Circuitry
101: How to Hook Up LEDs
The
direct url for this guide is:
http://tutorial.lsdiodes.com
Below
we've created a very basic
guide to help people
unfamiliar with circuits get
their LEDs up and running
without blowing them out and
wasting all their money. IT IS
VERY BASIC!! Current is hardly
ever mentioned, not because
it's not important, but
because we've found it makes
things confusing when trying
to teach people about this
sort of thing. If we've done a
bad job explaining things or
if you have a question this
doesn't answer, use the
contact form at the bottom of
this page to let us know
what's up.
When
LEDs are placed in a series,
the voltage is dispersed
between the LEDs, meaning less
voltage goes to each LED. This
can be very useful. For
example, if a 12 volt adapter
were powering one LED, there'd
be 12V going through that LED
which is way too much for any
LED to handle and would result
in a rather unpleasant burning
smell.
However,
if you take that same 12V
power source and put 4 LEDs in
series, there would be 3V
going to each LED and
(assuming the LEDs are made to
run off 3V) each would be
powered and just dandy. Check
out this illustration:

It's
important to notice how the
LEDs are positioned: (-) (+),
(-) (+), etc. making sure that
the end (-) connects to the
(-) wire and the end (+)
connects to the (+) wire, if
any LEDs are backwards nothing
bad will happen, they just
won't turn on.
If
three LEDs were in series with
a 12V source, each would
receive 4V, if six were in
series, each would receive 2V,
etc.
"But
what if I have four LEDs
powered from a 12V source and
I want each to receive less
than than 3V/ea?" This
is where the little
'Resistor(s)' squiggly comes
in. By adding a resistor it's
possible to tone down the
amount of voltage each
receives. To find out what
value resistor you should use,
use an led calculator such as this
one . Go
to the middle form where it
says 'LEDs in series' and
simply type in your power
sources' voltage, the LEDs'
voltage you'd like and the
LEDs current capability (use
20mA.) It then tells you what
ohmage resistor to stick in
the circuit.
Parallel or
"How do I power lots of
LEDs off a lower voltage
source?"
Let's
say you wanted to power three
of your brand new LEDs off a
3V battery pack (two 1.5V AA's
in series, make sense?) you
found lying around. If you
were to series the three LEDs
there'd be 1V going to each (3
Volts / 3 LEDs = 1V for each
LED). That's not enough to
power your LEDs! You want them
to have the full 3V going to
each. Here's how:

How
this works is that while every
LED receives the same amount
of voltage, the current of the
source is dispersed between
the LEDs. What this means for
you is that you have 20 LEDs
paralleled off a battery, it's
going to drain the battery a
lot quicker than if you only
had 2 LEDs in parallel. If
you're paralleling off a wall
adapter, for instance though,
the source can constantly
renew itself so you can
essentially parallel as many
as you'd like without fear of
draining the wall
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