ESP capacitive soil moisture sensor

About

This code is for testing / using capacitive soil moisture sensors with ESP based boards (ESP32 / ESP8266) in Arduino IDE. It provides functions for getting calibration values and displays the information via 20x4 LCD and if enabled via serial monitor.

Important

• You need to gather calibration data first to measure soil
• Needs to be calibrated for every sensor / ESP combination (ESP8266 has different ADC values than ESP32)
• Probably also needs to be calibrated for different power sources

Usage

Use	Function name
Measure dry calibration value (sensor in air) -> modify airVal to this value	measureAir();
Measure wet calibration value (sensor in water) -> modify waterVal to this value	measureWater();
Measure soil moisture based on calibration values gathered with the above functions	measureSoil();
Get raw values for debugging purposes	rawVals();

Hardware

• ESP8266 (NodeMCU V3)
• Capacitive soil moisture sensor v1.2
• 20x4 2004A blue LCD (HD44780) with I2C adapter module

Pinout

ESP8266	Sensor
3,3V	VCC
GND	GND
AD0	AOUT
ESP8266	LCD
5V	VCC
GND	GND
D2	SDA
D1	SCL

Arduino libraries

The following library is needed to be able to use this code:

Library	URL
LCD_I2C	https://gitlab.com/tandembyte/LCD_I2C

License

The ESP capacitive soil moisture sensor project by Dominik Künne is licensed under CC BY-NC 4.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc/4.0

This project uses code from:

• how2electronics.com: Example code for sensor and LCD (https://how2electronics.com/interface-capacitive-soil-moisture-sensor-arduino/)
• tandembyte/LCD_I2C: Library (https://gitlab.com/tandembyte/LCD_I2C/-/tree/master)

Please see the LICENSE file for details.

ToDos

• WLAN connection
• MQTT
• Offline calibration via buttons