Lego Mindstorms NXT : Put yourself in robotics

[MurTuza]

For these older children, Lego in recent years developed a range called Mindstorms. It is for the firm to propose that the Lego Technics program on the computer via either a sort of first approach to robotics. Not content to build his own robot, the self-respecting geek can now schedule, so developed, allowing for interaction with the environment, as we shall see a little further. Lego book indeed various sensors that will give your achievement some intelligence. As we approach Christmas, we propose to test or rather we play with the Lego Mindstorms NXT kit. To put an emergency under your tree?

Lego Mindstorms NXT: A Brief History

Lego enthusiasts surely remember the Lego Technic set out in 8852 ... 1987! At the time, it was a truck turning through the manipulation of a wheel in a robot. Fully manual, the robot kit in 8852 was far from matching the capabilities of one of the robots that can build with the Mindstorms NXT kit that concerns us today. Yet it somehow opened the door, as the yellow submarine, released in 1997 with Pneumatic system and, for the first time at Lego, CD-ROM montage (set 8250).

Lego Technics 8852

Of course, the Mindstorms NXT kit alias 8527, as it is today, does not quite out of nowhere, since Lego develops past few years its robotics program with various products, including Mindstorms kits. They have a dual purpose in wanting both fun and educational while to go back in 1998 to find the exit of the first Mindstorms kit. At the time, Lego had the services of the Massachusetts Institute of Technology, and proposed the RCX or Robotics Command System, a brick capacities smaller than that now animates the Mindstorms NXT. The NXT benefits for its return of enthusiastic users of the community Mindstorms, Lego had managed to unite and create a community around its programmable kits. With all Mindstorms NXT, Lego is proposing to build, among other things, a fully articulated robot can move and react to its environment by the robot since Technics of our childhood, the Mindstorms NXT robot is "intelligent".

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At the heart of Mindstorms, NXT brick

With 519 rooms, all Mindstorms revolves around the new NXT Intelligent Brick, which contains a microprocessor 32-bit ARM-7. This role will be to implement programs that will be transmitted via the USB cable or via Bluetooth, a Bluetooth radio standard Bluetooth 2.0 are included in this brick. Keystone of the system, brick NXT is powered by six batteries LR6 (or a rechargeable battery that can buy optional). As often in Lego, the problem of replacing batteries to replace them because it will remove the brick ... and therefore to play its construction. Given the power consumption of the equipment, our six batteries had not lasted more than a month, the purchase of the rechargeable battery seems essential.

With an LCD screen and a total of four buttons, the central orange button to start the system, the brick has a menu with icons in which sails with the arrows. This will select the program you want run, activate the Bluetooth, consult the contacts his mobile phone, adjust the volume of integrated speakerphone or put some order in its files or test the functioning sensors with some test programs.

The bare brick NXT

With 256 KB of flash memory, brick NXT unfortunately can store a limited number of programs. This is especially unfortunate that the speaker Piezo it contains can be used to give the robot voice: except that storing audio files, the amount of available memory is quickly reduced. In terms of connections, found on the bottom of the brick, four owners connectors (RJ-11 type) to connect the various input sensors Mindstorms while the top of the brick has three connectors, always type owner, for control a total of three electric. Not far away lies the USB connector used to program our brick. Also on the NXT brick, it is noted that micro software is free, so you can edit it to your liking or take advantage of alternative firmware developed by the community.

It should be noted that the sensors of the first Mindstorms RCX are not compatible with the new NXT. It will be the acquisition of adapters, sold as an option, to continue to enjoy its first generation accessories. In addition, the NXT brick fits differently in your constructions. Exit here want the assembly, Lego proposing only holes on the sides and bottom of the brick, how bricks Technics.

NXT brick in operation

Sensors, you want? here is!

The Mindstorms NXT kit includes, in addition to mounting elements such as bricks, gears, plots, etc.., A set of motors and sensors. Found in the box three servo, all identical, with a detector rotation. The rotation of the engines may be in degree and each engine can be operated with varying degrees of intensity.

Servo-motor Lego Mindstorms NXT

Side sensors, Lego provides four ... all different! Lego offers a sensor contact or touch, a microphone, a light sensor and a sonar. The light sensor can detect three levels of brightness: it can create a robot capable of moving along a line drawn on the ground or a robot able to sort by color. For this reason, a red ball and blue ball are supplied in the kit. For its part, the sonar detects the proximity of an obstacle to an accuracy of 3 centimeters to a scale from 0 to 255 centimeters. Finally, the sensor that we baptized microphone only measure the decibel level of the room.

With this wide range of sensors, the robot, or else your mind can hear, to locate in space and detect light and intensity of the latter. Optionally, Lego offers on its website other sensors including one capable of detecting colors, the latter containing an accelerometer and the third incorporating a compass.

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Mindstorms NXT: assembly

Sampling of various sensors delivered with Mindstorms NXT

Comes in a box more imposing dimensions, the Mindstorms NXT kit includes a large number of coins, which should delight fans of mounting a little complex. Since it is possible to achieve up to four different models, you will find in the kit of parts as unexpected as pliers, claws, balls, wheels, without forgetting the traditional plate stickers. The installation instructions are somewhat confusing because in our evaluation unit, we found the plan to mount our robot ... on the CD-ROM software NXT, which we will come back a little further. Mounting a Lego Technics with a computer rather than on paper ... this is not always practical.

For the rest, the instructions are relatively well thought since the construction of the robot is divided into various stages: assembly of each individual leg, construction of trunk, arms and creation, the final elements coming form the head in particular. Your servant, who had not touched a Lego Technics since the famous dump truck with arm and programmed by reading bar code, quickly dérouillé to find the pleasure to build a Lego simply in about an hour weather.

Petit regret when mounting it is very difficult (impossible?) To know the correct length of cable used to connect sensor or actuator to the brick: it is sometimes with cables too short (or vice versa) and the you start to sew to guide them so that the cables n'enrayent not the proper functioning of mechanics.


Mindstorms NXT: software

The assembling your model finished, we must now proceed to install the software Mindstorms, a software compatible with Windows Vista and Intel Mac version 1.1. Available in French, the software installs quickly, but requires a restart of the computer to be fully operational. Graphically pretty well, although a little too detailed, the Mindstorms software allows you to program your robot visually. To do this we find a set of operators grouped in a toolbar vertical display is simplified default while most of the screen is a plot on which to slide the various commands that will constitute the heart of your program. Using the programming language NXT-G, the Mindstorms software is fully chart: here not to dip his hands in lines of code.

Although wholly visual development environment Mindstorms is not disconnected from programming as we know it on our beloved PC. Thus we find loops and switches (if a condition is met), as in any programming language. Among the simplest operators, software Mindstorms proposes to operate the functions of travel: by dragging the move on the work surface, then choosing the port (A, B, C) engine you want actuate and we can then adjust the number of rotations, speed or duration. Among the basic features, the software can play sounds on the robot or to display icons on the LCD screen of the NXT brick. Unfortunately, these functions are limited, especially since the sound aspect is no question of its MP3 download on the NXT brick. Too bad!

Then come more sophisticated operators such as those indicating the program to await an order from a sensor whatsoever, before executing another action. It is of course possible to create loops in loops or using switches to tell the program to any action based on a condition that you choose yourself. Better, by switching palette, there are programming tools more advanced with the ability to perform calculations, adding logical operators or even generate random numbers or set of variables. And like a true development environment, it is possible to add comments. Once your program is complete, all that remains is to compile to send it to the NXT brick and run.

In short, if the NXT-G is accessible to all, it is not dopey, quite the contrary. It will take some uses to discover the wealth of opportunities offered by the programming language using its resources to the least excavated. It appreciates the rest integration of a module for assistance in the application for monitoring tutorials to put together, step by step, simple programs related to the model that was built.

Conclusion

While Christmas is near, the Lego Mindstorms NXT is certainly an original gift for any self-respecting geek. Combining into a single product, say no toy, the best of two passions (Editor's note: computers and Lego), the Mindstorms NXT kit remains, two years after its release, still bluff. While the capabilities of the NXT brick could be higher, particularly with regard to his memory or his screen as you would like color, but the possibilities offered by the Lego Technics of a new kind are simply breathtaking. All motors and sensors supplied by Lego to create from the mounting models fully functional interactions with enough fun. Imagine that our robot, named Michael in tribute to a famous Canadian, we can wish good night when the light goes off in the room or say hello when we light the lights. Better, Michael is able to move himself when we are near us away while he can tell us in review and make a U-turn.

So of course with software programming as Mindstorms NXT, we have only the possibilities of Lego as some optional sensors to enrich what can be done. But in the meantime, build the robot, see the town, and the program according to our wishes was a rather pleasant it must be acknowledged. Realizing the full potential of Mindstorms NXT will require time, however, and ... the money, the kit is expensive in 8527 while the optional sensors are quite expensive.