MQ4 Methane Gas Sensor

Key Features

• Sensitive to methane and natural gas.
• Analog and digital output for easy integration.
• Adjustable sensitivity using a built-in potentiometer.
• Durable and stable for long-term use.

Specifications

• Operating Voltage: 3.3V–5V DC
• Operating Current: ~150 mA
• Detectable Gases: Methane (CH₄), natural gas.
• Output Types:
  • Analog Output (AO): Proportional to gas concentration.
  • Digital Output (DO): High/low signal based on the threshold set by the potentiometer.
• Sensitivity: Detects methane concentrations from 200 ppm to 10,000 ppm.
• Preheat Time: ~20 seconds for stable operation.
• Operating Temperature: -20°C to 50°C.

Pinout

1. VCC: Power supply (3.3V or 5V)
2. GND: Ground
3. DO: Digital output
4. AO: Analog output

Working Principle

The MQ4 sensor utilizes a SnO₂ (tin dioxide) sensing layer that has low conductivity in clean air. When exposed to methane or natural gas, the conductivity increases. This change is used to determine the concentration of gas in the environment.

Interfacing with Arduino

Hardware Setup

1. Connect VCC to the Arduino’s 5V pin.
2. Connect GND to the Arduino’s GND pin.
3. Connect AO (Analog Output) to an analog input pin (e.g., A0).
4. (Optional) Connect DO (Digital Output) to a digital input pin for threshold-based detection.

Sample Code

const int analogPin = A0; // Analog output pin
const int digitalPin = 2; // Digital output pin
int analogValue = 0;

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

void loop() {
  // Read analog value
  analogValue = analogRead(analogPin);
  
  // Print analog value (methane concentration)
  Serial.print("Analog Value: ");
  Serial.println(analogValue);

  // Check digital output
  if (digitalRead(digitalPin) == HIGH) {
    Serial.println("Methane concentration exceeded threshold!");
  }
  
  delay(1000);
}

Calibrating the Sensor

1. Preheating: Allow the sensor to warm up for at least 24 hours before precise calibration.
2. Adjusting Sensitivity: Use the built-in potentiometer to set the desired digital threshold.
3. Mapping Analog Values: Expose the sensor to known methane concentrations and record the analog values to create a calibration curve.

Applications

• Methane and natural gas leak detection.
• Industrial safety systems.
• Smart home gas detection systems.
• Environmental monitoring for methane emissions.
• IoT-based gas detection and alert systems.