LED (light emitting diode) lighting systems are increasingly being used for lighting purposes. LED lighting systems are mostly used to replace the energy consuming traditional lighting systems like fluorescence bulbs and incandescence bulbs. LED lighting systems will find the most frequent applications in the future compared to the traditional lighting systems (ERCO 8).
The use of LEDs has a short history. Electroluminescence was discovered in the year 1907 by HJ round using silicon carbide crystals. The first LED was created in 1927 by Losev Oleg. Infrared emission of gallium arsenide was reported in the year 1955 by Rubin Braunstein (Shuji 245). During the year 1961, Robert Biard and Pittman Gary obtained the first patent for infrared LEDs. During the year 1962, Nick Holonyak developed the first visible spectrum LED. In 1976, the first highly efficient highly bright LEDs for optical fiber telecommunications were developed by TP Pearsall (Hecht 132).
The first LEDs were very costly and had little use. However, advances in technology resulted in the use of planar processing, innovative packaging, and chip fabrication to obtain the required cost reductions in LEDs production (HS lighting). The first major practical use of LEDs was the replacement of the neon indicators and incandescence lights used in electrical appliances like radios and TVs. The first LEDs were only bright enough for the use in electrical appliances as indicators (Tom and Wesley 1).
Multicolored LEDs were later developed and utilized in many electrical appliances. As LEDs technology became advanced, the development of the white light LEDs opened the use of LEDs in illumination. LEDs lighting is fast replacing fluorescent and incandescent lighting systems (Hecht 345). Rapid development in high brightness LEDs has also transformed LEDs lighting systems. LEDs technology developments have led to an increase in the efficiency and the light output of LEDs exponentially since the invention of the first LEDs in 1960. For example, luminous efficiency of 300 Lumens of visible light has become a reality using neon crystals (Cantalupi 1).
Light emitting diodes exploit semiconductors. These semiconductors can transmit an electric current. LEDs are solid state lights. They do not require cruets containing gas mixtures or other components (ERCO 16). LEDs have many advantages over other lighting systems. LEDs have a longer lifetime; they need little or no maintenance and produce a higher lighting efficiency (Fred 334).
LEDs also consume less electricity and have better capabilities for manipulation to achieve different light color schemes. LEDs also have a unique mechanical reliability because of their solid state structure. LEDs are also small in size compared to other lighting systems. LEDs’ sizes range from micro LEDs that utilize milliwatts of electricity to large power LEDs that consume hundreds of watts of electricity (Cantalupi 1). Low and medium power LEDs do not exceed 150MA and are used to obtain light signals for decorative purposes. Power LEDs are used in lighting surfaces and large environments (Tom and Wesley 1).
LEDs are typically illuminated by the movement of electrons in the semiconductor material. The main conductor used in LEDs is Aluminum Gallium Arsenide (AlGaAS). The semi conductors having extra electrons are called the N type material since they have negatively charged particles (Held 40). The semiconductors with extra holes are called the P type material, because they have positively charged particles (Shuji 255). A diode comprises of an N type semiconductor and a P type semiconductor with electrodes on each end. This arrangement makes diodes conduct electricity in only one direction (Hecht 411).
When no voltage is applied in the diode, electrons from the N semiconductor fill holes from the P semiconductor along the PN ends making a junction between the N and P materials. This junction or layer forms a depletion zone that makes the diode tube be in an insulating state because all the holes are closed and there are no free electrons moving freely in the diode (Tom and Wesley 2).
The depletion zone is removed by applying current that makes the electrons move from the N type area of the P type semiconductor (Held 59). The N type semiconductor is connected to the negative side of a circuit while the P type part of the LED is connected to the positive end. When the electrons in the holes in the depletion zone are boosted out, they move across the diode in the process making the depletion zone disappear (Cantalupi 1).
The interaction between the electrons and the holes in the diode generate light. The wavelength of the photons of light emitted by the LEDs is determined by the band gap energy of the P/N junction (Cantalupi 1). In diodes made of silicon and germanium diodes, the holes and the electrons combine in a transition that is not irradiative. There is no optical emission in silicon and emission diodes because these materials are from indirect band gaps (ERCO 23).
The materials mostly used in LEDs have a direct band gap with varied bandwidth including visible, near infrared, and near ultraviolet light. Many commercial LEDs use sapphire substrates. Many LEDs semiconductors have transitional coatings of clear or colored molded plastic shells. These plastic shells make the process of installing semiconductor chips in devices very easy to accomplish (Cantalupi 2).
The plastic shells transitional coatings in LEDs also prevent the electrical wiring from damage. These plastic shells also act as reflective intermediaries between the semiconductor and air. These plastic shells act as the diffusion lens that allow light to be emitted at higher angles of incidence (Hs lighting 2).
LEDs are specifically constructed to release outwards a large number of photons outwards. LEDs are housed in a plastic bulb that concentrates the light in one direction. Most of the light from the light emitting diode bounces on the sides of the bulb travelling through the corners of the bulb. Many LEDs are designed to operate with not more than 30-60 milliwatt of power. However, powers LEDs capable of using more than one watt have been developed (Tom and Wesley 4)
Light emitting diodes (LEDs) have some unique engineering features that open the avenue for their utilization in planning and the design of decorative lighting. The lumen of LEDs indicates the light flux, which is the quantity of light given out by a light source per second. LEDs have been developed that give out many Lumens per watt of electricity consumed (Shuji 256).
The use of LEDs in lighting systems requires a very high flux. The flux is the illumination, i.e. the light quantity that falls on a surface unit. The light flux is determined by the quantity of light source and the distance of the light emitting source with the illuminated area (Cantalupi 1). It is possible to manipulate the Lumens, the colors, and the flux of the light emitted by LEDs to achieve unique lighting décor (Fred 336).
It is also possible to program LEDs to dim in a unique pattern to provide a unique lighting system. LEDs technology is utilized in providing the greatest lighting densities on small spaces. This great density lighting systems form the basis of selling points for many products in the market. The direct contacting of the LEDs in display devices allows for optimal lighting conditions that are visually appealing (Cantalupi 2).
To produce a unique lighting system using LEDs, the designer must first determine the lighting intensities required in a given space, and then determine the output of the light of various devices. The designer must then consider the factors that degrade light output. The LEDs lighting devices must then be selected in layouts that produce the desired light distribution patterns (Hecht 456). For example, the Metropolitan Museum of art galleries in San Francisco utilizes LEDs lighting in displaying the artifacts in the museum.
The MetropolitanMuseum holds a large collection of decorative arts and French furniture housed in extravagant 18th century rooms. The grand rooms of the museum have been dramatically transformed from just lifeless museum displays to atmospheric environments because of the unique LEDs lighting system. The museum was originally illuminated using floodlights which consumed a lot of power, and the lighting was too harsh on the artifacts (Arts management network 3).
The replacement of the floodlights with energy efficient LEDs lights mounted on the façade of the mecum has made the museum a spectacular masterpiece of art. The LED lights are angled on the sidewalks and are programmed to dim in some conditions to enhance the architectural appeal of the museum. The environment and the character of every room in the museum are different. The balance of lighting, the hierarchy, the shadow, the color, the sparkle and temperature is all woven into the LED lighting system (Arts management network 2).
The objects on display reveal their glory because of their unique lighting system that is enhanced for low light limits. The candlesticks are also equipped with electric flames that move adds to the décor to the museum. The accent lighting of the objects in the museum utilizes a low voltage lighting system in the ceilings of the building and fiber optic sub miniature spotlights that are hidden in the room entrances. LED lighting systems are also used to simulate daylight and night conditions in the museum (Arts management network 3).
All the light sources in the museum are dimmed to allow for the balancing of the intensity of the multiple light sources and extension of the life of the electroluminescence lights used in the museum. The unique architectural LED lighting systems of the museum have won an excellence award from the international association of lighting designers. The designers of the lighting system utilized LED lighting system to achieve a unique decor for the metropolitan museum (Arts management network 2).