The Unofficial LEGO MINDSTORMS NXT Inventor’s Guide

The accelerometer sensor (see image below), also known as the tilt sensor and acceleration sensor, enables your robots to know “which way is up and when your robot tilts left or right, up or down, or side to side.” That’s according to the official LEGO online store, where you can currently purchase the sensor for $46.99. Your NXT robots can finally determine when they’ve toppled over! The maker of the sensor, HiTechnic, offers more details at their website:

The NXT Acceleration Sensor contains a three axis accelerometer that measures acceleration in three axes, x, y and z. Acceleration is measured in the range of –2g to +2g with scaling of approximately 200 counts per g. The Acceleration Sensor can also be used to measure tilt in three axes.

So what are some real applications for this sensor? Well, you can use it to play a game on the NXT. A more common use, however, is in a mobile robot for determining when the robot is situated at different angles (facing upward, downward, etc.). As with the other available sensors, I’m sure there are numerous other possibilities!

The light sensor included in the NXT set offers a great deal of potential, but it does have limitations. For example, if you’re expecting the light sensor to accurately detect different colors, you’re in for a surprise. The light sensor can detect different colors to some extent, but it’s actually indirectly detecting colors since it is capable only of measuring light intensity. So if two colors reflect similar amounts of light back to the sensor, the light sensor can experience, well, a case of color blindness. How does it tell which color it’s looking at? In short, you can’t count on the light sensor to accurately distinguish between all colors all the time.

Now, however, you can use the color sensor (see below) to give your robots the ability to detect colors. You can buy this color sensor from the official LEGO store. Currently, the cost is $46.99.

According to the makers of the color sensor, HiTechnic, the color sensor is “‘tuned’ to standard LEGO colors. When positioned over a surface, the Color Sensor will return a numeric value identifying the target color.” In addition, the LEGO store reports that the sensor “enables your robot to distinguish not only between black and white, but also a range of bright and pastel colors.”

Sound like fun? Check out the movie below by HiTechnic for one application of the color sensor: brick sorting!