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Guide for MQ-2 Gas/Smoke Sensor with Arduino

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This guide shows how to build a smoke detector that beeps when it detects flammable gas or smoke.

The MQ-2 Gas Sensor

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

smoke sensor r

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) sensitivity according to how accurate you want to detect gas.

smoke sensor label

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 voltagesmokepicture

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:

DSC08397

Schematics

Follow these schematics to complete the project:

circuit

Code

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

Video demonstration

Watch this quick video demonstration to see this project in action:


I hope you found this guide useful.

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Thanks for reading,

-Rui Santos

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