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Lesson 04: Gas Sensor Module (MQ-2)

In this lesson, you’ll learn how to use the Raspberry Pi Pico W to read data from a gas sensor module (MQ-2) using MicroPython. We’ll guide you through setting up an ADC on GPIO pin 26 to process analog signals from the MQ-2 sensor. You’ll gain practical experience in continuously monitoring and printing sensor data to understand the presence of gases in the environment.

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 Pico W	BUY
Gas/Smoke Sensor Module (MQ2)	BUY
Breadboard	BUY

Wiring

Code

import machine
import utime

# Initialize an ADC object on GPIO pin 26.
# This is typically used for reading analog signals.
mq2_AO = machine.ADC(26)

# Continuously read and print sensor data.
while True:
    value = mq2_AO.read_u16()  # Read and convert analog value to 16-bit integer
    print("AO:", value)  # Print the analog value

    utime.sleep_ms(200)  # Wait for 200 milliseconds before the next read

Code Analysis

1. Importing Libraries:

   The code begins by importing necessary libraries: machine for hardware interactions, and utime for handling time-related tasks.

   import machine
   import utime
   

2. Initializing the MQ-2 Sensor:

   An ADC object is created on GPIO pin 26 to read analog signals from the MQ-2 sensor. The MQ-2 sensor outputs an analog signal which varies with the concentration of gas in the air.

   mq2_AO = machine.ADC(26)
   

3. Reading Sensor Data in a Loop:

   The main loop of the program continuously reads the analog value from the sensor. The read_u16 method is used to read the analog value and convert it to a 16-bit integer. This value is then printed out. The loop includes a delay (utime.sleep_ms(200)) to wait for 200 milliseconds before reading the sensor value again. This delay is crucial to prevent overwhelming the sensor and the microcontroller with rapid readings.

   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.

   while True:
       value = mq2_AO.read_u16()  # Read and convert analog value to 16-bit integer
       print("AO:", value)  # Print the analog value
       utime.sleep_ms(200)  # Wait for 200 milliseconds before the next read