Brain and Control short out

While practicing and working with our robot, the connection between the brain and the controller goes in and out forcing the students to have to tether the two together to get it to work properly. Looking for suggestions on how to fix this. Thanks so much!

Hi smudgey20,

We’re sorry that you have encountered this issue. To help resolve this issue, please make sure that all of your VEX IQ control system devices have been updated to the latest version of VEXos (currently 2.0.1) using the VEXos Utility.

Once this is complete, please turn on the suspect Robot Brain and Controller that are having radio connection problems and separate them by the normal distance that they are when in use. On the Robot Brain, press the X button while on the Home Screen to enter the Settings menu, then scroll to System Info and press the Check button. The information on this screen will help isolate what might be the cause of the radio issues.

The first thing to check is the radio signal strength - this is similar to how “loud” the radio signal is. The radio icon on the top menu bar of the screen displays signal strength. If your Robot Brain and Controller are within at least 5 meters or so of each other, you should have at least 3 out of 4 bars of signal strength. If there is poor signal strength and your Robot Brain and Controller are close to each other, please make sure that the Robot Brain and Controller are located away from large metal objects - these can block some radio signals.

The second thing to check is the radio data - this is how “clearly” the radio signal can be heard. The Radio Data line on this System Info screen should display 100% or Good if the Robot Brain and Controller are within about 5 meters of each other. If you do no see either of these (such as if you see Marg (short for marginal), the problem is likely from radio interference. If you are using the 900 MHz Radio, some older cordless telephones from the 1990s and earlier used 900 MHz and may cause interference. If you are using the 2.4 GHz Radio or the Smart Radio, both of these operate in the 2.4 GHz frequency range. The 2.4 GHz frequency range is also used by Bluetooth and 2.4 GHz Wifi. If you are trying to drive a lot of VEX IQ robots in an area that has a lot of Bluetooth and Wifi devices in use, there may not be enough empty radio frequency for everything to work without devices trying to “talk over each other”.

To help isolate whether radio interference is causing these issue, please take the Robot Brain and Controller to a “quieter” area (radio wise), such as out in a parking lot or sports field/park. If the Robot Brain and Controller do not have any wireless radio problems out there, but do have problems in the school, the issue is likely the result of too much radio traffic in the school. In this case, turing off the offending devices (such as Bluetooth or Wifi if you are using the 2.4 GHz or Smart Radios) should alleviate the problem.

If you have any further questions or concerns, please contact VEX Technical Support at or by calling +1-903-453-0802 for more detailed help.


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