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Originally Posted by Mark McLeod
No case damage at all. All damage was limited to the FETs alone. The underlying substrate was unaffected.
It almost always involved different motors/speed controllers each time it happened (globe, drill, CIM). We never had a problem with a rebuilt Victor, and we didn't replace any of the motors this year. By Nationals all Victor problems had gone away, but we'd replaced/rebuilt a half dozen by then.
Static is a possibility.
Any ideas on tests we can run in the off-season? I'd like to make it into a research project for the students, but I don't want to risk expensive mistakes.
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The type of failure you describe is unusual from my experience. Even the number of devices replaced is unusual. Is there a possibility that your controllers were mishandled before install? i.e. students walking across carpets and picking up the controllers. Were they ever used in another application, testing or demo? Ever installed near bare metal or wire? Ever connected directly to a battery and motor outside of a robot without circuit breaker protection? The controllers I have experienced with failure due to over current or foreign material show charred and blown apart cases, high current types of damage and burned circuit boards. On our team we regularly use 8 or more controllers per robot. Over the years with both a competition and proto robot running near year round we have only killed 2 or 3 controllers in the years since they were introduced. (Wildstang has been around since 1996 but there were Tekins then and they failed all the time.) At least one of those was due to drill filings falling into the case. Have you disabled the dead zone in software? Is there a possibility that the controllers were always "on" just a little? Do you calibrate the controllers? Can you show a picture of how they are mounted in your robot?