Introduction
In this project, we will build a 4-Digit 7-Segment Digital Clock using Arduino Uno in the Wokwi simulator. This Arduino digital clock displays time in HH:MM format using a multiplexed 7-segment display.
This is a perfect beginner-to-intermediate level project to understand:
-
Multiplexing technique
-
7-segment display interfacing
-
Real-time clock logic
-
Arduino timing functions
Diagram.json:
{
"version": 1,
"author": "4-Digit Clock Display",
"editor": "wokwi",
"parts": [
{
"type": "wokwi-arduino-uno",
"id": "uno",
"top": 0,
"left": 0,
"attrs": {}
},
{
"type": "wokwi-tm1637-7segment",
"id": "tm1637",
"top": -96,
"left": 144,
"attrs": {
"color": "red"
}
},
{
"type": "wokwi-pushbutton",
"id": "btn_set",
"top": 124.8,
"left": -124.8,
"attrs": {
"color": "green",
"label": "SET"
}
},
{
"type": "wokwi-pushbutton",
"id": "btn_hour",
"top": 124.8,
"left": -28.8,
"attrs": {
"color": "blue",
"label": "HOUR"
}
},
{
"type": "wokwi-pushbutton",
"id": "btn_min",
"top": 124.8,
"left": 67.2,
"attrs": {
"color": "yellow",
"label": "MIN"
}
},
{
"type": "wokwi-resistor",
"id": "r1",
"top": 220.15,
"left": -124.8,
"rotate": 90,
"attrs": {
"value": "10000"
}
},
{
"type": "wokwi-resistor",
"id": "r2",
"top": 220.15,
"left": -28.8,
"rotate": 90,
"attrs": {
"value": "10000"
}
},
{
"type": "wokwi-resistor",
"id": "r3",
"top": 220.15,
"left": 67.2,
"rotate": 90,
"attrs": {
"value": "10000"
}
}
],
"connections": [
[
"tm1637:CLK",
"uno:2",
"blue",
[
"v0"
]
],
[
"tm1637:DIO",
"uno:3",
"green",
[
"v0"
]
],
[
"tm1637:VCC",
"uno:5V",
"red",
[
"v0"
]
],
[
"tm1637:GND",
"uno:GND.1",
"black",
[
"v0"
]
],
[
"btn_set:1.l",
"uno:6",
"green",
[
"v0"
]
],
[
"btn_set:2.l",
"r1:1",
"black",
[
"v0"
]
],
[
"r1:2",
"uno:GND.2",
"black",
[
"v0"
]
],
[
"btn_hour:1.l",
"uno:4",
"blue",
[
"v0"
]
],
[
"btn_hour:2.l",
"r2:1",
"black",
[
"v0"
]
],
[
"r2:2",
"uno:GND.2",
"black",
[
"v0"
]
],
[
"btn_min:1.l",
"uno:5",
"yellow",
[
"v0"
]
],
[
"btn_min:2.l",
"r3:1",
"black",
[
"v0"
]
],
[
"r3:2",
"uno:GND.2",
"black",
[
"v0"
]
]
],
"dependencies": {}
}
You can simulate everything online in Wokwi without physical hardware.
Code:
/*
* 4-Digit 7-Segment Clock Display
* Displays time in HH:MM format using TM1637 display module
* Features: Clock display, adjustable time, blinking colon
*/
#include <TM1637Display.h>
// Pin definitions for TM1637
#define CLK_PIN 2 // Clock pin
#define DIO_PIN 3 // Data pin
// Button pins for setting time
#define HOUR_BTN 4 // Button to increment hours
#define MIN_BTN 5 // Button to increment minutes
#define SET_BTN 6 // Button to enter/exit set mode
// Create display object
TM1637Display display(CLK_PIN, DIO_PIN);
// Time variables
int hours = 12;
int minutes = 0;
int seconds = 0;
// State variables
bool setMode = false; // Time setting mode flag
bool colonBlink = true; // Colon blinking state
unsigned long lastUpdate = 0; // Last time update timestamp
unsigned long lastBlink = 0; // Last colon blink timestamp
// Button debouncing
unsigned long lastHourPress = 0;
unsigned long lastMinPress = 0;
unsigned long lastSetPress = 0;
const int debounceDelay = 200;
// Segment data for digits with colon
const uint8_t SEG_COLON = 0b01000000; // Colon segment
void setup() {
Serial.begin(9600);
// Initialize button pins
pinMode(HOUR_BTN, INPUT_PULLUP);
pinMode(MIN_BTN, INPUT_PULLUP);
pinMode(SET_BTN, INPUT_PULLUP);
// Initialize display
display.setBrightness(0x0f); // Maximum brightness
// Display startup message
uint8_t data[] = {0x00, 0x00, 0x00, 0x00};
display.setSegments(data);
delay(500);
Serial.println("4-Digit 7-Segment Clock Initialized");
Serial.println("Use buttons to set time:");
Serial.println("- SET button: Enter/Exit set mode");
Serial.println("- HOUR button: Increment hours");
Serial.println("- MIN button: Increment minutes");
}
void loop() {
unsigned long currentMillis = millis();
// Check button presses
checkButtons();
// Update seconds and time (only when not in set mode)
if (!setMode && currentMillis - lastUpdate >= 1000) {
lastUpdate = currentMillis;
updateTime();
}
// Blink colon every 500ms
if (currentMillis - lastBlink >= 500) {
lastBlink = currentMillis;
colonBlink = !colonBlink;
}
// Display time
displayTime();
delay(10); // Small delay for stability
}
void updateTime() {
seconds++;
if (seconds >= 60) {
seconds = 0;
minutes++;
if (minutes >= 60) {
minutes = 0;
hours++;
if (hours >= 24) {
hours = 0;
}
}
}
// Print to Serial Monitor
Serial.print("Time: ");
if (hours < 10) Serial.print("0");
Serial.print(hours);
Serial.print(":");
if (minutes < 10) Serial.print("0");
Serial.print(minutes);
Serial.print(":");
if (seconds < 10) Serial.print("0");
Serial.println(seconds);
}
void displayTime() {
// Create time display value
int displayValue = hours * 100 + minutes;
// Show time with or without colon based on blink state
if (setMode) {
// In set mode, always show colon
display.showNumberDecEx(displayValue, 0b01000000, true);
} else {
// Normal mode, blink colon
if (colonBlink) {
display.showNumberDecEx(displayValue, 0b01000000, true);
} else {
display.showNumberDecEx(displayValue, 0b00000000, true);
}
}
}
void checkButtons() {
unsigned long currentMillis = millis();
// SET button - toggle set mode
if (digitalRead(SET_BTN) == LOW && currentMillis - lastSetPress > debounceDelay) {
lastSetPress = currentMillis;
setMode = !setMode;
if (setMode) {
Serial.println("*** SET MODE ENABLED ***");
Serial.println("Use HOUR and MIN buttons to adjust time");
} else {
Serial.println("*** SET MODE DISABLED ***");
Serial.println("Time saved. Clock running.");
seconds = 0; // Reset seconds when exiting set mode
lastUpdate = currentMillis; // Reset update timer
}
delay(200); // Additional debounce
}
// HOUR button - increment hours (only in set mode)
if (setMode && digitalRead(HOUR_BTN) == LOW && currentMillis - lastHourPress > debounceDelay) {
lastHourPress = currentMillis;
hours++;
if (hours >= 24) {
hours = 0;
}
Serial.print("Hours set to: ");
Serial.println(hours);
}
// MIN button - increment minutes (only in set mode)
if (setMode && digitalRead(MIN_BTN) == LOW && currentMillis - lastMinPress > debounceDelay) {
lastMinPress = currentMillis;
minutes++;
if (minutes >= 60) {
minutes = 0;
}
Serial.print("Minutes set to: ");
Serial.println(minutes);
}
}
Components Required (Wokwi Simulation)
-
Arduino Uno
-
4-Digit 7-Segment Display (Common Cathode)
-
220Ω Resistors (8)
-
Jumper Wires
Circuit Connections:
Segment Pins (a–g, dp)
Connect segment pins to Arduino digital pins:
| Segment | Arduino Pin |
|---|---|
| a | 2 |
| b | 3 |
| c | 4 |
| d | 5 |
| e | 6 |
| f | 7 |
| g | 8 |
Digit Control Pins
| Digit | Arduino Pin |
|---|---|
| D1 | 9 |
| D2 | 10 |
| D3 | 11 |
| D4 | 12 |
(Use resistors for segment pins)
How the Arduino Digital Clock Works
-
The code uses the millis() function to track time.
-
Every 60,000 milliseconds (1 minute), minutes increase.
-
When minutes reach 60, hours increase.
-
Multiplexing activates one digit at a time very quickly.
-
Human eyes see all digits glowing continuously.
Applications of 4-Digit 7-Segment Clock
-
Digital wall clock
-
School electronics project
-
Embedded systems learning
-
IoT display modules
-
Arduino beginner project
Why Use Wokwi Simulator?
-
No hardware required
-
Instant debugging
-
Easy circuit wiring
-
Perfect for students and beginners
FAQ
Q1: Can I add seconds to this Arduino clock?
Yes, you can modify the code to update every 1000 milliseconds and display seconds.
Q2: Can I use RTC module like DS3231?
Yes, for accurate real-time clock, you can connect an RTC module.
Q3: Is this project suitable for beginners?
Yes, this is an excellent intermediate beginner Arduino project.
Conclusion
This 4-Digit 7-Segment Clock using Arduino Uno in Wokwi is a great project to understand multiplexing and time control using millis(). It is ideal for school exhibitions, robotics students, and embedded systems beginners.
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