Weird IME Problem

We are trying to get a scoring autonomous going, but some weird things are happening when we try.

We first tried just letting it go:

Move(1000, 127);
Right(-100, 63);
Move(-500, 127);

It did that fine. Then we tried aiming it at sacks, and I think when it touched a sack, it messed the whole program up. I’m not sure. It works fine with no sacks, but when it has sacks in it’s way, it messes up.


If you replace the Sacks with a different object does it still mess up?? How about a Wall or Large Unmovable Object?? Your Hand??

I would guess this is either a Static Issue, or the Bot is being Slowed Down by the Sacks and not arriving Where it Should, When it Should…

We were having some of the same issues. However, it seemed to be unrelated to the sacks. I can definitely see static being an issue, though. We force-redownloaded firmware and code and after one test, everything was working fine. I plan on doing some more testing over the next couple of days.

It may end up being that we have to redownload firmware/code every couple of robot usage hours :confused:

Just to add on specific details:

One time we got the first part of the autonomous to work (one movement to get the sacks), then one of the encoders made all of the motors reverse. That was probably related to the sacks. We redownloaded the code (not firmware) and then the robot would go completely different directions than what was assigned. We ended up taking of the autonomous entirely due to the IME failure… it cost us at least one match.

I plan on dealing with redownloading firmware/code every once in a while for the rest of the year, but until the issue gets directly addressed, I’ll be sticking to the optical encoders.

Team 24C and our team have both had problems with IMEs collecting static electricity and sending it to the brain. This can cause several different problems, most notably the robot doing whatever it was doing when it bugged out, infinitely until you turn it off.

The IME’s are the only sensor that has exposed pins (due to the method of daisy chaining)… which are made of copper… copper having less resistance than steel will attract the static to those pins directly…

So I would suggest either plugging an extra 4 wire cable in the open port or putting tape over the port… so the static does not have a direct route to the exposed pins…

Vex should include caps for the exposed port Just a 4 wire cable end with no copper on it or wire attached… this would probably alleviate a lot of problems from static… also if you do not have an extra 4 wire cable if you took some 2 wire ends and trimmed then down it should work the same way… this should be legal as long as you explain to the inspectors what this is for…I will ask a QA about it because tape is illegal for that use… and I do not want to spend 20 bucks on some 4 wire cables…

With the static issue being talked about lately, has anyone tried to use a ground wire?

I just asked a QA about modifying wires to prevent this for those of us that do not have extra 4 wire cables…

Hey, same here!

Guess everyone is coming up with the same idea.

I pondered that originally but the foam field is probably not the best grounding path. With so much of the field elements and other surfaces being non-conductive, what would you ground to? Would running a ground strap to the field keep it from static charge build up or since the field itself is non-conductive foam ground to anything?

And yes, this is totally non-hard evidence based thinking at this point… But seems to hold true anecdotally…

The floor mounts for the troughs are metal, right? If your grounding wire ran across one of those, that MIGHT work.

I see it being an entanglement hazard, though. Robots already get tangled with well secured wires.

Grounding wires worked for FTC which uses the same foam tiles and IFI field perimeters. Entanglement shouldn’t be an issue if the wire is placed out of reach of the other robots.

I don’t think you could protect it well enough. And besides, what would you use as a grounding wire, per <R15>?

We’ve done quite a bit of experimentation. Covering the exposed pins at the end of the daisy-chain doesn’t help with static. Dragger chains don’t seem to help either. The best bet is to spray the field tiles with an anti-static spray – which we do at VEX World Championship.

We will continue to look at ways to help “bring the Cortex back” from the weird reset condition caused by this static.


Oh, that’s awesome. So, we shouldn’t worry too much?

Trust, but verify?

We’re going to continue to look for ways to help alleviate the problem, but we are very confident that the static spray will reduce the ESD events at VEX Worlds such that they aren’t a problem. The weather in Anaheim is also helpful :).

If you’re concerned, I encourage you to test on a sprayed field, and see how you feel about it.


Will we see an update by beginning of the '13-'14 game season? (October-ish, in my mind)

We will try to provide an update by then, but I can’t say for certain.