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3.2.6 LEDs

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From Robotics

Definition: Light Emitting Diodes (LEDs) are compound semiconductor devices that convert electricity to light when biased in the forward direction. Because of its small size, ruggedness, fast switching, low power, and compatibility with integrated circuitry, LED was developed for many indicator-type applications.

Today, advanced high-brightness LEDs are the next generation of lighting technology and are currently being installed in a variety of lighting applications. As a result of breakthroughs in material efficiencies and optoelectronic packaging design, LEDs are no longer used in just indicator lamps. They are used as a light source for illumination for monochromatic applications such as traffic signals, brake lights, and commercial signage.

LED Benefits

  • Energy efficient
  • Compact size
  • Low wattage
  • Low heat
  • Long life
  • Extremely robust
  • Compatible with integrated circuits

FIGURE 3.20 Parts of an LED

FIGURE 3.20 Parts of an LED.


LED Structure
  • Chip
  • Lead frame
  • Gold wire
  • Epoxy resin (plastic mold package)
  • Cathode
  • Anode
  TABLE 3.3   Semiconductors for LEDs
General
GaP
GaN
GaAs
GaAlAs
Green, Red
Blue
Red, Infrared
Red, Infrared

Super
GaAIAs
InAsP
GaN
InGaNGaP
Red
Yellow, Red
Blue
Green Green

Ultra
GaAIAs
InGaAlP
GaN
InGaN
Red
Yellow, Orange,
Red
Blue
Green

Classification: Classification of LEDs are defined by spectrum.
(i) Visible LED: Based on max. spectrum, produces red, orange, yellow, green, blue, and white.
(ii) Infrared LED: (IR LED).

Applications of LEDs
Visible LED: General-purpose application in various industries including indication devices for electronic appliances, measuring instruments, etc.
Bi-color (dual color) LED: Charger for cellular phones, showcase boards, traffic boards on highways, etc.
High & Ultra Brightness LED: Full-color display for indoor/outdoor, automotive signal lamps, high-mount lamps, indoor lamps, traffic signal lamps, etc.
Infrared LED: With high output capacity, IR LED is used in remote controls, IrDa ( Infrared Data Storage Devices), etc.

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