In the relatively short history of robotic kits on the commercial market, a wide chasm has existed between the Lego Mindstorms packages and the far more complex, high-end fare offered by makers such as Evolution Robotics. The Radio Shack VEX Robotics Design System bridges that gap with an accessible, yet not-too-simple robo kit for kids in their early to mid-teens. In fact, this well-machined, decently documented kit succeeds as a helpful introduction for roboticists of virtually any age.

The VEX system arrives in a box roughly 18 by 24 by 8 inches (HWD), filled with Erector Set-style bars, screws, nuts, actuators, motors, wheels, and gears, and a binder full of instructions. The manual is not only helpful—it's completely necessary for beginners. It offers a comprehensive look at the hundreds of VEX parts and a step-by-step guide for building your first robot. Our only complaint with the documentation is that it identifies the different sets of Allen wrench screws by their size and width. The packets each set of screws comes in do not repeat these naming conventions, so you have to eyeball the pictures and the screws to make a match. That's pretty much impossible. Fortunately, the primary difference on most of the screws is length.

Thanks to the extremely well-machined screws, nuts, bars, plastic gears, and components, building your first robot—"the squarebot"—is easy. The VEX system was built with the education market in mind and is part of Dean Kamen's popular FIRST Robotics competitions. As such, it's really designed to be built by a small team of teens (under the guidance of a teacher), and the manual recommends that different groups take on the structure, subsystem, sensors, and so on. In my tests, just my 10-year-old son and I worked together, and it took us about four hours to build the squarebot. One of the admirable things about the manual is that it intersperses building instructions with lessons on robotics fundamentals, such as sensors, gears, and torque, and how balance and center of gravity can work with or against your robot.

The section on sensor use and the microcontroller is quite complex—as is the controller itself, which contains dozens of ports for sensor plugs and jumpers. Varying the placement of the plugs changes the robot's behavior and interaction. We chose to follow the basic instructions and placed the plugs as the manual instructed.

The robot and accompanying pro-level remote control take 14 double-A batteries. The manual recommends the use of rechargeable nickel-cadmium batteries, which isn't a problem, except for the additional expenditure for all those batteries and the necessary special charger.

Small Problems

Following the instructions to the letter led us to two problems, one minor and one more challenging. Both the robot receiver and remote-control transmitter use frequency crystals that make sure the remote and robot are on the same channel (in competitions, different teams need to use crystals on different frequencies). When we turned on the remote, we noted that the channel read correctly and the control system had a green blinking light, but we could not make the robot move.

It turned out that our robot had shipped without a matching crystal for the remote control. We received one a few days later and soon had the robot in motion, which led us to our second problem. Our robot had four rubber wheels, with axles running through them into the motors. The manual shows placing the wheels on the axles, but says nothing about securing them. As soon as we started running the robot, the wheels started coming off the axles. We rechecked the manual to see if we had missed an important building step, but we had not.

In the end, we used four extra collars with threaded screws to secure the four wheels. A Radio Shack rep explained that the wheels were originally supposed to lock themselves onto the axles, but that didn't happen in the final product, and the wording and pictures in the manual were never changed. Since this is a learning tool, I don't necessarily consider this a big hitch. Figuring unexpected stuff out is part and parcel of good robotics training.

The basic-box squarebot is designed to run into an object and pause for 2 seconds before hitting it again. If you spend enough time with the sensor portion of the manual, you can learn how to have the squarebot hit an obstacle and retreat from it. At one point, we added a jumper to port 13 (the autonomy port) and turned the robot back on: It chased us around the room like some kind of crazed metal Chihuahua.

The kit ships with sensors that could replace the basic bumper switches and let you easily add edge detection. And enough extra hardware is included to build ball corrallers and even something that might lift a ball and drop it into a basket. Most of these accessories were included with the FIRST competition in mind, where teams of young students from around the country enter hand-built robots in robotic ball-handling events.

At $299.99 (not counting batteries), the VEX System is more than just a kiddy construction set. It is best suited for the scientifically inclined teen (or classroom), and is a perfect fit for the robo-hobbyist who can't afford an AIBO, but might be willing to build his own metal companion.