A light emitting diode or LED is very simply a light source or a diode that puts out light. LEDs are often used in electronic devices as indicator lights; they are ideal for showing whether a circuit is closed.
A diode is an electronic device that conducts electricity in one direction. An LED includes a diode semiconductor chip, an epoxy casing, and two wires or leads that extend out of the casing. One of the leads is positive and the other is negative. The negative lead βor anode lead β is always the shorter of the two wires and is connected to the negative pole of a battery. The positive lead β or cathode lead β of the LED is connected to the positive pole of a battery.
When the leads are both connected to a battery, a circuit is created. When the circuit is created, electrons move easily through the LED in one direction, passing from the negatively charged portion of the chip to the positively charged section. Once this movement takes place, there is a charge and electromagnetic energy is created. This burst of electromagnetic energy emits a photon of light and causes the device to glow or emit light.
LEDs are extremely low voltage devices; an LED generally operates between 1 and 4 volts. LEDs are available in different colors; since materials all emit photons in only a narrow range, different materials must be used in the semiconductors inside LEDs in order to produce different colors of light. Because each LED emits visible light in only a narrow wavelength, the color displayed by an LED is monochromatic.
So, a light emitting diode displays a true color with no other waves disrupting the display. This also allows LED light to be seen from great distances. Some of the most commonly used LED colors are red, green, blue, white and amber. Red and green both protect night vision effectively; blue is the gentlest LED color for the eyes to view. White LED light is the most commonly used for general applications.
Many light sources such as halogen and incandescent bulbs create light by heating filaments until they radiate light. These sources are wasteful since a large amount of energy is lost in the radiation process. LEDs do not waste energy, because they convert electrical current directly into the light without an extra process such as radiation. So, while LEDs are extremely low voltage, they are also extremely efficient.
Light emitting diodes are flexible and efficient devices; engineers appreciate the ease of control and programming in incorporating LEDs into a wide array of devices. LEDs emit no ultra-violet rays, are very bright and intense, produce little heat and are highly reliable. They are not only resistant to motion and shock, but are long lasting so they need to be replaced only rarely.
LED technology continues to expand allowing a wider range of colors and ever-increasing brightness. Today, light-emitting diodes are used in appliances, electronics, cell phones, clocks and watches, streetlights and uncountable other applications. LEDs are likely to increase in popularity and usage as their advantages over other lighting sources continue to grow.