In this blog post, we will guide you through making a DIY RTC Digital Clock using an Arduino UNO and an I2C LCD. We will also explain the provided circuit diagram, how to design and order a PCB from PCBWay, and why PCBWay is the best choice for high-quality PCBs.

Circuit Diagram Explanation

The schematic consists of an ATmega328P microcontroller, an RTC module, an I2C LCD, and other supporting components. The microcontroller manages the real-time clock functionality and displays the time on the LCD screen.

Key Components Used:

1. Microcontroller: ATmega328P-PU
2. Real-Time Clock Module: DS3231
3. Display: 16x2 LCD with I2C interface
4. Voltage Regulator: 7805 for 5V regulation
5. Diodes: 1N4007 for reverse polarity protection
6. Transistors: BC547B for switching
7. Capacitors: 22pF and 220uF for stability
8. Resistors: 10kΩ, 1kΩ
9. Crystal Oscillator: 16MHz
10. Relay Module: For controlling external devices
11. LED Indicators: For power and status indication

Hardware Connections & Explanation

1. I2C LCD: The I2C LCD is connected to the ATmega328P microcontroller via SDA (A4) and SCL (A5) lines. This reduces the number of GPIO pins required for communication.
2. RTC Module: The DS3231 RTC module communicates via I2C and provides accurate timekeeping.
3. Power Supply: The circuit operates at 5V, regulated by the 7805 voltage regulator.
4. Relay Control: The relay is controlled by a transistor to switch external loads.

Working Principle

1. The RTC module keeps track of the real-time clock and communicates with the microcontroller via I2C.
2. The microcontroller reads the time data and displays it on the LCD.
3. A relay is incorporated to control external devices based on time settings.
4. The system is powered by a stable 5V regulated supply to ensure smooth operation.

How the RTC Module Works & Calibration

The DS3231 RTC module is a highly accurate real-time clock with an inbuilt temperature-compensated crystal oscillator. It maintains time even when power is removed, thanks to its onboard battery backup.

Calibration with Arduino UNO

Connect the RTC Module to Arduino:

VCC → 5V

GND → GND

SDA → A4

SCL → A5

Upload the following code to set the correct time:

#include <Wire.h>

#include <RTClib.h>

RTC_DS3231 rtc;

void setup() {

Serial.begin(9600);

if (!rtc.begin()) {

Serial.println("RTC not found!");

while (1);

}

rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));

Serial.println("RTC Set to Compilation Time");

}

void loop() {}

Verify RTC Time: Upload the code below to read and display the RTC time.

void loop() {

DateTime now = rtc.now();

Serial.print(now.year(), DEC);

Serial.print("/");

Serial.print(now.month(), DEC);

Serial.print("/");

Serial.print(now.day(), DEC);

Serial.print(" ");

Serial.print(now.hour(), DEC);

Serial.print(":");

Serial.print(now.minute(), DEC);

Serial.print(":");

Serial.println(now.second(), DEC);

delay(1000);

}

Arduino Code for RTC Digital Clock

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

#include <RTClib.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

RTC_DS3231 rtc;

void setup() {

lcd.begin();

lcd.backlight();

if (!rtc.begin()) {

lcd.print("RTC ERROR");

while (1);

}

rtc.adjust(DateTime(__DATE__, __TIME__)); // Set to compile time

}

void loop() {

DateTime now = rtc.now();

lcd.setCursor(0, 0);

lcd.print("Time: ");

lcd.print(now.hour(), DEC);

lcd.print(":");

lcd.print(now.minute(), DEC);

lcd.print(":");

lcd.print(now.second(), DEC);

delay(1000);

}

Code Explanation

RTC Initialization: The DS3231 module is initialized using the RTClib library.

LCD Display: The I2C LCD module displays real-time clock data.

Time Adjustment: The RTC is set to the current compile time when the program is uploaded.

Loop Function:

Continuously reads the RTC time.

Displays the time on the LCD.

Refreshes every second to keep it updated.

PCB Design & Ordering from PCBWay

Conclusion

By following this guide, you can build a professional RTC Digital Clock using an Arduino UNO and an I2C LCD. This project provides a practical way to understand RTC communication, LCD interfacing, and relay control. Using PCBWay for PCB manufacturing ensures high quality and reliability. Happy DIYing!