Overview
Things
Story

What is an MQ-2 Smoke Sensor
How does it Work
Pin Wiring

Published May 6, 2016 © LGPL

Smoke Detection using MQ-2 Gas Sensor

In this tutorial, we will learn how to detect Smoke and inflammable gases using an MQ-2 sensor.

BeginnerProtip30 minutes605,236

Things used in this project

Hardware components

Arduino UNO

Breadboard (generic)

MQ-2 Smoke detection sensor

Male/Female Jumper Wires

5 mm LED: Red

5 mm LED: Green

Buzzer

Resistor 221 ohm

Software apps and online services

Arduino IDE

Story

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.

What is an MQ-2 Smoke Sensor?

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

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 sensitivity according to how accurate you want to detect gas.

MQ-2 sensor

Sensor Pin-out details

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 greaterthe gas concentration,the greaterthe output voltage

The lowerthe gas concentration,the lowerthe output voltage

Working Mechanism

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

So, before jumping into the coding part, let's check whether we've assembled all the necessary hardware components.

Hardware Components

Kindly refer to the connection schematic attached below. After you've wired all the components properly, it's time to upload the necessary code.

Code

MQ-2 sensor code

/*******
 
 All the resources for this project:
 https://www.hackster.io/Aritro

*******/

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);
}

Credits

Aritro Mukherjee

4 projects • 370 followers

Enthusiastic about IOT , Robotics and Automation technologies

Smoke Detection using MQ-2 Gas Sensor