if(back==1){
              back=0; return;
              }

if(back==1){
              back=0;
              source1=0;
              source2=0;
              source3=0;
              return;
              }

if(d1 ==0)source1=0;
         if(d2 ==0)source2=0;
         if(d3 ==0)source3=0;

#define s1        portb=1
#define s2        portb=2
#define s3        portb=4
#define off_relay portb=0
sbit  d1 at RA0_bit ;
sbit  d2 at RA1_bit ;
sbit  d3 at RA2_bit ;
sbit  buzzer  at RB3_bit ;
char source1=0,source2=0,source3=0, x=0;
char back=0;
//*************************//
void function(char sw);
void  delay_15_sec(char sw1);
void buzzer_function();
//****************************//
void main() 
{ 
 cmcon=7;
 TRISB=0; 
 TRISA=0xFF;
 off_relay;
 while(1)
        {
         if(d1==1 && source1==0)
                  {
                   delay_15_sec(1);// wait 15 sec
                   function(1);
                  }

         else if(d2==1 && d1==0 && source2==0)
                  {
                   delay_15_sec(2);// wait 15 sec
                   function(2);
                  }
         else if(d3==1 && d1==0 && d2==0 && source3==0)
                  {
                   delay_15_sec(3);// wait 15 sec
                   function(3);
                  }
         else if(d1==0 && d2==0 && d3==0)
                  {
                   off_relay;
                  }
         if(d1 ==0)source1=0;
         if(d2 ==0)source2=0;
         if(d3 ==0)source3=0;
        }

}
//**************************************************//
void function(char sw)
{
 if(back==1){
              back=0;
              source1=0;
              source2=0;
              source3=0;
              return;
             }
 if(sw==1)
          { 
           s1;
           source1=1;
           source2=0;
           source3=0;
          }
 else if(sw==2)
               {
                s2;
                source1=0;
                source2=1;
                source3=0;
               }
 else if(sw==3)
               {
                 s3;
                 source1=0;
                 source2=0;
                 source3=1;
               }
}


//*********************************************
void  delay_15_sec(char sw1)
{
 off_relay;
 for(x=0;x<30;x++)// total time =15sec (( 500ms * 30 =15sec))
                  {
                    if(sw1 ==1)
                              {
                               if(d1==0){back=1;return;}
                               buzzer_function();
                              }
                    else if(sw1 ==2)
                              {
                               if(d2==0 || d1==1){back=1;return;}
                               buzzer_function();
                              }
                    else if(sw1 ==3)
                              {
                               if(d3==0 || d1==1 ||d2==1){back=1;return;}
                               buzzer_function();
                              }
                   }
buzzer=0;// for check the buzzer is stop
}
//**********************************************
void buzzer_function()
{ // total delay=100+100+150+150=500ms
 buzzer=1;
 delay_ms(100);
 buzzer=0;
 delay_ms(100);
  buzzer=1;
 delay_ms(150);
 buzzer=0;
 delay_ms(150);

}