The MQ-2 Gas Sensor

 

 

The MQ-2 smoke sensor is the one in the following figure:

The mq 2 gas 1

 

 

The MQ-2 smoke sensor is sensitive to smoke and to the following flammable gases:

 

  • LPG
  • Butane
  • Propane
  • Methane
  • Alcohol
  • Hydrogen

 

 

The resistance of the sensor is different depending on the type of the gas.

The smoke sensor has a built-in potentiometer that allows you to adjust the sensor digital output (D0) threshold. This threshold sets the value above which the digital pin will output a HIGH signal.

 

 

 

How does it work?

 

 

The voltage that the sensor outputs changes accordingly to the smoke/gas level that exists in the atmosphere. The sensor outputs a voltage that is proportional to the concentration of smoke/gas.

 

In other words, the relationship between voltage and gas concentration is the following:

  • The greater the gas concentration, the greater the output voltage
  • The lower the gas concentration, the lower the output voltage

 

  • The mq 2 gas 2

 

The output can be an analog signal (A0) that can be read with an analog input of the Arduino or a digital output (D0) that can be read with a digital input of the Arduino.

 

Pin Wiring

 

The MQ-2 sensor has 4 pins.

 

Pin

Wiring to Arduino Uno

A0

Analog pins

D0

Digital pins

GND

GND

VCC

5V

 

 

Example: Gas Sensor with Arduino

 

In this example, you will read the sensor analog output voltage and when the smoke reaches a certain level, it will make sound a buzzer and a red LED will turn on.

When the output voltage is below  that level, a green LED will be on.

 

 

Parts needed:

 

So, for this example, you’ll need:

DOWNLOAD FREE GUIDE: Ultimate Guide for Arduino Modules and Sensors

The mq 2 gas 3

 

  • 1 x MQ-2 gas sensor 
  • Arduino UNO 
  • 1x Breadboard 
  • 1 x red LED
  • 1 x green LED
  • 1 x buzzer
  • 3 x 220Ω resistor
  • Jumper wires

 

You can use the preceding links or go directly to MakerAdvisor.com/tools to find all the parts for your projects at the best price!

 

 

Schematics

 

Follow these schematics to complete the project:

The mq 2 gas 4

 

Code

 

Upload the following sketch to your Arduino board (feel free to adjust the variable sensorThres with a different threshold value):

 

/*******

 

 All the resources for this project:

 http://randomnerdtutorials.com/



*******/



int redLed = 12;

int greenLed = 11;

int buzzer = 10;

int smokeA0 = A5;

// Your threshold value

int sensorThres = 400;



void setup() {

  pinMode(redLed, OUTPUT);

  pinMode(greenLed, OUTPUT);

  pinMode(buzzer, OUTPUT);

  pinMode(smokeA0, INPUT);

  Serial.begin(9600);

}



void loop() {

  int analogSensor = analogRead(smokeA0);



  Serial.print("Pin A0: ");

  Serial.println(analogSensor);

  // Checks if it has reached the threshold value

  if (analogSensor > sensorThres)

  {

    digitalWrite(redLed, HIGH);

    digitalWrite(greenLed, LOW);

    tone(buzzer, 1000, 200);

  }

  else

  {

    digitalWrite(redLed, LOW);

    digitalWrite(greenLed, HIGH);

    noTone(buzzer);

  }

  delay(100);

}

view raw    Projects/smoke_detector.ino

 

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