Glitch and the LED sneakers – The Parts

First things first… what’s the final design going to look like? My plan was for 4 LEDs along the outside edge of each shoe – 2 red and 2 yellow to match the colours of the Glitch shoes. Then run wires up inside each leg of my jeans to the Lilypad and power supply mounted around my waist. Add a button to allow switching between different flashing modes and some connectors at the ankle and waist to allow things to be detached and we’re set.

So what hardware are we going to need?

We’ll need:
the components

  • a Lilypad Arduino – the programmable microcontroller that drives everything. It’s got 14 digital I/O pins that can drive LEDs directly
  • a power supply – this lovely little board takes a single 1.5v AAA cell and steps it up to 5v to drive the Lilypad. However I think I’d power it differently if I was doing things over again
  • a cable to connect it to a computer for programming. This is USB at one end and serial at the other with a connector that plugs directly onto the Lilypad for downloading programs, communication back to the computer and power
  • 8 LEDs – I used LEDs specifically designed to complement Lilypad
  • a button for changing modes – again this is specifically designed for the Lilypad line, although I ended up not using it in the final design
  • lots of wire & connectors

For wiring, I need a signal line for each LED down each leg, plus a common 0v line – so 5 wires per leg. I visited Lee’s Electronics on Main Street in Vancouver for parts (they’ve got loads of Arduino items but if you’re not local then SparkFun are a great online source for everything Arduino) and I took the brave decision to explain to the assistant exactly what I was planning to do with this hardware, rather than just swan in and give him my parts list. He was really helpful and suggested ribbon wire for the wiring. This was a smart move as it’s cheap, low bulk and meant I could use insulation displacement connectors for one half of each connector, eliminating half the fiddly wiring. It also looks cool if you’re into the whole ‘visible electronics’ thing. If you’re into e-textiles then you can actually buy electrically conductive thread and sew your circuit into your clothes. Pretty amazing but I was just looking for a temporary solution and I didn’t fancy the idea of sewing 5 lines down each pant leg.

I bought 9 foot of 10-way ribbon cable which, even allowing for lots of slack in the system, turned out to be about 2 foot too much (but I knew I was buying too much: it’s like haircuts… it’s much easier to take off a little more at the end than it is to add some back on). Another great thing with the ribbon cable: you can just tear it up the middle and suddenly, with no extra work, you’ve got a cable that’s 10-way at one end and splits into two 5-way cables at the other end!

One downside of the insulation displacement connectors is that the male side of the connector is usually soldered into a circuit board. Nobody ever uses them for in-line connectors (as I was trying to do) so the only option I had for the male connector was a PCB mount variant with exposed pins on the back side. This makes for rather fiddly soldering and a connector that’s far from ideal for wearing, so I added a length of heat-shrink tubing to my basket.

And finally, I also bought a pack of crocodile clip test leads for prototyping. I knew I had a set at home somewhere but you can never have enough crocodile clip leads – and actually, even having found the second set I had at home, I didn’t have enough leads to fully wire-up the 8 LED design with crocodile leads.

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