MQ-2 Gas Sensor Module For H2, LPG, CH4, CO, Smoke or Propane Detector Module

MQ-2 Gas Sensor Module 

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Applications:

• Safety of home
• Control of air quality
• Measurement of gas level
• Gas leakage alarms
• IoT safety

MQ-2 Gas Sensor Module – Quick Start Guide

Wiring Guide

• Connect VCC to Arduino 5 V.
• Connect GND to Arduino GND.
• Connect A0 (analog output) to Arduino analog pin A0.
• Optional: Connect D0 (digital output) to Arduino digital pin (e.g., D2) for threshold detection.
• Allow the sensor to pre-heat for a few minutes before use.

Arduino Code Example – Analog Read

#define sensorPin A0    // analog input pin for MQ-2
int sensorValue = 0;

void setup() {
  Serial.begin(9600);
  Serial.println("MQ-2 Gas Sensor Test");
  delay(2000);  // sensor stabilisation
}

void loop() {
  sensorValue = analogRead(sensorPin);
  Serial.print("Gas Sensor Reading: ");
  Serial.println(sensorValue);

  if (sensorValue > 400) {   // adjust threshold as needed
    Serial.println(">> Gas/Smoke Detected! <<");
  }

  delay(1000);
}

Usage Tips

• Higher sensor values indicate higher gas concentration.
• Adjust the threshold depending on your environment and calibration.
• The digital output (D0) can be used for simple detection logic.
• Ensure good ventilation and safety when testing with flammable gases.

MQ-2 vs MQ-3 vs MQ-7 – Gas Sensor Comparison

Feature	MQ-2	MQ-3	MQ-7
Main target gases	Combustible gases & smoke (LPG, propane, methane, hydrogen, etc.)	Alcohol/ethanol vapour (also benzine, smoke to lesser extent)	Carbon monoxide (CO) primarily
Typical operation voltage	5 V heater standard	5 V heater standard	Complex heating cycle (e.g., 5 V then 1.4 V low-heater mode) for CO detection
Specific usage notes	General-purpose gas and smoke sensor; wide detection scope but less selective	More selective toward alcohol vapour; used in breathalyzers and alcohol detection systems	Specialised for CO; requires heating cycle and calibration for accurate measurement
Calibration & complexity	Relatively simple; heat up, read analog output	Simple; read analog output, target is alcohol so environment matters	More complex; proper heater cycling and careful calibration needed
Best for	Home/DIY gas leak & smoke detection projects	Projects detecting alcohol vapour (e.g., breath analysis, security systems)	Applications where CO detection is important (ventilation, safety, industrial)
Considerations / trade-offs	Not very selective; may trigger for a range of combustible gases & smoke	May also respond to other vapours or solvents, not purely alcohol	Higher cost, more complex setup, slower response; careful calibration required

MQ Gas Sensors – Troubleshooting Tips

• False Readings: Ensure proper ventilation and avoid placing the sensor near strong fumes, alcohol, or other interfering gases if you want specific detection.
• Calibration Issues: Pre-heat the sensor for the recommended time (typically a few minutes to hours depending on sensor) before taking readings.
• Threshold Setting: Adjust threshold values in your code carefully; raw analog readings vary between sensors even of the same type.
• Environmental Factors: Temperature and humidity affect readings; use in stable environments or implement compensation if needed.
• Power Supply Stability: Use a stable 5 V supply; fluctuations can cause erratic readings.
• Sensor Age / Wear: MQ sensors degrade over time; if readings are inconsistent, consider replacing the sensor.