Introduction

A digital clock is a clock that displays time in numbers rather than hands on a dial. The first digital clock was invented by Josef Pallweber which used the “jump-hour” mechanism in 1883. The working principle of his clock is the use of rotating discs which displayed the hour and minutes. Since his invention, there has been a rapid development of digital clocks.

Digital clocks typically use oscillation of AC power (50 Hz / 60 Hz) or 32.768 kHz crystal oscillator as seen in quartz clock to keep time. We have two different display formats for digital clock namely: 24-hour format or 12-hour format. Liquid crystal display is used by some of the clocks while others use 7 segment display.

Design

The proposed digital clock uses a dedicated micro controller and a 20 MHz crystal oscillator. A 16×2 LCD is used to display the time. A keypad is used to set the time. Here we used the sinus board to design a digital clock. The schematic for the digital clock is shown

The source code is developed using mikroc pro.

//PROGRAM WRITTEN BY NDUKWE SAMUEL C.
//SAMSONIC TECHNOLOGIES AND CONSULTS
//digital clock   USING PIC18

#define ok           PORTD.F6
#define up           PORTD.F7
#define down         PORTD.F5
#define pressed      0

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

      sbit LCD_RS_Direction at TRISB2_bit;
      sbit LCD_EN_Direction at TRISB3_bit;
      sbit LCD_D4_Direction at TRISB4_bit;
      sbit LCD_D5_Direction at TRISB5_bit;
      sbit LCD_D6_Direction at TRISB6_bit;
      sbit LCD_D7_Direction at TRISB7_bit;


int counter = 0;
int sec = 0;
int minu = 0;
int hr = 0;
int num = 0;
char *hrTM   = "00";
char *minuTM = "00";
char *secTM  = "00";



void Interrupt(){
     if(TMR0IF_bit){
         TMR0IF_bit = 0;
         TMR0H = 0XEC;
         TMR0L = 0X78;
         counter++;
         if (counter == 1000){
            counter = 0;
            sec++;
         }
         if (sec == 60){
            sec = 0;
            minu++;
         }
         if(minu == 60){
            minu = 0;
            hr++;
         }
         if(hr == 24){
            hr = 0;
         }
         if(hr<0) hr = 0;
         if(minu < 0) minu = 0;
     }

}
void setting(){

     if(ok == pressed){ 
           num++;
           delay_ms(200);
           Lcd_Cmd(_LCD_CLEAR);
           Lcd_Cmd(_LCD_CURSOR_OFF);
     }
     if (num == 3) num = 0;
     
     switch (num){
            case 1: LCD_Out(2,1,"^^");
                    if(up == pressed) {
                        hr++;
                        delay_ms(200);
                     }
                    if(down == pressed){
                         hr--;
                         delay_ms(200);
                     }
                    break;
     
            case 2: LCD_Out(2,4,"^^");
                    if(up == pressed) {
                         minu++;
                         delay_ms(200);
                    }
                    if(down == pressed){
                          minu--;
                          delay_ms(200);
                    }
                    break;
            
            case 3: num = 0;
                    break;
     }
     
     
}

void main(){
    T0CON = 0X88;
    TMR0H = 0XEC;
    TMR0L = 0X78;
    GIE_bit = 1;
    TMR0IE_bit = 1;
    TRISD.F5 = 1;
    TRISD.F6 = 1;
    TRISD.F7 = 1;
    PORTD.F5 = 0;
    PORTD.F6 = 0;
    PORTD.F7 = 0;
    ADCON1 =  0b00000111;
    LCD_Init();
    Lcd_Cmd(_LCD_CLEAR);
    Lcd_Cmd(_LCD_CURSOR_OFF);
    hr = 10;
    minu = 58;
    sec = 0;
    
    while(1){
    setting();
    LCD_OUT(1,3, ":");
    LCD_OUT(1,6, ":");
    secTm[0] = (sec/10) + 48;
    secTm[1] = (sec%10) + 48;
    minuTm[0] = (minu/10) + 48;
    minuTm[1] = (minu%10) + 48;
    hrTm[0] = (hr/10) + 48;
    hrTm[1] = (hr%10) + 48;
    LCD_OUT (1,1, hrTm);
    LCD_OUT (1,4, minuTm);
    Lcd_OUT (1,7, secTm);
     
    }

}
                                        
                                            

working video :