Wheeee – It’s a Wii Remote in Physics!

The following is a guest blog post written by Dr. Lenore Horner of SIUE (a physics professor who works down the hall from me and who has the best toys in the department.)

In late October or early November of last year, eons in academic life, one of our graduate students introduced me to something that I think is going to have a dramatic impact on teaching physics and on how we interact with computers, especially in the classroom. Why do I think this is going to be so important? It’s cool, it’s powerful and flexible, it’s cheap, and a fair number of our students already have or want one. The gadget I’m referring to is the remote for the Wii gaming platform, sometimes called the Wiimote. The Wiimote measures acceleration and position in three dimensions. Better still, it communicates with the world using the Bluetooth protocol which most recent computers also use. What this means is that the Wiimote can be used for a lot more than playing video games. To get an idea of what kinds of things, take a look at Johnny Chung Lee’s videos: tablet computer / smart board, virtual reality, finger tracking. As far as classrooms are concerned, I think the smart board application is going to have the most impact: it’s easy to use and, to be terribly mundane, the price is definitely right.

wiimote_in_use.png
Wiimote tracking acceleration (green spikes) of a cart on an air-track
as the cart rebounds off a stretched rubber band.

If you have a Wiimote handy, or can extract one briefly from a nearby teenager’s hands, take a look at DarwiinRemote (on Macs) or WiinRemote (on PCs) to get an idea of how the Wiimote might be useful for teaching physics. Being a Mac user, DarwiinRemote is the only software I have any first-hand experience with for the Wiimote. In fact, I spent most of fall break in the middle of my parents’ living room floor with family and in-laws carefully avoiding me while I muttered imprecations and obscure incantations as I tried to learn Xcode and Eclipse (free software to make programming easier), Objective C and OpenGL (programming languages), and Subversion (a way of letting a bunch of people work on the same program without driving all and sundry completely crazy) just so I could make DarwiinRemote a better platform for teaching physics. I haven’t finished yet, but will get back to it eventually – maybe spring break. The Wiimote tracks position by tracking the locations of up to four infrared light sources with a camera in one end of the Wiimote. (The camera is reported (see Sensing) to be made by PixArt and works by triangulation.) I haven’t set up my light sources yet, so I’ll have to write about that some other time. The Wiimote tracks acceleration through a tiny mass suspended on even tinier springs in three directions. What the Wiimote reads is how much the springs are stretched. Since the mass is suspended within the body of the Wiimote, dropping the Wiimote reproduces the condition of astronauts in orbit – free-fall. (The so called “vomit comet” also reproduces free-fall and some roller coasters at least come close by having parabolic arcs in their tracks.) This means that if you drop the Wiimote, all three axes will report no acceleration while if you set the Wiimote on a flat surface, at least one axis, depending on orientation, will report an acceleration of magnitude g. So what can you do with this? Swing it in a circle around your head and see how high the acceleration will go (the Wiimote can’t measure more than 5g unfortunately). Attach the Wiimote to a long string. Why do two or three of the traces show periodic accelerations and not just one? Strap the Wiimote to the catcher in a ballistic pendulum experiment and see how long it takes the collision to occur. Walk around and see how you accelerate and decelerate with each step. Try to match a particular pattern of acceleration and deceleration. Imagine athletes strapping a Wiimote to an arm or leg or head to monitor how they move – the next step from video analysis. (The catch here is staying within Bluetooth range, roughly 10m, of your laptop.)

There are a few things I’d like to develop that don’t exist yet. One, which has some implementation but, as far as I’m aware, for Macs, is tracking two Wiimotes with the same computer. Then students could see, in real time, the accelerations of two carts as they collided with each other. For ergonomics, particularly in sports, it would be nice to have a small data recorder light enough and rugged enough to be carried with the athlete so that the Bluetooth range wouldn’t be an issue. There is software using the Wiimote to teach drumming technique (p20).

Motion sensors aren’t really new in teaching labs, so why did this one get me so wound up I’d spend a whole vacation teaching myself new stuff just so I could play with it? One thing is that it’s three axes and not just one. Another is that it’s relatively small and light – designed to be held and swung instead of rigidly mounted. A third is that it’s cheap enough to buy as a toy and the software is open source so I can fix it if it doesn’t do what I want – which I’ve already done some of. Lastly is the fact that the Wiimote wasn’t designed for a specific experiment, it was designed to do more or less everything and it’s up to us to find cool things to do with it.

Finally, I’m very excited that I have four of Southern Illinois University Edwardsville computer science students whose senior assignment to write a cross-platform piece of software specifically focussed on using Wiimotes to teach physics.

For more on open source software for the Wiimote on all operating systems, go to the Wiili site.

8 Comments

  1. Beth February 13, 2008 at 10:36 pm #

    Oooooh! I want to keep up on this. I use Eclipse and XCode mostly using C++ and Java. If you need help on the Objective C, let me know. I’m a longtime NeXT user and my husband is an Objective C developer. We haven’t been able to get our hands on a Wii yet, but maybe I need to go shopping again. I know I can get a remote fairly easily.

  2. Jay Parkhill February 13, 2008 at 11:01 pm #

    I once met the founder of the company responsible for the “magic” first-down line in football on TV and the hockey puck tracer in TV NHL hockey. They had developed their own accelerometer to trace movements in sports like diving and aerial skiing, but I’ve never seen it go anywhere.

    All of which is to day that the “it would be nice to have” has been done. Getting it used is another matter. Cool thought though.

  3. michael cassidy February 14, 2008 at 10:09 am #

    the wiimote is sounding like somewhat like the computer. even the brightest [von neumann] didnt think there was a need for more than tree or four computers in the country – then …….

    its also another argument for open source; now if the lights went at apple and microsoft

  4. Doc Kinne February 14, 2008 at 10:25 am #

    Pamela, you’re a Geek. You know that, right? :-)

  5. Scott December 3, 2008 at 12:42 am #

    Define Irony: While googling for information to help me develop our senior project I find a blog from the teacher I’m developing it for about the very software I’m developing. Google infinite loop?

    Scott

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