本科毕业论文-基于AT89C51单片机的便携式电子称设计.doc

基于AT89C51单片机的便携式电子称设计摘 要日常生活中人们很多地方需要用到便携式电子秤，人们对便携式电子秤的要求也越来越高，大家期望能够让电子秤体积变小，功耗低，精度高，使用年限长。因此本文设计了一种新型电子秤，它的量程为05kg，最小分辨率可达到0.1g。该电子秤已经足够满足人们日常生活中的使用。本文介绍了该系统的各部分组成。包括传感器，电源电路，信号放大，A/D转换，输出显示，超重报警，单片机最小系统。在硬件电路中详细介绍了系统各部分电路，给出了仪器电路相关流程图，电路图。并利用proteus仿真软件进行仿真。以及利用LabVIEW软件设计该产品的虚拟模拟界面，深刻解读该系统。该系统主要由51单片机来控制，测量物体重量部分由双孔悬臂梁力传感器测量，经过差动放大器为信号进行放大，再利用A/D转换器转换成数字信号输入至单片机中，再通过LCD显示重量。系统还设置了超重报警功能，保护仪器，防止超重对传感器的破坏。因此该电子秤俱备了体积小、操作简单、精度高，性价比高、功耗低、系统设计简单、速度快等优点。关键词：双孔悬臂梁力传感器，51单片机，A/D转换，电子秤目 录摘 要2目 录31 引言41.1课题的背景和意义41.2本论文主要工作42总体设计方案52.1传感器52.2信号放大器62.3A/D转换72.4单片机系统82.4.1 LCD显示.92.4.2 超重报警.92. 5 电源部分.103传感器选型.104 LabVIEW仿真.135总结与展望.14参考文献14附 录151 引言1.1 课题的背景和意义 随着科学技术的发展，时代的进步，人们对在生产和生活着对秤的要求越来越高，在有些方面需要量程比较大的秤，而在有些地方则需要量程小，精度高的秤。目前，台式电子秤在商业贸易中的使用已相当普遍，但存在较大的局限性：体积大、成本高、需要工频交流电源供应、携带不便、应用场所受到制约。现有的便携秤为杆秤或以弹簧压缩、拉伸变形来实现计量的弹簧秤，居民用户使用的是国家已经明令淘汰的杆秤。随着时代的发展，人们一直希望能够有携带方便，精度高，功耗小的便携式电子秤。1.2 本论文主要工作 本文主要是向大家介绍一种新型的便携式电子秤，该电子秤的量程05kg，最小分辨率可达到0.1g。该电子秤已经足够满足人们日常生活中的使用。本文详细介绍了该系统的各部分组成。包括传感器，硬件电路，输出显示，超重报警。在硬件电路中详细介绍了系统各部分电路，给出了仪器电路相关流程图，电路图。并利用proteus仿真软件进行仿真。以及利用LabVIEW软件设计该产品的虚拟模拟界面，深刻解读该系统。本系统主要由AT89C51单片机来控制，测量物体重量部分由双孔悬臂梁力传感器测量，经过差动放大器为信号进行放大，再利用A/D转换器转换成数字信号输入至单片机中，在通过LCD将重量显示出来。系统还设置了超重警报功能，保护仪器，防止超重对传感器的破坏。因此该电子秤俱备了体积小、操作简单、精度高，性价比高、功耗低、系统设计简单、速度快等优点。2 总体设计方案图1 系统原理框图 系统总体方案设计如图1所示，它是由悬臂梁力传感器模块，放大电路模块，A/D信号转换器模块，AT89C51单片机模块，数据显示模块，超重报警模块构成。该电子秤还设有一个电源开关按键。2.1 传感器由于本系统要求称重在0至5kg范围内，且最小分辨率为0.1g。因此传感器部分主要是用双孔悬臂梁力传感器进行测量重量如图1所示，它是一种高精度，性能优良，适合小量程的称重测力传感器，采用弹性梁和应变片作转换元件。当力作用在弹性元件（梁）上时，金属与应变片一起变形使应变片的电阻变化。图1双孔悬臂梁力传感器原理图在传感器的测量电路方面，本系统要求的最小分辨率为0.1g，因此采用全桥差动电路。它不仅能消除非线性误差，而且还使电桥的输出灵敏度是单臂工作时灵敏度的四倍，同时还具有温度补偿的作用。单臂电桥工作时，半桥差动电路工作时，全桥差动电路工作时，由上可知，全桥差动电路是最适合传感器测量电路。如图2所示图2全桥差动电路2.2 信号放大器该系统的传感器输出电压幅值范围030mV。而A/D转换器的输入电压要求为03V，因此该放大电路的增益必须为100左右。对放大环节的要求是增益可调的（80130倍），根据本设计的实际情况增益设为100倍即可，零点和增益的温度漂移和时间漂移极小。因此放大电路主要由高精度低漂移运算放大器构成差动放大器，而构成的前级处理电路；差动放大器具有高输入阻抗，增益高的特点，可以利用普通运放OP07做成一个差动放大器。如图3所示。图3差动放大电路2.3 A/D转换目前，世界上有多种类型的ADC，有传统的并行、逐次逼近型、积分型ADC，也有近年来新发展起来的-型和流水线型ADC，多种类型的ADC各有其优缺点并能满足不同的具体应用要求。该系统中对物体重量测量的量程为0至5kg，精度为0.1g，精度要求不高，仪器使用的场合要求不高，A/D转换的速率要求也不高，而双积分型A/D转换器精度高，具有精确的差分输入，重要的是输入阻抗高，有自动调零功能，有超量程信号输出，全部输出于TTL电平兼容。且双积分型A/D转换器具有很强的抗干扰能力。对正负对称的工频干扰信号积分为零，所以对50Hz的工频干扰抑制能力较强，对高于工频干扰已有良好的滤波作用。只要干扰电压的平均值为零，对输出就不产生影响。 因此综上所述，根据系统的精度要求以及综合的分析其优点和缺点，该系统采用了12位A/D转换器AD574。电路连接如图7所示图7 A/D转换电路2.4 单片机系统该系统采用MCS-51系列的AT89C51单片机，AT89C51单片机有4k 字节Flash 闪速存储器，128字节内部RAM，32 个I/O 口线，两个16位定时/计数器，一个5向量两级中断结构，一个全双工串行通信口，片内振荡器及时钟电路。同时，AT89C51可降至0Hz的静态逻辑操作，并支持两种软件可选的节电工作模式。空闲方式停止CPU的工作，但允许RAM，定时/计数器，串行通信口及中断系统继续工作。掉电方式保存RAM中的内容，但振荡器停止工作并禁止其它所有部件工作直到下一个硬件复位。单片机的引脚图如图4所示 图4单片机引脚图2.4.1 LCD显示该系统采用LCD来显示重量，由于是便携式电子秤，因此需要耗能低的组件，而利用LED数码管显示的话，它的功耗比较高，因此使用LCD来做显示电路，可以节省电能消耗。LCD电路与单片机的电路连接如图5所示。图5系统显示电路2.4.2 超重报警对于电子秤而言，超重报警是必不可少的部分，因为如果测量的物体长期超过传感器所承受的范围内，可能会导致传感器无法复原，产生严重的偏差，最终导致测量结果不准确。因此在超重报警中，通过A/D转换器转换进来的信号，在单片机内部进行比较，如果超过量程5kg范围内，则在单片机的P2.0口输出高电平，在报警电路中有发光二极管，蜂鸣器，NPN三极管，限流电阻。当P2.0为高电平时，三极管导通，蜂鸣器想起，发光二极管发亮。具体原理如图6所示。图6报警电路2.5 电源部分该系统的传感器部分需要12V的直流电压，其余芯片单片机之类的需要5V的直流电压。因此本系统通过接入220V的交流电，经过变压器降压，通过整流滤波电路将交流电变成直流电，再通过稳压二极管来控制电压，输出正负12V，正负5V的直流电压。具体电路如图8所示。图8电源电路3 传感器选型根据本系统的设计方案，在市场上发现有两款传感器，第一款是由蚌埠恒远传感器有限公司生产的HYXB-021小量程悬臂梁传感器。第二款是由博林公司生产的BL801平行梁传感器。两款传感器在内部参数上都非常的接近，但是在外形上，第一款传感器的体积要比第二款传感器要小，由于该系统设计的是便携式传感器，因此，我们就选择了第一款由蚌埠恒远传感器有限公司生产的HYXB-021小量程悬臂梁传感器。传感器介绍如下：HYXB-021小量程悬臂梁传感器如图11传感器实物图图12传感器外形图额定负荷1，2，5（kg）额定输出1.0 0.15mV/V非线性0.03 %F.S滞后0.03 %F.S重复性0.03 %F.S蠕变(5分钟)0.03 %F.S输出温度影响0.01 %F.S/零点温度影响0.05 %F.S/零点平衡0.1000 mV/V输入阻抗111510% 输出阻抗100010% 绝缘阻抗1000 M安全过载率150 %F.S极限过载率200 %F.S工作温度范围-2060 推荐工作电压512 VDC最大工作电压15 VDC材质铝合金防护等级IP65电缆0.825 cm台面尺寸150150 mm接线方式红：电源+，黑：电源-，绿：信号+，白：信号-传感器尺寸：80x2.7x12.7mm规格：1kg 2kg 5kg 满量程输出电压=激励电压x灵敏度1.0mv/v例如：供电电压是5v乘以灵敏度1.0mv/v=满量程5mv接线:红线输入电压+ 黑线输入电压-绿线输出信号+白线输出信号-4 LabVIEW仿真该系统利用随机数产生0-8之间的数来模拟物体的重量，包括了超重部分，当产生的数字超过5时会发出警报并将重量显示置0，系统中还有一个总开关进行控制。因此该系统能够形,象的模拟出生活中的各种状况。图9Labview前面板图10 labview程序框图5 总结与展望 便携式电子秤一共涉及到传感器，电源供电，信号放大及转换，利用单片机来控制整个系统，再显示在LCD液晶显示屏，超重报警等方面，该产品属于新型的便携式电子秤，在精确度方面相比以前提高了很多，该产品的精确度为0.1g。如果按照我们的方案来设计生产该产品，一定能够满足市场需求。而且该产品的价格低廉，携带方便，结构简单。但是产品的不足之处是无法调节产品的量程，由于传感器是5kg的量程，因此电子秤也不能为用户提供量程转换功能。今后通过继续努力研究与学习，利用更好的传感器来解决该问题，则可以满足更多的用户来使用该产品。参考文献1 马修水，钟伟红，陈琢等 传感器与检测技术M浙江：浙江大学出版社，20092 李林功，吴飞青，王兵等单片机原理与应用M北京：机械工业出版社，2007:96-1203 刘刚，王立香，张连俊LabVIEW8.20中文版编程及应用M北京：电子工业出版社，2007附 录产品介绍说明：使用说明：接入220v的家庭用电，打开电源开关即可使用，使用时注意请勿渗入水，可能会引起产品短路。请勿在载物台上放置超过5kg量程的物体。使用完毕后请关闭电源，节约能源。请您删除一下内容，O(_)O谢谢！Many people have the same mixed feelings when planning a trip during Golden Week. With heaps of time, the seven-day Chinese请您删除一下内容，O(_)O谢谢！National Day holiday could be the best occasion to enjoy a destination. However, it can also be the easiest way to ruin how you feel about a place and you may become more fatigued after the holiday, due to battling the large crowds. During peak season, a dream about a place can turn to nightmare without careful planning, especially if you travel with children and older people. As most Chinese people will take the holiday to visit domestic tourist destinations, crowds and busy traffic are inevitable at most places. Also to be expected are increasing transport and accommodation prices, with the possibility that there will be no rooms available. It is also common that youllwait in the line for one hour to get a ticket, and another two hours at the site, to only see a tiny bit of the place due to the crowds. Last year, 428 million tourists traveled in China over the week-long holiday in October. Traveling during this period is a matter that needs thorough preparation. If you are short on time to plan the upcoming Golden Week it may not be a bad idea to avoid some of the most crowded places for now. There is always a place so fascinating that everyone yearns for. Arxan is a place like this. The beauty of Arxan is everlasting regardless of the changing of four seasons. Bestowed by nature, its spectacular seasonal landscape and mountains are just beyond word. Arxan is a crucial destination for the recommended travelling route, China Inner Mongolia Arxan Hailar Manzhouli. It is also the joint of the four prairies across the Sino-Mongolian border, where people gravitate towards the exotic atmosphere mixed with Chinese, Russian, and Mongolia elements. As a historic site for the Yitian Battle, Arxan still embodies the spirit of Genghis Khan. Walking into Arxan, you will be amazed by a kaleidoscope of gorgeous colors all the year round - the Spring azaleas blooming red in the snow, the Summer sea wavering blue in the breeze, the Autumn leaves painted in yellow covering volcanic traces, and the Winter woods shining white on the vast alpine snowscape. Hinggan League Arxan city is situated in the far eastern area of Inner Mongolia Autonomous Region. Its full name Haren Arxan means hot holy water in the Mongolian language. Arxan is a tourism city in the northern frontier with a blend of large forest, grand prairies, vast snowfield, heaven lake cluster, thermium, as well as volcanic cluster. It is a rare and unique ecotourism base filled with healthy sunshine, clean air and unspoiled green. Nestled close to the countrys largest virgin forest, and known for its spring and ecological environment, Arxan is marveled at by many tourists as the purest land on earth. You cannot miss out the Autumn of Arxan. It is definitely the best with brightly-colored scenery full of emotions. Autumn in the northern part of the country comes earlier than the South. A September rain followed by the footprints of Autumn brings more colors to the once emerald green mountain and blooming grassland. Shutterbugs flock to see for themselves the marvel of splendid colors around the mountains and waters, many of whom have travel a long distance and even camp here only to capture a moment of the nature wonder. The silver birch turns golden, while the larch is still proudly green. You will find yourself drowned in the intoxicating red of the wild fruits as well as the glamour of flowers in full blown. And your heart will be lingering on the woods as its time for the wild fruits to ripe. The picturesque Arxan in Autumn is indeed a fairyland only exists in a dream that satisfies all your fantasies. If itrains heavily on Saturday night, some elderly Chinese will say it is because Zhinu, or the Weaving Maid, is crying on the day she met her husband Niulang, or the Cowherd, on the Milky Way. Most Chinese remember being told this romantic tragedy when they were children on Qixi, or the Seventh Night Festival, which falls on the seventh day of the seventh lunar month, which is usually in early August. This year it falls on Saturday, August 2. Folklore Story As the story goes, once there was a cowherd, Niulang, who lived with his elder brother and sister-in-law. But she disliked and abused him, and the boy was forced to leave home with only an old cow for company. The cow, however, was a former god who had violated imperial rules and was sent to earth in bovine form. One day the cow led Niulang to a lake where fairies took a bath on earth. Among them was Zhinu, the most beautiful fairy and a skilled seamstress. The two fell in love at first sight and were soon married. They had a son and daughter and their happy life was held up as an example for hundreds of years in China. Yet in the eyes of the Jade Emperor, the Supreme Deity in Taoism, marriage between a mortal and fairy was strictly forbidden. He ordered the heaven troop to catch Zhinu back. Niulang grew desperate when he discovered Zhinu had been taken back to heaven. Driven by Niulangs misery, the cow told him to turn its hide into a pair of shoes after it died. The magic shoes whisked Niulang, who carried his two children in baskets strung from a shoulder pole, off on a chase after the empress. The pursuit enraged the empress, who took her hairpin and slashed it across the sky creating the Milky Way which separated husband from wife. But all was not lost as magpies, moved by their love and devotion, formed a bridge across the Milky Way to reunite the family. Even the Jade Emperor was touched, and allowed Niulang and Zhinu to meet once a year on the seventh night of the seventh month. This is how Qixi came to be. The festival can be traced back to the Han Dynasty (206 BC-AD 220). Traditionally, people would look up at the sky and find a bright star in the constellation Aquila as well as the star Vega, which are identified as Niulang and Zhinu. The two stars shine on opposite sides of the Milky Way. Customs In bygone days, Qixi was not only a special day for lovers, but also for girls. It is also known as the Begging for Skills Festival or Daughters Festival. In this day, girls will throw a sewing needle into a bowl full of water on the night of Qixi as a test of embroidery skills. If the needle floats on top of the water instead of sinking, it proves the girl is a skilled embroiders. Single women also pray for finding a good husband in the future. And the newly married women pray to become pregnant quickly. Tradition transformed The love story of Niulang and Zhinu, and the Qixi Festival have been handed down for generations. Yet these ancient traditions and customs are slowly dying out. Many modern Chinese, particularly youngsters, seem to know more about St Valentines Day on February 14, characterized by bouquets of roses, chocolates and romantic candlelight dinners, than they do about their home-grown day for lovers. Even Qixi is nowadays referred to as the Chinese Valentines Day. More and more young Chinese people begin to celebrate this day in a very similar way as that in western countries. Fewer people than ever will gaze at the heavens on Saturday to pick out the two stars shining bright on either side of the Milky Way, that is, if people even know on which day Qixi falls. There are ready reminders dotted about, in the form of big ads saying Sales on Chinese Valentines Day! in shops, hotels and restaurants. But few young women will mark the festival with their boyfriends, or take part in traditional activities to pray for cleverness. A large-scale of exhibition on the Silk Road opened to the public in the National Museum on Thursday. The exhibition displays more than 400 treasures from Shaanxi province, Gansu province and 14 other regions. It is largest scale exhibition that shows the history of the Silk Road in recent years. AsAPECis going on in Beijing, the exhibit aims to show the world this brilliant section of history. The Silk Road is a series of trade and cultural transmission routes that were central to cultural interaction through regions of the Asian continent. It connected the West and East by linking traders, merchants, pilgrims, monks, soldiers, nomads, and urban dwellers from China and India to the Mediterranean Sea during various periods of time. I met my dear hubby in 2009 the second year I was in my school and it was the first year when he came here. We became colleagues. And there was nothing special happening during that year. He was just a kind and humble brother graduated from the same college as me. But we did not know each other till he became my colleague and his office desk was just in front of me. There was only a glass between us. So actually we could see each other when we both look up. But it is not the main reason that really draws us close. How we become close to each other was something seems quite natural. We went out to play badminton with other colleagues and we sometimes chatted for a while. He is a man of few words but somehow sometimes will say something really humorous. Then one day, to my great surprise, I found a pot of beautiful flower on my desk. It was just the flower I had talked about with my colleague the other day, and I thought it was her who put the flower there. But the truth is not. It was the humble guy sitting in front of me. He just simply said ,”well, I caught sight of this flower and thought that its beautiful and you may like it”. I wonder why I was moved because of these simple words and present. Maybe it is the sincerity and the true self that impress me. I thanked him and some colleagues walked past my desk would appreciate the beautiful flower and they noticed that something romance happened there. Then later on, there were some little surprises once in a while. Once, there was something wrong with my drawer and I had complained about it unconsciously. And he fixed it for me. Then the other day, he placed several pink diamond roses beside the flower with a piece of paper saying” I love you more than I can say! Diamond stands for marriage, rose stand for love. I hope you are mine, become my wife. You are the only girl who I really want to spend the rest of my life to stand by.” Although there were some grammar errors but I got what he meant. He meant so clear and so direct. And actually, I accepted him some days earlier. I was just waiting for him to break the ice. So finally, the common interests and the common understanding brought us together. Some people say the relationship and the feeling will change after getting hitched. You will find that love is no longer strong and there is always lack of passion and whats worse you may find out many bad habits of your partner, which never appear when you are first in love before the marriage. It seems that many faults turn up after you truly living together and see each others face the moment you open your eyes in the early morning. But after almost 4 years from now, I do not feel any negative change in our relationsh