A light emitting diode (LED) is essentially a PN junction semiconductor diode that emits a monochromatic (single color) light when operated in a forward biased direction. The basic structure of an LED consists of the die or light emitting semiconductor material, a lead frame where the die is actually placed, and the encapsulation epoxy which surrounds and protects the die (Figure below shows both standard lamp type and surface mount type).
An LED can be operated using either one of the two following methods: 1.) “Static drive” where a constant DC current is supplied through a dropping resistor and 2.) “Dynamically” where the current is pulsed. Pulsing the LED is frequently used to conserve power since the LED in not constantly on. If the ON-OFF intervals are short, dynamic lighting appears to the human eye as static lighting.
The scientific measurement and quantification of LED color is called Colorimetry. Its units are typically given as chromaticity coordinates or in wavelength. Color perception is very complicated because it not only depends on the various physical properties of light such as the emission and optical properties of the light source, the wavelengths transmitted, etc. but also on things such as surrounding objects, the devices mechanical properties, the viewer’s eye response as well as their psychological state. The CIE (Commission International de l’Eclairage) has established standards for the measurement of visible light as it relates to the “standard human eye response.” This so called standard observer curve was first established in 1931 (see figure 1a).
ESD, or Electro Static Discharge, is the term used to describe the sensitivity of electronic components to static electrical charges. Many of these components such as some types of LEDs, computer chips, circuit boards etc. can be damaged beyond repair by an electrical discharge as low as 20 volts.
When the LED first became commercially available, over 30 years ago, no one really paid much attention to how it was made or what it consisted of chemically. This was in part due to the fact that only a few basic types and colors were available (such as GaP – red and green, and GaAsP – yellow). Today, in order to obtain new colors, or wavelengths, and improve performance and reliability, there are many new types of chemical structures being created.
If there were ever any question that LEDs would be such a dominating lighting technology just take a look around. They are virtually everywhere. From standard indicators on stereo equipment, laptops and toys to traffic lights, variable message signs and automotive lighting, LEDs have enjoyed an explosive growth over the last several years with no [...]
It’s been over 30 years since the introduction of the first LED (Light Emitting Diode) and we at long last have a white LED that begins to rival incandescent in many architectural and small area illumination applications.
LEDs have enjoyed a tremendous growth over the last several years with new applications ranging from automotive lighting and [...]
Communication is the cornerstone of success, and there’s no better way to communicate than a beautiful, state-of-the-art electronic message center in front of your school or an indoor LED display inside your school building. Now you too can afford to install one at your school.
A light-emitting diode (LED) is a semiconductor device that emits visible light when an electric current passes through it. The light is not particularly bright, but in most LEDs it is monochromatic, occurring at a single wavelength. The output from an LED can range from red (at a wavelength of approximately 700 nanometers) to blue-violet (about 400 nanometers). Some LEDs emit infrared (IR) energy (830 nanometers or longer); such a device is known as an infrared-emitting diode (IRED).
Myth: You save on energy bills by leaving lights on. Some people believe that the energy to turn on lights exceeds savings of turning lights off.