A circuit that detects the fire and activates the siren sound or buzzer is called an automatic fire alarm circuit. It is a very, very important device to detect fire in time and prevent damage to people or property.
It is a part of a security system that protects people and precious property like a bank, home, and accounting record of an organization. A 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.
Circuit 1. Auto Fire Alarm circuit with IR receiver Sensor
The flame sensor circuit/automatic fire detector circuit uses only an IR receiver sensor to detect Flame or fire. And we have 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 the drop on the IR sensor triggers the transistor. The transistor gate opens from emitter to collector, and the buzzer rings. Led will also glow.
2. Fire Alarm Circuit Using Thermistor
In this fire 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 with this sensor turns on the circuit.
Components of Fire Alarm Circuit
- Thermistor 10k
- Variable resistor (POT)
- Diode in4007
- Resistor 220 to 500 ohm
- BC547 NPN Transistor
- Speaker any
- Battery 6v to 9v
Circuit Diagram of a 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. The first stage of the fire alarm circuit is the input stage that is connected with the thermistor. The second stage of the fire alarm bell circuit consists of the output stage.