I said last week that I wanted to switch gears for a bit and work on a few projects that I’ve been neglecting while I focused on the Project:65 computer. First on that list is this cool little robot kit I picked up from Adafruit a couple of months ago. It’s the Parallax Board of Education (BoE) kit for Arduino. I chose this kit for my first foray into robotics because it included everything I needed (except the Arduino itself) and because it came with an extensive set of tutorials. Since I don’t know anything about how to control servo motors, it seemed like a good place to start.
The main idea for this kit is that you use an Arduino as the brains of the robot. It’s connected to the BoE shield, which attaches to the frame of the robot. In a lot of ways, the BoE shield is just a bigger-than-normal Arduino shield. It provides access to all the Arduino’s IO pins, and has a little breadboard area in front for hooking up sensors and stuff.
The shield’s most important job is to drive the servos that control the robot’s wheels. You can’t drive a servo motor very well using the Arduino directly, because it just can’t provide enough juice. You’ll notice the bigger voltage regulator and heat sink in the center of the BoE shield, which will provide the extra power. The whole thing runs off 5 AA batteries nestled underneath the main body.
For the most part, the robot went together very easily. The hardest part was early on, when I was attaching the Arduino to the BoE shield. The kit includes some screws and plastic (nylon?) spacers to secure the two pieces. With the Arduino Uno I’m using, that proved to be a really tight fit, and I had to trim down one of the spacers so that it would fit next to the Arduino’s headers. I believe older Arduino models had a shorter header in that spot, which wouldn’t have gotten in the way.
Friendly reminder, kids: wear your safety glasses when you’re doing something like that. The spacer was very hard plastic, and I actually snapped the blade on my X-acto knife trying to cut through it.
Afterwards, I decided that I probably would have been just as well off leaving the spacer out, but sometimes solving the problem is more important than deciding whether it needs to be solved or not. One thing’s for sure – that Arduino isn’t coming out of that robot any time soon.
With the Arduino and shield attached, I was able to plug in the servos, apply some power, and do some calibration. Each of the servo motors has a little calibration screw which is easier to get at before assembling the rest of the robot. The idea is just to adjust it slightly so that when the Arduino is telling the motor to stay put, it does, instead of turning really slowly in one direction or the other. Both of my servos were pretty close right out of the box, so with a slight adjustment I was ready to go.
The rest of the assembly reminded me of playing with an Erector set, except easier. Of course, the Erector set I had as a kid was a hand me down from my Mom that had seen better days. By comparison, this project featured much lower risks of either electrocution or Tetanus. I definitely appreciate the steel chassis, and especially the fact that it has a lot of convenient-looking attachment points for… well, I guess we’ll see what they can be useful for.
There’s a picture of the completed build up at the top. It’s a cute little thing with two powered wheels and a freely-rotating wheel at the back. It’s not tremendously fast, but hopefully that will translate into accurate movement. Now as far as controlling it, I’m going to start in on the tutorials and see how far they go, and then see if I can get it to do something interesting. You can expect to hear more about it in the future – either when I’ve got it doing something cool, or if I need to vent about something not working the way I want.