Tech Primer
LED (Light Emitting Diode) convert electrical energy into light. The wavelength of the light, i.e. the color of the light is determined by the semiconductor materials used and he light intensity is related to the current flowing through the LED.
LEDs are available in single color types such as red, green and orange, and multicolor types made up of two or three devices in a single package, each generating a different colors. Each color of LED can indicate status of a system. In instrumentation, green light generally refers to normal or safe; Yellow or amber to an abnormal status which may need monitoring or minor intervention and Red to an unsafe or failure state.
LED indicators need to provide different packaging types and sizes for different applications. Panel mount LEDs, which are assembled within a housing, can provide many lens types of different materials and outlines, as well as different lead lengths. Additionally, there are indicators classified as through-hole and surface-mount, which are designed for circuit board. The common LED indicator has a diameter from 2mm to 5mm. But their are large one available of 10mm or 20mm, which are usually used for panel mount. When multiple LED indicators are required, the horizontal and vertical arrays of LED can be selected as an appropriate solution in order to save space.
Other Resources
- Light-Emitting Diode
- LEDS: From Indicators to Illumination
- Performance Characteristics of Light-Emitting Diodes
- LED Technical Information
- What are LED Lamps
- LEDs Are Still Popular and Improving after All These Years
- Detailed information of LEDs
- Glossary of Lighting
Glossary:
| Candela(cd) | The luminous intensity as defined by the international metric standard (SI). The term, retained from the early days of lighting, defines a standard candle of a fixed size and composition as a basis for evaluating the intensity of other light sources. |
| Flux | The sum of all the lumens (lm) emitted by a source (see lumen). |
| LED | A Light Emitting Diode (LED) is a solid-state semiconductor device that converts electrical energy directly into light. |
| Lumen (lm) | The international (SI) unit of luminous flux or quantity of light and equals the amount of light that is spread over a square foot of surface by one candle power when all parts of the surface are exactly one foot from the light source. |
| Luminous Flux | The total perceived power emitted in all directions. |
| Luminous Intensity | Measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. |
| Lux (lx) | The SI (International) unit of illuminance, or luminous flux incident on a unit area, frequently defined as one lumen per square meter (lm/m2). |
| Viewing Angle | Viewing angle is the maximum angle at which a LED can be viewed with acceptable visual performance |
| Wavelength | Distance between two successive points of a periodic wave; the wavelengths of light are typically expressed in nanometers (nm), or billionths of a meter. |