Materials Required
To build this stopwatch project, gather the following hardware components.
Some versions include an OLED display.
- Microcontroller: Arduino UNO, Nano, or Pro Mini (ATmega328P-based boards).
- Display: 0.96-inch I2C OLED Display (128×64 resolution, SSD1306 driver).
- Input: 2x Momentary Push Buttons (Tactile switches for Start/Stop and Reset).
- Breadboard: Standard half-size or full-size breadboard.
- Wiring: Jumper wires (Male-to-Male and Male-to-Female).
- Power: USB cable or external 5V power source for your Arduino.
Circuit Connections & Wiring Diagram
The 0.96-inch OLED display communicates via the I2C protocol, which uses only two data pins on the Arduino (SDA and SCL). The push buttons use digital input pins with internal pull-up resistors enabled in software, minimizing external wiring.
| Component | Component Pin | Arduino UNO/Nano Pin | Description |
| OLED Display | VCC | 5V | Power Supply |
| GND | GND | Ground | |
| SCL | A5 (or SCL) | I2C Clock Line | |
| SDA | A4 (or SDA) | I2C Data Line | |
| Start/Stop/Reset Button | Pin 1 | Digital Pin 6 | Control state (Start/Pause) |
| GND | Ground reference | ||
| Reset stopwatch to zero | |||
| Ground reference |
Step by Step Connection Diagram
Step 1
Step 2
Step 3
Step 4
Arduino Source Code
Before uploading the code, ensure you have installed the required libraries via the Arduino IDE Library Manager:
- Adafruit_SSD1306 (by Adafruit)
- Adafruit_GFX_Library (by Adafruit)
Arduino Code
// Ogbugbu Technologies https://ogbugbu-technologies.com.ng/ https://www.youtube.com/@ogbugbu-technologies
// Arduino OLED Stopwatch
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Fonts/FreeSans9pt7b.h>
#include <Fonts/FreeSans18pt7b.h>
#include <Fonts/FreeSans12pt7b.h>
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
// SCL A5
// SDA A4
#define OLED_RESET 0 // GPIO0
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
#define LOGO_HEIGHT 16
#define LOGO_WIDTH 16
const unsigned char PROGMEM icon [] = {
0x00, 0x1F, 0xF8, 0x00, 0x00, 0x1F, 0xF8, 0x00, 0x00, 0x1F, 0xF8, 0x00, 0x00, 0x1F, 0xF8, 0x00,
0x00, 0x1F, 0xF8, 0x00, 0x00, 0x03, 0xC0, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0xE0,
0x00, 0x1F, 0xF8, 0xF0, 0x00, 0x7F, 0xFE, 0x70, 0x00, 0xFF, 0xFF, 0x20, 0x01, 0xF0, 0x0F, 0x80,
0x03, 0xC1, 0x83, 0xC0, 0x03, 0x81, 0x81, 0xC0, 0x07, 0x01, 0x80, 0xE0, 0x07, 0x01, 0x80, 0xE0,
0x0E, 0x01, 0x80, 0x70, 0x0E, 0x01, 0x80, 0x70, 0x0E, 0x03, 0xC0, 0x70, 0x0E, 0x03, 0xC0, 0x70,
0x0E, 0x03, 0xC0, 0x70, 0x0E, 0x01, 0x80, 0x70, 0x0E, 0x00, 0x00, 0x70, 0x07, 0x00, 0x00, 0xE0,
0x07, 0x00, 0x00, 0xE0, 0x07, 0x80, 0x01, 0xE0, 0x03, 0xC0, 0x03, 0xC0, 0x01, 0xE0, 0x07, 0x80,
0x00, 0xF8, 0x1F, 0x00, 0x00, 0x7F, 0xFE, 0x00, 0x00, 0x1F, 0xF8, 0x00, 0x00, 0x07, 0xE0, 0x00
};
const unsigned char PROGMEM swatch [] = {
0x03, 0xC0, 0x03, 0xC0, 0x03, 0xC0, 0x00, 0x08, 0x07, 0xEC, 0x0E, 0x70, 0x18, 0x18, 0x30, 0x0C,
0x30, 0x8C, 0x21, 0x84, 0x21, 0x84, 0x30, 0x0C, 0x10, 0x08, 0x18, 0x18, 0x0F, 0xF0, 0x03, 0xC0
};
void setup() {
pinMode(6,INPUT_PULLUP); //Switch
display.begin(SSD1306_SWITCHCAPVCC, 0x3C); // initialize with the I2C addr 0x3C (for the 64x48)
display.display();
display.clearDisplay();
display.setFont(&FreeSans9pt7b);
display.drawPixel(10, 10, SSD1306_WHITE);
display.setTextColor(WHITE);
display.setCursor(0,0);
display.print("Viral Science");
display.display();
delay(800);
}
int poz=1;
int broj=1;
int kretanjeY=30;
int sec1=0;
int min1=0;
unsigned long msec=0;
unsigned long mili=0;
int pres=0;
int fase=0;
int start=0;
unsigned long tim=0;
void loop()
{
display.clearDisplay();
if(digitalRead(6)==0)
{
if(pres==0)
{
fase=fase+1;
pres=1;
if(fase>2)
fase=0;
}
}else{pres=0;}
if(fase==0)
{
display.setFont(&FreeSans12pt7b);
display.setFont();
display.setCursor(50,50);
display.print("Start");
display.drawBitmap(48, 8, icon, 32, 32, WHITE);
sec1=0;
min1=0;
tim=0;
mili=0;
msec=0;
start=0;
}
if(fase==1)
{
display.clearDisplay();
display.setFont(&FreeSans12pt7b);
display.setFont();
display.setCursor(37,0);
display.print("Stopwatch");
display.setFont(&FreeSans9pt7b);
if(start==0)
{
start=1;
tim=millis();
}
msec=(millis()-tim);
min1=msec/60000;
if((msec/1000)>59)
{
sec1=(msec/1000)-(min1*60);
}else{
sec1=msec/1000;
}
mili=(msec%1000)/10;
display.setCursor(42,30);
if(min1<=9)
{
display.print("0");
display.print(min1);
}else {display.print(min1);}
display.print(":");
if(sec1<=9)
{
display.print("0");
display.print(sec1);
}else {display.print(sec1);}
display.setFont(&FreeSans12pt7b);
display.setCursor(50,57);
if(mili<=9)
{
display.print("0");
display.print(mili);
}else {display.print(mili);}
}
if(fase==2)
{
display.clearDisplay();
display.setFont(&FreeSans12pt7b);
display.setFont();
display.setCursor(52,0);
display.print("Time:");
display.setFont(&FreeSans9pt7b);
display.setCursor(42,30);
if(min1<=9)
{
display.print("0");
display.print(min1);
}else {display.print(min1);}
display.print(":");
if(sec1<=9)
{
display.print("0");
display.print(sec1);
}else {display.print(sec1);}
display.setFont(&FreeSans12pt7b);
display.setCursor(50,57);
if(mili<=9)
{
display.print("0");
display.print(mili);
}else {display.print(mili);}
display.drawBitmap(105, 20, swatch, 16, 16, 1);
display.drawBitmap(12, 20, swatch, 16, 16, 1);
}
display.display();
}
