Farmland irrigation automatic control circuit a

The automatic irrigation control circuit can automatically irrigate crops according to the soil moisture. It can be widely used in state-owned farms, orchards,
greenhouse vegetable cultivation, greenhouse cultivation and sprinkler irrigation of vast farmland.
    (1) Circuit composition The automatic irrigation controller circuit consists of a soil moisture detection sensor, a Schmitt trigger , a monostable trigger, an LED display
circuit and a control execution circuit, as shown in Figure 8-2.
    The Schmitt trigger consists of four NAND gate integrated circuits 1C1-1C2, resistors Ri, Rz, capacitors Cl, c2, and potentiometer RP1.
    The monostable trigger is composed of IC 3~lC4, resistor R4, potentiometer RP2 and capacitor G.
    The LED display circuit is composed of transistor VT3, light-emitting diodes LED1, LED2 and resistors Rs~R7.
    The control execution circuit consists of resistor Ra, transistor VTI, VIII, relay K and diode. VI) Composition. ,
    (2) Working principle of the circuit: When the soil moisture is suitable, the electric value between the two probes of the humidity detection sensor is small, the input terminal of ici is at a
low potential, and the Schmitt trigger cannot be triggered. At this time, IC4 outputs a high level, causing VT1 and VT2 to cut off. K does not suction the table, the water pump motor
M does not work, and LED2 does not light up; at the same time, VT3 is turned on, and LED1 lights up, indicating that the soil moisture is suitable.
    When the soil is dry to a certain extent. When the resistance value between the two probes of the humidity sensor rises to a certain predetermined value, the Schmitt trigger is triggered
and flips. G provides a negative jump pulse to the monostable trigger, causing the monostable flip-flop to flip. , IC 4 outputs a low level, causing VT3
to cut off, and LED1 to go out; VT1 and VT2 are turned on, K is closed, the water pump is powered on, and irrigation starts, and LED2 lights up at the same time; indicating that the water pump motor
is operating normally.
  R'1 is used to control soil moisture and adjust its resistance. The timing of irrigation J can be determined based on the soil moisture. By adjusting the resistance of RP2,
the length of irrigation time can be adjusted.