Design of Monitor-And-control System for Supermarket Fresh Area Based on ZigBee---IEEE2011

7/31/2019 Design of Monitor-And-control System for Supermarket Fresh Area Based on ZigBee---IEEE2011

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Design of Monitor-and-control System for

Supermarket Fresh Area Based on ZigBee

YangChenwei, Liu Dao, Yao Dunping

Department of Measurement &Automation

Electrical Engineering College of

University of South China

Hengyang, Peoples Republic of China

[email protected]

AbstractAccording to the status that most of supermarkets

cant effectively monitor the temperature and humidity around

food of fresh area in our country Currently, the thesis designs ahierarchical topology central monitoring system based on ZigBee

wireless sensor network(WSN).In the system, the temperature

and humidity of surveyed area can be automatically monitored

and controlled. The monitoring nodes, with the CC2430 chip and

THS11, can collect and upload temperature and humidity data to

the Management Centre, which displays and processes the

data ,through the central node and the RS-232 interface. If the

collected data exceeds the threshold, it automatically starts the

alarm system and the regulating system; while the data is lower

than the standard value, regulating system could be

automatically shut down. Nodes work in the regular query power

saving mode. Power is obtained from button cells conversion

through MAX687.The results reveal that this WSN system has

the potential for field applications due to its low cost, low power

and flexible networking construction.

Keywords: ZigBee, Supermarket fresh area, Monitoring,

Wireless Sensor Network

I. INTRODUCTION

Currently, in the most of our supermarkets, fresh food

(meat, seafood, vegetables, fruit, etc) are put on the sale desk

by spreading through air conditioning at the end of the

counter or capping with ice cluster on the counter. These

methods are likely to cause fresh food heated at top side while

cold 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 air

conditioning or replace ice cluster or spray mist from time to

time. Because of the lack of effective monitoring system,

adding air conditioning or spraying mist is manipulated by the

staff with experience. As fresh food is distributed wildly,

ambient temperature and humidity parameters of fresh food is

tested by hand-hold instrumentation regularly, which has

Yao Shengxing, Li Zuling

Department of Electrical &Information

Engineering of Hunan Institute of Technology

Hengyang, Peoples Republic of China

[email protected]

[email protected]

low efficiency, and is more difficult to achieve a real-time

automatic detection and intelligent control. This increases the

difficulty of the staffs work, and to some extent, increasesthe difficulties of preservation for fresh food.

ZigBee technology is a two-way wireless network

technology of a short distance, low complexity, low power

and low-cost[1]

.It is developed based on IEEE 802.15.4

wireless standards[2]

.The nodes could be expanded up to

65536[3]

.It also has the advantages of low power consumption.

Working in energy saving mode, the two batteries supply

energy up to 1 year and a half or so.Based on these, monitoring project for Supermarket fresh

area is proposed and designed using ZigBee wireless sensor

network. The system is composed of node modules which are

based on high performance single chip CC2430 that integrates

ZigBee wireless network technology, and the modernmanagement center. By the implementation of platform of

software and hardware, the Management Center monitor

temperature and humidity of nodes located in different

parts of the fresh food area. In addition, the system has an

automatic alarm and regulation system. If the detected data

information exceeds the set threshold (for a variety of

preservation condition, the threshold may be set separately to

different fresh food. In the system, the threshold of

temperature of fresh meat is set as 4[4]

),the host displays a

warning information on the screen, immediately sends a

warning instruction to the corresponding node to drive the

warning module to alarm ,so as to alert staff. And also, itstarts the regulation module and opens the solenoid valve to

automatically adjust temperature and humidity around the

food through air conditioning or water mist. While the

temperature or humidity reaches the preset standard value(in

the system, the temperature standard value of the meat is set

to 0 [4]

),the management center sends stop regulating

instruction to the corresponding node to close regulation

module, thus achieving the purpose of automatic detection

and intelligent control.

This work is supported by Research Study and Innovative

Experiment Project of College Students in Hunan Province978-1-4244-8039-5/11/$26.00 2011 IEEE


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II .HARDWARE CONFIGURATION

According to distribution of the fresh food in supermarket

and characteristics of ZigBee technology, the system uses the

tree topology structure, Figure 1 is the structure diagram of

the monitoring system. The system mainly consists of

monitoring nodes, router nodes, the control center node and

the Management Center (PC). All nodes are based on the

CC2430 that is a standards-compliant SOC ZigBee chip based

on IEEE802.15.4Monitoring nodes are the leaf nodes of the

network, mainly responsible to collection data, sound and

light alarm and the temperature and humidity adjustment;

Router node is responsible to network management and data

forwarding, which can guarantee connectivity and robust for a

larger network; Central node is the Coordinator of ZigBee

Network, equivalent to the trunk node in the network,

responsible to management node, processing data and external

interfaces. PC host is the system's central controller, and

connected to the central node through the RS-232interface,

responsible to analysis, processing and conditioning control

data.

Fig.1 Structure diagram of supermarket fresh area monitor system

Supermarket fresh food areas generally are divided into

several small sale units, which are close to each other and the

number is big, which requires more sensor nodes. So

miniaturization and low-power are required for nodes to

facilitate the arrangement and save consumption. In addition,

for the sensor nodes are placed in a humid environment, in

order to work properly, a higher reliability of the hardware is

required.

In the system, the management center has a graphicwarning function. In addition, to increase the field alarm and

automatic control, monitoring nodes are equipped with alarm

module and regulation module.

A. Monitoring Node Design

Monitoring nodes are composed of the wireless transceiver

module (including the main chip CC2430, the clock unit and

the RF antenna unit), the sensor module, alarm module,

regulation module and power supply module. The schematic

is shown in Figure 2.CC2430 manufactured by TI, is the core

of the hardware module, which is a enhanced 8051MCU

integrated with RF transceiver[5]

, working in 2.4GHz band,

low-voltage power supply (2.0 ~ 3.6v), low power

consumption (receiving data is 27mA, sending data is 25mA),

and the maximum transfer rate of 250KB/s.CC2430 clock unit

has two working modes, 32MHz to provide normal power

mode frequency, 32.768MHz for low-power operating

frequency. Antenna module consists of antenna feeder circuit

and impedance matching circuit, the maximum transmission

distance is up to 100m.

K?

Relay-SPST

U?

Optoisolator1Q32N5551

D2

LED1

Fig.2 Schematic of monitoring node

Sensor module is used to get the temperature and humidity,

signal conversion and processing. In the system, SHT11

sensor is produced by the Sensirion of Swiss, with I2C bus

interface and full digital calibration of the relative temperature

and 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 the

relative humidity and temperature; and can be completely

submerged in water.

Power module consists of two 3V button batteries,

MAX687 chip, transistor FZT749 and other components. Two

3V coin cell batteries are collected to give 6V reference

voltage which is transformed to gain 3.3V operating voltage

by MAX687.FZT749 PNP transistor is used to expand theflow of current, with the maximum output current up to

1A.Therefore,the node module could meet the demand of

electricity supply. To meet the saving energy demand, if the

output voltage is less than 2.96V, MAX687 can automatically

cut off the output voltage.

The P1_0 pin of the CC2430 is externally collected a

buzzer to form alarm module, when the sensor node detects a

alarm instruction, fed back from PC, P1_0 could generate a

switching signal to trigger the alarm buzzer.

Regulating module consists of the optocoupler TLP521,


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driver transistor 2N5551,Relay DZ-122 and solenoid valve.

When P0_1 receives low trigger signal, the optocoupler starts

to work, NPN transistor is in a conduction state, a current

flows through the relay, then the solenoid valves starts to

work. Air conditioning or water flows through the open valve,

which adjusts the temperature or humidity. In the system, the

solenoid valve power is supplied by AC 220V.Relay and

optocoupler are 12V and 5V, which are gained by 220V

transformer, rectifier, filter, regulator.

B. Central Node and Routing Node Design

The wireless communication module of the two nodes is

same as the monitoring node, consisting of the wireless

transceiver module and the external circuit, as shown in figure

3. The difference from the monitoring node is that it s main

chip CC2430 connects with a serial communication interface

RS-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-232

level. The hardware module of router nodes are same as thesensor node.

Fig.3 Structure diagram of center node

III. SOFTWARE DESIGN

The modular design of software is used. The main

module is divided into upper and lower machine module.

Upper machine module is the management center module, the

lower machine module is ZigBee node module which includes

the sensor module, the central node module, and routing node

module. In normal conditions of temperature and humidity,

the whole system works in timing query mode. Only when

the monitoring nodes receive a query command, they will

upload the collected data, and the other most of the time theywill be in energy saving state. This article will discuss the

software design for the host computer module, monitoring

node module and central node module.

A. Software Design of PC Module

PC is the system management center, and the work flow

chart is shown in Figure 4. After the system is powered, the

host sends wake-up instructions to each node via RS-232 bus,

to wake the nodes from the close state. If success, each nodes

will send a response message to the management center

through the center node. After confirming that the nodes have

been waked up, Management Centre will send a query

instruction to each node every 1 minute, which checks

whether the node works normally. And at the same time, PC

sends 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, also

compares with the threshold. If a monitoring node data are

greater than the threshold, the corresponding display bar of

node appears warning message. Also PC will send a warning

instruction to the node. Then it will receive real-time data

from the node and ceaselessly compare with the set standard

value ,if the data is less than the standard value, PC will sent a

stop regulating instruction to the corresponding node to

automatically turn off regulator module.

Fig.4 Flow Chart of the Management Center

B. Software Design of Monitoring Node Module

Monitoring node is the terminal node of the network, and

its work flow chart shown in Figure 5.After the node is waked

up, it will automatically initialize hardware and be

self-organized into ZigBee networks, and then read the

instructions from the central node. If it reads the query

instruction, it will collect the data and send it and its address

to the host through the central node; If it receives the alarm

instruction, it will immediately start the alarm module to

remind staff, start the regulation module, and start air or water

valves to automatically adjust the temperature and humidity


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around the food through the relay to open the solenoid valve.

After successfully starting regulating module, the alarm

module will be shut down. It will send the data information to

the control center every 10 seconds. If it receives the stop

regulating instruction, it will immediately close the regulator

module. Nodes are in energy-saving sleep state in other time.

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Design of Monitor-And-control System for Supermarket Fresh Area Based on ZigBee---IEEE2011