A Circuit that detects the fire and activates the Siren Sound or Buzzer is called Automatic Fire Alarm Circuit. It is a very very important device to detect fire in time and prevent damages to people or property.
It is part of a security system that protects people and precious property like a bank, home, and accounting record of an organization. Fire Alarm circuit is a necessary part of today's busy life. Many expensive Fire Alarm Circuits are available in the market but we are going to make 5 very simple Automatic Fire Alarm Circuits in this article.

Automatic Fire Alarm Circuit using thermistor

Automatic Fire Alarm Circuit using thermistor

A flame sensor circuit / Automatic Fire Detector Circuit uses only an IR receiver sensor to detect Flame or fire. and we used a buzzer and a red led to show the output of the circuit. It is a very famous sensor in the world. To understand this circuit deeply see the diagram and the structure of the circuit.

Description Automatic Fire Alarm Circuit

The following diagram of the fire alarm circuit using a transistor clearly shows that it will be triggered by the IR Receiver sensor. when the flame of drop on the IR sensor triggers the transistor. The transistor gate opens from the emitter to the collector and buzzer ring. Led will also glow.

2. Fire Alarm Circuit Using Thermistor

In this Fir Alarm system, we have used a thermistor as a heat sensor. When the heat comes on this sensor its resistance increases and the transistor that is connected to this sensor turns on the circuit.

Components of Fire Alarm Circuit

  • Thermistor 10k
  • Variable resistor(POT)
  • Diode in4007
  • Resistor 220 to 500ohm
  • BC547 NPN Transistor
  • Speaker any
  • Battery 6v to 9v

Circuit Diagram Simple Fire Alarm System

Fire Alarm using Thermistor and 555 ic

In this circuit, we use a thermistor with a 555 timer ic instead of the transistor to increase sensitivity.

Circuit Diagram Fire Alarm Circuit

This circuit consists of two stages. 1st stage of the fire alarm circuit is the input stage that is connected to the thermistor. The second stage of the fire alarm bell circuit consists of the output stage.