ROBOTMAK3RS Blog

Someday, the hardware police are going to come and take away my toys, citing me for criminal abuse. Until then, I'll continue to see what an NXT can handle... and what I can learn in the process. On a recent trip to Niagara Falls, I was fascinated again with this huge, impressive natural feature. And thinking about the foolhardy souls that over the years have tried to survive going over the falls in a barrel, I did what was natural for me - thought about the NXT doing it. Of course, getting permission to throw something over Niagara Falls is unlikely to happen... and it's dangerous, and retrieving it would be extremely difficult. But I could certainly do some test runs... so was born the "NXT in a barrel". I used an NXT slid into a 4" PVC pipe segment, sealed tightly at either end with re movable closeout plugs. To keep it from bouncing around inside, I used a hot-wire cutter to shape foam "bulkheads" to support and lock the NXT into place within the tu...

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...

Damien Kee from Domabotics.com has written a new booklet on datalogging with the NXT. I recently got a chance to read through it, and my first impression is that it was well-named. Titled " Datalogging Activities for the Busy Teacher ", it is structured as a series of almost stand-alone short projects or lessons, ideal for teachers with little time and little or no background with the NXT. The book starts with a few pages talking about what datalogging is & how it works, and then just a very brief review of the built-in datalogging environment of Educational version of NXT-G 2.0. At the end of the book are a series of handouts and worksheets for the students, saving the teacher the time of developing these themselves. But the bulk of the book is a series of chapters organized by sensor: datalogging with the touch sensor, datalogging with the light sensor, etc, including the new temperature sensor. Each chapter starts with a description of the sensor, and what sort of rea...

I've had the chance to have a good play around with the new education version of the software, in particular the datalogging aspect. Whilst it's possible to do datalogging in previous versions (check out some of Brian's amazing posts) the new version ties it all together in a nice GUI that I think will appeal to many teachers. Each experiment has it's own Configuration panel where you can specify the sampling rate, overall experiment length and the sensors you'll be using. Once setup, you can run the experiment in either Real-time or remote mode. Real-time allows you to see the data as it's captured whereas remote allows you to download the experiment, take the NXT to another location and upload the data once the experiment is finished. NXT-G2.0 produces some nice graphs and enables you to to do some basic analysis. This is the graph that was produced when I logged the light levels in a room for 24 hours. Overall I really like it. It is quick to setup and run...

I realized I have a lot of sensors. I should really review them :). I've been using the new NXT temperature sensor (mentioned here in the blog a while back) for a couple of projects, and decided to blog my opinion of it. Note this isn't even remotely authorized, approved, or perhaps even noticed by LEGO et. al... these are just my experience and opinions, your mileage may vary. Both the old analog temperature sensor ( product ID W979889 , $38.95, although you need a conversion cable to use it with the NXT) and the newer digital temperature sensor ( product ID W979749 , $39.95) are available from LEGO Education (they're not normally distributed through the retail arm of LEGO). I've been using these for a number of projects, including monitoring the temperature in my house and freezer, and recently for instrumenting a model geyser (in my kitchen... yeah, it's messy around here). The old sensor is analog - it actually put out a voltage that changed with the temperatur...

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

I recently returned from a wonderful week-long vacation in the Rocky Mountains here in the US, and of course took along the NXT. I mentioned before that I was trying to get the NXT to function as a pedometer to record footsteps for a project I was working on. Well, I didn't get the pedometer working, but I certainly had fun on the project... The HALE mission is rapidly approaching, and one of the things I wanted to do on my payload was fly a good pressure sensor. A really good one, with possible vertical resolution in the range of a meter or better. After some discussion with the folks over at Hitechnic, they were able to put together a prototype for me to fly with very high resolution. But how to test it? First, I made a small vacuum chamber from a Tupperware bowl, aquarium supplies, and a large-bore syringe, testing it out under hot sun & in my freezer (my wife did look at me a little funny...). It worked rather well, but I wanted more. Since ultimately the HALE pressure da...

Well, it’s been far too long since I’ve blogged… well, anything . So I wanted to drop a quick line to mention three interesting datalogging examples I’ve hit upon during the last few months. In some cases, these are only ideas to be built upon, but they should give you food for thought on datalogging with the NXT. All these images are up in my Brickshelf gallery if you want to look – plus more. First, I was contacted by someone who wanted to know if it was possible to use the NXT to log the accelerations of a Hulahoop. So I said “I don’t know”… and tried it. The first task was trying to get a semi-balanced hoop with the weight of the NXT. So I used the b est thing I could to counterbalance an NXT… another NXT. Using duct tape (a lot of duct tape) I taped one NXT with a Hitechnic accelerometer to one side, and another NXT to the other side as a counterbalance. OK, now the next problem… I can’t Hula-hoop. At all. And a hula-hoop with a dozen AA batteries duct-taped to it isn’t the easies...

One of the things that has come up recently with regards to NXT-G v2.0 and datalogging is the speed that information can be logged. It seems the custom logging option under NXT-G v2.0 may be “slow”, in that it only logs somewhere between 10 and 100 readings every second (reports vary wildly, and until I test it myself I’m in no position to speak on this). Readers have pointed out, quite correctly, that NXT-G is not the fastest option for this. Robolab, for instance, is faster, and other offerings such as RobotC and pbLua are blazingly fast. But before everyone complains about this “new feature”, consider two other important points. First is ease of use. It seems that with NXT-G v2.0, LEGO Education will be releasing a version that has a lot of the datalogging handled for the student (or the teacher), making it easier to get and process data. That may require a slightly slower acquisition rate, but it may be more than worth it to some folks, especially if it provdes built-in smoothing,...

MAKE magazine's website has a small writeup and link to Brian Davis' writeup on using the NXT and datalogging at Disney World. Check it out here . (Of course, the article's link will bounce you back here...)

So what do you do if you're taking a family trip to Disney World, and you're me? Take your NXT of course! As a physicist, I've always been curious (read: obsessed) with things like the acceleration on roller coasters. So, on a recent trip to Walt Disney World in Florida I took an NXT with a field-ready datalogging program & a Hitechnic 3-axis accelerometer attached. In the picture at left, you can see the NXT with me on Expedition Everest... OK, actually what you see is a picture of me screaming like a little girl with one hand raised, as the other crushes the NXT into the seat beside me. But it's there, trust me. Previously I had datalogged by just grabbing a reading and storing it in a file as quickly as possible. But for a 5 minute ride the resulting file would be large - so large that I could only record one or two rides a day. Instead, the program stores the average value of the three axis data, with the sampling interval selected by the user at start-up. The...

Guy Ziv over at NXTasy has written a nifty little utility called NXTLogger that will allow the NXT to dump data from an NXT-G program directly to a nearby PC using the BT link. I've had a lot of fun datalogging with the NXT, but I've done everything on-brick: not having Guy's skills, I'd not tried this approach. But it looks like it works great - I've been corresponding with him on this a little, and I'm anxious to see what others think of this. In addition to several advantages Guy mentions in his post, there's at least one other I think folks will like: In an educational environment, the very rapid upload and analysis will be nice to have, when every moment counts in a classroom setting. This is a beta version, but he tends to write some very stable applications in my experience, so please give it a try... and let us know what you think, what your experiences are, and what improvements or modifications you think would be handy. -- Brian Davis

So what happens when you let a physicist loose with an acceleration sensor? They find something to measure of course! I’ve been fortunate enough to test several sensors, including the HiTechnic acceleration sensor. This is a 3-axis accelerometer that can register up to 2.5 G’s along each axis with a fairly high resolution. I used it for a couple of “standard” robotics-type applications, like vehicles that try to roll up hill, etc., but what originally drew my attention to the RCX, years ago, was its ability to function as a cheap datalogger. So I wrote up a simple NXT-G program that allows me to log data from the sensor to the NXT file system on command: the result is a compact and very rugged datalogger, suitable for measuring accelerations almost anywhere. As an example, I duct taped the sensor to my tailbone, and went out back to play on the swings. The graph shows the results. The red line is the side-to-side acceleration (minimal, as I was trying to swing in a straight line), whil...