Jul 31, 2008
The Scholastic Store has provided a %20 Off coupon code for a new NXT Retail kit. I'm not sure how long the coupon will last, but if you need an NXT kit here's what you do:
STEP 1) CLICK HERE to open the NXT product page.
STEP 2) Add an NXT to your shopping cart and click "Checkout Now".
STEP 3) On the "Order Review" page (last page of the checkout process), copy and paste this coupon code MOMSVIEW (All Caps!) into the box "Promotion Code" - then click the "Apply Promotion" button.
STEP 4) You should now see the discounted price of $199.96 USD.
The shipping costs are very reasonable. Enjoy! Chris
Jul 30, 2008
They all seem to be intact. FLL Team 90's payload is the third one from the left. It looks like the UV filter pinwheel ( an old CD case) had survived the trip. Although, I'm not sure what is dangling from the corner of the box. The pinwheel may have caught some of the balloon shreds on the way down.
The kids produced a nice little document of the FLL Team 90 Payload internals here.
I am confident that the team will learn something about Earth science and Global Warming through this program. We are treating our participation as a FIRST LEGO League research project for the upcoming season’s challenge, so I expect that the team has learned how to seek out the advice of experts in the field, came up with their own solutions through experimentation, document their work and had lots of fun in the process.
Thanks to Eric Wang, Brian Davis, Dave Parker, and others for taking the time to answer the kids questions. Please feel free to browse the google group discussion list for the FLL Team 90 and other topics.
Payload Coach - FLL Team 90
Up to now, the biggest draw back in using MS Robotic Studio for me has been the lack of on-board support for the NXT. This means that if you want to give your NXT robot autonomy, you need to embed a Windows Mobile device (or a laptop) in the robot to control the NXT (via Bluetooth). However, it did not stop me from spending a lot of time and effort over the last 12 months learning to use it.
So when Microsoft announced the new CTP (Customer Technical Preview) version this week, I decided to try it out.
So far it seems to be pretty good.
The new version will be called 'Microsoft Robotics Developer Studio 2008'. So they have moved away from the V1... V1.5... to 2008 to be consistent with the Visual Studio product family.
Incidentally, the new version is compatible with the new version of Visual Studio 2008 family - which is needed for it to run. It also works with the free version of Visual Studio 2008 (express edition)
The free download is available here.
There are a lot more new samples as well - the one that caught my eyes are:
- The XBox Controller Viewer sample shows support for use of interactive Silverlight-based UI
- Some really cool simulation samples
If you are Visual Studio developer, you would appreciate the new Visual Studio Project Wizards - rewritten to make it much simpler to create new service projects
directly from Visual Studio 2005 and 2008. The product also boasts faster compile time and the new DSS Log Analyzer (new debugging and monitoring tool that can visualize and analyze message exchanges between services sent between NXT and other nodes.
Why not give it a try? I must warn you it is a bit overwhelming at start if you are not used to the Microsoft developer tools - but given the popularity of the MS developer platform, it is definitely worth a try.
Jul 29, 2008
9:52 EDT, 6:52 PDT: LAUNCH! Balloon #2, carrying an SLR camera payload, FLL Team 90's payload, the LEGO Mindstorms Team's payload, Gypsy, Lil' Joe, and the "NXT" communications payload just launched from the Nevada desert! Everything looks good at launch, although conditions have gotten slightly windier... but it's going up! Next launch in perhaps 30 minutes or so.
10:41 EDT, 7:41 PDT: LAUNCH of Balloon #1, carrying LUXPAK, Brix-Catcher, Peeps-in-Space, a ride-along student payload, the National Instruments video camera payload, Reel-E, and the "Energizer" communications payload. the team has immediately departed for parts NE, as the first balloon has already reached more than 72,000' and is well downrange. The SPOT transmitters on the first balloon have cut off as designed at 40,000'; they should resume transmitting when they drop below that, Lil' Joe first (planned cut-down at 80,000' or so) and later the main balloon payloads. The first balloon can be tracked using the ham link in the above post, while the 2nd balloon has not yet come within line-of-sight of a repeater tower (but should soon).
10:54 EDT, 7:54 PDT: Lil' Joe has been commanded to be cut free from balloon #2 at an altitude of slightly above 80,000'. If the program is functioning as intended, the freefall may be as long as 80 seconds, but Lil' Joe will set it based on the time aloft. I'm not sure what the ground underneath looks like yet, I'll have to check. Balloon #1 has started reporting in via ham radio as well, already above 21,000'.
11:14 EDT, 8:14 PDT: Balloon #2 now over 99,000' in altitude, approaching expected maximums. Balloon #1 is over 40,000' and ascending. All SPOT transmitters now silenced, as expected by altitude. The next SPOT transmitter message would likely be Lil' Joe, although the timeframe is very uncertain.
11:17 EDT, 8:17 PDT: SPOT contact from Lil' Joe timestamped 8:15:50 AM. This means the SPOT has continued functioning during the descent, but since there is no altitude information there is no way of knowing if the parachute has deployed. This is as planned (or hoped for, take your pick... Can You Tell I'm Nervous?!?)
11:34 EDT, 8:34 PDT: At a timestamp of 8:25:13, the Lil' Joe SPOT transmitter sent another location update, the same location update as the one at 8:15:50 AM. This means that Lil' Joe is below 40,000' and not moving... in other words, on the ground and with a working SPOT transmitter. It seems that the free-fall payload has made it safely to the ground! Balloon #2 (the first launched) has popped and is on it's way down (I'll look up the peak height in a minute), and Balloon #1 is still going up. According to Eric, they passed within a couple miles of each other as #2 was coming down & #1 was going up, so there is at least a small chance that one payload may have photographed the other, which it would seem like is another first.
11:56 EDT, 8:56 PDT: the last report from KE7BQV was over 30 minutes ago, from an elevation of 17,000' on its way down. This is expected, as the transmitter drops below the line of sight to ham repeater stations. The implication is that Balloon #2 (the first one launched) is now on the ground, and the ground teams are heading out to retrieve it using the last known GPS position. Balloon #1 (KD7UCE) reports an altitude of almost 82,000'. Lil's Joe's SPOT coordinates show it in a flat area below 4,000', so it should be relatively easy to retrieve.
12:29 EDT, 9:29 PDT: Both Lil' Joe & the first balloon (KE7BQV) are now down, actually fairly close to each other. They're SPOT transmitters have continued to send back data that shows both payloads stationary. The second balloon (KD7UCE) has not reported in via the ham GPS system in more than 40 minutes, but it recently send back two locations via its SPOT transmitter, showing it is still in the air and moving. The elevation isn't known (the SPOT system does not transmit this), but if the SPOT unit is reporting it should be below 40,000', so it may be on its way down.
1:05 EDT, 10:05 PDT: Just got a sat-phone call from Eric - Lil' Joe has been retrieved! Well, sort of... it was located just 2000' off of a road (or what could loosely be called a road in that area), but it appears the parachute tangled with the tailfin assembly at some time (I did a quick calculation & found a higher-than-expected descent rate based on the cut-down & on-ground times, so I knew it had been a fast descent). The impact was hard enough to eject the inner mechanism straight through the bottom of the payload shell (inch+ thick blue stryofoam)... yet the SPOT was working. And so was the NXT! I'm not sure what data will be on it or what other damage it might have suffered, but it seems that it can survive a... rather high-speed... impact into the desert floor when released from 80,000' (yes, I want pictures as well)! Clearly some redesign is needed for the next time (like cutting free the tailfin altogether), but it works, and the NXT survived! The team is heading north to where the SPOT unit shows the next payload (Balloon #2), and Balloon #1 has recently reported in with two consecutive SPOT readings that show it stationary as well, so at this point all three payload strings are on the ground and reporting their location! The ground team may have some weather to cope with (and there may be clouds in a lot of the pictures), but it looks like a very good mission at this point.
2:20 EDT, 11:20 PDT: The ground team has now begin hiking up into the hills where Balloon #2 landed. I can actually see this "as it happens", because of the rather amazing survival of the Lil' Joe SPOT unit; the team is carrying this unit with them, and so it shows up on the map along with the other payload locations. Balloon #2 is located only a couple miles from where Lil' Joe landed, only about a mile from the road (although I've been advised that calling this a "road" is extremely generous) but apparently up some hills or terrain.
2:45 EDT, 11:45 PDT: The ground team has reached the second payload to be retrieved, Balloon #2, in some more interesting terrain as shown on the map ("canyoneering" was a phrased tossed about). They report all is well except for one payload that is missing from the payload string (I'll try to get details later, it was not a great connection, & I'm not sure which payload it was). I do know that Gypsy and the pipe framework supporting it survived, so on top of LEGO surviving incredible falls from 80,000', it can also support an active, moving payload, with the only connection being normal ABS (no glue!) exposed to -60° C or lower temperatures. Very impressive! More details when I get them.
3:59 EDT, 12:59 PDT: The ground team is now hiking out to the third and final payload, Balloon #1, and should reach it shortly.
4:22 EDT, 1:22 PDT: In what I'm certain is a long day for the ground team, they have retrieved the last of the payloads: all three returned missions (Lil' Joe, Balloon #2, & Balloon #1) have landed and been recovered safely. The missing payload mentioned before seems to have been the LEGO Mindstorms team payload (no idea what happened to it at this point - Eric reports it simple "wasn't on the line" when they found the payload string). He also had some numbers to give. According to the GPS units riding in the balloon payloads, Balloon #2 (the first launched) reached a peak altitude of 99,730', while Balloon #1 (the second launched) reached just a hair lower at 99,566' - a wonderful altitude for both payload strings! Gypsy was still running when recovered (in fact, it wouldn't shut off for some reason, and had to have the batteries removed) and had noted on the LCD that it had detected free-fall and switched over to the descent imaging script. The SLR payload took 18,888 pictures (yes, I got that right) all in raw format (16 Gb of data!), and the NI video payload evidently got the entire mission, hopefully including the balloon burst. The team is now returning to home base, and will start downloading data as soon as possible. I think it's appropriate at this time to declare the first HALE mission a wonderful success (although there's certainly some unexplained issues to address still, with several different payloads).
Personally I want to give a huge thanks to Eric Wang, Jeffrey LaCombe, and their entire team for putting in an amazing amount of work on this, from start to absolute finish (& they're still not done - drive safe, ground team!), as well as the sponsors for HALE, including LEGO, Energizer, National Instruments, The University of Nevada-Reno, and the Nevada Space Grant. Thanks for an amazing opportunity... and now to dig through the data!
(very happy near-space mission specialist)
In order to handle the photographic challenge, the program uses the same approach as the original Nadar: following a script. It reads a series of timed commands from a text file (think of it as a “photographic program” that Gypsy follows), executing each command (“take picture”, “turn on video”, “tilt platform”, etc.) and then waits a specified time until it reads & executes the next command in the file. This way the programming code for, say, “turn on the camera, take a picture, and turn off the camera” only needs to appear once in the program – it is just invoked every time it’s needed, saving huge amounts of memory over a simple “string of Motor blocks” style program (for comparison, several hundred still photos and five videos, with numerous repositionings of the pitch of the platform, take only 0.4 k of the NXT memory when stored as such a “script file”).
To deal with the simultaneous issue of datalogging, the program uses a similar system of “timed events”. The same loop that handles waiting for the next timed camera command also checks if, for instance, two seconds has elapsed since the last pressure & temperature logging – if it has, it logs the current pressure/temperature, and resets this timer as well. This same process occurs (with varying timed intervals) for engineering data, heater checks, etc. There’s no reason to do these in multiple parallel sequences… after all, most of the time all these would be just sitting around “waiting” for the right time to elapse. So instead, they all sit in the same loop being checked in series. This means the program can execute faster as well. The internal temperatures and the state of the internal heaters are also handled by this “timed event” strategy, so the program is fairly easy to troubleshoot – most of the sections are working the same way.
There’s a lot of data to record as well: ambient pressure, three different temperature sensors, external light level, the angle (or pitch) of the platform, NXT battery voltage, when each picture was taken (& if it was a picture or video), when the platform angle is changed (& how loud the motors sound during this event, as well as the background noise level, and how loud the NXT “Beep” sounds at this point as well), the two-second average acceleration and sound level, etc. To put as much as possible into the datalog, all this information is “compressed”, using a very simple data compression scheme coded up in NXT-G, that packs information about twice as dense as a text file “normally” would. The bit that does the datalogging and data compression is all in a self-contained My Block to make things easier – you wire in the information, and it handles writing it to the file, opening a new file if the old one is full or flawed, timestamping it, and compressing everything.
On top of all this, the program can switch to a different photoscript just by changing a single variable. Taking advantage of this, when the program detects a free-fall event (like when the balloon bursts), it will switch photographic scripts, as well as change the frequency of datalogging certain variables, so it can adjust its behavior under its own control during the mission (hey, otherwise it’s not a robot, right?).
How big is this complex, multi-tasked program? Remember, I need to save as much space as possible for datalogging all the information from this multi-hour mission as well, so size is critical. Well, it turns out on the NXT it occupies only about 20k – under 20% of the available memory. The “secret” (if that’s the right word) is that I simply reuse code – I do not follow the more common “string of Motor blocks” style that often gets used in many NXT-G program I’ve seen. The result is a program with 25 different My Blocks, interconnected and repeatedly calling each other on multiple levels, instead of 250+ individual Motor (and other) blocks, each of which I would have to set up, and each of which would take up memory. The result may look complex when diagrammed out, but it really isn’t… at least no more so than a "normal" NXT-G program. After all, you don't have to understand what LabVIEW routines are called when you use a certain NXT-G block, or what machine language commands each of those LabVIEW commands is translated to later. In short, I’ve just followed the example set forth by the folks who designed the software – make it modular, and built on things you already know work. The result was the program was “written” in about two days, with about a week of testing (because each testing run had to last something like 2-4 hours).
Please note this is not because I’m a genius, or that I’ve deep insight into the minds of programmers (I’ve never had a programming class in my life), or anything like that. I’m just following where a modular language like NXT-G leads me… and curiously, it’s led me to write code that is far more modular and compact than I ever ended up doing in text-based languages.
OK, that’s it – tomorrow is the launch, and we’ll see what works (hardware, software, etc.)… and what doesn’t. Cross your fingers… and watch the tracking links on the HALE website to see where these payloads are going "as it happens". I'll also be blogging on this tomorrow during the actual mission.
Jul 28, 2008
Note that on mission day, there should be live tracking of both balloons as well as Lil' Joe. The Balloon radio payloads will transmit about once a minute (and will include altitude data), while the three SPOT units will transmit about once every ten minutes, and send back no altitude data (they are there for payload recovery, not primarily airborn tracking). I will be following the mission in detail as well as possible from home, (& blogging it), but you can as well by following the links on the HALE website.
PS- The first picture is all or most of the payloads staged for launch - can you figure out which is which?
Now, if you have a missing part or two in your new kit, you can order them online--a more convenient option for most of us.
Last year, we lost one of the instruction manuals for our NXT set. Previously, replacing the missing manual would have involved calling LEGO and waiting for the manual to arrive in the mail. Now, you can just download replacement manuals from LEGO's web site, including the NXT's main manual and the "quickstart" manual for the tribot.
The link to LEGO's new customer service site is
It's hard to believe, but next month most teams are going to start receiving their FLL robot kits plus the mission mat and models... and then Sept 5 will see the release of the rules for the new season and its theme, Climate Connection. I hope all of you are excited and ready to get going! Jonathan and I want to wish all of you luck in the upcoming season, and we hope you enjoy every minute of the experience. As always, we love to hear from our readers about their FLL teams, so feel free to share pictures, comments, etc. Just like last year, we'll be offering a breakdown of each new mission with plenty of discussion in future blog posts - keep your eyes open for them.
Now, as for our new book, FIRST LEGO League: The Unofficial Guide, I have been receiving your email questions about it and wanted to post replies in one post rather than individually, so please check out the Q&A below. (I've edited some questions for length...)
1. When will the book be released? - August 20, 2008 is the shoot-for date and I'm told the printer is on schedule.
2. What does the book cover? I've finally managed to get an accurate Table of Contents that you can download and check out here. It's a 5MB zip file that contains a single PDF file.
3. Where is the best place to get it? Bookstores should be carrying it, but Amazon.com is a sure fire best. Also, please check out this post regarding a discount that No Starch is providing - definitely a nice savings (only good thru Oct 1) if you're willing to buy 4 or more books (any No Starch titles).
4. Does the book provide building instructions for robots? No. Sorry. We do provide some sample robot attachments and programs for performing certain tasks (such as using a specific sensor) but we do not (and cannot) provide solutions. Besides, that would take the fun away from FLL, wouldn't it? We promise that the sense of accomplishment you'll get from building your OWN robot will beat anything we can provide to you.
5. Does the book provide any programs? Yes. The book's download section will contain all the .rbt files seen in the book once the book is released.
6. Is there an electronic/e-book version? Not sure yet - but I'll be checking with No Starch on this and post an update soon.
7. Can I get you and Jonathan to sign my book? Jonathan and I are happy to sign your book if you hunt us down at any gatherings we attend (World Fest, for example - I'll also be signing copies at Botoberfest in Atlanta in Sept 2008), but please PLEASE don't send us copies of your book - return postage is expensive PLUS we don't want your book to get lost in the mail. In place of signing your book, we've come up with a different solution: Once the book is released, we'll be posting a bit of info on how to obtain a bookplate (a sticker you can place inside the book) that Jonathan and I will sign. The bookplate will look like the image seen here and there will be limited quantities. (All we'll require is that you send us a self-addressed/stamped-envelope (SASE) so we can send the bookplate back to you.) More info to come...
There's also one other cool item in the book - Dean Kamen wrote a letter for us that is being included in the book - if you attend World Festival (or any event where Mr. Kamen is present), hunt him down and get him to sign the letter for you. He's very nice and approachable and can usually be found signing all kinds of things.
8. I bought the Robotic Competition Workbook (here or here)- does it have the same stuff as this book? No. Jonathan and I wrote the RCW over a year ago and it's when we realized there was SO MUCH MORE stuff that needed to be covered. The workbook also was heavy on worksheets that an existing team could use whereas the book doesn't use a worksheet approach. There is a very slight overlap of the workbook and book and it's mainly found in the attachment section - but the book goes into a LOT more detail, including sensors in the discussion. A few more differences:
* The workbook has a section on scheduling not found in the book - basically how to examine how much time your team has left before a competition and figuring out how to use it to your best advantage - uses a worksheet
* The book focuses on putting a team together and organizing it (plus integrating new members into an existing team) that isn't found in the workbook.
* Workbook is 99 pages, 10 of which are worksheets that can be photocopied (or downloaded)/
* Book is 219 pages, a few worksheets that are downloadable.
90% of the workbook is completely unique material, not found in the book - and vice-versa. If you've purchased a workbook, definitely check out the Table of Contents mentioned above (Item #2) and see what you think.
9. Any freebies with the book? Besides the bookplate (if you want it) and the downloadable .rbt files, we've also set up a discussion area in the forums for the book - Jonathan and I will be checking in regularly to answer any questions, but you'll also hopefully find a lot of other people offering advice and assistance... we want to make sure our readers get their questions answered (if we can't answer it, we'll do our best to track down someone who can). One of the freebies you can go ahead and grab now is a worksheet I created for some local teams (Atlanta) that help them with brainstorming and testing the various missions - it's a PDF file with instructions and you can get it here.
10. What other FLL resources have you created? Search the blog using "FLL" as the keyword and you can find all kinds of posts from our archives. If you have any team members who want to document their experience with pictures, notes, etc, there's a 40 page Competition Journal (sample pages/excerpts here) with space for pictures, screenshots, autographs, notes, and more. I guess our question for you is: What do you need?
If you've got any additional questions, please post as comments and we'll do our best to get you an answer...
Jul 27, 2008
Using a LA with a NXT kit is pretty intuitive. Just plug in an axle of a NXT motor (or a Power Function (PF) motor using the NXT adapter cable) to a LA. Write a simple program in NXT-G to drive the motor. I will post an example program in NXTLog ASAP. Programming does not need to be very precise as to the number of rotations - I did it long enough to do about 28 rotations to extend the LA fully - and it works fine. If you put too many rotations, the internal clutch handle it pretty well as you can see in the video below.
Here is something I knocked up within minutes of opening the box with a LA using a PF motor and a couple of gears and a NXT. I also used the bracket that came with the LA to make the connection easier.
Here are the two models that has a LA: 8294 (telescopic Extender), 8295 (Excavator).
Below are pictures of the robots that the kids built, plus photos of their actual science fair display. The web site describing their project is
Jul 26, 2008
There are many uses for linear motion in a robot. In simplest form it could be flexing of a robot arm or controlling the bucket of a bulldozer. More complex examples might involve shifting gears in an automatic transmission or activating a trigger.
We are going to look at three simple ways to create linear motion using a motor under NXT control:
Linear motion Using Levers attached to a spinning motor:
This is really simple and the most common way a linear motion is created. Implementing is very easy with parts available in a NXT kit. Here is a video of how this works:
Creating your custom actuator:
It is pretty straight forward to create a custom actuator like the one below - it can be made with components that comes with aNXT kit - such as two worm gears and the TECHNIC pulley that acts like an inverted corkscrew.
When the motor turns the two worm gears, the pulley travels in a linear fashion. Here is a video of one of these in action in a Zamor Ball firing mechanism. You can see more about this in NXTLog.
In the final part of this (hopefully this Monday), we will look at how to achieve linear motion using the new Linear Actuator.
Thank you to everyone that has taken part in the recent contest to design and build a robot for an industrial application. The response to the contest exceeded my expectations, and for several weeks it was a challenge just to keep up with all the excellent questions from all the designers!
I met with several members of my company to review the design submissions, and I wish you could have seen the reactions of the group as they watched the videos, reviewed the CAD designs, NXT programs, pictures, and all the material that we received. Most of the review panel was made up of seasoned engineers and industry veterans, and they were all completely impressed with the level of professionalism and ‘out of the box’ thinking that was displayed. Our company is very supportive of creative ideas and collaborative thinking, and this project definitely extended our pool of creative thinkers!
We judged all the submissions on these criteria:
Robustness: Will the robot be able to withstand the rigors of a factory environment, and be able to run continuously? Was there a 24 hour test conducted and reported?
Presentation: Did the designer submit all the necessary items (Video of a working robot, CAD drawings, Build Instructions, NXT program)? Was there a WOW factor?
Repeatability: Does the robot deliver the required amount of pellets in the specified timeframe? How much variability was there?
Quick Change: Can the pellets be changed from one color to another easily, or is there some manipulation required?
No Spills or Contamination: Do the pellets get delivered without spilling? Is it an open or sealed container?
Simplicity: Is the design simple and clean looking, or complex?
Each criteria was rated on a scale of 1 to 5, then all the scores added together for a final score. I will contact each person directly to let them know what their actual score was, but here are the results:
Gold Prize: Jonathan, for Pellet Picker $125
Silver Prize: Dismay, for Pellet Mover $75
Bronze Prize: RoboLab 2.9 for The Pellet Machine $50
Our next step (NXTStep!) is to purchase an NXT unit and to build Jonathan’s robot and do some extended tests to verify the robustness, accuracy, and repeatability. If we’re confident that it will stand up to our industrial environment, we will be using the robot in our process! We may also work with the team of designers above to collaborate on working through any issues that may come up during our extended trials.
Thank you again for taking part, it has been a great experience, and perhaps we’ll think up another contest in the future!-----
Congratulations to the winners from all of us here at The NXT Step blog. We'll be on the lookout for similar projects in the future. That said, if you work for (or own) a company that has an idea for possibly integrating the NXT robot kit into a work project, let us know and we might be able to help facilitate a future contest for you.
Hope this helps to all the users of NXT-G out there... and thanks to Brian Davis and Steve Hassenplug!
Jul 25, 2008
Registration Is Now Open
The 2008 FTC Season Registration is now open. How do you register, you ask? Well, let us take a moment to tell you!
- Go to our registration web site: http://www.usfirst.org/
- If you are a returning team, log in and select the team you would like to register.
- If you are a new team, follow the instructions to create a login.
o A login and password will be emailed to you
o Use login and password to access registration site
o Create a new team
- Complete all the required fields **hint: required fields have an X next to them**
- When the required fields are completed, follow the "Program Fee" link to complete your registration **hint: the "Program Fee" link is near the bottom of the page**
- When your registration has been paid, a link under "Order Kit" will become active.
- Follow that link for ordering information.
o Paid teams can place orders for Kits immediately
o Kits will ship in August
o You may request an invoice be sent to you prior to the kit ship date
As requested by a number of teams, the Bill of Materials is now available for the new kit. Look under "Headlines" on the FTC landing page, http://www.usfirst.org/
Please be aware, we reserve the right to make changes to this list for the final kit.
TETRIX Video Released From Pitsco
Click here to see a video of the new TETRIX kit: http://www.legoeducation.com/
Jul 24, 2008
Here's a steerable blimp using an RCX. The maker wants his next version to use an autonomously-programmed NXT with a single mylar envelope that could theoretically fly for days.
Here's the builder's full description:
"Using an RCX, 3 Motors, the Infrared Remote, Large trash bags, and lots of helium, my son and I created a steerable blimp.
Two of the motors controlled propellers (made from a LEGO propeller with larger blades made out of packaging plastic). The third motor controlled the tilt of the two propellers.
Each propeller can be separately controlled. For example, to rotate the craft, one propeller would be driven forward and the other backward.
Metal washers were used as ballast to try to achieve neutral buoyancy so the propellers could be used to raise or lower the craft as well as move about the room. Helium leaked out of the trash bags fairly quickly so the ballast had to be frequently adjusted.
With one load of helium, we had about 2 hours of flight time (starting with a lot of ballast and then removing it bit by bit over the two hours).
The use of the Infrared remote was a bit of a challenge as the controls were not very intuitive (e.g., frequently tilting the rotors in the wrong direction). Also, maintaining the line-of-site needed for the remote was a challenge.
In my next version, I'm planning to make the following changes:
- Use an NXT instead of an RCX and use bluetooth to remotely control the craft.
- Set up more intuitive controls.
- Replace the trash bags with one large mylar envelope. This should greatly increase the flight time from hours to days or even weeks.
- Set up one of the propellers to have the opposite pitch to have the two props cancel each other out when spinning in a vertical position.
- Add sensors and program the NXT for independent control."
Gypsy incorporates the strengths of Nadar, but with a far more robust program and numerous sensors. It carries a custom pressure sensor (mentioned before) that has an effective resolution in altitude of as small as 10 cm, and also incorporates a temperature sensor. An accelerometer both logs accelerations on the payload as well as allowing the payload to determine when it is “cut down”. A sound sensor is also built in, both to detect any background noise (I expect very little… but you don’t know ‘till you try), as well as sample specifically the noise level when the motors are running and the loudness of a sample standard tone played from the NXT speaker (this way, if a motor starts to break or degrade, the NXT will literally record the “death cry” of the motor… and the fading of the standard tone with altitude should serve as a second way to judge the air density). The fourth sensor port is connected to a HiTechnic prototyping board, a fantastic device that will be seeing much more use by me in the future. This one board allows me to run a CDS cell light sensor (detecting the outside illumination during the mission), two internal engineering temperature sensors (one on the NXT batteries, one near the camera batteries, and a reed relay to switch an independent heater circuit on and off. By monitoring it’s own internal temperature, the NXT can turn the heaters (there are two separate units) on & off to maintain electronic-friendly conditions in the upper atmosphere, where the outside can reach -60° C or lower. And all that on one sensor port, using just a fraction of the simple input/output abilities of this $40 “sensor”. On a mission like this, an amazing bargain! On top of this, the program autodetects when a motor is stalled, and will not “hang” waiting for a motor command to complete.
Mechanically there are several untested things about this payload. First and foremost is how LEGO pieces, made out of ABS, will handle the bitter cold at 100,000’. The design uses a rectangular frame of CPVC pipe (also untested under temperatures this cold), and suspended from that are cords that attach to the two “hubs”, actually large LEGO turntables, that the pitch motor drives. If the pipe framework fractures in the intense cold, or the LEGO turntables shatter or separate, the entire payload would plummet out of the sky… without the benefit of a separate parachute like Lil’ Joe. So to back up these untested elements, Gypsy also has a more conventional “safety tether” that extends straight through the payload box. Even if the hubs or pipe frame fail completely, the payload box should still remain connected to the main system, to be returned safely to Earth.
I also used a novel method for a “remove before flight” trigger. The HALE team requested that payloads have a “key” or “pull pin” that would trigger the payloads right before the balloon was released. That way all the payloads could be turned on in a “waiting” mode, and a very simple pull of a removable trigger could quickly & reliably start the payload’s mission. I decided to have mine do double-duty: the CDS cell that during the flight monitors the external illumination is covered initially by a piece of Velcro (Velcro also holds the lid on the payload… and idea I stole from the LUXPAK group). When the Velcro strip is pulled away, the drastically increased light level is the cue to the program to begin the mission. This way, one sensor (and one that is multiplexed with several others via the HiTechnic protoboard at that) can serve two purposes, a “start trigger” as well as monitoring ambient conditions.
Another consideration on this mission was weight, so the payload shell is nothing more than a custom-fit, Gorilla-glued Styrofoam… in fact, the same kind you can buy in 4x8 sheet for insulating homes. Using a hot-wire cutter, I first made the internal mechanism, and then carefully constructed the shell around it – making sure I could remove it when I was finished (I used the same technique for Lil’ Joe, except in the end I had to drastically reduce the weight). The result was a close-fitting shell with good strength properties but very light weight, and some insulation value to boot.
Gypsy is really a two-goal payload: versatile camera platform, and dedicated datalogger. Even if the camera portion of the mission were to fail, there would still be a whole lot of very interesting data returned. Now I just have to wait and see… by far the hardest part of the mission.
Next up - Gypsy, the Software
More pictures can be found on my HALE Brickshelf gallery.
Jonathan and I are looking forward to the release of our new book, "FIRST LEGO League: The Unofficial Guide" in August. This book is part of a series of books in the No Starch NXT Library and will join David Perdue's "The Unofficial LEGO MINDSTORMS NXT Inventor's Guide," Fay Rhodes' "The LEGO MINDSTORMS NXT Zoo!," and The NXT Step contributors' "LEGO MINDSTORMS NXT Idea Book."
In preparation for the release of the book, No Starch has a nice offer for you - order 4 or more No Starch titles (feel free to buy 4 copies of FLL UG if you like!), and you get a 40% discount on the order AND free ground shipping. Use Voucher Code 410281213 to get the free ground shipping. All 3 of the above books, plus the FLL Unofficial Guide can be in your library!
UPDATE: The Discount Period ends Oct 1, 2008.
If you know of some new teams, new FLL coaches, and/or new FLL students, please pass along this offer.
FIRST LEGO League: the Unofficial Guide is tentatively scheduled to ship August 20, 2008.
H.A.L.E is an event that will carry LEGO Mindstorms-based payloads into the Earth’s stratosphere. At that altitude H.A.L.E. will be above 99.9% of the atmosphere. They payloads will be exposed to extreme the cold and radiation of near space. The sky looks black and the curvature of the Earth is evident.
The launch vehicle consists of an atmospheric weather balloon and a communication system to track the payloads. Once the balloon reaches approximately 30 km in altitude, it ruptures and the payloads return to the ground under parachute.
Projected minimum altitude: 27 km (88,000 feet)
Projected maximum altitude 33 km (108,000 feet)
Video from a Prior Year's MissionThe following video was captured at the moment of maximum altitude "balloon burst".
Jul 23, 2008
For this tutorial, you will need:
- HiTechnic gyro sensor
- RobotC installed on your computer (you can download it here).
Build the robotic platform. You may use your own idea or use the instructions provided below.
Here are some tips if you decide to build one yourself:
- Wheel size is important. I first tried wheels that were too big and the robot just flopped on its face. Why? The program I used was design for wheels of a specific size, hence wheels that are too small would also not work.
- Wheel spacing must be also considered if you want your robot to turn. If the wheels are further apart, then the robot needs more rotations to turn; if the wheels are closer together, then the robot needs fewer rotations to turn.
- Orientation of the gyro sensor is also important; if it is incorrect, the robot will fail to balance. For the correct orientation, see in the pictures below.
Here are the instructions for the simple NXTway I made:
And check out the rest of Chris' site... if you haven't seen his homebrew DIY UAV (powered by NXT) be sure to watch some of the videos and read his writeups here.
The command and control for Lil' Joe is fairly simple: when it is turned on, the NXT-G program starts writing timestamped 3-axis accelerometer data to a datalog as fast as it can. Every five seconds it checks a "free-fall flag", and if that flag has not been set it erases the data & starts again. This way, the final datalog should contain a few seconds of data from just before the payload is cut free, extending through the free-fall and the parachute deployment beyond... even though the NXT doesn't know in advance when it is being released. A second sequence running in parallel with the first is responsible for detecting free-fall and deploying the parachute after that. It simply hangs in a loop, waiting for at least 0.5 seconds of near free-fall (less than 0.25 G's) acceleration, and once it detects that sets the "free-fall flag", as well as starting a count down for the parachute deployment. At the moment of deployment this sequence pauses datalogging briefly, runs the motor to unwind the tether & deploy the parachute, and then resumes datalogging (datalogging is paused because a poorly-timed write to the flash memory can mess up the internal clock and motor control, disasterous if the motor in question is releasing your only parachute).
Just how fast and how far Lil' Joe will fall is poorly known: a 20 second free-fall with no friction at all can produce a velocity of 440 mph after a fall of more than a vertical mile. But even with as thin as the air is up there, there will be some friction, & as the payload plummets deeper in the atmosphere and the atmosphere gets thicker aerodynamic effects will limit it more and more. So it's really an unknown right now. The good news is that with the size of the payload bottom and the size of the parachute (24"), it looks like parachute deceleration might be reasonable at under 10 G's for a couple of seconds... but that means the heavy portions of the payload (batteries) need to be very firmly cradled by the parachute lines directly. The team at the University of Nevada at Reno are working with me on perhaps adding some things to the payload (such as a convection baffle for after the tailfin comes off, and perhaps stronger webbing).
There are more pictures of Lil' Joe up in my Brickshelf gallery:
HALE Photos on Brickshelf
As well as a short YouTube video of Lil' Joe. This is really aimed at explaining to the launch team how it is unpacked and packed, but it also shows (near the end of the video) what the internal mechanism does during free-fall. Hopefully this wasn't the last time I ever get to video it :).
Lil' Joe preparation on YouTube
Jul 22, 2008
WARNING: Gizmodo's comments can sometimes include non-kid-friendly statements - I wish I could just share the video and commentary, but it appears to be embedded in their blog.
Thanks to Steve at HiTechnic for the link.
A small group in the water was playing with a small toy submarine that was in clear plastic - it appeared to be remotely controlled but it was unusual looking. I really think this item was not made in the USA as it had a distinctly Japanese look to it - not sure how to explain that but it just looked like similar toys from Japan that I've seen.
Anyone seen this? Know where to find one? I've Googled and dug around, but no luck. It was housed in a clear plastic shell (maybe a slight bluish tint to it) and had an external prop for movement and (I think) some sort of piston/hydraulic that pulled in and expelled water from a tank.
I think it would be awesome to have a similar shell built for the NXT... but I now many of us are hesitant to take our bricks anywhere near water.
I'm kicking myself for not swimming over and looking... argh.
Jul 20, 2008
- Eugene Tsai (Taiwan): payload will use filter papers to capture particles and/or chemicals in the air during the balloon ascent and/or descent periods. The LEGO Mindstorms NXT will used to provide a mechanism to switch filtering papers to capture the materials in the air and then keep the papers in a secured compartment. The filtering papers will be retrieves and analyzed what particles and chemicals exist at different altitudes.
- Brian Davis (USA): Gypsy (a.k.a. Nadar 2.0) will be a fully automated camera platform that taking both video and still images. The NXT will control all image timing as well as pitch angle of the platform, and datalog more than 11 different parameters at varying intervals during the flight.
- SpaceMasters Robotics Team (Sweden). Team is lead by Jurgen Leitner and David Leal Martinez. The XGRAVLER (EXperimental GRAVity research with LEgo based Robotics) payload will be measuring the change in g-forces as a function of altitude. The plan is to have the payload repeatedly drop a tethered Wii-mote to measure the acceleration experienced at different altitudes.
- Brian Davis (USA): Lil' Joe will perform an automated free-fall in an attempt to set the record for the longest NXT free-fall (since there hasn't been one yet, this is a pretty easy record to capture... if the parachute deploys). The payload will be detatched from the main balloon near maximum altitude and will free-fall until the NXT deploys the parachute. It will also be logging 3-axis acceleration data before, during, and after the free-fall, to be retrieved separately from the main payload stack.
- LUXPAK (Luxembourg): This student team is mentored by Claude Baumann, Francis Massen, Jean Mootz, and Jean-Claude Krack. The payload will measure ozone-concentration, air-pressure, temperature (inside/outside), and reflected light from earth during ascent. In recognition of the 10th anniversary, LUXPAK will be using an RCX for command and control functions. See their very detailed development log for a lot more information.
- Barbara Bratzel and Chris Rogers are leading a group of 4th grade students (USA): The students want to investigate the impact of the flight conditions on yellow marshmallows (a.k.a. peeps). The NXT will be recording temperature and pressure during the mission. Personally, I can't wait to see pictures of yellow marshmallow "Peeps" being loaded into a mission payload... I'm hoping at least one is wearing a helmet :).
- FLL Team 90 (USA) is lead by David Levy: the payload will be measuring UV radiation as a function of altitude. The NXT will not only data log the UV sensor readings, but is also be used to manipulate filters and control the payload heater.
- LEGO Mindstorms Team: top secret classified payload. Yeah, I wish I knew what it was as well, but they're not talking.
Bishop covers sensors, variables, loops and switches, with special sections on mathematics (Sines, Cosines, Square Root, Factorials) and the compass sensor. All of the blocks and MyBlocks covered in the book are included on a DVD that comes with the book.
The DVD also includes a list of book illustrations that are cross-referenced with the programs on the disk. For example, illustration "13.14" in the book refers to the "Maze Runner" program found on the disk. This cross-referenced list makes it easy to find a particular program discussed in a particular portion of the book.
Some programs covered by Bishop:
1) "Housefly" Program: A fast-falling shadow on the light sensor (like that of a fly swatter) causes the robot to quickly move, in order to escape the "swat".
2) "Maze Learner" Program: The robot "learns" each section of a maze by having the brick's left button pressed at each juncture of the maze. The robot will then repeat its "learned" route.
3) "Magic" Program: A pointer on the robot will "read the mind" of the robot's operator, by pointing to an illustration which only the operator knows. (The program is a trick, of course, but a clever one).
I haven't yet tested any of the programs in Bishop's book but am eager to do so. The book reminds us that NXT-G is a fairly sophisticated programming language that can challenge even an expert.
Two quibbles with the book:
1) The DVD is never referenced in the book; therefore, the buyer doesn't know the disk's contents until he/she puts it into a computer. A listing of the DVD's contents within the book would have been helpful.
2) The book's cover price: $41US is a lot of money for a 185-page book printed in black-and-white, even if it includes a DVD of programs. Fortunately, Amazon.com sells the book for $27US, which includes free shipping.
Amazon's link to the book is
Jul 19, 2008
Eric is also in the process of building the animals from
Eric's web site is
Jul 18, 2008
Our favorite NXT display application has really grown! As MDP, Andreas Dreier created this application 2 years ago and offered a wonderful way to give a personal touch to our NXT screens. Use it once...and you'll want to add images in all of your programs too! Checkout the abundant features and improvements in English or German.
I must say, the proudest bit of this is that is written in stock NXT-G, with no add-ons or NI Toolkit VI's.
It is near completition, so I thought I'd put out a little (or, rather large) teaser.
You can also go to my website at www.legorichard.bravehost.com/homepage.html for more pictures.
Enjoy, and keep your eyes peeled!