November 03, 2007

Happy Hallowheel!

I really like Halloween. I especially get a kick out of making costumes that are tailored to the audience that will be seeing them, as I find costumes funnier when people can really relate to them.

This year I didn't have any Halloween parties to attend, so I wanted a costume that my co-workers would get a kick out of, as they'd be the only ones seeing it. But since I'd be at work, I also needed one that I could take off easily and still look relatively normal. (It's tough to take someone seriously in a meeting if he's dressed like Peter Pan.)

So this year, I was the iWon Prize Wheel. It's nerdy, it could be removable, it's perfect.

You can see the "real" one at

My basic vision was a cardboard wheel attached to my chest. Of course, it had to be spinnable. Otherwise, it's no fun. To take it even further, I thought it'd be funny to make it like the wheel on the site: The player has no control of the wheel, other than just pressing the start button. To get that type of control, I busted out the big (and nerdy) guns: My Vex robotics kit.

Those for the weak of nerd may want to stop here and skip to the final result

I cut a circle out of cardboard, and attached it to a wheel from the Vex kit. The Vex wheel would give my cardboard wheel a bit more mass, and more importantly, provide a sturdy way to grip the axle.

I mounted the wheel assembly on an axle, built a simple frame, and hooked up a motor. Now I could start and stop the wheel via the motor.

The guts of the operation. The motor is the green-and-black piece on the right. The red thing is my secret weapon. I'll get to that later.

Now that I knew the motor could spin the wheel, I needed a way to start and stop the wheel via a button. I also wanted a smooth start-up/slowdown, to make it look semi-natural. For that, I was going to need a microcontroller. The Vex kit also has one of those. I hooked everything up to the computer and got a'programming.

The Vex kit made this really easy. The coding environment doesn't really allow for robust (or pretty) code, but it does simple stuff well. Within about an hour I was able to make the button control the wheel, and add the nice acceleration/deceleration that I was looking for.

I embedded the spin button inside one of those cheap touch-lamps. Ideally, I would have been able to turn the light on and off using the Vex kit as well, but I couldn't figure it out in time, so I scratched that idea. Just having the big button was enough.

Spin Now!
One of these Vex buttons embedded inside the touchlamp

I built a frame out of the Vex erector-set-style pieces, and then embedded everything in a shoebox. I clipped on a few straps from laptop bags for straps, making sure that they clipped on to the metal frame, so that the cardboard wouldn't have to bear any of the weight. My basic costume was complete.

View from the front, sans-wheel
View from the back, nerdery on display

Next up: Cheating. The outcomes for the wheel on the site are controlled by odds, and I wanted mine to be controlled by me. That's where the red thing in the photo above comes into play. Basically, that box keeps track of how far the wheel has spun. Which means that at any point (even when the wheel is spinning), the Vex system will know where the wheel is positioned, and with some clever thinking, can predict where it would stop with reasonable certainty. So I just had to make sure it didn't start slowing the wheel down until it thought it would stop on the desired outcome. It's not perfect, but it was about 90% accurate.

Now that the Vex could determine the outcome, I needed a subtle way for me to tell it which outcome I wanted. Originally, I added two pushbuttons, but they protruded a bit, and made a clicking sound when pressed, so I was afraid people would catch on. Luckily, the Vex kit also has light sensors that act the same way as the buttons do. Once I added them to the frame, I'd be able to signal the Vex where to stop just by covering the "Win" or "Lose" sensor with my hand. I figured I'd be able to make it look like I was just stabilizing the frame while the wheel is spinning.

Here's are the sensors embedded in the top of the box.

The red and black piece is a light sensor

They were a bit too visible, so I disguised them a bit with electrical tape. It worked great, and the strip of tape just appeared to be keeping the box closed.

Covering the red part of the sensor really hid them well. No one spotted them all day.

The day before the contest, my office announced there would be a costume contest, with prizes going to winners in four categories. I think this is the first time in my life I knew that I'd win something. The prize I was shooting for:

Guitar Hero III for the Wii

The big day came, and the wheel was a huge hit. All my coworkers got the joke right away. I got a kick of watching their expressions when they realized it spun electronically. Sadly, my "cheating" feature didn't work reliably, so I gave up on it pretty early, but I really didn't mind, since everyone was enjoying the costume.

The final product

Thanks to Scott for taking this video of the wheel in action

I totally won the costume contest, and Amy and I are now addicted to Guitar Hero. Maybe that's what I'll be for Halloween next year.

Posted by Kevin at November 3, 2007 03:20 PM

Hi Kev,

Every once in a while on a rainy Saturday, I browse through various websites, today it was yours!! Loved your Halloween costume, certainly better than Brendan's...heard he had some tee shirt that looked like a woman in a bikini...he always makes me so proud. Love to you and Amy.

Posted by: Aunt Patty at November 3, 2007 06:35 PM won't stop spinning...I want your liver!

Posted by: Bizz at November 4, 2007 09:41 PM

I got nervous while watching the video when the wheel lands on "candy". I see Kevin slowly reaching towards his pants and that's when I had to close my browser. So congratulations, it really was a scary costume!

This year, I just went the cheap route and did the whole "hospital patient with her butt flapping in the breeze" thing. It went over really well with my roommate.

Posted by: Katie at November 6, 2007 02:12 PM

Again, I can't say it enough...


I had no idea you used the Vex Programming Kit. Good to see you made good use of the kit.

Posted by: Scott at November 6, 2007 10:09 PM


Posted by: jay at November 7, 2007 09:01 PM

Yes, hushpuppies boxes are highly-respected in the home-grown-electronics culture. In fact, HP computers are actually named for the HushPuppies boxes they were originally built in. The "Hewlett Packard" name is just a coincidence.

Posted by: Kevin at November 9, 2007 09:30 AM
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