Simple Fire Alarm Circuit Using Thermistor

Fire safety systems don’t always have to be complex or expensive. In this project, we’ll build a simple and effective fire alarm circuit using easily available electronic components. It’s a great beginner-friendly project that demonstrates how temperature sensing can be used to trigger alerts. 🔥 Overview This fire alarm works by detecting a rise in temperature using a thermistor. When the temperature crosses a certain threshold, the circuit activates a buzzer to alert you. It’s ideal for learning basic electronics, sensor behavior, and simple circuit design. 🧰 Components Required Thermistor (NTC type) Transistor (BC547 or equivalent) Buzzer Resistors (various values, typically 1kΩ–10kΩ) Variable resistor (potentiometer) Battery (9V) Breadboard and connecting wires ⚙️ How It Works The key component in this circuit is the NTC thermistor (Negative Temperature Coefficient) . Its resistance decreases as temperature increases. Here’s what happens step by step: At normal temperature, the ther