Microcontroller­-based irrigation controller

Abstract

A microcontroller-­based irrigation controller system was designed, constructed and tested. The system uses a gypsum block as sensor. The change in resistance of the gypsum block was used as the basis for measuring the moisture content of the soil.
The gypsum block was interfaced to an ATMega16 microcontroller through its on­-chip Analog to Digital Converter. The voltage output of the gypsum block sensor circuit was converted to actual soil moisture content by the ADC and software program of the microcontroller.
The gypsum block sensor was calibrated using clay loam soil from wilting point to saturation point. Irrigation schedule was controlled in two ways: by measuring the change in moisture content of the soil and by utilizing a timer to control the time of irrigation.
The testing of the instrument was also divided into two parts. The first was conducted by setting different start times, durations and time intervals of ON and OFF-­time of the system. The second testing was done by simulating the voltage input to the ADC using a variable potential divider.
The results showed that the system turned the irrigation valve ON at the time set by the user or at moisture content of 22% or lower. The controller turned the valve OFF after the duration set by the user was attained.