This simple fire alarm circuit uses a heat sensor to detect high temperatures and alert you with an LED and buzzer, helping you stay safe at home.
Key Components Required
- NTC type thermistor-10KΩ ►https://amzn.to/3BkTJoI
- Transistor BC547►https://amzn.to/3kzDq0t
- Variable Resistor-10KΩ►https://amzn.to/3mQAEGK
- LED►https://amzn.to/2XX0Uoz
- Buzzer►https://amzn.to/38pL0VG
- Zero PCB►https://amzn.to/3gLrKqj
- 9v Battery►https://amzn.to/3BmJekD
Circuit
How It Works
The circuit’s operation is based on the unique property of the NTC Thermistor:
- The NTC thermistor changes its resistance with temperature: as the temperature rises (like near a fire), its resistance decreases.
- This change causes the voltage at the transistor’s base to increase.
- When the base voltage crosses a threshold set by the variable resistor, the BC547 transistor switches ON.
- This allows current to flow to the LED and buzzer, turning them ON to alert you.
- The variable resistor lets you adjust at what temperature the alarm activates, making the circuit customizable.
- Powered by a 9V battery, this circuit is compact and easy to install.
Watch the full video tutorial here: How to make a simple Fire alarm at Home | heat sensor with explanation using transistor BC-547