RS550 Causing Robot Disable

[Joe Johnson]

Originally Posted by djdaugherty

The motor and gearbox is face mounted to 1/4in polycarb; the motor is 6 inches away from the chassis.

But interesting - we did ohm out each motor lead to the motor case. And that motor seems to have values that go down to .9ohm as we spin it by hand slowly.

What should that usually be?

We were going down a path of a loose USB tether, our RoboRio. But we thought that should always manifest itself with a "communication" error, and it was just simply disabling without any noted error.

0.9OHM? Not KOhm or MOhm? If so, something is wrong with your motor. Why did you switch to this motor? Do you have another you can use?

I like that it's on plastic and not on the chassis proper but how is it driving? I know that in the year of the Banebot shorting motor fiasco, there were a number of teams that reported the problem when driving through chain or gears, even with the motor can itself isolated. Chain and gears are not great conductors but they do get a lot better when there is pressure squishing out all the grease/oil at the interfaces.

Maybe this explains the "it happens when we stall the motor" behavior?

Back to the resistance value of 0.9Ohm, if you DID mount this motor to something connected to the chassis frame, you may not pass inspection:

R38 All wiring and electrical devices, including all Control System COMPONENTS, shall be electrically isolated from the ROBOT frame. The ROBOT frame must not be used to carry electrical current.

The blue box says >3Kohm is the check.

I smell a rat in that motor...

Dr. Joe J.