1、- 1 - Based on AT89C52 LED overview LED (Light Emitting Diode), light-emitting diode, is a solid state semiconductor devices, which can be directly converted into electricity to light. LED is the heart of a semiconductor chip, the chip is attached to one end of a stent, is the negative side, the oth
2、er end of the power of the cathode, the entire chip package to be epoxy resin. Semiconductor chip is composed of two parts, part of the P-type semiconductor, it inside the hole-dominated, the other side is the N-type semiconductor, here is mainly electronic. But linking the two semiconductors, among
3、 them the formation of a PN junction. When the current through the wires role in this chip, will be pushing e-P, P zone in the hole with electronic composite, and then to be issued in the form of photon energy, and this is the principle of LED luminescence. The wavelength of light that is the color
4、of light, is formed by the PN junction of the decisions of the material. LED history 50 years ago, people have to understand semiconductor materials can produce light of the basic knowledge, the first commercial diodes in 1960. English is the LED light emitting diode (LED) acronym, and its basic str
5、ucture is an electroluminescent semiconductor materials, placed in a wire rack, then sealed with epoxy resin around, that is, solid package, Therefore, the protection of the internal batteries can play the role of line, so the seismic performance LED good. LED is the core of the P-type semiconductor
6、 and components of the N-type semiconductor chips, the P-type semiconductor and N-type semiconductor between a transition layer, called the PN junction. In some semiconductor materials in the PN junction, the injection of a small number of carrier-carrier and the majority of the extra time will be i
7、n the form of light energy to release, thus the power to direct conversion of solar energy. PN junction on reverse voltage, a few hard-carrier injection, it is not luminous. This use of injection electroluminescent diodes is produced by the principle of light-emitting diodes, commonly known as LED.
8、When it in a positive state of the work (that is, at both ends with forward voltage), the current flows from the LED anode, cathode, semiconductor crystals on the issue from the ultraviolet to infrared light of different colors, light and the strength of the currents. Instruments used for the first
9、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 12-inch red traffic lights as an example, is used in the United States have long life, low-efficiency 140 watt incandescent
10、 lamp as a light source, it produced 2,000 lumens of white light. The red filter, the loss-90 percent, only 200 lumens of red light. In the light of the new design, Lumileds companies have 18 red LED light source, including the loss of circuit, a total power consumption of 14 watts to generate the s
11、ame optical effect. Automotive LED lights is also the source of important areas. 沈阳工程学院毕业设计（论文） - 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 Garnet (YAG) package together cause. GaN chip of
12、the Blu-ray ( p = 465nm, Wd = 30nm), made of high-temperature sintering of the Ce3 + YAG phosphors excited by this Blu-ray after irradiating a yellow, the peak 550 nm. Blue-chip installed in the LED-based Wanxing reflection in the cavity, covered with a resin mixed with YAG thin layer, about 200-500
13、 nm. LED-based tablets issued by the Blu-ray absorption part of the phosphor, the phosphor another part of the Blu-ray and a yellow light mixed, can be a white. Now, the InGaN / YAG white LED, YAG phosphor by changing the chemical composition of the phosphor layer and adjust the thickness of the 350
14、0-10000 K color temperature can be colored white. This blue LED through the method by white, constructed simple, low-cost, 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 light-emitting
15、 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
16、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 computer, English, Chinese text and graphics, Video screen using microcomputer control, graphic,
17、image, with real-time, 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, tax
18、ation, industry and commerce, telecommunications, sports, advertising, corporations, transportation, education system, station, port, airport, hospital, shopping malls, hotels, Banks, securities market, market, and construction management of industrial enterprises, Christies and other public places.
19、 The LED display can display the change of digital image； text, graphics, Not only can be used for indoor environment can also be used in outdoor environment, projectors, LCD TV wall, and the incomparable advantages. LED by the wide attention and rapid development, and it is the advantages of itself
20、. These advantages in is: high brightness, working voltage, low consumption, miniaturization, impact resistance and long service life and stable performance. LED the development prospect, is currently towards a higher brightness, higher resistance to climate, higher and higher light shine density ev
21、enness, reliability, the direction of development. Full-color The classification of the LED display 1, the color can be divided into gezer The single color display: single colors (red or green). Double colors: red and green screen, double colors gray, can show 256 levels 65536 colors. - 3 - Full-col
22、or display: red, green, and blue, gray level 256 gezer full-color display screen can show more than 1,600 colors. 2, according to the classification of display devices LED digital display: display device for seven yards, suitable for making the clock display screen, interest rates, digital electroni
23、c display screen. Pictures of LED dot matrix LCD display device is composed of many: evenly composed of light emitting diode matrix display module, suitable for broadcast text, images of information. LED video display: display device is composed by many light-emitting diodes, video, animation shows
24、various video files. 3, by using occasions classification Indoor display: light point is lesser, general 3mm - 8mm, display area of general several ten square meters to. Outdoor screen area to several hundred square meters general dozens, high brightness, can work under the sun, in the wind, rain, w
25、aterproof function. 4 points, according to the classification of light in diameter Indoor screens: 3mm, 3.75 mm, 5mm, Outdoor screen: 10mm, 12mm and 16mm , 19mm, 20mm, 21mm, 22mm, 26mm The basic unit of the light outdoor screen for led light cone tube, the principle is a group of red, green, and blu
26、e light emitting diode sealed in a plastic tube in common 5. Display horizontally scrolling, static, vertical scroll and flip shows, etc. Single block module control drive 12 (maximum control and block), 16X48 matrix 8X8 matrix (or 32X48 matrix), is a single block of MAX7219 (or PS7219, HD7279, ZLG7
27、289 8279 and other similar LED display driver module) 12 times (or 24 times)! Can use cascade means any bitmap big screen composed. Show good effect, low consumption, and the cost of using MAX7219 circuit is lower. The LED display inspection method, See appearance, specifications, screen body flatne
28、ss, screen the attachment within 2 look bad, after the light screen is not in scope, the screen (generally now basically no) Color consistency, displays text display is normal, the picture to screen, full-color play white, red, green and blue. Technical advantage Existing common indoor full-color scheme comparison: 1 the matrix modules: design, color dot matrix LCD by indoor artifacts Advantage: the cost of raw materials, production and processing of the most advantage of simple process, quality is stable. Faults: color consistency, Mosaic phenomenon, serious effect.
