V5 Motors freeze after a period of time

Hello everyone!

Yesterday my team was experiencing some problems with the V5 motors on our robot, where they freeze up (as they stay put) after a certain amount of time. Turning off the Brain lets the motors loose up, but the problem consists after trying to use the motors again.

I don’t believe it’s a coding issue, since all we have been changing in the code is autonomous for the past several weeks. The motors freeze up when operating in both driving manual and autonomous. We’ve also tried using a different motor, but the problem still ensues.

We have several plans of action to try and fix the problem (Listed from easiest to hardest):
Reset brain and upload code again - Though I still believe it’s not a coding issue, this would be the easiest thing to do first.
Switching the controller - The motors may be frozen because it’s not receiving any input. The motors are coded to hold if none of the buttons are pressed.
Switching the brain - The brain itself might have an issue. We’ve updated it to the latest firmware, but the motors still act up.
Replacing the wires - We have been using custom cables to run the motors throughout the season. They might have worn down after some time. We could try using new custom cables or use the assorted ones VEX provides. This would be a bit time consuming though and we only have a few days before our state competition.

The motors could have also just have stopped due to overheating. I’ve been heavily testing autonomous for about an hour before this issue began. It’s been several hours since we’ve used the robot, so maybe it’ll just work fine later (hopefully).

Any advice or opinions on our issue would be gladly accepted. I’ll update on my team’s condition as we try to fix this problem.

You could try creating a new program that does something really simple like run a motor, and see if it still freezes. If not, then it’s a coding issue. If it still does, then it’s a problem with something else

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it is most probably an overheating issue. Have you tried inverting a compressed air canister and blasting the motors? that’s what my team did when this happened

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Both of these ideas might be worth a shot.

First idea

The motor brake type of hold is a bit of an odd thing.

How does braketype::hold work? and thoughts about it

The active usage of the motors could cause the motors to overheat (and lock I suppose). I would suggest that you change the motors to use braketype::brake instead.

Second idea

Our motors have locked up from ESD (electrostatic discharge). It happened suddenly for a good couple days. The brain port would be damaged, we switch the brain port the motor si plugged into, then the next brain port gets damaged. We resolved the problem by putting electrical tape around the port on the motor and switching the port. Haven’t had a problem since.

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I think this is most likely your issue if the motors are under any prolonged or repeated load. I had a motor on hold that was constantly being forced to hold its position, and it ended up locking up. Letting the motor rest and cool allowed the motor to work normally again

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Look in the brain log, that will show any motors that are overheating.

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We use braketype::hold for the V5 motors, since they are used on the arm of the robot. We could possibly implement braketype::coast when the arm is down to reduce power. But I don’t think braketype::break would help since it still uses power.

Edit - changing braketype::hold to braketype::brake did seem to help quite a bit. It seems somewhat weird that braketype::hold might be causing the issue, since we’ve been using braketype::hold for several months for our bot without many issues. We might make a button that toggles between brake and hold to “reset” the motors.

One of my teammates tried putting an ice back outside the motor to help cool it down, but it didn’t really help. Compressed air could help cool the motor, but that might cost quite a bit.

I would replace the cords with vex assorted ones becase the coustom cords have always had alot of problems

First thing I would do is really make sure it isn’t the program. Aside from overheating that seams like the simplest, thus most likely, answer. On the brain go to devices, click on one of the motors and try running it from there. Does the issue still happen?


Also do check the log like jpearman said…

How to view the log.


With this information I am sure we can diagnose the issue further.

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After testing the motors individually, we found that one of the motors overheated much faster than the others, to the point that it eventually stopped moving. All the motors are used to operate a DR4B, so one of them caused the whole left side to stop moving. We switched the faulty motor out with a new V5 motor and all the motors seem to respond well.

After replacing the motor, the DR4B moves well but often clicks. My team found that many of the axles holding the gear train together were bent, probably from the motor malfunction. We’re planning to replace those axles a few days from now and see if it runs more smoothly.

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