Weird Robot Lag/Glitch

Some of our robots at school seem to be interfering with each other. Whenever We go to drive, it there is lag with the controller every once in a while, and sometimes it just spazzes out. However, when we take the robots home to practice, nothing of the sort happens. It could be that the radios are interfering with each other, but I’m not sure. I’m just wondering if anybody has had a similar problem, and if so, how did you fix it?

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Whenever the robots are separate it doesnt happen either, only when there are multiple in the same room

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Is this a v5 or cortex robot?

It’s just vex iq, middle school


Can you also post your code? It could also be that. Unless you are blessed with 60+ robots in your lab your problem isn’t going to be robot to robot radio interference.

Can you tell us the color of the radios you are running please?

If they are the black (2.4 Mhz) radios can you tell us where you are running them? Look up at the ceiling to see if you are directly under a WiFi access point. The higher power ones may be blanketing you field location.

I’m not able to give the code, there are about 5 separate robots so that might be difficult

Also, it couldn’t be the code, because whenever we drive the robots separately this problem does not happen.

We are using the blue radios

The blue radios are bluetooth, and with only 5 robots you shouldn’t have a problem with interference.

But lets do two things:

  1. If you only run them 2 at a time are there issues? Or is it only when all 5 are running at the same time.
  2. Is the radio firmware up to date? You can check by using the VEXOS utility and checking with the controller plugged into the brain.

1.) Actually i just figured out that one of our teams drove the robot by itself in the same building, and it was glitching. However he took it home and it was working perfectly, so it might be something in the school.

2.) Actually they arent, so Ill go update it and get back to you


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um, this isn’t a solution

The robots are only having this issue in the school, not anywhere else. We know that it is location related, what could be causing this? (BTW, @JakeLee and I go to the same school)

have you guys done enough testing to confirm that it’s really the location and proximity of the robots causing the problem, not that your robots just had some other issue (code/mechanical) while you were at school in proximity with other robots? I know pretty much nothing about iq, but seeing as there are competitions with tons and tons of teams all indoors, I find it unlikely that radio interference is your problem.


It does not have anything to do with the amount of robots driving at once (we originally thought this but I have driven alone at school with no other robots running and the issue has not happened). I have driven the robot at multiple locations within the school building, and it has happened in every one. I have also tested it at home, where it did not happen.


are contradictory statements.

Sounds to me like a code issue, or perhaps some mechanical problem causing inconsistencies. Or maybe some other variable is causing problems like battery charge, motors overheating, or connection issues. But radio interference seems an unlikely culprit to me.


You are right, we don’t have a solution yet, we don’t have enough info. But for 99% of us, we don’t see radio glitches. So thats why we are looking for more info

I pretty much agree with @Xenon27, but let’s do some more diagnostics,

The blue radios are bluetooth. So is it possible you have a bluetooth transmitter that is with you? Like your phone searching for your bluetooth headphones that are back in your coat pocket? If it’s radio interference there is a radio source you are searching for. You are really looking for “what is different here in school than at home”.

If we riff on @Xenon27 for a few moments, is it home=hardwood floor school=carpet. Since there is a friction difference, the battery packs will wear more on long use with a carpet.

How long does it take to glitch with a fully charged battery pack? 20 seconds? 2 mins? 10 mins?


sorry, i meant alone, at home

At both school and at home, we are running the robots on tables, so friction is not the problem. We encounter the input lag/undesired movements from the moment we turn the robot on (i.e. dropping risers by opening the claw, spinning in a 360), no matter the charge of the batteries. I am almost certain it is the amount of Bluetooth devices at the school that is interfering with the smart radios. That is the only difference between home and school that I could think of.

Ok, so now you need to find the radios. I’ve run events with 40+ robots in them and never saw a Bluetooth glitch. So search around to find the radio. You are looking for a Bluetooth type 1 setup, that would be the only thing that would have enough power to flood the robots (See the table about 1/2 down the page)

And that’s a pretty weird thing to see in a non-mfg environment.

A few posts ago I asked about the firmware in the radios. Can you verify you have the latest firmware in your robot? You need to run the test with controller hooked up to the brain via the blue cable.


have you done enough testing to confirm beyond a doubt that it never happens outside of school?

not sure if vexiq has this feature, is there a way to connect the controller to the robot through a cable instead of wirelessly, in order to see if the problem persists after completely eliminating that variable?

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Yes, it keeps happening over and over, and it is getting annoying so this is something that needs to be fixed. It could affect any tournaments that might happen at school. There’s a chance that it could be the repeaters that are located around the school, and they are interfering instead of the radios.

Yes, it does have that feature. We will try that when we return to school.

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