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 operating current of the probe 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.