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Hockey’s Jadoogar – Dhyan Chand

Dhyan Chand popularly known as hockey's jadoogar. Dhyan Chand was born on 29th August, 1905 at Allahabad. His father was in the British Indian...
HomeLearnScienceHow Light Emitting Diodes Work?

How Light Emitting Diodes Work?

Light Emitting Diodes, commonly called LEDs, are real unsung heroes in the electronics world. They do dozens of
different jobs and are found in all kinds of devices. Among other things, they form numbers on digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light.
Basically, Light Emitting Diodes are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don’t have a filament that will burn out, and they don’t get especially hot. They are illuminated solely by the movement of electrons in a semiconductor  material, and they last just as long as a standard transistor. The lifespan of an LED surpasses the short life of an incandescent bulb by thousands of hours. Tiny Light Emitting Diodes are already replacing the tubes that light up LCD HDTVs to make dramatically thinner televisions.
 Light Emitting Diodes are specifically designed so they make light of a certain wavelength and they’re built into rounded plastic bulbs to make this light brighter and more concentrated. Red LEDs produce light with a wavelength of about 630–660 nanometers—which happens to look red when we see it, while blue Light Emitting Diodes produce light with shorter wavelengths of about 430–500 nanometers, which we see as blue.
We can also get Light Emitting Diodes that make invisible infrared light, which is useful in things like “magic eye” beams that trigger photoelectric cells in things like optical smoke detectors and intruder alarms.  Semiconductor
lasers work in a similar way to Light Emitting Diodes but make purer and more precise beams of light.
Nick Holonyak: he came up with the idea of the light-emitting diode in 1962 while he was working for the General Electric Company.

What’s so good about Light Emitting Diodes?

In a nutshell:
  • They’re tiny and relatively inexpensive.
  • They’re easy to control electronically.
  • They last virtually forever. That makes them brilliant for traffic signals.
  • They make light electronically without getting hot and that means they save lots of energy.
  • Energy efficient source of light for short distances and small areas.
  • The typical LED requires only 30-60 milliwatts to operate
  • Durable and shockproof unlike glass bulb lamp types
  • Directional nature is useful for some applications like reducing stray light pollution on streetlights

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  • May be unreliable in outside applications with great variations in summer/winter temperatures, more work is being done now to solve this problem
  • Semiconductors are sensitive to being damaged by heat, so large heat sinks must be employed to keep powerful arrays cool, sometimes a fan is required. This adds to cost and a fan greatly reduces the energy efficient advantage of LEDs, it is also prone to failure which leads to unit failure
  • Circuit board solder and thin copper connections crack when flexed and cause sections of arrays to go out
  • Rare earth metals used in LEDs are subject to price control monopolies by certain nations
  • Reduced lumen output over time.

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