Light-emitting diode, or more commonly known as LED is a two-lead semiconductor light source. It has a p-n junction diode that when activated, it emits light.
Not like lasers, the color of the light emitted from a LED is neither coherent nor monochromatic. However, it has a narrow spectrum with respect to the human vision, and for most purposes, the light from a simple diode element can be regarded as a functional monochromatic.
In 1962, LEDs has appeared as a practical electronic component. The earliest LEDs emit a low-intensity infrared light. The infrared lights are frequently used, up today in transmitting elements in remote-control circuits. The first visible light of LED is of low intensity and limited to red, however, the LEDs of today are available in visible, ultraviolet, and infrared wavelengths, with very high brightness.
LEDs have numerous of advantages over incandescent light sources, such as low energy consumption, long life cycle, improved physical robustness, smaller size, and faster switching. They are significantly more energy efficient and have fewer concerns regarding their disposal.
LEDs, when operated at low currents and at low temperatures, can be subjected to wear and tear, even though it is a solid-state device. The usual life cycle of a LED is up to 25,000 to 100,000 hours, however, it can extend or shorten. The most common sign of LED failure is the gradual lowering of light output and loss of efficiency, although sudden failures can also happen.
Conventional LEDs are available in different colors, such as infrared, red, orange, yellow, green, blue, ultraviolet, pink, purple, and white. These are made from a variety of inorganic semiconductor materials, with different wavelength, voltage drop, and materials.
There are considerations in using LEDs, it has the same current-voltage characteristic to other diodes. A small change in the voltage can cause a large change in the current, thus a constant current power supply should be used to avoid damaging or destroying the LED. Just like diodes, the current flows easily from p-type to the n-type material, when a reverse voltage grows large enough to exceed the breakdown of voltage, a large current flow may occur leading to the damaging of LED.
The materials used to make LEDs are safe under all conditions of normal use. It does not contain mercury, the federal standards declared that LEDs are not hazardous except those low-intensity red LEDs and low-intensity yellow LEDs.
There are numerous of advantages in using LEDs, it emits more lumens per watt than an incandescent light bulb, and can emit an intended color without the use of any filter. It has a cool light that radiates a small amount of heat, and difficult to damage with external shocks, unlike other bulbs that are fragile. It has a long life cycle, and it fails by dimming over time and not an abrupt failure.
However, there are also disadvantages in using LEDs, it is more expensive on an initial capital cost basis, and it largely depends on the ambient temperature of the environment.