Today I soldered plugs onto the wires from two of the motors, and tested them with two of my boards. The result: Success! The motors turned, at a rate of about .5 Hz or so, both back and forth. Woo-hoo! The first step towards an army of robots!
However, when I tried to set both motors up at the same time (to check power usage and Arduino connections, and to get a picture of them both moving, they started acting erratically. At first, I thought it was the Arduino connections, cause they had a tendency to pop out real easy. However, I soon found out that the switch I mounted on the power supply was the problem, causing glitches and jitter. Finally, one of the switch wires turned out to just have broken off, so I stripped some more to reattach it. But now, the power supply doesn't do anything anymore, not even with just the car bulb attached. I guess all the twitter must have blown the supply -- possibly just a fuse, but I'll have to open the supply for the first time to check.I might want to hardwire the green line and use a switch on the main power.
Gotta get some proper plugs for the Arduino connections.
The heat sinks get warm quite quickly, I'll have to keep a good eye on them.
Power supplies are fragile to loose connections.