The soil moisture level is one of the critical aspects, which controls the quality of the grapes grown in vineyards. The main objective of this research is to investigate the development of a low cost soil moisture sensor, which can be used in a ZigBee mesh network.
ZigBee is a new mesh networking standard, which places emphasis on low cost sensor networks and energy conservation. The development focus for ZigBee is remote monitoring and control applications.
Manufacturers are still improving their ZigBee devices and ZigBee software stacks. The ZigBee based Texas Instruments CC2430 microcontroller was selected as the wireless sensor hardware for this research. Micro climate weather station was designed to monitor the vineyard environmental data like temperature, pressure, sunlight, humidity, leaf wetness and soil moisture and temperature.
The wireless soil moisture sensor is one main component of the micro climate weather station. The two probe soil moisture sensor uses the basic principle of a series fed Hartley oscillator frequency shift due to the varying dielectric constant of the soil according to the soil Volumetric Water Content (VWC).
When the soil VWC increases, the dielectric constant also increases as the oscillator frequency decreases. This basic principle is used measure the soil moisture content. Both the soil moisture sensor and micro climate weather station have been developed and tested with the ZigBee mesh network topology. The soil moisture sensor was tested and calibrated, using two different soil types.
This research has successfully achieved its objectives and identifies areas for future development. The third version of the micro climate weather station is under development with the focus on modular design, and a new sensor management system to improve energy conservation.
Source: AUT University
Author: Perera, T. A. S. Achala