Research On Voltage Compensation Method Of WSN Soil Moisture Acquisition Nodes

Detecting the soil water content information of farmland accurately and timely to improve the efficiency of irrigation is very significant to agriculture production and economic development. Establishing reasonable water-saving irrigation scheme by applying wireless sensor network (WSN) technology to test soil water content have been got attention by more and more researchers.According to the characteristic of agriculture production. CC2430 and EC-5 soil moisture sensor with low-voltage and low-power are used, and WSN nodes which are suitable for collecting soil moisture information are designed in this paper. Voltage compensation method was researched from hardware and software after analyzing the source of detection error, especially the influence of EC-5 sensor's output caused by node voltage variety. If hardware method of voltage stabilizer was used, the node cost increases limitedly, but the additional energy consumption introduced by voltage stabilizing circuit will greatly increase the sensor node's energy consumption, reduce the life of node battery, this doesn't meet the design requirements of WSN. The neural network has a strong ability to approximate any continuous nonlinear function, and it can perform the inverse modeling of nonlinear sensor system. Considering the limited resources and weak computing ability of WSN nodes, an effective compensation method is presented according to the basic theory of neural network, it establishes the voltage compensation model of WSN node after the data of soil moisture and node voltage is pretreated as the training sample of neural network. This method does not need more communication costs and energy consumption of sensor node.Experiment was carried out through the voltage compensation platform which is built ordering star topology. The theoretical analysis and experimental results show that this method can effectively eliminate the influence caused by node voltage variation. After compensation, the detection error of soil moisture reduces to less than 1Vol.% when the node voltage descends from 3.2V to 2.1V.