Brief history of light emitting diodes and LED technology.

1. By Shelly Shinevar

2. Invention of the Light Bulb
With 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 point
contact on a crystal of SiC recreates
H. J. Round's original experiment from
1907.

10. Parts of an LED. Although not directly labeled, the flat bottom surfaces of the anvil
and post embedded inside the epoxy act as anchors, to prevent the conductors
from being forcefully pulled out from mechanical strain or vibration.

11. Type: Passive, optoelectronic
Working principle: Electroluminescence
Invented: 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 Haitz's law. Light output per LED as a function of
production 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 three
different sized LEDs -- 8 mm, 5 mm and 3 mm -- with a
wooden 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.[] The
color of the plastic lens is often the same as the actual color of light emitted, but not
always. For instance, purple plastic is often used for infrared LEDs, and most blue
devices have clear housings. There are also LEDs in surface-mount technology
(SMT) packages, such as those found on cell phone keypads (not shown).

19. Blue
LEDs.

21. Calculator LED display, 1970s.

22. A green surface-mount LED mounted on an Arduino circuit board.

23. High-power light-emitting diodes (Luxeon, Lumileds)

24. 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.

25. 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.

26. City of Southgate’s Outdoor LED Lights
EECBG LED Demo Grant: $98,000

27. City of East Lansing’s Historical Lightpoles with LED Lights
EECBG LED Demo Grant: $112,500

28. Delhi Township’s new LED lights
Part of an EECBG Multi-Purpose Grant: $112,847

29. The City of Wayne installed indoor LED lights as part of a
Multi-Purpose EECBG project. The city received $88,124.

30. City of Wayne’s indoor LED Exit sign lighting.

31. Another type of indoor LED light installed by the City of Wayne.

32. Traffic light using
LED

33. Overhead LED lighting on a train, replacing the fluorescent bulbs used in the past.

34. LED destination signs on buses, one with a colored route number.

35. LED daytime running lights of Audi A4

36. A large LED display behind a disc jockey
.

37. LED panel light source used in an experiment on plant growth. The findings of
such experiments may be used to grow food in space on long duration missions.

38. LED Illumination.

39. LED lights reacting dynamically to video feed via AmBX
.

40. 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.

41. The filament-style bulb, which hangs in the Livermore fire station, has been glowing
continuously 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 conspiracy
theory 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.

42. The End