eV3 Color Sensor

P1190332( Right:  New eV3 color sensor vs Left: Old NXT color sensor)

The eV3 doesn’t come with separate color sensors and light sensors like the NXT.  Instead, it comes with a new eV3 color sensor which more accurately detects more colors as well as can be used in reflective mode as a light sensor to detect colors in a gray scale.

ev3_color_spread( Light dispersal from top LED which is reflected and read by sensor below )

In less common usage, it can be used to detect light shone upon it.  Surprisingly, it can be used like a near field ultrasonic sensor to measure short distances betwee 1.5 cm to 5 cm since it can read it’s own reflected light off a nearby surface and judge short distances depending upon the intensity of the light that is reflected back to it.

Here are two videos (parts 1 & 2) that do a good intro on the eV3 color sensor:


 

The eV3 color sensor is our most commonly used sensor.  Guidelines suggest setting the color sensor perpendicular to and 8-16mm above the mat surface with sheilding to avoid effects from ambient light.

The more in front of the drive wheels they are located, the sooner they can detect mat markings and better to effect changes based upon markings like turns.  The wider apart they are the more accurate squaring up becomes.  Both of these changes come at the expense of lengthing and widening our robot chassis respectively, which generally reduces manueverability, increases weight, etc.  – typical design tradeoffs we’ve seen all season.

We use it to help make our way around the field by:

– detecting and differentiating colors on the mat

– following lines and stopping at them

– squaring up to lines to correct for accumulated errors in driving/turning

The eV3 Education Kit comes with only 1 sensor so we had to order another for $35 to be able square up.  Ideally, we’ve considered using 3 to square up to lines in both forwards direction and sideways direction (if they weren’t so expensive).

Whereas we had a lot of spurrious problems with the NXT color and light sensors, the eV3 seems to be much better behaved.  The much fewer number of reported eV3 color sensor problems support this observation.

 

 

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