After several iterations and data collection, I've created a PCB to neatly connect the Raspberry to the relays/sensors which includes 4 analog inputs to connect analog sensors (0-5v). I called it the "Automatio/Irrigation Hat". I've tested it with several sensors including the analog capacitive hygrometers. Using the analog inputs, among the other things, I can now verify and chart the voltage level of the battery of my Solar irrigation system.
The board can be connected to up to 16 relays, which can be irrigation lines or other actuators.
The Board is available for sale at the following link:
https://www.tindie.com/products/angelova/automationirrigation-hat/
Buying the board can be a great way to contribute to this project.
NOTE: the hydrosys4 project can still be implemented without any custom board, all the supported hardware configurations/connections are described in the website.
Thank you Angelo, yes I have all the parts so will make the changes as per the schematic.
Yes its interesting how the rain sensor acts as a virtual tipping bucket, turning on and off with rain showers during the day and eventually filling the bucket and switching off for a day, this is user configurable on the rain sensor.