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L.E.Ds
are available in many different coloured shapes and sizes. They can be used:
as indicators, to illuminate, or to create displays.
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They light up traffic
lights on our roads.
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They can be
used to tell
you that your
food is
cooking in
the
microwave. They conveniently
show when your TV,
or computer,
is turned on, or on standby.
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They can
be used
to display numbers
in clocks. (Did you
know that James
Bond's first digital
watch used L.E.D.
technology?)

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They can
let you know a
device is
switched on
and functioning.
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Over the past fifty years,
the original technology has been developed to produce flat panel screens and higher energy devices. These are now commonly used in computer monitors, widescreen TV's, car headlamps and lighting for theatre shows or concerts.The L.E.D. has become a very popular component and is seen in many of the products we buy - especially around Christmas!
An
L.E.D. Close-Up.
When
a small current flows through an L.E.D. (normally
about 20-30 milliamps) it will light up. Unlike an older filament bulb, its two connections ( + and -) must be connected
correctly to the power source for it to work.
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Super
Bright White L.E.D.
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Standard
Red L.E.D.
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Symbol
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The
two different connections to the L.E.D. are called:
1, The Anode (+)
2,
The Cathode (-).
These
can be identified by looking for either the long (+) or
short (-) legs. The flattened edge of the led is always nearest
to the Cathode (-). You can see this in the image above.
Getting
an L.E.D. to light up safely.
L.E.D.s are semiconductors and most of them cannot work
safely in a circuit on their own. This is because they can allow too much current to flow. By comparison, we have seen how older traditional filament bulbs will only take the current they need when connected-up to a power supply.
To
protect the L.E.D., it is therefore necessary to include an electronic component called a resistor. This is connected in series with the L.E.D. and power supply. The resistor limits the current and stops the L.E.D. over-heating and possibly blowing-up!
Please go on to the next section
to learn more about this.
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