Tank track assembled
May 20, 2011
I said in my last blog entry that I wanted to play with the sensors first, and I did a bit, but I decided to go ahead and assemble the chassis and drivetrain first. I got the Tamiya track and wheel set, the dual gear box and the universal plate set. All this stuff is meant to work together, but the directions are in Japanese and it took a bit of kajiggering to get working right. In particular, it gives you no real hints about how many of the track sections to use, you just have to estimate and if you get it wrong, take it apart and try again.
The track set itself is not that hard to work with. The tracks are kind of a hard rubber kind of stuff, and putting the sections together is quite easy with the aid of some sharp tweezers. However, these tweezers are sharp and I actually damaged one of the track sections trying to put them together, but it ends up I don't need all the sections anyway. I put mine together in the configuration it showed on the box. It seems ideal for the small obstacles it will encounter around the house. At any rate, here's a pic, but it's probably nothing you haven't seen before.
I also mentioned just how tiny the Baby Orangutan microcontroller and motor controller board was. It was so tiny, I didn't even see it in the little bag it came in. I knew it was going to be small, just not that small. But here's a shot of the board next to an Arduino and the tiny LCD I got for debugging. I also got a tiny ICSP USB programmer from Pololu (not pictured), these guys really like they're tiny boards. Though boards are expensive, making small boards probably helps them keep costs down.
But anyway, as for the sensor, I did get it working. I found some black magic formula that'll convert from the 10-bit ADC value to centimeters. I found it after an hour of so of googling and testing some things out, only to come here today and someone posted the same code on the forums. D'oh! I know how I could have figured it out, but googling just seemed easier.
And finally, I figured out that running a servo motor from the 5v supply on your Arduino is not such a great idea. It kept resetting the Arduino, but I needed to fire up my "power supply" anyway, which is really just a small circuit zip tied to a 9.6v battery pack. I made it like 5 years ago as a temporary solution, and it's just too useful to disassemble.