Adventures in Robot Building

It’s all about learning, right? I’ve been building a robot from scratch, as you may know if you’ve read some of my previous posts. I started out with only a vague idea of what I wanted to do. I started by saving the miniature balsa crates that the grocery store sells tangerines in. That is a good size for a robot, I thought to myself.

Then I discovered the Arduino. I knew immediately that I wanted the robot to have an Arduino for a brain. Next, I bought a dual gear motor kit and some wheels. I assembled the kit and discovered that it wasn’t going to mount very easily on my tangerine crate. So, I thought about it a while and discovered that if I took the crate entirely apart (it was only stapled together), the side panel was exactly the right size to mount my wheel assembly on.

Originally, I wanted to build a robot with wheels front and back. My BOEbot uses a rear roller for stability instead of having two sets of wheels so I wanted to try something different. After some more thought, I decided to compromise and buy an omni-directional caster for the stability point of my robot. By this point, I had mounted the wheels on one end of the side panel and the caster on the other. I had also purchased an H-bridge motor driver shield to control the wheels (shields are the daughter boards that plug on top of the Arduino so conveniently).

The motor shield came as a kit and I assembled it per the instructions. Try as I might, I never got it to spin my motors. I spent several afternoons troubleshooting the problem and decided that I probably burned out one of the chips on the motor shield. I decided that I should have installed a socket instead of soldering the chip directly to the board as the kit instructed. So, I ordered some replacement chips for the board and proceeded to try to desolder the chip in question. That was harder than it sounded. I haven’t yet managed to desolder the chip in question.

While I was ordering the replacement chips, I discovered an already assembled H-bridge controller that cost less than half what I paid for the motor shield kit. The mini-controller wasn’t as capable as my motor shield but it was adequate for driving the two motors on my robot. All it required was that you solder two, eight pin headers to either side of the board. I was sold. If I could repair the motor shield, I could use the little controller board for another project. If I didn’t get the motor shield fixed, I would still be able to get my robot rolling on it’s own power with the new controller. That was the plan anyway.

When the parts came in, I soldered the headers to the board and plugged it in to the solderless bread board to give it a try. I wired it up and checked my wiring several times. I wrote the code for the Arduino to control the new board. I plugged it all in and uploaded the code and nothing happened.

I spent most of the evening troubleshooting. I still haven’t figured out what is wrong. I will give it another try this weekend. I still have several things I can try. I suppose it wouldn’t be nearly as much fun if it wasn’t so challenging. And like I said at the beginning of this post, it’s all about learning, right?

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