Rev Robotics Color Sensor Claibration

[shivsaxena]

Hello everybody,
We are trying to understand if the rev robotics color sensor included in the expansion hub requires calibration? If it does require calibration, how do we do it?
Thanks for all your help,
Team 11089

[suriono]

Why would you think it needs calibration ? It seems to work, when reading a reflective color with the LED on. Unfortunately the latest beta version 3.2 the enableLed(false) is not working to turn the LED off, thus it overpower a light source if you want to read the color of a light source.

[100101]

suriono, my team had calibration troubles at a competition with an MR color sensor even though we disabled the LED. Light levels can mess it up.
As for Rev Robotics I would assume it needs calibration, but I don't know.

[shivsaxena]

Thanks Suriono, 100101,
We are not sure either - if calibration is needed. We also found that enableLed does not work. We hope that there is a bit more documentation support from Rev. It says that it can also be used as a promixity sensor. But we have had very limited success with that too. Please do help if some of you know how to use this sensor.

[suriono]

100101,
Last year we found the color sensor depends on the ambient light, the sensitivity of reading value and how before sensing a color would increase with lower lighting. It is more likely about compensation than calibration. You can test if you need calibration by checking the reading value under the same ambient lighting, if it changes on daily or weekly basis, then there is a calibration issue. Or you can do a compensation method, do the ambient color readings at the beginning, compensate it when you do an actual color reading of an object or light source.

[shivsaxena]

Thanks 100101, we will give it a try. It would have been nice to have the ability to turn off LED though.

[suriono]

Answering 100101 question about proximity sensor, it worked within about 10 cm (thus the word "proximity" suggests). Beyond that the number could fluctuates wildly. You could check if the value fluctuates, and if not, the value is pretty accurate for distance sensor.

[shivsaxena]

Thanks Suriono for confirming the behavior - I believe our measurements were also along those lines - we freaked out a bit on seeing the wild fluctuations. However, the specification does suggest that the range should be up to 25 cm. For now, this will do.

• Built-in IR Proximity Emitter and Detector - 5 -25cm Range

[Rachel]

The REV Color Distance Sensor does not require any calibration before use. For color detection, the sensor should be placed about 2cm away from the target. If you are too far away the sensor sees an image which is too dim, or includes other colors around the target and will give poor results. The LED on the REV Color Distance sensor is always on and cannot be controlled via software. The light on is almost always best for the passive (not internally lit) targets like the ones in this year's game.

The proximity portion of the sensor works best from 5-25cm, less than 5cm the sensor will always output 5cm. This is an IR based sensing technology, so appropriate considerations to the use case and working environment should be followed. IR sensors are very susceptible to external IR light sources (some lights, the sun), as well as the material it's reflecting off.

You can use the example code in the SDK to test this device's features, check the example file: SensorREVColorDistance.java

Rachel from REV

[shivsaxena]

Thanks Rachel, we appreciate your help.