[RL73] Grade 7 - Session 3

M3D RoboticsLab RoboticsLab Grade 7
1

Session 3: Endless Moves: Loop Logic

Duration: 50-60 minutes

Equipment Required:

  • M3D Robotics kit (M3D Go)
  • Laptops with Arduino IDE
  • USB/OTG cables to connect the robot to the laptop
  • Projector for live coding demonstrations

Learning Objectives:

  • Understand variables as containers for storing data values.
  • Explore basic types of variables and how to use them in code.
  • Learn for loops for repeating actions a specified number of times.
  • Apply loops with movement, display messages, and sensor readings to control the robot’s behavior.

1. Introduction to Variables (15 minutes)

Activity:
Start with a hands-on activity to introduce the concept of variables as a way to store and manipulate data in code. This sets up a foundation for using variables with loops.

Instructions:

  1. Visualizing Variables:

Begin with an empty container or cup, explaining that variables are like containers where we store values temporarily. You can start as follows:

"Think of this container as a variable. Right now, it’s empty, but we can add coins to it, just like putting points into a game score. When we need the value, we can pull it out or change it.”

  • Write “Coins:” on the board and hand out coins to students.
  • Encourage them to add the coins in the cup and change the value of the variable “Coins” as they add coins in it.
  1. Demonstrate Variable Usage:

Write code to create and assign a simple variable on the projector.

  • Example Code:
    int score = 0;  // Creates a variable named 'score' and sets it to 0

Explain that int means it’s a whole number. You may say:

“Here, ‘score’ is a variable that starts at zero. As we play, we can increase this score. Just like you count points in a game, we count values with variables.”

  1. Types of Variables:
    Introduce a few basic variable types with examples:
    • int (integer): Stores whole numbers, like scores or counts.
    • float (floating-point): Stores numbers with decimals, like distances or measurements.
    • String: Stores text, like messages to display on the screen.
    • bool: Stores the status true or false of a state to be used in conditions.
    • Example Code:
      int count = 5;           // Stores a whole number
float distance = 15.6;    // Stores a number with decimals
String greetings = "Hello"; // Stores text

You can explain each variable as you code them on the projector screen:

“Just like you can put different items in a container, you can store different kinds of data in variables. int is for whole numbers, float for decimals, and String for text.”

2. Introduction to Loops (10 minutes)

Activity:
Begin with a discussion on the need for repeating actions in code, introducing for loop.

Discussion Examples:

You may say:

“Have you ever clapped ten times in a row or counted steps? Instead of writing the same instruction multiple times, we can say ‘Clap ten times,’ and everyone knows what to do. A for loop helps us repeat actions like this.”

Introduce for loops and demonstrate a basic example on the projector.

You main explain the syntax by breaking it down in three parts:

  • Variable initialization/Defining the variable
  • Condition
  • Variable change
for(i = 0, i<10, i++){

display.text("Clap!");    // Instructions to be repeated

}

Example Code for For Loop:

#include <M3DGo.h>

void setup() {
    go.begin();  // Initialize the robot
}

void loop() {
    for (int i = 0; i < 3; i++) {    // Repeat actions 3 times
        go.forward(50);              // Move forward at 50% speed
        go.delay(1000);               // Move for 1 second
        go.stop();                    // Stop
        go.delay(500);                // Wait for 0.5 seconds
    }
}

Explanation:

You may say:

“This for loop repeats three times. Each time, the robot moves forward, shows ‘Step’ and the step number, waits, then stops. The i variable keeps count.”

Encourage students to change the loop count and observe the changes.

3. Hands-On Challenges (30 minutes)

Encourage students to apply for loop, using movement, display messages, and distance readings.

Challenge 1: Forward and Spin Repeat

  • Task: Program the robot to move forward and spin clockwise, repeating five times using a for loop.

Example Code:

void setup() {
    go.begin();
}

void loop() {
    for (int i = 0; i < 5; i++) {
        go.forward(50);
        display.text("Forward Step " + String(i+1));
        go.delay(1000);
        go.spinClockwise(50);
        display.text("Spinning");
        go.delay(500);
        go.stop();
    }
}

Challenge 2: Loop Counter on Display

  • Task: Use a for loop to make the robot move forward 3 times and display the loop count each time.

Example Code:

void setup() {
    go.begin();
}

void loop() {
    for (int i = 1; i <= 3; i++) {
        go.forward(50);
        display.text("Loop " + String(i));   // Display loop count
        go.delay(1000);
        go.stop();
        go.delay(500);
    }
}

Challenge: Obstacle Response with State Variable

Task:
Program the robot to detect obstacles within 15 cm using the distance sensor. When it detects an obstacle, set a boolean variable (obstacleDetected) to true. If obstacleDetected is true, the robot should stop, display “Obstacle Ahead!” on its screen, and spin in place for 2 seconds. Once the spin is complete, reset obstacleDetected to false, allowing the robot to resume moving forward if the path is clear.

Goal:
Learn to use a boolean variable to create a state that triggers specific actions based on sensor input.

Example Code:

#include <M3DGo.h>

void setup() {
    go.begin();
}

void loop() {

bool obstacleDetected = false;  // Variable to track obstacle status

    // Check if obstacle is detected within 15 cm
    if (range.get_cm() < 15) {
        obstacleDetected = true;   // Set state to true if obstacle is close
    }

    // Perform actions based on obstacle state
    if (obstacleDetected) {
        go.stop();                    // Stop the robot
        display.text("Obstacle Ahead!"); // Display message
        go.spinClockwise(50);          // Spin in place
        go.delay(2000);                // Spin for 2 seconds
        obstacleDetected = false;      // Reset state after action
    } else {
        go.forward(50);  // Continue moving if no obstacle
    }
}

4. Reflection and Wrap-Up (5 minutes)

Reflection Questions:

You may ask:

  • “How did using a for loop help you repeat actions a specific number of times?”
  • “What did you find challenging or interesting about today’s session?”

Teacher’s Role:
Wrap up with a discussion, reinforcing the value of variables and loops for creating efficient, flexible code that can adapt to repeated actions and specific conditions.

Learning Outcome:

By the end of this session, students will understand basic variables, for loop, and use these structures in conjunction with sensor inputs and display messages to build decision-based behaviors in the robot.