555 Timer LED Flasher - What is LED ?


  • Light-emitting diode (LED) is a PN junction semiconductor device that emits a monochromatic (single color) light when operated in a forward biased direction.
  • Light is produced within the solid semiconductor material.
  • Light is generated when the particles that carry the current (known as electrons and holes) combine together within the semiconductor material.
  • It is also defined as solid-state devices.
  • LED convert electrical energy into light energy
  • LEDs present many advantages over traditional light sources including
    • Lower energy consumption.
    • Longer lifetime.
    • Improved Robustness.
    • Smaller Size.
    • Faster Switching.


Types of Light Emitting Diode

  • Gallium Arsenide (GaAs) – infra-red
  • Gallium Arsenide Phosphide (GaAsP) – red to infra-red, orange
  • Aluminium Gallium Arsenide Phosphide (AlGaAsP) – high-brightness red, orange-red, orange, and yellow
  • Gallium Phosphide (GaP) – red, yellow and green
  • Aluminium Gallium Phosphide (AlGaP) – green
  • Gallium Nitride (GaN) – green, emerald green
  • Gallium Indium Nitride (GaInN) – near ultraviolet, bluish-green and blue
  • Silicon Carbide (SiC) – blue as a substrate
  • Zinc Selenide (ZnSe) – blue
  • Aluminium Gallium Nitride (AlGaN) – ultraviolet

Types of LED

How it Works


How LED Works

  • When current flows across a diode.
  • Negative electrons move one way and positive holes move the other way.
  • The holes exist at a lower energy level than the free electrons.
  • Therefore when a free electrons falls it losses energy.
  • This energy is emitted in a form of a photon, which causes light.
  • The color of the light is determined by the fall of the electron and hence energy level of the photon.

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