Clipper card modding
San Francisco’s BART, Muni, and Caltrain public transport systems all take the Clipper card. So of course, when I was with a small group earlier this week, three of us simultaneously declared our desire to mod them into jewelry. It turns out that you can’t just cut the chip out; the card includes a wrap-around copper antenna coil.
I nosed around and found that people have used acetone to dissolve the adhesive in London’s Oyster card, so I tried this on a spare card. Thirteen hours later, finding it largely unchanged, I found another person’s Clipper adventure and learned that this is normal: the modern Clipper card is stalwartly reinforced. But acetone still helps!
Upon examination, the soaked card had a matte finish (as opposed to its original shiny veneer), and the edges were swollen.
The lamination had been weakened, and could now be scratched through with a fingernail. It peeled off easily (and satisfyingly!) in a single piece.
I started on the white side. Here, the next layer also peeled back with relative ease, though it sometimes wanted to fragment into sub-layers. Underneath lay the chip and coils, firmly embedded into a single, thick layer in the middle. There’s no harm in picking off bits of the covering that get stuck; you won’t damage the card’s innards that way (unless you REALLY go at it or use something other than a fingernail).
The blue side was easier; the outer layer wasn’t as tough, and came away as a single sheet. Underneath was printed a cryptic “6.8″:
According to Nima, the card uses a radio frequency of 13.56 MHz, so my only hypothesis regarding this number is shot. Any thoughts?
The soaked edge was soft and broke away easily, but the rest of the central layer was more durable. Still, it flexed easily and could be cut with a small razor. I tried a duller knife first and accidentally scored across the wires in one place, but it didn’t seem to damage anything.
The good news: The card worked! Also, if you want to punch a hole through your Clipper card, you can. Just avoid the edges, and give that chip-indentation a wide berth.
The bad/good news: After cutting the card down this far for testing, I was toying with it while walking around today, and of course I dropped it. However, I’ve got a new one, and am attempting to cut it down without the acetone bath – using the measurements I made from the old one, as well as referencing the photos I took for more precise calculations. Wish me luck!
Now, in case you’re curious:
- Card dimensions: 2.125″ x 3.375″ (2 1/8″ x 3 3/8″)
- To avoid coils, cut ≥1/4″ in from edge, most of the way around.
- To avoid chip and inner antenna, cut 7/8″ from that side of the card.
I also have an Oyster card (London) and a tarjeta Bip! (Santiago), so it could be cool to make a matched set of patches or whatever to stick to my bag for different cities. Bracelets would also be great, though I don’t tend to wear them, and they’re hard to make one-size-fits-all, as I may end up selling these. Patches definitely seem like the way to go – especially as I’ll be making those soon anyway — easily swappable depending on your current location. So, if you have a transit card from any city besides SF, please consider sending it to me, and I’ll send you something in return! (Stone carving? Prototype hologram? Other?)
•••••
Other current projects:
- Making a 3D-image-to-”hologram” system, after Bill Beaty’s method, with folks from Noisebridge
- Learning shorthand (because I’m trying to lucid dream again, but I usually stop journaling when it takes me ≥ 1 hour to write down my dreams… like this morning)
- Downloading XCode as I write this, to get the iOS SDK and start developing basic iPhone apps! (I have a list of four to start with… mmmmmm.)
- As soon as I have a stable place to live again, making some fricking patches for my IndieGoGo perks.
October 24, 2011 5:34 am 1 Comment
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breadboard dreams » Wearable transit card — February 21, 2012 @ 6:33 pm
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