Nov 30, 2008

Deals on NXT Sets?

Right now, LEGO sets are on Sale at Toys R Us---at least online. (I don't know how long the sale lasts.)

The Good News — Their offer is "Buy 1, get 1 half price".

The Bad News - The full price is $290!!!

In the end, if you want two sets, or can share they deal with someone else, you end up paying $217 for each of the two sets---which is an unusually-good discount.

Anyone know of other special deals right now?

FLL Mission Overview Part 8 - Fund Research or Corrective Action

Objective: Move the money (yellow ball) to the research area (the top left corner) or the research area (bottom right corner) so it's not touching any of the mat outside it.

Point Worth: 15

Mission Location: Ball starts near the house, somewhat in the top right corner. It needs to be move to the research area (top left corner) or the research area (bottom right corner).

Estimated Difficulty Level: Medium

Time Length Rating: 4/10

Unique Challenge Aspects: Watch out for the house! Also - is it just me, or does the yellow ball roll more freely than the gray ones?


NXT Peg Sorter

This NXT Peg Sorter will sort long black NXT pegs from long gray pegs, into two separate bins. A conveyor feeds pegs down in a chute, then the light sensor is used to see the color of the peg as it is sliding down the chute, then a hitting arm hits the black pegs to the side while allowing gray pegs to fall straight down into the other side.

Here is a video of the machine in action:

There are simpler and more reliable ways to sort pegs, but with this project I wanted to do something similar to the way some modern high speed mechanical sorters work in factories. In some of these machines, the items are thrown quickly past a gap in the conveyor belt, where an optical sensor looks for rejects, and then air jets are used to knock the rejected items down through the gap into a reject bin, while the good items continue past the gap to the other side. The challenges are to quickly detect a reject and then to get the right timing between seeing the reject and pushing it out of the fast moving stream. An example is this machine for sorting vegetables (see also the video at the end of the page). Another example that is simpler and closer to how this peg sorter works is seen in this video of a colored pencil sorter.

In this NXT Peg Sorter, the gray pegs are the "good" pegs, and the black ones are the "bad" (e.g. burnt) ones that need to be rejected. The speed of this sorter is limited by how fast the hitting arm can recover after hitting one black peg (not nearly as fast as an air pressure jet can recover), but the rest of the machine is capable of sorting much faster. I didn't put that much time into designing a good hitting arm, so there is definitely room for improvement here. How fast can it get?

Nov 29, 2008

Gaze following robot

Here is another example of how the NXT can be so much more than just a toy. A group of researchers from Technical University of Denmark and the IT University of Copenhagen have built a robot that goes in the direction that you look.

Here's how it works; You sit in front of a computer that has sophisticated eye tracking software (that's right, it knows where you're looking!) It then sends commands via wifi to a robot that has it's own laptop. This laptop then calculates how much power needs to go the motors, and sends appropriate commands to the 2 NXT's onboard. These then drive the motors appropriately. A webcam connected to the laptop streams back video of where the robot is travelling.

I'm thinking it might be possible to bypass the onboard laptop completely, and have the main PC send commands directly to the NXT. You could then put on a cheap wireless video camera to give you the robot's point of view.

Damien Kee

Nov 28, 2008

NXT Plotter

This fantastic plotter uses the Eclipse development environment to process an image. It then send the information to the NXT via bluetooth, which is running lejos.

I quite like how it drives backward for each newline, as opposed to having a fixed workspace. In theory it could do whole banners (although I'm sure it would be quite slow :D )

More pics at

Damien Kee

Happy Thanksgiving

For those celebrating today, Happy Thanksgiving!

Nov 27, 2008

Celebration of 10 years of LEGO® MINDSTORMS

You might have already noticed that LEGO® is celebrating 10 years of MINDSTORMS presently (not last by Alpha Rex's journey around the world): the first MINDSTORMS Set was launched in 1998.
On occasion of that, a celebration took place last week at LEGO®'s offices at Billund (Denmark) with lectures held, videos and models shown and a lot of persons taking part that played a key role with LEGO® MINDSTORMS. Amongst others, also a bunch of community members of the MCP program for the NXT were present.

Have a look at LEGO®'s announcement on the event.

Nov 26, 2008

AlphaRex's RoadTrip to Stockholm, Sweden

Alpha-Rex enjoyed Ice-skating in Stockholm.

Find out about his recent visit and view the picture album here.


FLL: How Do You Practice at Home?

Some FLL teams face a challenge: how do individual team members practice at home without a mat?

FLL teams can purchase extra mats by buying additional field kits. However, these kits aren't available to individual teams after the registration period closes.

What creative ways do your team members use to practice at home?

Nov 24, 2008

New NXT Robot - Guest Blog

Alexandre writes:

I have just built a new version (only partially in Lego), aiming
at more serious goals (testing gaze-interaction to control electric
wheel-chairs). If you are interested, you can read about it on:

Click here to read more... and the first version can be found here.

Nov 23, 2008

FLL Mission Overview Part 7 - Construct Levees

Objective: Move levee blocks to shore while not damaging currently standing levees.

Point Worth: 5 points for each block touching red. 4 points for each block touching green. If the block touches both green and red, it counts for red, scoring 5 points.

Mission Location: North west (top left).

Estimated Difficulty Level: Medium

Time Length Rating: 4/10

Unique Challenge Aspects: This challenge seems easy, though if you score or not may depend on other factors such as the wheel from the Test Levees or simply a slight overturn from the robot.

Setup notes: 5 levees start in Base and 3 start at their positions on the shore centered in the outlines.


One-Kit Wonders on Amazon

The One-Kit Wonders book is now in stock on If you have preordered the book there, you should have it soon. We appreciate it if you can review this book on that webpage, too.

Nov 22, 2008

AlphaRex's RoadTrip to Helsinki

Alpha-Rex enjoyed the nature in Finland.

Find out about his recent visit and view the picture album here.


FLL Mission Overview Part 6 - Get People Together

Objective: Move 3 of a certain type of people to their respective areas; red/white citzens go to the pink grid area, blue/gray leaders touching the tall green mountain, and black/white scientists touching the research area.

Point Worth: 10 points for each group of people (consisting of 3 people each).

Mission Location: The pink grid area in the north-east, the tall green mountain on the south center side, and the research area inside the ice crater in the south-east corner.

Estimated Difficulty Level: Easy

Time Length Rating: 7/10

Unique Challenge Aspects: Another simple mission, but spread all across the board! This is another mission that can be simple strategized to save time and get points.

Refer to setup to see how they start: and for more information.


Nov 21, 2008

FLL Mission Overview Part 5 - Test Levees

Objective: Activate the wheel-roller so that wheel rolls out freely, regardless if the levees are hit or missed. However, if the wheel is strategically blocked so as to not hit the levees, this mission will not score.

Point Worth: 15 points.

Mission Location: In front of Base, slightly to the right.

Estimated Difficulty Level: Easy

Time Length Rating: 1/10

Unique Challenge Aspects: A very simple mission to perform, but can get in the way of other missions. Look out!


Nov 20, 2008

Control the NXT with a keyboard

I get a lot of emails from users who what to use the keyboard to control a robot. So I decided to write a (new) Bluetooth remote that will allow you to do just that. With the remote you can also select from a variety of different sensors and read it's value with a single press of a button. Download the remote from my website. Hope you Enjoy


Nov 19, 2008

Nov 18, 2008

AlphaRex's RoadTrip to Montevideo and Rome

Alpha-Rex was walking on the nice beach of Montevideo.

Find out about his recent visit and view the picture album here.

The other Alpha-Rex went to Rome, Italy.

Find out about his recent visit and view the picture album here.


Nov 17, 2008

leJOS NXJ 0.7

Version 0.7 of leJOS NXJ is out!
leJOS NXJ is a full-blown mature Open Source Java platform for the NXT with a Java Virtual Machine that runs directly on the brick.
The new release
"includes a Windows installer to make installation a breeze for new users (the compressed-file distribution is also still available). New features include better USB support, no more using a paper clip to upload firmware, faster garbage collection, three new GUI tools, a brand new Tutorial, support for many new sensors, bug fixes and much more."

There's also preliminary support for mobile phone remote control and Monte Carlo Localization.

It's decidedly worthwhile to have a look!

FLL Mission Overview Part 4 - Find Agreement (Align the Arrows)

Objective: Point both arrows in the same direction, no matter which direction it is or which robots contributed to it.

Point Worth: 40 points.

Mission Location: North (top) wall, 11 inches away from the absolute center of the wall. The model's base should be centered across BOTH tables' walls, where they meet.

Estimated Difficulty Level: Hard

Time Length Rating: 9/10

Unique Challenge Aspects: This is possibly the most unique challenge this year. It is setup at the beginning of the match by the referee setting the arrows in a random direction, so that they are not pointing in the same way. Then, there is no gurantee that if you are able to complete the mission, the other team will not "uncomplete" it; in contrast, the other team may do the work for you. Also, the arrows are not particularly long, so that they overhang the wall very much. This will be quite the interesting mission to watch.


Nov 16, 2008

RoboCup Junior - Rescue (Australian Version)

We recently had our Australian Championships for RoboCup Junior. One of the divisions I'm heavily involved with is the rescue league. The robots need to navigate the maze of tiles to get to the 'chemical spill' (large green area). Once there, they need to 'rescue' the victim. (juniors just push it out, seniors have to lift it onto a platform).

The maze itself consists of a sequence of tiles, which are revealed to the participants just before each round. The sequence changes for each round and generally gets harder as the rounds go on. Plenty of NXT robots as well as RCX versions and a few hybrids and custom built robots.

This video was taken by one of our student referee helper over the two days.

Damien Kee

NXT Safe

From the description:

"This 6.5 Kilogram heavy weight SAFE has an electronic code lock. Five double-digit codes are required to open the lock. The (left-hand) dial is direction sensitive...(there are) 305 billion code combinations for unlocking the door!"

It also includes a motion alarm. More details are here.

Robot Inspiration Series #15: Radar/Mapping Robot

In the RIS days, it was hard to make a robot that could map out its surroundings using only LEGO's official parts, since there was no distance sensor like the US sensor. Now with the NXT, it can be a lot easier. This week's inspiration is to create a robot that can at least partially map out obstacles in its surroundings. For example, can your robot display a "map" of a room, showing where the obstacles are in it? If you wanted to take it even further, you could try to make the robot "store" the map in memory and then navigate around obstacles using the map (this might be pretty advanced, since you would need a system to tell the robot its position, so that it would know if it was getting near the position of an object on the map).

One very nice example of a radar robot was posted on the blog earlier, here. This robot spun around 360 degrees and mapped objects within a certain range, like radar. This method seems relatively easy, but has the drawback of only detecting one side of objects; it can't see how far back objects extend and it can't detect objects that are behind other objects. It also has a limited range. It would be ideal if you could get a robot to make a more complete map, showing whole objects. However, this I admit seems extremely hard to do... I haven't even been able to think of a system that would do this, much less design one. But, like the LEGO MINDSTORMS motto, the possibilities are endless!


P.S. You can see other posts in this series here.

Nov 13, 2008

Lunar Robotics Challenge

Last week, the first Lunar Robotics Challenge took place on the vulcanic island of Teneriffa. The aim of that contest hosted by the European Space Agency (ESA) was to retrieve soil samples from a lunar-style terrestrial crater with a self-constructed robot rover in preparation for an eventual deployment on the Moon.

Eight teams from European universities took part; although no LEGO® MINDSTORMS NXT robot was amongst the contestants, this event nevertheless is a nice showcase also for NXT robot builders on the challenges and actual problems a robot has to face even when trying to cope with such a task that looks simple at a first glance.

By the way, a German team from Bremen University finally won the contest.

FLL Mission Overview Part 3 - Elevate the House, Turn Off the Lights, and Open a Window

While these are actually three missions, they all revolve around one object: the House.

Elevate the House

Objective: Have the house elevated (and the lever is pointing east) at the end of the match, when the referees score the table.

Point Worth: 25 points.

Mission Location: Between the north-west (top right) corner and the center of the table.

Estimated Difficulty Level: Medium

Time Length Rating: 6/10

Unique Challenge Aspects: This mission is a straightforward one. However, we have noticed that our house has some slop in the gears so that if you choose to elevate the house by rotating the lever, the robot will need to push fairly hard to fight all the slop. This may vary from table to table, but this is another simple thing to check before you run!
Turn Off the Lights

Objective: Have the house window showing black. This is most easily done by hitting the lever on the most western side (to the right, away from Base).

Point Worth: 20 points.

Estimated Difficulty Level: Medium-easy

Time Length Rating: 5/10

Unique Challenge Aspects: Another straightforward challenge, but they had to put it all the way on the far end of the table! Also note that when you elevate the house, the lever to turn off the lights and everything else goes up with it.
Open a Window

Objective: Have the house window all the way open. This is most easily done by rotating the rubber wheel counterclockwise.

Point Worth: 25 points.

Estimated Difficulty Level: Medium-hard

Time Length Rating: 5/10

Unique Challenge Aspects: This slightly more difficult than the above, requiring the robot to find a way to rotate the black wheel - or find another means of opening the window. This too goes up when the house is elevated.

Good luck to all!


LEGO MINDSTORMS NXT One-Kit Wonders--New from No Starch Press

O'Reilly | No Starch PressFor Immediate Release
CONTACT: Travis Peterson
415.863.9900 x300

New from No Starch Press

How to Build Innovative Robots with Just One NXT Kit

LEGO MINDSTORMS NXT One-Kit Wonders San Francisco, CA, November 12, 2008—When the creative minds behind The NXT STEP blog co-authored The LEGO MINDSTORMS NXT Idea Book (No Starch Press) in the fall of 2007, they hoped to revolutionize the world of homebrew robotics by teaching readers how to build unique and compelling robots, such as a slot machine and a robot that helps take photographs. The NXT STEP blog is back this year with a similar goal—to show readers how to build a fascinating selection of robots with only one NXT kit.

In LEGO MINDSTORMS NXT One-Kit Wonders (No Starch Press, Nov 08, 408 pp, ISBN 9781593271886), readers will find instructions for building 10 exciting robots, including ones that can balance and steer, sort M&Ms, drag race, and park themselves between objects. Other robots include:

  • CandyPicker, a robot that picks up candy and other items
  • RoboLock, a security system that locks and unlocks robots using a passcard
  • The Hand, a robotic replacement hand
  • GrabBot, a robot that autonomously finds, grabs, lifts, and moves objects
  • BobBot, a NXT version of the Bobcat skid-steer loader

"We're really pleased to be publishing another book from The NXT STEP blog," said No Starch Press founder Bill Pollock. "Readers will find these robots really fun to build, and we think people will be pleased by the fact that each of them can be built with only one NXT kit."

Whether readers are new to LEGO building or are veterans seeking new and interesting robots, LEGO MINDSTORMS NXT One-Kit Wonders will have them building amazing creations with just one NXT kit in no time.

For more information, to schedule an interview, or to request a review copy of LEGO MINDSTORMS NXT One-Kit Wonders, contact Travis Peterson at No Starch Press (, +1.415.863.9900, x300), or visit

Sample pages from LEGO MINDSTORMS NXT One-Kit Wonders:

book spread

About the Authors
LEGO MINDSTORMS NXT One-Kit Wonders is written by James Floyd Kelly, Matthias Paul Scholz, Christopher R. Smith, Martijn Boogaarts, Jonathan A. Daudelin, Eric D. Burdo, Laurens Valk, BlueToothKiwi, and Fay Rhodes

The nine contributors to LEGO MINDSTORMS NXT One-Kit Wonders are dedicated NXT robotics fans who write for the popular blog The NXT STEP, recognized as one of the best sources for news and information about the NXT. Many of the authors have been involved with LEGO as members of the MINDSTORMS Community Partners program, where they advise LEGO regarding NXT marketing, events, and future developments.

Additional Resources
Excerpts from Chapter 1, "CandyPicker," and Chapter 10, "The Bike" (PDF)
Table of contents overview
Detailed table of contents (PDF)
Large cover image

By the Contributors to The NXT STEP blog
November 2008, 408 pp
ISBN 9781593271886, $29.95 USD

Available in fine bookstores everywhere, from, or directly from No Starch Press (,, 1-800-420-7240).

About No Starch Press
Founded in 1994, No Starch Press is one of the few remaining independent computer book publishers. We publish the finest in geek entertainment—unique books on technology, with a focus on Open Source, security, hacking, programming, alternative operating systems, and LEGO. Our titles have personality, our authors are passionate, and our books tackle topics that people care about. See for more information and our complete online catalog. (And most No Starch Press books use RepKover, a lay-flat binding that won't snap shut.)

About O'Reilly
O'Reilly Media spreads the knowledge of innovators through its books, online services, magazines, and conferences. Since 1978, O'Reilly Media has been a chronicler and catalyst of cutting-edge development, homing in on the technology trends that really matter and spurring their adoption by amplifying "faint signals" from the alpha geeks who are creating the future. An active participant in the technology community, the company has a long history of advocacy, meme-making, and evangelism.

# # #

Video - World Robot Olympiad

Tomas G. emailed me a link to a video from the World Robot Olympiad - a nice view of a different type of competition. If any of our readers have more information on what we're seeing in the video and what the challenge(s) are, please let me know.

(Be sure to watch the small advertisement on the right side and watch for the Honda Asimo advertisement - very funny and you can almost see the day when we have these robots working all around us in restaurants and other places.)

Nov 12, 2008


Michael Gasperi, co author of already 3 MINDSTORMS books has written a new book: "LabVIEW for LEGO MINDSTORMS NXT". It is now available from the publisher at .

You can also get a sneak peek of chapter 2.
Looking forward to a review.

NXT Twistcar

Guy Ziv over at designed this amazingly cool "Twistcar", which moves and turns with only one motor.

Nov 10, 2008

Robot Inspiration Series #14: Remote Controlled Robot

This week's inspiration is to build a robot that can be controlled by a human. Although remote controlled robots may seem relatively easy to program and perhaps build, they don't have to be. Building and programming the remote control system can be a big challenge by itself. In addition, a robot that is remote controlled can still have many autonomous functions so that the driver doesn't have too many things to keep track of. For example, since I'm competing in FTC, a competition involving remote controlled robots part of the time, I'm constantly looking for ways to program my team's robot to either help the driver or take care of functions entirely so that the driver doesn't need to worry about it.

One fun application of remote controlled robots is a Battle Bots game, where multiple robots try to flip or disable their opponents. Once I made a remote controlled robot to battle with some of my siblings' Spybots. Racing is another possible application of remote controlled robots. If you have a wireless camera to attach to your robot, you could make a robotic explorer that would let you explore a room while sitting at your computer.

Some robots you can use for inspiration include my PC-Controlled Robot, Jim's remote controlled robot with camera goggles, and Philo's Spy Camera Rover along with his NXT Joystick. There's lots of others out there, and feel free to comment with any good ones you know of!


Dean Kamen interview - FIRST mentioned

Interesting article... particularly Dean's challenge to the kids.

FIRST, if you're reading this - please ask Dean to bring the car to World Fest in April 2009.

New NXTLog Building Challenge

NXTLog put up a new building challenge... this time contestants have to build a robot for a holiday. Read about it here.


Nov 9, 2008

Bike from "NXT One Kit Wonders"

The "No Starch Press" web site has posted an excerpt from the new book, "Mindstorms NXT One Kit Wonders".

The excerpt features an NXT bike that can steer and move by itself, designed by NXTstep blogger "BlueToothKiwi". The bike can be built from one NXT retail kit.

The direct link to download the excerpt is here.

Nov 8, 2008

Datalogging Disney Redux

About a year ago, I blogged about datalogging acceleration profiles of several rides at Walt Disney World, using the HiTechnic accelerometer and the NXT. Well the story doesn't end there. I mentioned this information on a Disney fan site, where not only were people interested in the results, but asked for more - particularly a ride called Rockin' Rollercoaster, which uses a linear motor to shoot the train forward at high acceleration straight into a loop. The problem was this coaster exceeds the 2.5 G limit of the Hitechnic accelerometer, so I decided to try again, using the "Version 3" accelerometer from Mindsensors, that can reportedly measure up to 10 G's. Mindsensors very graciously providing me with a unit to test, and I thought this would be the ideal way to do it... subjecting the hardware (& myself) to high-G rides, and review a sensor in the process.

The Mindsensors newest accelerometer was mentioned here back in August: it has a user-selectable range (2.5, 3.3, 6.7, or 10.0 G) and comes in a much improved form factor. Small, flat, and protected, it was much more suited to the type of abuse I was planning than the older versions. Controlled via I2C, it proved fairly easy to use from NXT-G using the custom I2C blocks. It also mounts firmly with the blue axle pins: pinned to the side of the NXT, it never came loose (even when I ended up sitting on the NXT on one ride at over 2 G’s). The increased range and high resolution of the sensor were nice pluses as well.

There are a few cautions I uncovered however. I was worried about shearing off the exposed-looking female port, although as noted it seems to have held up well (& most people would not treat their sensor this way). The increased flexibility in range (good) seems to be coupled with a slower response time (not as good), compared to the HiTechnic version: while the LEGO-certified sensor can be sampled about every 20 ms, the Mindsensors V3 seemed to take around 70 ms per reading (this may have been due in part to the way I was accessing it from NXT-G, but I used very similar routines for both sensors). For ease of use the HiTechnic NXT-G block allows access to all the sensor readings in a single operation, while the current Mindsensors NXT-G block only returns one value, requiring potentially 3 separate reads to get the data I wanted (note this was not why the sensor was slower in my tests; I got around these limitations by driving the sensor straight from the I2C level with multi-byte reads).

The results were very interesting. Rockin’ Rollercoaster’s initial kick-in-the-pants acceleration is “only” about 1.6 G’s, but as it shoots up into the 1st loop accelerations on the rider rapidly mount to more than 4 G’s, with the total accelerations topping 3 G’s a couple of other times (this 4 G reading was the maximum sustained acceleration I’ve recorded in the park so far, for those of you who like the extremes). The initial horizontal acceleration could even be integrated to show a terminal speed of 53+ mph as it exits the launching area: one of the very few times I’ve been able to use pure acceleration data to get a good estimate of speed and position (0 to 53 mph in 3.2 seconds or 160 ft). The Tower of Terror is a ride that subjects you to the equivalent of a possessed elevator, shooting you up and then immediately putting you in free-fall in an unpredictable 45 second sequence. Here the data showed that peak accelerations are carefully controlled to 1.75 G’s, and when it drops it really does briefly accelerate downward faster than gravity alone (not that you doubt this, as the seat is literally pulled away from your body as the elevator suddenly drops… it was “interesting” trying to keep the NXT firmly positioned on the seat with one hand while my body was thrown up against the insubstantial-seeming lap belt). There are also periods when the ride acceleration is carefully controlled so that you are “falling”, but not as fast as gravity would have you – I didn’t actually notice these at the time. Test Track (a ride in a computer-controlled car) subjects you to at least 2 G’s of acceleration in the high-speed exterior banks, with many of the turns, banks, and drops easily seen in the data. Expedition Everest, which I’d previously logged as “at least” 2.5 G’s, showed it’s extremes with the new sensor at almost 3.8 G’s at the bottom of the biggest drop (and several others breaking 2.9 G’s). I even datalogged Splash Mt again, Goofy’s Barnstormer (a “junior coaster”), and one of my favorites, the Spinning Teacups. With a strong hand and a stronger stomach, I could easily crank the hand-powered teacup around at perhaps 40 RPM, experiencing almost 1.5 G’s in the tiny ride (and nearly making some of my passengers a little sick… hey, sometime one has to sacrifice in the name of science).

For the full range of results, as annotated graphs, please look at my Brickshelf folder (after moderation). All the newest data has been labeled with the prefix "DLD" (for DataLoggingDisney, the name of the program I used to to this):

Datalogging Folder on Brickshelf (after moderation)

For anyone curious as to how bulky or awkward the NXT is for datalogging, here's a picture of the setup I took - the entire thing will fit in my pocket. There are actually four sensors: two for acceleration, one for pressure (to determine elevation if I wanted), and a touch sensor that can be used as a fourth "button" to label certain points in the datastream. Over the front is a flip-down button guard, to keep me from accidentally stopping the program or turning off the NXT during a violent ride. I'd love to see some others do this sort of thing - as many of you now have the technology to do this literally sitting in your house, and as an educational opportunity is is almost unmatched (I'll be happy to sent a copy of the program and instructions for those interested). That’s actually about all the big acceleration rides at Disney. I guess I’ll have to start hitting Cedar Point and some of the Six Flags establishments now ☺.

Brian "still dizzy" Davis

One-Kit Wonders hitting the shelves!

While it took quite long for the authors to create this book, it was worth the waiting. The books should now be shipping to the bookstores and it will be available on Amazon soon. Pre-ordered copies shouldn't be far from your mail box either.

We've got a section on the forums for discussion and updates for the book here. You can find more information about the book by clicking the tags below this post.

Nov 7, 2008

NXT Dolphin

This NXT Dolphin will "swim" across your carpet by flapping its tail up and down, using a mechanical ratcheting trick in its tail to make forward progress. Dolphins are gray on the top and white on the bottom, so with a little work the standard NXT part colors actually contributed to the design!

Here is a video of the dolphin in action:

Nov 6, 2008

FLL Mission Overview Part 2 - Bury Carbon Dioxide (Carbon Sequestration)

Objective: Move the Carbon Dioxide (gray balls) to the Underground Reservoir (outlined square in the top left corner) so that the balls are touching the protruding outline or the mat inside the outline; the ball cannot touch the mat outside of it.

Point Worth: 5 points for each gray ball touching the Underground Reservoir.

Mission Location: The Carbon Dioxide (gray balls) are scattered throughout the table, generally near the vertical center. The Underground Reservoir corner is in the top left corner.

Estimated Difficulty Level: Medium

Time Length Rating: 8/10

Unique Challenge Aspects: This mission looks like it will take quite a bit time since the balls are scattered all across the board. This is where good mission planning comes in; teams may be able to incorporate this mission with others to save time.

Also, the outline protrudes from the table surface quite a bit, so the robot cannot simply and easily “just” push the ball in. While this method is possible, other methods, perhaps more accurate, may be considered by a team.

Note: It does not matter what happens to the tires holding the gray balls in place; in fact, they can be removed as part of the stray objects rule.

Details here:


PS Make sure to read Jim's post below! Really good stuff :)

One Kit Wonders: The PunchBot

For the new NXT book coming out this month, I chose to create a robot that reaches back a few decades to use an old method of programming - it's called PunchBot.

Long before we ever had graphical user interfaces (GUI) or even the command prompt (look it up if you don't know what THAT is), early programmers used a flat piece of stock paper called a punchcard to submit instructions to large mainframes (basically the predecessor to what we know as servers - web servers, email servers, etc.). They fed these cards into a slot (sometimes a card feeder could be used) and each card contained a small bit of the larger program. I use the word 'bit' here slightly tongue-in-cheek because that's exactly how early programmers did it - they programmed in binary, using only 1s and 0s (zeroes) to perform basic functions such as ADD, SUBTRACT, MOVE, and more commands. (Do a search for "machine language" for more information.)

It was tedious, error prone, and not as glamorous as programming with a nice drag-and-drop interface like NXT-G. These cards were printed with dozens, sometimes hundreds, of small circles or rectangles. Holes could then be punched in the card - a punch in a particular hole indicated a 1... a non-punched hole indicated a zero.

So on a particular card, if you saw the following:

punch - no punch - punch - punch - punch - no punch - punch - no punch

this equated to

1 - 0 - 1 - 1 - 1 - 0 - 1 - 0

That's an eight-bit sequence! - if this were treated as a binary number, it could be converted to the decimal value of 186. You'll need to do some research on binary math to understand this process, but for now what you need to understand is that programs were written using hundreds, thousands, and sometimes even millions of cards containing punched sequences like the one above. Some cards could hold dozens of sequences and other cards might only hold one or two... as technology progressed (laugh), cards could hold more and more sequences of punched values - this in turn meant that programs took up fewer cards!

My Punchbot will show you how to create your own punchcards, with each card holding five bits - the first bit is always "punched" and is how the robot will find the start of each card (I call it the synchronization bit). The remaining four sections of the card can either be punched or not punched. Four bits means I have a total of 16 possible combinations (again, do some research if you want to understand binary counting).

This means that each card can tell the Punchbot to run 1 of 16 possible mini-programs! (Each mini-program is stored in a Switch block that is configured with 16 tabs - each tab can contain one or more NXT-G blocks meaning you can create complex behaviors for each card.)

For example, a card with 1-1-0-0-1 converts to 9. (Remember, the first bit on the far left is a synch bit and isn't counted BUT it must always be punched so it is represented by a 1.)

If I submit two punchcards to my PunchBot, both with this sequence, the robot will run whatever blocks I have in the 9th tab of the Switch block TWICE. You can submit as many cards to the PunchBot as you like - it stores the cards' values in a file and then reads them back in sequence to determine the order that your sub-programs will run.

Building instructions and the complete program are provided in the book, along with some expanded exercises and suggested modifications to improve the robot.

I hope you enjoy it!

Nov 5, 2008

FLL Mission Overview Part 1 - Raise the Flood Barrier

This segment is the first of many that will discuss each of the FLL Climate Connections missions in depth. You can read about them here:

Sorry for the delay on this - school has been quite the time eater!

Objective: Find a way – not necessarily using the lever – so that the large flood barrier/LEGO plate is upright and the red lever is down.

Point Worth: 15 points

Mission Location: Top/Center, slightly offset to the left - just enough to get in the way of the first Find Alignment arrow!

Estimated Difficulty Level: 2/10

Time Length Rating: Low

Unique Challenge Aspects: While this challenge may seem pretty straightforward and simple, there are variables that may affect its completion. The Dual-lock is not perfect, so that the two ends may be shoved together particularly tight at one competition table, causing barrier to be really stiff; at the next table, the two ends might spread apart on another table so that the barrier is particularly loose! This is a simple thing to check for before the round; make sure you do! Remember that teams get at least one minute before the round to check on the table conditions.

Enjoy, and stay tuned for the rest of the missions!


Nov 4, 2008

Vanishing Amazon Reviews

For some reason, all of the reviews for No Starch NXT books have vanished from Amazon.

As you can imagine, these reviews are pretty important---especially when buyers are being careful with their money. If you have enjoyed any of these books, you would be doing these NXT Step Blog authors a favor if you wrote a new review for the Christmas shopping season. The books (by Blog authors) missing reviews are:

LEGO MINDSTORMS NXT Idea Book (by NXT Step Bloggers)
Already a classic.
LEGO MINDSTORMS NXT Zoo! (by Fay Rhodes)
These models require extra parts, but they're worth it!
FIRST LEGO League Unoffical Guide (by Jim Kelly and Jonathan Daudelin)
If you are leading an FLL program---and especially if you are a new coach---this book is wonderful!

Also, a new book of NXT models from contributors to the NXT Step Blog,
will be hitting the bookstores within days. All of the models included can be built with just the base kit, so it's the ideal Christmas present for someone who already has an NXT kit. And please review the book on Amazon, for discerning buyers.


Radio Interview about FIRST LEGO League: The Unofficial Guide

Recently, I had the opportunity to do a 15-minute radio interview about Jim's and my FLL Unofficial Guide and the FLL program in general with the Personal Computer Radio Show on WBAI-FM 99.5... you can listen to the show here.


Using the NXT in FTC

Now that the FTC season has gotten underway and my team has been working on our robot, I've gotten a chance to work with the TETRIX pieces and to use the NXT and other LEGOs with them. The TETRIX system is really nice... it opens up so many possibilities with the NXT system. However, I like to think of it as a sort of "block building" system compared to the NXT. It doesn't have a very wide variety of parts, and most of those parts aren't very small pieces useful for making detailed mechanisms. This makes LEGOs very useful when you need a complicated design in the robot. The big, ultra-strong TETRIX metal is great for the framework and simple, powerful mechanisms, while the NXT pieces are helpful when you need something complex. We've already found a use for NXT pieces in one of our robot's modules, and I was really glad to have had experience with the NXT beforehand. If anyone out there is looking to join an FTC team, your skill with LEGO MINDSTORMS could be very helpful.

One of the main differences I've found between using the NXT for FTC and my other projects is the need to make it work with non-LEGO objects. Our LEGO mechanism had to work with hockey pucks, which weren't designed to fit exactly with LEGO pieces. It's a neat challenge trying to work around this.


Nov 2, 2008

Robot Inspiration Series #13: Robotic Game

After spending so much time building robots, wouldn't it be nice to sit back and play some games... with your NXT! This week's inspiration is to make a game using the NXT. This could be a video game using the NXT display screen and sensors/motors for controls, but it could also be a more mechanical robot, such as a pinball machine.

Some nice examples of robotic games include this Helicopter video game and this pinball machine. There's also a very extensive tutorial on making NXT video games here.


P.S. You can see other posts in this series here.

FLL: A Community Affair

Perry, Oklahoma has its very first FLL team this year.

There are thousands of FLL teams, of course, but Perry's FLL team involves a wide swath of the community:

1) A large corporation in town gave the team new computers, competition NXT kits, personal NXT kits for each participant and transportation costs to all of the team's competitions.

2) The local school houses the team's practice sessions, which are led by a math teacher, an engineer and NXTStep blogger Fay Rhodes.

3) Two local farmers spoke to the team of how climate change has affected their land and livestock.

4) The husband of a teacher built the team's competition table.

5) Several teachers attend the practice sessions and all of the parents are supportive and involved.

The photos in this post are from a recent practice session. QUESTION: How do you involve your community in your FLL team's efforts?

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