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750px-Verschiedene LEDs

LEDs are produced in a variety of shapes and sizes.

About[]

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting. Introduced as a practical electronic component in 1962, early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet and infrared wavelengths, with very high brightness.

When a light-emitting diode is forward biased (switched on), electrons are able to recombine with electron holes within the device, releasing energy in the form of photons (light). This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor. An LED is often small in area (less than 1 mm2), and integrated optical components may be used to shape its radiation pattern. LEDs present many advantages over incandescent light sources including:

  • lower energy consumption
  • longer lifetime
  • improved robustness
  • smaller size
  • faster switching
  • greater durability and reliability.

LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compact fluorescent lamp sources of comparable output.

Light-emitting diodes are used in applications as diverse as replacements for aviation lighting, automotive lighting (particularly brake lamps, turn signals and indicators) as well as in traffic signals. The compact size, the possibility of narrow bandwidth, switching speed, and extreme reliability of LEDs has allowed new text and video displays and sensors to be developed, while their high switching rates are also useful in advanced communications technology. Infrared LEDs are also used in the remote control units of many commercial products including televisions, DVD players, and other domestic appliances.[1]

Power sources[]

The current/voltage characteristic of an LED is similar to other diodes, in that the current is dependent exponentially on the voltage (see Shockley diode equation). This means that a small change in voltage can cause a large change in current. If the maximum voltage rating is exceeded by a small amount, the current rating may be exceeded by a large amount, potentially damaging or destroying the LED. Typically, an LED operates between 1.5 to 5 VDC with a resistor in series to prevent early component destruction. Also, an LED has one leg longer then the other one, the longer one is the positive lead and the smaller one is the negative.


References[]

  1. E. J. Mastascusa . "LED." Bucknell University . 2008. http://www.facstaff.bucknell.edu/mastascu/eLessonsHTML/Diodes/Diode3.html


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Video[]

thumb|300px|right|Make presents: The LED

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