Design and implementation of automatic control system for sectional type subsurface drip irrigation in greenhouse

In order to fully draw out the potential of water saving and benefit increasing of the subsurface drip irrigation technology in greenhouse production, the authors developed an irrigation control system with the method of fuzzy controlling. In the design process of the system, the authors considered the climate characteristic of cold and drought in the northeast of China, and the greenhouse production scale and financial situation of the local farmers specially. The developed system consists of a controller, a magnetic valve, a soil humidity transducer, a water tank and a sectional sub irrigation ductwork. An 89S51 type chip microprocessor has been used as the controller, and the type of the A/D converter is ADC0804. An LCM display module is adopted as the indicator, and a 24c02 type chip as the external memory. The keyboard of the system consists of four spring type keys. There are two input signals to the two-dimension controller which are the errors of soil moisture and the change rate of the above error. There are also two output signals from the controller which are the open time of magnetic valve and the continuous open period of the above valve. Experiment results showed that the governing time needed 30－40 min to raise soil moisture by 10%, the control error was ≤3%, and the operation of the system was steady. The accuracy and rapidity of the system were able to satisfy the agriculture technical requirements.