3.1.2 Traffic Light

Introduction

In this beginner-friendly project, you’ll build your own working traffic light system using red, yellow, and green LEDs! Just like real traffic lights, your system will automatically cycle through different colors with proper timing. Plus, we’ll add a 4-digit display that shows a countdown timer for each light phase - so drivers know exactly how much time is left!

Components

Connect

T-Board Name	physical	wiringPi	BCM
GPIO17	Pin 11	0	17
GPIO27	Pin 13	2	27
GPIO22	Pin 15	3	22
SPIMOSI	Pin 19	12	10
GPIO18	Pin 12	1	18
GPIO23	Pin 16	4	23
GPIO24	Pin 18	5	24
GPIO25	Pin 22	6	25
SPICE0	Pin 24	10	8
SPICE1	Pin 26	11	7

Warning

Important SPI Configuration Notice: If you have previously enabled SPI on your Raspberry Pi, you must disable it before running this traffic light project. This is because two of our LEDs are connected to SPI-related pins, and having SPI enabled will prevent them from working properly.

To disable SPI: Run sudo raspi-config → Interface Options → SPI → No

Code

For C Language User

Go to the code folder compile and run.

cd ~/super-starter-kit-for-raspberry-pi/c/3.1.2/

gcc 3.1.2_TrafficLight.c -lwiringPi

sudo ./a.out

How your traffic light works:

Once the program starts, your traffic light will cycle through the standard sequence:

🔴 Red Light: 60 seconds (Stop! Wait for green)
🟢 Green Light: 30 seconds (Go! Safe to proceed)
🟡 Yellow Light: 5 seconds (Caution! Prepare to stop)
Back to Red: The cycle repeats automatically forever

The 4-digit display will count down the remaining time for each phase, so you can see exactly when the light will change!

Tip

Want to explore the code? Use nano 3.1.2_TrafficLight.c or nano 3.1.2_TrafficLight.py to see how the timing and LED control work!

For Python Language User

Go to the code folder and run.

cd ~/super-starter-kit-for-raspberry-pi/python

python 3.1.2_TrafficLight.py