How to Use MQ-8 SENSOR HYDROGEN: Examples, Pinouts, and Specs

The MQ-8 sensor is an electronic device designed to detect the presence of hydrogen gas (H2) in the air. It is widely used in various applications such as hydrogen gas leak detection systems, hydrogen storage units, and safety monitoring in environments where hydrogen is produced or used. The sensor operates on the principle that the conductivity of tin dioxide (SnO2) changes with the concentration of hydrogen gas in the air, providing a means to measure the gas concentration.

• Target Gas: Hydrogen (H2)
• Detection Range: 100ppm to 10,000ppm
• Preheat Duration: 20 minutes (typical)
• Supply Voltage: 5V DC ±0.1V
• Heating Voltage: 5V ±0.1V (High), 1.5V (Low)
• Load Resistance: Adjustable
• Heater Resistance: 31Ω ± 3Ω (at room temperature)
• Heater Power Consumption: Approx. 800mW
• Operating Temperature: -10°C to 50°C
• Humidity Range: 95% RH or less (non-condensing)

1. Power Supply: Connect the VCC pin to a 5V power supply and the GND pin to the ground.
2. Analog Output (AO): Connect the AO pin to an analog input on your microcontroller to read the gas concentration as an analog voltage.
3. Digital Output (DO): The DO pin can be connected to a digital input on your microcontroller. It outputs a low level when the hydrogen concentration reaches a certain threshold, which can be adjusted using the onboard potentiometer.

• Calibration: The MQ-8 sensor requires calibration to ensure accurate readings. Expose the sensor to a known concentration of hydrogen gas and adjust the onboard potentiometer until the desired output is achieved.
• Preheating: Before taking measurements, allow the sensor to preheat for at least 20 minutes to stabilize its readings.
• Environmental Factors: Avoid using the sensor in environments with high concentrations of other gases or volatile organic compounds (VOCs) that may interfere with the sensor's readings.
• Safety: Hydrogen is a highly flammable gas. Ensure proper safety measures are in place when using the sensor in potentially hazardous conditions.

// MQ-8 Hydrogen Gas Sensor Example Code
int analogPin = A0; // Analog input pin connected to AO pin of MQ-8
int digitalPin = 2; // Digital input pin connected to DO pin of MQ-8
int sensorValue = 0; // Variable to store the sensor value

void setup() {
  pinMode(digitalPin, INPUT); // Set the digital pin as input
  Serial.begin(9600); // Start serial communication at 9600 baud rate
}

void loop() {
  sensorValue = analogRead(analogPin); // Read the analog value from sensor
  Serial.print("Hydrogen concentration (analog): ");
  Serial.println(sensorValue); // Print the analog reading

  if (digitalRead(digitalPin) == LOW) { // Check if the digital output is LOW
    Serial.println("Hydrogen level is above the threshold!");
  } else {
    Serial.println("Hydrogen level is below the threshold.");
  }

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

• Inaccurate Readings: If the sensor provides inconsistent or inaccurate readings, ensure that it has been properly calibrated and that there are no interfering gases present.
• No Response: Check the power supply and wiring connections if the sensor shows no response. Ensure the sensor has been preheated sufficiently.

• Calibration: Perform calibration in a controlled environment where the hydrogen concentration is known.
• Sensor Cleaning: Periodically clean the sensor's surface with alcohol to remove any contaminants that may affect its performance.
• Avoid Contaminants: Keep the sensor away from dust, oil vapor, and other contaminants that can coat the sensing material and affect readings.

Q: How long does the MQ-8 sensor last? A: The lifespan of the MQ-8 sensor can vary depending on usage and environmental conditions, but it typically lasts for several years with proper maintenance.

Q: Can the MQ-8 sensor detect other gases? A: While the MQ-8 sensor is designed for hydrogen gas detection, it may show some sensitivity to other gases. It is important to calibrate the sensor specifically for hydrogen gas detection to avoid false readings.

Q: Is the MQ-8 sensor suitable for outdoor use? A: The MQ-8 sensor can be used outdoors, but it should be protected from extreme temperatures, humidity, and direct sunlight to ensure accurate readings.