基于单片机的室内一氧化碳安全监控系统设计(9) (1).doc

长春理工大学毕业设计题目论证书题目： 基于单片机的室内一氧化碳安全监控系统设计1 本课题研究的目的，意义随着经济的发展，人们对生活质量的提高和生活环境的改善越来越重视，液化气、煤气进入家庭的使用为人们带来了方便，也改善了城市的环境，但同时也给人们带来了潜在的危险，其中一氧化碳是最主要的危险源。由于使用不当或设备不完善、老化等问题引起煤气泄漏、爆炸的事故也在增多，极大的威胁着人们的生命财产安全。虽然人们对煤气泄漏事件有了一定的防范意识，但是，煤气泄漏事件造成的家庭悲剧时有发生，不仅带来了人员伤亡，而且还造成了严重的经济损失。为了确保家庭用气的安全，防止煤气泄漏引起的中毒和爆炸事件的发生，CO气体检测与报警系统也就应运而生了。CO气体检测报警系统能够检测室内CO气体的浓度，当室内CO浓度增加并超限时，系统就会报警，这在减少人员伤亡和经济损失方面起到至关重要的作用。一般的CO报警器功能单一，性能稳定性低，而大型的监控系统又价格不菲，需要专门的技术人员来管理，不适用于中小企业和家庭。所以，及时准确地对有房间室内进行CO浓度监测和报警成为保障群众生命安全和国家财产安全的一项必不可少的工作。为此，我设计开发了一套应用于房屋室内的基于单片机的一氧化碳安全监控系统。 2国内外研究现状 国内研究状况人们最初认识室内环保问题，以人体排出的二氧化碳、体臭以及烟雾作为研究对象，并根据研究，提出了最小通风换气率。70年代，由于世界性范围的节能，建筑物加强了气密性，减少了新风量，同时由于有机合成材料和新设备的广泛使用，使得挥发性有机化合物大量散发，因此IAQ大大降低，出现了病态建筑综合症(SBS)等与此有关的病状。自1986年开始，同济大学的沈晋明教授一直从事IAQ方面的研究，他对上海许多办公楼进行了主观与客观的研究，了解了IAQ的现状，同时提出了IAQ评价的方法及标准，也提出了改善IAQ的策略;重庆建筑大学及其它相关单位的学者也提出IAQ对新风量的确定及新风处理的重要性 国外研究状况1978 年，丹麦哥本哈根召开了关于室内空气品质的国际会议 (InternationalConference on Indoor Air Quality Climate)，并决定以后每三年举行一次。80年代中期，美国EPA的工作重点由室外大气转向室内空气。西方各国，包括欧共体和北大西洋公约组织成员国也开展了室内环保的研究。1991年，ASHRAE与国际建筑研究学会(CIB)联合举办了健康建筑与IAQ 的国际会议(Healthy Building/IAQ 91), 1997年，该会议在华盛顿召开，目的是为了获取信息，使会员对室内环保和SBS在各类非工业建筑中的状况了解。从1992年开始，己有34场以室内环保为主题的国际性会议在美国召开。此外与此相关的国际组织、国际会议、刊物及网站也很多。现行检测CO的手段主要有：利用束管检测系统；采用CO检测器或传感器报警仪来测定；利用抽气唧筒取气样，进行色谱分析或用CO检定管来测定CO的浓度。检测CO浓度的仪器有很多，按原理可分为：电化学、红外线吸收、气敏半导体型等；按安装方式可分为：便携式和固定式。就我国目前使用情况来看，以电化学便携式居多。下面以LTJ-300型便携式CO检测报警仪为例简单说明一下CO检测仪的结构。LTJ-300型便携式CO检测报警仪是应用电化学原理实现大气中CO气体含量测量与超限自动报警的携带式仪器。它具有读取迅速、直观准确及连续监测等特点。该仪器以四位数码来显示所测CO的浓度值，显示范围为0-0.0003%CO,报警范围在0.000020.0015CO任意可调，报警方式为断续声光信号，仪器的反应时间小于30秒，传感器使用寿命一年。该仪器外形为长方体，左上部为报警指示灯，右上部为传感器，正面板左上方为蜂鸣器，中部为四位码显示窗，仪器的右侧中部设有电源开关，下部有一个“关合”板，打开它可见调0和调报警点电位器，仪器的中下部设有调精度电压器，而在下方则设有一节6F22型叠层方形电池。3拟采取的研究路线本文采用单个传感器检测一氧化碳气体浓度，将检测到的浓度结果通过运算放大器放大后送入模/数芯片ADC0809中进行模数转换，传入单片机中，由AT89C51单片机处理数据，并利用单片机控制报警器进行声音报警。其中硬件部分主要研究CO气敏传感器的工作原理；采样信号的温度补偿；A/D转换的实现和起停控制；控制芯片的管脚分配及时钟电路和复位电路的控制等。4进度安排第一周第三周 调研、查阅相关资料、完成文献综述及开题报告第三周第九周 论文方案设计，实验，优化第九周第十四周 系统软、硬件调试，完成论文中期检查第十四周第十六周 撰写论文，准备答辩5 文献综述单片机基础知识简介介绍及主控电路设计在实际的应用中，基本知识的掌握程度至关重要，他影响到应用的好坏。硬件知识用来设计硬件电路，软件知识用来设计芯片处理数据的先后顺序，数据的获得途径以及对数据做怎样的处理，还有其他的一些驱动和显示功能等等。本设计用到的硬件知识主要有：电子技术、单片机技术。在电子技术方面分为模拟电子技术和数字电子技术，模拟电子技术主要用来放大传感器检测信号和驱动反光二极管以及显示穿管器检测气体浓度；数字电子技术用来把模拟量转换成数字量，把从刚起检测到的模拟量转换成数字值。利用单片机实现综合控制。主控电路中，以单片机为主体，通过分析A/D转换的得到的数字值，控制事故处理模块运行。设计采用的是AT89C51型单片机,AT89C51是一种带4K字节闪存可编程可擦除只读存储器的低电压、高性能CMOS 8位微处理器，俗称单片机。单片机的可擦除只读存储器可以反复擦除1000次。由于将多功能8位CPU和闪烁存储器组合在单个芯片中，ATMEL的AT89C51是一种高效微控制器，AT89C2051是它的一种精简版本。AT89C单片机为很多嵌入式控制系统提供了一种灵活性高且价廉的方案。气体传感器的选择对于煤气报警器的实现，感应器的选择也相当的重要，是系统重要的组成部分之一，其性能对于系统的精确度和实现范围有这相当大的影响。市面上的煤气感应器多种多样，特性价格也各有不同。根据实际应用和成本性价比，本设计一氧化碳气体传感器选择了NG-CO-001型电化学一氧化碳气体传感器。NG-CO-001型电化学一氧化碳气体传感器属工业级别产品，通过成熟的电极制备处理技术及传感器结构设计，使其具有长寿命、高灵敏度、液体密闭性良好等技术特点。传感器与外部电路连接部位通过接插元件完成，有利于传感器与电子线路的兼容与互换。A/D转换器选择本文A/D转换器选择了TLC2543，该芯片是7LC2543是德州仪器公司(TI)新型模数转换器(ADC)，具有l2位的分辨率，使用开关电容逐次逼近技术完成AD转换过程，提供的最大采样率为66KSPS，供电电流仅需1mA(典型值)。它除具有高速的转换器和通用的控制能力外，还具有通用灵活的串行接口(SPI)。它被广泛运用于数据采集系统中。气体自动控制阀的原理台湾SUNYEH电动阀门它是一种直角回转结构，它与阀门定位器配套使用，可实现比例调节；V型阀芯最适用于各种调节场合，具有额定流量系数大，可调比大，密封效果好，调节性能零敏，体积小，可竖卧安装。适用于控制气体、蒸汽、液体等介质。PVC电动调节三通球阀是阀与电动执行器组成，由调节电动执行器接受420mA信号启动旋转带动阀体转角为090从. 而打开和关闭阀门，电动执行器可搭配大部份之阀门，安裝配套容易一氧化碳传感器原理及应用监控系统最关键的部分在于室内一氧化碳气体浓度的检测，本系统考虑到室内空气中一氧化碳含量的大致范围，结合国家环境空气质量标准（GB3095-1996）规定的一氧化碳分级标准，我们选用了MOTOROLA 生产的一种专门用于家庭用途的MGS1100 型一氧化碳气体传感器，它是在微型硅桥结构中嵌入的加热器上制作一层SNO2薄膜，这种结构不仅使得SNO2薄膜对CO气体在很宽的温度范围内具有敏感性，而且硅膜减少了热传导的热损失，从而大大降低了功耗。该传感器的管脚如图所示，其中2,4 端为加热器的电源接线端，1,3为传感器输出端，其工作原理是把传感器置于CO气体环境中，SNO2薄膜层的电阻会随着CO浓度的变化而变化，CO 浓度越大，SNO2薄膜层阻值越小。图2为取得传感器输出信号的基本电路图，vh为加热电压，传感器电阻RS 与负载电阻RL串联接到工作电压VCC 两端，传感器阻值RS随着CO浓度的增大而减小时，输出负载电压VRL逐渐变大，所以通过测量负载电压即可反应出被测对象的CO浓度。由于元件的本身特性决定了其阻值会随着周围环境温度的变化产生明显的漂移，致使测量电路的输出产生零点漂移，漂移过大会造成测量的不灵敏或过灵敏，使整机的可靠性下降。为此，我们增加了温度补偿电路，如图!3所示，其中RT为热敏电阻，RS 为传感器电阻.气体传感器的信号采样气体传感器信号采样电路图如图2所示，由LM317提供加热电压。其中，HVCC是输入电压，VE是气体传感器的加热电压，VH是监测回路的工作电压，GND为气体传感器加热地，Vss为信号采样地，Rs为气体传感器的敏感体电阻，RL为取样电阻。传感器加热电压高，加热丝的电阻值小，这样势必导致流经加热回路的电流大；另外，为了方便测量，传感器探头电路与仪表数据处理电路不在同一个电路板上，而是用了比较长的数据线相连。如果采样地与加热地共用一条回路，采样地就会流过较大的电流，这样就能在信号采样线上产生很大的压降，从而导致采集的信号受信号采集线的长短影响较大。必须把加热地与信号地分离开，才能降低干扰。模数A/D转换电路此部分采用AD7810模数转换芯片，AD7810应用时几乎不需外围元件。在本设计中AD7810与AT89S52接口时，电路采用模拟串口方式，AD7810的SCLK、DOUT和CONVST分别接至AT89S52的P1.5、P1.6和P1.7。这种方式实际上可扩展到所有的MCU种类。执行电路由电磁阀启闭和排气两部分电路组成。电磁阀启闭由DAC0832、电磁阀、变送器等组成。采用AIDE的M系列二位二通节能型燃气电磁阀（直动式），当正向脉冲供电时阀门开启并保持，此时电源切断阀门为开启位置；当反向脉冲供电时阀门关闭并保持，此时电源切断阀门为关闭位置。由于电磁阀需由脉冲信号驱动，系统采用在单缓冲方式下工作的DAC0832作为波形发生器，以提供正负脉冲，使其能够自动启闭，实现安装位置的可调性。排气部分选用DAC0832、家用排风机、电磁继电器、SN75452驱动器、AC220V电源，用TPL光电隔离器使现场信号与单片机系统实现完全电隔离，提高系统抗干扰能力系统工作原理本设计为一个监控报警系统对煤气浓度进行智能地实时检测和监控、报警，能实现自动开启和关闭煤气管道阀门。系统的一氧化碳气体传感器部分作为整个系统的信号来源部分，将检测到的气体信号经A/D转换为电信号，即进行模数转换。转换得到的电信号经过单片机运算处理，与设定值进行比较，当检测值比设定值低时，系统不进行报警等一系列工作，煤气管道正常供气；当检测值比设定值高时，系统进行声光报警，显示浓度，并进行D/A转换控制关闭煤气管道阀门。键盘可以对报警浓度进行设定。通过一氧化碳气体传感器MGS1100接收一氧化碳气体信息，由AT89S52单片机构成信息处理，用MCS-51汇编语言，以达到温度显示、分析和控制的功能。整体硬件框架图如图1所示。算法实现及主程序流程图由传感器曲线和放大器增益计算得到的斜率一般为小数,而浮点计算程序比较复杂, 所以, 可以将斜率和采样数据同时放大1 000倍, 将浮点计算转化为定点计算。程序中包含定点乘法、定点除法、减法及二进制码转化为BCD码等一些常用算法。其主程序流程图如图3所示。 图3 主程序流程图外文文献摘 要: 简要介绍了一氧化碳传感器的特点、组成、工作原理及分类, 总结了一氧化碳传感器在各个领域的应用概况。探讨了一氧化碳传感器的发展前景。Application and advance of CO sensorsYANG Bang-chao, DUAN Jian-hua( Inst. of Infor. Materials Engin. , University of Electronic Science and Technology, Chengdu 610054, China)Abstract: A brief introduct ion the characterist ics, forms, working pr inciple and sorts of CO sensors are given, theg eneral situat ion of the mainly application ar eas is summarized. The CO sensor. s develop future is introduced.Key words: CO; sensor; application and advance0 前 言由于CO 与血液中的血红素的结合能力是氧的240 倍, 因此, 当它进入人体血液循环系统后, 就会大量取代氧而与血红素结合, 抑制血液中氧气的释放, 从而导致发生头痛、耳鸣、呕吐、血压降低等不同程度的症状发生。如果CO 中毒严重, 轻者于康复过程中可能会头昏眼花、丧失记忆或引起视觉及神经上的障碍, 严重者会导致脑部受损甚至发生死亡。有些国家对工作场所的CO 允许体积分数都做了规定。炼钢厂工作人员、消防人员、高速公路收费员、矿坑工作从业人员较可能暴露在高体积分数CO 环境中; 在生活中, 堵塞的交通、在密闭房间内抽烟、甚至煤气、瓦斯等不完全燃烧的室内、火灾现场等, 均可能使空气中的CO 体积分数超过允许标准。因此, 对生活, 工作环境中的CO 体积分数实施准确而有效地检测与报警是一个与人类生态和工作环境相关的重要问题。 A: Fundamentals of Single-chip Microcomputer The single-chip microcomputer is the culmination of both the development of the digital computer and the integrated circuit arguably the tow most significant inventions of the 20th century 1. These tow types of architecture are found in single-chip microcomputer. Some employ the split program/data memory of the Harvard architecture, shown in Fig.3-5A-1, others follow the philosophy, widely adapted for general-purpose computers and microprocessors, of making no logical distinction between program and data memory as in the Princeton architecture, shown in Fig.3-5A-2. In general terms a single-chip microcomputer is characterized by the incorporation of all the units of a computer into a single device, as shown in Fig3-5A-3.ProgrammemoryInput&Outputunit CPUDatamemory Fig.3-5A-1 A Harvard typeInput&Outputunit CPUmemory Fig.3-5A-2. A conventional Princeton computerTimer/Counter SystemclockExternalTimingcomponentsSerial I/O ROM Reset Prarallel I/O RAM Interrupts CPU Power Fig3-5A-3. Principal features of a microcomputer Read only memory (ROM).ROM is usually for the permanent, non-volatile storage of an applications program .Many microcomputers and microcontrollers are intended for high-volume applications and hence the economical manufacture of the devices requires that the contents of the program memory be committed permanently during the manufacture of chips . Clearly, this implies a rigorous approach to ROM code development since changes cannot be made after manufacture .This development process may involve emulation using a sophisticated development system with a hardware emulation capability as well as the use of powerful software tools. Some manufacturers provide additional ROM options by including in their range devices with (or intended for use with) user programmable memory. The simplest of these is usually device which can operate in a microprocessor mode by using some of the input/output lines as an address and data bus for accessing external memory. This type of device can behave functionally as the single chip microcomputer from which it is derived albeit with restricted I/O and a modified external circuit. The use of these ROMless devices is common even in production circuits where the volume does not justify the development costs of custom on-chip ROM2;there can still be a significant saving in I/O and other chips compared to a conventional microprocessor based circuit. More exact replacement for ROM devices can be obtained in the form of variants with piggy-back EPROM(Erasable programmable ROM )sockets or devices with EPROM instead of ROM 。These devices are naturally more expensive than equivalent ROM device, but do provide complete circuit equivalents. EPROM based devices are also extremely attractive for low-volume applications where they provide the advantages of a single-chip device, in terms of on-chip I/O, etc. ,with the convenience of flexible user programmability. Random access memory (RAM).RAM is for the storage of working variables and data used during program execution. The size of this memory varies with device type but it has the same characteristic width (4,8,16 bits etc.) as the processor ,Special function registers, such as stack pointer or timer register are often logically incorporated into the RAM area. It is also common in Harard type microcomputers to treat the RAM area as a collection of register; it is unnecessary to make distinction between RAM and processor register as is done in the case of a microprocessor system since RAM and registers are not usually physically separated in a microcomputer .Central processing unit (CPU).The CPU is much like that of any microprocessor. Many applications of microcomputers and microcontrollers involve the handling of binary-coded decimal (BCD) data (for numerical displays, for example) ,hence it is common to find that the CPU is well adapted to handling this type of data .It is also common to find good facilities for testing, setting and resetting individual bits of memory or I/O since many controller applications involve the turning on and off of single output lines or the reading the single line. These lines are readily interfaced to two-state devices such as switches, thermostats, solid-state relays, valves, motor, etc.Parallel input/output. Parallel input and output schemes vary somewhat in different microcomputer; in most a mechanism is provided to at least allow some flexibility of choosing which pins are outputs and which are inputs. This may apply to all or some of the ports. Some I/O lines are suitable for direct interfacing to, for example, fluorescent displays, or can provide sufficient current to make interfacing other components straightforward. Some devices allow an I/O port to be configured as a system bus to allow off-chip memory and I/O expansion. This facility is potentially useful as a product range develops, since successive enhancements may become too big for on-chip memory and it is undesirable not to build on the existing software base.Serial input/output .Serial communication with terminal devices is common means of providing a link using a small number of lines. This sort of communication can also be exploited for interfacing special function chips or linking several microcomputers together .Both the common asynchronous synchronous communication schemes require protocols that provide framing (start and stop) information .This can be implemented as a hardware facility or U(S)ART(Universal(synchronous) asynchronous receiver/transmitter) relieving the processor (and the applications programmer) of this low-level, time-consuming, detail. t is merely necessary to selected a baud-rate and possibly other options (number of stop bits, parity, etc.) and load (or read from) the serial transmitter (or receiver) buffer. Serialization of the data in the appropriate format is then handled by the hardware circuit.Timing/counter facilities. Many application of single-chip microcomputers require accurate evaluation of elapsed real time .This can be determined by careful assessment of the execution time of each branch in a program but this rapidly becomes inefficient for all but simplest programs .The preferred approach is to use timer circuit that can independently count precise time increments and generate an interrupt after a preset time has elapsed .This type of timer is usually arranged to be reloadable with the required count .The timer then decrements this value producing an interrupt or setting a flag when the counter reaches zero. Better timers then have the ability to automatically reload the initial count value. This relieves the programmer of the responsibility of reloading the counter and assessing elapsed time before the timer restarted ,which otherwise wound be necessary if continuous precisely timed interrupts were required (as in a clock ,for example).Sometimes associated with timer is an event counter. With this facility there is usually a special input pin ,that can drive the counter directly. Timing components. The clock circuitry of most microcomputers requires only simple timing components. If maximum performance is required,a crystal must be used to ensure the maximum clock frequency is approached but not exceeded. Many clock circuits also work with a resistor and capacitor as low-cost timing components or can be driven from an external source. This latter arrangement is useful is external synchronization of the microcomputer is required. B:PLC1PLCs (programmable logical controller) face ever more complex challenges these days . Where once they quietly replaced relays and gave an occasional report to a corporate mainframe, they are now grouped into cells, given new job and new languages, and are forced to compete against a growing array of control products. For this years annual PLC technology update ,we queried PLC makers on these topics and more .Programming languages Higher level PLC programming languages have been around for some time ,but lately their popularity has mushrooming. As Raymond Leveille, vice president & general manager, Siemens Energy &Automation .inc; Programmable controls are being used for more and more sophisticated operations, languages other than ladder logic become more practical, efficient, and powerful. For example, its very difficult to write a trigonometric function using ladder logic .Languages gaining acceptance include Boolean, control system flowcharting, and such function chart languages as Graphcet and its variation .And theres increasing interest in languages like C and BASIC.PLCs in process controlThus far, PLCs have not been used extensively for continuous process control .Will this continue? The feeling that Ive gotten, says Ken Jannotta, manger, product planning, series One and Series Six product ,at GE Fanuc North America ,is that PLCs will be used in the process industry but not necessarily for process control.Several vendors -obviously betting that the opposite will happen -have introduced PLCs optimized for process application .Rich Ryan, manger, commercial marketing, Allen-bradley Programmable Controls Div., cites PLCss increasing use such industries as food ,chemicals ,and petroleum. Ryan feels there are two types of applications in which theyre appropriate. one, he says, is where the size of the process control system thats being automated doesnt justify DCSdistributed control system.With the starting price tags of chose products being relatively high, a programmable controller makes sense for small, low loop count application .The second is where you have to integrate the loop closely with the sequential logical .Batch controllers are prime example ,where the sequence and maintaining the process variable are intertwined so closely that the benefits of having a programmable controller to do the sequential logical outweighs some of the disadvantages of not having a distributed control system.Bill Barkovitz, president of Triconex, predicts that all future controllers that come out in the process control system business will embrace a lot of more PLC technology and a lot more PLC functionality than they ever did before .Communications and MAPCommunications are vital to an individual automation cell and to be automated factory as a whole. Weve heard a lot about MAP in the last few years ,and a lot of companies have jumped on the bandwagon.2Many, however, were disappointed when a fully-defined and completed MAP specification didnt appear immediately .Says Larry Komarek: Right now, MAP is still a moving target for the manufacturers, a specification that is not final .Presently, for example. people are introducing products to meet the MAP2.1standard .Yet2.1-based products will be obsolete when the new standard for MAP3.0 is introduced.Because of this, many PLC vendors are holding off on full MAP implementations. Omron, for example, has an ongoing MAP-compatibility program;3but Frank Newburn, vice president of Omrons Industrial Division ,reports that because of the lack of a firm definition ,Omrons PLCs dont yet talk to MAP.Since its unlikely that an individual PLC would talk to broad MAP anyway, makers are concentrating on proprietary networks. According to Sal Provanzano, users fear that if they do get on board and vendors withdraw from MAP, theyll be the ones left holding a communications structure thats not supported.Universal I/OWhile there are concerns