Pico Plant Water Sensor 3.3V Supply - Voltage Divider

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01:01:32

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.

published 3 years ago

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