works 100% accurately.

Components Required:

1. Power Supplies:
   • 2x 220V-9V (or more) Step Down Transformer
   • 2x Bridge Rectifier
   • 2x 7806 IC
   • 2x 3300uF Capacitor
   • 2x 10uF Capacitor
   • 2x Heat Sink
2. Transmitter Section:
   • 1N4148 Diode
   • 1 Kohm resistor
   • 22 ohm resistor (0.5W)
   • 2.2 Kohm resistor
   • 2x 0.01 uF capacitor
   • Pot 4.7 Kohm variable resistor
   • BC547 Transistor
   • 555 IC
   • Infrared LED
3. Receiver Section:
   • TSOP 1738 IR Receiver
   • 2x 220 ohm resistor
   • 1.8 Kohm resistor
   • 2x 4.7 Kohm resistor
   • 2x 1 Kohm resistor
   • 1 Mohm resistor
   • 470 ohm resistor
   • 220 Kohm resistor
   • 4.7 ohm resistor (0.5W)
   • 47 uF capacitor (16V)
   • 2x 0.1 uF capacitor
   • 10 uF capacitor (16V)
   • 100 uF capacitor (16V)
   • 2x BC547 transistor
   • BC558 transistor
   • 3.3V zener diode
   • 1N4007 diode
   • LED green +red
   • Speaker 8ohm (1W)
   • CD4538 IC
   • UM3561 IC

Circuit Diagram:

Power Supply:

Transmitter:

Receiver:

Working:

In the transmitter circuit,we have taken IR because IR is invisible to the eye, where as in case of LASER, which is easily visible to the human eye by which will, alert the unauthorized person. That is why we have taken IR as a transmitter which will transmit a continuous IR signal. The 555 timer generates a 38KHz frequency which is then sensed by the TSOP1738 in receiver circuit.

The transmitted IR signal directly falls on IR sensor TSOP1738. Whenever the IR signal is interrupted, its output pin 3 goes low and IC2 is triggered at pin 5 through transistor T2. As a result, its output at pin 7 goes low (for a preset time) to forward bias siren-driver transistor T2. This condition is indicated by the glowing of LED1. The time-out period can be increased or decreased by changing the value of capacitor C6.

The output tone of siren-sound generator IC3 can be set by connecting its pin 6 to either Vcc or GND. When you connect pin 6 to Vcc IC3 produces the sound of fire-alarm siren, but when you connect it to GND it produces the sound of ambulance siren.

Notes:

• Both circuits have to be powered by different 6v power supplies.
• You may see and check the infrared led is glowing or not by using a camera.
• Receiver circuit may not properly sense the infrared led on a breadboard as it didnt work for me, so its better to assemble the circuit on a vero board or PCB.
• Heat sinks should be used with the 7806 ICs or the IC may get damaged if the circuit is powered on for a long time.
• Alarm turns off after about 5-10 seconds of getting the contact with IR again.
• Range of the circuit is about 5m.
• Vary the variable resistor to increase or decrease the intensity of the IR LED for better performance in lighting conditions.

Enclose your infrared security alarm system in different plastic or metal packaging and install it on adjacent walls of ur door and your home will be in protection.