How to Use MQ-2: Examples, Pinouts, and Specs

The MQ-2 is a versatile gas sensor manufactured by Arduino, designed to detect a variety of gases such as LPG, propane, methane, and smoke. It operates on the principle of resistive change, where the sensor's resistance varies in the presence of target gases. This change is converted into an analog output, making it easy to interface with microcontrollers and other electronic systems.

• Gas leak detection in homes and industries
• Smoke detection in fire alarm systems
• Air quality monitoring
• IoT-based environmental monitoring systems
• Safety systems in automotive and industrial environments

The MQ-2 sensor is designed for ease of use and reliable performance. Below are its key technical details:

The MQ-2 sensor module typically has four pins. Below is the pinout and description:

The MQ-2 sensor is straightforward to use in a circuit. Follow the steps below to integrate it into your project:

1. Power the Sensor: Connect the VCC pin to the 5V pin on the Arduino UNO and the GND pin to the Arduino's GND.
2. Read Analog Output: Connect the AOUT pin to an analog input pin on the Arduino (e.g., A0).
3. Optional Digital Output: If you want to use the digital output, connect the DOUT pin to a digital input pin on the Arduino (e.g., D2). Adjust the onboard potentiometer to set the gas concentration threshold for triggering the digital output.

Below is an example of how to use the MQ-2 sensor with an Arduino UNO to read analog values and detect gas concentration:

// MQ-2 Gas Sensor Example Code
// This code reads the analog output of the MQ-2 sensor and prints the value
// to the Serial Monitor. Adjust the threshold value as needed for your application.

const int analogPin = A0;  // Pin connected to AOUT of MQ-2
const int digitalPin = 2;  // Pin connected to DOUT of MQ-2 (optional)
int sensorValue = 0;       // Variable to store analog reading

void setup() {
  Serial.begin(9600);      // Initialize serial communication
  pinMode(digitalPin, INPUT); // Set digital pin as input
}

void loop() {
  // Read the analog value from the sensor
  sensorValue = analogRead(analogPin);
  
  // Print the analog value to the Serial Monitor
  Serial.print("Analog Value: ");
  Serial.println(sensorValue);

  // Check the digital output (optional)
  if (digitalRead(digitalPin) == HIGH) {
    Serial.println("Gas concentration exceeded threshold!");
  }

  delay(1000); // Wait for 1 second before the next reading
}

• Preheat the Sensor: Allow the sensor to preheat for at least 24 hours before taking accurate measurements.
• Calibrate the Sensor: For precise gas concentration readings, calibrate the sensor in a known gas environment.
• Avoid High Humidity: Prolonged exposure to high humidity can affect the sensor's performance.
• Use a Load Resistor: Ensure the load resistor (RL) is properly selected based on your application. A typical value is 10 kΩ.
• Ventilation: Place the sensor in a well-ventilated area for accurate readings.

1. No Output or Incorrect Readings

   • Cause: Insufficient preheating time.
   • Solution: Allow the sensor to preheat for at least 24 hours before use.

2. Fluctuating Analog Values

   • Cause: Electrical noise or unstable power supply.
   • Solution: Use a decoupling capacitor (e.g., 0.1 µF) across the power supply pins.

3. Digital Output Not Triggering

   • Cause: Incorrect threshold setting on the potentiometer.
   • Solution: Adjust the potentiometer to set the desired gas concentration threshold.

4. Sensor Not Detecting Gas

   • Cause: Sensor placed in an unsuitable environment.
   • Solution: Ensure the sensor is exposed to the target gas and is within its operating temperature and humidity range.

Q1: Can the MQ-2 detect multiple gases simultaneously?
A1: Yes, the MQ-2 can detect multiple gases such as LPG, propane, methane, and smoke. However, it cannot differentiate between them.

Q2: How do I convert the analog output to gas concentration (ppm)?
A2: The analog output voltage can be mapped to gas concentration using the sensor's sensitivity curve provided in the datasheet. Calibration in a known gas environment is required for accurate results.

Q3: Can I use the MQ-2 with a 3.3V microcontroller?
A3: The MQ-2 is designed for 5V operation. If using a 3.3V microcontroller, you will need a level shifter or a 5V power source for the sensor.

Q4: How long does the MQ-2 last?
A4: The sensor has a typical lifespan of 2-3 years under normal operating conditions.