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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http://learn.sparkfun.com/tutorials/ldk-experiment-1-lighting-up-a-basic-circuithttps://learn.sparkfun.com/tutorials/series-and-parallel-circuitshttps://learn.sparkfun.com/tutorials/light-emitting-diodes-ledshttp://learn.sparkfun.com/tutorials/how-to-power-a-projecthttps://www.sparkfun.com/wish_lists/71106https://www.sparkfun.com/products/10730https://www.sparkfun.com/products/10867https://www.sparkfun.com/products/10405https://www.sparkfun.com/products/338https://www.sparkfun.com/products/11842https://www.sparkfun.com/wish_lists/71106

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