Light-emitting diodes (LEDs)

LEDs (light-emitting diodes), the modern craze in
lighting, hold the promise of making obsolete Edison’s
greatest invention, the incandescent light bulb. They are
in toys, in automobiles, in stop signs, in every color-
shifting gadget, and are even being added to clothing.
These techno-sequins are arguably the greatest crafting
material invented.
Why are LEDs so darn cool?First of all, they are
compact and emit bright light lasting as long as 10 years.
Secondly, unlike traditional light bulbs, they don’t get hot.
And most importantly, they consume very little power.
This means that you can continuously run a super-bright
LED off of a small battery for more than a hundred hours.
LEDs come in several colors, brightness levels, sizes,
and shapes. The two types of LEDs that you will use in
these projects are standard LEDs and high-flux LEDs.
These and several others are discussed in detail at the
end of this section. Before you start working with LEDs,
there are a few essentials you need to know.

Understanding the Technical
Specifications for LEDs

Following is an explanation of all the technical data and
symbols that come with your LED package. With an
understanding of a few basic terms, you will be able to
easily choose the right LED for your project and use
online resistor calculators to determine the right resistor
for your circuit.

Forward Voltage (Vf): Also referred
to as the forward voltage drop, the VF
is the minimum amount of voltage
needed to light up an LED.

Luminous Intensity (Iv): The IV is the
amount of light emitted from an LED in
a particular direction. It is measured in
millicandela (mcd). For our purposes,
consider luminous intensity the
“brightness” of an LED. The greater
the millicandelas, the brighter the bulb.

Viewing Angle: The viewing angle is the spatial
distribution or spread of light. It is expressed in degrees
that measure the width of the light beam. LEDs with a
small viewing angle produce a more focused beam, and
LEDs with larger viewing angles produce a softer, more
dispersed beam.

written by Anthony


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