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Problem with MR Color Sensor

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  • Problem with MR Color Sensor

    We are using a Modern Robotics color sensor for our autonomous program, but we are experiencing issues with it.

    The wiring is all plugged in in the correct orientation and includes the MR color sensor, sensor cable that switches the wires, the level shifter and the cable that plugs in to the REV expansion hub. We have tried replacing all of these components and are still experiencing problems. The MR color sensor is currently plugged in and configured to I2C bus 3 on the REV expansion hub.
    These problems using Modern Robotics color sensors on our robot have been occurring all season. The problem is intermittent and random, we cannot predict when it will happen. We've tried to strain relieve the cables with zip-ties but that hasn't done much. In fact, cutting off the zip-ties seemed to help. Wiggling the wires also seems to temporarily fix the the problem. Sometimes the problem occurs even when the robot isn't moving. There really is no way to predict it.

    The error message we receive is: warning: problem with "color" (color is the name of our color sensor).

    Our robot uses two REV expansion hubs. We are using version 3.6 of the FTC app on Motorola G3 phones and deploy our code through Android Studio. The REV hubs have firmware version 1.7.2.
    Captain of Team 7593 TigerBots, NorCal Region

  • #2
    Did you ever find the cause of this issue? We had this and it was a bad color sensor. We replaced the sensor but the new sensor also went "bad" about 3 weeks later. I honestly think something is amiss between using a rev hub and mr color sensors.


    • #3
      Our team also experienced issues using MR color sensor this season that we were able to resolve and now it has worked reliably over three qualifiers. We are still using MR electronics but the general findings below should still be useful :-

      1. It may be an urban legend but never "hot plug" the sensor. It appears that we destroyed a working sensor from last season and had to purchase a new one.
      2. The cabling was the biggest culprit in our case. This season's game requires the sensor to be mounted at a considerable distance from the CDI and we used 2 extensions (bought from MR) end to end. The sensor will be momentarily turn on and then off. Pushing the wires would fix the problem and but then the problem will re-appear. I finally got tired and bought pre-crimped loose wires and connector housing from Pololu and assembled a single 2 ft long sensor extension. Plugged that in and the disconnection problem dis-appeared.
      3. When you get a new sensor, please do remember to calibrate it following the MR's instructions. Our brand new sensor after failing to correctly identify the red ball from the blue was tested and we found that it was reporting a bright red (255) value when pointed a blue ball !! The calibration step fixed this final issue and now we have no color sensor issues now.

      Hope this helps.


      • #4
        Unfortunately, we were never able to resolve the issues with the MR color sensor. At one point we found that there was a broken logic level converter that was the culprit, but the color sensor stopped working again soon after we replaced the logic level converter. Due to the issues with the MR sensor, we opted to switch to the AdaFruit RGB color sensor. We soldered the appropriate connectors for the Adafruit sensor to the other end of a REV I2C sensor to make one long cable so there are fewer points where a connection problem could occur, and this has been working much more reliably for us.

        voltemort I think I may have hot plugged a MR color sensor at some point when I swapped it out for a new one, whoops. With all the different components needed to make the MR sensors compatible with the REV expansion hub, there are so many points where the connection could be disrupted that there were probably connection issues as you said. If we ever decide to try the MR color sensor again, we will take your suggestions into consideration.

        Captain of Team 7593 TigerBots, NorCal Region