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Possible CYBOT Light IO Board problems

Following on from a post on the Forums:

problem:Cybots keeps spinning
One Wheel will not spin
Cybot ignores its light sensors

1. Possible capacitor damage
I have noticed on the discussion forums that a few people are having incorrect
motor behavious (spinning cybot etc ) with and without the light sensors connected.

The method used to determine the resistance of the LDR is to measure the charge time of a capacitor.

If this capacitor was damaged, resulting in open or short circuit, or
incorrect value, the resultant operation could be as reported.
It is possible for the end terminations (where the device solders to the board)
to suffer microscopic cracks during PCB manufacturing and handling.

I have tested the LDR / Motor reactions:

When operating normally:

With equal light on the LDR's ( Light or Dark ), both motors spin
With one in light and one covered - Only the motor opposite to light LDR spins

Capacitor removed:
(Also the same as the component being damaged.)

The motor on the faulty side does not spin
The motor on the good side always spins
(C10 suspect if it spins to it's left, C11 to the right)

Capacitor short circuited:
(Also the same as the LDR lead unplugged or poor connection.)

The motor on the good side spins with high light.
The motor on the faulty side always spins
(C10 or CDS-L if the it's left motor does not spin, C11 or CDS-R for it's right)


If your motor spins all the time, regardless of LDR light levels
Possibly a damaged capacitor

If your cybot travels in a straight line in high light, circles in the dark
More than likely a bad LDR connection.
Try swapping the left and right LDR's over first:
(if the fault moves, the LDR or connection is the problem