We are using a new brain. The teams having problems are all new teams, so new brains and new motors.
Are you testing with a new brain? Maybe that will increase your chance to reproduce the issue.
We had one motor die on the intake, the intake had just a little bit of friction, and it was running at 95% power. Then we had two motors die on the flywheel, the flywheel had minimal friction and we kept the acceleration steady and slow enough. I recieved these motors in a V5 Super Competition Kit in August of 2022.
Same problem here. My group had 2 bots at competition, we lost 6 motors that day, light, normal use (nothing geared high or overloaded.
The Vex site says “thousands of hours of engineering” went into the new v5 motors… apparently not thousands of hours of testing though? As an electronics engineer, I cannot believe these circuits do not have a shut-down to protect itself from dying (overload, overheat, etc). Or, if they do, these board revisions are faulty in some other component. Vex desperately needs to make this right.
@levipope please update this thread when you have a solution. Thanks!
Our team has trouble with the motors too, but its only for the motors bought from the new suppliers. None of our previous motors has died yet
I apologize for the radio silence on this thread. I just want to let you know that this topic is on the top of our priority list and we are working on it diligently to make sure it gets solved.
Here are the updates I have:
We have collected enough failed motors to know that the issue only happens on revision 10 of our motor PCBs. What we have determined is that something is causing a diode to fail on that revision. When that diode fails it brings the power rail down on the entire board and the processor will not boot.
We still don’t understand why some motors fail and others don’t. But we have been able to replicate the failure but only by aggressively back driving an unpowered motor. Obviously that is not how all of these failures are happening. Unfortunately, we have not been able to replicate the issue on a robot. But it could very well be that we are not accurately able to recreate the environment where these failures are happening. Regardless, we are still trying to replicate and are also working on solutions to protect that diode and resolve this issue.
We are currently working through all of our inventory to make sure we do not ship any Rev 10 boards. As soon as we have a solution for this issue we will arrange to rework/replace the remaining rev 10 boards that have already shipped.
Thanks for the great update! I’m glad to hear vex is working on it.
Quick question: what do you plan to replace the Rev 10 boards with? I can’t imagine that the motor shipment time will do anything but go up, but I’d like to know if that is definitely the case or if there is another plan. I’m imagining teams sending in motors to be reworked/replaced expecting quick turnaround times and ending up not having any motors rather than having potentially fallible motors.
Great question. We will need to figure out a few things before we can nail down exactly how this will work. First we have to find out how many pre rev 10 boards we have in the warehouse and at the factory. Second we need to know what the final fix is for the rev 10 boards.
Once we answer these questions, the goal will be to throttle the RMA process so that we will only take the motors that we can quickly replace. Hopefully that will minimize the down times for teams.
For those of us at home, how do we identify the Rev 10 motors without opening them up? I’d rather not install them on robots if I can manage it. Thanks!
I would say that any motor with a date code that starts with a 22 is suspect. But that is not 100%. We are working on a way to detect this with software and we will release that when we can.
Sorry for being off topic here but when I saw your pfp at first my heart had skipped a beat. I though that the VEX account had come back again.
(Which hopefully it will never rise from its grave again)
We just had 2 more die the other day.
This one is the motor that spins the intake and the roller mech. Team is attempting to build a sensored roller mechanism with an optical sensor.
They encountered this nasty lag/delay between the time the sensor reads a change in color and the time the motor stops (HOLD). Not sure if electronic, program related or mechanical inertia but this results in the roller being spun way past the intended mark.
The programmer decides to “fix” that temporarily by adding a slight delay and reversing the motor to spin the roller back to the desired position. We warn him not to do that as reversing the motor like that can put a lot of stress and burn stuff. Programmer rebuts with “but our driver has buttons for forward and reverse and HOLD in between and mashes those buttons like a madman and motor is fine”. Fair.
So we try the code and motor does not even attempt to spin but goes dead instantly. We abandon the reverse code and just reduce velocity to the dismay of the team. After a few batteries and attempts at figuring things out the second motor dies the same way.
We opened them and they were both Rev 10 with a “22” date. The only thing I can think of is the fact that we are pushing these motors hard with “spin with voltage” commands in the max 12V zone. But after they die we always revert to “spin with percentage” at 80% or even more conservative. They still die. Did not find a pattern yet. Now we are afraid to test anything as there are no more motors.
Unfortunately we never connected the dots at the beginning of this saga and motors are not labeled and are mixed up in a box so no way of telling what rev is what without opening. I’m tempted to believe that spinning the motor with voltage at 12V has something to do with it but it could be paranoia/coincidence. But every dead motor this entire season was 100% a Rev 10 with 22, that is absolutely certain.
Thank you @district9 for the detailed explanation. I will add steps to our current tests to see if we can replicate in this way.
There are some small screws on the motor that hold the cartridge in, if you take these off, it will decrease the friction and give you a better test of the motors. If they still don’t spin, you can always take apart the motor and clean the internals. It is a little tricky, but you should be able to get it done with some elbow grease and dawn dish soap
Which would work except that’s not the issue with these motors lol. You’d know if you read what Levi had to say mbruh.
Had one die today. Is there an update to this?
We killed one more as well since my last post. Opened it and the board says Rev 10. We now open every motor and make sure they are Rev 7. Wonder what happened with Rev 8 and Rev 9, VEX went the Microsoft Windows naming way?
I don’t know if you understand this situation. The motors aren’t being locked up, they are:
Also, just had our first new motor die
We had about 5 die on us last season. We opened 3 of them and they all say Rev 7. As far as usage or programming pattern, they just all seemed to be random for us. We have since bought anti-static spray and that has seemed to help (knock on wood).
This seems like a big issue that could make or break the remainder of the season.
Why don’t you share details of what you know so far with the rest of the community?
There are plenty of experienced electrical engineers among mentors, that would be happy to look into the problem and share some thoughts.
For example, are you collecting student code that was used to run failed motors vs your test code?
If you determine the failures to be associated with the specific usage pattern then, in the ideal case, you may be able to fix it with firmware update.