2010-12-18
TRON Backpack
With TRON Legacy now out and being a fan of the original 1982 TRON movie I had a sudden dorky desire to trim my backpack with electroluminescent glowy goodness. Usually I let such ideas slip, but I made the mistake of mentioning it on Twitter, and well - it is all Jeri Ellsworth's fault, she encouraged me!
Implementation wise there is not a lot to say. In last year's after-Christmas sales big-W was selling off unsold EL-wire decoration units for about $3 each - a bargain I just couldn't let go. I've been looking for a project to make use of the bag full of them ever since.
Each came as a ice-blue 3 metre length of EL wire inside a PVC coloured cladding, powered by a 3 volt (2 AA cell) inverter delivering about several hundred volts pk-pk at a few kHz into the EL wire capacitance.
I used about 5 metres of the EL wire for the project; one three metre length to profile the body of the bag. A shorter length for the shoulder straps, and a another stripped bare length for the detail on the back. The separate pieces are simply wired together using a pair from rainbow data cable - probably technically not rated to the voltage, but hey it's only me going to get shocked if it fails... A single stock inverter was used to drive the full length, there is plenty of capacity to drive longer lengths with a single unit, maybe at the cost of a little brightness. The inverter sits in a pocket inside the bag, you just open the zip (or squeeze the button through the fabric) to turn it on and off. The inverter pulls a lot of current, and the 2 AA cells won't last too long - that said I am still on my first pair of alkalines, when they die I will probably install a pair (or three) of D cells.
The high-quality rip-stop nylon material of the bag required use of a large needle and thimble for the tailoring part of the project, in fact I used pliers to pull the needle through quite often. A mixture of black nylon thread and fine "tiger tail" black braided stainless steel jewellery wire was used to hold the EL wire rope in place. Some fine black heat-shrink tubing was used to insulate the terminations and free-ends of the wire, and to black-out a couple of sections on the detailed back section. It took hours to complete (about 8 to be precise) and wasn't very nice on the hands - this is not an easy project physically, but quite trivial electrically...
The end-result looks awesome in the dark though - totally worth the effort. TRON Legacy and New Years Eve here I come!
After using it for two days now I need to touch-up the stitching on the shoulder straps and perhaps look at a few more stitches on the annular design on the back. It is very difficult to keep it symmetric on a moving fabric surface. I was silly enough to do this to my favourite "every-day" backpack, so it will have to bear the abuse of my daily commute to work and back for some time yet.
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