Leela (Cyclops SpurtBot-or a Bridge to Learning H-bridges.)
As you can tell, I pulled together another experiment based on the Dagu Micro-magician Chassis. I hope no one objects to me calling this a different robot every time I put a different "brain system" on it. This is my third robot listing using it (there was also the DAM v.1 and Johnny 555) and I've lost track of blogs, tips and walkthroughs using it.
Anyway, I built this mostly as an experiment to see if it would work. I wanted to see how simple of a robot I could make using one of the ubiquitous dual H-Bridges that are most commonly associated with microcontrollers-in this case an L298 (one of the red Hex units I have so many of.) The idea is that if you tie the enables and one input on both sides "high" and the other input low, you'll get a signal that drives both motors "forward" (if you're careful about orientation of course.) If you do something simple to take one of the "high" inputs "low," then the motor on that side will freeze up, the other side will keep rolling and it will turn until the input goes "high" again.
What occurred to me was that I could probably do this by making a voltage divider out of a Light-Dependant Resistor. I breadboarded it up with the multimeter and got a good enough voltage difference between the exposed and shaded resistor that it would let the one H-bridge input affected stay high until the "eye" got covered. Here is the circuit as Fritzed and schematic:
So here's the part where I justify what was really just a curiosity as an educational possibility. IgnobleGnome and Chris the Carpenter (and others) have listed several 'Spurtbots' as a means of intoducing robots to youngsters. Here's one based on an LDR but using a transistor and a DPDT relay. There are several great designs using any number of combinations of components. This one could be used as a stepping-stone between "analog" spurtbots and the first true microcontrolled robots taught to kids.
The concepts taught here are H-Bridge function and the differnce between digital "high" and "low," and how they have real analog meanings too. Once a student sees what's happening with the LDR as an input (how it is essentially using variable resistance as a switch) moving on to the control of an H-bridge using a microcontroller. Also, seeing how the H-bridge actually works by having one side continuous and the other "switchable" ought to drive home at least part of the H-Bridge function (PWM speed control and polarity reversal will have to wait for another lesson.)
The name Leela is a reference to what has become my favorite TV show:
Somehow a Sci-fi version of the Simpsons is the most comforting thing I can imagine since they told me I was sick. It puts me to sleep like a favorite song even the thousandth time I've seen each episode, and Leela is of course the most normal character on the show in spite of her cyclopia. I think it bothers my wife that I use it as background noise. I sometimes get self conscious and intentionally put on something I want to listen to less just to make it less likely I'll drive her crazy.
Anyway, I'm completely aware of the fact that my robot-evolution seems to be progressing in reverse. My first machine here was based on the Mac OS X operating system with an iSight camera and fairly powerful arm. Since then I've been presenting things with fewer features and less power each time. I really have to get back on the K-9 track.
But I probably am not done with this set of ideas yet. I'd kind of like to do a two-eyed version of this that can follow my hand a little bit better than we see here. And I want to make it look like a turtle. I might even solder some stuff on it. We'll see.
HASTA LA VISTA, MEATBAGS!