Interesting Information About Motors(Motors Stop Working)

I have been at several tournaments providing a live webcast of the competition and throughout the matches, robots would just stop working and would not be able to move on the field. I have been coordinating with the same people that bring the field equipment and the local event coordinators for arranging setup times and event configurations. If you like watching videos and prefer not to read, this youtube video explains everything related to PTCs, overheating and motor draws and loads.

I was told that my livestream was interfering with the field controls as it was only 1 of 3 fields that were having the issue. But now going back and looking at the footage there were more teams that were experiencing similar issues. Some teams were actually turning the joysticks on and off in the middle of driver control mode in the match.

I started researching into how the fields were operating and weather or not a livestream actually played a role in connectivity issues and according to another thread in this forum, the fields are operated through usb match controllers that control the field controllers(2 field controllers per field, 1 match controller per field). The usb is actually providing a serial interface to the joysticks through the cat 5 cables so I don’t see how network lag could cause an interrupt to the field controls.

Through another team/robotics program I helped start, I learned that they were having similar troubles with their drive train where motors would just stop working. They then explained to me the concept of PTC(thermal fuse for simplicity.

The VEX Cortex has 2 PTCs, one that operates on ports 1-5 and one for ports 6-10. Each PTC can draw up to 4amps before it is tripped. Each motor also contains a PTC, this one can only draw a maximum of 1.75amps for 7.1 seconds before being tripped and trips even faster the higher the demand for torque and friction. The video also clearly indicated that all fields were operating normally and the tournament software was in complete control of each field and each robot.

What I would like to know is if anyone else has done similar research into this and weather or not this is a confirmed idea or not. Is the PTC tripping a common issue for motors and other teams? If not, what else could be interrupting the signal from the joysticks to the robots?(We disable all wifi at the venue and only broadcast on the 5Ghz frequency for scoring tablets)

My final question is could the livestream have interfered with the field control in any way given the way the fields operate?(More specifically interference that can cause a single team’s robot to stop working but keep the link to the field working and all LED’s green-taken from video recordings)

There has been a lot of research into PTC operation, here is one thread.

PTC’s tripping in motors is very common, dealing with these issues is almost a “right of passage” for rookie teams.

Anything that is sharing the 2.4GHz band can potentially interfere with the VEXnet communication between joystick and robot. This can include conventional WiFi networks, 2.4GHz video systems and microwave ovens. The new VEXnet 2.0 keys are more reliable and able to handle the interference better than the older V1.0 keys but it is still a concern and most events try and limit potential sources.

You are correct in that field control is hard wired to the joystick, details on how that works is here, it is much simpler than most people imagine.