LED’s
LED = Light Emitting Diode
LED’s are used in many applications from household lights to HD sports arena screens. They have so many useful applications there is an entire organization dedicated to what they call “the LED Revolution”
(http://www.creeledrevolution.com/system/files/imagecache/testimonial_size/testimonial/photos/smithsonianLR24.jpg)
http://www.creeledrevolution.com/blog/2010/03/26/high-definition-screens-at-american-airlines-center-put-hd-in-every-seat/
In the Smithsonian’s National Air and Space Museum they are moving into the LED Revolution replacing all the old – sometimes 30years old – light bulbs with LED’s that will allow for cheaper maintenance and save more energy than their Mercury vapor predecessor. These lights also produce less heat and emit virtually no ultraviolet rays which protect the artifacts in the museum. The LED lights are designed for 50,000 hours which = 17years at 8hours a day 7days a week.
(http://www.creeledrevolution.com/blog/wp-content/uploads/2010/03/AmericanLED1.JPG)
http://www.creeledrevolution.com/revolutionaries/new-smithsonians-national-air-and-space-museum
LED’s are semiconductors that convert electricity into light. They’ve been around since 1960’s, but is just recently becoming used for spatial lighting. White LED’s weren’t possible until 1993 when Nichia used a blue indium gallium chip with a phosphor coating that created the white light from one diode. Each diode is about 1/4″ diameter and use 10milliamps to work a 1/10 of a watt.
Currently a typical residential LED is about 20 Lumens per watt. Efficacies have been documented up to 100 in laboratories. LED’s are best at unidirectional lighting leading to unique arrays and decorative fixtures. LED’s are also more durable then incandescent and don’t flicker. However, excessive heat can dramatically reduce output and lifetime.
Uses include:
* Task and reading lamps
* Linear strip lighting (under kitchen cabinets)
* Recessed lighting/ceiling cans
* Porch/outdoor/landscaping lighting
* Art lighting
* Night lights
* Stair and walkway lighting
* Pendants and overhead
* Retrofit bulbs for lamps
Definition of efficacy: “The efficiency of the bulb to convert electricity into light”
(http://www.toolbase.org/products/led_bulb.jpg)
http://www.toolbase.org/Technology-Inventory/Electrical-Electronics/white-LED-lighting
Definition of a Lumen: “a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candle intensity”
http://www.merriam-webster.com/dictionary/lumen
Definition of efficacies: : “The efficiency of the bulb to convert electricity into light”
LED’s work similar to a motor meaning when connected to a battery they can take energy to produce light, but also they can take light and produce energy.; the more intense the light the higher the voltage. Also the lights will only produce energy with a specific wavelength of light, meaning you can use it as a sensor to read how much of a specific wavelength of light is produced. If this is connected to a voltmeter this could be read then feed possibly into a program that could turn something on or off. You then could use a laser to trigger a device.
(http://mvh.sr.unh.edu/mvhtools/images/lightsources.png)
http://mvh.sr.unh.edu/mvhtools/led_sensors.htm