3. Lesson 3 - Greet a stranger

EV3 Phi. Greet a stranger with the robot. Introduction to the module

In this module we will program our robot to display emotions!

Do robots have emotions?

Most of the time they don't but we will learn how to animate our robots, so that they look more 'alive'.

EV3 Easy Bot v2

The second version of the Ev3 Easy Bot. This robot is used in classes with students as one of the first robots to be built. Easy to follow and to arrive at a construction even for first-time students.

Display block in the EV3-G software. Smiley faces, angry faces... all kinds of emotions

How to use the display block to show images with the EV3 software.

The display block

In the green "action" pallette, find the Display block.
By default, the mode of the block is "display file".
In the top right corner choose Lego Images and browse all preset images.
The "Big smile" image is in the "Expressions" folder.

Display block as a last block in an EV3-G software program

How to be sure your image on the display can be seen when the program ends.

"The image is in the program but I can't see it"

We hear that phrase from our new students every time. The reason is that the display block can't be the last block in the program.
When a program, running on a robot ends, the display shows the program's menu list, and your image is not visible anymore.

Wait a bit to see it

Put a wait block in order to be able to see the image that was the last block of the program. This way we postpone the end of the program and give ourselves some time to see the image.

Task: Try by yourself to make the robot make a sound

We encourage you to explore the software on your own.


Find a way to play a sound with the robot, using the EV3 programming environment. Choose any sound you like.

Be polite

Just make sure you respect each other's patience and be quiet with the volume settings of your computer and robot.

Task advanced icon Try to program the robot to speak

  • Find the sound block and try to play some words with the brick.

Sound block in EV3-G software. How to say "Hello" with the robot

Let's learn how to use the Sound block.

The Sound block

In the green "action" pallette find the Sound block.
By default, the mode of the block is "Play file".
In the top right corner choose Lego sounds and browse all preset sound files.
The "Hello" greeting is in the "Communication" folder.

Task: make the robot greet a stranger and leave

Explanation and demonstration of the big task for the module.

"Greet a stranger" challenge

The robot smiles, moves to a person or an object, sais hello, and returns back.
Use all the blocks that you learned so far, together.

Task normal icon Greet a stranger and leave


  1. Walk smiling to the person:
    • first put display block;
    • then add a move block.
  2. Greet, say "Hi".
  3. Return backward.


Task: Don't be rude, wait a moment.

Using Display, Sound, Wait and Move blocks together.


In order to be polite, you should wait for a response by the person you have just greeted.

Go to the stranger, say "hello", wait for a response, say "goodbye" and leave. Use all blocks you already know.

Try to find out how to make the robot wait for a while before leaving.

After five minutes go to the video section and see how we do it.

Wait block. Basic usage.

How to make the robot stay idle with the program is still running.

The Wait block

In the orange Flow palette, take the second block, the wait block. The default mode of the wait block is to wait for some time. You can set the number of seconds the robot should wait before the program continues to the next block.
You can think of the wait time block as a "pause".


Task normal icon Tasks to finish a class

  1. Take pictures and make videos of your robots
  2. Disassemble and arrange the robot
  3. Arrange your workplace
    • It is important to arrange the electronics of the robots on the cover of the box.
    • Wind the programming cable so that it is assembled.
    • Put the robot cables next to the electronics.
    • Wind the mouse cable around the mouse.
    • Wrap the cable of the laptop charger in a way that your teacher will show you.
    • When you turn off the computer, leave it next to the robot box.
  4. Turn off all programs on your computer
  5. Exit FLLCasts  
  6. Shut down your computer
  7. Put your chair under the desk.