Friday, February 24, 2006

Throw Away Your RCX?

On Nabble, Liz Bilbro wrote:

I'm in my 4th year of teaching LEGO robotics to homeschoolers, holding LEGO robotics camps, and coaching FLL teams. Right now I have almost 30 kids in my classes, and am looking at my summer camp schedule and teaching LEGO robotics at the local U., and my fall schedule.

This has me staring at my investment of 20 RIS sets and thousands of dollars in extra motors, sensors, gears, not to mention probably 50 pounds or so of extra parts.

Is it all a waste?
Should I sell it all on eBay?
Is anyone going to be supporting LEGO RCX robotics in Education? (I've been
using Carnegie Mellon, but they're off with the NXT, it appears...)
Can I use many of these parts if I switch the NXT?
Will any of our ROBOLAB knowledge help us with the new language?

Will any of us be able to buy an NXT in a reasonable time to figure any of this out?

Just wondering... Anyone have any opinions?


I decided to bring that over to my blog, since the answer is probably useful to many people, now and in the future.

For those people who are looking at upcoming investments, my advice would be to hold off any purchases of the Lego Mindstorms, until the Lego Mindstorms NXT will be released in about 6 months. Clearly, I’m not helping Lego’s commercial interests here, but I believe the value that the NXT set brings does matter. I have written or commented about this here, here and here.

But, as Liz asks, what about people who have literally thousands of dollars invested in the Mindstorms RIS sets?

If I was teacher in that position, I would teach them using the RCX. I would teach them about loops, triggers and sensors, motors, parallel behaviors. That would teach them those basics and give them hands on experience. For instance, the RCX allows easily to teach how robust robot software must be. Unlike pure software projects, mechanics, friction and unforeseen events tend to throw programs off.

Only when these basic skills are sufficiently mastered, and when precision matters to the robot behaviors, the time to come to use a NXT set. So initially, I’d have only a one or a few NXT sets for that purpose. Whereas they could experiment freely with the RCX, they must share the NXT on those advanced projects.

Over time, RCX units will wear out and are replaced with NXT units.

But will the RCX parts be around, and how about continued support? Here’s what Lego has already published on this topic:
  • Lego Education continues to provide [RCX] sets, software, technical support and services for Lego Mindstorms for Schools.
  • Tufts University’s Center for Engineering and Educational Outreach will play a key role in providing professional support and advice for new and existing [RCX] users.
  • The RCX motors, RCX sensors and Lego bricks can be reused with the new kit, so that you don’t need to throw away these parts. You can literally connect the old motors and sensors directly to the NXT brick.
  • If you have been using RoboLab in the past, you will find the new LabVIEW environment very familiar. Both products have been built by National Instruments, both products have started from the same underlying software (LabVIEW), and have a nearly identical philosophy.
  • The NXT kits will be available in August 2006.

Does it make sense to mix old Lego motors and sensors with the new Lego Mindstorms NXT? Absolutely! For instance, if you have a car-like robot, you could use a new motor for the steering wheel (precision), and an old motor to move forward (not so precise). Likewise, the difference between the old touch sensor and the new touch sensor is not phenomenal. Nevertheless, “touching” (or hitting) an obstacle is one of the most frequently used ways of detecting the environment.

In addition, I would never throw away the working RCX brick, since it can be used as the perfect slave computer for a NXT brick.

Finally, I hope that sites like bNXT and others will provide you with the answers that you are looking for when it comes to upgrading the RCX, doing the same things with NXT, or mixing parts. Don’t hesitate to ask them!


At February 24, 2006 10:07 PM , Anonymous Anonymous said...

I just bought 10 RCX Education kits even though I knew the NXT would come out in August. I am teaching a Robotics class in the Fall and August was too late to wait. I also wrote a new C compiler for RCX, which I intend to support (see I can't speak for John Hansen who does the NQC support, but I get the impression that's he's in for the long haul on both RCX and NXT.

Now to perceptions and rumors. I haven't seen a "live" NXT kit but I believe that the beams and connectors are technic compatible. Second, rumor has it that the Ed Kit has 3 conversion cables and 7 connector cables. My inference from that is that you get to use everything that you already bought. Third, rumor has it that there is a new firmware for the RCX in the works. If that's true, someone needs to start on blog on fixing all the silly things that LEGO did wrong on the RCX. Fourth, rumor has it that there's a C compiler being released with the NXT hardware. I don't have a rumor on whether that same compiler will target either old or new RCX firmware.


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