Lego MindStorms: An Introduction

by Jonathan Knudsen
Lego MindStorms

• MindStorms is a line of robotics kits from the Denmark-based Lego company which is famous for making plastic bricks.

• The kits include Lego brick hardware and a software development enviroment. You can write programs by snapping together visual program modules as you snap together bricks.

• Lego is a big enough player to create a standard in a hobby area (building toy robots) that has lacked one up until now.

The Lego MindStorms Robotics Invention System was clearly the coolest toy of 1999. A surprise bestseller, this set from Lego has captured the imaginations and wallets of people of all ages. It offers the chance to breathe life into Lego creations—to make them move and think. Lego robots are a fun, surprisingly easy way to explore the fascinating and complex field of mobile robotics.

What makes Lego robotics such a success?

  • First, cheap electronics make small robots affordable.
  • Next, Lego bricks have always been a good mechanical prototyping tool. Massachusetts Institute of Technology (MIT) researchers have been combining Lego bricks and small computers in interesting ways for years.

And the fast-growing Internet is an excellent medium for robot builders to gather and share ideas. In the rest of this article, I'll talk about what MindStorms means, what the Robotics Invention System really is, how MIT is involved, the Internet connection, and how all this has changed the Lego company itself.

What is MindStorms?

MindStorms currently includes three main sets:

  • The Robotics Invention System (US$200) contains over 700 Lego bricks and a special robot brain called the RCX. It also includes software (Windows) for programming your robotic creations.
  • The Robotics Discovery System ($150) is a scaled-down version of the Robotics Invention System. It includes a robot brain, the Micro Scout, which is similar to the RCX. Robot programming is done through front panel of the Scout.
  • The Droid Developer Kit ($100) is a set for building very simple robots, including R2D2 from the Star Wars movies. It also comes with the Micro Scout and preprogrammed behaviors.

In This Column

• What is MindStorms?
RCX Programming
Lego and MIT
Lego Glasnost

Of the three sets, the Robotics Invention System is the most powerful (and expensive). It has also been around the longest (since Fall 1998). It has been thoroughly examined and documented, and it supports MindStorms, a large body of software. For these reasons, when many people say MindStorms they mean the Robotics Invention System.

What's in the box?

The Robotics Invention System consists of more than 700 Lego bricks and software for your desktop computer. Most of the bricks are standard pieces from Legos' Technic line, such as beams, plates, gears, axles, wheels, pulleys, and various other doodads. But some of the pieces are specific to robot building.

The most important special brick is the RCX, the robot brain, shown in Figure 1.

The RCX—brain of the Robotics Invention System

Figure 1. The RCX is the brain of the Robotics Invention.

The RCX's outputs can drive motors or lights. The Robotics Invention System also includes two motors like the one shown in Figure 2.

One of two motors included in the Robotics Invention System.

Figure 2. One of two motors included in the Robotics Invention System.

The motor is internally geared down, which means the output shaft moves at a useful speed and probably won't need much external gearing. An internal flywheel makes the output motion very smooth.

To connect a motor to one of the RCX's outputs, you use a special "wire brick." This is a wire with special Lego connectors on each end. You simply snap one end on the motor and the other end on one of the RCX's outputs (Figure 3). The connectors are cleverly designed so that you can attach wire bricks in any orientation.

Connecting motors and sensors to the RCX.

Figure 3. Connecting motors and sensors to the RCX is as easy as snapping Lego bricks together.

The Robotics Invention System also includes sensors that can be attached to the RCX's inputs. The set comes with two touch sensors (switches, basically) and one light sensor (Figure 4).

One light sensor and two touch sensors come with the Robotics Invention System

Figure 4. One light sensor and two touch sensors come with the Robotics Invention System.

The light sensor includes a wire brick. The touch sensors are attached to the RCX's inputs just as the motors attach to the outputs. You can purchase other types of sensors (temperature and rotation sensors) from Lego. If you're handy with a soldering iron, you can even build your own sensors.

Jonathan Knudsen is an author at O'Reilly & Associates. His books include The Unofficial Guide to Lego Mindstorms Robots, Java 2D Graphics, and Java Cryptography.