19 Jul 2007 tbenedict   » (Master)

The AVR Dragon rocks. I used it to debug an ATtiny85 with some LED blinker code running on it, and it worked like a champ. My next project is a gravity racer (or "downhiller") for a local club challenge. The idea is to take the idea of the soapbox derby (a gravity race involving a twisting curving course) and scale it down to the size of the pinewood derby. Oh, yeah, and make a robot that drives it.

So what's the appeal? No motors! No drive wheels! So the things wind up being pretty dirt cheap. If you read all the pinewood derby forums, you'd be convinced that the Secret of Speed is smooth axles, perfectly axisymmetric wheels, low drag, etc. For this? So far the Secret of Speed seems to be not hitting stuff and tuning the servo loop that handles steering. (So far none of the ones built at our club has navigated the 8' straight track without smacking wall... This isn't that easy a challenge.)

So I'm planning to use an ATtiny84, which has the 16-bit timer I need for driving the servo. (I could do a single servo on an 8-bit timer, but I've already got servo code written that uses the 16-bit timer.) The ATtiny84 can do debugWIRE, so this'll be the perfect opportunity to try the Dragon out on a for-real project. (WOOT!)

I'm looking forward to the build and to the tuning that'll happen afterward. Should be a fun robot.

The NEXT track the club's going to run is a full-blown slalom course. I'll be curious to see if the best-tuned straight-track cars perform well at all in the curves.


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