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LDK Experiment 2: Multiple LED Circuits alearn.sparkfun.com
tutorial
Available online at: http://sfe.io/t37
Contents
IntroductionGather MaterialsAdding LEDs to a Parallel
CircuitCreating a Multi-LED Series CircuitResources and Going
Further
Introduction
Welcome to the second experiment of the LilyPad Design Kit,
where we'll learn how to add morethan one LED to a circuit.
Additionally, we'll learn about the two types of standard
circuitconfigurations: series and parallel.
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LDK Experiment 2: Multiple LED Circuits SparkFun Wish
List
When working with LEDs, you’ll use parallel circuits very often.
In addition to being able to turn onmore components with less
voltage, they’re more durable. In a series circuit, if one LED
getsdamaged, all of the LEDs will stop working. In a parallel
circuit, one broken LED won’t stop theothers from lighting up! You
may have heard of this effect, or experienced it firsthand, in
Christmaslights.
In spite of the reasons to prefer parallel circuits for most
projects, no education in basic circuits iscomplete without
discussing series circuits, so we’ll give one a try!
Suggested Reading
Here are a few related tutorials that you might want to read
over or refer to:
LDK Experiment 1Parallel and Series circuitsLight-emitting
Diodes (LEDs)How do I power my project?
Gather Materials
Here are the components you'll need for this circuit. If you're
using the LilyPad Design Kit, you'vealready got these!
(2) LilyPad Coin Cell Battery Holder - 20mmDEV-10730
If you're looking for a simple way to add a battery to your
LilyPad project, the LilyPad Coin Cell Battery Holder …
Conductive Thread Bobbin - 30ft (Stainless Steel)DEV-10867
This is 30 feet of conductive thread spun from stainless steel
fiber and wound on a plastic bobbin. Use it to sew…
Needle SetTOL-10405
This set of sewing needles is a must-have when stitching
together your next e-textile project. Each envelope c…
(2) Coin Cell Battery - 20mm (CR2032)PRT-00338
CR2032 Lithium metal 3V 250mAh button cell battery. Great for
powering low power processors or blink an LE…
LilyPad Rainbow LED (strip of 7 colors)DEV-11842
This is the LilyPad Rainbow LED strip, a simple seven pack of
every LilyPad LED that we have, each still attac…
View LDK Experiment 2: Multiple LED Circuits on SparkFun.com
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You’ll also want scissors, fabric, an embroidery hoop, and
possibly a needle threader.
Go ahead and get the fabric set up in the embroidery hoop, and
start with a threaded, knottedneedle.
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Adding LEDs to a Parallel Circuit
We’re going to use the circuit you made in LDK experiment 1 as
the foundation for our parallelcircuit. In a parallel circuit, you
sew all of the positive pins to each other and all of the negative
pinsto each other. As in experiment 1, you never want to allow the
positive and negative traces to comeinto contact with each other.
For this circuit, don’t use any red or yellow LEDs you still have
-- you’llneed those for the series circuit!
Note: Remember to take your battery out while you’re sewing, to
prevent battery drain and shortcircuits while you're sewing.
Positive Trace
Start with your needle threaded and knotted. Sew a new stitch
into the positive pin of the LED youused on the initial circuit,
and add another tight stitch on top of the stitches holding it
down. Due tothe uninsulated nature of conductive thread, the thread
you are currently sewing with is nowconductively connected to your
original circuit. The trace you start sewing now is a continuation
ofthe positive trace that already existed in the original
circuit.
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Green = correct traces, Red = incorrect traces.
From here, sew in a line to where you’d like the positive pin of
your next LED. You’re going to needto keep the positive and
negative traces parallel to each other (hence ‘parallel’ circuit),
so don’tplace the new LED such that its position is reversed from
the original LED.
Sew the positive pin of the second LED down with three stitches,
as you have done with allprevious pins. From here on, I’m just
going to tell you to sew the pins down, but please continue touse
several stitches per pin! Continue sewing to the third LED, and sew
that positive pin as well.Keep thinking in a parallel fashion as
you locate the third LED.
That’s the end of the positive trace for this circuit. Go ahead
and tie your thread off, and cut it.
Negative Trace
Begin with a newly threaded needle. As you did on the positive
trace, sew one stitch around thenegative pin of your LED on the
original circuit, to connect your new trace to the old.
Stitch from here in a line to the new LEDs, sewing each one down
as you go. Be careful not to
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cross or contact your positive trace while you do this.
Knot and cut your thread on the finished negative trace, and do
a quick check for stray threads,long knot-ends, and anything else
that might cause a short circuit.
Double-check that you don't have any loose threads, crossed
traces, or other visible problem spots.If everything looks good,
slide your battery into the holder, positive side up. All three of
your LEDsshould light up. You’ve successfully completed a multi-LED
parallel circuit!
Creating a Multi-LED Series Circuit
One of the things that’s very different about a series circuit
is the power requirement. To create thiscircuit, you’re going to
need more power than you needed for the parallel circuit, so we’ll
be usingtwo batteries instead of one. In the parallel circuit, we
connected all of the positive pins to eachother, and all of the
negative pins to each other. In the series circuit, things are very
different. We’llbe creating our circle by connecting each positive
to a negative, each negative to a positive. You’llwant to use red
and yellow LEDs for this circuit, because they have the lowest
forward voltage droprequirement.
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Once again, let’s start with the battery packs. You’ll need two
of them, so we're going to combinethem in a series circuit. Start
by placing the battery pack you’d like to be on top, and make sure
youleave room for another one on the fabric below it. Point the
negative pins down towards the secondbattery pack location.
Sew down one negative pin with a few stitches.
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Next, place your second battery pack directly underneath the
first one, with the positive pinspointed towards the negative pins
of the first battery pack. Sew just one or two stitches from
thenegative pin you’ve already sewn down to the closest positive
pin on the other pack, and stitch thatpositive pin down.
Sew from this positive pin, in several stitches to the other
positive pin on this board, and sew thesecond pin down.
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From this positive pin, take another stitch or two up to the
remaining negative pin on the first batterypack.
You should now have one set of negative pins attached to one set
of positive pins, with another setof each unsewn positives and
negatives pointed up and down, respectively. Knot and cut
yourthread, getting ready to sew a new trace. Start up at the
unsewn positive traces, which should be atthe top edge of your top
battery pack. Sew down the pin furthest from the side you’d like
your LEDson, then sew a few stitches to the other positive pin and
sew that down as well.
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From here, sew to where you’d like your first LED, and sew down
the positive pin. Knot and cutyour thread here.
Re-knot your thread and sew down the negative pin of the same
LED with the new length of thread.The positive and negative sides
of this LED should not be connected to each other by any thread.Sew
from this negative pin to where you would like the positive pin of
the next LED to be, and sewthat positive pin down. Once again, knot
and cut your thread.
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Start again with your new thread and sew the negative pin of the
second LED to the positive pin ofthe third LED, then knot and cut
your thread.
With this last independent length of thread, sew down the
negative pin of the third LED, and sewfrom there to the nearest
negative pin of the bottom battery pack; these negative pins should
be thelast ones left unsewn. continuing this trace, sew the first
negative battery pin down.
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Sew a few stitches to the other negative pin of the battery
pack, and sew that down as well. Knotand cut your thread, and take
a quick look for long thread end, dangling thread, loose stitches,
orother problems that could cause shorts.
Once you’re sure you don’t have any extraneous thread mucking up
your circuit, put both batteriesin. All three LEDs should light up!
Depending on the colors you’ve used, you’re likely to see that
thelights in the parallel circuit are significantly brighter than
the ones in the series circuit.
Resources and Going Further
Ready to learn more? Explore the next LDK experiment or have a
look at some of our other e-textile tutorials.
LDK Experiment 3E-Sewing Kit
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E-Sewing Kit Part 2
learn.sparkfun.com | CC BY-SA 3.0 | SparkFun Electronics |
Niwot, Colorado
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LDK Experiment 2: Multiple LED Circuits a learn.sparkfun.com
tutorialAvailable online at:
http://sfe.io/t37ContentsIntroductionSuggested Reading
Gather MaterialsAdding LEDs to a Parallel CircuitPositive
TraceNegative Trace
Creating a Multi-LED Series CircuitResources and Going
Further