I am a 5 year veteran home based coach with a 2nd year team of 10 year olds. We are working with a Mindstorms NXT system that we purchased new last year, with a fully recharged battery. We are experiencing several intermittent erratic behaviors (listed below) that is driving our team crazy. Please let us know if you have any debugging suggestions.


Observed behaviors:


1.       After completing a planned series of instructions, with the last instruction having 2 wheels turning equally (straight line), the robot suddenly makes an additional turn (one motor, rotating robot about 30 - 40degrees). This occurs even after deleting the program, recompiling and redownloading it, and even after adding an all motor stop block to the program. Our team is referring to this as a ghost and are convinced that the robot is now haunted, just to get us in the Halloween mood.

2.       The robot, using a two wheeled turn (one motor going forward, one going backward) intermittently turns too far or too short. Programming is being done in rotations for both motors. Because both motors are running together, I can’t tell if it is related to the problem above. This occurs about 1 in 5 runs.


I do not think that this is a cable issue, as we are not seeing anything beyond the usual minor navigation errors due to lineup, wrinkles in the mat, etc. That leaves the motors and the NXT itself. Could this be a bad servo motor and if so, is there any way to test them?


Appreciate your suggestions!


Bob Henshaw

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