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LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
LED: Lighting the Way
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LED: Lighting the Way

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Brief history of light emitting diodes and LED technology. …

Brief history of light emitting diodes and LED technology.

Published in: Technology
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  • This is the end. And now, for your listening enjoyment…(play video/audio).
  • Transcript

    • 1. By Shelly Shinevar
    • 2. Invention of the Light BulbWith the invention of the light bulb, lighting became an easier issue for businesses and homes on a massive scale.
    • 3. How was the light bulb invented?Someone had a bright idea, but who was it?
    • 4. The History of the Incandescent Lightbulb 1809 - Humphry Davy, an English chemist, invented the first electric light. Davy connected two wires to a battery and attached a charcoal strip betwween the other ends of the wires. The charged carbon glowed making the first arc lamp. 1879 - Thomas Alva Edison invented a carbon filament that burned for forty hours. Edison placed his filament in an oxygenless bulb. (Edison evolved his designs for the lightbulb based on the 1875 patent he purchased from inventors, Henry Woodward and Matthew Evans.)
    • 5. What does this light bulb have in common with LED lighting?
    • 6. What does LED stand for? Light Emitting Diodes
    • 7. Brief History of LEDs 1907 – Electroluminescence is discovered by a British experimenter, using a crystal of silicon carbide and a cat’s-whisker detector. 1927 – Creation of the first LED by a Russian scientist. 1955 – Braunstein of the Radio Corp. of America observed infrared emission generated by simple diode structures. 1961 – American experimenters, working at Texas instruments, receive the patent for the infrared LED. 1962 – Nick Holonyak, Jr., while working at General Electric Co., develops the first practical visible-spectrum (red) LED. He is seen as the “father of the light-emitting diode.” 1968 – The Monsato Company was the first organization to mass-produce visible LEDs. Hewlett-Packard introduces LEDs. 1970s – Commercially successful LED devices (under 5 cents each) produced by Fairchild Optoelectronics. 1972 – First yellow LED is invented by a grad student of Holonyak’s. 1976 – T.P. Pearsall created the first high-brightness, high-efficiency LEDs for optical fiber telecommunications.
    • 8. How do LEDs wor k? An LED is a semi-conductor light source. They contain a tiny flake of semi-conducting material. (Often less than 1 square millimeter.) Although not conductive in pure form, the materials become conductive when doped with impurities. A current is created that induces electroluminescence. Semiconductor properties determine light output color.
    • 9. Green electroluminescence from a pointcontact on a crystal of SiC recreatesH. J. Rounds original experiment from1907.
    • 10. Parts of an LED. Although not directly labeled, the flat bottom surfaces of the anviland post embedded inside the epoxy act as anchors, to prevent the conductorsfrom being forcefully pulled out from mechanical strain or vibration.
    • 11. Type: Passive, optoelectronicWorking principle: ElectroluminescenceInvented: Nick Holonyak Jr. (1962)Electronic symbol:Pin configuration: anode and cathode Red, pure green and blue LEDs of the 5mm diffused type.
    • 12. Lighting engineers determine the efficiency of lighting devices by measuring the lumens of light output per watt of electrical input.Researchers have developed prototype LEDs with a luminous efficacy of over 200 lumens per watt.
    • 13. The development of LED technology has caused their efficiency and light output to rise exponentially. This trend is called Haitz’s law.Illustration of Haitzs law. Light output per LED as a function ofproduction year; note the logarithmic scale on the vertical axis.
    • 14. The inner workings of an LED
    • 15. Combined spectral curves for blue, yellow-green, and high-brightness red solid-state semiconductor LEDs.
    • 16. Spectrum of a “white” LED showing blue light directly emitted by the LED and the more broadband light emitted.
    • 17. LEDs are produced in various sizes. Here are threedifferent sized LEDs -- 8 mm, 5 mm and 3 mm -- with awooden matchstick for scale.
    • 18. LEDs are also produced in a variety of shapes. The 5 mm cylindrical package (red,fifth from the left) is the most common, estimated at 80% of world production.[] Thecolor of the plastic lens is often the same as the actual color of light emitted, but notalways. For instance, purple plastic is often used for infrared LEDs, and most bluedevices have clear housings. There are also LEDs in surface-mount technology(SMT) packages, such as those found on cell phone keypads (not shown).
    • 19. BlueLEDs.
    • 20. Calculator LED display, 1970s.
    • 21. A green surface-mount LED mounted on an Arduino circuit board.
    • 22. High-power light-emitting diodes (Luxeon, Lumileds)
    • 23. Advantages to using LEDs Efficiency – Emit more light per watt than incandescent light bulbs. Use 5x less power than CFLs. Color – Emit light of an intended color more efficiently. Size – Can be very small. On/Off time -- Light up very quickly. Cycling – Ideal for uses subject to frequent on-off cycling. Dimming – Very easily dimmed. Cool light – Radiate very little heat. Slow failure – Mostly fail by dimming over time. Lifetime – Can have a relatively long useful life. Shock resistance – Difficult to damage with external shock. Focus – Can be designed to focus its light.
    • 24. Disadvantages to using LEDs High initial price – Currently more expensive, price per lumen, on an initial cost basis than most conventional lighting technologies. Temperature dependence – Largely depends on the ambient temperature of the operating environment. Voltage sensitivity – Must be supplied with the voltage above the threshold and a current below the rating. Light quality – Most cool-white LEDs have spectra that differ significantly from an incandescent light. Area light source – Difficult to apply if a spherical light field is needed. Electrical polarity – Will only light with correct electrical polarity. Blue hazard – Concern that blue and cool-white LEDs may exceed eye-safety limits. Also, blue pollution is a concern. Droop – Efficiency tends to decrease as one increases current.
    • 25. City of Southgate’s Outdoor LED Lights EECBG LED Demo Grant: $98,000
    • 26. City of East Lansing’s Historical Lightpoles with LED Lights EECBG LED Demo Grant: $112,500
    • 27. Delhi Township’s new LED lightsPart of an EECBG Multi-Purpose Grant: $112,847
    • 28. The City of Wayne installed indoor LED lights as part of aMulti-Purpose EECBG project. The city received $88,124.
    • 29. City of Wayne’s indoor LED Exit sign lighting.
    • 30. Another type of indoor LED light installed by the City of Wayne.
    • 31. Traffic light usingLED
    • 32. Overhead LED lighting on a train, replacing the fluorescent bulbs used in the past.
    • 33. LED destination signs on buses, one with a colored route number.
    • 34. LED daytime running lights of Audi A4
    • 35. A large LED display behind a disc jockey.
    • 36. LED panel light source used in an experiment on plant growth. The findings ofsuch experiments may be used to grow food in space on long duration missions.
    • 37. LED Illumination.
    • 38. LED lights reacting dynamically to video feed via AmBX.
    • 39. So, what does this light bulb have in common with LED lights? It was built to last. This is the Centennial Bulb. It’s the longest burning light bulb in history! It is now in its 110th year of illumination in a Livermore, California firehouse.
    • 40. The filament-style bulb, which hangs in the Livermore fire station, has been glowingcontinuously since 1901. The secret to its longevity apparently died with its inventor, a French immigrant professor named Adolf Chaillet. The Light Bulb Conspiracy (a video documentary) shows how many early incandescent lightbulbs lasted upwards of 2,500 hours. But then the leading manufacturers of the time formed an international cartel (Phoebus) whose proclaimed goal was to standardize the lightbulb. Its real intent, as the conspiracytheory goes, was actually to shorten the lifespan of all lightbulbs. By the 1940s, bulbs were burning for 1,000 hours, which is their expected lifespan today.
    • 41. The End

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