Robot Remix - Helicopter

Last summer, the LEGO MINDSTORMS Community Partners were challenged to come up with a creative design using pieces from the EV3 LEGO Robotics kit (31313) and the new LEGO Technic Fire Plane (42040). Four designs were chosen:  a helicopter that flies in a circle, a cat that turns his head back and forth, an airplane that transforms itself into a standing winged robot, and a dancer that shakes his hips like Elvis Presley. Each design was clever and unique, but clearly fairly sophisticated in their engineering and programming. A few weeks ago, the NXTStep blog published the building instructions and program files for all 4 designs. I was intrigued by the helicopter, but I don't have the Fire Plane. I do, however, have the LEGO Technic Fire Truck (8289), so I decided to give it a try.

What I discovered is that most of the specialty pieces from the Fire Plane set are not functional, but structural. Consequently, it was quite easy to substitute something similar from elements I had on hand. My biggest concern was the helicopter blades, but the swords from the EV3 home edition worked well. The only difficult part was figuring out how to attach them to the rotor in a way that would allow them to spin freely and provide the lift needed to lift the tail and spin the helicopter.

It took me 2 tries to build the main body of the helicopter (the gearing system is very complex). The hardest part was not having access to the original CAD files so that I could observe the model from different directions. The pictures in the building instructions are quite good, but with all the black on black pieces, it's difficult to see how to connect the lower section to the upper section in the last few steps.

I think this is a great STEM activity for those fast finishers who need an extra project. Challenge them to build the helicopter (or one of the other Robot Remix models) using only the components you have on hand in your classroom. Give them the building instructions knowing they are going to have to improvise at points along the way and see what they come up with. Remember, this is a working model, not a decorative one, so "close" isn't good enough to get the copter flying. Good luck and have fun.

Wheelie Bot

The first model in the Tetrix Prime robotics kit is called WheelieBot. WheelieBot is a 3-wheel robot that uses a continuous rotation servo motor on the back wheel for motion and a standard servo motor on the front axle for steering, It's a good starter robot for a beginner, because it is quick and easy to put together. But let's face it - it's boring to drive. WheelieBot has no speed and the steering is abrupt and jerky. I can't think of a better opportunity to introduce a lesson in gears.

Let's first tackle the speed issue since everyone likes to drive fast. To increase the speed on the back wheel, I need to use a method called gearing up. In a gearing up arrangement, a large driver gear is attached to the motor and a smaller follower gear is attached to the wheel. I removed the continuous motor and replaced it with a small 40-tooth gear. My intention was to move the motor back just enough to add a large 80-tooth gear, but the wheel kept hitting the motor housing. I could have avoided this problem by putting the gears on the same side of the beam as the wheel, but then the robot would have been significantly unbalanced (being a 3-wheeled robot, it tends to tip as it is). Instead, I added a second 40-tooth gear to act as a spacer. The additional gear doesn't influence the speed, but it has the added benefit of keeping the wheel turning in the same direction as it did without gears (teachable moment:  an even number of gears changes the direction of rotation; an odd number of gears, keeps the direction of rotation the same). Since the 80-tooth gear is twice as large as the 40-tooth gear, the speed is doubled. If you watch closely, you can see that every time the driver gear makes one complete turn, the follower gear turns around twice resulting in a much more exciting robot to drive.

Unfortunately the faster speed only compounded the abruptness of the steering often causing the robot to tip over. In this situation, I wanted to slow the steering down giving me more control over the steering. This gearing method is called gearing down. In a gearing down arrangement, the 40-tooth gear becomes the driver and the larger 80-tooth gear becomes the follower. I removed the beam attachment hub and replaced it with the 80-tooth gear. You need to make sure the set screw on the gear faces up, so that the 2 nubs on the underside of the gear fit into the holes on the cross beam (the beam acting as the axle between the two wheels). This gives your robot much more stability. You'll need to use two shaft collars to attach the two beam sections together. Make sure all set screws are facing forward before tightening otherwise the front wheels will be out of balance when you turn the power on. I made all these improvements using only the elements in the basic Tetrix Prime kit. It would have been nice to have some additional bushings and another 40-mm axle, but my robot seemed to drive fine without them.

Greebling

I ran across an interesting term the other day on BrickBlogger called greebling. Greebling is a technique used in the movie industry for adding detail to the surface of a large object to make it appear more complex. Greebles are meant to appear functional, but typically they are just simple geometric shapes added to an otherwise smooth surface. For example, the starfighters in the Star Wars movies often sported additional detailing to give them a more sophisticated, futuristic appearance, when in fact, if they were truly designed to maximize aeronautical performance, they would have smooth bodies with no unnecessary protrusions to cause friction or drag.

As I was looking at my LEGO RAC3 Truck, I came to the conclusion that it has been greebled to death. Isn't that what we should be encouraging our children to do? So I went to work on my truck and removed all extraneous LEGO pieces that served no functional or structural purpose. There were a lot. The new design is much cleaner and easier to build and drives just as smoothly as the old design. Better still, I can have my students build this truck in half the time it took to build the original design, leaving them extra time to do their own greebling. Some students might add color; some might give it eyes or a nose; still others might make it look like a flying machine. The best part is, we've all learned how to build a simple drive train, learned a little about gearing mechanisms, and still left room for creativity. Isn't that what good entrepreneurship is all about?

EV3 RAC3 Truck

The other day I was fooling around with the Home Edition of my EV3 software when I noticed the button for "More Robots." What do you know... here was a whole slew of new robot programs and designs that I could try out for free. I clicked on the RAC3 Truck - a front-wheel drive vehicle that uses 2 large motors to power the rear wheels and a medium motor to steer the front wheels. The truck uses the proximity sensor for object avoidance in autonomous mode. You can also remotely operate the truck by sending steering commands with the IR beacon.

The "guts" of the truck is a fairly simple design built from basic LEGO elements, but the body has been significantly embellished with fenders, panels, crossblocks, and eyes - non-functioning elements that appeal to kids and contribute to the truck's futuristic, souped-up look.

From an educational standpoint, two things really impressed me with this model. The first is the gearing system used to steer the front wheels. The drive train is composed of two 4-tooth angular wheels and two bevel gears attached to the medium motor. This yields an extremely strong, yet very precise turning system.

Normally, when you build a vehicle with multiple gears, you always take a chance that the gears will not mesh properly when you first try to drive it. The RAC3 program, however, has a clever little My Block (called "Reset") which eliminates the possibility of this happening. The block starts by turning the medium motor at 30% power for 1.5 seconds. I'll admit, when I first started the program and heard that "click," I thought, "oh no, the gears are locking up." But then the motor turns back 120° and resets. Voila! The wheels are always starting pointing perfectly forward. Very clever.

The other thing I like about this model is the simple program used for remote control operation. It is a perfect tutorial for programming the IR beacon, as well as demonstrating how to program multiple cases in a Switch block. If you're looking for a good STEM activity to use in your classroom, the RAC3 Truck can't be beat.

Tetrix Prime Robots

This summer I taught 2 kid camps using Pitsco's new Tetrix Prime robotic set and I'll have to say that I absolutely love how easy this set is to use. The robots are constructed from 16mm aluminum beams and plastic connectors. Pitsco's new quick rivets and thumbscrews make prototyping simple and quick. The kids literally had time to make 6 different robots during our week-long camp. You can find building instructions for several different designs here.

The kits require a little pre-assembly by the teacher to put together the gripper arm and to pair the receiver with the controller, but it's worth it. The gripper is so much sleeker than the clunky design described in the Tetrix Max builders' guide. The robots are remote-controlled with a double joystick controller (included with the kit) so you can configure the robots for arcade or tank-style driving. Pitsco sells a module that will allow autonomous control of the robot's motors using LEGO's EV3 or NXT, but this is an additional $54. Instead we added an NXT and a light sensor to each robot to give audio feedback (a beep or sound file) whenever the robots drove over little squares of blue tape. I think the kids had a lot more fun driving the robots around to find the tape than they would have had watching the robots find the tape autonomously.

After that activity, I started wondering if I could use that same technique to add a Vernier sensor to my robot. Sure enough, I built a little holder for Vernier's Magnetic Field Sensor, programmed the NXT to beep whenever it detected a magnet, and then scattered little neodymium disc magnets all over the floor. This would be even more fun for kids if the magnets were hidden underneath plastic cups or little Lego bricks.

PicoBoard

Lots of educators are using Scratch to teach elementary students animated computer programming. Scratch is a free programming language developed by the Lifelong Kindergarten at MIT's Media Lab. I think Scratch is an amazing tool, but being an engineer, I like when you can add a hands-on component to essentially a virtual environment. The folks at SparkFun have developed the PicoBoard, which can add an element of sensor control to students' animated creations. 

A few months ago, I bought a PicoBoard from SparkFun (only $35.96 with your educator discount). I'll admit that it was a bit tricky getting my computer to recognize it the first time (I needed an FTDI driver), but SparkFun has posted a wealth of online resources to help get your device up and running. My favorite 3 sensors are the slider, sound sensor, and light sensor. A really simple way to get started is to write a script to simply scale your sprite (animated character) based on the sensor value. For example, in the script shown above, when you put your finger over the light sensor (blocking out the light), the sprite shrinks, but when you shine a flashlight onto the sensor, the sprite becomes really large. Note that this script was written using the older version of Scratch (v1.4). I used it, because you can download this software directly onto your computer. SparkFun has a plug-in that you can add if you are using the online version of Scratch (v2.0).

Chromebooks

It's back-to-school season and I've been hearing a lot of chatter in the educational community about schools switching to Chromebooks. A Chromebook is a different breed of computer in that it is designed to be used primarily while connected to the internet. Unlike a more traditional laptop or desktop computer, its documents and other applications live in the cloud rather than on the unit's own hard drive. My initial reaction to this movement was somewhat incredulous, since many schools have fairly restrictive web usage policies. Teachers wage a constant battle with students sneaking off to chat rooms and online gaming sessions when given access to the internet. But I decided to check it out for myself.

I quickly discovered there are a daunting number of variables to consider when buying a Chromebook - price, size, speed, durability, battery, etc. But after doing a little research and checking out the back-to-school sales, I zeroed in on the CB3-111-C670 Acer (only $178 on Amazon). It's small and lightweight (11.6" at 2.43 lb) with a built-in webcam, Intel Celeron processor, Bluetooth, and a chiclet-style keyboard. I considered the Samsung Chromebook, since it's got a metal body over Acer's white plastic case, but I didn't think it was worth the extra cost or weight. Asus had a really nice Chromebook with a rotating touchscreen that can turn the Chromebook into a tablet, but I was a little turned off by the slower Rockchip processor. I also looked at HP's Chromebook, because they were highly rated, but the HP's do not have USB ports. Since I'm not totally convinced about the reliability of the "cloud," I felt I really needed a method of backup storage, and the Acer Chromebook comes with 2 USB ports, plus an SD card reader.

I haven't really done much with my Chromebook yet, except take it out of the box and turn it on, but I was really impressed with the wealth of educational apps that are already available from the Chromebook store. Once I try a few of them out, I'll come back with an updated review.

The Hexcalator

I was in Target the other day browsing through the toy department when I noticed a display of Vex robotics products. Vex has long been a competitor of Tetrix's metal robots, but they've recently redesigned their products to include plastic parts more in keeping with LEGO's robotic kits. I've been intrigued with their new design for a while now (I've seen them at several technology conferences this past year). So since they were right there in front of me (and the price was right), I decided to give one a try. I picked out the Hexcalator ball machine (only $29.99), because it looked like fun and I thought it would make an interesting demo for my fall workshops. Vex advertises this kit as an Intermediate-level build, only requiring 3 hours of assembly, for kids 8 years and above. I found their claim a little ambitious, since it took me 2 days to get my ball machine up and running.

The primary components of the Vex kits were rectangular plastic plates that snap together with tiny white pegs to form the basic structure. The initial assembly was not very difficult, but I found the instruction booklet quite tedious to follow. I'm a big believer in wordless pictorial diagrams, but in the Vex booklet, all the diagrams are poor reproductions of multiple dark gray plates overlapping one over the other. A parts banner runs across the top of the page, but there is no rhyme or reason to the scale between the various components (a tiny peg is drawn the same size as a large plate) making it very difficult to tell which part to actually use. It would have been so easy for Vex to call out the numerical sizing of each plate (ie. 3x4 or 4x12), so that I didn't have to stick my nose right into the booklet trying to count the holes.

I've read some reviews on the internet claiming that the Vex components are not very durable and I have to say that I wonder about that myself. In my workshop experience, young children (8 year olds in particular) are somewhat clumsy, and I cannot imagine this ball machine surviving intact if it were dropped onto the floor. I'm also not convinced that a typical 8 year old would have the patience and persistence to figure out the building instructions. It took me quite a while to get the machine's complicated gearing system to mesh smoothly (would an 8 year old bother with that?). But despite these concerns, I'm still determined to try to automate this kit with a motor and sensor for my next workshop. We'll see how that goes.

New Focus

When I initially created this blog, I wasn't sure what the focus would be. Should it be travel? office politics? diet and exercise? entertainment reviews? All quite interesting with the potential for a good dramatic read, but as time got away from me (has it really been 4 years???), I thought why not share some of the stuff I do every day in my job as a STEM Education Consultant. Just to clarify for those of you who are not acronym aficionados, this will not be a blog about gardening, but one devoted to hands-on activities in Science, Technology, Engineering, and Math.