7-Segment Display to Arduino Uno in Tinkercad (With Traffic Light Counter)

MakeMindz

Module 02 of 10

Beginner+ ⏱ ~50 min 🔴 Traffic Light 🖥 Tinkercad

Traffic Light System
with 7-Segment Countdown

Combine three LEDs and a 7-segment display to build a real traffic light that counts down 5–0 for each phase — exactly like the signals on the road.

▶ Open Simulator 📖 Step-by-Step

1Overview 2Phases 3Components 4Simulator 5Circuit 67-Segment 7Truth Table 8Code 9Tinkercad 10Quiz 11Applications

Section 01

What Will You Build?

This project combines a 7-segment display (showing digits 0–5) with a three-LED traffic light. Instead of a plain delay(5000), the display counts down from 5 to 0 during each phase — exactly how real smart traffic signals work!

🏁 What you'll learn:

💡Control multiple LEDs with digital output pins

🔢Drive a 7-segment display for a countdown

🔄Sequence events with loops and timing

🎛Use a 2D array to store segment patterns

Section 02

Traffic Light Phases

The traffic light cycles through three phases. During each, the 7-segment display counts down from 5 to 0, giving drivers and pedestrians a visual timer.

🔴 RED — Stop

Red LED ON. All traffic must stop. Display counts 5→0.

5s

🟡 YELLOW — Caution

Yellow LED ON. Traffic prepares to move. Display counts 5→0.

5s

🟢 GREEN — Go

Green LED ON. Traffic moves. Display counts 5→0.

5s

Section 03

Components Required

#	Component	Qty	Role
1	Arduino UNO	×1	Controls all LEDs and the 7-segment display
2	Red LED	×1	Stop signal
3	Yellow LED	×1	Caution signal
4	Green LED	×1	Go signal
5	Common Cathode 7-Segment Display	×1	Countdown timer (5→0) for each phase
6	220Ω Resistors	×10	7 for segments + 3 for LEDs
7	Breadboard	×1	Clean prototyping surface
8	Jumper Wires	~20	All connections

Section 04

Interactive Preview

Watch the traffic light and countdown work together. Press Play to start the simulation.

Live Traffic Light + 7-Segment Countdown

SIGNAL

● READY

Press Play to start

5

seconds

COUNTDOWN

Section 05

Circuit Connections

The full circuit combines three LED connections and seven 7-segment pins. Follow the wiring guide below.

🔴🟡🟢 Traffic Light LEDs (via 220Ω resistors)

Red LED +→Digital Pin 2 on Arduino

Yellow LED +→Digital Pin 3 on Arduino

Green LED +→Digital Pin 4 on Arduino

All LED (–)→GND on Arduino (via 220Ω resistors)

🔢 7-Segment Segments (via 220Ω resistors)

a

↓ 220Ω

Pin 7

b

↓ 220Ω

Pin 8

c

↓ 220Ω

Pin 9

d

↓ 220Ω

Pin 10

e

↓ 220Ω

Pin 11

f

↓ 220Ω

Pin 12

g

↓ 220Ω

Pin 13

COM (both)→GND on Arduino

Section 06

7-Segment Display Explorer

This project only uses digits 0–5 for the countdown. Click each to see the exact segment pattern light up.

Click a digit — Common Cathode Display

Digit-by-Digit Pin States

Section 07

Segment Truth Table (Digits 0–5)

1 = HIGH (ON)  ·  0 = LOW (OFF)  ·  Only digits 0–5 are needed for the countdown timer.

Digit	a (7)	b (8)	c (9)	d (10)	e (11)	f (12)	g (13)

Section 08

The Arduino Code

Two tabs below: the full traffic light + countdown code, and the standalone showDigit() function you can study separately.

traffic_light_7seg.ino

// ── Traffic Light + 7-Segment Countdown ──────

// Traffic Light LED Pins
int redLED    = 2;
int yellowLED = 3;
int greenLED  = 4;

// 7-Segment Pins (a–g)
int a=7, b=8, c=9, d=10, e=11, f=12, g=13;

void setup() {
  pinMode(redLED,    OUTPUT);
  pinMode(yellowLED, OUTPUT);
  pinMode(greenLED,  OUTPUT);
  pinMode(a,OUTPUT); pinMode(b,OUTPUT); pinMode(c,OUTPUT);
  pinMode(d,OUTPUT); pinMode(e,OUTPUT); pinMode(f,OUTPUT);
  pinMode(g,OUTPUT);
}

// Display a digit (0–5) on the 7-segment display
void showDigit(int num) {
  int seg[6][7] = {
    {1,1,1,1,1,1,0},  // 0: a,b,c,d,e,f ON
    {0,1,1,0,0,0,0},  // 1: b,c ON
    {1,1,0,1,1,0,1},  // 2: a,b,d,e,g ON
    {1,1,1,1,0,0,1},  // 3: a,b,c,d,g ON
    {0,1,1,0,0,1,1},  // 4: b,c,f,g ON
    {1,0,1,1,0,1,1}   // 5: a,c,d,f,g ON
  };
  digitalWrite(a, seg[num][0]);
  digitalWrite(b, seg[num][1]);
  digitalWrite(c, seg[num][2]);
  digitalWrite(d, seg[num][3]);
  digitalWrite(e, seg[num][4]);
  digitalWrite(f, seg[num][5]);
  digitalWrite(g, seg[num][6]);
}

// Countdown 5→0, one second per digit
void countdown() {
  for (int i = 5; i >= 0; i--) {
    showDigit(i);
    delay(1000);
  }
}

void loop() {
  // ── RED PHASE ──────────────────────────────
  digitalWrite(redLED,    HIGH);
  digitalWrite(yellowLED, LOW);
  digitalWrite(greenLED,  LOW);
  countdown();

  // ── YELLOW PHASE ───────────────────────────
  digitalWrite(redLED,    LOW);
  digitalWrite(yellowLED, HIGH);
  digitalWrite(greenLED,  LOW);
  countdown();

  // ── GREEN PHASE ────────────────────────────
  digitalWrite(redLED,    LOW);
  digitalWrite(yellowLED, LOW);
  digitalWrite(greenLED,  HIGH);
  countdown();
}

showDigit() — standalone

// Standalone showDigit() — drop into any project
int a=7, b=8, c=9, d=10, e=11, f=12, g=13;

void showDigit(int num) {
  int seg[6][7] = {
    {1,1,1,1,1,1,0},
    {0,1,1,0,0,0,0},
    {1,1,0,1,1,0,1},
    {1,1,1,1,0,0,1},
    {0,1,1,0,0,1,1},
    {1,0,1,1,0,1,1}
  };
  digitalWrite(a,seg[num][0]); digitalWrite(b,seg[num][1]);
  digitalWrite(c,seg[num][2]); digitalWrite(d,seg[num][3]);
  digitalWrite(e,seg[num][4]); digitalWrite(f,seg[num][5]);
  digitalWrite(g,seg[num][6]);
}

// Usage: showDigit(3); → displays "3" on the display

💡 Key code concepts in this project:

• 2D array — seg[6][7] stores all 6 segment patterns in one compact structure
• Function reuse — countdown() is called once per phase instead of repeating 18 lines
• for loop — counts from 5 down to 0, displaying each digit and waiting 1 second

Section 09

Try It in Tinkercad

The complete circuit with traffic light LEDs and 7-segment countdown is pre-wired. Hit Start Simulation to watch the full cycle run.

Open Traffic Light Simulation

All LEDs and 7-segment display are connected. Start the simulation and watch the full RED→YELLOW→GREEN cycle with live countdown.

▶ Launch Simulator ↗

🧪 Simulator challenges:

1. Run the simulation — observe the full RED→YELLOW→GREEN cycle with countdown.
2. Change the for loop to count from 9→0 for a 9-second phase.
3. Make the yellow phase shorter (count from 2→0 instead of 5→0).
4. Challenge: Add a buzzer that beeps once per second during the red phase only.
5. Bonus: Add a second set of traffic lights for cross-traffic!

Section 10

Test Your Knowledge

Click an option to check your answer instantly.

Q1. What does the countdown() function do in this project?

Changes the LED colour

Displays 5→0 on the 7-segment display, one per second

Reads sensor values from A0

Q2. Why is countdown() called as a function rather than repeating the code 3 times?

To make the code run faster

To avoid repeating the same code 3 times (reusability)

Because the 7-segment display requires functions

Q3. How many total digital pins does this project use on the Arduino?

3 pins

7 pins

10 pins (3 LEDs + 7 segments)

Q4. What is stored in the seg[6][7] 2D array?

The Arduino pin numbers for each segment

The HIGH/LOW pattern for each segment of digits 0–5

The colour of each traffic light phase

Section 11

Real-World Applications

🚦Smart JunctionsCountdown timers on real traffic signals

🏗School CrossingsSafe pedestrian crossing systems

🚜Factory FloorsMachine status signals with timers

🎯Game Show TimersVisual countdown for competitions

🚫Access ControlDoor wait timer with signal

🔬Science FairEye-catching exhibition project

🚀 Ready to level up? Try these extensions:

• Add a buzzer that beeps every second during the countdown
• Use a push button to let pedestrians manually trigger the green phase
• Add a second 7-segment display for two-digit countdown (00–59)
• Use a PIR motion sensor to extend green when vehicles are detected
• Add an LCD screen showing STOP / CAUTION / GO text alongside the lights

🚦

MakeMindz — Traffic Light System with 7-Segment Countdown
Part of the makemindz.com Arduino project series  ·  Open Tinkercad Simulation ↗