Archive for November, 2007

Tag-Bot and the Great Escape Video

Thursday, November 29th, 2007

I recently added a funny video of Tag-Bot, the robot from Chapter 14 of The Unofficial LEGO MINDSTORMS NXT Inventor’s Guide. Check it out below. For one part of the video, I stuck my camcorder (which is very small) onto Tag-Bot’s “head” with the aid of some special “glue dots.” Using this approach, I was able to get some video of what it looks like from the robot’s perspective!

New NBC/NXC Version Available

Tuesday, November 27th, 2007

I programmed extensively in the NQC (Not Quite C) programming language for the RCX microcomputer. That’s why I’m glad to see that John Hansen is working hard on the NXC (Not eXactly C) language, which is very much like NQC. In addition, he is simultaneously developing the NBC (Next Byte Codes) language.

Beta version 34 of the software is now available, released November 25th. Click here to get the update. Or you can download the latest version of the BricxCC IDE, which also includes the latest version of NBC/NXC.

The BricxCC IDE

Guard-Bot video

Sunday, November 25th, 2007

I’ve put together some video of Guard-Bot, the robot from Chapter 15 of The Unofficial LEGO MINDSTORMS NXT Inventor’s Guide. As noted in the book, an interesting characteristic of this six-legged walking robot is that it uses two independent motors to power the legs, and each motor powers a set of three legs on its side. Normally, this would result in the robot’s legs eventually becoming unsynchronized (which would make walking very difficult–or humorous!). However, using the built-in rotation sensors in the NXT servo motors enables the robot’s legs to stay synchronized quite well.

Using the accelerometer sensor: which way is up?

Saturday, November 24th, 2007

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!

Using a color sensor: what a bright idea!

Thursday, November 22nd, 2007

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.

Color Sensor

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!

Release of the Unofficial LEGO MINDSTORMS NXT Inventor’s Guide

Saturday, November 17th, 2007

The Unofficial LEGO MINDSTORMS NXT Inventor’s Guide has finally been released! It’s still making its way into bookstores, but a number of online retailers now have it in stock. There is one feature of the book in particular I hope NXT fans find useful. Printed on the inside front and back cover in color (yes, color!) is a parts list for the retail NXT set. So if you’ve ever wondered “how many I have left of that type of piece,” you can easily find out the answer.