>iPod fun

As my winter vacation comes to a close, I realize that I won’t be able to play as much with my new Jesuschristmas gift. There’s some history here: Last year my wife and I decided not to get each other anything but I surprised her with a KitchenAid Stand Mixer (it was a big hit). This year she paid me back with an 8GB iPod Touch. Needless to say I’ve really been enjoying it. Here are a few of the highlights about this cool product:

  1. There’s all kinds of free applications online at the iTunes App Store
  2. My woeful music library only eats up about 4GB of space leaving plenty of room for the aforementioned free applications
  3. It works seamlessly with my mac laptop
  4. Now that I’m planning to take the bus to work (more on that in a later post), I’ve got something to keep me entertained.

As for the applications, people have really made full use of the features. The coolest apps make use of either the built in accelerometer and/or the touch screen. There are a few “balance the ball through the maze” apps out there that are fun and of course some flying/rolling/running ones that use the accelerometer. As for the touch screen, my wife and I are in a furious battle for the high score in Wurdle which is a Boggle clone where you trace out the words with your finger.

Thinking of uses for work, I thought the accelerometer could be quite fun. In Modern Physics Lab I have students interface two 2-axis accelerometers and have them retrace my steps in the computer. There are some limitations but they learn a lot about interfacing and integrating streams of data. I thought it would be fun to play with the iPod in the same way. Well, first off, there are a few apps out there that do this kind of thing. There’s a free one that turns your iPod into a level complete with angle readings. This makes it clear that what’s inside is actually a force reader, not an accelerometer as it’s feeling the direction of gravity’s pull even when you’re holding it still (that’s the image above). I also found a few apps where they are encouraging you to use it in your car so that you can rate your hotrod’s acceleration. But I was disappointed as I looked around for an accelerometer-based tape measure. Essentially if you know all the accelerations taken as you move the iPod from one location to another you can integrate the raw data twice to get the position (in all three dimesions!). I thought that would be really cool. To measure a room, say, you’d place your iPod down on the floor in one corner and then start the program and move it to the opposite corner and stop the program. You’d get all three dimensions in one shot. Well there’s a guy who wanted to do this but he’s frustrated with the level of noise he found. Of course there’s a digital round off problem (he found it to be about 0.1 m/s^2 which isn’t too bad) and there’s lots of jitter as you’re holding it. I’m pretty sure, however, that appropriate software algorithms could correct for a lot of that. In fact I was recently reading how the first accelerometer based gaming consoles struggled until appropriate filters were put in to get rid of the jitter. I think for now I’ll keep having my students do their projects but eventually I might look into making my own iPod app to act as a 3D tape measure.

About Andy Rundquist

Professor of physics at Hamline University in St. Paul, MN
This entry was posted in teaching, technology. Bookmark the permalink.

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