Intro: USB Stretchy Fabric Connection
Make a stretchy fabric USB cable for whatever reason you like. This was a first test for me and... it worked! So the next step will be to integrate this USB connection into a shirt that I can wear, with a pocket for my digital camera, containing a USB connection that connects to the end of one of a sleeve, so that I can plug right into my laptop to download my pictures (see sketch).
This Instructable will cover the basic principle of how to make the stretchy fabric connection and isolate it. Though I take no responsibility for what might go wrong.
Step 1: Materials and Tools
- Stretch conductive fabric from www.lessemf.com
(also see http://cnmat.berkeley.edu/resource/stretch_conductive_fabric)
- Fusible interfacing from local fabric store or
(also see www.shoppellon.com)
- Conductive thread from www.sparkfun.com
(also see http://cnmat.berkeley.edu/resource/conductive_thread)
- A USB cable from your excess of USB cables lying around or from any local electronics store
- Stretch fabric (cotton jersey or similar) from local fabric store or old clothing item
- Regular sewing thread from local fabric store
- Aleene's stretchable fabric glue from www.amazon.com
- Baby powder from local drugstore
- Fabric scissors
- Sewing needle
- Soldering iron and solder
- Wire clippers
- Wire strippers
- Stanley knife
Step 2: Stripping the Wires
Cut both ends of your USB cable off leaving about 2-3 cm space (plus some extra for mistakes). I actually donÃ¢â¬â¢t know why I did not strip my cable close to the plug on both ends, so now I still have a long piece of wire at one end. Which I actually donÃ¢â¬â¢t want, but am too lazy to un-sew and re-solder and re-sew.
Once you have cut the wires, strip the wires (see picture). Another thing I didnÃ¢â¬â¢t do, which would be a good idea, is to actually solder a wire to the ground (isolation) and also make a stretch conductive connection for this (IÃ¢â¬â¢ll include this in future versions).
Once the wires have been stripped, make little loops as the end of each wire and using a bit of solder, fixate these so that they are closed circles.
Step 3: Ironing Conductive Traces
Fuse (iron-on) some interfacing to a strip of stretch conductive fabric. Cut this strip into 5mm thin strips. Enough so that you have 4x (or 5x, including ground) the length of the connection you want to make, in my case 30cm long, although I'm not sure if the resistance over a longer distance will effect the USB connection and it might not work. Will also try out in future versions.
Lay out your piece of regular stretch fabric on an ironing board or other good ironing surface. Iron it flat, and then fuse (iron-on) your conductive strips so that they go from one end to the other with about 5mm spacing in between.
The resistance for a 5mm thin strip over 30 cm seems to be about 60 Ohm. You can actually about half the resistance by making the strip twice as wide (1cm).
Step 4: Sewing
Thread a needle with conductive thread and take it double. Sew the loops that you soldered to the end of the USB wires to the conductive strips. Make at least 3-4 stitches connecting the two. For the first side it does not matter which colour wire connects to which strip. But for the second side you definitely want to MAKE SURE that all the colours match up (green to green, red to red... whatever colour wires your USB cable contains).
Step 5: Insulating
Now that everything is in place we want to isolate the individual stretch conductive strips from one another so that, should the fabric fold, no short circuit or signal disturbance is caused. You can surely try other methods, but IÃ¢â¬â¢ve found AleeneÃ¢â¬â¢s stretch fabric glue to work best for me as it does not affect the conductivity much or at all.
You can either isolate each trace individually or, as I ended up doing, you can spread a thin layer over all of the traces and spaces using a piece of cardboard to spread the glue after first applying it evenly.
You will also want to isolate the conductive stitches on the back of your fabric!
NOW you will have to wait a whole day for it to dry. So better to just leave it and come back to it the next day.
Step 6: Baby Powder
NEXT DAY you will find that the isolation, though set, is still sticky, or at least it likes to stick to itself. An easy solution to this (if it bothers you) is to sprinkle some baby powder on top and rub it in. Then shake it out the window. It smells very intense, almost awful.
You can check the resistance and it should not have changed at all, or only very little. In my case it even improved (or I measured a different trace the second time round).
Step 7: Plugging In
Now that everything is isolated (best check with a multimeter that you have no cross connections) you are ready to plug in a USB device that fits the type of USB connection you selected.
In my case I chose a regular to small USB connection that I normally use for my digital camera, to download images. And it worked!
First of all I downloaded all of the pictures for this Instructable using a non-tampered-with USB cable. And then I took a random picture of my wall and plugged in my stretch fabric USB connection and then my camera and all worked. But I have no proof that things aren't going wrong at the same time. So please do this at your own risk.
But have fun doing it.
Pictures of this last step were taken using a different camera, since my camera can not take pictures of itself. So these will be uploaded shortly.
Step 8: One Last Thing
If you want you can sew the fabric together and turn it inside out. this makes everything a bit more compact and better looking (see pictures).