5.9 Measure Soil Moisture

This capacitive soil moisture sensor is different from most of the resistive sensors on the market, using the principle of capacitive induction to detect soil moisture.

By visually reading the values from the soil moisture sensor, we can gather information about the moisture level in the soil. This information is useful for various applications, such as automatic irrigation systems, plant health monitoring, or environmental sensing projects.

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
ESP32 Starter Kit	320+	ESP32 Starter Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
ESP32 WROOM 32E	BUY
ESP32 Camera Extension	-
Jumper Wires	BUY
Soil Moisture Module	BUY

Available Pins

• Available Pins

  Here is a list of available pins on the ESP32 board for this project.

  Available Pins

  IO14, IO25, I35, I34, I39, I36

• Strapping Pins

  The following pins are strapping pins, which affect the startup process of the ESP32 during power on or reset. However, once the ESP32 is booted up successfully, they can be used as regular pins.

  Strapping Pins

  IO0, IO12

Schematic

By inserting the module into the soil and watering it, the value read on I35 will decrease.

Wiring

Code

Note

• Open the 5.9_moisture.py file located in the esp32-starter-kit-main\micropython\codes path, or copy and paste the code into Thonny. Then, click “Run Current Script” or press F5 to execute it.

• Make sure to select the “MicroPython (ESP32).COMxx” interpreter in the bottom right corner.

from machine import ADC,Pin
import time

# create an ADC object acting on a pin
moisture = ADC(Pin(35, Pin.IN))

# Configure the ADC attenuation to 11dB for full range
moisture.atten(moisture.ATTN_11DB)

while True:

    # read a raw analog value in the range 0-4095
    value = moisture.read()
    print(value)
    time.sleep(0.05)

When the script runs, you will see the soil moisture value in the Shell.

By inserting the module into the soil and watering it, the value of the soil moisture sensor will become smaller.