Design of energy self-sufficient wireless sensor network node for orchard information acquisition

A type of wireless sensor network (WSN) node suitable for orchard information acquisition was designed to solve the existing problems as wireless communication obstruction and battery replacement difficulties.. The node uses a MSP430F149 as the processing core, a nRF905 RF chip and its peripheral circuits was used as wireless communication module, power management chips CN3058 and HT6292 as well as their peripheral circuits were used as the solar charging module, motor driver chip uln2003 and vertical、horizontal motors were used as the solar tracing module, DHT22 air temperature and humidity sensor and TDR-3 soil moisture sensor and their peripheral circuits were used as the sensing module. The communication protocol, application program and time synchronization algorithm were designed based on the hardware platform. Power consumption , communication distance and charging time of one node were tested and analyzed, the maximum effective communication distance of the designed nodes reached 202 m in unoccupied regions. In the test of charging time, 580 minutes were needed for charging one lithium battery from 3V to 3.6 V, and 283 minutes were needed for charging two tandem lithium batteries from 5.6 V to 8.4 V. With no solar charging and a working cycle of 30 min, the theoretical life cycles of the main circuit and sensor circuit is 497 d and 187 d，respectively. A WSN was established for measuring temperature, humidity and soil water content in a citrus orchard, the experimental results indicated that the network packet loss rate is 1.5%.