We are one of those teams that decided to use V5 for this season. I am really regretting this decision.
Why V5 is better than the cortex just with some bugs that should be fixed (hopefully).
Our team hasn’t broken a port on the brain.
Why do I regret using V5?
Because we have only received 2 batteries even though we paid for 8 (back in May), we haven’t received the vision sensor, we only received 2 brains (and we bought 4), we only received 2 controllers (and we bought 4). We go 8 motors to start with (even though we bought 20). We have bought 20 more but don’t have them yet. We didn’t get any of the different motor cartridges (100rpm, or 600rpm) even though we already paid for them. We bought the wire wheel and but haven’t receive it. VCS can’t talk to the brain wirelessly - lots of fun to program a VRC robot dragging a wire connected to your laptop. VCS generates a binary file that doesn’t properly work with Gitbub, or any other source control system. VCS doesn’t save your work. And the list goes on.
When did you order the wires brains and etc. Plus vex is trying to give V5 to everyone that ordered it then sending out more. Just be patient their are plenty of tournaments to go to (or at least where I am). Also our team still hasn’t received our extra batteries and motors we ordered.
What length of wires are you using? We didn’t have any issues with ports breaking until we had to use longer, manually spliced wires on our robot. I suspect there’s a connection between using long wires and ports breaking, and i suspect it’s an issue on all V5s, and that as more people start attempting lifts with longer wires, the issue is going to start popping up more. I hope I’m wrong and the ports breaking are just a small number of brains that are faulty, but it’s just a hunch that I have. I’m guessing it has something to do with the eFuse implementation…
but in my unamazing drawing/ the image from vex 
I’m pretty sure our wires are made correctly, but I’ll have a look at that tomorrow to make sure the plastic connectors are properly oriented. I’d imagine if you had the wires not properly oriented, the motor wouldn’t run at all, whereas our motor runs for awhile, before eventually killing whichever brain port its connected to. However, I’m wondering if it could be something with custom spliced cables that’s causing the issues; Has anyone had failing ports with factory cables? Could people be poorly making the cables and having metal contacts touching and shorting? I don’t think thats the issue, but its a possibility.
ZoeChow (OP of this thread) said that he/she was using the 1500mm cables made by vex, so the issue seems to not be an error in assembly of custom cables (though of course the factory cable could have been made incorrectly).
We have several theories. Proving these is not easy (I’ve never manage to kill a port myself). It’s “probably” nothing to do with the eFuse or over current protection.
I am using factory cables, we have have many ports where the motors cut in and out.
That just sounds like overheated motors.
If the internal temperature of the motor reaches 55C we reduce max current, if the temperature continues to rise we reduce further until eventually we stop all motor movement.
It is not overheated motors. This happens when we just turn on the brain. I will post a video shortly.
I think there might be a relation to battery because most of this situation happens when it’s less than 50%.
In our case it is not battery related. This happens even when we just started the robot for the first time with a new battery. We are using the official cable sizes as we have yet to receive the 8m smart cable reel.
I have posted this on the other forum but thought I would only concentrate on Port issue here.
On our November 3rd competition, one of our team got three of their V5 port malfunction without any reason. They have been using this robot since October 6th competition without any issue. They have practiced for hours on this robot without any port issue etc. However on November 3rd competition, one of their port (Port #10) all of the sudden malfunction. They switched to different port and replaced port #10 to port #9. Forty-five minutes later, port #9 and port #17 malfunction again.
Here are some the details on Brain V5 port issue for one of our team:
Port #10 was used for the cap intake (about 4 1/2 feet long) and port #17 was used for lift ( 2 1/2 feet long). These two ports has been on the robot since October 6th competition. The same wires and motors have been on those two ports since middle of September and the team secured the wires really well with zip ties. They have been practicing for hours without any sign of issue.
These two ports do perform little different than the other six ports for the motors. Since port #10 (and #9) and #17 were used as part of the cap intake and lift.
- Port #10 and #17 uses longer VEX wires (4 1/2 feet and 2 1/2 feet respectively).
- Port #10 (and#9 broke within 45 minutes) and #17 programmed to have brake (meaning they don’t use stop() but instead, they use stop(brakeType::brake). Once the robot is on, the motors connected to those port always use brake. The motors never over heat so it isn’t motor being over heat issue on those malfunction ports.
Note: We have replaced the long wires with shorter wires with new motor, the broken port (#9, #10 and #17) never come to live again. The red lights kept on blinking but nothing more. We have waited for a day and reset the brain and retested those broken port but no luck. It looks like once it got itself into black hole, it stays in that black hole.
How can we get this issue fix? Do we need to return this Brain back to VEX?
I will contact you by PM.
@jpearman
Port 4 died on our bot during a tournament on Saturday. This motor was attached to our wrist which does not have much loading on it. The bot is primarily for flags, but can lift and flip caps. It does have mechanical stops for 180 rotation.
I’ve contacted support but we are not in an urgent need of a replacement since there are many ports compared to motors, etc. However, if you have a fix or need more info let me know.
The more I read read about this issue the more I am convinced that it is caused by the intermittent loss of connection in the ground line between the motor and the brain.
It seems that all reported port failures were associated with the motors at the end of some mechanism that is moving relative to the Brain. If wire connectors were not fully secured at the both motor and brain’s ends this would put them at increased risk of accidental loss of continuity in one of the lines.
Without seeing V5 motor and brain schematics (especially its circuit protection measures) it is just a speculation but, I would assume, that loss of ground line is the least thought about / protected against scenario and could have the most devastating consequences.
I have looked at the pictures of V5 internals posted by @sazrocks and didn’t see any obvious TVS arrays or zener diodes in their usual glass packaging protecting communication lines as is customary done with, for example, USB inputs.
If the ground connection is lost between V5 motor and brain, while the motor is running, could there be a voltage spike on the RS-485 data lines and is the brain being actively protected against it?
@jpearman, what are the color codes for V5 status lights? Does red blinking lights indicate no data link?
In the meanwhile, I would recommend everyone to secure wires on both ends to ensure that proper connection is not affected by any robot’s mechanism movement.
For one of the team, the wires were secured. They have adhesive foam on the wires on both the brain and the motors. On top of that, they also zip ties the wires completely close to the motor and on the brain. The only way to remove the wires is to cut the zip ties and push really hard to remove the wires. According to the team, they didn’t touch the wires nor any robot hit them during the competition. Basically, the wires on the brain and on the motors on those dead ports were untouched since middle of September. The port didn’t die while they were using it (motor running), they only found out the ports die when they tried to use the motors on those ports. Their ports basically just die while on the competition field while the robot is moving or the port die when they start the Brain. But either way, it was on the field that their ports die (twice).
Those dead ports do connect to motors with longer wires, i.e. 2 1/2 feet and one with 4 1/2 feet. I don’t know if the port die when turned on the brain or during using the brain (without actually using the motors on the on those ports).
I wonder if it is when turning on the brain with long wires connected to the motor, static, heat or combination that caused the port to die.