EV3 basics course. Color Sensor. Detect line (part 1)

Very simple and basic introduction to the color sensor in the LEGO Mindstorms EV3 set. The first program is to stop at a line. Then we can move from stoping at line to counting lines and even more complex tasks.

  • #147
  • 19 Oct 2015
  • 5:55

The EV3 Color Sensor detecs the color of an object. It could be in a range of 7 colors from white to black. The sensor could also detect Reflected Light and Ambient Ligth which generally means "how much light is the sensor receiving".

Check out the video tutorial and lear how to use the sensor

English

In the next few videos of the series we'll do an introduction into the EV3 color sensor. How we can use it, how we can detect different lines and how we can use it on the competition.

We'll be using this sensor, the color sensor to detect different lines on the table here and because of this the sensor must face down, vertically not horizontally. I'll remove the ultrasonic sensor from the previous tutorials

and I'll add the light sensor.

If we just use the same attachment to add the color sensor, I'll sometimes refer to this as a light sensor but it's more correctly to say it's a color sensor,

so if it is added like this it is facing forward but that's not what we want. We want the sensor to be facing down. So I'll use one more additional part in order to make the sensor face down.

Now there's some gap between the table and the light sensor. It's about one finger, so it's about cm or let's say half an inch. That's the distance between the sensor and the table. You cannot place the sensor very high because it won't detect the lines that are on the table and you can't place the sensor very near to the table because again there's not enough room for the sensor to work correctly.

The default port for this sensor is port 3. This here is the sensor. Now the programs that we would like to do are first we would like to stop at a black line.

I'll take this band and I'll add it right here on the table.

Let's now without entering into much details on how the sensor works try to make a program that makes the robot stop on this black line. First we need a block that moves the robot forward. We'll use again the Tank block and we are moving motors A and D so move forward motors A and D and we don't want to move for 1 rotation we just want to move forward until we detect a line. How do we detect a line? We add a Wait block as with the other sensors, with the touch sensor and with the MIndstorms ultrasonic sensor, we add a wait block in the EV3 software and we select wait. We are waiting for the color sensor to detect a color and this color would be black, only black. So move forward until the color sensor detects a color that is black. You can see here the different colors that we can select from and we want to detect black, because the line is black and then after we detect the line we want to stop with both motors.

Let's download and run the program. This here is the robot, this is the color sensor and now we start.

The robot moves until it reaches the black line and it stops and I can start the robot from different positions, for example, from here. It stop on the black line.

This is the basic way in which we use the color sensor. In the next program we'll try to stop at the third black line.

You can try it before watching the next video to build a program that stops on the third black line.