Understanding Indicator Lights - IQ Controller (1st gen)

Using VEX IQ (2nd generation)? See this article.

Notice there are two different indicator lights on the Controller. The first indicator light is called the Power / Radio Link LED.

IQ (1st gen) Controller with its Power / Radio Link LED highlighted.There are two possible colors of the Power / Radio Link LED to indicate the status of the VEX IQ Controller Battery and of the VEX IQ Radio Link:

Power / Radio Link LED Color   Status

Icon of a solid green indicator light.

Solid Green Controller ON - Controller Battery level sufficient - with NO Radio Link (searching)

Icon of a blinking green indicator light.

Blinking Green Controller ON - Controller Battery level sufficient - with good Radio Link.

Icon of a solid red indicator light.

Solid Red Controller Battery level low - with No Radio Link

Icon of a blinking red indicator light.

Blinking Red Controller Battery level low - with good Radio Link

If the Controller’s LED is not blinking, the Controller is not wirelessly connected to the VEX IQ Robot Brain. Connecting with the Tether Cable overrides the wireless connection and the Controller’s LED will show solid green. Click here for instructions for properly linking (wirelessly connecting) the Controller with the Brain.

The second is called the Charge LED. 

IQ (1st gen) Controller with its Charge LED highlighted.

There are three possible colors for the Charge LED: green, red, and gray.

Charge LED Color   Status

Icon of a solid green indicator light.

Solid Green Controller Battery is completely charged

Icon of a solid red indicator light.

Solid Red Controller Battery charge in progress

Icon of a blinking red indicator light.

Blinking Red Controller Battery fault

Icon of an indicator light that is turned off.

Off Not charging

Click here for instructions for charging the Controller Battery.


Indicator Lights when Wirelessly Connecting

When wirelessly connecting a VEX IQ Controller to the VEX IQ Robot Brain, the indicator lights on the front of both the Controller and the Brain may display different colors. The different lights and flashing patterns indicate the status of the Brain’s and Controller’s connectivity and power.

Controller placed next to a Brain on a table, both powered on and connected. In this example, they both have green indicator lights.

Use this checklist when testing connectivity and understanding indicator lights:

  • Is the Power/Link LED on the Controller and the Brain LED both solid green?
    • If the answer is Yes, then the devices are charged but not paired. 

Follow the instructions in How to Pair the VEX IQ Robot Brain with the VEX IQ Controller for Wireless Operation

  • Is the Power/Link LED on the Controller and the Brain LED both blinking green? 
    • If yes, then success! Both LEDs should blink green when wirelessly connected. 

It indicates that there is a good connection and both batteries are charged.   

    • Is one or both of the LEDs red or blinking red? 
      • If the answer is Yes and the Controller’s LED is red, then the Controller Battery is low. 

Follow the instructions in How to Charge the VEX IQ Controller Battery

    • If the answer is Yes and the Brain’s LED is red, then the Robot Battery is low. 

Follow the instructions in How to Charge the VEX IQ Robot Battery.  

If the wireless pairing is still unsuccessful, be sure that the VEX IQ Radios in the Brain and Controller are a matching pair. Review the following:

For more information, help, and tips, check out the many resources at VEX Professional Development Plus

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