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 Makezine.com.