Interfacing MQ-4 Methane Gas Sensor with Arduino

MQ-4 Methane Gas Sensor

The MQ-4 Gas Sensor is designed to detect methane (CNG) and natural gas in the air. It’s commonly used in gas leakage detection systems in homes, vehicles, and industrial environments.

Working Principle of MQ-4 Gas Sensor

The MQ-4 sensor operates by measuring the conductivity change in its sensing material when exposed to gas. The sensor’s internal heater provides the necessary temperature, allowing the tin dioxide (SnO₂) layer to react with methane molecules, triggering a measurable change in resistance.

Types of Gas Sensors

Semiconductor Gas Sensor

  • Heats up the sensor element using an internal heater.
  • Gas molecules interact with the sensing material.
  • Changes in resistance are converted into readable signals.

Infrared Gas Sensor

  • Emits IR light through the gas sample.
  • Detects absorption at specific wavelengths.
  • Calculates gas concentration from the absorption data.

Requirements

1. Arduino

2. MQ-4 Gas Sensor Module

3. 10k ohm resistor (optional for analog smoothing)

4. Jumper wires

Pin Configuration of MQ-4 Gas Sensor

MQ-4 Sensor Module

  • VCC: Connect to +5V on Arduino.
  • GND: Connect to GND on Arduino.
  • DO: Digital output – HIGH or LOW based on gas threshold.
  • AO: Analog output – gives variable voltage depending on gas concentration.

Wiring the MQ-4 Gas Sensor to Arduino

To connect the MQ-4 to Arduino, wire VCC to 5V and GND to GND. The AO pin connects to an analog input to measure gas concentration, while the DO pin can trigger alarms when gas exceeds a set limit.

Algorithm

  1. Initialize Components

    • Connect the MQ-4 sensor’s VCC and GND to Arduino’s +5V and GND.
    • Connect AO to any analog input pin, e.g., A0. Optionally connect DO to a digital pin.

  2. Write the Code

    • Define sensor pins in the Arduino sketch.
    • Read analog values from the AO pin in the loop() function.
    • Use conditional logic if DO pin is used for threshold detection.

  3. Display Values or Trigger Alarms

    • Print gas values to the serial monitor for monitoring.
    • Trigger a buzzer or LED when gas concentration exceeds safe limits.

  4. Test the Project

    • Upload the code to the Arduino.
    • Expose the sensor to a small amount of gas and observe the readings or alarm behavior.
1// Arduino Code to Interface MQ-4 Gas Sensor (Detects Methane/CNG, Natural Gas)
2
3const int analogPin = A0;     // AOUT connected to A0 for analog gas readings
4const int digitalPin = 2;     // DOUT connected to D2 for threshold-based detection
5const int ledPin = 13;        // Onboard LED for alert indication
6
7void setup() {
8  Serial.begin(9600);              // Start serial communication at 9600 baud
9  pinMode(digitalPin, INPUT);      // DOUT is an input from the sensor
10  pinMode(ledPin, OUTPUT);         // Configure the LED pin as output
11  Serial.println("MQ-4 Gas Sensor Initialized...");
12}
13
14void loop() {
15  // Read the analog gas concentration value
16  int analogValue = analogRead(analogPin);  // Read the analog signal (0-1023)
17  float voltage = analogValue * (5.0 / 1023.0); // Convert to voltage
18
19  // Print values to the Serial Monitor
20  Serial.print("Analog Value: ");
21  Serial.print(analogValue);
22  Serial.print(" | Voltage: ");
23  Serial.print(voltage);
24  Serial.println(" V");
25
26  // Optional: Check digital output for gas threshold detection
27  int gasDetected = digitalRead(digitalPin);
28
29  if (gasDetected == LOW) {
30    // When gas exceeds threshold, DOUT goes LOW
31    digitalWrite(ledPin, HIGH);  // Turn ON LED to indicate gas presence
32    Serial.println(" Methane or Natural Gas Detected!");
33  } else {
34    digitalWrite(ledPin, LOW);   // Turn OFF LED if no gas detected
35  }
36
37  delay(1000); // Wait for 1 second before taking the next reading
38}
39

Applications of MQ-4 Gas Sensors

  • Home gas leak detection systems
  • Automotive CNG safety systems
  • Industrial gas monitoring
  • Smart kitchen safety
  • IoT-based air quality solutions
  • Environmental monitoring devices

Conclusion

Integrating the MQ-4 Gas Sensor with Arduino enables real-time methane and natural gas detection for safety-focused applications. Its ease of use makes it a valuable tool in smart systems and DIY safety setups.