Terd-L, for Two-Eyed Robotic Differential-Locomotion. (I can't believe I forgot to include that right away. May St. Markief forrgive me!)
Update 24 April 2013
Finally added the video. It shows Terd in both "Follow Me" and "RunAway" modes. I can actually switch the jumpers without tearing off his "shell," but I need needle nose pliers to get in under there and do it! (Extra points if you recognize the music & know why I picked it!)
When I first started planning my entry into the "Diamond Mine" challenge, my idea was to make a Pakbot-style machine with an arm and a camera that I could pilot from a few meters away and use to pick up some chunks of glass. To that end, I bought a bunch of parts, including a vintage Radio Shack/Tomy "Armatron Mobile" robot arm that was advertised as "whining but not working" or something like that. I figured I could rig it well enough to get it to function. In any case, I had too many sick days to complete the project and wound up with a bench full of parts to use for something else.
The base though was a differential drive that I hadn't been planning to use in the Diamond Mine Challenge, so I knew it could go to something else from the start.
No disappointment there! Picking up on the "research" I did with "Leela" I decided to do a slightly more controllable and toy-like machine. It's essentially the same thing with two LDR/voltage dividers instead of one, so the robot kind of follows a hand if it's placed over either "eye."
I was inspired by a couple of other recent LMRbots to make a body for it out of a Dollar-store mixing bowl, and just because I was bored I added the Larson Scanner. The color scheme (yellow LEDS on Cardinal red) is there to honor my Alma-mader Iowa State University, which is held by SCOTUS to be the birthplace of the first Electronic Digital Computer in the US. (Actually, that's only kind of true-I just had a lot of yellow LEDs to use and I thought the red bowl would show up better in the little front-page photograph.)
The Larson Scanner ("Cylon Eye") uses an ATTiny 45, so saying it doesn't have a brain is a little misleading, but it's only using that microcontroller for bling. All the mechatronic decision making is strictly "Analog Computing."
I experimented briefly with trying to invert the signals from the "eyes" to give the bot a zero-turn radius, but wasn't able to get satisfactory results. My plan was to do this on either side:
...it didn't work with the pre-made L298 module though. I even tried it with discrete component inverters (both a 74ac14 and a ULN2803) but to no avail. Something about these L298 modules doesn't like the janky signal modulation. It would have been nice-I could have added bump-switches so that when it hit an object it could turn until it escaped, but again, I kind of hit a wall of my own (the wall of losing interest in a project.)
One thing I did do was put the LDRs on Dupont terminals so that I can switch modes from shadow chaser to shadow-phobe, just by reversing which "eye" links to which side.
So what I'm left with is a fun-looking project that I might give to my nephew as a birthday present. This is probably the last of the "brainless bots" that I'll experiment with for a while though. Until I get another brilliant idea that I haven't seen someone else build there's really no point. I know I can make amusing toys satisfactorily-I need to move on to making useful tools.
(I'll add video later-after this has been on the front page for a while and a few other posts have knocked it down a place or two! ;-)