School Geek

Memorial Day marks the end of school for many, but the teachers and students in this School Geek’s NASA Explorer School save the best project of the year for the weeks after Memorial Day. Our NASA Explorer School is connected to the home of the world’s most expensive remote control toys, The Jet Propulsion Laboratory in Pasadena California. We end the year with students using a remote control Lego rover to explore a simulated Mars landing site, photograph geological features, identify the features, and describe the forces that created them.

The past few years we have used a Lego RCX with a long umbilical cord to support the camera and controls. This year the team received funding for 3 Lego NXT and wireless Booster Vision Cameras. The Lego NXT supports Blue Tooth providing truly wireless remote control rover.

Rover: The team tried a number of different designs from Lego NXT Log combing ideas from Urig, ro1000, braico, aardvarkman95 and RC-X finally settling on a design with a lower center of gravity than the default Lego design. We started with a grabber claw, but it kept catching on the rocks because the driver did not have a good view, so we modified the design adding ground clearance and using the third servo to move the camera.

Camera: The team mounted a wireless Booster Vision camera on the front of the rover. The only flaw in the Booster Vision design is the wire connections which can become lose and degrade the picture. The camera’s battery lasted on average about a day. We found a blog post that showed us how to use the NXT’s Port A to power the camera, but it was pretty complex so we stuck with the batteries. To get the video from the camera into the computer you will need some kind of digitizer. We choose the Belkin, mainly because anything we have ever bought from Belkin worked out of the box. In this situation all we had to do was plug the receiver into the digitizer, and connect the digitizer to the USB port on the computer. As soon as Windows recognized the digitizer we had a live picture from the Booster Vision.

Remote Control: Lego has a nifty RCX Control Pad that can be used with Lego’s RoboLab software to control the RCX across the Internet. However, the RCX is not wireless and thus requires a long umbilical cord. The new Lego NXT supports BlueTooth wireless technology, but does not offer a remote control or controller software. The Lego representative for Southern California pointed us in the direction of a joystick control built from Lego Servo. Our issue here was that we would need to canalize a rover for the parts needed to build the joystick control, so instead of 3 rovers we would be limited to one rover, one remote control, and one back-up rover. Someone in the Lego forums recommended we take a look at using a USB PSP controller and the open source program RoboRealm to control the NXT. RoboRealm supports USB controllers and video sources and could be configured to control the rover and the wireless camera all on one screen. It took us a few hours to figure it out and make it work, but as an added bonus we discovered that RoboRealm has a small web server built in that will serve up real time images and will automatically scale the quality based on the number of views.

Blue Tooth: We learned through trial and error that the NXT and the BlueTooth dongle need to be in close proximity to set up the link. Once the link has been establish the NXT could be moved across the room with no problem.