Conductive Jelly Donuts - an Introduction to Sewing Circuits With Makey Makey

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About: Computers are going bananas! Use #makeymakey to practice invention literacy and connect the world to your computer.

We noticed on Twitter that a lot of our Scratch and Makey Makey fanatics wanted to know more about sewing circuits, so we crafted up this tutorial to give you a quick introduction on sewing circuits and how you can sew some modular pieces. (This is basically the start to a soft circuit version of this rad "Circuit Block Tutorial" by 3DNicholos. Woo!)

Supplies needed for this project:

(If you like this idea of alligator clipping and testing circuit components and have a limited budget, check out Scrappy Circuits! It's a similar idea to 3DNicholos's project, but with office supplies and cardboard!)

Supplies:

Step 1: Sew a Power Source

The first step to understanding circuits is understanding how to power them! You can power these modules with Makey Makey, but we thought it might help you understand sewing circuits even more if you sew your own power source.

Make a Template:

Download the battery holder template, then get some felt and conductive thread, and let's get sewing!

All you need to sew a battery holder is to sew two conductive pads for the battery to send power through. The most important thing is that these two threads never cross. If they do, you'll short your circuit!

The easiest way to ensure this is to draw your pattern on your felt and visually test your design with a coincell battery. Make sure the two legs from the felt won't touch, and make sure the area where you sew your conductive pad will make a firm connection with the battery.

Sew Positive Side:

Once you are sure your design will work, grab your conductive thread, and cut about 2 feet of thread (or measure an arm's length of thread.) Tie a knot in one end and make sure you keep the opposite end short on your needle.

Sew about 5-6 stitches to make a patch on the positive side of your battery holder. Make sure not to pull the thread too tight or your fabric will pucker. Use a running stitch to run up the positive leg of your holder. Then sew about 4-5 stitches on the end of this fabric for your alligator clip to attach to. Tie a knot and cut your thread short!

Sew Negative Side:

Repeat this same process for the negative side of the template.

Place Battery:

Sandwich your battery inside, test it by alligator clipping to an LED, and use non-conductive thread to sew your holder together.

Tips:

  • Conductive thread is sticky, make sure you use a short length as a beginner.
  • Conductive threads need to be sewn neat and tight. If you sew loosely, you run the chance of the thread touching the other side and shorting your circuit. (One the other hand, this is a great way to learn to debug a circuit! Once I thought I'd busted my sewing, but really a thread from my negative trace was just barely touching the positive trace and stealing all those lazy electrons.)
  • Depending on the thread you buy, some conductive thread will pull apart easily. This means you can yank to cut the thread, but it also means you might accidentally yank too hard when sewing and accidentally break your thread!
  • You'll have to sew close to the battery with your nonconductive thread to make sure the holder is sandwiching that battery really tight! Otherwise, the battery might not make a good connection with your sewn conductive pads.
  • If you don't sew wide enough stitches for your conductive pads, they might not do their job well. If this happens, just grab your thread and sew the area wider. Since the thread is conductive, it won't matter you are using a new piece of thread!

Step 2: Sew an LED

Now to sew an LED we can power with our freshly crafted battery pack or Makey Makey!

Felt Donut shapes:

Use a roll of tape to cut two circles on felt, and then cut a frosting shape out of another color. You can stuff and sew these together after sewing your circuit.

Sewing an LED:

Download the template if needed. To make a regular LED sewable, it's easiest to use needle-nose pliers to and shape the LED legs. We shape both legs differently so we can mind polarity when sewing. (An LED has to be wired right or it will not light up. You must power the long leg to the positive side of your battery and the negative side to the negative.)

We prefer to shape the longer leg (aka positive side) in a spiral and zig zag the short leg. This helps to visually know which side is which even when we've finished sewing the project!

Sewing Positive Connection:

Sew about 5-6 stitches on the edge of your donut, then sew a running stitch up to the LED leg. Sew your thread really close to the metal legs of the LED as this is how you are conducting electricity! Again, make those stitches tight so they make a good connection. Once you've sewn about 5-6 stitches on the LEG leg and secured it to the felt, flip your project over, tie a knot, and cut your thread to the knot.

Sewing Negative Connection:

Now do the same thing for the negative side! Make sure you are using a new thread to sew your negative connection. You can move your running stitch all over your donut, but make sure the negative trace NEVER TOUCHES or CROSSES the positive thread.

Connecting Power:

Once your LED is sewn, you can connect it to a battery power source, or connect the positive side to KEY OUT on your Makey Makey and the negative leg to the EARTH connection on your Makey Makey. See the pictures and template for clarity on this!

Step 3: Sew a Momentary Switch

Sewing a momentary switch is actually pretty easy! The great thing about the way you will build this, is that we are going to hide how it works from the top, but you can still share how a momentary switch works by flipping your donut over to see how the circuit is broken until you activate it.

Shaping the Donut:

Use a roll of tape to cut 2 pieces of brown felt for your donut base. Then cut your frosting top out of a nice sugary and contrasting color. We will sew the circuit on the donut base, so set the rest of the felt pieces and aside and grab your conductive thread.

About the Circuit:

To sew a momentary switch, you will need to break the circuit by having two touch points close together that do not touch. This switch is normally open, but will be closed when someone presses on the donut, because you will have conductive tape on the top layer of donut. This conductive tape on the top will bridge the circuit for a moment and then the circuit will be open again when you let go! (That's what makes this a normally open momentary switch!) The cool thing about this build is that it is the same way keys on your keyboard work! If you took apart your keyboard (or a calculator) you would see the same type of circuit on the board where the traces come awfully close together, but they don't touch. When you press on a key, there is a small conductive pad that will close the circuit by bridging those two touch points. Pretty cool, eh?

Sewing the Circuit:

Download the template if needed. Cut about an arm's length of thread and sew 5-6 stitches on the edge of your donut base, then sew a running stitch to the center of your donut. Make sure to sew small stitches and keep your thread tight. Loose stitches will lead to a short circuit. In the center, sew a 6-7 stitches close together to make a leaf or circle pattern and create a conductive touchpad. Flip your work over, thread your needle through a stitch, and tie a knot to secure your thread. Cut loose threads!

Repeat for the the other side.

Building a Bridge:

To bridge the circuit, you'll put a conductive pad on the top layer of donut. We used a small piece of conductive fabric tape, but you can also sew this conductive pad. To ensure connectivity with your sewn circuit, place the top layer of donut and mark where you need to create your "bridge." Once you've created it, hook up your Makey Makey and make sure placement works before sewing your donut together. (Hook one circuit trace to a key press and the other circuit trace to EARTH.)

Finishing the Donut:

If your circuit works, take a little stuffing to fluff up the outer edges of your donut and keep the bridge from connecting with the circuit traces. If you don't have stuffing, you can cut an extra donut piece from felt, but make sure to cut a hole so the tape can still connect with the circuit traces.

We put a little stuffing, and held it to the side by sewing some basting stitches with non-conductive thread. Place everything together and test your circuit again. Adjust away from your touchpads, and if your circuit works, put all the donut pieces together and sew the edges of donut together by sewing looping stitches from the top layer to the bottom and bringing your needle back to the top to sew to the back (Picture 7.) Repeat until your donut is sewn together!

In Picture 8, you can see that we sewed a running stitch around our button area, this is to keep the stuffing from accidentally fully insulating the conductive touch pads.

Frosting and Sprinkles:

Using a bright contrasting thread, you can sew sprinkles on your frosting and this will also hold the frosting to your donut. Just sew a stitch on the top of the frosting and make sure you only sew through to the top layer of donut. Sew a couple of stitches close together to make it look like a sugary sprinkle. Vary the angle of your stitches for an organic sprinkling effect.

A Little Explanation:

A switch is made by a break in the circuit. You can attach this and break either the negative or positive side to your LED, but for simplicity sake, it's easiest to attach this "break" to your negative trace. (Wonder why we keep using the word trace? In electronics you can see the circuit traces on a circuit board, and when sewing circuits or creating paper circuits, we emulate these circuit traces on PCBs or Printed Circuit Boards) A Makey Makey works in the same way. It breaks the circuit and is always open, until you touch a key press and an earth connection. We always recommend using your hands when you start with Makey Makey and then testing conductive items for playing with circuit ideas. For more on this, visit our Tinkering with Circuits guide.

Tips:

  • Conductive thread is sticky and knots easily.
  • Keep your thread as short as you can and sew tight stitches. It helps to hold the thread at the base after sewing a stitch.
  • With normal thread you can use a double thread for hand stitching, but with conductive thread you need to use a single thread. (A double thread is when you thread a needle and place your threads evenly at the base and tie a knot. For sewing with conductive thread, you need a single thread, which means you will thread your needle and leave a short tail and only knot only the long side of your thread. For more hand-sewing basics check out this Instructables class.)

Step 4: Tinker, Play, and Sew More!

Now that you've got a base of modules, hook them together with alligator clips and explore how to power an LED, break a circuit with a normally open momentary switch, and maybe start tinkering with ideas for creating your own normally closed switch. (What is that? And how could you sew one?)

Hooking LED to Battery Pack:

To hook your sewn LED to a battery, hook the positive side to the positive on a battery pack and the negative side to the negative of your battery. In Picture 1 we used a yellow alligator clip for the positive side and a grey alligator clip to indicate the ground or negative side.

Hooking Conductive Jelly Donut Switch to LED and Battery Pack:

To add your conductive jelly donut switch and disrupt the circuit, take the negative alligator clip and unhook it from the battery pack, hook it instead to the donut switch, and then from the other side of the donut hook another alligator clip to the negative side of the battery. This breaks the circuit until you press on the donut and close the circuit to send electrons to the LED! (Picture 3)

Hooking LED to Makey Makey:

To light your LED with Makey Makey, place a jumper wire in the back header where it indicates "KEY OUT." then alligator clip from this wire to the positive side of your LED. In picture 4 we used a yellow alligator clip to the positive side of the LED donut. Then hook an alligator clip from the negative side of the LED to an EARTH input on the Makey Makey. Using your hands, you can now press any key press to light up the LED.

Hooking LED and Conductive Jelly Donut Switch to Makey Makey:

If you want to light your LED donut with your jelly donut switch, just add your donut switch to any key press. One side should be clipped to a key (in picture 5 we hooked a yellow alligator clip to SPACE) and hook the other side of your donut to an EARTH input. (Remember the entire bottom strip is EARTH!) You can clip from the front or the back, either way, the Makey Makey will send the signal when you press on the donut!

Next Steps?

If you like this Instructables, look our for a second upcoming guide to help you learn to sew even more soft circuit blocks you can use with Makey Makey or power with a battery.

We love seeing your creations! So if you make this project, please share below!

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