How to Use MQ-5 : Examples, Pinouts, and Specs

The MQ-5 Gas Sensor, manufactured by Tengxing (Part ID: Gas Sensor), is a versatile and reliable sensor designed to detect various gases, including natural gas, LPG (liquefied petroleum gas), and other combustible gases. It operates on the principle of resistive change in the presence of gas, providing an analog output proportional to the gas concentration. This sensor is widely used in applications such as gas leak detection, air quality monitoring, and safety systems in industrial and domestic environments.

• Gas leak detection in homes and industries
• Air quality monitoring systems
• Safety alarms for combustible gases
• IoT-based environmental monitoring systems

1. Power Supply: Connect the VCC pin to a 5V DC power source and the GND pin to the ground.
2. Analog Output: Connect the AOUT pin to an analog input pin of a microcontroller (e.g., Arduino) to read the gas concentration as a voltage signal.
3. Digital Output: Optionally, connect the DOUT pin to a digital input pin of a microcontroller. The DOUT pin provides a high/low signal based on the gas concentration exceeding a preset threshold, which can be adjusted using the onboard potentiometer.
4. Preheat Time: Allow the sensor to preheat for at least 24 hours before taking accurate readings.
5. Calibration: For precise measurements, calibrate the sensor in a known gas concentration environment.

• Ventilation: Ensure proper ventilation around the sensor to avoid saturation or false readings.
• Avoid Contaminants: Keep the sensor away from water, oil, and corrosive gases to prevent damage.
• Stable Power Supply: Use a stable 5V power source to avoid fluctuations in readings.
• Preheat Period: Always allow the sensor to preheat for the recommended time before use.
• Threshold Adjustment: Use the onboard potentiometer to set the desired gas concentration threshold for the digital output.

// MQ-5 Gas Sensor Example Code for Arduino UNO
// This code reads the analog output (AOUT) of the MQ-5 sensor and prints the
// gas concentration to the Serial Monitor.

const int analogPin = A0; // Connect AOUT pin of MQ-5 to Arduino A0
int sensorValue = 0;      // Variable to store the analog reading

void setup() {
  Serial.begin(9600); // Initialize serial communication at 9600 baud
  Serial.println("MQ-5 Gas Sensor Test");
}

void loop() {
  sensorValue = analogRead(analogPin); // Read the analog value from the sensor
  float voltage = sensorValue * (5.0 / 1023.0); // Convert to voltage (0-5V)
  
  // 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
}

1. No Output or Incorrect Readings:

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

2. Fluctuating Readings:

   • Cause: Unstable power supply or environmental interference.
   • Solution: Use a regulated 5V power source and ensure proper ventilation.

3. Digital Output Not Triggering:

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

4. Sensor Not Responding to Gas:

   • Cause: Sensor contamination or damage.
   • Solution: Ensure the sensor is clean and free from contaminants. Replace if necessary.

• Q: Can the MQ-5 detect gases other than natural gas and LPG?

  • A: Yes, the MQ-5 can detect other combustible gases, but its sensitivity varies depending on the gas type.

• Q: How do I calibrate the MQ-5 sensor?

  • A: Expose the sensor to a known concentration of gas and adjust the load resistance (RL) or potentiometer to match the expected output.

• Q: Can I use the MQ-5 with a 3.3V microcontroller?

  • A: The MQ-5 requires a 5V power supply for the heater. However, you can use a voltage divider or level shifter to interface the analog output with a 3.3V microcontroller.

• Q: How long does the MQ-5 sensor last?

  • A: The sensor typically lasts for several years under normal operating conditions, but its sensitivity may degrade over time.

By following this documentation, users can effectively integrate the MQ-5 Gas Sensor into their projects and ensure reliable performance.