May 31, 2010

Maker Faire 1010

Not directly related to LEGO® MINDSTORMS NXT, but nevertheless intriguing: a video of the Maker Faire 2010 that took place last weekend in San Francisco (with around 20.000 visitors - it's getting larger year by year).

Oh how I wished I had been there!

Actually, the video alone provided my with some nice new ideas for NXT robots...

May 30, 2010

A step-by-step tutorial for setting up JCreator with leJOS NXJ

Being one of the developers of the leJOS NXJ Open Source project, a Java platform for the NXT, some people asked me for help in setting up JCreator for working with leJOS NXJ.
JCreator is a light-weight Java IDE that comes in a free community edition as well as a commercial one; it's not my favorite one (I prefer Eclipse), but I noticed teachers seem to like it for their robotics classes, considering the barrier to entry pretty low.

So here it is: a step-by-step tutorial on how to set up JCreator with leJOS NXJ, allowing you to program your NXT with Java using JCreator.

Segway in NXT-G

Update March 2012: The project with source code is located here.

In the past year, a classmate and I have researched 'self-balancing robots' as a final year project. The goal was to create a simulation model of such a robot, and the result was an NXT Segway, with a HiTechic Gyro sensor, and programmed in RobotC (and a 170-page document going with it). I found this to be a very interesting project, but since the project document was written in Dutch entirely, that won't be very helpful to most of you.

Another Segway, you might think, and that's actually quite right. Today however, I wanted to try to program this Segway in NXT-G, because the current version of NXT-G (2.0) is relatively fast. It turns out that the Segway can still balance very well when programmed in NXT-G. It's a little slower, but it can still handle uneven terrain and small disturbances.

In the next week, I'll post some more updates, including the NXT-G program. Basically, all you need to create this robot is the HiTechnic Gyro sensor, any NXT set (any wheel size will work), and the NXT-G 2.0 software.

May 27, 2010

PSumo - want your own?

Some creations cry out out to you. They look so fun that it's hard not to bemoan the fact that 99% of them you will only ever see "virtually", on a web page, YouTube, or similar. Steve Hassenplug created a competitive robotic games that's a mash-up of the RoboRally boardgame and conventional robotic sumo, and it's been a hit everywhere it goes. The idea of robotic sumo is simple - your robot must defeat the opponent by incapacitating it or pushing it out of the ring. But that requires a lot of mechanical design, programming complexity, and testing. The idea of PSumo is to remove some of those hurdles, while preserving most of the fun. Instead of building a custom sumo robot, you build two identical ones. Instead of laboriously programming them, you swipe a series of "programming cards" over a sensor on the robot before the match begins - it's your selection of programming cards that determines how the robot will behave during the match.

I've had a lot of demand for some of my creations - but evidently Steve's had a little bit more for this one. In fact, he's put together a PSumo "kit" ($240) that has much of what you need to add to a standard NXT kit, together with instructions, software, etc., to produce your own copy of his PSumo game. Note this doesn't have everything - but it does have the harder-to-get components, as well as the instructions to make it all work together.

If you haven't seen this before, I'd recommend visiting Steve's PSumo page to at least take a look at what it is. It's not just an impressive feat of programming and building - but it's a really educational example of "packaging". While all the parts are there to experiment with and change any way you like, just like with LEGO in general, here's an example that does something, and does that something well, and is entertaining at the same time. In short, it's a good example of what a LEGO robotics project can be... for everyone (not just the builder).

May 26, 2010

New NXT competition

Received an email from Kathy Kent, Director of CyberKids Robotics:

Our organization is hosting a Nationwide Robotics Tournament to provide robotics teams with more practice time during the summer and to help teams prepare for the upcoming FLL Robotics Season. Our website containing all the information for the robotics competition is


If any of our readers choose to participate, please let us know - we'd love to post details about the competition and would welcome guest writeups.


Incredible GBC Video!

You have to check this one out!  Way too much awesome stuff to mention.

LEGO Festival at The Mall Athens

Here is some good news strait from Greece!!  Since the 19th of May,  the first LEGO Festival at The Mall Athens has started... Why post about it here you ask? well because a famous  Mindstorms master builder has helped organize the Mindstorms section of this huge event! Indeed NeXTSTORM can be spotted in the video below showing off his latest creation 3it3ot along with Alpha Rex, HoloEyedBug (his new holonomic bot) and many other NXT robots.


More good new? is going on till June 6th.  So jump in a plane, a train or out of the blue sea and head down to The Mall to play and enjoy all of the LEGO Themes and Mindstorms robots.

NeXTSTORM & Greek LEGO Market Officer

For more info visit
Visit for more of his projects & pictures.

May 25, 2010

Temperature Sensor Review - Dexter Industries

I mowed the lawn today. But we'll get back to that.

I've had the chance to play with Dexter Industries new temperature sensors recently. These are thermistor-based, and read as analog sensors by the NXT. There are two versions: the "O" or open version, which is essentially a bare thermistor for a fast response, and a "P" or protected version that encloses the same thermistor in a stainless steel sheath. Rated from -50° to 150° C (-58° to 302° F) they span just about any (un)reasonable temperature a LEGO user is likely to need, from dry ice to the average oven (I'm pretty sure the plastic coating on the cord would not handle that; don't do it), and reasonable resolution which varies with temperature but is as fine as 0.15 °F (the resolution is poorer near the upper & lower extremes). Dexter Industries provides NXT-G blocks to read the sensors that work very nicely - under NXT-G 2.0, the block provides better than 1° F resolution, and will output the measured temperature in °C, °F, K, and R (OK, I don't know who still uses Rankine, but it's kind of neat it's there). The steel-coated one doesn't fit nicely into LEGO geometry, but I found it easy to mount onto structures with a simple rubber band. The "open" or bare sensor is so small it's trivial to thread through LEGO pinholes & in fact can fit inside LEGO pegs themselves if you are careful.

I tested the thermal response of the sensors against the other standards I have: the old LEGO analog sensor, and the newer LEGO digital one. The first test was to simply chill all the sensors in icewater, & then plunge them into boiling water. Ideally the sensor should respond as quickly as possible, and the offerings from DI did fairly well. The "open" version had almost the same time response as the LEGO digital sensor, a characteristic time of about 4 seconds. The "protected" version wasn't nearly as fast, but still faster than the old-style LEGO sensor... and unlike the LEGO analog sensor, these sensors will go to much higher temperatures (note how the analog sensor "maxes out" before it reaches the proper temperature). Testing the sensor speed (or NXT-G block speed) was also informative: the blocks from DI are actually faster than the way I'm reading the LEGO digital sensor, and the old LEGO analog sensor is much faster than all others... but that's not actually very important. The fact that these sensors can be read so fast is largely irrelevant as the physical response time of the sensors is so much longer.

The other thing I tried to do was do a direct comparision of the sensors at the same temperature. Actually, I tried to do this for about three days, with little luck (the graph at left is one of the best runs... notice it took about 10+ hours of continuous measurement and sloooow temperature changes). The problem is not that the sensors are poor - in fact, they're (all) rather good. The problem is that first graph, showing response time. If the temperature changes, each sensor will respond at a slightly different rate, so even in the same environment, they won't always show the "same" temperature. By keeping all four sensors in the same water bath, and very slowly changing the temperature, I tried to correct for this, and at first glance at the graph it looks like all four tracked the temperature identically... but they didn't. In fact there were times that one sensor was as much as 4° F "out of alignment" with another. A 4° error? Hmm...

Is this a problem with the sensors? Well... no, actually. It's what you'd expect, given that even in a water bath, the temperature isn't the same at all points (convection currents), and if the temperature is changing, even a little bit, you should expect the sensors to respond differently. I wanted to mention it here because it's important to realize what the limitations of a sensor (any sensor) are... and that those limitations aren't always due to the manufacturer, but the essence of what you are measuring. Don't blame the manufacturer if you don't understand exactly how the sensor should respond.

I really like the LEGO digital temperature sensor - it's just about as fast as the best from DI, but with amazingly high resolution, and it's digitally corrected within the sensor, as well as protected. But... there are things these DI thermistors can do that the LEGO digital version can't. First, they're cheaper, which can certainly be a consideration. Second, they could potentially work over longer distances (I was grateful for the chance to play around with a "open" version with a 2 meter long cord, a meter longer than the NXT I2C system can easily handle and very useful). And third, their small size and flexibility allows the "open" version in particular to be used in places that would otherwise be impractical.

Remember mowing the lawn?

Here's where a small, flexible sensor can really shine. It's been hot here in Indiana, but I still had to head outside today to mow the lawn... and wondered just how hot I was going to get. Not how hot it was outside (easy), but how hot I would be working out there (hard). So I stuck the NXT in a little fanny pack with the LEGO digital sensor sticking out to record air temperature, and using advanced bioadhesives* secured two DI "open" style thermistors to my body in protected areas. The result was that I could log an approximation of my core body temperature as I was working, and see how fast it warmed and how fast it dropped again when I stopped & went indoors to the air conditioning. This is probably not something I could have done easily with the "protected" or LEGO digital probe... but it was easy (actually, not even uncomfortable) with the small flexible "open" sensor. And it showed a number of interesting trends, including my core temperature rising but dropping back down rapidly after I entered the house.

It's amazing what you can do with a simple set of sensors, when they are coupled to a flexible independant computer the size of your fist that can be programmed by a child :). Now, if I can just figure out how to rig a pulse monitor and respiration rate sensor...

*No, not duct tape. Rubber bands around my upper arm and band-aids.

Quarto! Game

I have never heard of the game Quarto! but it looks like a pretty neat game. What’s more is that YouTube user BlaMule has built a really cool robot to play and win the game against a human competitor.

There are so many things I like about this robot. First, I like that it is a fast mover; there aren’t many pauses and when it gets moving it doesn’t stop and wait. The second thing I like is that it is a polar robot rather than a Cartesian (x-y) coordinate robot like the first version. That adds some complications to the programming, but this robot handles them very well and seems to be very accurate. I also like the linkage movement meaning that the gripper extends when in the lowered position and is retracted when in the up position. That shows me that the creator had to figure out how that linkage would work which is a task in itself. I like how the end part of the arm is very lightweight and the gripper is controlled using the older Lego Flex parts, which I don’t see done very much.

Very nice build!

May 24, 2010

LittleDog from USC - Non LEGO

This is a non-LEGO post.  However, the level of autonomous locomotion of this robot is amazing... so I'm going to mention it here.

Just watch the video... the agility and ability to recover of this little 4 legged robot is amazing.

New NXT Book for Educators

Received the following from Chris Bracken:

I am pleased (and excited) to announce that after 2 years of research, writing, trialing and editing, “Educate NXT” is rolling off the presses at PITSCO (LEGO Education Nth America) for Worldwide distribution.

Educate NXT is a 275 page printed robotics resource (with substantial PowerPoints) for teachers and students. Teachers will find out how to successfully and confidently manage a robotics program within their school. It includes graded student worksheets, extensive teacher sections, animated PowerPoints and additional challenges. Educate NXT is designed to give educators control within the robotics classroom, yet fosters learning freedom and the buzz of student engagement.

I invite all current (and future) Robotics teachers to check out the Educate NXT website which gives a very comprehensive overview of this exciting new resource.

May 23, 2010

Coming Soon: Altimeter from Mindsensors

Once again LEGO-X has spotted an upcoming sensor... This time it's from Mindsensors and visiting their Coming Soon page  you can read about them making an Altimeter for Mindstorms NXT.
"With an Altimeter, you will be able to measure altitude above sea level."
Sounds like an interesting sensor for NXT projects such as HALE
I wonder what other ideas you may have for an Altimeter equipped robot?

(edit)  ...Found this post entry dating back to 2008 by Brian Davis

May 20, 2010

LEGO Universe Mode in LDD

On the eurobricks forum, I detected a useful tip on how to make use of a new feature in the LEGO® Digital Designer 3, called LEGO Universe Mode.
It's a new theme that allows you access to all the 1400+ bricks in the LDD database.

Read about the details here.

May 19, 2010

Brickworld 2010 - 30 Days 'Till Competition

Brickworld 2010 is rapidly approaching. If you've been, you know it's an incredible experience, getting together AFoL's from all over to share their amazing creations. If you haven't been... it's well worth the trip. With just 30 days to go preparations are in full swing, & I thought I'd mention a few aspects that might appeal to the Mindstorms crowd. There will be displays with the NXT there, and also some head-to-head competitions. There will be Robot Basketball (collisions on the field? So much the better), Robot Jousting (risk of NXT's hitting the floor? Always exciting), and even NXT sinking into the pool (a LEGO pool challenge... although not explicitly robotic, it certainly could be in the future). There will also be FLL style events, and lot of other fun things going on, including people to meet and talk to, and plenty of ideas running around... not to mention give-aways, prizes, etc. for full admission (and for those who can't be there the entire time, there's always the public days). Please feel free to check out the links and we hope to see you in Chicago soon!

May 18, 2010

BobBot Mk2

This cool bot is based on the BobBot (from the One Kit Wonders book, created by various authors here at NXT Step).

The bot includes:

It can handle these because of the Sensor MUX.  It's programmed in RobotC.  The HUD is pretty slick.  Gives you a good view of what is going on in the robot while it's running around.

You can see the details, and some videos, here:

May 12, 2010

Coming soon: Pressure sensor from Dexter

Joey, a young fan of LEGO Mindstorms who runs his own blog, was recently invited to test Dexter's upcoming sensor.  He wrote a nice article about it. I invite you to read it on his LEGO-X blog latest post:

Special! Datalog report for the new sensor from Dexter Ind. : dPressure

The NXT Step is often his number one source for news and information about NXT related things ...but not this time!  Well done Joey and thanks for your report.

Released: 3rd Party ROBOTC Driver Suite V1.4

v1.4 of the RobotC Driver Suite has been released. You can download it here: RobotC Driver Suite v1.4

Details of the release are found here at Xanders Blog.  

For those interested, I'm working my way through some of the RobotC examples that go along with the HiTechnic Experimenters Board.

My findings are found here:  Brick Labs - RobotC Tutorials and Examples

May 10, 2010

Back to the Basics... in Perspective

I wanted to link to a short YT video here, a version of Claude Shannon's Ultimate Machine. This is really an amazing mechanism here, and demonstrates in a small package some amazing mechanical techniques - techniques actually very commonly seen in a lot of "real" robots and industrial mechanisms, and rendered beautifully here in LEGO (the subject is also a rather famous robot of a sort). Note that this has no NXT in it. In fact, it doesn't even have a single PF motor in it. There's no wires, no programming, and the closest it gets to a MINSTORMS solution is that it uses gears:

So why the heck am I posting about it here, in a blog dedicated to the NXT?

One of the things that's easy to overlook when working with something like the NXT is that when you have your hands around a hammer, everything starts to look like a nail. The NXT is a powerful microcomputer, that can read multiple sensors and run lots of motors, and so there's a tendency to think that's the way to solve a problem.... any problem. That's not usually the case. Sometimes, mechanical solutions will work, and work better, than some complex programmed solution. Even complex robots often depend on intricate, imaginative mechanical tricks and aspects to work right. This often seems to get lost with people when they start using the NXT (or even advanced users), and it bears repeating - look for mechanical solutions and techniques in addition to, and to support, "intelligent" functions.

This was driven home to me recently in a post on NXTasy about a maze-solving robot. This user wanted to know (more to the point, apparently wanted working NXT-G code) for a robot that would use 3 US sensors to find its way though a simple maze. Some people opinioned that the language chosen was perhaps a problem. The thread originator had even gone out and worked out a detailed truth table type structure to solve the problem... but in the rush to make a functional solution, they had apprently not noticed that there was no need to use three sensors in the case they originally wanted - two would suffice, & as a result their proposed solution was a good deal more complex than it needed to be. And to this day, the best LEGO solution I've seen to this used nothing more than a single motor, some wheels and rubber bands... and easily beat every "robotic" solution tested that day in a fairly well-respected field of competitors, RCX and NXT-based, against folks like myself and Steve Hassenplug.

Yep, it's a robotics set. That doesn't mean it's always the solution are "more sensors, more motors, more memory, more speed". Sometimes, it means the best solutions... involve more thought.

May 9, 2010

Winners of NXTLOG's "Smart Move" challenge

The winners of the April-March challenge of NXTLOG have been announced.
The goal of "Smart Move" was to design a LEGO MINDSTORMS NXT transportation device of the future.
Have a look at the winners here or view all entries using the smartmove tag on NXTLOG.

Congrats to all participants!

May 7, 2010

NXT-G Programming Guide, 2nd Edition

Just a quick note - Apress is releasing a 2nd edition of my NXT-G Programming Guide in July. It covers both NXT-G 1.0 and 2.0, but it's been specifically updated to include the following:

* More sample programs - I've added 25 more sample programs (in the form of Exercises) at the end of most chapters. Each Exercise also has a solution at the end of its respective chapter if you get stuck.

* Coverage of 2.0 Tools - the 2.0 version of the software has some new tools (Image Editor, for example) - I've updated the book to cover the new tools as well.

* Fixed errors - there may be new errors, but I think I got the old ones fixed - and made some updates to some explanations that readers have asked me to go deeper into...

All in all, about 100+ new pages to the book... I don't have a final pagecount yet, but I'll try and post that once I know it... the book is in PDF review right now before heading to the printer.

And for those of you wondering if there will be any more NXT books like Mayan Adventure or King's Treasure - all I can say is Yes... more details will be coming. In the meantime, I've been doing some straight fiction writing (check out for details) as well as some tech books on non-NXT topics (here and here), so be patient with me - I've got a lot of projects going at once, but more NXT projects are planned.

May 6, 2010

Journey account on Atlanta FLL world finals

Austrian MCP Mike Brandl has published a travelogue of his six days sojourn at the FLL world finals in Atlanta in mid of April. Have a look at his site where you will find a lot of interesting photos and videos.

Besides, it's a good opportunity to see how some of the people that are posting here actually lool like... ;) 

NXT 2.0 Ball Shooter, Baseball Game

The NXT 2.0 kit comes with parts to make a ball shooter ("Zamor Sphere Launcher"), but it is not exactly obvious how to build a simple one that is controlled by the NXT, and the shooter on the built-in ShooterBot robot is somewhat strange and hard to transfer to another robot. So I have posted a design for a compact and sturdy Ball Shooter that is easy to attach to another robot:

Then I used this shooter as part of this new Baseball Game for NXT 2.0:

May 5, 2010

Review of some thermal sensors for the NXT

MDP Dave Astolfo has published a review of a set of Dexter Industries Thermal Sensors and compared them to the LEGO® Education NXT Temperature Sensor.
Have a look at the according page at

May 3, 2010

Back to Basics Advice?

Sometimes we forget that what is common knowledge for some is completely unheard of for others. So, I suggest we revisit the question of what NXT kit supplements we most recommend---and were to find them.

My top priority would be short NXT wires, which are available from The regular wires get in the way excessively.
(While you are there, check out their new Touch Sensor Multiplexor.)

If I only owned the NXT 2.0 kit, I’d definitely purchase some gears and the rechargeable battery set. The battery pack is available from the LEGO website. Gears can be found in large quantities from LEGO Education, or in any quantity from

No matter which kit you have, more of these are desirable:
Technic Beams with Snaps
Angle beams
Studless Technic Beams
The links are for the Lego Education U.S. site. They can also be found on and, I assume, other regional/national LEGO Ed sites.

Other recommendations from y'all?

This post has been edited for accuracy by the author.

Using an iPad for LEGO Building Instructions

So I got an Apple iPad recently, and I have seen the future... This a cool device, and it's good at many things. One thing that it is exceptionally good at is viewing LEGO building instructions, because you can have it with you right on the floor with your LEGOs, and it's interactive, connected, color, etc. It beats a laptop or a stack of books easily at this task. So I made a little video demo of using it in various ways for this (viewing web content directly, PDFs, eBooks, etc). This may be the future of education... Check it out.

May 1, 2010

NXT 2.0 Discovery Book now in stock on Amazon

The LEGO MINDSTORMS NXT 2.0 Discovery Book: A Beginner's Guide to Building and Programming Robotsis now in stock on Amazon. If you receive your pre-order, leave a message here. You may even receive it before the author sees his book!

Website with MINDSTORMS projects

I have been building MINDSTORMS robots for about five years now, and in this time I've created quite a few different robots. I have recently created a new website to share information about these designs. Only some of the 35+ designs on this website have building instructions, but the construction and design tricks may still be helpful to you. The link is here.

Using the EOPD sensor to measure distance

On the HiTechnic website, Gus Jansson has published an interesting article on how to use the HiTechnic EOPD sensor as an accurate distance measuring sensor. You can read it by following this link. (Thanks to Xander for the link.)
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