Traffic light module

By Admin, 07/07/2026 · 4 min read

Traffic light module guide for the 37-in-1 Arduino Sensors Kit.

Sensor module

Traffic light module

Module 03 in the 37-in-1 kit. Shows red, yellow, and green states. Start by changing one physical condition and watching the reading respond.

Back to 37-in-1 kit Open sensor projects Open source guide

Source image

Match the physical module

Use this source photo to identify the module before wiring it. The photo is saved from the checked 37-in-1 kit guide.

What it detects

Shows red, yellow, and green states.

This is the main signal to test before adding displays, motors, buzzers, or game logic.

How it works

The module is three separate LEDs arranged like a traffic signal. Code turns each output on in sequence, which makes it a simple way to learn state changes and timed behaviour.

What you need

Starter parts

Keep the first circuit small and add displays or motors later.

White USB Type-C CableConnects or powers USB-C devices, boards, chargers, and project accessories.

Arduino Nano & Expansion BoardCompact controller and breakout board for sensors, wiring, and embedded projects.

Female to Male 10 cm Wire10 cm Jumper Wire for connecting breadboards to male-pin modules or sensors.

37-in-1 Arduino Sensors KitExplore light, sound, motion, touch, and environmental sensing with Arduino projects.

Try first

Run a timed traffic-light sequence.

This is the quickest way to see the module reading change.

Connections

Wiring to the Arduino Nano on its expansion shield

Plug into the digital bank of headers. The pin numbers below match the sketch further down this page; change one and change the other.

Module pinGoes to

Module RShield header D8

Module YShield header D9

Module GShield header D10

Where it plugs in

The ringed column on the shield is the one this module uses. Its three pins are ground on top, 5 V in the middle and the signal at the bottom, so a three-pin module takes one whole column.

Before you power it

On this shield both banks read G, V, S from the top: the black lead goes to G, the red to V and the signal to S. The letters are printed at the ends of the rows, so check them on your own board before you wire a whole class.

One 3-pin lead per module. Connect ground first, then power, then signal.

A module in backwards puts 5 V on the signal pin. Some shrug it off, plenty do not.

The pin map and the shield layout are on the Nano and expansion shield wiring guide.

1

Plug the module into the header listed above, black lead to ground.

2

Copy the sketch below, upload it, and open Tools > Serial Monitor at 9600 baud.

3

Change the physical condition the module senses and watch the reading or output respond.

Starter sketch

Code you can copy and upload

Set the pin constants at the top of the sketch to match the header you plugged the module into, then upload it and open Tools > Serial Monitor at 9600 baud.

traffic_light_module.inoArduino C++

1const uint8_t RED = 8, YELLOW = 9, GREEN = 10;
2
3void setup() {
4  pinMode(RED, OUTPUT);  pinMode(YELLOW, OUTPUT);  pinMode(GREEN, OUTPUT);
5}
6
7void only(uint8_t pin, uint16_t ms) {
8  digitalWrite(RED, pin == RED);
9  digitalWrite(YELLOW, pin == YELLOW);
10  digitalWrite(GREEN, pin == GREEN);
11  delay(ms);
12}
13
14void loop() {
15  only(GREEN, 4000);
16  only(YELLOW, 1200);
17  only(RED, 4000);
18}

Three separate LEDs, so this is really a state machine with a timer. Each state names the one pin that should be on.

Build next

Build a crossing-light game with a push button.

Turn the raw reading into a small useful interaction.

Add the OLED display when the reading is stable.

Use an LED, buzzer, servo, or motor only after the sensor input works by itself.

Write down the value range you see so your thresholds match the real room and module.

Reference

Source guide and step-by-step builds

Use the source guide for the exact wiring diagram, and the workshop guides for a full worked build on this board.

Keyestudio project 3: Traffic light module
Arduino Nano and DHT11 electronics workshop
Arduino Nano and I/O expansion shield wiring
Install Arduino IDE on Windows or Mac
37-in-1 kit index

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Traffic light module