Interface MQ2 Gas Sensor with Arduino

Introduction

The MQ-2 gas sensor is an essential tool for detecting gases like LPG, methane, and smoke, making it ideal for safety and air quality projects. It works by measuring changes in electrical resistance based on gas concentration, outputting an analog signal that corresponds to detected levels. This guide will help you connect the MQ-2 to an Arduino and read gas or smoke concentration values accurately.

Safety Warning

This experiment involves detecting gas with the MQ-2 sensor, which may require using a lighter or other gas sources. It is crucial to prioritize safety during this experiment.

• Children should only conduct this activity under the supervision of an adult.
• Keep flammable materials and ignition sources away from the sensor and workspace.
• Always have an adult handle any ignition sources, such as a lighter, to minimize risks.

Required Components

• Arduino Board (e.g., Arduino Uno)
• MQ2 Gas Sensor
• Jumper Wires
• Breadboard (optional)

Pinout

Circuit Diagram / Wiring

• MQ2 SENSOR VCC → 5V (Arduino)
• MQ2 SENSOR GND → GND (Arduino)
• MQ2 SENSOR AO (Analog Output) → Pin A0 (Arduino)

Programming With Arduino

• Copy the provided code into your Arduino IDE.

// Define the analog pin connected to the MQ-2 sensor
const int mq2Pin = A0; // Analog pin A0 for MQ-2 sensor output
const int detectionThreshold = 600; // Set a threshold value for gas detection

void setup() {
  Serial.begin(9600); // Initialize serial communication
}

void loop() {
  int sensorValue = analogRead(mq2Pin); // Read analog value from MQ-2 sensor

  // Check if the sensor value exceeds the threshold
  if (sensorValue > detectionThreshold) {
    Serial.println("Gas Detected!"); // Print message if gas is detected
  } else {
    Serial.println("No Gas Detected!"); // Print message if no gas is detected
  }

  delay(1000); // Delay before taking the next reading
}

Explanation

• mq2Pin: Defines the analog pin connected to the MQ-2 sensor.
• detectionThreshold: A threshold value set to 300 (you may need to adjust this value based on your calibration and testing).
• analogRead(mq2Pin): Reads the analog value from the MQ-2 sensor.
• if (sensorValue > detectionThreshold): Checks if the read sensor value is greater than the threshold to determine gas presence.
• Serial.println("Gas Detected!"): Prints a message when gas is detected.
• Serial.println("No Gas Detected!"): Prints a message when no gas is detected.
• delay(1000): Pauses for 1 second before taking the next reading.

Adjustments

• You may need to adjust the detectionThreshold based on your specific sensor’s behavior and the type of gases you want to detect.
• Monitor the Serial Monitor output to determine what sensor values correspond to gas presence and adjust the threshold accordingly.

Testing and Troubleshooting

• Verify Connections: Ensure the MQ-2 sensor is properly connected to the Arduino, with VCC, GND, and the analog pin (A0) connected correctly.
• Check Serial Monitor: Open the Serial Monitor to see the gas concentration readings in PPM. If no values appear, check the code and wiring.
• Sensor Calibration: Adjust calibration values like RS_air and RL for better accuracy based on specific conditions or gas types.
• Voltage Range: If readings seem off, confirm that the analog pin is receiving the expected voltage (0-5V) from the sensor.