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    NXTiiMote

    NXTiiMote is a remote control device based on a MindSensors acceleration sensor. You may control a vehicle through Bluetooth by tilting the remote, forward/backward and left/right. Additionally, a wheel and push button can control supplementary actions.

     

    Right view. The wheel drives motor encoder whose position is transmitted to the remote controlled vehicle. I use it to change the azimuth of the wireless camera built on the rover.

    The trigger button is also used at the beginning of the program to calibrate the joystick (set the zero position).

    It might also be used as a "shift key", to control two actions when the trigger is released, two other actions when pressed.

    Here it simply triggers a R2D2 sound played by the rover

    Bottom view. Here the remote is shown with Li-ion battery pack, but it works fine with regular batteries!

    Close-up on the acceleration sensor. I used the ACCL-Nx-3g3x (3G sensitivity, 3 Axis readings), but since only two axis are used here, the slightly cheaper 2 axis version (ACCL-Nx-2g2x) would work fine too.

    The rover is a slightly modified version of my Spy Camera Rover.

    A third motor was added to allow the camera to look up and down. It is controlled by the position of the wheel on the remote.


    Video

    Video showing how the remote orientation controls rover moves.

    The camera is equipped with 4 white LED headlights to improve vision in dark corners.


    Building instructions

    Printable building instructions (PDF, 1.6Mb).

    LDraw/MLCad MPD file.

       

    Programs
     

    The NXTiiMote NXC program sends the controller orientation and wheel position to a remotely controlled NXT robot. I choose NXC because when I wrote this program NXT-G blocks to control acceleration sensors were not available. It also allowed me to experiment with NXC to NXT-G Bluetooth communications. The only catch is mailbox numbering (NXC maibox n matches NXT-G mailbox n+1).

    June 2008 update: Daniel Sirota sent me a version of NXTiiMote program adapted for LEGO/HiTechnic acceleration sensor. Also included here.

    Use the "remote-z" program on the modified Spy Camera Rover.

    Bluetooth mailbox usage:

    • Forward/Backward joystick value is sent as a signed value in mailbox 1 (0 in NXTiiMote NXC program)
    • Left/Right is sent as a signed value in mailbox 2 (1 in NXTiiMote NXC program)
    • Trigger button sends a message in mailbox 3 (2 in NXTiiMote NXC program)
    • Azimuth wheel sends a signed value in mailbox 4 (3 in NXTiiMote NXC program). The value is clipped to avoid mechanical lock of the camera orientation motor.

    Usage

    • Level the camera a
    • Start the "remote-z" program on the rover NXT.
    • Establish Bluetooth link between both NXTs from the NXTiiMote (the link must be established from joystick, using slot 1 to use the programs without modifications)
    • Start the NXTiiMote program (the program first checks for a valid Bluetooth connexion).
    • Level the NXTiiMote
    • Press trigger button
    • You are now controlling the remote robot.

 

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