Page 302 - Lego Mindstorms

Robot 9 • The SpinnerBot

Troubleshooting

Upon running the Capture-the-Flag program, the SpinnerBot should try to
lower its lifting arm and open the grippers. If the arm goes up instead of down,
try reversing the orientation of the electrical connector on the arm motor. If the
robot begins moving without trying to reset the arm, you need to check that
the arm motor is connected to RCX Output Port A, and that the main drive
motor is connected to Output Port C.
Once the arm has been reset, SpinnerBot will begin trying to move for-
ward. If it moves forward but turns while doing so, one of the wheels is having
a hard time turning. Make sure no loose wires or pieces are touching the
wheel, and try turning the wheel by hand to ensure it spins freely. You may
need to reach into the underside of the robot and wiggle the gears of the drive
shaft to make sure they are loose enough to not bind on a beam. If SpinnerBot
moves backward and turns instead of moving forward, check to see that the
light sensor is in place and is looking at a white part of the Test Pad. If so, you
will need to reverse the electrical connector on the main drive motor.
The SpinnerBot should reverse and turn when it reaches the black oval. If it
fails to change direction at all, check that the light sensor is in place and con-
nected to the RCX. By pressing the View button on the RCX, you can see what
light level the light sensor is reporting. Under very bright conditions such as
direct sunlight, you may need to lower the WHITE threshold in the program to
a lower value. If the light sensor is working properly, but the SpinnerBot
reverses without turning, the ratchet on the right wheel is not engaging. This
ratchet was added in Lower Arm Drive Step 5, and should have been set on
top of the 24t gear in Final Step 15. You may need to remove the Arm Drive
sub-assembly and try repositioning it according to the instructions. You can tell
if the ratchet is working: The right wheel should turn forward freely with a
slight clicking sound, but should not turn backward at all.
If the SpinnerBot does not detect a flag upon bumping it, test the bumper
by pressing it while watching for the small arrow to appear under Input Port 2
on the RCX LCD display. If no arrow appears when you press the bumper, you
will need to check the wires connecting the touch sensors to Input Port 2.
If the arm motor turns on and the grippers close but the arm does not move,
the rubber band might not be seated properly on its pulleys. Make sure the
blue band travels around the groove in the smaller pulley on the Lower Arm
Drive sub-assembly, and around the groove in the larger pulley on the motor of
the Upper Arm Drive sub-assembly.

Playing Capture-the-Flag

The Capture-the-Flag program causes the SpinnerBot to roam around the inside
of the black oval on the Test Pad, searching for a flag to grab. Try placing a flag

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