Additional pins (D8 and D11) are used as LOW (GND) in the code

Published March 28, 2026

Smart Flame Detection & Alarm System

A compact and low-cost flame detection system using Arduino Nano that detects fire using an analog flame sensor and triggers a buzzer alarm

BeginnerWork in progress1 hour49

Things used in this project

Hardware components

DFRobot Gravity: Analog Flame Sensor For Arduino

LED (generic)

Buzzer

Arduino Nano R3

Jumper wires (generic)

USB Cable Assembly, USB Type A Plug to Micro USB Type B Plug

Software apps and online services

Arduino IDE

Story

IntroductionFire accidents can occur unexpectedly and cause serious damage if not detected early. Modern safety systems rely on sensors and automation to provide quick alerts and prevent hazards.

In this project, I built a flame detection and alert system using Arduino Nano, which can detect the presence of fire and immediately trigger a buzzer along with LED indicators.

Idea Behind the ProjectThe main goal of this project was to understand how flame sensors work and to create a simple real-time fire detection system.

Instead of relying on manual monitoring, the system automatically detects flame using infrared sensing and alerts the user instantly. This makes it useful for basic safety applications in homes, labs, and small setups.

How It WorksThe system uses an analog flame sensor to detect infrared radiation emitted by fire.

The flame sensor continuously reads the environmentArduino reads the analog value from the sensorThe value is compared with a predefined thresholdIf the value is below the threshold, flame is detectedThe system activates buzzer and LED alerts

Each output behaves as follows:Flame Detected → Buzzer ON + Red LED ONNo Flame → Buzzer OFF + Green LED ON

Hardware SetupThe circuit is simple and uses minimal components:

Arduino Nano as the main controllerFlame sensor (analog output connected to A0)Buzzer connected to digital pin D4Red LED connected to D9Green LED connected to D12Power supply (5V)

Additional pins (D8 and D11) are used as LOW (GND) in the code.

FeaturesReal-time flame detectionAudio alert using buzzerVisual indication using LEDsSimple and low-cost designEasy to build and understand

Challenges FacedWhile building this project, I faced some common issues:

Finding the correct threshold value for detectionFalse triggering due to ambient lightLow buzzer sound initially

These were solved by calibrating the threshold, adjusting sensor position, and using the tone() function for a louder alert.

Future ImprovementsThis project can be extended further by:

Adding IoT module (ESP8266) for mobile alertsIntegrating GSM module for SMS notificationUsing relay module to control fire safety systemsAdding LCD display for real-time monitoring

ConclusionThis project demonstrates how a simple flame sensor and Arduino Nano can be used to build an effective fire detection system. It provides both audio and visual alerts, making it useful for basic safety applications and a great learning project for embedded systems.

flame_code.ino

// ===================== CONFIGURATION =====================
const int FLAME_SENSOR_PIN = A0;
const int BUZZER_PIN       = 4;

const int RED_LED_PIN      = 9;
const int GREEN_LED_PIN    = 12;

// Optional (only if actually used in hardware)
const int RED_LOW_PIN      = 8;
const int GREEN_LOW_PIN    = 11;

const int THRESHOLD        = 300;   // Adjust based on calibration
const int BUZZER_FREQ      = 2000;  // Hz

// ===================== SETUP =====================
void setup() {
  Serial.begin(9600);

  pinMode(RED_LED_PIN, OUTPUT);
  pinMode(GREEN_LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);

  pinMode(RED_LOW_PIN, OUTPUT);
  pinMode(GREEN_LOW_PIN, OUTPUT);

  // Ensure LOW-side pins are grounded (if used)
  digitalWrite(RED_LOW_PIN, LOW);
  digitalWrite(GREEN_LOW_PIN, LOW);

  // Initial safe state
  digitalWrite(RED_LED_PIN, LOW);
  digitalWrite(GREEN_LED_PIN, HIGH);
}

// ===================== LOOP =====================
void loop() {
  int sensorValue = readFlameSensor();

  Serial.print("Flame Sensor Value: ");
  Serial.println(sensorValue);

  if (isFlameDetected(sensorValue)) {
    activateAlarm();
  } else {
    deactivateAlarm();
  }

  delay(200);
}

// ===================== FUNCTIONS =====================

// Read analog value from flame sensor
int readFlameSensor() {
  return analogRead(FLAME_SENSOR_PIN);
}

// Check if flame is detected
bool isFlameDetected(int value) {
  return (value < THRESHOLD);
}

// Activate alarm system
void activateAlarm() {
  tone(BUZZER_PIN, BUZZER_FREQ);
  digitalWrite(RED_LED_PIN, HIGH);
  digitalWrite(GREEN_LED_PIN, LOW);
}

// Deactivate alarm system
void deactivateAlarm() {
  noTone(BUZZER_PIN);
  digitalWrite(RED_LED_PIN, LOW);
  digitalWrite(GREEN_LED_PIN, HIGH);
}

Credits

ELECTRO MOTIF

5 projects • 0 followers

Electronics enthusiast focused on PCB design, power electronics, and embedded hardware. I design circuits and share hardware projects.

Smart Flame Detection & Alarm System

Things used in this project

Hardware components

Software apps and online services

Story

Additional pins (D8 and D11) are used as LOW (GND) in the code.

Code

flame_code.ino

Credits

ELECTRO MOTIF

Comments

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Smart Flame Detection & Alarm System

Smart Flame Detection & Alarm System

Things used in this project

Hardware components

Software apps and online services

Story

Additional pins (D8 and D11) are used as LOW (GND) in the code.

Code

flame_code.ino

Credits

ELECTRO MOTIF

Comments

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