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led displays: big screen exhibit at science city
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One large size LED display screen has installed at Gujarat Science City for the visitors as an out door exhibit. The LED screen having dimension of 20' x 12' size and uses 1,84,320 tiny LEDs to play a character or to depict the story lines. The screen can display 53 characters in 24 lines in English language.
If you have a magnifying glass handy, hold it over a photograph in a magazine or a book. You will see thousands of colored dots or pixels, which make up the screen of the photograph. At close range, these dots are quite noticeable, but at normal viewing distances, you do not see the dots, just the image that they form. This gives the concept of LED dots in big characters.
A light-emitting diode (LED) is a semiconductor device that emits incoherent monochromatic light when electrically biased in the forward direction. This effect is a form of electroluminescence. The color depends on the semiconducting material used, and can be near-ultraviolet, visible or infrared. Nick Holonyak Jr. (1928) of the University of Illinois at Urbana-Champaign developed the first practical visible-spectrum LED in 1962. Since then, the technology has been
LEDs are, essentially, little colored light bulbs. Modern LEDs are small, extremely bright and use relatively little power for the light that they produce. Other places one can find LEDs used in outdoors like traffic lights and automobile brake lights.
On a color CRT television set, all of the colors are produced using red, green and blue phosphor dots for each pixel on the screen. In a jumbo TV, red, green and blue LEDs are used instead of phosphor. A "pixel" on a jumbo TV is a small module that can have as few as three or four LEDs in it (one red, one green and one blue). In the biggest jumbo TVs, each pixel module could have dozens of LEDs. Pixel modules typically range from 4 mm to 4 cm (about 0.2 to 1.5 inches) in size.
To large LED screen has been operated through a Pentium III computer system having specialized software along with a power control system and a lot of internal wiring is required for normal operation.
The computer system looks at the incoming TV signal and decides which LEDs it will turn on and how brightly. The computer samples the intensity and color signals and translates them into intensity information for the three different LED colors at each pixel module.
The power system provides power to all of the LED modules, and modulates the power so that every LED has the right brightness. Turning on all of those LEDs can use a lot of power. A typical 20 x 12' LED screen can consume up to 1.2 watts per pixel, or approximately 300,000 watts for the full display.
Several wires run to each LED module, so there are a lot of wires running behind the screen.
The model T19.05K 192 x 320 OD, is the latest innovation in LED technology, popularly called as virtual pixel or 'V-tech' technology. The virtual pixel is a multiplexed pixel that allows a tighter screen resolution by using pixel-sharing techniques.
In traditional LED screens, a large number of LEDs will remain dormant while they wait for their particular color to come up in the image that is being viewed. Using V-tech technology, each LED is a pixel, borrowing from its neighbor the color it needs to create a full pixel increasing the resolution and enhancing the picture quality.
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