Automatic School Bell Using Arduino

 

(Time Table Bell Alarm System)

This project automatically rings a school/college bell at predefined times according to a timetable. It is very popular for B.Tech 1st year, diploma, and IoT basics.

🎯 Project Objective

To design an Arduino-based automatic bell system that:

• Rings the bell at fixed periods

• Reduces manual effort

• Works accurately using RTC (Real Time Clock)

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🧠 Working Principle

• RTC module (DS3231/DS1307) keeps real-time even after power loss

• Arduino continuously compares current time with stored timetable

• When time matches → Relay ON → Bell rings

• After few seconds → Relay OFF

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🧰 Components Required

Component	Quantity
Arduino UNO	1
RTC Module (DS3231 recommended)	1
Relay Module (5V)	1
Electric Bell / Buzzer	1
16×2 LCD (optional)	1
Jumper Wires	As required
Power Supply (9V/12V)	1

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🔌 Circuit Connections

RTC (DS3231) → Arduino

RTC Pin	Arduino Pin
VCC	5V
GND	GND
SDA	A4
SCL	A5

Relay Module → Arduino

Relay	Arduino
IN	D8
VCC	5V
GND	GND

⚠️ Bell is connected via relay COM & NO terminals

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⏰ Example Time Table

Period	Time
Morning Bell	09:00
Period 1	09:45
Period 2	10:30
Lunch	12:30
School Over	16:00

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💻 Arduino Code (Fully Working)

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

RTC_DS3231 rtc;

int relayPin = 8;

// Set bell times (HH, MM)
int bellHour[]   = {9, 9, 10, 12, 16};
int bellMinute[] = {0, 45, 30, 30, 0};
int totalBells = 5;

void setup() {
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, HIGH);

  Serial.begin(9600);
  rtc.begin();

  // Uncomment only once to set RTC time
  // rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
}

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

  for (int i = 0; i < totalBells; i++) {
    if (now.hour() == bellHour[i] && 
        now.minute() == bellMinute[i] && 
        now.second() == 0) {

      ringBell();
      delay(60000); // Avoid repeat ring
    }
  }
}

void ringBell() {
  digitalWrite(relayPin, LOW); // Bell ON
  delay(5000);                 // 5 seconds
  digitalWrite(relayPin, HIGH);// Bell OFF
}

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📌 Features

✅ Fully automatic
✅ Accurate time using RTC
✅ Easy to modify timetable
✅ Low cost
✅ Reliable for schools & colleges

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📚 Applications

• Schools & Colleges

• Factories (Shift Bell)

• Offices

• Prayer Timers

• Exam Halls