Emergency Protocol: Arduino Fire Alarm

A standard smoke detector looks for microscopic particles in the air. The Arduino Fire Alarm utilizes entirely different physics, relying on the raw infrared radiation (IR) emitted by active combustion. This project teaches the threshold calibration of sensitive analog inputs designed to protect property and trigger automated responses.

The IR Flame Sensor Diodes

A generic temperature sensor (like a DHT11) will only trigger if the room becomes incredibly hot. The KY-026 IR Flame Sensor can mathematically "see" a candle flame from 10 feet away in a freezing room!

1. The Spectrum Physics: An active fire emits invisible Infrared radiation with a wavelength between 700nm to 1000nm. The photodiode on the sensor is electrically tuned specifically to this frequency.
2. The sensor has both a Digital D0 and Analog A0 output. The analog pin allows extreme sensitivity tuning.
3. int fireIntensity = analogRead(A0);
4. In total darkness without fire, the value reads 1023. The instant a lighter is flicked across the room, the value plummets down to 200!

Multi-Factor Detection (Relay Safety)

A good safety system requires redundancy.

• If a burst of sunlight perfectly hits the IR sensor, it might trigger a false alarm, which is unacceptable if the system automatically triggers an expensive fire-suppression water pump!
• The system must verify the threat using an NTC Thermistor (Heat) or an MQ-2 Sensor (Smoke/Combustible Gas).
• The Logic Gate:

if ((fireIntensity < 300) && (ambientTemp > 45)) { // IR Light AND physical high heat
  digitalWrite(SprinklerRelay, LOW);
  TriggerKlaxonSiren();
}

Emergency Hardware Kit

• Arduino Uno/Nano.
• KY-026 Infrared Flame Sensor Module (5-pin or 4-pin analog).
• Active Piezo Buzzer or 12V Industrial Siren (Driven via an NPN Transistor).
• 5V Optically Isolated Relay (If simulating the triggering of a water pump or automatic fire door release).