Introduction: World's Thinnest Programmable Leather Bracelet!
I've already found a whole bunch of uses for the bracelet: it makes me visible during night bike rides on the way home; it makes an awesome raver strobelight (I have a special accelerometer built into mine); I can set it to count down how many minutes I have left during a presentation; it reminds me to move my car after two hours so I don't get a parking ticket ; and it makes a handy flashlight in a pinch.
And the really cool thing is, if I need to change its behavior, I can do so really quickly and easily whether I'm on the desktop, handheld or phone. I write and upload programs directly from a web-browser, and a scheme interpreter flashes a part of the screen like morse code, which is read by button-schemer. This way I don't need special software or any extra hardware. Because of its built-in light sensor, it can also respond to other lights in the environment, or - get this - program another bracelet!
As we all know, one recurring problem with wearable electronics is how do you program it if you don't want to bring your whole development system and hardware with you? How tiny can it be if it contains extra hardware to talk with your computer? Another problem is the need for bulky battery holders. Read this tutorial to see some of our solutions to these issues.
To make your own, you'll need our kit (it's the tiniest you'll find anywhere), but this tutorial has a ton of ideas about making your own wearable electronics. For instance, designers should aim for ultra simple wiring, perhaps making a system bus so that end-users would need only two wires throughout their garment. Right now, even simple computational projects need a lot of different stitches (which must not cross). This project also hints towards the future of mixing craft with programming, so it's worth reading even if it's just to gain insights for your own unique projects.
Step 1: Preparation
First, a few words about the button-schemer system.
It's designed to be very easy to hookup but it's picky about what it's connected to.
- The two holes on either side of the button-schemer connect to lightboards and switches only, and you can use more of both in your design, for some kinda weird bike-wheel-flashing-light project.
- It has a voltage booster to make the lights bright on a CR2016 battery, and it runs until all the juice is gone.
- The switch has a 1K resistor. This is because lightboards and switches use the same line. Take note if you plan to use your own switch.
Ingredients (all from Aniomagic Store: http://www.aniomagic.com/store )
- button schemer
- 4 lightboards
- 1 button switch
- pre-cut piece of leather
- matching brass snaps
- conductive thread
- thin battery (CR2016)
- adhesive-backed liners.
Everything listed here comes in a kit, and the leather strap has the snaps already attached. We've also laser cut holes in the strap because leather can be tough to sew through, and it strips conductive thread, reducing its conductivity.
Step 2: Building - This Takes Less Than 20 Minutes.
Remember to test your circuits often as you build, to minimize the cost of errors. The button-schemer comes pre-programmed with a "heartbeat" pattern that turns on all 5 lights in succession.
That said, sew down the + and - holes, leaving about 3 inches each to make into a "battery holder." Quickly use a bit of tape to connect the two strands of thread to the battery. You should see a flashing pattern. This must work before moving on.
Step 3: Lights on Left
Next, sew on the lightboards left of the button schemer.
Tip: tape down the previous thread so it doesn't get in the way or fray.
Use two separate stitches. It's important for the lightboards to be oriented like this: the one closer to button-schemer has the plus facing up, the other facing down. To test, connect to the battery as before, you should see pattern start at the schemer, then move left.
Step 4: Lights on Right (and Switch)
Now connect the lightboards right of the button-schemer, as well as the switch. (you could also put the switch on the left too, or leave it off entirely). You could also experiment with a tilt switch or some other sensor. Remember the switch needs a 1K resistor or else it will short out the electronics (or not be sensed correctly).
Step 5: Making the Battery Holder
One major goal is to keep the bracelet thin, so any type of traditional battery holder would be way too thick for us. We use a bit of adhesive-backed liners to make really thin, yet sturdy battery holder.
Peel off the paper backing from the liner. With the sticky side facing up, pass the minus conductive thread through the hole, fold the liner and press it to the leather. Then wind the thread on the adhesive side into a small coil. Place the battery down, minus side down, and press it until you feel it make good contact with the thread. It should stay stuck.
Then, make a slightly larger coil with the plus conductive thread on the small disc, sticky side up.
Press it unto the battery. Push the thread into the tiny notch so it doesn't stick out.
Step 6: Finishing Up...
Seal the back with the longest adhesive liner.
The world's thinnest, programmable bracelet.
And how do you program it? Heh heh, that's the real icing on this cake: head on over to
http://www.aniomagic.com/schemer and play with the web-based interface.
Why not USB or bluetooth? Hah! Where are you going to fit all that? If someone has a source for USB or bluetooth chips that fit on an SOT-23-6 footprint, I'd love to hear about it.