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Sorry I haven't had that much to contribute lately, but I've been doing real work instead ;-) Anyway, I thought you might like to take a peak at a small by-product of my work over the last year and a half - this is a map of one of the floors of the building next to (and above) my lab (caution! 4813x4168 image!)

This is all done with kD-Trees and a bunch of linear algebra on the software side, the hardware side uses a Hokuyo laser scanner and an Inertial Measurement Unit (integrated gyro, accelerometer and 3D compass) all mounted on the top of a radio control car. The map can be built in real-time and shows me a nice position of the car on it as it drives around, so I can easily tell what still needs mapping =)

I hope to be back with something to liven up the rumble soon!

That sounds cool! And pretty fun. =) So the car navigates itself, too? Do you do any pathfinding like with graphs or just trace your way along walls?

Btw, what kind of R/C car is it? Just curious. I was into R/C cars quite a bit when I was really young. (Like too young to build my own cars, just tagging along with Dad and older brother and racing.)

I have some simple wall following in, but right now the car is manually controlled. My project is more based on getting good maps out of it.

It's a pretty tough 4WD thing with knobbly tires. Overkill, but it means that some time in the future we can switch to 3D mapping and send it anywhere.

What brand / model is it? This conversation got me looking at the modern RC10's from Team Associated. :-) But maybe I'm just assuming it's a "real" / expensive R/C car since I remember you were into R/C helicopters too.

Yeah, it's the expensive, modular type. I would estimate it cost ~$300, but the lab owns it, not me. I'm not sure on the brand, I can check when I go in next year =) I actually mostly do quadcopters and planes as well as some DIY things, including all of the embedded programming and electronics for driving motors and speaking with gyros and accelerometers. Fun stuff, but it sucks time and money! I'm also looking at 3D printing, but that can wait until I graduate.

Ah, looks similar to the Team Associated stuff, but electric and 4WD. And we took the cover off and put on a custom platform which holds a bunch of very expensive electronics.

Yeah, I always raced electric, but gas has gotten much more popular since I stopped racing. But I think lots of folks (including Team Associated) still sell electric cars too.

That all sounds pretty neat. But it is indeed a huge money drain, which makes me hesitant to dip my toes in again. :-) So I recall 2 of the 3 main pieces of electronics in cars were "speed control" for controlling the motor and servo for the physical steering. You're saying you actually program those devices yourself, right? Is that just low level programming or designing/modifying circuits too?

A bit of both. It takes some embedded programming knowledge to interpret the signals coming from the radio receiver (I don't bother with trying to make those), figuring out what it is saying, then applying whatever actions you are looking for to the motors or possibly modifying the signal from the receiver and passing it on to servos. The actual 'speed control' is pretty easy electronics wise, particularly if you don't want reverse. If you want reverse and breaking it becomes a bit more complicated and uses about 4x the components, as well as the risk of destroying hardware if you have bugs in your code. You get chips that do it all for you, but then you might as well just buy a commercial solution since you lose a lot of the fine-grained control that the custom solution gives. Servos can also be done custom, but it's easier just to get a commercial one since servo control is a surprisingly complicated problem involving damping, oscillations and holding torque, all of which are dependant on the exact specs of the motor, geartrain and the voltage the servo is running off of. So, low level programming applied to a knowledge of fairly standard power electronics.