⚠️ MQ-2 Gas Leakage Alarm

Detect combustible gases and smoke using the MQ-2 sensor and trigger an audible alarm.

📋 Overview

The MQ-2 is a versatile sensor sensitive to LPG, propane, hydrogen, and smoke. It uses an internal heating element, so it needs a 'warm-up' period before readings become stable.

What you'll learn: Gas sensor calibration, analog thresholds, and safety system logic.

Estimated time: 35-45 minutes. Difficulty: ⭐⭐ Easy.

🧩 Components Needed

Component	Specification	Qty
Arduino Uno R3	5V	1
MQ-2 Gas Sensor	Analog output	1
Piezo Buzzer	Active/Passive	1
Red LED	Warning light	1
Resistor	220Ohm	1

🗺️ Component Pin Mapping

📖 Step-by-Step Tutorial

Connect MQ-2

VCC → 5V, GND → GND, AO → Pin A0.

Connect Alert

Buzzer to pin 8, LED to pin 9.

Pre-heat Sensor

Let the sensor run for 2-3 minutes. It will get warm — this is normal.

Set Threshold

Check Serial Monitor for clean air values (~100-200). Use a lighter (don't ignite!) to test gas response.

💡

The MQ-2 sensor has a small heater inside. If it's brand new, it might need to "burn-in" for 24 hours for maximum accuracy, but it works for basic projects in minutes.

💻 Arduino Code

gas_detector.ino

INO

// Gas Leakage Alarm : Volt X
const int gasPin = A0;
const int buzzer = 8;
const int led = 9;
const int threshold = 400; // Adjust for your environment

void setup() {
  pinMode(buzzer, OUTPUT);
  pinMode(led, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int val = analogRead(gasPin);
  Serial.println(val);

  if (val > threshold) {
    digitalWrite(led, HIGH);
    tone(buzzer, 1000); // Continuous alarm
  } else {
    digitalWrite(led, LOW);
    noTone(buzzer);
  }
  delay(200);
}

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