【正文】 nd the strength of the currents. Instruments used for the first LED light source instructions, but all kinds of light colored LED lights in traffic and large screen has been widely applied, have a very good economic and social benefits. The 12inch red traffic lights as an example, is used in the United States have long life, lowefficiency 140 watt incandescent lamp as a light source, it produced 2,000 lumens of white light. The red filter, the loss90 percent, only 200 lumens of red light. In the light of the new design, Lumileds panies have 18 red LED light source, including the loss of circuit, a total power consumption of 14 watts to generate the same optical effect. Automotive LED lights is also the source of important areas. 沈陽工程學院畢業(yè)設計（論文） 2 For general lighting, people need more white light sources. The 1998 white LED successful development. This is the GaN LED chip and Yttrium Aluminum Gar (YAG) package together cause. GaN chip of the Bluray (λ p = 465nm, Wd = 30nm), made of hightemperature sintering of the Ce3 + YAG phosphors excited by this Bluray after irradiating a yellow, the peak 550 nm. Bluechip installed in the LEDbased Wanxing reflection in the cavity, covered with a resin mixed with YAG thin layer, about 200500 nm. LEDbased tablets issued by the Bluray absorption part of the phosphor, the phosphor another part of the Bluray and a yellow light mixed, can be a white. Now, the InGaN / YAG white LED, YAG phosphor by changing the chemical position of the phosphor layer and adjust the thickness of the 350010000 K color temperature can be colored white. This blue LED through the method by white, constructed simple, lowcost, high technology is mature, so use the most. In the 1960s, the use of science and technology workers semiconductor PN junction of The principle of developing a LED lightemitting diodes. At that time, the development of LED, the materials used are GaASP, its luminous color is red. After nearly 30 years of development, and now we are very familiar with the LED, has been sent to red, orange, yellow, green, blue, and other shade. However lighting necessary for white LED light only in recent years to develop, readers here to tell us about lighting with white LED. The LED display screen and video display into the text by LED matrix blocks. Graphic display can be displayed with puter, English, Chinese text and graphics, Video screen using microputer control, graphic, image, with realtime, synchronization, clear information dissemination way play all kinds of information, but also shows 2d, 3d animation, videos, TV, VCD programs and live. The LED display screen display bright colors, stereo sense is strong, such as oil, such as films, widely used in finance, taxation, industry and merce, telemunications, sports, advertising, corporations, transportation, education system, station, port, airport, hospital, shopping malls, hotels, Banks, securities market, market, and construction management of industrial enterprises, Christie39。當電流通過導線作用于這個晶片的時候，電子就會被推向 P 區(qū)，在 P 區(qū)里電子跟空穴復合，然后就會以光子的形式發(fā)出能量，這就是 LED 發(fā)光的原理。 當它處于正向工作狀態(tài)時（即兩端加上正向電壓），電流從 LED 陽極流向陰極時，半導體晶體就發(fā)出從紫外到紅外不同顏色的光線，光的強弱與電流有關。這種 LED是將 GaN 芯片和釔鋁石榴石（ YAG）封裝在一起做成。經(jīng)過近 30 年的發(fā)展， 7 現(xiàn)在大家十分熟悉的 LED，已能發(fā)出紅、橙、黃、綠、藍等多種色光。LED 的發(fā)展前景極為廣闊，目前正朝著更高亮度、更高耐氣候性、更高的發(fā)光密度、更高的發(fā)光均勻性，可靠性、全色化方向發(fā)展。室外顯示屏：面積一般幾十平方米至幾百平方米，亮度高，可在陽光下工作，具有防風、防雨、防水功能。二看屏點亮后壞點，在不在不范圍之內，（一般來說現(xiàn)在的屏基本上沒有了）色差一致性，顯示文字是否正常，顯示屏圖片等，全彩的要全屏打白色，紅，綠，藍。加工較復雜，抗靜電要求高?？臻e模式下， CPU停止工作，允許 RAM、定時器 /計數(shù)器、串口、中斷繼續(xù)工作。在 flash編程時，此引腳（ PROG ）也用作編程輸入脈沖。當 AT89S52從外部程序存儲器執(zhí)行外部代碼時， PSEN 在每個機器周期被激活兩次，而在訪問外部數(shù)據(jù)存儲器時， PSEN 將不被激活。外部程序存儲器和數(shù)據(jù)存儲器都可以 64K尋址。用戶軟件不應給這些位寫 1。 參考資料： 1． ATMEL公司 AT89C52的技術手冊 2．深圳市中源單片機發(fā)展有限公司 AT89C52 3．復旦大學出版社單片微型機原理、應用和實驗張友德等