Soil moisture sensor

There are two methods for using sensors to monitor soil moisture
:
1. Surface mount components are soldered, using a 3-pin interface with 3.3V power supply. The output frequency varies with temperature; it is approximately 25kHz when completely dry and around 16kHz when fully submerged in water. The required observation values ​​can be obtained using a microcontroller's counting or pulse width capture.
2. No surface mount components are soldered; they are directly connected to the microcontroller's capacitor button pins. Actual measurements are performed using an ESP32 microcontroller, resulting in stable observation values ​​with a reading range of approximately one level.
The features of this sensor are:
1. The sensing part inserted into the soil is constructed with an inner layer of 4-layer board, and the outer layer forms effective protection, so the copper foil will not be corroded.
2. It can be used with different types of microcontrollers.
 
Example reading
 
#MicroPython v1.20.0 on 2023-06-09; ESP32 module (spiram) with ESP32
from machine import TouchPad, Pin import timet = TouchPad(Pin(33))for i in range(1000): time.sleep(0.25) print("%d"%(t.read()))
 
The reading is about 140 in the air and about 70 when the two sides are pinched with fingers.