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  • Collin Cunningham: People are fascinated by light.

  • I mean just glancing over at a display of flashing lights can

  • grab my attention. Do you ever remember sitting

  • around a campfire? Staring at the flames and just

  • being totally transfixed, almost like if you're watching

  • TV. It's comforting,

  • and it can even by hypnotic. Recently, technology has made

  • creating light a whole lot easier to do.

  • For that, we have this little guy to thank.

  • The light emitting diode, or LED for short.

  • LEDs have a lot of different uses, from a simple power on

  • indicator to traffic signals. LEDs use about ten percent of

  • the energy of a traditional light bulb, and they can last

  • about thirty times longer. That makes them a pretty big

  • hit with businesses looking to do large scale visual

  • communication. The first person to ever report

  • the effects of a light emitting diode was researching another

  • form of communication. In 1907, a man by the name of

  • H. J.

  • Round was researching radio waves for Marconi Labs.

  • He was using a device called a cats whisker detector,

  • which no, does not contain any cats or part of cats.

  • Round was searching for a sweet spot on a crystal silicon

  • carbide when he noticed something odd.

  • Part of the crystal started to glow, it lit up a pale yellow,

  • and that was an LED. H.

  • J. Round's crystal experiment was

  • so cool and simple that I had to try it myself.

  • So I got a piece of silicon carbide, then I hooked that up

  • to the positive lead on my power supply.

  • That's an alligator clip. I hooked a little sewing needle

  • to the ground on my power supply.

  • Then I began to search for light emitting zones.

  • I built my own sort of cats whisker detector in order to

  • keep the needle in place on a particularly bright spot I

  • found. Now I can sit back and enjoy

  • the warm glow of a homemade LED anytime I choose,

  • even though it's pretty dim, but it's still cool.

  • As far as we know, Round's research into light

  • emitting crystals ended here, which is a shame because he was

  • definitely on to something. But of course that's not the

  • end of the story. Fifteen years later,

  • in imperial Russia, a scientist and inventor named

  • Oleg Vladmirovich Losev noticed that certain diodes in radios

  • started to glow a bit when in use.

  • Losev conducted a lot of heavy research and published his

  • findings in several languages. But, sadly, they seem to have

  • gone unnoticed. It wasn't until 1962,

  • that a visible light emitting diode was made practical by Nick

  • Holonyak working at General Electric.

  • He's widely known as the father of the LED.

  • The technology that Holonyak brought to the public is

  • remarkably similar to our crystal experiment.

  • A thin metal wire connects one side of the circuit to a small

  • piece of semi-conductive material on the other side.

  • The LED's two leads are cut to different lengths to show you

  • how it should be connected. The longer one is called the

  • anode, and that connects to positive.

  • The shorter is the cathode, and that goes to negative.

  • To power an LED, you can just use a simple coin

  • cell. This is a CR2032.

  • And just make sure the longer lead is on the positive side,

  • which is wider and smoother, and negative is on the other.

  • If you plan to use a battery, let's say a nine volt,

  • you'll also need a resistor to limit the current so we don't

  • burn out the LED.

  • Connect negative to the cathode, the shorter lead,

  • and we'll put a 470 ohm resistor between the positive

  • battery and the anode. For more useful info,

  • check out the LED Center, and there's a lot of great

  • history at the LED Museum. For all types of project ideas,

  • info, and inspiration head over to

Collin Cunningham: People are fascinated by light.

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B1 led emitting diode glow positive cathode

MAKE presents: The LED

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    Sea Monster posted on 2015/05/01
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