PTC Check at Worlds Inspection

So there has been a new update in the inspection check list.
You can see it here:
What I believe is that you must unplug all the wires from the motor port on the cortex and power expander so it is important that you make those easily accessible. I’m guessing they will have this device that they plug into the ports to check if the PTC is working as it should.

I made this thread just to let everyone know and get the word out.
This is also a discussion place as well.

I sure hope they don’t ask me to unplug my wires. It took me a while to get them all nice, and it would just be time consuming to get it all plugged in again.

I also have it behind a plexiglass plate because it’s RIGHT in the back, so I added that as protection for my cables to not get entangled with other robots; I would need to take that off too.

They did random PTC checks at the CA state championship. They pulled us aside right after a match and had us unplug one of the chassis motors from the motor controller (not the cortex) and he ran the motor and held it in stall.

I really hope they don’t check all ten motors on each robot. I think that one on each subsystem would be sufficient.

I’d hate to have to rewire my robot after inspection. I hope they do it like at CA states, where they only check one motor. Although at CA states, they forced us to stall our motor to check, which I didn’t really like.

They give the heads up to make the wires easy to unplug from the cortex here:

So I’m thinking no motor stalling is going to be happening.

I think your motors have seen a lot worse on the field (or in the pit area) than a quick stall :stuck_out_tongue:

We did get checked twice in one day which seemed a little unnecessary.

The PTC is in the motor though, so I don’t see how testing the ports on the cortex would show anything.

Same, I hope it is only one motor. I don’t want to rewire my robot either.

you plug in through the motor controller, the cortex also has some breakers too

It would be a lot harder for a team to modify the breakers in the cortex than to bend the PTC. It they are testing the breakers also, then I would expect PTC checks seperately.

I can’t even get half of my motors off without disassembling the frame. I can take the backs off and they can take a look, but actually removing the motors is not an easy task, and one I really didn’t want to do right before a huge competition. The same goes for the wires connecting the motors to the Cortex. I don’t want to get into detail here, but the wiring is… complicated to make work. To say the least.

Can someone from VRC explain precisely what this entails? I’d like to have 3 weeks to make it easy to prove my robot is compliant with the new inspection guidelines rather than try to fix whatever is done at inspection in 3 days.

It does say from that one picture that was linked that only the cortex ports and power expander ports should be easily accessible, and not the actual motor or wiring itself. You should be fine unless you’re like me and have plexiglass covering the cortex. (I can easily take it off for inspection, though)

We will be checking the motor, the Cortex, and the Power Expander at the Cortex and Power Expander. We are trying to make this as minimally invasive as possible.

At the California State Championships we made people cut into their nicely routed wire bundles to get to the 2 wire side of the motor connection. This was less than desirable.

We have devised new methods that allow us to check at the 3 wire side of the connection. I highly suggest you make the Cortex and Power Expander motor ports accessible as we will be checking every team at inspection and random inspections throughout the weekend.

This is a very short stall test. If your PTC is in the place it was during manufacturing, then you will pass the test with flying colors. If it is not, then you will most certainly fail the test.

VEX and the RECF is taking this very seriously. I suggest every team take it seriously, too.


Say the following wiring diagrams were to exist.

Motor → Motor Controller 29 → Y-Cable → Cortex

Motor → MC29 → Y-Cable → Power Expander → Extension Cable → Cortex

Does the stall test work through Y-Cables, or do I need to remove each MC29 from the Y-Cable in order for the motor to be tested? Does it matter if we’re going through the power expander?

If we are using Y-Cables, can I choose to expose the end of each MC29 in order for you to test the motor? I’ve sort of buried my Power Expander this year, but I can easily get to the MC29s, or even the blue, 2-wire leads from the motor itself. If both are those are options, is it actually necessary that I remove the Y-Cable from the power expander in situation 2 above? I’m just trying to figure out if I NEED to move the Power Expander, or if there’s another option.

Hi Paul

Thank you for implementing these checks to keep the competition fair. :slight_smile:

Regarding the random checks, can you please give consideration to the timing of these checks so that they are closer to post-match rather than pre-match? I am concerned that having motor stall testing done immediately prior to a match could hurt the motor performance of some teams in their ensuing match.

Many thanks, Paul

Completely agree the point. After a motor or Cortex that experienced stall, it will stall more frequently.

What have I done to deserve this.(I hate wiring and i’m really bad at it to)

I appreciate the measures taken to ensure a fair playing field. I have a few questions in how the operation will be performed. First, if drives are chained together, will motors have to be taken off, for an individual test. Second, what is powering the motors being tested, 9v battery, cortex, or some other power source. Third, will all motors be tested or just some. Fourth, and last, if one of these checks caused a team to be held from a match, because these checks may take a while. Is there any means in place to ensure a team doesn’t miss a match. Or, will inspectors check the match schedule, so a team won’t be inspected right before their match.

If they test them by stalling them, if you would stall all of the drive motors, the test could be achieved.

We have a 4 wheel, 6 motor, 1.6:1 drive base. Stalling it would take some effort. I guess we could drive it into a wall a dozen times, but I doubt that’s best for the robot.