A Smarter SmarTrip
I’ve lived in DC for long enough to be tired of the poor implementation of the SmarTrip system for our lovely Metro system. Don’t get me wrong I love having a contactless RFID and can’t imagine a paper ticket MetroBus/MetroRail system, but frankly I’ve grown to loath these SmarTrip cards because they break or get lost. It’s a pain in the ass to report it stolen, transfer the credits of your old card or SmartBenefits to a new card, and get it to you in a timely way. I haven’t yet figured out why they don’t have a kiosk at every Metro Station and major bus stations which is tied to a phone number, pin, and/or a credit card which will immediately process a lost/stolen report and spit out a new card attached with your balance.
Actually I lied, I have figured it out, I read this Office of the Inspector General report on the SmarTrip system and it reads like horror story of lowest bidder bureaucratic ineptitude. They built the system from the top down, just like NASA and the space shuttle, which is why it took 3 years past the contracted Roll-out date and an extra 3.8 million dollars. It’s also a hodge podge of contractors with dependancies which may be typical, but was the reason for the failure (Inter-contractor communication that is). The companion Final Audit Report completes the story and is somewhat upbeat about what they’ve learned from these failures. They are at least trying to learn from this, although I must say that based on my contintuing study of Organizational Management, I am not reassured. Needless to say I think my kiosk idea is not likely to hit the streets anytime soon.
The point of this page is that I’m trying to do something about this SmarTrip card design failure. Several people have dissected the SmarTrip card. There has been talk about creating “Smart Clothing” and given this is just a contactless RFID, it doesn’t look like it’s that big of an issue. Except the antenna isn’t as easy as coiling it, soldering it, and sewing it. Tom at the DCist was the only one who managed to get one to work, but he did not get a keychain sized device to work. His first attempt was an uncoiled wire with heat shrunk tube attached to the chip, which worked but was ungainly. His second which was coiled was unreliable.
I tried his second version with unheat shrunk magnetic coil from RadioShack and it failed entirely. I realized in playing around with this that the frequency was extremely confusing to people. Many thought it ran at 2.4 GHz in the unlicensed frequencies, but I found out through more research that it’s a 13.56 MHz system as well as that it’s a 3DES encrypted device using the ISO 14443 proximity card standard in the ISO 7810 form factor (credit card size format). As of yet no one has broken the security of the chip, although they have broken the system the Oyster Card uses which is similar in format, frequency, and standards. (The encryption standard is not set in the ISO protocol so each RFID manufacturer uses different chip layouts. So although in theory a similar method could be used to attack the SmarTrip chip, I’m unsure of how likely it is.)
As of right now I do not have a viable SmarTrip keychain key fob. Rather then trying to do the math on the antenna frequency resonation and then trying to figure how coiling might effect it, my next path is to try dissecting this key fob from Trossen Robotics and try transplanting a SmarTrip chip into it. If it works, I’ll post photos and a step by step how to up here (or on the HacDc Wiki) so others in DC can stop breaking SmarTrip cards and perhaps even create SmarTrip clothing. Speaking of which Trossen has this sticker backed Clear Thin Lamination Disk built for the same 13.56 MHz frequency which, if the transplant is successful, should make creating Smart Clothing a snap.
Feel free to email me or post a comment here if you have thoughts or more info.
UPDATE: Jan 23 2008
I received the RFID key ring chips from Trossen a few days ago (Saturday I think, but the Inaguration had me distracted). I have managed to destroy one of them in dissecting it (I bought five). I managed to pull apart another one without destroying it completely. The chip itself is similar in size to a Smartrip, which is to be expected. The chip and antenna are encased in a resin, so I’m going to drop it in acetone and see if I can’t get a better look at it. I’m hopeful with this transplanting plan as it looks like this might be fairly easy to acomplish, assuming I can solder worth a damn. I’ve got picture that I’ll put up this weekend.
UPDATE: Jan 25 2008
I’ve spent a good portion of the last two days working on this. I now have 2 key ring key fob chips that are left untouched, 1 that is likely in working order, and 2 that are damaged beyond repair during extraction/dissection. The video below is a play list of the timelapse that I’m taking of the continuing work I’ve been doing. It illustrates the initial dissection using a drill (tl01) with the first key ring. tl02 show’s the third dissection of the resin encased antenna, or the attempt at it (along with some clean-up) tl03-1 show’s one of the RFID chips dissolving in acetone within a jar (24 fps showing just under 11 hours worth of progression). tl03-2 is me trying to strip the resin off the antenna and remount/solder the SmarTrip chip into this antenna while another antenna and chip continues to dissolve. I tried to use the broken ones to count the number of wire wraps for future reference, however this required stripping the resin off and peeling the wire back through the remain resin which didn’t work to well. This antenna wire is a really light gauge of copper so I had trouble using enough torque to pull it through the resin, but not enough to break the copper. Further the acetone, although it took the outer plastic shells apart rather well (turning it into mush) and part of the resin too, the chip itself seem to be placed in a different epoxy resin which was only slightly weaked by the acetone. tl04 show me try to deal with the mush aftermath of an antenna, and again trying to count the strands in one of the antennas, followed by resin stripping, desoldering, and soldering a smartrip chip into this antenna (while I chase it around). I also did try and measure the diameter of the antenna wrap, but was none to accurate (fractions of an inch just confuse me and make me wonder why imperialism is assocated with an archain system rather then something like metric). I did find out (as you’ll see in a later timelapse) that the antenna from the Trossen key fob keychain is 22-23 cm in diameter wrapped 12 times (or about 69-72cm). I am going to dissect another one and count it too just to confirm.
Apparently impedance matters the most in this case. As I understand it this is a very low impedance antenna, but I’m not sure how exactly this works math wise. I’m still trying to find someone who knows more about this who can help me put this together.
I might add that the attempt above at transplanting failed when I took it to the Columbia Height Station. I had another SmarTrip card with me which did work. I did take a quick 30sec video of the normal one working and the transplant failing, but I haven’t put it up yet.
Right now it looks as if it’s back to the drawing board…