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Simple Infrared (IR) Intruder Alarm Circuit

This article tell how to make new type of Simple Infrared (IR) Intruder Alarm Circuit.

It can find person who walk through invisible light beam.

Circuit have two main part: one transmitter and other one is receiver.

Transmitter send out one infrared light beam across a room.

If someone goes in front of light the LED blink and alarm makes sound.

This project is good for learning more about electronics.

What is a Infrared IR Intruder Alarm Circuit:

One type of security device used in infrared technology is to find intruder is Infrared IR Intruder Alarm Circuit.

When warm body or person make through then infrared light sensor can see it.

Main idea is to use IR transmitter and receiver to make one barrier or zone.

When intruder walk through this area they break the IR beam and alarm starts making sound.

Transmitter Circuit Working:

Parts List:

CategoryDescriptionQuantity
Resistors470Ω (all 1/4 W CFR)2
2.2k (all 1/4 W CFR)1
Preset 10k1
CapacitorsCeramic 47nF1
Electrolytic 10µF 25V1
SemiconductorsIC 5551
IR Emitter LED1

This transmitter circuit uses IC 555 timer work like astable multivibrator which we can see in above diagram.

Infrared LED1 make light blink at around 5KHz speed.

Some good things of this blinking system are:

Adjust frequency of transmission depend on transmitter and receiver both.

Formula:

Below formula is to find frequency of 555 astable circuit using parts value:

Frequency (f) = 1.44 / (R1 + RV1 + 2R2) × C1

where:

Receiver Circuit Working:

Parts List:

CategoryDescriptionQuantity
Resistors (all resistors are 1/4 W CFR)47k 3
100k 3
100Ω 1
5.6k 1
CapacitorsCeramic 10nF1
Ceramic 100nF1
Electrolytic 2.2µF 25V2
Electrolytic 100µF 25V1
SemiconductorsTransistor BC5471
Diodes 1N41483
IC 7411
IR Receiver LED1
Relay 12V1

One infrared receiver diode LED1 is use in receiver circuit which is reverse biased and we can see this in above circuit diagram.

When IR light comes diode resistance goes up and voltage drop happen at point between R1 and LED1.

Here are main parts in receiver circuit:

Op-Amp Setup:

R2 and R3 give input at half of power supply.

R4, R5 and C2 used to calculate amplifier gain.

At 5KHz gain becomes very high which is even thousand times.

When receiver gets signal Op-Amp IC1 give AC output signal around 5KHz.

Other circuit parts:

D1, D2 and C4 work like voltage doubler.

Relay and Q1 transistor are used for switching.

When C4 get enough charge the relay turn ON.

If signal stops or break then relay turns OFF.

How to Build:

Steps to Build Simple Infrared (IR) Intruder Alarm Circuit is mentioned below:

Transmitter Circuit:

Receiver Circuit:

Alignment and Testing:

Test it:

Note:

Conclusion:

This smart and Simple Infrared (IR) Intruder Alarm Circuit gives more safety because of good alignment, fast working and strong receiver parts.

We can change frequency and test with different place of transmitter and receiver to make it work better for our design.

References:

INFRARED SENSOR BASED BORDER SECURITY SYSTEM

Intruder Detection System: A Literature Review

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