Robotics 1.0 Lesson Plan
Lesson 7 - Serve It Cool

Purpose: Enable students to connect a servo motor to the CPX and control its movement based on sensors such as light or temperature.

No. of Classes

2 classes (Duration: 1 hour 30 minutes; maximum 4 students per group).

Materials Required

    Desktop or laptop computer, CPX board, USB cable

    Micro Servo 9g

Curriculum Content 2.4 Exception handling
3.7 Slide switch
4.2 IR Tracking / Avoid Sensor
4.3 Servo Motor
7.1 Servo Motors
Prior Knowledge

Adafruit Circuit Playground Express (CPX) board

USB cable

Computer with Mu Editor

Exercises

Exercise:1


Servo Control Using CPX Toggle Switch


Click here to view the connection diagram for a servo motor and CPX
Click here to view the instructions and code

Exercise:2


Introduction to IR Sensor:


Click here to view the instructions for the connections
Click here to view the explanation and code

Exercise:3


Using Try-Except block in CircuitPython


Click here to view the instructions and code

Exercise:4


Handling Servo Motor Errors Using Try-Except in CircuitPython


Sample code:

Click here to view the instructions and code (without try-except)


How to fix the error:

Click here to view the instructions and code (with try-except)

Solution


Here is the solution:

  • Click here to see the solution video for Exercise 1
  • Click here to see the solution video for Exercise 3 (without try-except)
  • Click here to see the solution video for Exercise 3 (with try-except)
    • Teacher's Instruction
    1. Click here to know more about Servo working.Video
    2. Explain about servo motors and PWM (Pulse Width Modulation) - explanation and diagram
    3. Click here to know more about IR sensor working.Video
    4. Introduce the required materials (CPX, USB cable, Mu Editor, servo motor – 180°).
    5. Simple Explanation:
      • Introduce students to different types of servos - 90, 180 and continuous servo motors and highlight how they are different
      • Teach students that a 180 servo motor moves only between 0° and 180°.
      • Show how to control the servo using CircuitPython and the servo.angle command.
      • Explain that setting angles in a 180 server outside the range, like 360° will cause an error.
      • Use a try-except block to safely handle invalid angles.
      • Students run the code and observe servo movements and REPL (Read, Evaluate, Print, Loop) messages.
      • Provide step-by-step instructions and demonstrate troubleshooting techniques.
    6. View the code here
      What is the value of final_state in this? Talk about the motor_on=False statement inside the try-except block, why it is not reachable and different ways to ensure it executes
    7. Is it better to prevent errors or handle them when they happen?