In 1961 two researchers, Robert Biard and Gary Pittman discovered that a certain compound was capable of emitting infrared radiation when passed through an electric current. This compound is GAAS (Gallium Arsenide), this compound is used in the manufacture of rectifier diodes and others. However, ultraviolet radiation cannot be seen with the naked eye, so in 1962, Nick Holonyak was able to obtain, through an LED, visible illumination, in red color. Robert and Gary patented the idea, but Nick Holonyak is considered the inventor of LED (Light Emitting Diode).
The LED is a light-emitting diode, however, there are other types of diodes. The Diode is an electronic component, made of germanium or silicon, which conducts electrical current only in one polarization (positive anode and negative cathode), this polarization is called rectification, is used to convert alternating current (AC) into direct current (DC ) and extract information from an amplitude-modulated (AM) signal. There are also other types of diodes for certain functions.
Main types of Diodes:
- Rectifiers: rectifier diodes are the most common, have direct polarization (positive anode, negative cathode), are used to convert alternating current into direct current;
- Zener diode: generally used in voltage regulating circuits and power supplies, the peculiarity of this type of diode is its polarization. Unlike the aforementioned, this diode has reverse polarization, that is, negative anode and positive cathode;
- Tunnel: devices used in high frequency (microwaves), through quantum mechanics phenomena. They are used in amplifier circuits, oscillators and frequency converters;
- LED: are diodes that, when passed through an electric current, are capable of emitting light;
The word LED comes from the English Light Emitting Diode, which means Light Emitting Diode. LED is a semiconductor electronic component, composed of silicon or germanium semiconductor crystal. LED has the same technology used in computer chips, which have the ability to turn energy into light. The transformation of electrical energy into light that LEDs have is different from the transformation that incandescent lamps do. Conventional incandescent lamps use a metallic filament, whereas in LEDs this transformation is made in the matter, being called a solid-state. In incandescent lamps, the metal filament is placed inside, the same filament heats up when electrical current flows. Atoms have their degree of agitation so increased that the emission of light occurs. The LED emits light when the electric current travels through the PN (semiconductor diode) junction material, emitting infrared radiation. The most important component of an LED is the semiconductor chip, responsible for the generation of light, this chip has very small dimensions, smaller than the size of a conventional LED, about 0.5 mm.
The LED is a bipolar component, it has two terminals called anode and cathode, which determine whether or not the polarization of the LED, that is, the way it is polarized determines the passage or not of electric current, this causing the occurrence of light . The polarization that allows the emission of light by the LED is the anode terminal on the positive and the cathode on the negative, to identify which of the terminals is the anode and which is the cathode, just observe the size of the terminals. The largest “leg” of the LED is the anode, and the smallest is the cathode.
Using the LED
The LED is generally used in electronics, where its application for signaling (on or off), for example, is advantageous. It is very easy to find LEDs on various household appliances, such as LED TVs, also on radios, computers, some types of traffic lights, etc. However, as a result of energy crises and the concern with the proper use of electric energy and its economy, LED has also been taking up space in the lighting of homes, with LED lamps.
LED lamps to have several promising and innovative features with regard to residential lighting, in addition to being less aggressive to the environment, like other lamps. As previously mentioned, the lamps use a metallic filament in the transformation of electrical energy into light, which causes heating and poor lamp durability, compared to LED. LED lamps are the future of residential lighting as they are economical and have a long service life.
Types of LEDs
There are variations of LED models, some of them are:
- Common diffuse LEDs: the light from these LEDs is scattered through its plastic shell. The goal would be for the light to be uniform throughout the LED surface, but there are still points with greater brightness and less brightness;
- High brightness LEDs: the luminous power of these LEDs is much greater than that of diffuse LEDs, for example. The plastic capsule is transparent, which increases the brightness of the LED, its light is concentrated;
- LED strips: as the name suggests, it is a strip that has, in its extension, several tiny LEDs, shining together or alternating, depending on the model of the tape;
- Bi-color LEDs: can be diffuse or transparent, have two colors, or the combination of two colors to form a third color. It can display two or three terminals;
- RGB or tricolor LEDs: they have three colors, red (Red), green (Green) and blue (Blue). They can be diffuse or transparent. The use of colors can be joint or individual;
- SMD LEDs: are the LEDs used in the LED strips, they can be diffuse, transparent or tricolor;
- Matrix of LEDs: are sets of LEDs used in rows or columns, to present readings and even graphics of bay resolution. They can be diffuse, tricolor or transparent, they can work together or individually depending on the model;
The size of the LEDs can generally vary from 3 to 10 millimeters, other sizes, smaller or larger, are usually for specific cases. The amount of LED illumination is always measured in lumens, and its lifespan is dependent on the location and manner of use, but varies from 25,000 to 100,000 hours.