Fire Alarm System Without Microcontrollers

This fire alarm system operates without microcontrollers, relying on basic electronic components like transistors, resistors, light-dependent resistors (LDRs), and buzzers.

Key Components & Their Roles

1. Light-Dependent Resistor (LDR) – Detects changes in light levels, triggering the alarm when smoke or fire disrupts the light source.
2. NPN Transistor – Acts as a switch, amplifying signals from the LDR.
3. Resistor – Limits current flow to protect components.
4. LED – Provides a visual indication when the alarm is triggered.
5. Buzzer – Sounds an alarm when the system detects fire or smoke.
6. 9V Battery – Powers the circuit.

Working Principle

• The LDR detects ambient light levels.
• If smoke or fire blocks the light, the resistance of the LDR changes, triggering the transistor.
• The transistor activates the buzzer and LED, alerting users of a fire hazard.
• The system resets automatically when normal light conditions are restored.

Wiring Connections

Component	Connection
LDR	Connected to transistor base
Resistor	Limits current to transistor
Transistor Collector	Connected to buzzer and LED
Transistor Emitter	Connected to ground
9V Battery	Powers the circuit

Advantages of This System

✅ No Microcontroller Required – Simple and cost-effective.
✅ Instant Response – Detects fire and activates the alarm immediately.
✅ Low Power Consumption – Operates efficiently with minimal energy.
✅ Easy to Build – Uses basic electronic components.