[tutorial] ESP32 Soil Hygometer

Here’s an other entry from the coding realm:

For Work I needed a way to quickly and cheaply measure the moisture of many soil samples in a row.
The internet offers a great variety of more or less well working sensors for tinkerers.

Since I had a Lilygo T-Display-S3 left over from the BrotBot project, I ordered such a sensor, fixed it as described and combined it with the T-Display.

Software-wise I implemented the following functions:

• Read ADC raw value
• Convert this value into rel humidity (hard coded linar regression)
• Write values into a csv file on a SPIFFS file system
• Transfer values via serial connection
• Delete saved values
• Low battery warning
• Deep sleep, when not in use

Calibration of the sensor has to be performed externally and the values for linear regression have to be flashed onto the device each time. In a future version of the software, I want to implement a calibration function that runs right on the device.

To be able to handle the devide nicely, and to stop all the cables from dangling, I designed a case for the T-Display and battery in FreeCad. The senor will be connected via header, to be able to switch it out easily.

Source code and 3D files can be downloaded HERE.
Die deutsche Version des Artikels gibt es HIER.