These past two weeks I've worked on my linefollower project a bit more:
- Built some wheels out of Lexan with my Dremel and circle cutter (not a bad job if I do say so myself.)
- Getting the Hamamatsu encoders mounted and testing reading them.
- Building a little RS-232 to TTL line level converter board w/ a MAX232 chip.
- Wired up the first serial port on the Atmel AT MEGA 162 and put in some test code to read and write from the port.
As far as making the rs232 line level converter: A word to the wise, check out Al Williams' web site AWC for a cheap and easy way out. But I was halfway done with my version before I found it. Since I wanted this to be fairly sturdy so I could re-use it for multiple robots, I made a schematic in Eagle and etched a PCB for it. My first board was a flop. Several of the traces had bridges because I didn't scrub all the paper off, and I accidentally mirrored the image to boot. The second board came out of the etching process much better after using a toothbrush to scrub the smaller bits of paper off. But I didn't align the board and the drawing very well for my 2 layer design. And I crossed RX and TX. And I didn't wire up the power pin. And, well, it was pretty much the worst pcb I've ever made, but it does work. Because I didn't plan ahead on putting it in a particular project box, it won't fit in a project box, so I just sprayed the bottom side with clear enamel to prevent shorts and am using it as-is.
Next on my plate for the linefollower is to get it to drive in a straight line. I can work on my motor controller logic (a PID loop, I guess) now that I have the encoders installed and a serial port for debugging.
Tonight I'm off to the AHRC Robot builder's night out. I've got my eye on making a drivetrain for the wiper motors for building some kind of larger size bot.