Every year, the students in my middle-school Physics by Design class at the Shady Hill School in Cambridge, MA build "meet and greet" robots after they learn Robolab programming. The robot must respond to a wave or a handshake with some sort of enthusiastic display—lights, motion, music, etc. This year, for the first time, we built the robots using the NXT instead of the RCX. To my delight (and somewhat to my surprise), this year's robots were the best ever. In the past, most of the RCX robots had waved back and flashed lights. This year, the NXT robots picked up their feet and danced, rocked back and forth, even high-fived the hand-shaker. The sturdiness and flexibility of NXT beam-and-peg building allowed my students to express their creativity in ways that were difficult with the RCX.
Initially, I had been worried that building with pegs and bricks would be harder
for students to master and more intimidating for beginners than the brick-based
RCX system. While the students did find the NXT frustrating at first, especially
as they tried to build simple cars, they soon became adept builders. In fact,
when we built geared-down "snail" cars—the last car across the finish line wins—their
comfort in building with beams resulted in some extremely slow cars. The motor
of this year's slowest car must turn 5.3 x 1044 times in order for the wheels
to turn once. The gear trains this year were so elaborate that I had to borrow
extra 40-tooth gears from another school, which had never happened in my previous
eight years of teaching with the RCX.
Switching to the NXT gave us additional sensors to explore. With the ultrasonic
distance sensor, we built burglar alarms that detected when people approached,
pendulums that logged the distance to the ground in order to measure period
and frequency, and trombone-like musical instruments that changed pitch as the
slide moved in and out. With the sound sensor, we made clap-on/clap-off machines
to control lights and applause meters to measure audience reaction. I elected
to use ROBOLAB 2.9 with the NXT to retain the data logging activities that were
important to the course learning goals.
So, clearly the quality of the creations and the range of possible projects
have improved. What else has my class gained by switching to the NXT? There
are a host of small improvements—the ease of downloading programs, the adjustable
volume on the NXT, the more sensitive light sensor, the ability to synchronize
the motors. Inevitably, there are also some losses. I miss the simplicity of
the RCX motors and the ability to switch their polarity by reversing a lead.
I miss the ease with which one could build a sturdy two-motor car.
Unfortunately, the biggest problem I found in switching from the RCX to the
NXT occurred right at the beginning—the loss of the RCX's appealing simplicity.
Suddenly, I had a class of beginning builders and a not-so-intuitive piece of
equipment. With the RCX, I had often had the students start the year by designing
simple cars by themselves. With just a brief explanation of how to wire the
motors, they could build functional, if not exactly elegant, vehicles. With
the NXT, this activity became impossible. The students could not build an NXT
vehicle with no instructions—and the building plans that came with the set were
complicated and time-consuming. Instead, I have the students start with a non-motorized
building project—such as a chair for a small teddy bear, using the NXT as the
seat. This less-daunting project lets the students get used to beam-and-peg
building without having to worry about the motors. From there, I move to building
cars. I provide plans for a simple two-motor car; the students may build an
exact replica of my car, a variation of it, or a car of their own design. After
completing these two projects, I find that the students are comfortable enough
with NXT building to tackle more complicated projects with confidence.
When I decided to use the NXT this year, I was not sure if I was making the
right decision. After seven months in the classroom, I am happy I decided to
switch—and I can hardly wait to see what my students invent next!
1. Building with the NXT is quite different than building with
the RCX. At first, you may feel like a beginner again.
2. Start your students off with a pure NXT building project -- no motors,
no programming --to help them get the hang of peg-and-beam building
with the NXT.
3. Give the students building plans for simple cars when they first
4. Include some whimsy. Plan projects that allow the students some creative
leeway. Provide craft materials --feathers and googly eyes make the
NXT less intimidating.
5. And remember, the many advantages of the NXT more than make up for
the hassles of switching.
by Barbara Bratzel
Barbara Bratzel is a science teacher at the Shady Hill School in Cambridge,
MA. She is also the author of Physics
by Design (for the RCX and NXT) book from College House Press.