Feb 29, 2012

More LEGOWorld goodness

A few more videos from LEGOWorld Copenhagen.  Thanks to Menno and Robotica for finding them.

Feb 28, 2012

LEGO® in Space

Furukawa Satoshi, an astronaut from Japan on board of the International Space Station, these days built a LEGO® model of the ISS there:

LEGO robots in Barcelona

At Mobile World Congress 2012, Ericsson and LEGO Mindstorm partnered up in Hall 6 at The Social Web of Things and gave visitors a glimpse of what the future might look like if you had your very own R2D2. have a look here LEGO robots at ericsson mobile world event and see "snatcher" at work.

visit the show: February 27 to March 1 at La Fira – hall 6, Barcelona, Spain


Feb 27, 2012

Smallest NXT Biped ever!?

Michael has just sent us details of his recent creation, a tiny NXT based Biped called "My Very First Bipend" that won the SnapBots challenge over at NXTlog.

It's a great design and cleverly relies on momentum of the NXT brick to maintain balance.

More info and pics -

Can you make it smaller!? :)

PriNXT - NXT based printer

Nice NXT based printer from Leon Overweel.

Leon creates a design by first loading up an image on computer, converting it to black and white and then into 1's and 0's.  That array is then copied into a RobotC script that puts down the pen for the 1's and lifts the pen for the 0's as it scans along.  Nice and smooth, and great resolution of 50px by 50 px.

Leon has a comprehensive post with all the fine details.

(Thanks to Joey Kelly for pointing me to it!)

Feb 26, 2012

Building instructions for the NXT dolly

Some readers asked for building instructions for the NXT dolly, my NXT-based programmable camera car.
So here they are as an LDD file, alongside with a alternative attachment for mobiles.

New compass sensor from Dexter Industries

Dexter Industries have come out with another sensor for the NXT, this time a compass.

A compass is an excellent way of figuring out which way your robot is pointing.  Especially handy for things like navigating around or playing a game of robot soccer!

This particular one can measure along 3 axis (so I guess that means heading as well as tilt?)

As with all compass sensors, you need to be very careful around other magnetic fields (power cables, motors etc) but according to the manual, you can do some calibration to reduce any offset from true north.

At $29, it's one of the cheaper sensors available for the NXT :)

More details including code samples for NXT-G, RobotC and Labview can be found here.


(via Bot Bench)

Feb 25, 2012

Lego NXTified Friends robolab 3933

Take the LEGO Friends - Olivia's Invention Workshop (#3933) and add Anika a Mindstorms Robotics Expert... and what do you get?


This is just awesome!! I'de like to see this creation slightly raised on a mirrored floor plexiglass cube and let the public try it out at the next Mindstorms event.  Don't take it apart, it's beautiful!

 Girl... you inspire us all!

Feb 21, 2012

Awesome LEGO Robotic Arm

Max Shepherd has designed this amazing robotic arm. Learn more about Max's creative work---both moving and non-moving---at maxshepherd.net. Most impressive!

Feb 20, 2012

NXC programming language video tutorial for beginners

Youtube user GODLVESEVERY1 has made a serie of video tutorials about the NXC textual programming language. Check them out!

Feb 19, 2012

LEGO World - Copenhagen 2012

I was lucky enough to spend yesterday at LEGO world here in Copenhagen and got to catch up with some amazing builders.

Here is  very quick video I've put together to give a bit of an overview of the MINDSTORMS area.

Feb 18, 2012

Understanding NXT Sets, a detailed overview

In the past years I've received a lot of questions about LEGO MINDSTORMS NXT set versions. Here's an article I wrote which hopefully covers most of these questions. You'll find an overview of:
  • Overview of all three versions of the NXT set, and the differences in the included electronics
  • Links to element parts lists
  • Overview of Education base set and resource set (two versions)
  • Color vs. Light Sensor - which is in the NXT set?
  • NXT Rechargeable battery, what is it?
  • Upgrading NXT kit
  • Upgrading NXT "1.0" software
  • NXT Versions and NXT Books

Most of this is very basic information, but the variety of NXT sets and information can be confusing for new users and teachers. Especially when you buy a lot of sets for the classroom, it's important to know what you buy.

I'm not making any recommendations to what you should buy, I'm only collecting a lot of information in one place. Click to view article.


And a question to those who use the NXT-G education software: Can you use the LEGO NXT 2.0 Color sensor in NXT-G Edu 2.x? I'd like to add that to the information to the article.

Feb 17, 2012

Hispabrick event in December

The guys from Hispabrick (an amazing LEGO magazine), are planning a little event for LEGO fans in Spain.

From their website

We are happy to announce that HispaBrick Magazine will organise the event for LEGO® fans HispaBrick 2012 on December 7,8 and 9 in the mMACTEC (Museu de la Ciència i de la Tècnica de Catalunya), in Terrassa. Fans will be able to participate in activities and in the exhibition related to this construction toy.We will keep you informed.RegardsHispaBrick Magazine

 Looks like it'll be a lot of fun so save the date if you are in the area!

Feb 16, 2012

Small Ball Contraption

Not quite a GBC, (http://www.teamhassenplug.org/GBC) but a fun little machine none the less from Rob Torok.

New NXT Site

Recently I've begun moving all of my Mindstorms creations made in the past years to a new home - http://robotsquare.com/

I'm moving my old site to be able to better organize and archive my Mindstorms work. I'm rewriting some of my work as tutorials, to make it easier for you to remake some of the projects you'll find on the site.

Not all of the content has been moved yet, but you can have a look if you like. I'll still be blogging here, of course, don't worry -- My old site just needed an upgrade.

LEGOWORLD Copenhagen

One of the largest LEGO events in Europe starts today: the LEGOWORLD Copenhagen.

Until Sunday, there will be plenties of exhibitors showing off their LEGO® creations to the visitors. Also a lot of mind-blowing NXT stuff is to be expected again this year.
So in case you happen to be around Denmark or plan to go for a short-trip to Scandinavia - drop by!

We will try to get some on-site videos and reports from our friends being there.

Feb 11, 2012

NXTurtle 2.0 is alive!

I've been told by many teachers that my NXTurtle pet is beloved by children. That robot is described in detail in my book Creating Cool MINDSTORMS NXT Robots. Apart from walking and turning, the turtle can retract the head inside its shell. Since it is getting 3 years old by now, it was time to redesign it with the NXT 2.0 kit, giving birth to NXTurtle 2.0!
This new pet has an autonomous behavior, and a crazy new feature you will discover watching the video till the end.

You can download the building instructions and NXC programs for this robot from here.

Daniele Benedettelli: 10 years of LEGO® MINDSTORMS

Daniele Benedettelli, famous NXT dottore from Italy and creator of many cool robots, has completely re-designed his LEGO® MINDSTORMS web site.
Amongst a heap of fantastic robot creations and links to his various books, you will find a short video there; it not only reflects the self-assurance of a true NXT genius but also the achievements of 10 years of dealings with MINDSTORMS:

Feb 6, 2012

The horse shoe crab from Fay Rhodes' "One-Kit Creatures"

Some weeks ago I built a customized version of the horse shoe crab from Fay Rhodes' great book "LEGO® MINDSTORMS NXT 2.0 One-Kit Creatures". Today I have taken the time to produce a small video on it:

Feb 4, 2012

A Plethora of Pressure Sensors

It used to be there were very few ways to sense air pressure with the NXT… but over time a number of different companies have come out with third party pressure sensors for the NXT. It’s something that I’ve been interested in for a while: I’ve used pressure sensors for determining altitude during hikes, monitoring high-altitude balloon flights, technical geyser investigations, and lots of other things… so it seems natural to try to compare some of the sensors currently out there in the NXT market. Warning – this is my own personal testing and opinions. It may be wrong. And in the interest of full disclosure, most of these companies have been extremely helpful to me by providing sensors to test and responding to feedback… but still, this is as closeas I can come to an unbiased position. I have pressure sensors from four companies currently: HiTechnic, Vernier, Mindsensors,and Dexter Industries. All of them interface easily with the NXT, using NXT-G blocks, NXC code, or other drivers. Most of them (all except HiTechnic’s) can be “plugged in” to an air line like the LEGO pneumatic tubes or standard aquarium/sized tubing, which is handy for a lot of things. For this I tested all of them under NXT-G 1.0, and used whatever way seemed best to get the highest resolution readings I could from the sensors (sometimes using manufacturer-supplied blocks, sometimes reading the sensors in a “raw” format, etc.). So, without further ado… here we go.

A comparison of four sensors all on the same NXT, attached to the same manifold. I could pump air in and out using a pump based on a large syringe with two one-way valves. First the pressure was reduced (you can see the individual pump cycles in some cases) and held low, then the seal was broken to bring the pressure up as rapidly as possible, before the same pump was used to increase the pressure.

A detailed graph of the very first depressurization event, showing how the four different sensors respond to a sharp change in pressure. The Dexter Industries sensor was not involved in this test (due to software issues), but was tested and is described below. Notice how the Vernier Barometric sensor (purple line) stops dropping even as the pressure continues to be reduced, "bottoming out" at the lower end of its range.

Dexter Industries dPressure250 and dPressure500:


Cost: $28 for the 250 kPa version (up to 30 psi), $32 for the 500 kPa (70 psi) sensor.

Response time around 1 ms, analog, stated resolution of 250 Pa, although this varies across the range slightly (sensor reads all the way down to at or very near 0 kPa). The only true differential pressure sensor, with two ports (one for “negative pressure”, one for “positive pressure, clearly labeled”), this is the only sensor that can do an on-the-fly comparison of the pressure in two separate systems of tubes (if you want to build a Pitot air-speed sensor, this is the sort of thing you want. Non-linear response really makes it easiest to read this with the stock NXT-G blocks (but I couldn’t do this under NXT-G 1.0, this was not tested equally to the other sensors here). The 1/8th inch ports are easy to use (if small for some uses). This sensor reads fastest of all in this review, as it is can be read as a simple analog sensor (with a light sensor block, for example) once every 7 ms, although the sensor seems to have a longer physical lag time than that so it is not “really” as fast… but it’s still faster than any other sensor it seems. The biggest drawback may be the low pressure resolution… while fast, this isn’t as detailed as the other sensors here. The dual ports however are a unique feature that may be exactly what you need in some cases. Some care needs to be taken with the bare circuit board design style, but the sensor element itself is well mounted and I had no worries about it breaking off.

Vernier Gas Pressure sensor:


Cost: $83, (but you need to use $39 Vernier adaptor as well, potentially making this a $122 sensor)

Very fast response (purported to be 0.1 ms, but there’s no way to verify this on the much slower NXT). Reads from about twice atmospheric pressure all the way to zero (range of 210 kPa to 0 kPa), with a measured resolution of 240 Pa (note that Vernier lists a much higher resolution almost 5000 times better… but this isn’t available using the NXT’s internal analog-to-digital ability). Damaged above 4 Atm (60 psi or 405 kPa), this is a sensor that can handle high pressure and give you reasonable accuracy, considering the range. As an analog sensor, can be read as fast as any other (about 7 ms in my testing set up), but using the Vernier stock blocks it takes slightly longer at around 9.5 ms. The provided tube rapidly twist-locks to the sensor, and has a good valve and a universal adaptor at the end common to chemistry and physics departments (almost certainly the best supplied tubing set-up of the bunch, a feature shared with the sister Barometer sensor below). While the sensor housing is bulky, the long cables (this is an analog sensor) allow it to be used in a variety of situations… although for exactly the same reasons, using Vernier sensors with small mobile robots tends to be a problem. The very linear response, and high speed of this sensor are fantastic… but you certainly have to pay more for that. It should also be noted that there’s a reason for the higher cost… the Vernier sensors have very high resolution compared to the others here, but Vernier has never come out with a stand-alone AtoD converter that would allow the NXT to access this. I keep wishing; a basic 16-bit AtoD reader would make these (and a host of other analog sensors) potentially much higher resolution, really justifying (for NXT users) the higher cost. Does anyone at Vernier read these J ?

Vernier Barometric sensor:


Cost: $71, (but you still need that $39 adaptor, making the effective cost perhaps $110)

Again, very fast (on the order of 1 ms) response time. Almost identical to the Vernier gas sensor in look and function, but with a higher resolution (and more range-limited) sensor inside (everything I said for the cables, form, and tubing supplied with the Vernier gas pressure sensor holds for this as well). Instead of reading from zero to a high pressure, the sensor is limited from a lowest reported pressure around 84 kPa, to a highest reporting pressure of about 121 kPa… but that means over that range (about 80% of normal pressure up to 120%) the resolution is much better, around 25 Pa (again, it could be better… Vernier claims this sensor has resolution at the level of 1 Pa or so, but you can’t get this with the NXT’s lower resolution AtoD conversion). This comes with a caution – the sensor can be broken if subjected to more than around 2 Atm (203 kPa) pressure, so this is not a sensor for high-pressure environments… but for detecting small rapid changes at or near normal pressures, it’s hard to get better than this, period. Again the tubing kit, valve and adaptor are superior, and very handy. This is probably my most frequently used pressure sensor… but I must admit it comes with a large pricetag (note: this is one of the sensors I had to spring for myself… and even at the over $100, I’ve never regretted it. Your mileage may vary).

Both these Vernier sensors require an adaptor to interface with the NXT:


Cost $39

Bulky with a long cable. Not for compact mobile robots, but used with all Vernier sensors, so you can at least swap it in and out of different experiments (i.e. – no need to get one with every Vernier sensor you own… you just need one for each port that’s going to be hooked up to a Vernier sensor. And Vernier has… a lot of nice, unique, sensors).

HiTechnic Barometer NBR-1036


Cost: $55

Very slow response… while the sensor can be polled rapidly (once every 16 ms or so), the response to changes in pressure (as can be seen on the graph) is much much slower... not in 10’s of milliseconds, but in tens of seconds! Actually, for a barometric sensor, designed to respond to slow changes in pressure, this is the sort of response you want – the sensor is averaging out all sorts of short-term changes & noise to give you the best estimate to the true, ambient, weather-related pressure. On top of this the sensor also returns the ambient temperature (the only one in this review to do this), so in a real sense this is a “two for one” sensor, still taking only one sensor port. It is also fairly high-resolution, returning the pressure at a 10 Pa level (as HiTechnic claims, and is demonstrated by testing), better than any of the above. It can do both these things because it is not an analog sensor, but a true digital sensor, retuning information to the NXT via the I2C interface. On top of this the NXT-G block has been designed to make it very easy to interpret the pressure changes as elevation changes, making this the most transparent “digital altimeter” available as well. The next time I go hiking and want to log my elevation changes… this is likely the sensor I’d turn to. The casework is the standard high-quality HiTechnic model, LEGO-certified and indistinguishable (except for a small label) from any other LEGO sensor. For fast responses, this isn’t the sensor to get, and it can’t be easily connected to a tube or pipe to measure those sorts of pressures (the only one without a port of some type, probably related to being LEGO-0certified in LEGO-certified casework). But a really nice sensor for weather & altitude related measurements.

Mindsensors PPS58-Nx


Cost: $40

Rapid response, about 16 readings a second… but testing reveals that it will actually read the sensor much faster than this, returning a cached value off the sensor until a new updated pressure reading is available internally. So, what’s the “real” response time? If you are worried about how long reading the sensor “stalls” your program, it takes only about 16 ms… if you are worried about how fast this sensor can report a change in pressure, the answer is closer to 60 ms (about 16 times a second). If you are worried about how fast mechanically the sensor system responds… it’s even a little bit slower than this. If you look at the response comparison, you can see that this sensor takes some time (about a second) to reach the new pressure during a sharp change. So the “real” response time here really depends on what you are curious about… a common problem when discussing things like sensors. The sensor measures from 0 up to about 58 psi (0 to 400 kPa) very nicely, but as an I2C sensor this one, like the HiTechnic version, can have a high resolution: by reading the raw sensor output, it can actually measure the pressure to about the nearest 2 Pa (not exactly like the 1 Pa resolution mentioned in the website… but still amazingly high resolution, and it may have been due to how I was reading the sensor). In more common terms, it can detect a change in atmospheric pressure of just 0.002%, (equivalent to determining a change in depth beneath the ocean of a tiny 1/5th of a millimeter!). This is a ported sensor, and is packaged using the Mindsensors now-standard “doubled circuit board” approach that protects the components inside while making a very strong “sandwich” structure that’s perhaps more robust for damage (note: I’ve always worried about static damaging these exposed sensors… but I’ve yet to have it happen. Perhaps I worry too much). For the highest-resolution measurements on the NXT, this seems to be the best sensor available, and while not the fastest response, it’s a close fourth behind the three-way tie for first in this review.

The Conclusion

If you’ve bothered reading this far, you probably want to simply know “which should I buy”. So, here’s your answer:

I don’t know.

I’ve tested these sensors and used them in a lot of different ways. In robots, altimeters, weather stations, and physics experiments. Weighing objects, determining water depth, and analyzing how a balloon inflates. Each of these sensors has strengths and weaknesses, and which you want really does depend on what you need it to do. Do you need the least expensive (Dexter Industries is the lowest cost option on the market right now)? The fastest (Dexter Industries or Vernier sensors)? High-resolution that’s got a response of a few milliseconds (Vernier)? Ultra-high precision (Mindsensors)? Pressure & temperature at the same time, in one compact sensor (HiTechnic)? Something else? If you want the right sensor for your application… you first have to understand what your application is.

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