Distribution of combustible gas alarm based on embedded Ethernet technology

Journal of Harbin Institute of Technology( New Series, Vol 15, No. 2, 2008Distribution of combustible gas alarm based onembedded Ethernet technologyDING Xi-bo,, ZHANG Jun-jie, WANG Yang丁喜波,张俊杰,王ce Optics Research Center, School of Astronautic, Harbin Institute of Technology, Harbin 150001, China;2. College of Measure-control Technology Communication Engineering, Harbin University Science and Technology, Harbin 150080,China;3. Heilongjiang Provincial Institute of Measurement and Verification, Harbin 150036, China)Abstract: One kind of combustible gas alarms based on industrial Ethemet was designed to prevent the gasleakage in industrial production sites. The alarm adopted the high performance microprocessor LPC2214 as themain chip. The embedded operating system uC/OS-ll and TCP/IP protocol stack ulP running on LPC2214 con-stitute a development platform of application of the combustible gas alarm. The test shows that it can automati-cally and continuously detect combustible gas in industrial production sites in several positions; it can give ousound-light alarm and take proteres immediately against the gas leakage and it can send the deteeteddata to PC through the Ethernet interface to realize the remote detection. The designed project provides a reference to design industrial devices based on industrial Ethernet.Key words: industrial Ethernet; combustible gas alarm; embedded systemCLC number: 043Document code: AArticle II:10059113(2008)02022004Nowadays, most of combustible gas alarms for large vided by embedded control module, consisting byscale applications are still stand-alone analogue me- croprocessor, consisting by microprocessor, memory sys-electric circuit etcthickness in environment and output 4-20 mA analog2)Intermediate layer between hardware platformsignal. Though being able to connect to DCS, PLC and and software platform is also called BSP( Board Sup-data acquiring system directly, those kinds of meters do port Package), which is a software module compiled fornot conform to the tendency to digital and networking hardware in system, for example, program porting codesmeters. Along with the development of industry Ether- about microprocessor or hardware drivers. The overallnet technology and applications of Ethernet in Internet, design of BSP includes two parts, initialization of em-it would be the new tendency that meters plug into in- bedded system and Ethernet controller driverdustrial field bus[2-3)nc3)Software platform is made up of RTOS MultiTaking full advantages of Ethernet technology), thread Program Model ) network system and generalcombustible gas alarm could send the detecting data to set-up module.the PC through the Ethernet interface and realize re-4) Function layer is the application program basedmote detection of combustible gas in industrial produc- on RTOS to complete alarm system function needed bytion sites. It also has function of display of density ofuserscombustible gas and alarm time, sound-light alarm, con-trol of safekeeping equipment such as ventilating 2 Hardware Designfan). It has characteristics of high transmissibility, reli-ability, maintainability and remote transmission, andIn alarming system, combustible gas alarm is thevalues of Practical applicationintelligent node as shown in Fig. I, whose function is toreceive the signals of gas concentration from detectors1 General Designand to send the alarm information through Ethernet. Italso realizes the task of displayingofThe general design of combustible gas alarms di- concentration. iudging if the percentages are out of中国煤化工 g alarm time,and1) Hardware platform for system operation isCNMHGReceived 2006-06-07Sponsored by the National High Technology Research and Development Program of China(863 Program)( Grant No. 2006AA0-40601)220Journal of Harbin Institute of Technology( New Series), Vol 15, No 2, 2008quisition and amplification circuit. AD623, one kind ofEthemet switchsingle-supply instrument amplifier whose output swingcould reach the power voltage, is used to amplify thesmall-amplitude signal from sensor precisely, suppEthemetcommon-mode and improve signal quality, whicht convenient to a/d conversionombustibcombustibleis alarm息2. 3 Ethernet Interface and Control Circuitgiss alarmEthernet interface and control circuit is composedDetectorDelectorof Ethernet controller chip RTl8019AS expandedrface in LPC2214 and itsFig 1 Alarming system structureother peripheral circuit. RTL8019AS, a high-densityTo meet the demands mentioned above, the hard. 10Mbps Ethernet controller compatible to Ethernet IIand IEEE 802. 3, has advantages in hard software por-ware is composed of power circuit, microprocessor, sig tability, low price, and so onal acquisition and amplification circuit, Ethernet inter-face and control circuit alarm controller and the manNowadays, as the characteristics are hard real-timeinterface, etc. The hardware structure of com- Ethernet technology based on TCP/IP protocol is thalarm is shown in Fig. 2. Meanwhile, ex- best choice for field devices such as alarm to get accesconsidered in the design due to intelligent field instru- to industry control network. In the design, dependifpproof and other safety precautions should bements of industry applicationon this technology, we can achieve communication be-tween combustible gas alarm and Intemet by Ethernetcontroller rtl8019ASPower Module2. 4 Human- Machine Interface and Power CircuitOn the purpose of keeping watch on and setting upAid Kthe alarm in industrial field, this design also provideshuman-machine interfaces such as keys, display and V/O output, whosebeDetectARM LO-ClockLPC2214Buzzer alarmment to eliminate security threat like EDM and meetResetExtemalUART'YZNE-IoTthe demand of anti-explosion. Meanwhile, power circuitneeds to supply 2.5 V precision reference voltage forRS232A/D conversion of LPC2214 except other partsFig 2 Hardware structure of alarm2. 1 Microprocessor Module3 Software DesignThis system selects a high-performance micropro-cessor LPC2214 as the master chip, which is anIn order to reduce the development cycle time andARM7TDMI-S supporting real-time simulation andenhance the stability, software design uses the proposalof real-time multi-tasking operating system on accounttrack technologies and doing In-System Programming of complicated functions of combustible gas alarm. Ac-(ISP )and In-Application Programming( IAP ). Itscording to the structure drawing constituted by hard-32-bit RISC Microcontroller could reduce the energy ware platform and software( as shown in Fig 3), soft-supply of controlling system. 8-channels 10 bit ADCand 2. 44 us transition time make it more convenient toware design is modulized and its preparation work inconvert the signal from detectors rapidly. Extermalcludes completing HC/OS-I's operation on micropro-cessor LPC2214, transplanting TCP/IP Protocol-ulP in-memory interface is fit for the extension of Ethernet in- to uC/OS-I, designing driver program of RTL8019ASterface cbased on ulP, and so on. Corresponding program mod-As the control unit core of embedded Ethernet ules are compiled in accordance with the tasks that a-technology, microprocessor module is the most imparm should achieve, and then the jobs of tasktant module and directly related to overall performance ment, execution time management, synchronous commuof alarm system. Microprocessor is mainly responsibleto run TCP/IP protocol stack and complete the task of nication among tasks, memory management are finishedEthernet communication except the task of measure-by uC/OS-l operating system based on the prioritiesment and controlcomb中国煤化工 functions of2. 2 Signal Acquisition and Amplification Circuit 3.1Catalyst combustion gas sensors and precision inCNMHGpletely preemptivestrumentation amplifier AD623 constitute the signal ac- RTOS with open source code and able to be curtailedJournal of Harbin Institute of Technology( New Series), Vol 15, No 2, 2008which has been proved to be safe and stable by many 3. 4 Design of Alarmprofessions practices. What is more, it just has onlyonsidering the principles of Dependency on In-5500 line source code, and its object code can be cur- put/Output Device, Time-critical functions-Hard Dead-tailed to be less than 2 K byte so that the RTOS just line and Cyclic executing function ,we divide alarmoccupies 4 K byte of RAMapplication program into 7 functional modules keyBin. to make uc/oS- lls real-time kernel operate on scanning, LED display, real-time clock, signal collec-roprocessor LPC2214 normally, the microprocessor tion, alarm controls, setting parameters and network up-must meet certain conditions. Under the technical de-ading. The relationship among 7 modules is shown intails of processor and C compiler, it is necessary to Fig 4, in which NET MBox, ALARM. MBox, LEDcomplete some porting tasks of uC/OS-ll. For exam- MBox and SET MBox are the mailboxes designed toole, we declare 3# define macros(OS. CPU. H)pass or share messagewrite 6 simple functions in C(OS_ CPU. C C)Real TimeApplication Program of Combustible Gas AlarmNetworkA DataALARM MboxuIP Protocol stackAlarmuCOSⅡRTL8019AS DriverLPC2214RTL8019AS ChipParametersFig 3 Software hierarchy3.2 ulP in uc/oS-IIFig 4 Relationship among software modulesBecause there is no TcP/ IP Stack inμC/Os-ⅡTasks implementation of alarm is to compile thewe add a tiny TCP/IP protocol-ulP in the design, which interface functions for each module mentioned abovewas developed by Adam Dunkels and is applied on em- based on the platform of embedded operating systembedded microcontrollers from 8-bit to 32-bit, with main- uC/OS-I. Then uc/OS-II calls the basis function totained interoperability and RFC standards compliance. complete the module's task in accordance with theIt provides the necessary protocolsfor Internet commu- state of combustible gas alarm. There is only onenication, with a very small code footprint and RAM re- to schedule tasks in uc/OS-I that is to executequirementstask given higher priority, so we should design taskIn the design, to embed ulP into RTL8019AS and ority reasonably for improving system performance anduC/OS-I, the work mainly contains functions editing avoiding lockingand constant match, in aspects of the connection be-Taking alarm control module as an example, itstween ulP and system interface or application program- main work are to deal with the data of combustibleming interface and the porting and configuration of gas'density from news-mailbox AD MBox, to alarm inindustrial field and to display density information. As3. 3 Driver Program of RTL8019ASthe important part in the design, alarm task has theThe RTL8019AS is a highly integrated Ethernet ority 10 and program flow is shown in Fig.5Controller, which offers a simple solution to implementa Plug and Play NE2000 compatible adapter and pro- 4 System Testingvides the auto-detect capability between the integrated10BaseT transceiver BNC and AUI interface. With theData collection module is the key part of systemthree level power down control features, the testing and Ethemet interface module is the most com-RTL8019AS is made to be an ideal choice of the net- plex part because of its involvement with the network awork device for a GREEN PC systemOn the basis of information transmission modegreement, so their test will be introduced emphaticallyThe test of the data collection module is to com-RTL8019AS's driver program needs to compile 3 inter- pare analog input signals from slide rheostat with digitface functions named respectively initialization functionnet_init(), data packet sending function net. write()中国煤化工 ult indicates that theand data packet receiving function net. read(), with tioCNMHG difference betweenwhich various functions of the first-floor hardware cancombustible gas measured by data collection modulebe realizedand experimental gas doesnt surpass 5%LEL.Journal of Harbin Institute of Technology( New Series), Vol 15, No. 2, 20085 Conclusion配宽MThis paper solves the problem how to dispose ofthe information based on TCP/IP protocol under thelimited resources of MCU, in order to change the infor-mation into data packages transmitting easily on indus-Are data available?trial Ethernet. to achieve the goal of Ethernet commcation. This alarm has high measurement accuracy.ead the data fromAccording to the calculating data, its systematic error a-ALARM MIOXrising from voltage source, sensor, amplification circuitand A/D conversion is y= 2. 6 x 10 and less thanOn the scope of low-level1%. In the design, combustible gas alarm adapts tonew type field-bus control system and its entire softwarelow-level alarmand hardware system has a greater degree of upgradingOn the scope of high-levelReferences[1]Wang H X, Ren S M, Hao K H. Monitoring, alarmntroller for an inflammable gas. Instrument Technand Sensor. 2002. 4: 41-61Instrument malfimcto[2]Katzel J, Hoske M T. Industrial Ethernet protocols. ControEngineering,2006,53(12):58-63∠、 Within normal scop2F[3] Wilson A. The challenge of embedded internet design. E-lectronic Product Design, 1998, 12(3): 34-37.Normal display[4] Zou J N, Chen Lin R J. Implementation of access control-Wrong handlingler for Ethernet passive optical network. Journal of Shanghai University,2006,10(5):425-430.Fig 5 Flow chart of alarm task[5] Zhang SM. Researching and exploiting embedded systemased on ARM controller LPC2214. Electronic EngineeringThe test of ethernet interface module needs toproduct World. 2005. 12: 73-78.make sure system stability and transfer performance of[6] Hu X L, Wu G. RTL8019AS and its application in embednetwork in the constructed environment of industrialded Ethernet system. Chinese Journal of Scientific Instru-ment,2007,5:84-89Ethernet, through testing the receiving/sending time of [7]wang XM, Zhang s x. The porting of real-time operationdata packet between alarm and server, and detectingsystem uc/OS-I on ARM. Mechatronic, 2007, 1: 20the uniformity of time-interval. Known from the timeinterval of sending the data according to TCP protocol, [8 LiS Y, Tan n l, Wang X D. Real-time multi-tasking oper-as shown in Tab. 1, transmission velocity and stabilityating system and microcontroller software design. Electronicof Ethernet could meet the needs of alarms designEngineering& Product World, 2002, 13: 15-19Send the data according to tCP protocolTime/s0.0398270.0397570.0399010.0402780.039317中国煤化工CNMHG223