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Scribble Pad
Building: Intermediate
Program: Intermediate

Building Instructions








Attach a wire from the left motor to port B on the NXT and from the right motor to port C on the NXT.


Scribble Pad Programming

Use the program Scribble Pad for the Scribble Pad.  This program is designed to be as simple as possible in order to make it easy to understand, so it has a number of weaknesses.  See the Challenges section for ideas on how to improve it.


How to Use the Scribble Pad


  • A classic Etch-a-Sketch challenge is to draw a circle (or at least something close) which is amazingly difficult.  Give it a try!

  • Drawing on this scribble pad is very challenging for several reasons, including:

    • The dials are hard to turn because the motors have a lot of resistance.

    • The dials are too sensitive (turning just a little draws too much).

    • When you draw too far to the right and top, the line disappears off the screen.

    • When you draw too far to the left and bottom, the line "bounces back" and starts moving the other way.

    • When you double back on a line, you cannot see where you are.

    • You cannot "lift your pen" to put gaps in the drawing.

    • It is hard to remember which dial is which, and which way to turn them.

    Some of these problems are due to limitations in the NXT hardware or programming system, and some are classic Etch-a-Sketch problems, but many of them could be solved by improving the program or modifying the mechanical design.  For an advanced challenge, can you improve any of these by modifying the mechanical design or the program?

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