How to display the time on an LCD using a real-time clock (RTC) module?

This project demonstrates how to use an Arduino to display the current time on an LCD screen. We’ll use the DS3231 RTC (Real-Time Clock) module, which keeps accurate time even when the Arduino is powered off. The time is displayed on a 16×2 I2C LCD display, which is easy to interface with the Arduino.

Components Required:

1. Arduino board (e.g., Arduino Uno)
2. LCD display (e.g., 16×2 LCD with I2C module)
3. RTC module (e.g., DS3231)
4. Jumper wires
5. Breadboard (Optional)

Here’s a step-by-step guide to achieve this, along with the Arduino code:

Wiring the Components:

• RTC Module (DS3231):
  • VCC to 5V
  • GND to GND
  • SDA to A4 (on Uno)
  • SCL to A5 (on Uno)
• LCD (16×2 with I2C):
  • VCC to 5V
  • GND to GND
  • SDA to A4 (on Uno)
  • SCL to A5 (on Uno)

Arduino Code:

#include <Wire.h>              // Include Wire library for I2C
#include <LiquidCrystal_I2C.h>  // Include LCD library for I2C
#include <RTClib.h>             // Include RTC library

RTC_DS3231 rtc;                 // Create RTC object
LiquidCrystal_I2C lcd(0x27, 16, 2);  // Initialize LCD (I2C address 0x27, 16x2)

void setup() {
  // Start I2C communication
  Wire.begin();
  
  // Initialize RTC
  if (!rtc.begin()) {
    lcd.clear();
    lcd.print("Couldn't find RTC");
    while (1);  // Infinite loop if RTC is not connected
  }
  
  // Set RTC to the current date and time when the sketch is compiled
  rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  
  // Print a welcome message on the LCD
  lcd.begin(16, 2);
  lcd.setBacklight(1);  // Turn on backlight (optional)
  lcd.clear();
  lcd.print("RTC Initialized");
  delay(2000);
}

void loop() {
  // Get current time
  DateTime now = rtc.now();

  // Clear LCD and print current time
  lcd.clear();
  
  // Print time in HH:MM:SS format
  lcd.setCursor(0, 0);
  lcd.print("Time: ");
  lcd.print(now.hour(), DEC);  // Print the hour
  lcd.print(":");
  lcd.print(now.minute(), DEC);  // Print the minute
  lcd.print(":");
  lcd.print(now.second(), DEC);  // Print the second

  // Print date in DD/MM/YYYY format
  lcd.setCursor(0, 1);
  lcd.print("Date: ");
  lcd.print(now.day(), DEC);  // Print the day
  lcd.print("/");
  lcd.print(now.month(), DEC);  // Print the month
  lcd.print("/");
  lcd.print(now.year(), DEC);  // Print the year
  
  delay(1000);  // Update every second
}

Explanation of the Code

1. Libraries Used:
   • Wire.h: This library is necessary for I2C communication between the Arduino and the RTC module.
   • LiquidCrystal_I2C.h: This library allows you to control the LCD screen via I2C communication, making the wiring simpler.
   • RTClib.h: This library allows communication with the DS3231 RTC module.
2. RTC Initialization:
   • rtc.begin(): Initializes the DS3231 RTC module. If the RTC is not found, the code will display an error message on the LCD and halt.
3. Setting the RTC:
   • rtc.adjust(DateTime(F(__DATE__), F(__TIME__))): This sets the RTC to the date and time when the sketch was compiled. The __DATE__ and __TIME__ are preprocessor macros in Arduino that represent the current date and time when the code is compiled.
4. Displaying the Time:
   • rtc.now() fetches the current date and time from the RTC module. The now object contains the hour, minute, second, day, month, and year.
   • The time is displayed in the format HH:MM:SS and the date is displayed as DD/MM/YYYY.
5. LCD Updates:
   • The LCD display is updated every second (delay(1000)), so the displayed time is refreshed regularly.

Conclusion:

This Arduino project demonstrates how to interface an RTC module with a 16×2 LCD to display the current time and date. With this setup, you can easily display real-time information on an LCD, making it useful for projects like clocks, timers, or data logging systems.