Design and Characterization of a Low-Cost Capacitive Soil Moisture Sensor System for IoT based Agriculture Applications

The global demand for food can be eliminated by precision farming. This research work proposes a low-cost IoT-enabled handy device to measure soil water content. Three different sensor probes are designed in COMSOL Multiphysics 5.4 and fabricated using PCB Technology. The designed sensor probes are calibrated to effectively measure moisture content for three different soil types (silt/sandy/clay). An electronic system has been programmed according to Optimized-Moisture-Value (OMV) algorithm to read and collect the soil moisture information. Three sensor probes, capacitance, and voltage responses are analyzed using linear fitting. It has been observed from the response data that model B's performance is better than the other two presented models in terms of soil moisture. The obtained goodness of fitness value for model B is around 0.999 for all the categories of soils. The electronic system is built around W78E054D and ESP8266 controllers. The W78E054D controller is used to excite the sensor probe with a signal having a frequency of 500 kHz. The IoT-enabled controller ESP8266 reads and collects the soil moisture data according to the OMV algorithm.