[FTC]: FTC electronics issue - maybe metal shavings?

[BSV]

The kids are suddenly having some issues with the robot, and we want to make sure we are thinking of everything as we troubleshoot.

The motors are wired up like:

S1 --> Motor Controller 1 --> Motor Controller 2 --> Motor Controller 3
S2 --> Servo Controller 1 --> Motor Controller 4 --> Servo Controller 2

The controllers on S1 always work. Sometimes the controllers on S2 suddenly stop working for no apparent reason. If you unplug and replug any of them (even the last one in the chain), then they usually all reset and start working again. All of the controllers are pretty new.

Sometimes, when they've stopped working, if you bump the robot the servos might show a brief sign of engaging and stopping again.

As we were taking a closer look, we noticed some metal shaving on the robot around the area of Servo Controller 2 and the NXT brain. In fact, they were all over the robot. Apparently, the robot was near a chop saw that the FRC team was using and some of the shavings blew out all over the FTC 'bot. Nothing smoked, but we're not sure how much of an issue this is. All of the controllers read 12V when checked with a multimeter in their non-functioning state. We've no idea how those might affect the electronics. We believe when the saw was used may correspond with when the FTC 'bot started having issues, but we're not 100% sure.

We didn't have any way to clean them up today, but will try compressed air to blow things out tomorrow.

Any thoughts on other things we should look for? Thanks!

[MattRain]

Metal shavings on any electronics panel will cause problems. Check all of the ports/terminals for the NXT. Along with any of the terminals that are on the controllers. We have had things like this happen before, and it usually resulted in a small shaving in the terminal of one of those, or it was a bad NXT wire in general. A good practice is to store the robot way from any large tools.

[BSV]

Originally Posted by MattRain

A good practice is to store the robot way from any large tools.

Yes, we figured that out. Oops. Didn't think about the saw location as it had been mostly unused this school year until very recently, so the robot is now being stored in a different place!

Thanks for the info. We'll go through the plugs carefully and blow everything out with air.

[MattRain]

Originally Posted by BSV

Yes, we figured that out.

[IronicDeadBird]

Compressed air is a wonderful thing.

[jcarr]

Suggest that you rewire the controllers on S2 so motor controller is first in chain and the two servo controllers are 2nd and third.

Watch your current draw on the servo controllers. If over the 5A (easily done with the quarter scale servos), they can shut down for a time after maxing the current and it takes time for them to reset. Cycling power may not reset them, but they will reset after about 5 - 10 minutes.

Of course, metal shavings are always bad...

[pyroslev]

Originally Posted by jcarr

Of course, metal shavings are always bad...

Originally Posted by IronicDeadBird

Compressed air is a wonderful thing.

One is good and one is bad. When that compressed air drives metal shavings into a place where they can do more damage, that's worse.

Don't just drop the hammer on the compressed air. Take time and clean out the robot thoroughly to ensure ALL the shavings are out before you take the robot to the competition field.

[BSV]

Originally Posted by jcarr

Suggest that you rewire the controllers on S2 so motor controller is first in chain and the two servo controllers are 2nd and third.

Watch your current draw on the servo controllers. If over the 5A (easily done with the quarter scale servos), they can shut down for a time after maxing the current and it takes time for them to reset. Cycling power may not reset them, but they will reset after about 5 - 10 minutes.

Of course, metal shavings are always bad...

Thanks. We are using the Anderson power splitter and only three servos on each controller so we don't think that was it (and only one quarter-scale servo).

We replaced the motor controller and all seems to be well. Interestingly, I am told that one was being flaky earlier in the season, so it may or may not have been related to the shavings.

We carefully inspected everything and cleaned them off with compressed air. No issues at the moment.

Thanks, everyone, for your suggestions!