Full project can be found here: https://github.com/Silverune/PicoPlant
V represents digital input to RPI Pico W on a GPIO port. Logic high is defined as +1.8V-3.3V. Experimentally found goes does to about +1.4.
Design parameters assume short-circuit will not exceed the 3.3 and when a 20K ohm load on the sensors should turn "OFF".
By essentially halving the voltage (3.3 / 2 = +1.65V) we get the threshold for logical ON / OFF. Design simply matches the second resistance to the perceived resistance of the plant in a dry state, So assuming when on the threshold of dry there is 20K Ohms resistance, matched with an actual 20K resistor connected to GND.
Safer / cheaper design than previous. Easier to maintain as well.
