Fire Alarm Circuit

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Introduction

To secure the various process in different industries, heat is an important physical measurement. As you know that industries have furnaces, freezing substances, and melting machines, therefore in industries and the industrial process, temperature indicators, and fire alarms play a vital role. Usually, they are used to determine the temperature readings or levels. Moreover, it prevents the machines and environment from any hazardous or physical harm. Several temperature sensors and indicators are available in the market. There are many types of temperature sensors in the electronic industry. Thermistors, thermocouples, thermometers, and RTDs are some of them. In this circuit, we are using a thermistor sensor that uses a few components. So, in this tutorial, we are going to “Fire Alarm Circuit”.

Hardware Components

The following components are required to make a Fire Alarm Circuit

S.no	Components	Value	Qty
1.	IC	NE555 Timer	1
2.	Thermistor	103, NTC	1
3.	Buzzer	5V	1
4.	Transistor	BC547	1
5.	Potentiometer	100KΩ	1
6.	Capacitor	10μF/16V, 0.01μF	1,1
7.	Resistor	1KΩ, 4.3KΩ, 10Ω, 100KΩ	1,1,1,2
8.	Battery	9V	1
9.	2-Pin Connector	–	1

NE555 IC Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer

Fire Alarm Circuit

Working Explanation

In this Simple Fire Alarm Circuit, we are using a Negative Temperature Coefficient NTC of 10K, a Thermistor, and a 555 timer IC. The circuit includes the buzzer that generates the sound when the temperature near the thermal resistor increases more than the threshold limit. Hence buzzer turns ON when the temperature increases over the threshold voltage and turns OFF when the temperature is below the threshold voltage. Remember, that we can vary this threshold limit by using a potentiometer wired in the circuit.