Lego Mindstorms NXT



I have been playing with Mindstorms NXT since November 2007. As I usually always create a LDraw file of my creations in case I want to rebuilt one, I decided I might as well post them on the web in case they are of any interest to anyone.


So here are some of them. I will add more as time permits. The videos are all wmv files and the programs are all RobotC. After programming with such languages as C++, VB and C#, I just couldn’t get used to NXT-G and its graphical interface.


I have only one NXT brick but have bought lots of  HiTechnic sensors and the Mindsensors MotorMux and a lot of extra Lego pieces from BrickLink.




An Orrery is a mechanical apparatus which illustrates with balls of various sizes the relative motions and positions of the earth, moon, sun etc. I decided it would be impossible to make the planet sizes to scale as even if the Earth was only 1cm in diameter, Jupiter would be over 11cm and the Sun would be over 1 meter. Likewise if I tried to make the distances from the Sun to scale, with the Earth at 10cm, then Neptune would be at 3 metres.




This is my second attempt at a robot that can play checkers. My earlier effort (CPR) was slow and unreliable at identifying the pieces.

This one is pretty fast to both scan and play taking approximately 30 seconds to scan and 10-15 seconds to make a move. It is totally autonomous and generally plays a reasonably good game. Occasionally it will fail to pick up a piece and also occasionally misread a piece when scanning, particularly in bright light conditions but generally it is not too bad.




This was inspired by my daughter's constant requests for cups of tea to be delivered to her either in her bedroom or to the TV lounge.

Navigating accurately around a room is hard enough let alone going from one room to the next. So in order to better keep track of where the robot was I decided to use the grid of floor tiles as a guide.




This is not a compete project but rather something that could be used as part of another NXT project that requires user input, such as a game.

It consists of a keypad of 16 keys, in this case the numbers 0 to 9 plus a 'Backspace' key and an 'Enter' key. 




This started out as a balancing robot similar to the Gyro version of NXTWay and using Ramin's RobotC program.

This worked first time which caught me by surprise - I mean where's the fun in that? So I started playing around with the design. First I made it taller and taller but it still balanced ok so then I decided to see if I could make it stand up  again if it fell down.

The result is Toddlerbot.




Originally this was going to be a plotter, but part way through building it I decided to add a Joystick and make it play 'Pencil & Paper' games.

I choose three games, TicTacToe, a version of Combinatorial Regio and a simplified version of Salvo (or Battleships)

It can also be a plotter. Instructions can be saved into a file (nxtdata.txt) and then the robot reads these and executes the necessary actions.




When I asked my daughter what sort of robot I should make next, she replied 'Why don't you make one that plays checkers?"

Seemed like a reasonable idea so here is CPR (Checkers Playing Robot), a robot that can play checkers on a standard chessboard. (I would have called it CheckerBot but there is already another robot with that name.)



Beta Bob

This is Beta Bob (Alpha Rex’s cousin, aka PatrolBot), my best attempt at a biped so far. The legs are pretty much those from Omni-Biped in ’Creating Cool Mindstorms NXT Robots’ by Daniele Benedettelli. These are the best biped legs I have found: simple, smooth, able to reverse and turn, and most of all stable.



Holonomic Drive

"Oh no, not another Holonomic Drive" I hear you say. Afraid so.  It’s one of those ’must do’ projects so here is my attempt.

I used the HiTechnic compass sensor so I would know which way the robot was facing and could then calculate how much power to apply to each motor to move or turn in the direction I wanted to go.




So named because you get Four for the price of Two. This contraption is a gearbox that uses two motors. One motor changes the gears and the other provides drive to any combination of four outputs.

The idea is that not only do you get four output shafts, you can have any combination of them turning at one time, thus here are 16 different output combinations.



Balance Scales

This was my attempt to make a balance scale (or beam balance). It is pretty simple and worked ok but obviously could never be particularly precise due to friction at the pivot, flex in the plastic pieces and some jerkiness as the weight is driven along the beam.

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