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Arduino Visual Robot (2/4): buttons, LEDs, and modes

Students use visual blocks to read buttons, control LEDs, and build simple robot modes with observable real-hardware evidence.

  • Arduino robot (visual)
  • 55 min
  • Lower secondary / early high school
  • English
  • Robotics ยท Embedded systems
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Arduino robot (visual)
Arduino robot (visual)

Learning Outcomes

  • Use robot buttons as decision inputs.

  • Use LEDs and serial messages to communicate robot state.

  • Create a simple mode-based program with safe behaviour.

Student activity preview

Activity Content

Preview only. In a class session, students can fill in responses and submit their work to the teacher.

1

Design the modes

8 min

A robot can have states, not only movements. For example:

- Waiting mode: motors stopped, red LED on.
- Ready mode: motors stopped, blue LED on.
- Test mode: a very short movement, then stop.

Design three robot modes using buttons A, B, and C. For each mode, state which LED turns on, whether there is a serial message, and whether the robot moves or stays stopped.

2

Program inputs and outputs

24 min

  1. Open the robot visual lab and choose the recommended any-circuit option.

  2. Configure the buttons: Button A as buttonA, Button B as buttonB, Button C as buttonC.

  3. In the main loop, use if...then blocks.

  4. If buttonA is pressed, turn the red LED on and blue LED off.

  5. If buttonB is pressed, turn the blue LED on and red LED off.

  6. If buttonC is pressed, set both motors to 0, turn LEDs off, and print stopped.

  7. Verify, upload, and test each button from the robot interface.

Block image and text reference:

Block-style reference showing button setup for A, B, C and if-pressed logic for LEDs and safe stop

Configuration blocks:

[Button] A [as] buttonA
[Button] B [as] buttonB
[Button] C [as] buttonC

In the main loop:

if [buttonA is pressed]:
  [Set] red [led to] HIGH
  [Set] blue [led to] LOW

if [buttonB is pressed]:
  [Set] blue [led to] HIGH
  [Set] red [led to] LOW

if [buttonC is pressed]:
  [Change two motors speed]
    Left:  0
    Right: 0
  [Set] red [led to] LOW
  [Set] blue [led to] LOW
  [print] "stopped"

The Button ... as ... block creates the button name. After that, the is pressed blocks can use that name. Use is pressed (it checks whether the button is held at that moment); to make it register, hold the button while the program checks it in the loop.

Fill the table after testing the buttons. Use one row for each button you
test: A, B, and C. If the table shows extra blank rows, leave them empty. In
each row, record the intended mode, the LED you saw, any serial message, and
whether the result was safe.

Button Intended mode LED observed Serial message Safe result

Why do you need to configure a button before using a block that checks whether it is pressed?

3

Add a mode variable

15 min

As an improvement, add a variable called mode (*Variables* category). A
variable is a named "box" that stores a value and remembers it. Give it a starting
value (for example, mode = "waiting") so the robot has a state from the start. If
you do not set a starting value, the variable is empty until you press a button and
you will see no change. Each button changes the value:

- Press A: mode = "waiting".
- Press B: mode = "ready".
- Press C: mode = "stopped".

Then use mode to decide which LED or message to show.

Variable block image and text reference:

Block-style reference showing a mode variable, button updates, and LED decisions from the stored mode

At the start (run once):
  set mode to "waiting"

In the main loop:

if [buttonA is pressed]:
  set mode to "waiting"

if [buttonB is pressed]:
  set mode to "ready"

if [mode = "waiting"]:
  [Set] red [led to] HIGH
  [Set] blue [led to] LOW

if [mode = "ready"]:
  [Set] blue [led to] HIGH
  [Set] red [led to] LOW

What is the advantage of remembering the mode in a variable instead of only checking whether a button is pressed at this exact moment?

If pressing a button changes nothing, write three checks you would do before asking for help.

4

Short submission

8 min

Robot mode map

Submit your mode map and evidence of at least two working buttons. This can be a program screenshot, an observation table, or a written explanation with results.