An automatic watering controller with AT89S52 single-chip microcomputer was developed. According to the moisture condition detected by soil moisture sensor, the system could control the watering quantity by using fuzzy control rules to limit opening and closing time of electromagnetic valve of the irrigation system. Mamdani inference algorithm was employed as fuzzy control model for this closed-loop control system. Soil moisture sensor was put into the substrate for roots growth to obtain moisture information and used as the input. By comparing the water needed for plant growth, water demand and the electromagnetic valve opening and closing time was determined by the single-chip microcomputer program. Centroid method of defuzzification was used to determine the quantitative level of watering quantity. This fuzzy controller was designed by MATLAB fuzzy logic toolbox. The control system was simulated by Simulink. Simulation results show that this control method has good stability.
