Introduction
A fire alarm is a critical safety device that alerts individuals of a potential fire in a building. A simple fire alarm circuit is an easy-to-build and cost-effective solution to detect the presence of smoke or heat. When a fire is detected, the circuit triggers an alarm, alerting everyone to evacuate or take action immediately. This circuit is an excellent choice for small homes, offices, and workshops where a more advanced fire alarm system is not required.
In this article, we will delve into the design and construction of a simple yet effective fire alarm circuit. With its ease of use and low cost, this circuit can play a crucial role in ensuring the safety of the people and property in the event of a fire.
Hardware Required
You will require the following hardware for Fire Alarm Circuit.
| S.no | Components | Value | QTY |
|---|---|---|---|
| 1 | Relay | 9V SPDT | 1 |
| 2 | Transistor | AC128, BC177, BC108 | 1, 1, 1 |
| 3 | Diode | 1N4007 | 1 |
| 4 | Polar Capacitor | 2.2, 100uF | 1, 1 |
| 5 | Resistor | 1k, 100k | 1, 1 |
| 6 | Variable Resistor | 470k Preset | 1 |
Circuit Diagram
Working Explanation
The Simple Fire Alarm Circuit works by using a transistor BC177 (Q1) as a fire sensor. When the temperature increases, the leakage voltage of this transistor also increases. The circuit is designed such that an increase in the leakage of Q1 will trigger transistor Q2.
When there is a fire breakout, transistor Q2 will turn on, turning on transistor Q3. Transistor Q3 drives a relay, which can be used to activate a light, bell, or horn as an indication of a fire. The diode D1 acts as a free-wheeling diode to protect the circuit from the back EMF created when the relay switches.
We can adjust the Preset R1 to the desired temperature level to set the alarm. However, this is not a latching alarm, meaning that the alarm will stop once the temperature in the sensor’s area drops below the set point.
Depending on your needs, the load can be connected through the relay contacts’ C, NC, and NO points. The adjustment can be made using a soldering iron and a thermometer. To do this, switch on the power supply and keep the soldering iron tip near Q1 while keeping the thermometer near it. We can adjust the temperature to the desired level by sealing R1.
Final Words
In conclusion, a simple fire alarm circuit can be built using basic electronics. This fire alarm circuit is a low-cost and effective solution for basic fire detection applications. Let’s try this circuit, and if you have any queries, our comment section is open for you. Happy building!
