How to Use MQ-4: Examples, Pinouts, and Specs

The MQ-4 gas sensor, manufactured by DF Robot, is a highly sensitive and reliable component designed to detect methane (CH₄) and natural gas concentrations in the air. It operates on the principle of resistive change, where the sensor's resistance varies in response to the presence of target gases. The MQ-4 provides an analog output signal proportional to the gas concentration, making it suitable for a wide range of applications.

• Gas leak detection in residential and industrial environments
• Methane monitoring in mining and oil industries
• Environmental air quality monitoring
• Smart home safety systems
• IoT-based gas detection systems

The MQ-4 sensor is designed for ease of use and integration into various electronic systems. Below are its key technical details:

The MQ-4 sensor typically comes with four pins or terminals. Below is the pinout description:

The MQ-4 gas sensor is straightforward to use in a circuit. Follow the steps below to integrate it into your project:

1. Power Supply: Connect the VCC pin to a 5V DC power source and the GND pin to ground.
2. Analog Output: Connect the AOUT pin to an analog input pin of your microcontroller (e.g., Arduino UNO) to read the gas concentration.
3. Digital Output (Optional): If using the DOUT pin, connect it to a digital input pin of your microcontroller. Adjust the onboard potentiometer to set the gas concentration threshold for the digital output.

• Preheating: Allow the sensor to preheat for at least 24 hours before taking accurate measurements. This ensures the internal heater stabilizes.
• Calibration: For precise measurements, calibrate the sensor in a known gas concentration environment.
• Ventilation: Ensure proper ventilation around the sensor to avoid saturation and improve response time.
• Load Resistor: Use a load resistor (RL) of 10 kΩ for typical applications. Adjust as needed for your specific use case.

Below is an example of how to use the MQ-4 sensor with an Arduino UNO to read analog values:

// MQ-4 Gas Sensor Example Code
// This code reads the analog output of the MQ-4 sensor and prints the value
// to the Serial Monitor. Ensure the sensor is connected to the correct pins.

const int MQ4_AOUT_Pin = A0; // Connect AOUT pin of MQ-4 to Arduino analog pin A0

void setup() {
  Serial.begin(9600); // Initialize serial communication at 9600 baud
  pinMode(MQ4_AOUT_Pin, INPUT); // Set the AOUT pin as input
}

void loop() {
  int sensorValue = analogRead(MQ4_AOUT_Pin); // Read the analog value from MQ-4
  float voltage = sensorValue * (5.0 / 1023.0); // Convert to voltage (0-5V range)

  // Print the sensor value and voltage to the Serial Monitor
  Serial.print("Sensor Value: ");
  Serial.print(sensorValue);
  Serial.print(" | Voltage: ");
  Serial.print(voltage);
  Serial.println(" V");

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

• Avoid exposing the sensor to high concentrations of corrosive gases, as this may damage the sensing element.
• Place the sensor in a stable environment to minimize noise and fluctuations in readings.
• Use a decoupling capacitor (e.g., 0.1 µF) between VCC and GND to reduce power supply noise.

1. How long does the MQ-4 sensor last?

   • The sensor has a typical lifespan of 5 years under normal operating conditions.

2. Can the MQ-4 detect gases other than methane?

   • While optimized for methane, the MQ-4 may respond to other combustible gases, but with reduced accuracy.

3. Why is preheating necessary?

   • Preheating stabilizes the internal heater and ensures accurate and consistent readings.

4. Can I use the MQ-4 with a 3.3V microcontroller?

   • The MQ-4 requires a 5V power supply for the heater. Use a level shifter or voltage divider for compatibility with 3.3V systems.

By following this documentation, you can effectively integrate the MQ-4 gas sensor into your projects for reliable methane and natural gas detection.