April 7, 2025 On April 7, 2025

MQ-2 Smoke LPG Butane Hydrogen Gas Sensor Detector Module

Posted by

MQ-2 Gas Sensor Module

Flammable Gas and Smoke Detection for Safety Applications

Introduction

The MQ-2 is a semiconductor gas sensor that detects combustible gases including LPG, propane, methane, hydrogen, alcohol, and smoke. With its high sensitivity and fast response time, it’s widely used in gas leak detectors, fire alarms, and air quality monitors.

MQ-2 Gas Sensor Module

Key Features

🔥 Multi-Gas Detection

LPG, propane, methane, hydrogen, smoke

⚡ Analog & Digital Output

Dual signal output options

🎛️ Adjustable Sensitivity

Potentiometer for threshold adjustment

🔋 Heating Element

Requires pre-heating time (~24h for stabilization)

Technical Specifications

Detection Range	300-10000ppm (LPG, propane, hydrogen)
Operating Voltage	5V DC ±0.1V
Heater Current	~150mA (heating circuit)
Output Signal	Analog (0-5V) + Digital (TTL)
Sensitivity	R_s/R₀ = 2-10 (1000ppm LPG)
Response Time	<10s (to 90% of final value)

Pin Configuration

Pin	Label	Description	Arduino Connection
1	VCC	Power (5V ±0.1V)	5V
2	GND	Ground	GND
3	DO	Digital Output	D2 (Digital Input)
4	AO	Analog Output	A0 (Analog Input)

Important: Requires 24-48 hour burn-in period for stable readings

Wiring Diagram (Arduino)

// Basic Connections:
// VCC → 5V (must be 5V ±0.1V)
// GND → GND
// AO  → A0 (Analog Input)
// DO  → D2 (Digital Input - optional)

// For best results:
// - Allow 24-48 hours for initial stabilization
// - Keep sensor away from direct airflow

Basic Gas Detection

const int analogPin = A0;
const int digitalPin = 2;

void setup() {
  Serial.begin(9600);
  pinMode(digitalPin, INPUT);
}

void loop() {
  int analogValue = analogRead(analogPin);
  int digitalValue = digitalRead(digitalPin);
  
  Serial.print("Gas Level: ");
  Serial.print(analogValue);
  Serial.print(" | Alarm: ");
  Serial.println(digitalValue);
  
  if(digitalValue == LOW) {
    Serial.println("Gas detected!");
  }
  
  delay(1000);
}

Advanced Applications

Calibration

// Calibrate in clean air
float R0 = 0;
const int cleanAirFactor = 9.83; // Sensor specific

void setup() {
  // After 24h warmup in clean air
  float sensor_volt = analogRead(A0)*(5.0/1023.0);
  float RS_air = (5.0-sensor_volt)/sensor_volt;
  R0 = RS_air/cleanAirFactor;
  Serial.print("R0 = "); Serial.println(R0);
}

PPM Calculation

// Convert to PPM (LPG example)
float getPPM_LPG(float R0) {
  float sensor_volt = analogRead(A0)*(5.0/1023.0);
  float RS_gas = (5.0-sensor_volt)/sensor_volt;
  float ratio = RS_gas/R0;
  
  // Empirical values for LPG
  float ppm = 1000 * pow(10, (log10(ratio)-0.8)/(-0.4));
  return ppm;
}

Temperature Compensation

// Add temperature compensation
#include "DHT.h"
DHT dht(DHTPIN, DHT11);

void loop() {
  float temp = dht.readTemperature();
  float analogValue = analogRead(A0);
  
  // Simple compensation (adjust coefficients)
  float compensated = analogValue * (1 + (25 - temp)*0.02);
}

Wireless Alert

// Send SMS alert when gas detected
#include 

void sendAlert() {
  GSM_SMS sms;
  sms.beginSMS("+1234567890");
  sms.print("GAS LEAK DETECTED!");
  sms.endSMS();
}

void loop() {
  if(digitalRead(D2) == LOW) {
    sendAlert();
    delay(60000); // Prevent SMS flood
  }
}