Curso de led´s

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  • Publicado : 7 de octubre de 2010
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This course is organized like a book with multiple chapters. Each chapter may have one or more pages.

1. The previous and next arrows move you forward and back through the course page by page.
1. The left navigation bar takes you to any chapter. It also contains the bookmarking buttons, 'save' and 'go to.' To save your place in a course, press the 'save' button. The nexttime you open the course, clicking on 'go to' will take you to the page you saved or bookmarked.
1. The 'Go to Final Test' button on the left navigation bar takes you back to the Analog University course listing, where you started. Take the course final test by clicking on 'Test Yourself.'
1. The top services bar contains additional information such as glossary of terms, who to go to forhelp with this subject and an FAQ. Clicking home on this bar will take you back to the course beginning.

1. Don't miss the hints, references, exercises and quizzes which appear at the bottom of some pages

Overview of lighting
This chapter will provide overview of lighting applications and measurement of light.
1. 2.1 LED Applications
2. 2.2 More Applications
3. 2.3 EL &CCFL
4. 2.4 Color of light
5. 2.5 How bright?
6. 2.6 Overview Test

LED Applications |
Increasing number of portable devices use LCD displays that are backlit for brightness. White or RGB LEDs are used for this backlighting. Such LEDs are also used for intense lighting like camera flash or reading lights and for visual multicolor fun indication of status such as incoming calls on acellular handset.
1. From smallest 2" MP3 player displays using 5 LEDs to bigger 6"-9" Automotive displays using 10-16 LEDs, LEDs for backlighting are found in many applications.

1. Table below shows a matrix of display size vs number of backlight LEDs typically seen. As the size grows, there is also a trend towards using RGB LEDs instead of white LEDs.

More Applications |
In additionto the portable backlighting applications, LEDs are also seen in other backlighting applications.
1. LEDs are also seen in backlighting white goods, variable message signs e.g. in public transport and backlighting flat panel TV and PC monitors.

1. Brighter LEDs (called HVBLED - high voltage bright LED) are being used in illumination applications replacing classical lightingtechnologies. Examples are Automotive turn indicators (inside, front, rear and on mirror), architectural lighting, exit signs and traffic signs.


Besides LED, there are two other backlighting technologies - EL and CCFL.
1. EL (Electroluminescent Lamp) backlighting is commonly used for low brightness monochrome display backlight (e.g. watches, secondary handset display),cellular handset keypad backlight, automotive dash, auto PRNDL sign.
1. Advantages
1. Very thin and uniform light source
1. Can be cut and shaped
1. Common colors -blue-green, white, amber and blue
1. Relative low cost
1. Cool to the touch
1. Disadvantages
1. Poor performance in high humidity
1. Needs DC-ACinverter (120VAC @400Hz)
1. Relative low brightness (~ nits)
1. Relative short life span (3000~5000hrs to ½ bright)
1. CCFL (Cold Cathode Fluorescent Lamp) is commonly used in graphics and color displays (laptops), gas pumps, medical instruments, industrial PCs, POS, etc.
1. Advantages
1. Uniform and bright white light.
1. Disadvantages
1. Needsa DC-AC Inverter
1. 1000VAC @ 30kHz~40kHz
1. Typical life about 20~25000 Hrs.
1. CCFL more expensive than LED and EL
1. Uses material considered environmentally unfriendly
It's True!Both EL and CCFL have been used for backlighting since early 1990s, LED backlighting is more recent - early 2000s. |

Color of light |
The definitions on...
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