Design and test of real-time monitoring of droplet evaporation system based on standing wave and ZigBee

Abstract: The evaporation time of pesticide droplets on the leaf surface of plants is closely related to the absorption efficiency of pesticide droplets for plant leaves, which directly affects the efficiency of pesticide application. Pesticides can be divided into suction and touch type. For the suction of pesticides, after the droplets subsided to the foliage, as the extension of droplet evaporation time, the capillary pores of the leaves will absorb more pesticide particles, and pesticide pest control effect is better. For touch-type pesticide, the shorter the evaporation time of the droplets, the lower the probability of pesticide droplets falling from the blade surface by natural winds, and the effect of pesticides on pests and diseases is better. Therefore, the evaporation time of pesticide droplets on the surface of leaves, has a great impact on the pest control and pesticide utilization. In order to find out the influence factors of the evaporation of the droplet, the real-time monitoring system of the droplet evaporation based on the standing wave and ZigBee wireless transmission was designed. The system uses STM32 as the core to build the ZigBee network, and terminal nodes are connected with droplet collecting sensor. The data are transmitted to the network coordinator, then the coordinator transmits the data to the remote evaporation system designed by LabView2014 through the RS232 serial port, and the system realizes the real-time monitoring of the droplet evaporation condition through the waveform. From the waveform, we know that from the droplet deposition to the completion of evaporation, the system can accurately receive the data of evaporation loss which are returned by the ZigBee and show the fluctuation curve of the droplet area spread, and compared with the image processing method, its error is small, and it is easy to operate and more practical. The results show that: 1) The evaporation time of droplet is positively correlated with the particle size, which increases with the increase of droplet size. And when the particle size exceeds 242.3 μm, the trend is more obvious. 2) The droplet evaporation time is negatively correlated with the area spreading rate, and decreases with the increase of the droplet area spreading rate. When the volume fraction of organic silicon increases from 0.025% to 0.050%, the droplet area spread rate increases, but when it increases from 0.050% to 0.100%, the droplet area spread rate is relatively reduced. 3) The evaporation system can not only achieve remote detection, which avoids contact with liquid, but also perform real-time analysis of droplets evaporation time on the leaf surface and the area spread rate, and reasonably choose silicone volume fraction and droplet diameter, which helps to control the liquid absorption efficiency of leaf surface. The evaporation system can analyze the droplet evaporation in the blade surface evaporation time and the area spreading rate in real time. It provides a reference for the study of the evaporation time and spreading law of the droplets on the surface.