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Color Sensor Values

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  • Color Sensor Values

    Has anyone else seen very little difference in the value readings for Red Vs. Blue using the MR Color Sensor?

    When the sensor is about 4-6 inches away from the beacon we get the following readings:

    When the sensor is pointed at the blue side of the beacon:
    Blue: 1
    Red: 1

    When the sensor is pointed at the red side of the beacon:
    Blue: 0
    Red: 1

    We can get Red to increase to 2 and sometimes 3 but have to have the sensor very close to the red side of the beacon for this to occur.

    Has anyone else seen this or is there another way/programming tricks to pull values that are a little more apart from each other when comparing the blue side to red side?

  • #2
    Which color sensor are you using? Adafruit, MR, HiTechnic..?

    Our team uses the MR color sensor, and have seen quite a difference in values. Of course, we disabled the LED as it is not necessary to sense light, so your reading may be different with it enabled.

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    • #3
      We are using the MR Color Sensor and have the LED disabled since we are reading the light coming from the beacon.

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      • #4
        I am not sure what typical performance in passive mode is, but the Modern Robotics specs state:
        "Best results in Active mode are obtained when the target is within about 7cm of the color sensor."
        Our experience showed that to get a decent range of values, we needed to put the sensor much closer than 7cm - more like 1-2cm for best results.
        I can imagine that passive is not a lot better coming from the beacons in some of the competition environment - ambient light (especially florescent lights) seriously wash out the beacon brightness.
        Further, the lights can become dim after several matches have been run without a battery change.

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        • #5
          We saw these values prior to calibration. The MR color sensor worked much better after we did the black level and white balance calibrations as described in the sensor documentation.

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          • #6
            We can read the beacon color values even from a foot away, in passive mode.
            Btw, you need to use the core device discovery tool for the calibration.

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            • #7
              Very good to know! I will look for that documentation and try it out.

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