Simple Burglar Security Alarm Circuit Using LM358

In this tutorial, I will show you a burglar security alarm system designed to detect unauthorized entry into a house. A burglar security alarm system can be used in residential buildings, commercial buildings, offices, industries, and military bases. In most cases, these security systems are too much costly but this inexpensive project can overcome such problems. A simple burglar security alarm is here using the IR transmitter, IR receiver, and an LM358 op-amp for home purposes.

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Burglar Alarm circuit

Circuit Diagram

burglar security alarm

Components Required

  • LM358 IC
  • IR Transmitter
  • IR Receiver
  • 10 KΩ Potentiometer
  • 150 Ω Resistor
  • 10 KΩ Resistor
  • Buzzer

Circuit Connection

In this burglar security alarm circuit, the cathode of the IR transmitter is connected to the positive supply while the anode is to the ground supply through a resistor of 150 Ω. It is placed at a suitable position from the IR receiver.

The anode of the IR receiver is connected to the positive supply while the cathode is connected through a 10 KΩ resistor and placed to the ground. The cathode of the IR receiver is also connected to pin 5 of the LM358 IC, which is the non-inverting terminal of the op-amp.

The middle pin of the 10 KΩ potentiometers is also connected to the inverting terminal of pin 6 of the LM358 IC while another two terminals of the potentiometer are connected to positive and ground supply.

Pin 8 and pin 4 of the LM358 IC are connected to positive and ground supply respectively.

The output of the op-amp is obtained by pin 7. The negative terminal of the buzzer is connected to pin 7 of the LM358 IC while the positive terminal is connected to the positive supply.

Working Principle of Burglar Security Alarm

In this burglar security alarm, LM358 op-amp IC is configured as a comparator in this project. When the whole system is turned on, the IR transmitter starts to emit infrared rays. These infrared rays fall on the surface of the IR receiver.

As the IR receiver is connected in reverse bias condition, when the rays fall on it, it conducts a current flowing through it. Since it is connected to the non-inverting terminal of the op-amp, the output of the op-amp will be high.

As the buzzer is connected between the positive and the output terminal of the op-amp, no alarm is activated.

When an intruder enters the gap between the IR transmitter and the IR receiver, the rays falling on the IR receiver are blocked and it doesn’t conduct any current.

As a result, the input at the non-inverting terminal is less than the input at the inverting terminal. Hence, the output of the comparator is very low. This will trigger the buzzer and the alarm is activated then.

Application of Burglar Security Alarm

It can be used as a home security alarm for intruders or burglars.

It can also use for counting purposes like how many people enter from a gate.

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