Super Sensitive Intruder Alarm System Using IR And 555 Timer

In this project, the Super Sensitive Intruder Alarm circuit is designed to alert the owner when an intruder enters their home. If there is any obstacle in front of an infrared sensor, it generates an interrupt signal. This interrupt signal is given to the buzzer as output to alert the owner.

Principle Behind Super Sensitive Intruder Alarm

The infrared transmitter always transmits the IR (Infrared) rays which have to be received by the infrared receiver. When there is an obstacle comes in front of the IR sensor, the transmitted IR rays are reflected by that obstacle and back to the IR receiver. The output of the Op-Amp will become high when the IR receiver receives those IR rays. This output of the Op-Amp is connected to the RESET (Pin 4) pin of the 555 timer IC.

The output of the 555 timer IC is low when the input voltage applied at the RESET pin of the 555 timer IC is low. When the input voltage at the RESET pin is high, the 555 timer IC produces the frequency which varies on the resistors R1, R2 and capacitor C3.

The output of the 555 timer IC is filtered by the 1uF/16V electrolyte capacitor and given to the buzzer.

Different IR sensors are placed in the housing complex at different locations. The outputs of all these IR sensors are given to the RESET pin of a common 555 timer IC. When any of these sensors detect the intruder, the reset pin of the 555 timer IC becomes high and the buzzer will start to beep.

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Super Sensitive Intruder Alarm

Circuit Diagram

Super Sensitive Intruder Alarm Circuit Diagram
Super Sensitive Intruder Alarm Circuit Diagram

Components Required

  • NE555 Timer IC
  • LM358 Op-Amp
  • 10K Preset
  • IR Transmitter
  • IR Receiver
  • Red Led
  • Ceramic Capacitors (0.1uF, 0.01uF)
  • Electrolytic Capacitor – (1uF, 16V)
  • 10KΩ, 1KΩ, 100Ω Resistor
  • 330Ω Resistor (x2)
  • Buzzer
  • Breadboard
  • Wires
  • +5V Power Supply

Circuit Connection of Super Sensitive Intruder Alarm

555 Timer IC

The 555 timer IC acts here as a free-running oscillator. It will generate frequency when a high pulse is applied to the RESET pin. The generated frequency of the 555 Timer IC varies by varying resistor values R4, and R5 capacitor C3.

Here Pin 2 and pin 6 of the 555 timer ICs are shorted to allow the triggering after every timing cycle. In this circuit, capacitor C3 charges through the resistors R4, and R5 and discharges through the resistor R5.

LM358 Op-Amp

Every LM358 IC consists of two operational amplifiers. Each Op-Amp has two inputs (inverting input and non–inverting input) and one output. The output will be high when the non-inverting input is greater than the inverting input and it is low when inverting input is greater than the non-inverting input.

IR Transmitter

The operating input voltage of this IR transmitter is around 2V to 3V. To drop the remaining voltage we connect a resistor in series with an IR transmitter.

IR Receiver

It is always placed in reverse bias with the circuit. It almost acts as a closed circuit when it receives IR rays and it becomes resistant when it does not receive any IR (Infrared) rays.

Operation of Super Sensitive Intruder Alarm

First, we have to connect all the components to the circuit and give a +5V power to it.

After that move any obstacle in front of the infrared sensor. At that moment the circuit will catch the transmitted IR rays and turn this circuit to become high. The buzzer will beep the sound then.

And when no obstacle is found near the IR sensor, the circuit will remain low. So no sound will be a beep.

That’s how the whole circuit will operate.

Application of Super Sensitive Intruder Alarm

The intruder alarm system is used in housing and offices for security purposes.

Disadvantage of This Super Sensitive Intruder Alarm

This circuit also produces sound even if there is any non-living thing in front of the IR sensor.

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