Help Me Get Skynet Online (or: Lego Robotics)

April 27, 2007 3:08 PM

RoboFilter: What can someone with a budding (but likely fleeting) interest in robotics do for a first project that combines a little building, a little programming, and hopefully only a little money?

At work we have a tape library to handle loading and swapping of our backup tapes. It's basically a simple robot which moves items of a preditable size between known locations. The infamous robotic parking lots were probably inspired by this, as they're really very much the same idea.

The programmer in me (which is hobbyist level at best) is fascinated by the idea of programming a simple robot of similar design to do something like, say, fetch CDs/DVDs from a rack. Just for fun, not any practical purpose. But I don't have a ton of cash to spend, so if I do this, I don't want to spend more than a couple hundred on it, especially since my interests in these sort of things tend to be fleeting.

So, I'm thinking of picking up a Lego Mindstorms NXT kit, and a few extra sensors/motors. It has the advantages of being easy to build with (being lego), and also having the ability to be programmed with "real" programming languages if the included tools are too simple.

However, I'm also intrigued by the idea of using standard motors and a PIC. Both the design and programming are going to be more complex, but also more flexible. But I have to wonder if it would end up costing a lot more, or if it might be less, or comparable.

So, is there anyone around with experience using the Mindstorms NXT who can tell me a bit about its features and limitations in actual use? Likewise, anyone into more "serious" robotics project who can comment on the ups and downs of going the traditional route?

posted by CrayDrygu to grab bag (9 comments total)

When my children were 4 and 5 we got a first gen Mindstorms kit. (It finally broke when they were about 9 and 10.) I cannot speak to it from the standpoint of a robotics enthusiast, but I can tell you it is very intuitive to use. My kids could build the projects and program it, no problem, and the unit was certainly durable. What a blast that thing was.
posted by Methylviolet at 3:38 PM on April 27, 2007

There is a dorkbot for Boston, although it seems to be in hibernation. You might contact that guy; he should have some good local leads for you.
posted by adamrice at 3:54 PM on April 27, 2007

@adamrice: Thanks for the tip, but I forgot to update my location when I moved a couple years ago. I actually live in New Jersey now :) I'll look through that site, though, thanks!
posted by CrayDrygu at 4:26 PM on April 27, 2007

For the sort-of advanced side, you've got to check out Wiring by the folks from Processing.
posted by tmcw at 4:36 PM on April 27, 2007

If you are a mechanical/electrical engineer type, then I would go with the PIC/motors route. You already have the know-how, tools and experience to build a chassis totally from scratch and have it be pretty much what you want.

However, if you are relatively inexperienced when it comes to putting stuff together, I would *highly* recommend starting with Mindstorms. I haven't used NXT specifically, but I have the RCX and a ton (well, 1/16th of a ton) of Lego and I've built many robots/programmed machines.

The issue isn't the specific version of the tools, the issue is the iterative design process. You are going to have to build, program, rebuild, reprogram, tear apart and start over, build in a whole new direction, program from the ground up, etc, etc, etc. With Lego, tearing apart and rebuilding is easy.

The only real issue is the sensors. But honestly, sensors that are any more complex than the ones that come with Mindstorms are going to require a LOT of programming to be useful. Rather than spend a couple years getting a camera to recognize your DVD jackets, I'd use, say, a simple light sensor to read a barcode you tape on each one.
posted by DU at 5:26 PM on April 27, 2007

Look into a VEX kit -- it's a little more "grown-up" than the LEGO kits. That said, the LEGO kits can be very versatile.

You could also just buy an iRobot CREATE, which I think has a better sensor suite than any LEGO kits, and work with that. That one might have a better platform from which to build CD-fetching functionality or the like. Since this guy is almost all programming, it might give you the experience you're looking for right now.

If you want to branch out into more hacky stuff, look into something like the BOE-bot (runs on a BASIC stamp, which kinda sucks, but is at least a good and relatively cheap robotics intro), or look into something like the OOPic to be your robot controller, and build up around there. However, that will require more building, which will mean more motor integration/lower level programming (assembly, in particular, if you're using PICs, though you can do some of them in C) and more electromechanical integration. Maybe that's good, but maybe that's something to try after you've worked on a kit.
posted by olinerd at 6:58 PM on April 27, 2007

@DU: Excellent advice, thank you :)

I'll have to see if a simple barcode reader is feasable for something like this, I'm not sure the Mindstorms light sensors would be good enough to read a small one, and it would obviously be difficult to integrate an external one.

I was thinking I'd just program the intial state, and let it keep track itself, simply assuming a lack of outside influence on the state of the items it's moving.
posted by CrayDrygu at 7:08 PM on April 27, 2007

@olinerd: Wow, I had no idea those VEX kits even existed. Seems a little pricey compared to Mindstorms -- $300 for the starter kit and another $100 for the programming kit, and the individual components are a lot more outside the kit bundle -- but it also looks a lot more capable. Or at the very least, more sturdy.

The iRobot CREATE, on the other hand, looks like an excellent platform on which to build a Roomba ;)
posted by CrayDrygu at 7:22 PM on April 27, 2007

Yeah, I've lusted after Vex myself. Modularity is the key, though from what I've seen they are more geared (ha!) to mobile robots than generalized programmed machines. Also, Lego is available everywhere whereas Vex is relatively new.

The Mindstorms light sensor is pretty low res indeed, but maybe you can think of a coding scheme that doesn't require much. Or maybe a braille-like code for a touch sensor.

I had no idea about the IRobot CREATE--this looks awesome! It says it has a brazilian builtin sensors, but what are they?
posted by DU at 10:41 AM on April 28, 2007