What Is An LED?
An LED, also known as a Light Emitting Diode, is a special diode that uses a semiconductor chip to produce light when an electric current passes through it. The light may be infrared, ultraviolet or visible, depending on the composition and condition of the semiconducting material used. LEDs are used is a multitude of applications, everything from remote controls and stop lights to water sterilization and interior lighting!
How Does An LED Operate?
As with other diodes, an LED requires correct polarity to properly operate, and therefore it must be wired accurately. Below the "bulb" of the LED are two wires, and it's quite easy to determine which side is positive and which side is negative. The negative side is always the shorter of the two wires, and also has a flat edge on the bulb of the LED when viewed from the top down. If you look inside the bulb of the LED, you will also notice that the negative side is larger than the positive side.
The semiconductor chip located inside the bulb has two regions ("p" positive, and "n" negative) which are separated by a junction. The junction acts as a barrier to the flow of electrons between the two regions. However, when properly wired and the correct voltage is supplied, electrical current flows from the positive (anode) side to the negative (cathode) side. This results in a flow of electrons from the "n" to "p" region. The movement of electrons releases photons, which we view as light!
What Are Some Benefits Of Using LEDs?
- LEDs use substantially less power than incandescent bulbs to produce light, which is especially useful in battery-powered devices.
In fact, LED lights are so efficient that 3 or 4 LEDs together can pull as little as .02 amps!
- The life span of LED lights far surpasses standard incandescent lights.
This longer life span results in a lower cost of operation for the user, as the LEDs will not require replacement as often as incandescent bulbs.
- LED lights can have a very narrow viewing angle, and can be aligned and focused to light small areas.
They are also available with a wide viewing angle, which increases the spread of light.
- Incandescent bulbs require an external reflector to collect and focus light.
Unlike regular incandescent bulbs, LED lights do not emit a sizeable amount of heat.
- LEDs emit light in specific colors, without the use of colored filters that incandescent lighting would require.
Is the Future of Lighting Moving Towards LEDs?
The short answer - YES! Incandescent bulbs have been around for more than 120 years, and you might be surprised to learn that the basic design hasn't changed much since the late 1870's. Incandescent light bulbs consist of a glass enclosure filled with an inert gas, such as argon. Inside the bulb is a thin filament of tungsten through which an electrical current is passed. The current heats the filament, and produces the visible light that we can see. Incandescent bulbs require relatively large amounts of power to produce light. Because of this inefficiency, there are currently government laws and regulations designed to phase out their household usage.
Where have LEDs been used in the lighting industry?
LEDs are commonly used in aesthetic, effect, or specialty lighting applications, including architectural highlighting. Most traffic lights and exit signs, for example, now use red, green or blue LEDs.
Light emitting diodes (LEDs) are solid-state lighting components. They have no moving, fragile parts and can last for decades. LEDs can be many times more energy efficient than light bulbs, depending on the application. Just as vacuum tubes in televisions were replaced with solid-state components, the last remaining vacuum tube light bulbs are being replaced by solid-state components.
Imagine a grain of sand that emits a very bright light, usually red, amber, green or blue, depending on the material, when an electrical current is applied. That's essentially an LED. The actual science and manufacturing process to develop an LED is quite complex, but the principle is simple.
The first LEDs for commercial applications were red. They functioned as on/off or indicator lights in electronic devices such as VCRs, calculators, stereo systems and even automobile subsystems. Eventually, LEDs were produced in green and amber as well. The major breakthrough came in 1989 when Cree, Inc. of Durham, NC, started shipping the first commercially viable blue LED, based on silicon carbide. That blue LED enabled white LED-based light. Mixing red, blue and green light produces white light.
Today, a more-efficient and cost-effective white LED light is revolutionizing the lighting world. The white power LED, based on a blue LED chip coated with a phosphor, is bright and efficient enough to be used in general illumination. Fixture manufacturers are making LED-based products for outdoor street, walkway, parking and indoor-down light applications.
Cree, a company whose founders included several N.C. State University graduate students, introduced the first lighting-class white power LED in 2006 and followed up with the first lighting-class warm (softer) white power LED in early 2007. LEDs are ready for general-illumination applications, presenting a dramatically enhanced lighting option to save energy and maintenance costs as well eliminate the hazardous-waste issues associated with mercury-containing light bulbs and tubes.
History of Light (& Heat)
The history of man-made light is based on heat. Wax, oil and gas burn to produce light. The filament in an incandescent bulb heats up to produce light. Gas in a fluorescent tube is zapped to illuminate. The basic method is "Heat it up, and it glows."
For more than 120 years, incandescent light bulbs have brightened and literally warmed our lives. Electric-powered bulbs were a major improvement over candle, gas and oil light sources, but they are extremely inefficient. Bulb-based light sources are far better at producing heat than light â€" up to 90 percent of the power going into a bulb is converted to heat.
Compact fluorescent bulbs (CFLs) are more efficient, and are an excellent alternative to incandescent bulbs for Edison-socket light fixtures. However, they contain a small amount of mercury, making them hazardous waste when they break or burn out.
In the past few years, a new light source has emerged that is sufficiently bright and efficient to be used for general illumination. The light emitting diode, commonly called the LED, uses far less energy and can last many times longer than most bulbs and contains no lead or mercury. Cree, Inc. introduced the first commercially available lighting-class LED in late 2006. Lighting manufacturers are now producing a whole new class of LED lighting products for general illumination.
LEDs are now ready for broad deployment across general lighting applications such as parking garages and lots, streetlights and other outdoor installations. Indoor directional and down light solutions are also becoming available. According to the University of California, Santa Barbara, widespread deployment of LED-based lighting could save $115 billion in electricity costs in the U.S. alone by 2025.
By committing to LEDs in campus lighting, universites are making a thoughtful energy choice that will greatly benefit their students, teachers, staff and the environment.
Want to learn more about how LEDs work? Try these resources:
According to the U.S. Department of Energy, in the next 20 years, rapid adoption of LED lighting in the U.S. can:
- Reduce electricity demands from lighting by one-third
- Eliminate 258 million metric tons of carbon emissions
- Avoid building 40 new power plants
- Create financial savings that could exceed