Creating a 7-Segment 4-Digit Real-Time Clock with Arduino Objective

 Instructions for those learning to set up to create a clock in a 7-segment display for an arduino

Components Needed:

1. Arduino (e.g., Uno, Nano)
2. 7-segment 4-digit display (common anode or common cathode)
3. DS3231 RTC (Real-Time Clock) module
4. 4 Push buttons (for setting hours, minutes, etc.)
5. Resistors (for buttons)
6. Breadboard and jumper wires

Circuit Diagram:

1. Connect the DS3231 RTC Module to the Arduino:

   • VCC to Arduino 5V
   • GND to Arduino GND
   • SDA to A4 (for Uno, Nano)
   • SCL to A5 (for Uno, Nano)

2. Connect the 7-Segment Display:

   • Remember the following details:
   • Each segment (a-g) and the decimal point (dp) need to be connected to digital pins on the Arduino using current-limiting resistors (usually 220Ω or 330Ω).
   • The common pins (COM) of the 4-digit display should be connected to digital pins on the Arduino to multiplex the display.

3. Connect the Buttons:

   • Each button will be connected between a digital pin on the Arduino and GND.
   • Use pull-up resistors (10kΩ) or the internal pull-up resistors in the Arduino code.

Example Circuit Connections (assuming common cathode display):

• Segments a-g: Digital pins 2-8
• Common pins for digits 1-4: Digital pins 9-12
• Buttons: Digital pins 13, A0, A1, A2

Arduino Code:

Here’s an example code to display the time from the DS3231 on the 7-segment display and to change the time using buttons.

cpp
#include <Wire.h>
#include <RTClib.h>

// Define pins for 7-segment display
const int segmentPins[] = {2, 3, 4, 5, 6, 7, 8};
const int digitPins[] = {9, 10, 11, 12};

// Define pins for buttons
const int buttonHour = 13;
const int buttonMinute = A0;
const int buttonSet = A1;
const int buttonMode = A2;

RTC_DS3231 rtc;
DateTime now;
int hour, minute;
bool setTimeMode = false;

void setup() {
  Wire.begin();
  rtc.begin();

  // Set up segment pins as outputs
  for (int i = 0; i < 7; i++) {
    pinMode(segmentPins[i], OUTPUT);
  }
  
  // Set up digit pins as outputs
  for (int i = 0; i < 4; i++) {
    pinMode(digitPins[i], OUTPUT);
  }

  // Set up button pins as inputs
  pinMode(buttonHour, INPUT_PULLUP);
  pinMode(buttonMinute, INPUT_PULLUP);
  pinMode(buttonSet, INPUT_PULLUP);
  pinMode(buttonMode, INPUT_PULLUP);

  // Get the current time from RTC
  now = rtc.now();
  hour = now.hour();
  minute = now.minute();
}

void loop() {
  now = rtc.now();

  if (setTimeMode) {
    if (digitalRead(buttonHour) == LOW) {
      hour = (hour + 1) % 24;
      delay(200);
    }
    if (digitalRead(buttonMinute) == LOW) {
      minute = (minute + 1) % 60;
      delay(200);
    }
    if (digitalRead(buttonSet) == LOW) {
      rtc.adjust(DateTime(now.year(), now.month(), now.day(), hour, minute, 0));
      setTimeMode = false;
      delay(200);
    }
  } else {
    hour = now.hour();
    minute = now.minute();
    if (digitalRead(buttonMode) == LOW) {
      setTimeMode = true;
      delay(200);
    }
  }

  displayTime(hour, minute);
}

void displayTime(int h, int m) {
  int digits[] = {h / 10, h % 10, m / 10, m % 10};
  
  for (int i = 0; i < 4; i++) {
    digitalWrite(digitPins[i], LOW);
    displayDigit(digits[i]);
    delay(5);
    digitalWrite(digitPins[i], HIGH);
  }
}

void displayDigit(int num) {
  const int numToSegments[] = {
    // a  b  c  d  e  f  g
    0b00111111, // 0
    0b00000110, // 1
    0b01011011, // 2
    0b01001111, // 3
    0b01100110, // 4
    0b01101101, // 5
    0b01111101, // 6
    0b00000111, // 7
    0b01111111, // 8
    0b01101111  // 9
  };
  
  for (int i = 0; i < 7; i++) {
    digitalWrite(segmentPins[i], (numToSegments[num] >> i) & 0x01);
  }
}

Explanation:

1. Initialization:

   • Initializes the RTC module.
   • Sets up pins for the 7-segment display and buttons.

2. Main Loop:

   • Reads the current time from the RTC module.
   • Checks if the set time mode is enabled.
   • Increments hours or minutes when corresponding buttons are pressed.
   • Updates the RTC with the new time when the set button is pressed.
   • Displays the current time on the 7-segment display.

3. displayTime Function:

   • Splits the hour and minute into individual digits.
   • Displays each digit on the 7-segment display.

4. displayDigit Function:

   • Converts the digit to the corresponding segments.
   • Lights up the segments accordingly.

Notes:

• The delay between digit displays ensures proper multiplexing.
• Adjust pin assignments if needed based on your specific hardware setup.

This setup provides a functional real-time clock with the ability to set the time using buttons.