MQ9 - CO and Combustible Gas Sensor Module

The MQ9 Gas Sensor Module is a versatile sensor used to detect Carbon Monoxide (CO), Methane (CH₄), and LPG gases. It provides both analog and digital outputs, making it suitable for gas leak detection and air quality monitoring. The sensor requires a short warm-up time and is ideal for use in safety alarms and IoT-based environmental monitoring systems.

Technical Specifications:

• Operating Voltage: 5V DC
  
• Gases Detected: CO (Carbon Monoxide), CH₄ (Methane), LPG
  
• Detection Range: 10 – 1000 ppm (CO), 300 – 10,000 ppm (CH₄, LPG)
  
• Analog Output (A0): Varies with gas concentration
  
• Digital Output (D0): HIGH/LOW (based on threshold knob)
  
• Heater Power: ~900 mW
  
• Warm-up Time: 2 – 5 minutes (for stable readings)

Pinouts:

Connection with Arduino:

Module	Arduino UNO
VCC	5V
GND	GND
A0	A0
D0	D2(Optional)

 

Sample code:

Analog reading:

int mq9Pin = A0;  // Analog output of MQ9 connected to Arduino A0

void setup() {
  Serial.begin(9600);  // Start Serial Monitor
}

void loop() {
  int gasValue = analogRead(mq9Pin);  // Read analog value from sensor
  Serial.print("Gas Level (CO/CH4/LPG): ");
  Serial.println(gasValue);           // Display gas level
  delay(1000);  // Delay 1 second
}

Alert with a Buzzer if Gas is Detected

int mq9Pin = A0;         // Analog pin
int buzzerPin = 8;       // Buzzer connected to digital pin 8
int threshold = 400;     // Set based on testing

void setup() {
  Serial.begin(9600);
  pinMode(buzzerPin, OUTPUT);
}

void loop() {
  int gasLevel = analogRead(mq9Pin);
  Serial.print("Gas Level: ");
  Serial.println(gasLevel);

  if (gasLevel > threshold) {
    digitalWrite(buzzerPin, HIGH);  // Turn on buzzer
  } else {
    digitalWrite(buzzerPin, LOW);   // Turn off buzzer
  }
  delay(500);
}