SoilHumiditySensor

Project SoilHumiditySensor
Investigation of soil humidity sensors
Status	In progress
Contact	bertrik
Last Update	2019-05-12

Introduction

A number of types of soil humidity sensors exist. Many have the problem that the electrodes corrode.

For example, see this video by Andreas Spiess that compares a couple of types.

Hardware

It got these capacitive ones from Aliexpress.

I've connected it up as follows:

• probe GND (black) to Wemos D1 mini pin D5
• probe VCC (red) to Wemos D1 mini pin D0
• probe AOUT (yellow) to Wemos D1 mini pin A0

This way, the wire with the 3-pin connector can simply be plugged into the Wemos D1 mini, without having to modify the cable.

The software puts a low level on pin D5 (to emulate GND) and a high level on pin D0 (to emulate VCC). The idea is that the current is low enough for this trick to work.

Software

See my github repository.

The software takes a measurement at a regular interval and sends it over MQTT.