In this project, learners explore how technology improves road safety by using the Calliope Mini to understand how traffic lights work. They will program red, yellow, and green LEDs to turn ON in the correct order and timing, just like real traffic signals. We have included extra challenges that allow learners to experiment with different light sequences and timing patterns, making learning fun and interactive. Through this hands-on experience, learners develop logical thinking, problem-solving skills, and confidence while learning how coding, robotics, and smart systems help keep people safe and cities organized.

Traffic Light Connections

1. Connect the Red LED's long leg (+) of the LED to one end of the 220Ω resistor.

2. Connect the other end of the resistor to Pin 0 on the Calliope Mini

3. Connect the Red LED's short leg (–) of the LED to GND on the Calliope Mini

1. Connect the Yellow LED's long leg (+) of the LED to one end of the 220Ω resistor.
2. Connect the other end of the resistor to Pin 1 on the Calliope Mini
3. Connect the Yellow LED's short leg (–) of the LED to GND on the Calliope Mini

1. Connect the Green LED's long leg (+) of the LED to one end of the 220Ω resistor.
2. Connect the other end of the resistor to Pin 2 on the Calliope Mini
3. Connect the Green LED's short leg (–) of the LED to GND on the Calliope Mini

Tip: Always use a resistor between the LED and Calliope pin to prevent burning out your LED!

Follow these steps carefully to open and explore the project in MakeCode for Calliope Mini:

• Click this link to open the project code in MakeCode

• When you open the link, you will see a few colorful blocks that makes the project.

• Next, click Edit Code tab to be directed to the MakeCode editor

Plug in your Calliope Mini to your computer using a USB cable, then follow the steps in the video to upload your code and bring your project to life!

• LED not lighting?
  Make sure the LED polarity is correct—long leg = positive, short leg = GND.

• Wrong color lighting?
  Check that each LED is connected to the correct pin (P0, P1, P2).

• LEDs flicker or stay dim?
  Ensure resistors are between 100–220Ω.

• Program not running?
  Confirm the code was downloaded to the Calliope Mini successfully

• How digital pins control outputs

• How traffic lights are programmed in the real world

• How to create sequences with timing

• How loops work in microcontrollers

• Practical robotics and coding skills that connect to real city infrastructure

• Add a pedestrian button using Pin P3 to trigger a “Walk/Don’t Walk” signal.

• Make the traffic light blink yellow at night mode.

• Add a sound buzzer for pedestrian beeps—just like real crossings.

• Create a four-way intersection using more LEDs and smarter timing.

• Build a cardboard mini city and place your traffic lights along “roads.”

Use Edge Impulse to build, train, and deploy machine learning (ML) models to make their traffic light system intelligent and helpful. The AI learns from traffic patterns, such as how often cars and pedestrians arrive.

For example:

• Traffic Flow Predictor: The Calliope checks how often cars  “arrive” at the intersection (add a button to your project to simulate a car approaching when pressed). After a few tries, it predicts when the next car will come and changes the lights automatically.

• Fun Game Mode: Students can press buttons randomly to test the AI, and the Calliope tries to match or adjust the light sequence, creating a fun interactive game.

• Adaptive Timing: The AI can speed up or slow down the green light depending on how many cars are “waiting,” teaching kids about smart decision-making