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Lesson 02: Capacitive Soil Moisture Module

In this lesson, you’ll learn how to use the Raspberry Pi Pico W to measure soil moisture levels using a capacitive sensor and an ADC (Analog to Digital Converter). This beginner-friendly project will introduce you to handling analog signals in MicroPython.

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
Capacitive Soil Moisture Module	BUY
Breadboard	BUY

Wiring

../_images/Lesson_02_Capacitive_Soil_Moisture_Module_bb.png

Code

from machine import ADC
import time

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

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

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

Code Analysis

Importing Libraries:
```
from machine import ADC
import time
```
ADC Setup:
```
sensor_AO = ADC(26)
```
This code initializes an ADC object on GPIO pin 26. ADC is used to convert analog signals (from analog sensors) to digital data that the microcontroller can process.
Reading Sensor Data in a Loop:
```
while True:
    value = sensor_AO.read_u16()
    print("AO:", value)
    time.sleep_ms(200)
```
The while True loop runs indefinitely, constantly reading data from the sensor. The read_u16() method reads the analog value and converts it to a 16-bit unsigned integer. The print statement displays this value. The time.sleep_ms(200) causes the loop to wait for 200 milliseconds before reading the sensor value again, preventing excessive data readings and console output.