Hi,
[not sure if its a hardware or software problem]
I have build a kit for a car robot and am using the Arduino Uno as its brains.
On the work bench it works fine, but when I go out into the real work it looks like the program is going crazy.
Is there a common cause that makes your MCU go nuts?
PS: If you need more info, please say so. I will give all details that are needed.