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Lesson 04: Gas Sensor Module (MQ-2)

In this lesson, you will learn to use the MQ2 gas sensor with Raspberry Pi for gas detection. The course covers connecting the MQ2 sensor to the GPIO17 pin and programming the Raspberry Pi in Python to read the sensor output. You’ll understand how to detect gas presence, with a low signal from the sensor indicating the detection of gas. This project offers a practical introduction to sensor usage and Python scripting on the Raspberry Pi, ideal for beginners interested in environmental monitoring and safety applications.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name

ITEMS IN THIS KIT

LINK

Universal Maker Sensor Kit

94

Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction

Purchase Link

Raspberry Pi 5

BUY

Gas/Smoke Sensor Module (MQ2)

BUY

Breadboard

BUY

Wiring

../_images/Lesson_04_mq2_sensor_Pi_bb.png

Code

from gpiozero import DigitalInputDevice
import time

# Initialize MQ2 sensor on GPIO17
mq2 = DigitalInputDevice(17)

while True:
   # Detect gas presence (LOW signal indicates gas)
   if mq2.value == 0:
      print("Gas detected!")
   else:
      print("No gas detected.")

   # Delay between readings
   time.sleep(1)

Code Analysis

  1. Importing Libraries

    from gpiozero import DigitalInputDevice
import time

    This section imports necessary libraries. gpiozero is used for interacting with the GPIO pins of the Raspberry Pi, and time is used for handling time-related tasks such as delays.

  2. Initializing the MQ2 Sensor

    mq2 = DigitalInputDevice(17)

    Here, the MQ2 sensor is initialized as a digital input device on GPIO pin 17 of the Raspberry Pi. The DigitalInputDevice class from gpiozero is used for this purpose.

  3. Infinite Loop for Sensor Reading

    while True:
   if mq2.value == 0:
      print("Gas detected!")
   else:
      print("No gas detected.")
   time.sleep(1)

    In this segment:

    Note

    The DO pin on the MQ-2 sensor module indicates the presence of combustible gases. When the gas concentration exceeds the threshold value (as set by the potentiometer on the module), D0 becomes LOW; otherwise, it remains HIGH.

    • An infinite loop is created using while True. This loop will continue to run until the program is manually stopped.

    • Inside the loop, the value of the MQ2 sensor is checked using mq2.value. If the value is 0, it indicates the presence of gas, and “Gas detected!” is printed. Otherwise, “No gas detected.” is printed.

    • time.sleep(1) creates a delay of 1 second between each reading, reducing the frequency of the sensor checks and the output messages.