Brian Connors
17 March 2000
last updated 28 September 2000
If you're reading this page, it's becase you've caught on to the coolest toy of the last few years: Lego Mindstorms. These sets -- outgrowths of Lego's venerable Technic/Expert Builder line -- started off as an educational toy for kids age 12 and up, but rapidly proved to be every bit as popular (or more so) with older kids in their 20s and 30s. Mindstorms is an excellent starter for anyone who's ever wanted to learn anything about mechanical design and robotics. Excellent third-party support is available, and there are even a few good books on the subject out there.
This FAQ doesn't make much effort to cover what Mindstorms (and its related products, Dacta ROBOLAB, Technic Cybermaster, and Technic Code Pilot) are all about; this is simply an overview of what's available to the beginning robotics engineer. If you have any suggestions as to what to add to this document, contact me at connorbd@yahoo.com and let me know what to add.
Mindstorms Sets
These sets are part of Lego's Mindstorms line proper, and one of these will probably be the first purchase most wannabe Lego robotics engineers will buy.
Robotics Invention System (1.0/1.5) -- The basic
MindStorms set, comes with the basic MindStorms
microcontroller ("Programmable Brick" or "pbrick"),
the Robotic Command eXplorer (RCX). It is designed to
allow you to create fairly sophisticated robots;
programming is done on a PC (or Mac or Unix box, with
third-party support) and uploaded via infrared to the
RCX. The thing that makes the RCX interesting is the
fact that it is possible to remove the Lego firmware
and replace it with your own; it has also been quite
thoroughly hacked over, so it's a well-understood
piece of hardware with robust third-party support
(most notably, NQC (which has been tacitly
acknowledged by Lego), LegOS, and pbForth). Standard
Lego development software is a graphical language
known as RCXCode, which is most closely related to graphical languages such as Prograph but is somewhat limited in its capabilities. The RCX is based on work that was
done at MIT.
Extreme Creatures, RoboSports, Exploration Mars -- Three expansion sets
for the RIS. Probably only useful to those playing
with a-life concepts and the like; dissecting Technic
sets is a cheaper way to get parts. The RoboSports package does include a third motor.
The word on these packages is that you're mostly just paying for the software, which is of no use to anyone who isn't using RCX code. You can get a third motor for cheaper just by buying certain Technic sets.
A third set, Exploration Mars, seems to be a somewhat better value -- it allows you to attach a camera to the 'bot (at least if you're using the standard software) and includes information on building a robotic arm.
Robotics Discovery Set -- Based on a pbrick called the
Scout, the RDS is designed first and foremost for
younger children and people with no access to a
computer that supports the IR tower. The Scout is
designed for field-programmability, though it's
basically limited to reacting to sensory input.
However, Lego has recently released software to allow
the Scout to be used over an IR link as with the RCX;
presumably, work is ongoing to create third-party
support for the Scout, but I haven't heard much of
that other than a bit of reverse-engineering on the
Scout bytecodes. The Scout has numerous interesting
features that the RCX doesn't have, though, which
means it will probably come to generate quite a bit of
traffic of its own on this list.
(3/17) I now own the RDS, and I can say it is a fairly simple package -- dual-motor drive is the norm for any sort of maneuverable 'bot, and complicated mechanical design is somewhat out of the question. I do, however, consider it a must-have for any beginning robotics engineer, as it's a great way to learn the basics of mechanical design with Legos.
Star Wars Droid Developer Kit -- Apart from being a
good introduction to robotics for a fairly young child
(i.e. 9-11, old enough to handle a Technic set), the
DDK doesn't have a lot to recommend it. Its
controller, the MicroScout, is very simple, with seven
programmed behaviors and what seems to be a slave mode
that allows it to be hooked up via a fiberoptic
connection to a Scout. More than anything else, it's a
starter/spare parts kit. Its main advantages are that
it's cheap and it comes with instructions on how to
build R2D2 (a model that can be upgraded if you have access to an RCX). One caveat: the box indicates that a
Wintel PC is required to run it. This is not true; it
has perfectly adequate paper documentation, and one
person I've spoken to who owns the DDK has never
looked at the CD it comes with.
The DDK's MicroScout controller supports the previously mentioned VLL protocol, which is closely related to the CodePilot's barcode language. More information on VLL programming is available at Doug Eaton's website, Programming the Lego MicroScout. Note that though it is in fact externally programmable, the MicroScout supports programs no longer than 15 instructions. As of recently (October 2000), prices on the DDK have dropped drastically, making it a must-grab for anyone into Lego 'bots.
Dark Side Development Kit -- Lego must be making a lot of money off this Star Wars Thing, but you can make some cool 'bots out of it. The DSDK is MicroScout-based like the DDK, but supports a few models the DDK didn't, including a rather spectacular AT-AT and a Destroyer Droid. Essentially all the comments above apply to the DSDK, with the additional point that this set doesn't come with the red-herring CD that might needlessly scare off a non-computerized would-be robotics engineer.
Ultimate Accessory Set -- This rather overdue package, released at the end of 1999 IIRC, is a retail packaging of parts that include the Mindstorms Remote Control, extra sensors (including another touch sensor and a rotation sensor), several building elements (mostly various forms of brackets and support elements), and a constructopedia telling you how to use them. It seems like a good value given the price of the sensors that it comes with (a total of maybe $30US through the Lego World Shop).
Technic Robotics Sets
There are two more sets you should know about from
Lego that are not strictly part of the Mindstorms
lineup but are nevertheless related.
Technic Cybermaster (originally only available in
Europe, but now seems to be Stateside as well) is very
similar to the RIS, sharing maybe 70-80% bytecode
compatibility, but it's based on a radio link instead
of IR and has ROM-based (fixed) firmware. It also has
a few interesting features such as motors with
built-in tachometers.
Technic CodePilot is probably the most unusual Lego
robotics set. Essentially it allows you to create
robots that are controlled by bar-code; software (for Mac and Win32) to
generate the barcodes is available online, though I
don't believe the set itself is all that easy to get.
Educational Products
Lego has also created an educational Mindstorms package.
Lego Dacta ROBOLAB -- based on the RCX as well, and
sold through Lego's Dacta division and their
distributor Pitsco, ROBOLAB is Mindstorms for the
educational market. Its programming language
(developed at Tufts University in Somerville, MA) is a
graphical language based on LabView, and is supported
on both MacOS and Windows. It costs about twice as
much as the RIS, though.
Useful Links and Books
In addition to Lego's Constructopediae that they ship with every set, there are also two books on the market that cover Lego Mindstorms from a third-party perspective, as well as a number of sites of interest to those getting started.
Books
Jonathan Knudsen's Unofficial Guide to LEGO MINDSTORMS Robots was the first to market. It's published by the well-known computer book publisher O'Reilly and Associates, and is a very good step-by-step introduction to robot design using Mindstorms. It covers RIS 1.0 and demonstrates not only RCXCode (somewhat de-emphasized) but NQC, pbForth, and LegOS, and should give you more than enough information to get started with Mindstorms and robotics in general.
Dave Baum's Dave Baum's Definitive Guide to LEGO MINDSTORMS is the other book on the market, and was written by the author of NQC. I haven't read it yet, but it's said to be somewhat more demonstrative than Knudsen's book.
Websites
There are a large number of Lego Mindstorms-related websites out there, but I won't make much effort to catalog them. The following two are much more comprehensive sites, and have links to all the other information you're likely to need.
The official Mindstorms Home Page at Lego is where you can get more product data, as well as the spirit.ocx and Scout SDKs to write third-party programs for Mindstorms.
lego-robotics at Crynwr.com is the official website of the lego-robotics mailing list. From there you can find links to almost everything interesting about Mindstorms that this FAQ doesn't cover, like third-party documentation and software packages as well as robot design galleries.
Conclusion
The ones most worth getting right now seem to be RIS
1.0 (with the 1.5 upgrade), RDS, and maybe CodePilot
(its barcodes and the Scout's VLL (Visible Light Link)
protocol are related). Spare parts are best had by
buying and cannibalizing Technic sets or special-ordering from Lego.
