Automatic School / College Bell using PIC Microcontroller

Automatic School / College Bell using PIC Microcontroller

Here we are sharing a fully automatic and configurable bell which can be used in schools and colleges. It is made using commonly available microcontroller and other components.

Components Required

  • PIC 18F4550
  • 16×2 LCD Display
  • DS1307 or DS3232
  • 32.768 kHz Crystal
  • 16 MHz Crystal
  • 4.7K Resistor – 7
  • 10K Resistor
  • 10K Preset
  • 22pF Capacitor – 2
  • 100nF Capacitor
  • 4×4 Keypad
  • 680R Resistor
  • LED – 1
  • 3V CMOS Battery
  • BC548
  • 1N4148
  • Relay (5V/12V)

Circuit Diagram

Automatic College Bell using Microcontroller - Circuit Diagram

Automatic College Bell using Microcontroller – Circuit Diagram

How to connect the Bell ?

Program

The microcontroller program is written using MikroC Pro compiler.

#define MENU_KEY 'D'
#define SAVE_EXIT '*'
#define BELL_TIME 60

// LCD module connections
sbit LCD_RS at RB7_bit;
sbit LCD_EN at RB6_bit;
sbit LCD_D4 at RB5_bit;
sbit LCD_D5 at RB4_bit;
sbit LCD_D6 at RB3_bit;
sbit LCD_D7 at RB2_bit;

sbit LCD_RS_Direction at TRISB7_bit;
sbit LCD_EN_Direction at TRISB6_bit;
sbit LCD_D4_Direction at TRISB5_bit;
sbit LCD_D5_Direction at TRISB4_bit;
sbit LCD_D6_Direction at TRISB3_bit;
sbit LCD_D7_Direction at TRISB2_bit;
// End LCD module connections

// Keypad Connections
sbit KEY_R1 at LATD0_bit;
sbit KEY_R0 at LATD1_bit;
sbit KEY_R3 at LATD6_bit;
sbit KEY_R2 at LATD7_bit;
sbit KEY_C0 at RD3_bit;
sbit KEY_C1 at RD2_bit;
sbit KEY_C2 at RD4_bit;
sbit KEY_C3 at RD5_bit;

sbit KEY_R1_Direction at TRISD0_bit;
sbit KEY_R0_Direction at TRISD1_bit;
sbit KEY_R3_Direction at TRISD6_bit;
sbit KEY_R2_Direction at TRISD7_bit;
sbit KEY_C0_Direction at TRISD3_bit;
sbit KEY_C1_Direction at TRISD2_bit;
sbit KEY_C2_Direction at TRISD4_bit;
sbit KEY_C3_Direction at TRISD5_bit;
// End Keypad Connections

void keypadInit()
{
  KEY_C0_Direction = 1;
  KEY_C1_Direction = 1;
  KEY_C2_Direction = 1;
  KEY_C3_Direction = 1;

  KEY_R0_Direction = 0;
  KEY_R1_Direction = 0;
  KEY_R2_Direction = 0;
  KEY_R3_Direction = 0;

  KEY_R0 = 1;
  KEY_R1 = 1;
  KEY_R2 = 1;
  KEY_R3 = 1;
}

unsigned readKeypad()
{
  KEY_R0 = 0;
  Delay_ms(1);
  if(KEY_C0 == 0)
  {
    while(KEY_C0 == 0);
    return 1;
  }
  else if(KEY_C1 == 0)
  {
    while(KEY_C1 == 0);
    return 2;
  }
  else if(KEY_C2 == 0)
  {
    while(KEY_C2 == 0);
    return 3;
  }
  else if(KEY_C3 == 0)
  {
    while(KEY_C3 == 0);
    return 4;
  }
  KEY_R0 = 1;

  KEY_R1 = 0;
  Delay_ms(1);
  if(KEY_C0 == 0)
  {
    while(KEY_C0 == 0);
    return 5;
  }
  else if(KEY_C1 == 0)
  {
    while(KEY_C1 == 0);
    return 6;
  }
  else if(KEY_C2 == 0)
  {
    while(KEY_C2 == 0);
    return 7;
  }
  else if(KEY_C3 == 0)
  {
    while(KEY_C3 == 0);
    return 8;
  }

  KEY_R1 = 1;

  KEY_R2 = 0;
  Delay_ms(1);
  if(KEY_C0 == 0)
  {
    while(KEY_C0 == 0);
    return 9;
  }
  else if(KEY_C1 == 0)
  {
    while(KEY_C1 == 0);
    return 10;
  }
  else if(KEY_C2 == 0)
  {
    while(KEY_C2 == 0);
    return 11;
  }
  else if(KEY_C3 == 0)
  {
    while(KEY_C3 == 0);
    return 12;
  }
  KEY_R2 = 1;

  KEY_R3 = 0;
  Delay_ms(1);
  if(KEY_C0 == 0)
  {
    while(KEY_C0 == 0);
    return 13;
  }
  else if(KEY_C1 == 0)
  {
    while(KEY_C1 == 0);
    return 14;
  }
  else if(KEY_C2 == 0)
  {
    while(KEY_C2 == 0);
    return 15;
  }
  else if(KEY_C3 == 0)
  {
    while(KEY_C3 == 0);
    return 16;
  }
  KEY_R3 = 1;
  return 0;
}

unsigned readDS3231(unsigned address)
{
  unsigned short r_data;
  I2C1_Start();
  I2C1_Wr(0xD0); //address 0x68 followed by direction bit (0 for write, 1 for read) 0x68 followed by 0 --> 0xD0
  I2C1_Wr(address);
  I2C1_Repeated_Start();
  I2C1_Wr(0xD1); //0x68 followed by 1 --> 0xD1
  r_data=I2C1_Rd(0);
  I2C1_Stop();
  return(r_data);
}

void writeDS3231(unsigned address,unsigned w_data)
{
  I2C1_Start(); // issue I2C start signal
  //address 0x68 followed by direction bit (0 for write, 1 for read) 0x68 followed by 0 --> 0xD0
  I2C1_Wr(0xD0); // send byte via I2C (device address + W)
  I2C1_Wr(address); // send byte (address of DS1307 location)
  I2C1_Wr(w_data); // send data (data to be written)
  I2C1_Stop(); // issue I2C stop signal
}

char BCD2UpperCh(unsigned bcd)
{
  return ((char)((bcd >> 4) + '0'));
}

char BCD2LowerCh(unsigned bcd)
{
  return ((char)((bcd & 0x0F) + '0'));
}

unsigned Binary2BCD(unsigned a)
{
  int t1, t2;
  t1 = a%10;
  t1 = t1 & 0x0F;
  a = a/10;
  t2 = a%10;
  t2 = 0x0F & t2;
  t2 = t2 << 4;
  t2 = 0xF0 & t2;
  t1 = t1 | t2;
  return t1;
}

unsigned BCD2Binary(unsigned a)
{
  unsigned r,t;
  t = a & 0x0F;
  r = t;
  a = 0xF0 & a;
  t = a >> 4;
  t = 0x0F & t;
  r = t*10 + r;
  return r;
}

char* getDay(unsigned d)
{
  static char day[10];

  switch(d)
  {
    case 0 : strcpy(day, "Set Time ");
             break;
    case 1 : strcpy(day, "Sunday ");
             break;
    case 2 : strcpy(day, "Monday ");
             break;
    case 3 : strcpy(day, "Tuesday ");
             break;
    case 4 : strcpy(day, "Wednesday");
             break;
    case 5 : strcpy(day, "Thursday ");
             break;
    case 6 : strcpy(day, "Friday ");
             break;
    case 7 : strcpy(day, "Saturday ");
             break;
    default : strcpy(day, "INVALID ");
              break;
  }
  return day;
}

char decodeKeys(unsigned key)
{
  switch(key)
  {
    case 1 : return '6';
    case 2 : return '=';
    case 3 : return '3';
    case 4 : return '9'; //Not Available in 4x3 Keypad
    case 5 : return '*';
    case 6 : return '+';
    case 7 : return '-';
    case 8 : return '/'; //Not Available in 4x3 Keypad
    case 9 : return '5';
    case 10 : return '0';
    case 11 : return '2';
    case 12 : return '8'; //Not Available in 4x3 Keypad
    case 13 : return '4';
    case 14 : return 'N';
    case 15 : return '1';
    case 16 : return '7'; //Not Availabale in 4x3 Keypad
    default : return 0;
  }
}

void main()
{
  unsigned second, minute, hour, hr, day, dday, month, year, bellHour, bellMinute, hourB, minuteB, ls, bt, btLatch;
  unsigned menu = 0, mode = 0, mt, temp, temp2, normalBC, examBC, flag, ah = 0, am = 0, maxBell = 0, bs = 0, bc = 0, bellActive = 0, bellCnt = 0;
  char kp;
  char time[] = "00:00:00 ";
  char date[] = "00-00-00 ";

  ADCON1 = 0x0F;
  TRISA.F0 = 0;
  LATA.F0 = 0;
  I2C1_Init(90000); //DS1307 I2C is running at 50KHz

  keypadInit();

  Lcd_Init(); // Initialize LCD
  Lcd_Cmd(_LCD_CLEAR); // Clear display
  Lcd_Cmd(_LCD_CURSOR_OFF); // Cursor off

  Lcd_Cmd(_LCD_CLEAR); // Clear display
  Lcd_Cmd(_LCD_CURSOR_OFF); // Cursor off
  // Lcd_Cmd(_LCD_BLINK_CURSOR_ON);
  Lcd_out(1,1,"Time:");
  //Lcd_out(2,1,"Date:");

  if(EEPROM_Read(0) == 0xAA)
  {
    normalBC = EEPROM_Read(1);
    examBC = EEPROM_Read(128);
  }
  else
  {
    normalBC = 0;
    examBC = 0;
    EEPROM_Write(1, 0);
    EEPROM_Write(128, 0);
    EEPROM_Write(0, 0xAA);
  }

  bt = 0;

  while(1)
  {
    second = readDS3231(0);
    minute = readDS3231(1);
    hour = readDS3231(2);
    hr = hour & 0b00111111;
    dday = readDS3231(3);
    day = readDS3231(4);
    month = readDS3231(5);
    year = readDS3231(6);

    hourB = BCD2Binary(hour);
    minuteB = BCD2Binary(minute);

    time[0] = BCD2UpperCh(hr);
    time[1] = BCD2LowerCh(hr);
    time[3] = BCD2UpperCh(minute);
    time[4] = BCD2LowerCh(minute);
    time[6] = BCD2UpperCh(second);
    time[7] = BCD2LowerCh(second);

    date[0] = BCD2UpperCh(day);
    date[1] = BCD2LowerCh(day);
    date[3] = BCD2UpperCh(month);
    date[4] = BCD2LowerCh(month);
    date[6] = BCD2UpperCh(year);
    date[7] = BCD2LowerCh(year);

    if(bs == 0)
    {
      if(mode == 0) //Normal Mode
      {
        if(dday != 6) //If Not Friday
        {
          bt = EEPROM_Read(bc*3 + 2);
          if(bt == 0xAA)
            bt = 2;
          else
            bt = 1;

          bellHour = EEPROM_Read(bc*3 + 3);
          bellMinute = EEPROM_Read(bc*3 + 4);
        }
        else //If Friday
        {
          bt = EEPROM_Read(bc*3 + 65);
          if(bt == 0xAA)
            bt = 2;
          else
            bt = 1;
          bellHour = EEPROM_Read(bc*3 + 66);
          bellMinute = EEPROM_Read(bc*3 + 67);
        }
         maxBell = normalBC;
      }
      else if(mode == 1)
      {
        if(dday != 6) //If Not Friday
        {
          bt = EEPROM_Read(129 + bc*3);
          if(bt == 0xAA)
            bt = 2;
          else
            bt = 1;
          bellHour = EEPROM_Read(130 + bc*3);
          bellMinute = EEPROM_Read(131 + bc*3);
        }
        else //If Friday
        {
          bt = EEPROM_Read(191 + bc*3);
          if(bt == 0xAA)
            bt = 2;
          else
            bt = 1;
          bellHour = EEPROM_Read(192 + bc*3);
          bellMinute = EEPROM_Read(193 + bc*3);
        }
        maxBell = examBC;
      }
      if(bellHour < hourB)
        bc++;
      else if(bellMinute <= minuteB)
        bc++;
      else
      {
        bs = 1;
        bc++;
      }

      if(bc > maxBell)
        bc = 0;
      }
      else
      {
        if(hourB >= bellHour)
        {
          if(minuteB >= bellMinute)
          {
            bellActive = 1;
            btLatch = bt;
            bs = 0;
          }
        }
      }

      if(bellActive == 1)
      {
        LATA.F0 = 1;
        bellCnt++;
        Delay_ms(2);
        if(bellCnt > (BELL_TIME * btLatch))
        {
          bellActive = 0;
          bellCnt = 0;
        }
      }
      else
      {
        LATA.F0 = 0;
        bellCnt = 0;
      }

      kp = decodeKeys(readKeypad()); //Read Keypad

      if(kp == MENU_KEY) //Menu Selection via * button
      {
        menu++;
        mt = 0;
        if(menu > 5)
          menu = 0;
        }
        else if(isdigit(kp)) //If numberic value press
        {
          if(menu)
          {
            mt++;
            flag = 1;
          }
        }
        else if(kp == SAVE_EXIT) //Exit or Change Mode when # Pressed
        {
          if(menu)
            menu = 0; //Exit settings
          else
            mode = !mode; //Change Mode
          mt = 0;
        }

        if(menu == 0)
        {
          Lcd_out(1,1,"Time:");
          Lcd_out(1, 6, time);
          if(mode == 0)
            Lcd_out(2, 1, "NORMAL:");
          else
            Lcd_out(2, 1, "EXAM :");

          Lcd_out(2, 8, getDay(dday));
        }
        else if(menu == 1) //Set Time
        {
          Lcd_Out(1, 1, "Set Time ");
          Lcd_Out(2, 1, "Time: ");
          Lcd_Out(2, 7, time);
          if(mt && kp)
          {
            if(mt == 1 && kp < '3')
            {
              Lcd_Out(1,1,0);
              hour = 0x3F & BCD2Binary(hr);
              temp = hour % 10;
              hour = (kp - 48)*10 + temp;
              if(hour > 23)
                hour = 23;
              hour = Binary2BCD(hour);
                hour = hour & 0x3F;
              writeDS3231(2, hour);
            }
            else if(mt == 2)
            {
              hour = 0x3F & BCD2Binary(hr);
              hour = hour/10;
              hour = hour*10 + (kp - 48);
              hour = hour & 0x3F;
              if(hour < 24)
              {
                hour = Binary2BCD(hour);
                writeDS3231(2, hour);
              }
            }
            else if(mt == 3 && kp < '6')
            {
              minute = BCD2Binary(minute);
              temp = minute % 10;

              minute = (kp - 48)*10 + temp;
              minute = Binary2BCD(minute);
              writeDS3231(1, minute);
            }
            else if(mt == 4)
            {
              minute = BCD2Binary(minute);
              minute = minute/10;
              minute = minute*10 + (kp - 48);
              if(minute < 60)
              {
                minute = Binary2BCD(minute);
                writeDS3231(1, minute);
              }
            }
            else if(mt == 5)
            {
              second = 0;
              writeDS3231(0, second);
              menu = 0;
              mt = 0;
            }
          }
        }
        else if(menu == 2) // Set Date
        {
          Lcd_Out(1, 1, "Set Date ");
          Lcd_Out(2, 1, "Date: ");
          Lcd_Out(2, 7, date);

          if(mt && kp)
          {
            if(mt == 1 && kp < '4')
            {
              day = BCD2Binary(day);
              temp = day % 10;
              day = (kp - 48)*10 + temp;
              day = Binary2BCD(day);
              writeDS3231(4, day);
            }
            else if(mt == 2)
            {
              day = BCD2Binary(day);
              day = day/10;
              day = day*10 + (kp - 48);
              if(day < 32 && day > 0)
              {
                day = Binary2BCD(day);
                writeDS3231(4, day);
              }
            }
            else if(mt == 3 && kp < '2')
            {
              month = BCD2Binary(month);
              temp = month % 10;
              month = (kp - 48)*10 + temp;
              month = Binary2BCD(month);
              writeDS3231(5, month);
            }
            else if(mt == 4)
            {
              month = BCD2Binary(month);
              month = month/10;
              month = month*10 + (kp - 48);
              if(month < 13 && month > 0)
              {
                month = Binary2BCD(month);
                writeDS3231(5, month);
              }
            }
            else if(mt == 5)
            {
              year = BCD2Binary(year);
              temp = year % 10;
              year = (kp - 48)*10 + temp;
              year = Binary2BCD(year);
              writeDS3231(6, year);
            }
            else if(mt == 6)
            {
              year = BCD2Binary(year);
              year = year/10;
              year = year*10 + (kp - 48);
              year = Binary2BCD(year);
              writeDS3231(6, year);
              menu = 0;
              mt = 0;
            }
          }
        }
        else if(menu == 3) // Set Day
        {
          Lcd_Out(1, 1, "Set Day, SUN 1~7");
          Lcd_Out(2, 1, "Day : ");
          Lcd_out(2, 7, getDay(dday));

          if(mt <= 1)
          {
            if(flag == 1)
            {
              if(kp > '0' && kp < '8')
                writeDS3231(3, (unsigned short)((kp - 48)));
              bs = 0;
              bc = 0;
            }
          }
          else
          {
            mt = 0;
            menu = 0;
          }
        }
        else if(menu == 4) //Normal Bell
        {
          Lcd_Out(1, 1, "Set Normal Bell ");

          if(mt < 3)
          {
            Lcd_Out(2, 1, "Total Bells: ");
            Lcd_Chr(2, 15, (char)(normalBC%10) + 48);
            Lcd_Chr(2, 14, (char)((normalBC/10)%10) + 48);
            if(mt == 1)
            {
              if(flag && kp < '2')
              {
                normalBC = ((kp - 48)*10) + normalBC%10;
                EEPROM_Write(1, normalBC);
                flag = 0;
                bs = 0;
                bc = 0;
              }
            }
            else if(mt == 2)
            {
              if(flag)
              {
                temp = ((normalBC/10)*10) + (kp - 48);
                if(temp < 17)
                {
                  normalBC = temp;
                  EEPROM_Write(1, normalBC);
                  flag = 0;
                  bs = 0;
                  bc = 0;
                }
              }
            }
          }
          else if(mt <= (2 + normalBC*6)) //Normal Not Friday
          {
            temp = ((mt - 3)/6);
            temp2 = ((mt - 3)%6);
            if(temp <= normalBC)
            {
              if(temp2 == 0)
              {
                if(flag)
                {
                  ls = EEPROM_Read(temp*3 + 2);
                  ah = EEPROM_Read(temp*3 + 3);
                  am = EEPROM_Read(temp*3 + 4);
                  flag = 0;
                }
              }
              else if(temp2 == 1)
              {
                if(flag)
                {
                  if(kp == '1')
                    ls = 0xAA;
                  else
                    ls = 0x00;
                  EEPROM_Write((temp*3 + 2), ls);
                  flag = 0;
                  bs = 0;
                  bc = 0;
                }
              }
              else if(temp2 == 2)
              {
                if(flag)
                {
                  ah = ((kp - 48)*10) + ah%10;
                  flag = 0;
                  EEPROM_Write(((temp*3) + 3), ah);
                  bs = 0;
                  bc = 0;
                }
              }
              else if(temp2 == 3)
              {
                if(flag)
                {
                  ah = ((ah/10)*10) + (kp - 48);
                  flag = 0;
                  EEPROM_Write(((temp*3) + 3), ah);
                  bs = 0;
                  bc = 0;
                }
              }
              else if(temp2 == 4)
              {
                if(flag)
                {
                  am = ((kp - 48)*10) + am%10;
                  flag = 0;
                  EEPROM_Write(((temp*3) + 4), am);
                  bs = 0;
                  bc = 0;
                }
              }
              else if(temp2 == 5)
              {
                if(flag)
                {
                  am = ((am/10)*10) + (kp - 48);
                  flag = 0;
                  EEPROM_Write(((temp*3) + 4), am);
                  bs = 0;
                  bc = 0;
                }
              }
              Lcd_Out(2, 1, "NDbell : - ");
              Lcd_Chr(2, 8, (temp%10) + 48);
              Lcd_Chr(2, 7, (temp/10) + 48);
              if(ls == 0xAA)
                Lcd_Chr(2, 10, 'L');
              else
                Lcd_Chr(2, 10, 'S');

              Lcd_Chr(2, 12, (ah/10) + 48);
              Lcd_Chr(2, 13, (ah%10) + 48);

              Lcd_Chr(2, 15, (am/10) + 48);
              Lcd_Chr(2, 16, (am%10) + 48);
            }
            else
            {
              mt = 0;
              menu = 0;
            }
          }
          else if(mt <= (2 + 2*normalBC*6)) //Normal Friday
          {
            temp = ((mt - 3 - normalBC*6)/6);
            temp2 = ((mt - 3)%6);
            if(temp <= normalBC)
            {
              if(temp2 == 0)
              {
                if(flag)
                {
                  ls = EEPROM_Read(temp*3 + 65);
                  ah = EEPROM_Read(temp*3 + 66);
                  am = EEPROM_Read(temp*3 + 67);
                  flag = 0;
                }
              }
              else if(temp2 == 1)
              {
                if(flag)
                {
                  if(kp == '1')
                    ls = 0xAA;
                  else
                    ls = 0x00;
                  EEPROM_Write(temp*3 + 65, ls);
                  flag = 0;
                  bs = 0;
                  bc = 0;
                }
              }
              else if(temp2 == 2)
              {
                if(flag)
                {
                  ah = ((kp - 48)*10) + ah%10;
                  flag = 0;
                  EEPROM_Write(temp*3 + 66, ah);
                  bs = 0;
                  bc = 0;
                }
              }
              else if(temp2 == 3)
              {
                if(flag)
                {
                  ah = ((ah/10)*10) + (kp - 48);
                  flag = 0;
                  EEPROM_Write(temp*3 + 66, ah);
                  bs = 0;
                  bc = 0;
                }
              }
              else if(temp2 == 4)
              {
                if(flag)
                {
                  am = ((kp - 48)*10) + am%10;
                  flag = 0;
                  EEPROM_Write((temp*3 + 67), am);
                  bs = 0;
                  bc = 0;
                }
              }
              else if(temp2 == 5)
              {
                if(flag)
                {
                  am = ((am/10)*10) + (kp - 48);
                  flag = 0;
                  EEPROM_Write((temp*3 + 67), am);
                  bs = 0;
                  bc = 0;
                }
              }
              else
              {
                mt = 0;
                menu = 0;
              }
            }
            Lcd_Out(2, 1, "FDbell : - ");
            Lcd_Chr(2, 8, (temp%10) + 48);
            Lcd_Chr(2, 7, (temp/10) + 48);
            if(ls == 0xAA)
              Lcd_Chr(2, 10, 'L');
            else
              Lcd_Chr(2, 10, 'S');

            Lcd_Chr(2, 12, (ah/10) + 48);
            Lcd_Chr(2, 13, (ah%10) + 48);

            Lcd_Chr(2, 15, (am/10) + 48);
            Lcd_Chr(2, 16, (am%10) + 48);
          }
          else
          {
            mt = 0;
            menu = 0;
          }
        }
        else if(menu == 5) //Exam Bell
        {
          Lcd_Out(1, 1, "Set Exam Bell ");

          if(mt < 3)
          {
            Lcd_Out(2, 1, "Total Bells: ");
            Lcd_Chr(2, 15, (char)(examBC%10) + 48);
            Lcd_Chr(2, 14, (char)((examBC/10)%10) + 48);
            if(mt == 1)
            {
              if(flag && kp < '2')
              {
                examBC = ((kp - 48)*10) + examBC%10;
                EEPROM_Write(128, examBC);
                flag = 0;
                bs = 0;
                bc = 0;
              }
            }
            else if(mt == 2)
            {
              if(flag)
              {
                temp = ((examBC/10)*10) + (kp - 48);
                if(temp < 17)
                {
                  examBC = temp;
                  EEPROM_Write(128, examBC);
                  flag = 0;
                  bs = 0;
                  bc = 0;
                }
              }
            }
          }
          else if(mt <= (2 + examBC*6))
          {
            temp = ((mt - 3)/6);
            temp2 = ((mt - 3)%6);
            if(temp <= examBC)
            {
              if(temp2 == 0)
              {
                if(flag)
                {
                  ls = EEPROM_Read(129 + temp*3);
                  ah = EEPROM_Read(130 + temp*3);
                  am = EEPROM_Read(131 + temp*3);
                  flag = 0;
                }
              }
              else if(temp2 == 1)
              {
              if(flag)
              {
                if(kp == '1')
                ls = 0xAA;
              else
                ls = 0x00;
              EEPROM_Write(temp*3 + 129, ls);
              flag = 0;
              bs = 0;
              bc = 0;
            }
          }
          else if(temp2 == 2)
          {
            if(flag)
            {
              ah = ((kp - 48)*10) + ah%10;
              flag = 0;
              EEPROM_Write((130 + temp*3), ah);
              bs = 0;
              bc = 0;
            }
          }
          else if(temp2 == 3)
          {
            if(flag)
            {
              ah = ((ah/10)*10) + (kp - 48);
              flag = 0;
              EEPROM_Write((130 + temp*3), ah);
              bs = 0;
              bc = 0;
            }
          }
          else if(temp2 == 4)
          {
            if(flag)
            {
              am = ((kp - 48)*10) + am%10;
              flag = 0;
              EEPROM_Write((131 + temp*3), am);
              bs = 0;
              bc = 0;
            }
          }
          else if(temp2 == 5)
          {
            if(flag)
            {
              am = ((am/10)*10) + (kp - 48);
              flag = 0;
              EEPROM_Write((131 + temp*3), am);
              bs = 0;
              bc = 0;
            }
          }
          Lcd_Out(2, 1, "NDbell : - ");
          Lcd_Chr(2, 8, (temp%10) + 48);
          Lcd_Chr(2, 7, (temp/10) + 48);
          if(ls == 0xAA)
            Lcd_Chr(2, 10, 'L');
          else
            Lcd_Chr(2, 10, 'S');

            Lcd_Chr(2, 12, (ah/10) + 48);
            Lcd_Chr(2, 13, (ah%10) + 48);

            Lcd_Chr(2, 15, (am/10) + 48);
            Lcd_Chr(2, 16, (am%10) + 48);
          }
          else
          {
            mt = 0;
            menu = 0;
          }
        }
        else if(mt <= (2 + 2*examBC*6))
        {
          temp = ((mt - 3 - examBC*6)/6);
          temp2 = ((mt - 3)%6);
          if(temp <= examBC)
          {
            if(temp2 == 0)
            {
              if(flag)
              {
                ls = EEPROM_Read(191 + temp*3);
                ah = EEPROM_Read(192 + temp*3);
                am = EEPROM_Read(193 + temp*3);
                flag = 0;
              }
            }
            else if(temp2 == 1)
            {
              if(flag)
              {
                if(kp == '1')
                  ls = 0xAA;
                else
                  ls = 0x00;
                EEPROM_Write((191 + temp*3), ls);
                flag = 0;
                bs = 0;
                bc = 0;
              }
            }
            else if(temp2 == 2)
            {
              if(flag)
              {
                ah = ((kp - 48)*10) + ah%10;
                flag = 0;
                EEPROM_Write((192 + temp*3), ah);
                bs = 0;
                bc = 0;
              }
            }
            else if(temp2 == 3)
            {
              if(flag)
              {
                ah = ((ah/10)*10) + (kp - 48);
                flag = 0;
                EEPROM_Write((192 + temp*3), ah);
                bs = 0;
                bc = 0;
              }
            }
            else if(temp2 == 4)
            {
              if(flag)
              {
                am = ((kp - 48)*10) + am%10;
                flag = 0;
                EEPROM_Write((193 + temp*3), am);
                bs = 0;
                bc = 0;
              }
            }
            else if(temp2 == 5)
            {
              if(flag)
              {
                am = ((am/10)*10) + (kp - 48);
                flag = 0;
                EEPROM_Write((193 + temp*3), am);
                bs = 0;
                bc = 0;
              }
            }
            else
            {
              mt = 0;
              menu = 0;
            }
          }
          Lcd_Out(2, 1, "FDbell : - ");
          Lcd_Chr(2, 8, (temp%10) + 48);
          Lcd_Chr(2, 7, (temp/10) + 48);
          if(ls == 0xAA)
            Lcd_Chr(2, 10, 'L');
          else
            Lcd_Chr(2, 10, 'S');

          Lcd_Chr(2, 12, (ah/10) + 48);
          Lcd_Chr(2, 13, (ah%10) + 48);

          Lcd_Chr(2, 15, (am/10) + 48);
          Lcd_Chr(2, 16, (am%10) + 48);
        }
        else
        {
          mt = 0;
          menu = 0;
        }
      }
    Delay_ms(50);
  }
}

Working

Here we have designed a fully automatic and configurable bell which can be used in schools and colleges. The heart of this project is PIC Mircocontroller.

Configuration: Initially we have to set the time, date and day. Also we have to set the number of bells/day and duration of ringing bell with respect to Long duration/Short duration.


Working: As the name itself indicates it will trigger bell automatically at a preset time interval.  After thew configuration, the system starts to monitor the time. Once the time reaches to preset time interval then this module activates the bell. Similarly the process repeats for the remaining time intervals. Even we can set special time for Friday and Exam days. In the below video we have explained for 2 bells.

Output

Automatic School College Bell using PIC Microcontroller

Automatic College Bell

Automatic School Bell

Tips

  • Use Maxim Integrated’s DS3231 RTC for more accurate clock.
  • Use enough capacitors if you are connecting 5V relay to the same power supply. Otherwise relay switching can reset the microcontroller.

Video

Download Here

You can download the program code, hex file, proteus file, circuit diagram etc. here.

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