UPDATE 9/11/2008: Look ma! We have a whole website for the Speed-Vest now — you can sign up for news about the V2 vest, get yer press-blurbs on,

and stay informed about the 2009 Tour De Speed-Vest!

Furthermore, we’ve now got video of the vest in action here.

But if you’re looking for some fairly nerdy reading about how to make one of these yourself … read on!

The SPEED-VEST is a bicycle safety device and advocacy tool which displays the wearer’s current speed on their back in easy-to-read lighted numerals. It improves rider conspicuity while legitimizing bicycle speeds on the roadway. Originally conceived by Brady Clark and engineered by Mykle Hansen, it just won the Hub Bike Shop’s Bike Gadget Contest in Minneapolis, MN.

The system consists of a wheel speed sensor, a wearable numeric display and a small computer that does the thinking. The computer is an Arduino: an open-source embedded computing platform powered by an Amtel microcontroller. It runs for 6 hours on a 9 volt battery, and is about this big:

The numeric display is made from electro-luminescent wire, supplied to us by CooLight.com. El-wire glows brightly when supplied with a very small amount of high voltage, high-frequency current. It’s cheap, flexible and fairly durable. One AA battery can power the SpeedVest display for up to 6 hours.

This project was my first foray into microcontrollers. Not knowing much about electronics, I imitated this circuit closely; however the Arduino platform, suggested by the members of Dorkbot PDX, was much easier to use than I had imagined and quickly became my new favorite computer.

I wouldn’t call the project arduous, but the most time-consuming aspect was probably soldering the circuit together on the Arduino’s prototyping daughterboard. Next time, I’m going to learn how to make my own printed circuit board.

Meanwhile, Brady designed a template for the el-wire digits, based on the digits in old Nixie tubes. It seemed appropriate — it’s almost the same technology, really. Since I had 12 pins to play with, and since you can only overlap so much el-wire, we put five digits on the right and seven on the left:

We mounted the el-wire on a piece of black denim, taping on the template as a guide, using a technology the Coollight.com folks hipped us to: the Buttoneer. I don’t know how well it works for re-attaching buttons, but it’s great for this.

We achieved sharp corners by running the wire behind the denim through a hole, and then back through to the front at another angle.

In order to display the SpeedVest for judging at the Gadget contest, we needed a mannequin. So, we borrowed another great piece of Internet advice. Witness below the birth of the creature known as “Packing Tape Brady”, made possible through the assistance of super-assistant Heather Anderson:

We were up most of the night before the event deadline: debugging code, writing up handouts, fixing bad solder, screen-printing text onto reflective backing, velcro-ing everything together, and arguing about the relative artistic worth of the digits zero and seven. The next morning, we got it all together and brought it to the Bell Museum with about 15 minutes to spare.

(Somehow we neglected to get a picture of it working — but it worked!)

Despite some excellent other entries (including the zoobombariffic Superman Bike!), we were tickled pink when the judges at the Bike-In presented Brady and myself with a $150 gift certificate from the sponsoring bike shop, the HUB bike co-op of Minneapolis. And what a gift certificate! This beautiful hand-drawn check would have been prize enough, even if it hadn’t been financially negotiable.

The Speed-Vest will be undergoing speed trials in Portland, Oregon at an undisclosed test track this Sunday night. If you are interested in bringing the Speed-Vest to your town or event, or just want more info, please drop us a line:

info @ speed vest . com