Gas/Smoke Sensor Module (MQ2)¶

Introduction¶

The MQ-2 sensor is a versatile gas sensor capable of detecting a wide range of gases including alcohol, carbon monoxide, hydrogen, isobutene, liquefied petroleum gas, methane, propane, and smoke. It is popular among beginners due to its low cost and easy-to-use features.

Principle¶

The MQ-2 sensor works on the principle of resistance changes in the presence of different gases. When the target gas comes in contact with the heated MOS(Metal Oxide Semiconductor) material, it undergoes oxidation or reduction reactions that change the resistance of the MOS material. It is noteworthy that the MQ2 gas sensor is capable of detecting multiple gases, but lacks the ability to differentiate between them. This is a common characteristic of most gas sensors.

The sensor has a built-in potentiometer that allows you to adjust the sensor digital output (D0) threshold. When the concentration of gas in the air exceeds a certain threshold value, the resistance of the sensor changes. This change in resistance is then converted into an electrical signal that can be read by an Arduino board.

Usage¶

Hardware components

Arduino Uno R4 or R3 board * 1
Gas Sensor Module(MQ2) * 1
Jumper Wires

Circuit Assembly

Code¶

Code explanation¶

The first line of code is a constant integer declaration for the gas sensor pin. We use the analog pin A0 to read the output from the gas sensor.
```
const int sensorPin = A0;
```
The setup() function is where we initialize our serial communication at a baud rate of 9600. This is necessary to print the readings from the gas sensor to the serial monitor.
```
void setup() {
  Serial.begin(9600);  // Start serial communication at 9600 baud rate
}
```
The loop() function is where we continuously read the analog value from the gas sensor and print it to the serial monitor. We use the analogRead() function to read the analog value from the sensor. We then wait for 50 milliseconds before the next reading. This delay gives some breathing space for the serial monitor to process the data.
```
void loop() {
  Serial.print("Analog output: ");
  Serial.println(analogRead(sensorPin));  // Read the analog value of the gas sensor and print it to the serial monitor
  delay(50);                             // Wait for 50 milliseconds
}
```

Note

MQ2 is a heating-driven sensor that usually requires preheating before use. During the preheating period, the sensor typically reads high and gradually decreases until it stabilizes.

Additional Ideas¶

add a visual or auditory warning system (using LEDs or a buzzer) that triggers when gas concentrations exceed certain thresholds.

More Projects¶

Gas leak alarm