Zigbee is a wireless standard bad on IEEE802.15.4.it is low cost,low power,highly reliable,highly cure . Fig.2 depicts two key performance characteristics – wireless radio range and data transmission rate of the wireless spectrum. Comparing to other wireless networking protocols ,ZigBee shows excellent transmission ability in lower transmission rate and highly capacity of network. .ZigBee meet the requirements for reliability,curity,low costs and low power-consumption in the GEMS.
ZigBee framework is made up of a t of blocks called layers. As shown in Fig.3. The IEEE 802.15.4 standard defines the two lower layers: the physical (PHY) layer and the medium access control (MAC) layer. The ZigBee Alliance builds on this foundation by providing the network and curity layer and the framework for the application layer .
Fig.5 is a ZigBee network model, it supports both single-hop star topology and mesh topology. Coordinator manages the network, it can provide binding and address-table rvices, and save messages until they can be delivered. bore的用法
英文个人简历In this project ,we deploy five kinds of nsors in the greenhou bament .through thes
kuhlee deployed nsors, temperature,soil temperature,dew point,humidity and light intensity can be detected real time.figure is the overview of GEMS.when nsor nodes collect parameters real time,coordinator completes the task of data analysis and storage,menawhlie ,it is connected with GPRS/CDMA.In the monitoring center,by running greenhou management software,coordinator can periodically receive data from the wireless nsor nodes and display them on monitors.
Figure shows the universal structure of the WSN nodes.power module provides the necessary energy for the nsor nodes.Data collection module is ud to receive and convert signals of nsors.Data processing and control modules’functions are node device control,task scheduling,and unication module is ud to tranmit data between nodes.
In the data transfer unit,the ZigBee module is embeded to match the MAC layer and the NET layer.we choo CC2430 as the ZigBee protocol chips,which ingegrated the CPU,RF transceiver,net protocol and the RAM together.The SHT11 can test the soil temp
八年级上册英语课件erature and humidity.the DS18B20 is a digital temperature nsor,which has 3 pins and data pin .the TCS320 is a digital light nsor.the nsor nodes are powered by onboard batteries
The figure show the software flow started,the first action is the initialization of the hardware,satck and application variables.then a network will be formatted.and then physical address ,net ID,channel number will be showen on the LCD.then program will step into application layer and monitor ZigBee signal.if there is end device or router want to join in this net, LCD will show this information,the coordinator will allocate a net address.and the data transmitted by this node will be received by coordinator and shown in the LCD
alleyFigure show the software flow of a nsor node.as each nsor node is switched on,it scans all channels and,after eing any beacons,checks that the coordinator is the one it is looking for.it then performs a synchronization association is complete,the nsor node enters a regular loop of reading its nsors and putting out a fr
ame containing the nsor data.if nding successfully,end device will step into idle state.by contrast,it will colletc data noce again and nt to coordinator.
Currently,we have carried out experimental deployment of GEMS in the intelligent greenhou.as shown in figure,at different times.there is distinct difference for light intensity and soil temperature monitored respectively for the nodes deployed at different locations.
GEMS has the advantages of low cost,low power and easy maintenance. It can collect important environment factors which influence plants’growth.it also realizes the wide area transmission of the information.there is still room for improving the system functionality and increasing the practicality of the system.the future work includes the following firsr,According to the actual application requirement, we will monitor other environment factors which influence crop's growth, thus realizing a more systematic and comprehensive monitoring of the greenhou environment. 2. Carry out reliability analysis and accelerated fatigue testing on GEMS. By establishing reliability model, we can realize the system fault pre-warning and predict the residual life. ecr
