Worlds VEXNet dropouts

There have been quite a few drop outs with the new VEXNet control systems on the field. our team alone had 4 drop outs. We even had one match where one team from each alliance dropped out and they refused to give a rematch when both alliances asked for one. We were wondering how many teams have had their VEXNet drop out on them. Could teams please fill out the poll indicating how many matches, if any, they dropped out in?

I had it happen three or 4 times at last year’s worlds, once in each quarterfinal match.

VEXNet has never been nice to me.

The specs for next year allow the dongle to be connected to an extension cord. If you put the dongle in a nice, exposed, high place on your robot, disconnects will hopefully be a thing of the past.

Apparently, the problem came from an accident of a staple in the wires. They found this after taking apart the fields. We chose to use our own vexnet and never had the problem of it cutting out.

I didn’t like the setup and stuck with keys, our partners lost connection three times, all of which were matches we lost…

we had vexnet dropout multiple times on us at worlds (more than 4). for the practice round and the first 3 qual rounds it dropped when we dropped moveable bases under the ladder (probably indicating something loose). our connection returned after 5 to 10 seconds usually each time. our partners did not have this good of luck and 1) did not move or 2) went crazy and lost control. The second one of these things happened to another one of our teams in our club. their bot drove in circles (one side of the drive goes one way and the other goes the other). this seems like an issue where a bot gets stuck in a single case of an autonomous mode. im not exactly sure what is up with vexnet, but something is wrong with it…

I saw this happen once, and it was on the Technology display. I may have seen the same match. That seems strange, but I’m not really seeing it as a VEXnet issue… More like a programming/downloading error.



Before the rumor mill pushes this thread out of control I want to make sure that only FACTS are shared in this thread. We played over 1,100 matches over the last four days not including Skills Challenges with various skill level robots participating. I want to make one thing very clear: When your robot is moving erratically, it has NOTHING to do with VEXnet. With VEXnet you are either moving or you are not. “The Field” does not drive motors or servos, etc. It only tells you what state you are in and, in the case of the remote power used at VRC World Championships, provided power to the joystick and the remote key for the wireless link.

Again, if your robot was moving at all, then it was your code or a hardware issue with your robot … period. The VEX staff and technical volunteers took as much time as humanly possible with robots having problems to try to conclude what was happening. I personally helped at least 4 teams chase down mechanical and electrical problems.

Some teams would lose VEXnet communication on occasion. The cases I saw were:

  1. A loose connection between the usb key and the Cortex so that when it hit something you would lose connection.

  2. A loose power connection that would cause a loss of VEXnet connection.

  3. A bad key on either the robot or the joystick*.

  4. Improper gear ratio using the new 269 or 393 motors causing the thermal fuse to trip.

    • I actually did not witness this case personally.

With all of the above said, the staff at VEX Robotics puts the customer experience above all else and we will be working hard this year to try some things to make items 1 - 3 less common going forward. At the end of the day, making sure there are no loose connections are the team’s responsibility so please make sure your connections are solid.

Regarding item 4, my staff will be publishing technical data and easy to use charts to educate our customers on proper motor and gearbox sizing for VEX Robots.


our issues were not due to a loose vexnet key or battery as both were tightly ziptied to the cortex to allow for almost no movement. we used multiple sets of keys also because of thinking they may have been the issue. our motors did not trip in any of the matches that vexnet dropped so i think there must have been a different issue. thanks for the suggestions though. a loose vexnet key may have been an issue for another team in our club.

I know that there was lots of interference from people running WiFi networks in Math, I think they had similar issue, though less often, in Engineering.

I wasn’t at Worlds, but I just had some Vexnet dropouts here at home for a few minutes… then I realized my USB key was lose. :slight_smile:

Tape it in, and check it every match.

The FACTS are that there were WAY too many cases of teams losing total control of their robots for portions of matches for that majority of them to be connection related. If they WERE connection related, it seems to me it’s a design issue that needs to be addressed.

As a mentor, I was very disappointed at the performance of VEXnet at Worlds.

TEC dad

Luckily that only happened to us in the practice match. We found that the orange USB cable fell out way too easily.

Could velcro maybe be added in the same way many people hold their vexnet keys in?

Our first major cases of VexNet disconnection happened at the World Champions. This definitely could be attributed to loose keys or other mechanical or electrical failures on our part. Then again, it happened around 3 times for us on Thursday, but no issues occurred on Friday and Saturday.

Ya we had 6 of our matches were our robot did not work because of Vexnet. We would have done a lot better if it was not for this. We were 4-5 and ranked 58th. lucky the 3rd seed picked us. Then we didn’t work again in the quarters… we let down our epic alliance parterners. I felt so bad for accepting, i mean it wasn’t our fault… I can believe what happened to our team at worlds. good thing the judges liked us and helped us. We won excellence. hopefully we will do better next year in our home state. Worlds is in anehim, and we are about 30 minutes away. hopefully do better next year.

Luckily, our team chose not to use the new system for power.

We did recognize the Velcro usage as one of the Chinese teams rammed us in autonomous, affecting the microprocessor. A lesson learned the hard way-

In the math division, there was a noticeable amount of wifi connections. It showed no effect on our performance though.

The majority of wifi problems occurred on the first day of competition (to me, it appeared that way).

We never had any problems with VexNet because we stopped using the orange cable and instead used our own key after hearing about the problems.

However, we did have problems with Number 4 on Paul’s list. After a competition and hours upon hours of practice on a full field, we never had any problems with the 393 motors on our drive train overheating, but at worlds we had these problems in almost every match. It may have just been that we were driving too erratically, but regardless, it cost us a few qualifying matches until we learned how to deal with it. We ended up in 54th place in the Engineering division with a 4-5 record, but luckily, the First Seed realized our potential and picked us. Unfortunately, we blew a 269 motor out in our gear tower in the last quarterfinal match which allowed our opponents to catch up and win.

We hope not to have any of these problems next year, and we will certainly not use the same drive train again. Good luck to everyone in the coming season.

We were in technology and there was just as much interference.

ours was ziptied in but it still lost connection at times. we tried a few different sets of keys too so that was not the issue. i think it was with the fields’ vexnet keys possibly overheating and the slightest jolt causing them too lose connection.

i was dissapointed too as we lost our only 2 qual matches because of our partner dropping out. it costed us in elimination too…

i talked to the vex engineers and they know about the issue and said that they would do their best to work it through before next season. our 269s overheated and i would not say that we were overdriving them. being rammed for 5 seconds should not kill the motors for the entire match… something needs to change for next year.

is there any possibility that the placement of the field VEXnet key behind the lexan and the field metal could have caused the interfearance that teams had. There is the suuggestion that no metal should be surrounding te key. Also could a robot driving infront of the key cause the drop out issues. There has never been any of these problems when teams used their own keys only when they used the field keys so maybe the placement of the field keys.

If all of the different keys failed, then it seems like your connection is loose. Where did you put the zip tie? I don’t see many places on the Cortex for that kind of thing.

That situation is exactly how motors could fail. If you have 4 motors geared for speed on a heavyish robot with traction wheels, a 5 second pushing match could definitely do that.