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Design of monitor and-control system for supermarket fresh area based on zigbee

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  • 1. Design of Monitor-and-control System forSupermarket Fresh Area Based on ZigBeeYang Chenwei, Liu Dao, Yao DunpingDepartment of Measurement &AutomationElectrical Engineering College ofUniversity of South ChinaHengyang, People’s Republic of ChinaYangchenwei1985@163.comAbstract According to the status that most of supermarketscan’t effectively monitor the temperature and humidity aroundfood of fresh area in our country Currently, the thesis designs ahierarchical topology central monitoring system based on ZigBeewireless sensor network(WSN).In the system, the temperatureand humidity of surveyed area can be automatically monitoredand controlled. The monitoring nodes, with the CC2430 chip andTHS11, can collect and upload temperature and humidity data tothe Management Centre, which displays and processes thedata ,through the central node and the RS-232 interface. If thecollected data exceeds the threshold, it automatically starts thealarm system and the regulating system; while the data is lowerthan the standard value, regulating system could beautomatically shut down. Nodes work in the regular query powersaving mode. Power is obtained from button cells conversionthrough MAX687.The results reveal that this WSN system hasthe potential for field applications due to its low cost, low powerand flexible networking construction.Keywords: ZigBee, Supermarket fresh area, Monitoring,Wireless Sensor NetworkI. INTRODUCTIONCurrently, in the most of our supermarkets, fresh food(meat, seafood, vegetables, fruit, etc) are put on the sale deskby spreading through air conditioning at the end of thecounter or capping with ice cluster on the counter. Thesemethods are likely to cause fresh food heated at top side whilecold on the bottom side, temperature and humidity uneven,which easily make the food go bad and cause economic losses.Avoiding this, the staff of the supermarket have to add airconditioning or replace ice cluster or spray mist from time totime. Because of the lack of effective monitoring system,adding air conditioning or spraying mist is manipulated by thestaff with experience. As fresh food is distributed wildly,ambient temperature and humidity parameters of fresh food istested by hand-hold instrumentation regularly, which hasYao Shengxing, Li ZulingDepartment of Electrical &InformationEngineering of Hunan Institute of TechnologyHengyang, People’s Republic of Chinayaoshengxing@yahoo.com.cnlizulin321@yahoo.com.cnlow efficiency, and is more difficult to achieve a real-timeautomatic detection and intelligent control. This increases thedifficulty of the staff”s work, and to some extent, increasesthe difficulties of preservation for fresh food.ZigBee technology is a two-way wireless networktechnology of a short distance, low complexity, low powerand low-cost[1].It is developed based on IEEE 802.15.4wireless standards[2].The nodes could be expanded up to65536 [3].It also has the advantages of low power consumption.Working in energy saving mode, the two batteries supplyenergy up to 1 year and a half or so.Based on these, monitoring project for Supermarket fresharea is proposed and designed using ZigBee wireless sensornetwork. The system is composed of node modules which arebased on high performance single chip CC2430 that integratesZigBee wireless network technology, and the modernmanagement center. By the implementation of platform ofsoftware and hardware, the Management Center monitortemperature and humidity of nodes located in differentparts of the fresh food area. In addition, the system has anautomatic alarm and regulation system. If the detected datainformation exceeds the set threshold (for a variety ofpreservation condition, the threshold may be set separately todifferent fresh food. In the system, the threshold oftemperature of fresh meat is set as 4 [4]),the host displays awarning information on the screen, immediately sends awarning instruction to the corresponding node to drive thewarning module to alarm ,so as to alert staff. And also, itstarts the regulation module and opens the solenoid valve toautomatically adjust temperature and humidity around thefood through air conditioning or water mist. While thetemperature or humidity reaches the preset standard value(inthe system, the temperature standard value of the meat is setto 0 [4]),the management center sends stop regulatinginstruction to the corresponding node to close regulationmodule, thus achieving the purpose of automatic detectionand intelligent control.This work is supported by Research Study and InnovativeExperiment Project of College Students in Hunan Province978-1-4244-8039-5/11/$26.00 ©2011 IEEE
  • 2. II .HARDWARE CONFIGURATIONAccording to distribution of the fresh food in supermarketand characteristics of ZigBee technology, the system uses thetree topology structure, Figure 1 is the structure diagram ofthe monitoring system. The system mainly consists ofmonitoring nodes, router nodes, the control center node andthe Management Center (PC). All nodes are based on theCC2430 that is a standards-compliant SOC ZigBee chip basedon IEEE802.15.4 Monitoring nodes are the leaf nodes of thenetwork, mainly responsible to collection data, sound andlight alarm and the temperature and humidity adjustment;Router node is responsible to network management and dataforwarding, which can guarantee connectivity and robust for alarger network; Central node is the Coordinator of ZigBeeNetwork, equivalent to the trunk node in the network,responsible to management node, processing data and externalinterfaces. PC host is the systems central controller, andconnected to the central node through the RS-232interface,responsible to analysis, processing and conditioning controldata.Fig.1 Structure diagram of supermarket fresh area monitor systemSupermarket fresh food areas generally are divided intoseveral small sale units, which are close to each other and thenumber is big, which requires more sensor nodes. Sominiaturization and low-power are required for nodes tofacilitate the arrangement and save consumption. In addition,for the sensor nodes are placed in a humid environment, inorder to work properly, a higher reliability of the hardware isrequired.In the system, the management center has a graphicwarning function. In addition, to increase the field alarm andautomatic control, monitoring nodes are equipped with alarmmodule and regulation module.A. Monitoring Node DesignMonitoring nodes are composed of the wireless transceivermodule (including the main chip CC2430, the clock unit andthe RF antenna unit), the sensor module, alarm module,regulation module and power supply module. The schematicis shown in Figure 2.CC2430 manufactured by TI, is the coreof the hardware module, which is a enhanced 8051MCUintegrated with RF transceiver [5], working in 2.4GHz band,low-voltage power supply (2.0 ~ 3.6v), low powerconsumption (receiving data is 27mA, sending data is 25mA),and the maximum transfer rate of 250KB/s.CC2430 clock unithas two working modes, 32MHz to provide normal powermode frequency, 32.768MHz for low-power operatingfrequency. Antenna module consists of antenna feeder circuitand impedance matching circuit, the maximum transmissiondistance is up to 100m.K?Relay-SPSTU?Optoisolator1Q32N5551D2LED1Fig.2 Schematic of monitoring nodeSensor module is used to get the temperature and humidity,signal conversion and processing. In the system, SHT11sensor is produced by the Sensirion of Swiss, with I2C businterface and full digital calibration of the relative temperatureand humidity [6].With accurate dew point measurement,ultra-fast response time (less than 4s), ultra-small size(7.5*5*2.5mm),the sensor can simultaneously measure therelative humidity and temperature; and can be completelysubmerged in water.Power module consists of two 3V button batteries,MAX687 chip, transistor FZT749 and other components. Two3V coin cell batteries are collected to give 6V referencevoltage which is transformed to gain 3.3V operating voltageby MAX687.FZT749 PNP transistor is used to expand theflow of current, with the maximum output current up to1A.Therefore,the node module could meet the demand ofelectricity supply. To meet the saving energy demand, if theoutput voltage is less than 2.96V, MAX687 can automaticallycut off the output voltage.The P1_0 pin of the CC2430 is externally collected abuzzer to form alarm module, when the sensor node detects aalarm instruction, fed back from PC, P1_0 could generate aswitching signal to trigger the alarm buzzer.Regulating module consists of the optocoupler TLP521,
  • 3. driver transistor 2N5551,Relay DZ-122 and solenoid valve.When P0_1 receives low trigger signal, the optocoupler startsto work, NPN transistor is in a conduction state, a currentflows through the relay, then the solenoid valves starts towork. Air conditioning or water flows through the open valve,which adjusts the temperature or humidity. In the system, thesolenoid valve power is supplied by AC 220V.Relay andoptocoupler are 12V and 5V, which are gained by 220Vtransformer, rectifier, filter, regulator.B. Central Node and Routing Node DesignThe wireless communication module of the two nodes issame as the monitoring node, consisting of the wirelesstransceiver module and the external circuit, as shown in figure3. The difference from the monitoring node is that it’ s mainchip CC2430 connects with a serial communication interfaceRS-232 through which Management Center communicates.MAX3232 chip is selected, the working voltage is 3.3V,which can achieve TTL level converter with two-way RS-232level. The hardware module of router nodes are same as thesensor node.Fig.3 Structure diagram of center nodeIII. SOFTWARE DESIGNThe modular design of software is used. The mainmodule is divided into upper and lower machine module.Upper machine module is the management center module, thelower machine module is ZigBee node module which includesthe sensor module, the central node module, and routing nodemodule. In normal conditions of temperature and humidity,the whole system works in timing query mode. Only whenthe monitoring nodes receive a query command, they willupload the collected data, and the other most of the time theywill be in energy saving state. This article will discuss thesoftware design for the host computer module, monitoringnode module and central node module.A. Software Design of PC ModulePC is the system management center, and the work flowchart is shown in Figure 4. After the system is powered, thehost sends wake-up instructions to each node via RS-232 bus,to wake the nodes from the close state. If success, each nodeswill send a response message to the management centerthrough the center node. After confirming that the nodes havebeen waked up, Management Centre will send a queryinstruction to each node every 1 minute, which checkswhether the node works normally. And at the same time, PCsends a read data instruction to the node to read the node data.After receiving the data, management center automaticallyrecords and displays data from monitoring nodes, alsocompares with the threshold. If a monitoring node data aregreater than the threshold, the corresponding display bar ofnode appears warning message. Also PC will send a warninginstruction to the node. Then it will receive real-time datafrom the node and ceaselessly compare with the set standardvalue ,if the data is less than the standard value, PC will sent astop regulating instruction to the corresponding node toautomatically turn off regulator module.Fig.4 Flow Chart of the Management CenterB. Software Design of Monitoring Node ModuleMonitoring node is the terminal node of the network, andits work flow chart shown in Figure 5.After the node is wakedup, it will automatically initialize hardware and beself-organized into ZigBee networks, and then read theinstructions from the central node. If it reads the queryinstruction, it will collect the data and send it and its addressto the host through the central node; If it receives the alarminstruction, it will immediately start the alarm module toremind staff, start the regulation module, and start air or watervalves to automatically adjust the temperature and humidity
  • 4. around the food through the relay to open the solenoid valve.After successfully starting regulating module, the alarmmodule will be shut down. It will send the data information tothe control center every 10 seconds. If it receives the stopregulating instruction, it will immediately close the regulatormodule. Nodes are in energy-saving sleep state in other time.Fig.5 Flow chart of monitoring nodesC. Software Design of Central Node Module andRouting Node ModuleFig.6 Flow chart of center nodCentral node is a connection point between the ZigBeenetwork and the management center, playing Gateway role.The workflow is shown in Figure6.After the node wake-upinitialization, the node is waiting to receive information,which may be instructions from the management center oralso may be data in other nodes. If a instruction, the centralnode will parse the command information, and theninstruction is sent to the designated node, when receiving thedata information from other nodes, central node will sendthem to management center.Routing node module in this system is mainly used toenhance the network monitoring’s coverage and stability. Themain program essentially is similar with the central node, so itis not repeated here.IV. CONCLUSIONSSimulation tests of the system were implemented throughthe arrangement of 12 monitoring nodes, two routing nodes, acentral node and a central host in a local supermarket’s freshmeat sale counter. By Field testing, super-fresh meat salecounter’s temperature is 3.5 or so, humidity 78% or so, thecommunication distance of the monitoring node and routingnode is 23m or so. Within the 15m range, even when there isinterference of people walking around the supermarket,communication system, alarm system and regulation systemstill work correctly. As more points can be monitored, withmore flexibility node layout, lower cost and with a real-timedisplay and automatic alarm, adjustment function, the systemcan achieve reliable and efficient wireless intelligentmonitoring for supermarket fresh food, which creates acertain condition for modern management of the supermarket.V. ACKNOWLEDGMENTSWe wish to thank professors Tan Yaogeng and Li Lanjun ofthe department of Measurement &Automation at Universityof South China for their encouragement and support on ourproject.REFERENCES[1]ZigBeeAlliance.ZigBeeSpecificationVersion1.0[M]. ZigBee StandardsOrganization, 2004.[2] Howitt I.Gutierrez J A IEEE 802 1 5 4 low rate wireless personal areanetworks coexistence issues[J] WirelessCommunications and Networking 2003 pp 1481 1486[3] Bastinb Tony Roy Savarimuthu Morgan Bruce Maryam PurvisA ASoftware Framework for Application Development using ZigBee ProtocolTheInformation Science Discussion Paper Series Number 2009/03 ISSN1177-455X[4]JiangYujian1 Zhou Xiaoping2 Study on Shelf Life of MAP Packaged Porkunder Refrigerated Condition Food and Fermentation Industries2003( Chinese )[5]Bao Changchun Designed of Monitoring system for grain depot based onzigbee technology Transactions of the CSAE vol .25 NO 9Sep .2009(Chinese)[6]Datas heetforSHT11(v2.0),2003.http://www.sensirion.com

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