EV3 basics course. Touch Sensor. Programing. Pressed/Released (part 2)

We create a program for detecting when the Touch Sensor was Pressed/Released. Move until it is pressed, continue when it is released.

  • #139
  • 08 Oct 2015
  • 5:04

This is a simple tasks for introducing students with both states of the LEGO Mindstorms EV3 Touch Sensor. 

Previous video tutorials:

Instructions for building the EasyBot are available at:

Touch sensor Pressed/Released

EV3-G program for detecting pressed/released states of the LEGO Mindstorms EV3-G Touch sensors


In the previous video we attached the touch sensor to our robot and we did a small very simple program that moves the robot forward until the touch sensor is pressed. Today we continue using the touch sensor.

The next program that I would like to build is the following: the robot stays in place, the touch sensor is pressed and the moment I release the touch sensor I would like the robot to move forward for one rotation. So initially the button is pressed, but when I release the touch sensor the robot will move forward. Let's see how we can program this. The previous program was moving the motors, then waiting until the sensor is pressed and then stopping the motors. The current program should work in reverse, so we must first wait until the sensor is pressed, then we start the motors and we rotate the for let's say one second.

So the first block in our program is actually waiting for the sensor to be pressed and when the sensor is pressed we'll move forward. We start moving forward for one second. Let's download and see the program. I'm downloading the program.

Now the robot is not moving and the moment I press the touch sensor the robot will move forward for one second.

Again. Download the program. It waits for touching the sensor and then it moves forward. But that was not our original task. Our original task is to have the sensor pressed and when we release the sensor to move the robot forward. Let's program this. What we have to do is to configure the wait block for the touch sensor, to wait not for a touch, but for a release. To wait for releasing the touch sensor. And from the option right here, the state. Let me zoom a little more. If we change the state from pressed to released, then this block will wait for releasing the touch sensor.

Let's check this. Downloading the program and running the program. I download the program.

And because the sensor is released, it initially starts. Again I will download it. It just moves. But if I now press the sensor and I start the program, the program is currently running, you can see the green lights here and now when I release the touch sensor it will move forward.

That was for the second state of the touch sensor. Now let's take a look at the third state, before we end this video. The third option in the wait block for the touch sensor is bumped and bumped means pressed and then released. So if I now select the bumped option, I will have to press then release and only then the robot will move forward. Downloading and running the program. Position the robot. Now I'll download the program.

Download. Currently the program is running. If I press the sensor, the robot doesn't move. Now if I release the sensor, the robot moves. So it's the bumped state of the sensor, when I bump it, the robot starts. These were the three states of the touch sensor- pressed, released, bumped. Let's do more programs in the next video.