Introduction: Lilypatch: Quick Laser Cut Soft Circuit Breakout
Rapidly make your Attinies sewable! The Lilypatch is a quick and easy way to get many of the advantages of Lilypad-style sewable arduinos without a lot of the cost or effort.
In short, it is a piece of felt, laminated with a piece of conductive lycra that is then laser-cut into a solder-free prototyping platform (with a built-in battery holder!). To build and use it just needs 3 steps:
- Glue felt to lycra and laser-cut
- Punch DIP socket into Lilypatch, bend pins and remove backing (no soldering)
- Flip over pads (if needed) and sew to attach to devices or clothing.
In this instructable, I'll go into a bit more depth to help guide you along, and also hopefully to get all your ideas about how to improve, what I hope could be a very useful "patch." This one is formatted to work specifically with Arduino ATTINY85's, but with advice from you people out there, we could make a whole ecosystems of cheap, simple circuit boards floating freely around the internet for other microcontrollers or electronics. I'm sure lots of people have made very similar things before, and can give all sorts of great feedback. This project was created with very specific needs in mind, but hopefully releasing this design out can help out others too!
Why was this created?
In my PhD research (digitalnaturalism.org), I go out to far out of the way places, like the jungles of Panama or Singapore/Malaysia, and try to teach workshops for creating digital devices to interact with animals in their natural environment. In some of my upcoming trips, I am hoping to actually run some hiking hackathons where we will be out in the woods living for several days or weeks. This poses many design challenges, primarily was how to do electronics out in environments without wall electricity or soldering irons. Soft-circuitry was a good choice, because we can just sew connections together, but for a not-well funded researcher like myself, buying and giving away a bunch of Lilypads can get really expensive. The Gemma is the cheapest sewable platform (http://www.adafruit.com/products/1222), but $8 +shipping, makes it still too expensive to not want to ask for them back from my participants. Also with a cheaper solution, I can build lots of different things and not have to worry about harvesting their boards later. This is what got me into using ATTinies in the first place (they are dirt cheap and do most the stuff I want, and they're the chip already in the Gemma). Their problem is that they can be hard to use without soldering them
Thus I wanted to re-create the capabilities of the Gemma but in a cheaper, more disposable way. So I set up the following design goals for myself:
- The price to beat is $8 for the Gemma, and Ideally I want to keep it around 1-2 dollars, letting me supply 50-100 people in workshops with a budget of just $100.
- The material cost of one of these lilypatches with an attiny in them is just around $1.00-$1.40 (felt, lycra, attiny, thread).
- I wanted to figure out a 1-step process to rapidly make something I could take and put together however I wanted out in the field.
- Manufacturing during a trip is fine (there’s plenty of time for tinkering late at night while camping, but anything that needs exotic tools like laser cutters should be taken care of previously).
- Another regard was that I wanted to use this to teach electronics, so by not making it too complicated, people could use it as a platform to learn some basics on.
- I wanted to limit myself to using only 1 non-conventional material. In this case this was the conductive lycra.
- I’ve gone through dozens of ideas trying to figure out how to do this, (eg. mix shapelock and wires, make conductive glue and run leads to conductive fabric, …etc).
- The pads can be sewn to, gator-clipped to, folded over and stapled together, or used as touch-pads themselves.
- The pads stick out so that they can be flipped over for sewing on either side when attached to a garment or other device.
- I went through all sorts of geometry problems figuring out balances between making good contacts, making the backing peel easily, determining how to lock the pin legs to the right leads, while also trying to balance how this thing could be used. This hybrid, flip-if-you-want method with a battery pouch seemed to be my best option (after lots of personal iterations!)
- This design is also left open to lots of simple techniques that could make it a lot more robust (like if you aren't in the jungle, use some hot glue to seal the connections better!), though these aren't 100% necessary for simple projects.
What can it be used for?
All kinds of stuff! In theory anything you can do with an Attiny85 (which is a lot!). For many projects at home or in the lab, you might want to do some good old soldering for really good firm connections, but if you want to get started on an idea quick, and especially with soft-circuits stuff anyway, this might be a good option for you.
Also if you need to do some projects but get sick of sitting at the soldering iron, this can be a kind of fun activity, sewing together these different parts, that you can do while watching a movie or something.
I give three examples at the end of this instructable, a simple flashing costume, a plush, light-up cell model, and a device for monitoring where your pet tortoise may have run off to!
Help and Inspirations
Tom Jenkins, an awesome auteur of tinkering platforms (http://thomasjenkins.net/), helped me think thought this thing a lot
HOWTOGETWHATYOUWANT (http://www.kobakant.at/DIY/), as with most things soft-circuitry-related, the folks over at kobakant have compiled many great resources and ideas. For instance, the idea of making a conductive battery pouch like this comes straight from them: http://www.kobakant.at/DIY/?p=4432
Update: I just saw this other similar project they have http://www.kobakant.at/DIY/?p=2672 where they make a breakout board from laser cut fabric, but they also use somewhat specialized things like fabric fusing and pourable acrylic or soldering. This design I'm presenting here hopes to accomplish a very similar goal (in perhaps not as robust ways) with more limited materials.
Step 1: Materials
8 Pin DIP socket
Conductive Lycra (Stretch Conductive Fabric)
$4 /sqfoot http://www.lessemf.com/fabric.html
[just a lil bit] you don't need much to put this together. Here's the kind I use, doesn't kink that much: http://www.amazon.com/gp/product/B00C9NVUY6/ref=wm...
$4 http://www.amazon.com/3M-General-Purpose-45-Adhesi... (I actually used 3M 77, does it actually matter?)
Optional, but helpful
Needle Nose Pliers
Step 2: Spray-mount Conductive Lycra and Felt
Bonding a conductive surface to a non-conductive surface is a really handy technique in lots of electronics. In soft circuitry people do a lot of fusing, using a fusible interfacing that you can iron two items together. This creates a pretty solid bond.
For this project, I wanted a selectively permanent bond. Some parts should stay in place on the felt, and other parts (like the backing that we pull away), should pull off easily.
The solution I came up with was spray adhesive.
Lay down your felt on top of some paper (or anything else you don't mind getting sticky spray splash). Give it a quick, light mist.
Lightly, evenly set your Lycra on top of the sticky felt. Move from the middle outwards with you hands and smooth the Lycra on to the felt, avoiding any wrinkling. (this should feel really satisfying when you get it really smooth, and is not that hard to do). Finally put some more scratch paper on top and then cover it with some heavy books to press the whole thing together for 5 minutes while it dries.
This bond is pretty durable, while still being easily peel-able with just your fingers! At the end, you should secure (e.g. by sewing) any parts you are using.
Step 3: Cut Out the Fabric PCB
Get the most up to date layout from our github: https://github.com/Comingle/Comingle_Open_Docs/blo...
Load in to laser cutter, lycra-side up.
The goal of cutting the felt/lycra sandwhich is that the cuts will cleanly go through the lycra, but not all the way through the felt. The only cuts to go through everything will be the outer-most cuts to chop out the entire patch, and the through-holes.
with my Full-spectrum Gen 5 i used the following settings:
Regular cuts = 100%speed 30% power
Outer cuts and through-holes = 100% speed 40% power 2 passes
Step 4: Lock in DIP Socket
I use a socket so that I can pop my Attiny chips in and out if i need to re-program. Many other people are always just smashing and soldering straight to those poor things!
Take your DIP socket, and put it through the holes on the felt-only side of the patch.
Make sure they go through their corresponding holes and are lined up with the conductive traces.
HERE'S THE TRICKIEST PART OF THE WHOLE THING (not that bad)
Now, with your finger bend the pins OUTWARD. Do one side at a time, and hold the middle of the patch firmly in place (so that the pad doesn't slide out). Press down on a table to flatten these leads. Finally roll the socket hard, side to side, on the table to bend the pins up around the edges. This will lock the socket and metal pins firmly in place.
Step 5: Pull Off Backing
This took some effort to calibrate the design between getting nice fat leads, and making sure that connections we don't want are easily removed.
Take your fingers or some pliers and pull off all the backing materials.
This is probably a good time to take a multimeter and see if you have any shorts. If so, pull off the lycra that's causing you problems. I've been printing them recently with no problems!
Step 6: Form the Battery Pouch
First we make the negative terminal. This is just a spot that sits on the bottom of a coin cell battery. Take some conductive thread, stab through the negative terminal lead, and tie a fat little knot on the felt-only side. For best contact, tie this knot over a little bit of the conductive lycra you pulled off. This worked the best for me!
Next peel off a bit of the battery pouch, almost up to the narrow part, and cut off the felt. Now flip it up to the felt only side, and sew it down with NON-CONDUCTIVE THREAD. Make sure not to make it contact the negative side directly. It should be centered over the fat little knot you made earlier.
Now you should be able to slide a battery in and it automatically routes to power your ATTINY.
Go ahead and give it a test with some gator clips or just an LED on some leads and see that everything is functioning.
Step 7: Attach It to Things
You can sew, staple, velcro, or glue the whole patch onto other materials, and use conductive thread to run lines out to sensors or outputs like speakers or lights or servos.
If you are attaching it flat to something, fold the pads back so you can sew through them and knot the conductive thread on the conductive pads.
These work really well with gator clips too!
Step 8: Sample Projects!
Here's 3 quick example projects I whipped together to show off what it can do.
Tortoise Tracker Digital
(instructable coming soon) As my standard "Hello World" to prove to myself that the device works, I made a little device for keeping track of my pet tortoise! I like to let her run around outside and in the home, but she can be very sneaky, and climb away or hide and I could lose her or someone could accidentally step on her. I have made analogue ways of dealing with this problem in the past https://www.instructables.com/id/Tortoise-Tracker-... but I wanted to see if I could whip something up in just 10 minutes with my new Lilypatch!
I just plugged a piezo into one of the leads and the ground (note how I stack the pads using the felt to insulate and prevent shorts), and an LED into the other lead and ground. Now while she walks around I see and hear a little alert beacon. It's fun and was running for at least an hour until I stopped it myself (need to program the beeping to be not as annoying.)
For another example, look you can use it in human-costumes too. Here's some lights added to a set of sparkly wings.
Plush Light Up Cell Diagram
(Instructable coming soon) I have an awesome sister who teaches biology (and also has the number 1 rap song about Cells on the internet). I made her some plush plant and animal cells to use in class, complete with Light-up SMD LED mitochondria! I tried out an early version of the lilypatch on this and it worked pretty good!
Step 9: Iterations
It took a lot of iterations to get a patch that solved a lot of my problems and that could work reliably.
Here's some pics from past iterations to show you how my thinking evolved.
I can also make some statements about my design decisions:
The thickness and squishiness of the felt gives a tensions to the connections and knots made to give really good contact even without gluing or anything.
The thickness of the felt also prevents the cuts that separate the lycra from going all the way through the backing material, so the whole thing stays together even though the leads are separate!
From my experience, electrical shorts came from areas where two cuts were made but the cuts were not far enough apart for the bits of fabric to peel away easily, or the cuts were not close enough to obliterate this material. I tuned my design to try to do this.
It always feels like a hack when you try to power your devices, so i wanted to incorporate this into the design. The way this thing folds over though, and the way the battery goes on is the part where I think there could be the most improvement in future designs.