University of Wisconsin - Madison Materials Research Science and Engineering Center Education and Outreach

 

LEDs - Light Emitting Diodes

New Applications

LEDs are being used increasingly where low power consumption and long lifetimes are important. Here are a few examples. If you have seen other applications you would like to share, please send your digital image to:mcondren@cbu.edu. If you do not have a digital camera or scanner, send us your print and we canscan it.

Prints should be sent to:

Prof. Mike Condren
Department of Chemistry
Christian Brothers University
650 East Parkway South
Memphis, TN 38104

Examples

These Laser Lights brand shoes feature
red, yellow, and blue LED illumination.

 


Bi-color LEDs as used in programmable message boards.
The bi-color devices contain both a red and a green chip.
When the red and green chips are turned on simultaneously, they produce a yellow color.


Radar unit of Shorewood Hills, WI Police Department which displays your speed in arrays of red LEDs.


New Sony JUMBOTRON Instant Replay screen
Liberty Bowl Stadium in Memphis, Tennessee.


© Copyright 1999, The Nasdaq Stock Market, Inc. Reprinted with the permission of The Nasdaq Stock Market, Inc.

It is claimed that this is the world's largest LED array, at 120 x 90 feetand 18 million LEDs.

For a live view, see the Webcam


The Rainbow LED Board


Microscopic view of tri-color LED with plastic lens removed.

The LED on this board contains four semiconductor chips: 1 red, 1 green and 2 blue chips. The red, green and blue colors are controlled independently, allowing a rainbow of color possibilities. Yellow can be created by mixing red and green; cyan by mixing green and blue, and magenta by mixing red and blue. White light can be created by mixing red, green and blue equally.

For more information about color mixing, visit the web site of General Atomics Sciences Education Foundation .


The brake light on this van uses LEDs, while the tail lights use incandescent bulbs.


The LEDs show a peak in their spectrum at 667 nm. The tail lights use incandescent bulbs and show a peak in their spectrum at 647. Thusthe LEDs are appear redder.


All of the newer city buses in Madison have LEDs on the rear as brake and tail lights, as well as turn signals.

The newest buses have all of the external lighting, except the headlights, as LEDs. This includes the destination boards on the front and right side and the route number on the right front and rear of the bus.


Medium size truck are also using LED tail/brake lights such as this FedEx truck in Chicago.

 

Signal® Mirror Safety Systems.
Signal® Mirrors are a registered trademark of K.W. Muth Co. Inc.
Picture is used with permission from K.W. Muth Co. Inc.

K.W. Muth Co. Inc. is manufacturing Signal® Mirrors that use LEDs in the side view mirrors. These appear as original equipment on some pickup trucks, sports utility vehicles, vans, and motorcycles. Their Wide Angle Signal® Mirror Kit can be fitted to any vehicle.


LED flashers for bikes.

 

LEDs are being used increasingly where brightness, low power consumption, and long lifetimes are important safety concerns. Another advantage is that, if one element fails, the whole assembly does not stop working. As described in the Hewlett-Packard press release cited below, LEDs illuminate 200 milliseconds faster than conventional incandescent lamp, giving the driver of the trailing vehicle one car length greater stopping distance at 65 mph.

 


How many LEDs are in this red traffic light?


Note the difference in the color between the LEDs on top and the incandescent bulb/red lens on bottom.


LED "Do Not Walk" indicator.

For more information on traffic light applications, see the MRSEC Traffic Light Web page


Railroad crossing flashers using LEDs. Use this link for more information about Railroad Applications of LEDs.


Exit signs.


Each dot is a cluster of LEDs.
Parking Information
John Wayne Airport
Orange County, CA


Each dot is a cluster of LEDs.
Construction Site Traffic Arrow
Orange County, CA


Linear arrays of photo-diodes are being used as detectors in spectrophotometers such as this model by Ocean Optics. In this particular device, the light enters the detector through the fiber optic cable to the right. The light is dispersed by the grating at the bottom of the device and detected by the array of photo-diodes near the top. For more information about diode arrays and charge coupled devices, see Charge Coupled Devices.

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