The Unofficial LEGO Mindstorms NXT 2.0 Inventor's Guide comes with four new robot designs that Mindstorms owners can use to continue learning about the various controls available in the NXT 2.0 software, as well as to learn some new building techniques. For my Geek Gift review for the guide book, I built and photographed the LEGO robot models: Inventor-Bot, Jeep, Lizard, and Printer. This post features the short videos I took of each of the completed robot models. Each model took approximately 2-6 hours to build.
The Inventor-Bot is a generic, tractor-tread-driven vehicle that has several expansion options within the book and as many more as you can come up with within the Mindstorms set. This video first demonstrates some basic movement programming and then delves into more advanced programming using the ultrasonic sensor to detect objects and turn away from them. Next, the robot is programmed to maintain a specific distance from a moving object — in this case my hand. After that, a ball shooter clip is added onto the Inventor-Bot. The programming is changed to fire a series of balls at whatever object the bot "sees." In the last two clips, the Inventor-Bot gains some antennae, which are used to detect the edges of the table, back up, and then turn the robot in a different direction. Counts of the number of times each antenna is triggered are displayed on the screen in the last video. Watch my video footage of the LEGO Inventor-Bot.
The Jeep is a four-wheeled, front-wheel drive vehicle that can react to obstacles in its path using the ultrasonic sensor mounted on the roll bar. The Jeep is programmed to begin turning to the left as it approaches an obstacle, turning sharper the closer it gets. In the second segment, the Jeep gains the optical sensor, which enables it to follow a black line — or, more specifically, the edge of the black line. The Jeep does this by turning slightly to the left and right rapidly to ensure that it is still following the edge of the line. One aspect of the Jeep's programming that I especially like is the portions that adjust the left and right drive motors' speeds up or down depending on the direction and sharpness of the turn. This keeps the Jeep's wheels from dragging or spinning out while making sharp turns. Watch my video footage of the LEGO Jeep bot.
The Lizard walks across a surface using a complex pair of legs on each side. The Lizard is programmed to respond to four types of food (the four colored balls). The Lizard has the following reactions to those foodstuffs:
- Yellow: Stop
- Blue: Walk
- Red: Get Mad
- Green: Say "Thank You"
I was pleasantly amused with the AT-AT Walker-style movement of this model but was slightly disappointed in the construction of the tail. It is tied to one of the walk motors so that it swishes back and forth as the Lizard walks, but the construction isn't as strong as I'd like it to be. Over time, the tail mechanism separates from the motor, causing the tail to stop moving. Watch my video footage of the LEGO Lizard bot.
I think the Printer is the most interesting robot in this set. In this video, you can see that the printer uses a Sharpie marker to draw lines on a sheet of paper. With very intense programming, you can create nearly any drawing with the Printer.
There are three moving parts in the printer. The first are the wheels underneath that move the paper back and forth in the printer. These wheels facilitate the drawing of lines on the vertical axis. Second is the carriage that moves from left to right across the top of the printer, which facilitates drawing on the horizontal axis. These two combined allow you to draw diagonals and — if you have a lot of time on your hands — circles. The final moving part is the marker-holder. It raises and lowers the Sharpie so that it only makes contact with the paper when you intend to draw a line.
This video shows the printer drawing the LEGO Mindstorms NXT 2.0 logo on a sheet of paper. Because the drawing is based on the amount of time or rotations the motors make, sometimes lines drawn separately do not connect at correct points or make sections that are supposed to be even uneven. This can be seen at the bottom of the logo; the left and right sides aren't the same size. This is probably due to either resistance in the paper movement or a slight wiggle in the marker mount. The program to make this robot draw the logo is so large that I had to erase the rest of the programs off of the NXT computer block to be able to download to it. Watch my video footage of the LEGO Printer bot.