毕业论文-基于89S52单片机的烟雾报警器的设计.doc

河南机电高等专科学校毕业设计（论文）编号 基于89S52单片机的烟雾报警器的设计系 部： 自动控制系 专 业: 电气自动化 班 级: 自 104 姓 名: 学 号: 指导老师: 二零一四年四月Abstract摘 要本设计采用89S52单片机结合MQ-2传感器技术而开发设计了这一烟雾报警系统。论文中的烟雾报警器小巧轻便，适用于安装在含有爆炸性气体环境场所，还可使用于石油、化工等行业具有防爆要求的场所，可以安装在家里，也可以安装在露天、室外使用，防止和减少火灾危害，保护人身和财产安全。以89S52单片机和MQ-2烟雾传感器为核心设计的烟雾报警器可以实现烟雾报警、溶度显示、看门狗自检单片机状态功能、手动紧急报警等功能。本次设计的烟雾报警器结构简单、性能稳定、使用方便、价格便宜等优点。就有一定的使用价值。关键词：烟雾；报警器；89S52；MQ-2传感器。ABSTRACTThis design USES the 89S52 microcontroller combined with MQ-2 sensor technology and the development of design the smoke alarm system. In the paper the smoke alarm small and portable, designed for installation in contain explosive gases place, still can use in petroleum, chemical and other industries with the requirements of the explosion-proof place, can be installed in the home, can also be installed in the open air, outdoor use, and prevent and reduce the danger of fire protection of personal and property security.In 89S52 single-chip microcomputer and MQ-2 smoke sensor as the core design of smoke alarm can realize smoke alarm, solubility display, manual emergency alarm functions. The design of the smoke alarm simple structure, stable performance, easy to use, cheap price, etc. Have some use value.Key words: Smoke; alarm apparatus; 89S52; sensor1河南机电高等专科学校毕业设计论文目 录第1章 绪论11.1 论文研究来源、目的和意义11.2烟雾报警器的国内外现状21.3论文主要任务2第2章 烟雾检测报警器的方案选择42.1烟雾检测报警器设计思路42.2 烟雾传感器的介绍42.3 烟雾检测报警器整体设计方案7第3章 烟雾检测报警器的硬件设计103.1 主电路的设计与实现103.2 烟雾检测报警器硬件电路设计12第4章 烟雾检测报警器的软件实现194.1 单片机软件开发工具介绍194.2程序流程19第5章 结论22参考文献23致 谢24附 录A25附 录B26第1章 绪论1.1 论文研究来源、目的和意义 1.1.1 论文研究来源 随着社会的进步，人们的生活越来越好但也伴随着越来越多的隐患，由于在现代城市家庭里，许多人因不懂家庭安全常识引起火灾事故，使幸福家庭眼间毁于一旦,有的甚至导致家破人亡,而且一旦发生居民家庭火灾,处置不当,是造成人员伤亡的重要因素。所以说,人们应该积极了解家庭火灾的主要起因，还有预防火灾的发生。英国每年发生50000起以上的严重家庭火灾，其中大部分火灾造成人员伤亡和重大的家庭财产损失，有的还连累左邻右舍，火灾损失更加惨重。在调查火灾起因的时候，绝大多数发生火灾家庭的当事人说，以前总觉得火灾是人家的事情，与自己离得很远，没有想到这一次竟然会发生在自己的头上。 1.1.2 论文研究目的和意义 随着现代家庭采用方便的家用电器的增加，家庭火灾发生的频率越来越高。一旦家庭有火灾发生，就很容易出现扑救不及时、灭火器材缺乏以及在场人惊慌失措、逃生迟缓等不利因素，最终导致重大生命财产损失。为了保护生命安全与财产安全，人们需要实时注意避免火灾的发生，利用高科技产品有利于人们及早发现火灾的隐含，及时的避免不必要的灾难发生。为了早期发现火灾的隐患，防止和减少火灾危害，保护人身和财产安全，防止火灾引起燃烧、爆炸等事故，造成严重的经济损失与危生命安全。随着烟感报警器的使用者不断增加，住宅失火造成的死亡人数也不断下降。据美国国家消防协会报告表明，安装了推荐数目的烟感报警器的住宅一旦发生火灾，住宅内人员的逃生机会将比未安装的住宅多出502。所以家庭装有烟雾报警器灾难能够降低，避免不必要的灾难。1.2烟雾报警器的国内外现状 探测器朝新探测技术的发展进一步拓展了火灾探测的应用领域，为一些传统探测器无法胜任的环境提供了有效的手段。相关技术的发展，如傅立叶近红外光谱技术弱信号处理技术、低功耗MCU技术进一步促进了传统探测技术的改进，使得传统探测器在技术和性能上有了显著的提高。火灾着极早期探测、多传感器复合探测和探测器小型化、智能化的方向发展迈出了更快的步伐。第2章 烟雾检测报警器的方案选择2.1烟雾检测报警器设计思路此次设计是针对于单片机原理及其应用展开的。其中包含了大学四年中所学到的相关知识，运用所学的传感器技术，单片机技术去设计基于单片机的烟雾报警系统。烟雾报警器的最基本组成部分包括：烟雾传感电路、模数转换电路、单片机控制电路。单片机紧紧联系着传感器和报警电路设备，给烟雾报警器设定一个值，当外界环境达到预先设定的数值时，烟雾传感器把被测的物理量作为输入参数，转换为电量输出。为了简化整个系统的设计在本设计中不采用前置放大器而是选择数值符合A/D转换器的输入等级。模数转换电路将从烟雾传感电路送出的模拟信号转换成单片机可识别的数字信号后送入单片机。这里选择单片机的P1.0为输入方式，接收到信号的单片机经过程序的设定会由P2.0作为单片机的输出电路，单片机对该数字信号进行滤波处理，并对处理后的数据进行分析，是否大于或等于某个预设值，如果大于则启动报警电路发出报警声音，反之则为正常状态。烟雾传感器及单片机是可燃烟雾检测报警器的两大核心，根据报警器功能的需要，选择合适、精确、经济的烟雾传感器及单片机芯片是至关重要的。2.2 烟雾传感器的介绍 2.2.1 烟雾传感器的分类烟雾传感器是将空气中的烟雾浓度变量转换成有一定对应关系的输出信号的装置，烟雾传感器是一种技术先进，工作稳定可靠的传感器，被广泛运用到各种消防报警系统中。1、离子式烟雾传感器 该烟雾报警器内部采用离子式烟雾传感，离子式烟雾传感器是一种技术先进，工作稳定可靠的传感器，被广泛运用到各消防报警系统中，性能远优于气敏电阻类的火灾报警器。 它在内外电离室里面有放射源镅241，电离产生的正、负离子，在电场的作用下各自向正负电极移动4。在正常的情况下，内外电离室的电流、电压都是稳定的。一旦有烟雾窜逃外电离室。干扰了带电粒子的正常运动，电流，电压就会有所改变，破坏了内外电离室之间的平衡，于是无线发射器发出无线报警信号，通知远方的接收主机，将报警信息传递出去。2、光电式烟雾传感器 光电烟雾报警器内有一个光学迷宫，安装有红外对管，无烟时红外接收2.3 烟雾检测报警器整体设计方案 2.3.1 烟雾检测报警器工作原理 本论文中的烟雾报警器采用89S52单片机来控制核心，采用MQ-2型电阻式半导体传感器采集烟雾信息。其工作原理，首先烟雾传感器采集烟雾信息然后把烟雾信号转换为电量送入模数转换器中；接着模数转换电路将从烟雾传感电路送出的模拟信号转换成单片机可识别的数字信号后送入89S52单片机；最后，将实际可燃性气体浓度送入液晶，并判断浓度值是否超出报警门限，当浓度低于设置门限值的时候绿灯长亮，当烟雾浓度超出设定的限定值时，红灯亮并发出声音报警。 2.3.2 烟雾报警器系统类型 为适应家庭和工业等场所对可燃性易爆烟雾安全性要求，设计的可燃性烟雾报警仪应不仅能在较宽的温度范围工作，而且应具有显示可燃烟雾浓度使用89S52单片机，MQ-2烟雾传感器作为敏感元件，利用ADC0832转换器和烟雾报警电路，开发出可用于家庭或小型单位火灾报警的烟雾报警器。整个设计由4大部分构成：烟雾传感器、模数转换电路、89S52单片机、烟雾报警电路。其中，烟雾传感器是将现场烟雾浓度等非电信号转化为电信号；转换电路是将将烟雾传感器输出的模拟信号转换成数字信号。烟雾报警模块由单片机和报警电路组成，由单片机控制实现不同的声光报警功能。本系统采用高性能的单片机，工作稳定、测量精度高、通用性强、功耗低，保证报警器的精确性及可靠性，而且最好体积小，成本低，有利于减少报警器的体积，降低报警器的成本。烟雾浓度烟雾传感器ADC083289S52烟雾报警图2-1 烟雾报警的系统结构图29第3章 烟雾检测报警器的硬件设计3.1 主电路的设计与实现89S52单片机是报警仪的设计中最核心的部件，一方面它控制A/D转换器实现模拟信号到数字信号的转换，另一方面，将采集到的数字电压值经计算机处理得到相应的二进制代码，与设定的值作比较。整个系统的软件编程就是通过C语言对单片机89S52实现其控制功能。3.1.1 AT89S52单片机介绍AT89S52为ATMEL所生产的一种低功耗、高性能CMOS8位微控制器，具有8K在系统可编程Flsah存储器10。AT89S52实物图与结构图由图3-1、3-2所示。该单片机可反复擦写1000次的FLASH只读程序存储器，器件采用ATMEL公司之高密度、非易失性存储技术制造，兼容标准MCS-51指令系统及80C51引脚结构，片上Flash允许程序存储器在系统可编程，亦适于常规编程器。由图3-2可见，89S52单片机主要由以下部分组成：CPU系统：8位CPU；含布尔处理器；时钟电路；总线控制逻辑。存储器系统：8KB的程序存储器（ROM/EPROM/Flash，可扩至64KB）；128KB数据存储器（RAM，可再扩64KB）；特殊功能寄存器SFR。图3-1 89S52单片机实物图第4章 烟雾检测报警器的软件实现4.1 单片机软件开发工具介绍 KeilC51是美国KeilSoftware公司出品的51系列兼容单片机C语言软件开发系统，与汇编相比，C语言在功能上、结构性、可读性、可维护性上有明显的优势，因而易学易用17。用过汇编语言后再使用C来开发，体会更加深刻。KeilC51软件提供丰富的库函数和功能强大的集成开发调试工具，全Windows界面。另外重要的一点，只要看一下编译后生成的汇编代码，就能体会到KeilC51生成的目标代码效率非常之高，多数语句生成的汇编代码很紧凑，容易理解。在开发大型软件时更能体现高级语言的优势。KEILC51标准C编译器为80C51微控制器的软件开发提供了C语言环境,同时保留了汇编代码高效,快速的特点。C51编译器的功能不断增强，更加贴近CPU本身，及其它的衍生产品。C51已被完全集成到uVision2的集成开发环境中，这个集成开发环境包含：编译器，汇编器，实时操作系统，项目管理器，调试器。uVision2IDE可为它们提供单一而灵活的开发环境。4.2程序流程 在整个程序流程中，经常要控制一部分指令重复执行若干次，以便简短的程序完成大量的处理任务。这种按某种控制规律重复执行的程序称为循环程序。循环程序有先执行后判断何先判断后执行两种基本结构。而我们要选用的是先判断后执行。MQ-2刚开始的时候不能马上检测烟雾，需要等通电一会后才能正常工作，程序初始化结束后系统进入工作状态。89S52单片机对传感器检测到的烟雾信号进行模数转换，然后与设定的门限值进行比较，如果超过预算门限值蜂鸣器报警，同时把烟雾浓度值送入显示管显示，没有超过门限值继续进入监控工作状态。程序初始化子程序，这部分实现的功能包括各种I/O口输入输出状态的设定、寄存器初始化、中断使能等。首先设定定时初值50ms，利用IAP写入EEPROM，作为取值间隔。然后设置定时器0，选择方式1。方式1状态下定时器的工作寄存器TH1、TL1是全16位参与操作。接下来定时器0中断允许位置1，打开定时器0，关闭蜂鸣器，开启绿灯，设置报警限初值。Y开始初始化传感器预热、故障检测键盘处理报警限设置报警子程序平均值法滤波线性化处理设置指示灯状态YN是否按模式切换A/D转换N是否超报警限浓度显示图4-1主程序流程图第5章 结 论随着技术越来越成熟烟雾报警器成为保障生产与生活的安全一个重要的工具，避免火灾和爆炸事故的发生，是人们生活中一项重要的发明，具有广阔的市场空间与发展前景。 本烟雾报警器由烟雾信号采集电路与单片机控制电路两大部分构成。 根据设计要求、使用环境、等因素，选用MQ-2型半导体烟雾传感器。该传感器常用于家庭和工厂的气体泄漏装置，适宜于液化气、丁烷、丙烷、甲烷、酒精、氢气、烟雾等的探测，它的灵敏度适中，长期工作稳定性、重现性、不易受环境影响及抗温湿度影响等优点。 在系统单片机控制电路的设计上，采用了89S52单片机作为核心芯片，使仪器具有结构简单、性能稳定、体积小、成本低等优点。为提高响应时伺，保证传感器准确地、稳定地工作，需要向烟雾传感器持续供给5V的加热电压。 当烟雾传感器检测到一定的浓度的烟雾，传感器把烟雾信号送入到模数转换器中进行转换，把模拟信号转换成数字信号送入单片机，单片机对送入的信号进行处理，大于预定值的浓度，报警电路报警。本设计的报警器小巧轻便，方便安装。在现代社会中由于家庭火灾和有害气体中毒而导致死亡的人越来越多，每年给社会带来了很大的财产损失和社会负担。由于家庭火灾具有突发性，如果发现不及时很容易给家庭造成重大损失。然而文章设计的烟雾报警器可以很好的解决这个问题。文章以单片机为控制主体，烟雾传感器作为烟雾浓度探测器。由于报警器具有很高的灵敏度，即使在很低的浓度下也可以进行探测，而且还具有实时性，可以在最快的时间内对火灾发生前的物理和化学现象进行探测并发出报警，以提醒用户和其他人，因此它可以很好地减少家庭发生火灾的频率，能够保障人们生活的和财产的安全，是提供安全的生活环境所必备的仪器，具有十分广阔的市场空间和发展前景。 参考文献1彭军. 传感器与检测技术. 西安电子科技大学出版社, 2003: 263315 2李永生, 杨莉玲. 半导体气敏元件的选择性研究. 传感器技术, 2002(3): 13 3Yoon D h, Yu J h, Choi Gm. CO Gas Sensing Properties of Zn0-CuO Composite. Sensors and Actuators. 1998(46): 1523 4蔡文斋. 专业级串口调试器设计. 现代电子技术, 2006(23): 6972 5Wang Xi huai，Xiao Jian mei，Bao Minzhong. Multi-sensor Fire Detection Algorithm for Ship Fire Alarm System Using Neural Fuzzy Network. Signal Processing Proceedings. 2000(3):16021605 6张鹏翼, 罗卫兵, 楼超英. 基于STC单片机的无人飞机控系统设计. 设计参考, 2006, 18: 2325 7求是科技. 单片机应用系统开发实例导航. 人民邮电出版社, 2003. 8何衍庆. 控制系统分析设计和应用. 化学工业出版社, 2003. 9郑郁正. 单片机原理及应用. 四川大学出版社, 2003: 2556 10N kansah F D. Technology and reliability of submicron 1 T2 flash EEPROM. UMI Number :9995534. Bell &Howell Information and Learning Company, 2001: 2 11De Salvo B, Ghibaudo G. Pananakak is Getal. Experimental and theoretical investigation of nonvolatile memory data-retention. IEEE Trans Electron Devices, 1999, 46 (7): 1518 12黄再银. 带看门狗和电源监控功能的复位芯MAX813L. 电子世界, 2003(3): 3940 13黄新友, 高春华. 烧结温度对大功率超薄型压电蜂鸣器用压电陶瓷结构和性能 的影响. 中国陶瓷工业. 2003,10(2): 2224 14 于冶会. 对调整仪表用蜂鸣器振动规范的探讨. 传感器世界,2000 (1): 3538 15邵子扬, 黄保明, 刘海涛. Keil软件仿真的串口调试技巧. 单片机与嵌入式系统应用, 2006(7): 7678 16Keil Software. Cx51 Complier Users Guide. Keil Software, 2001 17Keil Software. Macro Assembler and Utilities Users Guide. Keil Software, 200118陈晓莉, 张俊涛. KEIL C51单片机仿真器的设计.微计算机信息(嵌入式与SOC), 2006,2(2): 1920致 谢在本次论文的写作过程中遇到了无数的困难和障碍，都在同学和老师的帮助下度过了。感谢我的同学和朋友，在我写论文的过程中给予我很多的素材，还在炉温撰写和排版过程中提供热情帮助，由于我的水平有限，所写论文难免有不足之处，恳请各位老师们给予批评和指正，三年的大学生活在这个季节即将划伤一个句话，而于我的人生却只是一个逗号，我将面对又一次征程的开始，三年来的求学生涯，在老师、同学们的帮助下，走得辛苦却也收获颇丰。可是我更急切地要把我的敬意和赞美献给每一位教过我的老师，在相处的日子中，老师们严谨的治学，渊博的学识，深邃的思想，雄阔的视野，为我营造了一种良好的精神氛围，授人以鱼不如授人以渔，置身其间，耳濡目染，潜移默化，使我不仅接受了全新的思想观念，树立了宏伟的学术目标，领会了基本的思考方式从论文题目的选定到论文写作的指导，经由您悉心的点拨，再经思考后的领悟，常常让我有山重水复疑无路，柳暗花明又一村。再次感谢自控系的所有老师，祝愿你们在今后工作生活中一帆风顺，心想事成。附 录 A本论文烟雾报警器设计实物图附 录B硬件电路图为你提供优秀的毕业论文参考资料，请您删除以下内容，O(_)O谢谢！2 Many people have the same mixed feelings when planning a trip during Golden Week. With heaps of time, the seven-day Chinese为你提供优秀的毕业论文设计参考资料，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 th