LEDs and LED Accessories

What Is a LED?

LEDs are among the most breakthrough technologies of the 20th Century. They are capable of emitting a great deal of light with very little power consumption. They are stable devices and are able to endure shock and other hazards very well. They come in a range of colors, allowing them to be used for signaling, indicator lights, display lights and flashlights. They are even used in household light fixtures as more energy efficient and far more durable alternatives to incandescent light bulbs. Even compared to compact florescent bulbs, they have lifespans that are much more impressive than other options on the market. A LED can emit light for literally tens of thousands of hours, which is the equivalent of decades of usage as a household light.

LED lights come in many different forms today, though they were rather limited in their capabilities when they were first developed. Today, consumer-level devices that cost very little money make use of powerful LEDs for safety, for emitting light in the IR and UV range, as remote control devices and more. They have also played a role in how computer monitors and televisions have developed, enabling the creation of very high resolution screens that are much thinner and lighter than CRT screens could have ever been manufactured. In automobiles, LED headlights provide very good visibility for the driver and consume far less power—and last much longer—than old auto headlights, improving safety and sustainability.


What Does LED Stand For?

LED stands for Light Emitting Diode. These are semiconductor devices that are very similar to many of the other semiconductor devices found in computers and other appliances. The first visible light designs emitted only red light, but there are designs available today that emit most any color and intensity of light.


How Does a LED Work?

The function of a LED is based on its semiconductor properties. The diode permits electrons to flow in only one direction through the component,. As they do, they begin recombining with in holes in the semiconductor material. This movement releases energy, which escapes the diode as a photon, a quantum of light.

Using various designs, LEDs can be made to emit certain colors of light or to distribute that light across a wider or narrower area. The technology that goes into these devices has advanced considerably over the years, leading to these devices being used in a variety of different applications.


What Are the Various Parts Inside a LED?

Figure 1: (we are creating our own diagram which will be used instead of this) Source: http://electronics.howstuffworks.com/led.htm/printable

In the above diagram, the parts of a LED are visible. The transparent plastic case houses the entire semiconductor device. In some LEDs, this case is designed to provide a specific type of light distribution, or may be of a specific color.

The terminal pins on the device are attached to the circuit, providing the current that powers the device. The diode is located within the case and is made out of the actual semiconducting material. When the electrons recombine within the holes in the semiconducting material, they emit the beams of light as shown in the diagram above. Note that, in the diagram, the light beams are being bounced off the side and emitted from the top of the LED, a common configuration for these devices.


How Was the LED Discovered?

LEDs function on a principle called electroluminescence, which was first discovered at Marconi Labs in 1907. The first LED wouldn’t come until two decades later, however, when Oleg Losev, a Russian scientist, built the first device.

It would take until the 1960s until LEDs came into their own. Researchers at Texas Instruments discovered a way to emit infrared light through electroluminescence. This was built upon by further researchers, with the first commercial version of a LED being released in 1962.

Visible LEDs were originally red. They are considered to have been principally innovated by a man named Nick Holonyak Jr who worked for General Electric Company. He worked on brightening LEDs and on designs that allowed different colors than red to be emitted.


What Colors Do LEDs Produce?

The colors that LEDs produce depend upon what semiconductor materials are used in their construction. They can emit any color of the visible spectrum. They can also emit into the ultraviolet and infrared ranges. They can emit pink light by combining various other colors to achieve the effect. White light can be emitted, as well, which is now being used in LEDs designed to replace incandescent bulbs in the household.


What Types of LEDs Exist?

The first LEDs were very low-power affairs, but that has changed tremendously over the years. Today, there are several different types of LEDs.

Miniature LEDs are most often used as indicator lights. These are very small, going down to as little as 2mm in diameter. They come in a variety of different shapes, making them suitable for use in many different designs. They usually consume between 5V and 12V of power.

Medium power LEDs emit in the 10s of lumens range. They are increasingly being used in automobile lights, where they provide excellent visibility at very low power consumption levels compared to standard incandescent bulbs.

High power LEDs are LEDs that can function at very high currents, sometimes more than a full amp. They usually have a heat sink incorporated in their design to shut off wasted energy. They are used in household lights, in display signs and in other applications where a high level of lumens is required.

There are other types of LEDs on the market, including ones that are designed to flash, ones that combine more than one type of emitter and ones that are designed to emit non-visible light in the infrared and ultraviolent ranges of the spectrum.


What Are IR LEDs? How Do They Work and What Are They Used For?

Infrared LEDs emit light in the infrared range of the spectrum, which is not visible to the human eye. They were among the first LEDs manufactured. IR LEDs are used widely in remote control units, where they can emit a pulse of light visible to an IR sensor but not visible to the eye. They are also used in security systems, frequently seen mounted around the lens of security cameras, where they flood nighttime scenes with IR light that can be used to create an image in the camera. These are usually visible through a smartphone or other digital camera as white-lit LEDs, as those cameras see further into the IR range than the human eye.


What Are LED Light Pipes? How Do They Work and What Are They Used For?

A light pipe is actually exactly what the name implies. It allows light to be directed horizontally with minimal scatter. They are made out of glass and polycarbonate, in most cases, and they can be mounted on a PCB or a panel. They can also be used with various types of LEDs, including through-hole and surface-mounted types. There are even flexible designs available.

A light pipe allows a designer to direct the light from a LED to a location that is not in a straight line from the LED itself, something which would normally be impossible with light. This can be used to, for example, take the light from an indicator on a PCB and direct it toward a panel, eliminating the need to install a separate LED for the operator’s benefit.


What Are LED Testers? How Do They Work and what Are They Used For?

A LED light tester allows LEDs installed in multi-light systems to be tested individually. They sometimes have their own power source, allowing the lights to be tested without powering the entire system up.

The LED light tester can be used in any application where one faulty LED might be preventing the others in the system from lighting up. The most obvious and accessible example of how this may be employed is Christmas lights. The tester can be attached to each individual LED until the bad light that’s preventing the lights from functioning is discovered and can be replaced. There are specialty designs available for use in specific applications, such as testing signs and so forth.


What Are UV LEDs? How Do They Work and what Are They Used For?

UV LEDs emit light in the ultraviolet range of the spectrum, invisible to the human eye. They sometimes are visible, emitting blue and purple that is within the range of the human eye in addition to UV light.

UV LED technology has a wide range of uses. These LEDs can be used to emit UV light that can be used to inspect machinery and for other tasks. They can also be used to detect watermarks in currency, preventing counterfeiters from being able to pass off phony bills. They are used in medical technology, as well.

UV LEDs can also be used for decorative purposes, much like a standard black light. There is some concern that the blue and ultraviolet frequencies emitted by some LEDs could lead to increased light pollution in urban areas. Blue and UV LEDs were among the last developed but are very common today.

Some LEDs that emit far into the UV range, but also into the visible spectrum, are used for rather mundane purposes. Pet stain detecting lights, for instance, cause pet urine to glow when the light is shone on it, making it easier for people to clean. LEDs are so inexpensive that even these types of advanced technology are available for very affordable prices.


What Are Visible LEDs? How Do They Work and What Are They Used For?

Visible LEDs can produce any color of the spectrum. They can do so directly, without a filter or a lens, by combining certain materials in their construction. They can also produce colored light by combining different colored LEDs, using the familiar RGB method of creating all the colors of the spectrum.

Visible LEDs include the types of LEDs that are used as indicator lights. The colorful options allow the indicators to be color coded, in some cases, or to be used as ornamentation in others. High end computers, for instance, often have cases with LEDs that serve no practical purpose installed in them, but that do increase the aesthetic appeal of the computer.

LEDs are also used in various roles in automobiles, including those already mentioned. LEDs in automobiles sometimes include the dashboard lights, interior lights, running lights and other types.

Visible LEDs are increasingly being used in households and offices. LED light bulbs are common, but new types of LED light, such as those designed to replace fluorescent tubes, sometimes using very similar fixtures, are available. These provide as much light as the lights that they’re replacing and consume very little energy relative to the lumens that they produce. As colored LEDs have become more advanced, manufacturers have been able to improve the quality of light that comes from them. For instance, LED light bulbs once had a very harsh, white light that people did not seem to gravitate toward, but come in designs now that throw off a warm, natural light that’s more aesthetically appealing to most.

Visible LED lights are also excellent for handheld lighting applications. The LEDs consume very little power, extending the battery life of the light. They are also very sturdy, making them ideal for applications such as bike lights, which may take a lot of shock and occasionally be dropped.

Visible LED lights are also used in computer screens, providing the backlight that illuminates the image.

Visible LEDs are found in most lighting applications today. In some areas, they haven’t worked their way into the market to a significant degree, but in others, they’ve largely replaced other technologies. LED flashlights, for instance, are available in hardware stores, sporting goods stores, grocery stores and online and are very affordable.

One property of visible LEDs that makes them even more flexible is that their color can be changed with optics such as lenses, but can also be changed by using different materials in their construction.