NXT Johnny Five
Monday, May 14th, 2007
Here’s a Lego robot copy of famous Johnny Five I found on YouTube. I hope I’ll find some details from the maker.
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NXT Radar - Part II
Saturday, May 12th, 2007Before I dwell into the technical details - a brief overview: NXT uses 6 wire ports. All passive/active RCX style sensors use pins 1 and 2. Digital sensors typically use pins 4-6, unless they require also a 9V power supply from pin 1.
The Lego Sonar sensor fits the last category. It requires 5 pins to function - +4.3V, ground, 2 digital (I2C) bus wires and the 9V power supply.
Soon after I started working on this project I realized that the sonar sensor is not an option. The reason is simple - all commerical cord untangler I could find only have 4 wires. These untanglers are used to connect a phone handset with the phone itself, and thus need only 2 wires for the loudspeaker and 2 for the mic. I could not find any manufacturer producing 6 wire untanglers (Maybe LEGO will make one some day?). The untangler I did find was this:
This untangler fits perfectly into the base of the old Technic turntable (Peeron #2856), and can be easily secured in place with thin 1×4 lego plates.
What of the sensor? well, I found out that mindsensors.com Sharp IR sensor does NOT require pins 1 and 2 to function, so this sensor can be incorporated into a radar-like sensor. But before I could build the radar itself I needed to make some soldering. First, I used a Dremel to expose the contacts on the untangler:
Then I cut one of my Lego wires, and an old phone cord and did some soldering. Make sure you put all heat shrinks on before you solder! The resulting units look like this: (click to enlarge)
It required some practice till all wires were soldered correctly, but at the end it worked. Mounting this into the turntable, I soon discovered that rotating it became more difficult (probably since the untangler is not concentric), which required a very stable construction - connecting the turntable to the platform with studless connectors, mounting gear very tightly and having the NXT motor connected directly to the turntable base. After all this was done (summerizing many hours of failures in two sentences…) the radar was ready!
Next post - programming using LabView…
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IBM PC PS/2 Keyboard Interface for NXT
Saturday, May 12th, 2007
Michael Gasperi did it again! Another cool hardware mod - an interface between the PS/2 keyboard and NXT. See the details and video on this page. Also there’s a discussion post on our forums here.
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NXT Radar - Part I
Saturday, May 12th, 2007
Here’s my latest project - a true NXT radar. The Sharp IR Distance sensor from mindsensors.com is mounted on a turntable on top of a mobile platform. The unique feature of this robot is that the sensor can be rotated infinitely, without tangling the cables, using a modified handset untangler.
A discussion topic is here. More details will appear soon…
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Mindsensors.com Port Expander
Friday, May 11th, 2007
Here’s an image of the prototype port expander of mindsensors.com. As you can see, it will allow connecting 3 digital sensors to one port. I’m not sure, but it probably can connect multiple expanders to connect even more sensors. I’ll post more details on availability and use when I get them.
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20 Days to Challenge Deadline!
Friday, May 11th, 2007Only 20 days left till our NXTasy.org 2nd challenge is over! We already have a few contributions, both in NXT-G and other programming languages. Still, I would be happy to see many more people trying to complete the challenge, so we feel it’s worth continuing this “tradition”.
I remind everyone of the rules, and the prizes sponsored by mindsensors.com:
1st prize in each category - $60 credit towards purchase at mindsensors.com
2nd prize in each category - $35 credit towards purchase at mindsensors.com
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Camera for NXT from mindsensors.com
Friday, May 11th, 2007
Mindsensors is coming out with a camera for the NXT. The camera will be able to track up to 8 objects. The beta trial is scheduled to begin on 1st June, and the plan is to make it generally available by end of July.
More details and video is here.
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NXT Plotter
Thursday, May 10th, 2007
Völker Nils from Germany has made this impressive NXT plotter. Nice images and video on his site. The programming was done in nxc, and is described in detail here. Take a look at the way he made a homebrew long gear rack using modelling clay!
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News of the Month!
Thursday, May 10th, 2007For those who are not very familiar with the nitty-gritty of the NXT digital I2C bus, I wish to highlight the significance of the ‘Homebrew NXT port expander’ published on NXTasy.
As many have experienced the major limitation in the NXT is the number of sensor and motor ports. The only solution so far was using another NXT, communicating with Bluetooth with the first NXT (or RCX communicating with other means, like published a while ago). HiTechnic has been developing an active sensor multiplexer for some time (a picture of the prototype is here). This multiplexer will allow connecting 4 sensors – either passive (e.g. touch sensor), active (e.g. light sensor) or digital (e.g. sonar), to a single NXT port.
The solution presented by xw25adc is different – his port expander connects in series just the four ‘digital’ wires from the 6-wire NXT port – the +4.3V, the ground and the two digital I2C wires. Well, I’m getting too technical… Let’s stop that.
So what this so innovative about xw25adc work? To connect more then one digital sensor to a one port (i.e. a common ‘I2C bus’) you must have the sensor recognize that other sensors are connected. Why? Because the total of all sensors’ pull-up resistors must equal 82kOhm. If you naively connect two digital sensors, the pull-up resistance equals to two 82kOhm resistors in parallel which gives 82kOhm/2=41kOhm and the sensors will not function.
Anyone who read mindsensors.com manuals might notice a feature called ADPA: Supports Auto Detecting Parallel Architecture (ADPA) for sensors. This means that ACCL-Nx can coexist with LEGO or third party digital sensor on the same NXT port. This enables user to employ several sensors on the same port without the need of external sensor multiplexer, reducing the overall size.” This feature is just what one need to solve the previous problem – activating the ADPA on mindsensors.com sensors (it is shipped turned off) make them sense and recognize if more sensors are wired to the same port, and change the pull-up resistance to compensate this. xw25adc MUST have activated the ADPA feature, and used the compass sensor “advanced” I2C commands to change his ‘address’ from the default value 2 to 4. As far as I know, this is the first demonstration of this feature in action. Now some may ask - Wow! Can I do it too? Well, I can tell you that mindsensors.com have a prototype of a similar port expander in hand. In a few days I will post an image of this prototype when it reaches me. I’m currently working on a simple PC/Mac application that will ‘manage’ sensors – change ADPA on and off, change address etc. If I get some help from Lego/NI this application might even incorporate into the ‘Tools’ menu in NXT-G (no promises…).
One final technical detail – what differs between HiTechnic sensor multiplexer and mindsensors.com multiplexer? The former also allow connection of passive and active sensors, while the later supports only digital sensors (actually, only digital sensors which do not require 9V supply). This requires active components to regulate which sensor’s analog readout is transfer to the NXT at any moment. For these reasons, the HiTechnic multiplexer is expected to be more expansive (and it require 9V supply) then the passive mindsensors.com ‘I2C expander’.
Guy Ziv
NXTasy.org
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Homebrew NXT port expander
Wednesday, May 9th, 2007
I received an email from xw25adc, the maker of this nice port expander (so, finally I know how made these I2C Read/WriteNXT-G blocks !). Here’s his description:
In this video you see a NXT brick connected to 4 sensors, one mindstorm.com compass sensor at address 4, one Acceleration Sensor at address 2 and two home brew 8574 input / output sensors at address 40 (on left one) and 46 (to the right). These 8574s are 8 bit input / output integrated circuit chips with a I2C interface. In this project the compass sensor is controlling a arrow at the top of the NXT display, the Acceleration Sensor is controlling a pointing finger at the right of the NXT display and the program is causing four lights connected to the 8574 chip on the right to blink in sequence. The program reads the touch sensors connect to the 8574 on the left and turn on a programmed light when one of the touch sensors is pressed.
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(Another) Balancing NXT robot
Wednesday, May 9th, 2007
Our forums reader RegwayFB16 , a electrical engineering student from the University in Kassel in Germany, posted on this self-balancing robot. The cool thing about this one is that it is programmed in NXT-G ! The video can be seen here, and the program can be downloaded here.
Very nice RegwayFB16!
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NXT explorer
Tuesday, May 8th, 2007
Here’s a VERY nice looking ‘explorer’ NXT by forums reader PTP. This explorer uses 3 multiplexed touchsensors, the ultrasound sensor, a color sensor, and a compass sensor. The driving base is extremly compact using two motors for navigation and the remaining motor port is used to drive two alternating LEDs. More images and discussion in this post.
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NXT Software version 1.1 announced!
Monday, May 7th, 2007From LEGO official website:
The LEGO® MINDSTORMS® NXT Software version 1.1 to be released in August 2007.
The team behind the LEGO MINDSTORMS NXT is happy to announce that from August 2007 the LEGO MINDSTORMS NXT Software version 1.1 will be available for all users in five languages (English, German, French, Dutch and Japanese). Among its new features this version includes full support for Windows Vista (32-bit and 64-bit) and the new Intel-based Macintosh systems.
In addition, the new NXT Software offers improved performance and speed, especially for large program development. New compression methods free up 30kb of useable memory on the NXT Intelligent Brick and shrink most programs and sound files by 40%. The software programming module, called NXT-G, features intelligent scroll + more than 100 other enhancements.
Availability to users:
The LEGO MINDSTORMS NXT software version 1.1 will be available in the LEGO MINDSTORMS NXT #8527 robotics toolset from August 2007.To support existing users of the LEGO MINDSTORMS NXT #8527, we offer a CD with the new NXT Software version 1.1 for 19.99 USD, plus shipping. This offer will be available from our online shop, Shop@Home.
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pbLua beta 7 now available
Monday, May 7th, 2007Ralph Hempel released a new beta version of pbLua. You can download it via pbLua website:
http://www.hempeldesigngroup.com/lego/pbLua/
What’s new in this version? It’s got some significant new features including:
1. The ability to turn the NXT off by pressing the orange button for at least three seconds
2. A startup screen that lets you select a Bluetooth device as the console. This will finally free you from the tether of the USB cord!
3. The RS485 high speed port now also supports standard baud rates from 1200 to 921600. This must be carefully used so that you don’t flood the 128 byte RX and TX buffers at lower baud rates
[via Lugnet]
Posted in firmware, news | 145 Comments »