Building with E-Textiles, Part 2

Last week, I spent an afternoon diving into the wonderful world of e-textiles. That is to say that I spent several hours sewing electrical components into a garment in an attempt to learn something new about both textiles and interactive consumer electronics. What I discovered was a surprisingly vast industry poised to explode in popularity and market share in the next few years. The unique engineering challenges presented by wearable electronics represent a significant barrier to entry for any company seeking to break into this largely untapped market. That means those who do have the design expertise and engineering capability can fairly easily start to work with off-the-shelf components to build interesting new products. You know those shoes kids wear that have a little light that flashes every time they take a step? That’s just the beginning. Soon, you’ll start to see jeans with lights along the length of each leg. It starts with a little light. Then, it evolves into complex sequences of light pulses, and suddenly kids are using their clothes to communicate in an entirely new way.

So that’s all interesting and terrifying, but you’re really here for details on the light dancing gloves we’re making. Where do I begin? Ah, yes. Where part one ends, we had the light cluster sewn (installed?) in the right glove. Once I had a feel for the sewing, it was simply a matter of placing each component to minimize thread length. We were quite fortunate that the rest of the components fell naturally into place. With one exception, there are no crossing threads in the entire design. That is to say that there is only one point in the circuit layout where one trace must cross over another without intersecting it. Textiles make this a bit easier, since there are two sides of every fabric. Pass one thread over the other by punching through the fabric and running across the back side. This relies on the fabric to act as a suitable insulator between the two threads. We recommend avoiding designs that involve this sort of thing. It leads to complications and opportunity for substantial maintenance overhead in the event two threads make contact.

We were doubly fortunate, in that no one was wearing our finished glove when I melted a small section of polyester glove material while running a test. That would likely have resulted in a nasty burn. The material I melted was also coincidentally the only thing preventing the supply voltage from contacting the ground and shorting out the system. I was able to identify the problem and disconnect the power before that could happen, so no major harm done. Forensic analysis suggests the resistance of the circuit powering the lights is very low, resulting in excessive current through the common ground. We’ll be modifying the design to add a decorative (current-limiting) resistor between their common ground and the actual ground. This will prevent future melting, burning, cursing, and ancillary drama. The point is to have fun, not to learn triage techniques for 2nd degree burns. That will most likely happen tomorrow, as soon as I can find a suitable resistor to wire in.

Today, I bought a second pair of gloves to make a glove for myself. I’m calling this one the mark 2. After perusing the Home Depot utility glove section, I settled on Gorilla Grip. They are all black, except a little silver around the wrist. The XL fit me snugly, which was a surprise, as I expected a M or possibly L. These are interesting gloves. They feel like rubber, but they are 100% nylon. They’re very flexible, which makes the sewing much easier. I was able to sew all the components into the mark 2 gloves in about 3hrs, whereas the mark 1 gloves took almost 12hrs. To be fair, the mark 2 does have a simpler design with all the components on the back of the glove. Mostly, though, the reduced build time is largely due to complete lack of design and sewing proficiency for the mark 1. Now that I know more about the rules of this design medium, I’m already improving on the design.

Here’s a photo stream of the process: https://www.icloud.com/photostream/#A15oqs3qSqdIy

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