Soil moisture detection circuit

Scientific farming requires controlling soil moisture. The soil moisture test circuit can roughly judge the soil moisture. It uses LED seven-color light -emitting
diodes to indicate the relative humidity of the soil. It is very convenient and fun to use. -
    (1) Circuit composition and working principle The soil moisture tester circuit consists of a humidity sensor detection probe, transistor VT, diodes VD1-
VD6, light-emitting diodes LED1-LED7, potentiometer RP, power switch S and 9V power supply, as shown in the figure .
    When the humidity detection probe is not inserted into the soil or the soil is too dry, VT and VD1-VD6 are in cut-off state, and LEDl-LED7 do not
emit light. When the soil has a certain humidity, the moisture in the soil makes the resistance between the two electrodes of the humidity detection probe smaller, VT is turned on, LED1 ~
LED7 light up sequentially, emitting seven colors of brown, red, orange, yellow, green, blue, and purple in sequence. The greater the humidity, the stronger the conduction ability of VT, and
the greater the number of light-emitting diodes that are lit. According to the number of light-emitting diodes that light up, the humidity of the soil is indicated.
    (Z) Select RP to use synthetic film resistors for winning parts. VD1-VD6 all use 2CP11 silicon ordinary diodes. LED1— LED 7
all use 0\>3mm high-brightness light-emitting diodes.