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[51] Relay interface with 8051

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hirenn

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Hi

I want to build a project with relay,switch and 8051

my logic is as below

- when pressed Switch Start Relay
- wait for pulse 60 seconds,
- if pulse there withing 60 sec then continuous on relay,
if no pulse then wait another 60 sec
- after 120 second if no pulse then make relay off and again check for switch pressed

thanks
 

hirenn said:
Hi

I want to build a project with relay,switch and 8051
...
thanks
Click to expand...
Thanks for sharing this with us!
:-D

ps. you obviously forgot to tell what your problem is...
 

Hi !

my problem is i dont know how to do this logic . . .

thanks
 

If there is pulse between 60 and 120 second ? Where does the pulse come from ? Is it actually a pulse or some low to high transition which remains in high state after transmission ?

Edit: If pulse is detected between 60 and 120 sec then Relay is turned ON ?
 
Last edited:

Use interrupt concept for detecting pulse, update the timer value with 60. Decrement the timer value in the while loop, when the timer goes zero switch off the relay.
 
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    hirenn

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I can do this but if you can use PIC18F458.

Here is the Keil C51 Code for AT89C51. INT0 is switch and button not pressed state is high. Button has to be pressed and released. Pulse has to go high and then low.

Code C - [expand]
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#include <REGx51.h>
 
#define ON 1
#define OFF 0
 
sbit RELAY = P1^0;
 
char myFlags = 0, count = 0, waitCounter = 0;
 
char pulseDetectedFlag = 0;
 
void ex0_isr (void) interrupt 0 {
     EX0 = 0;     
     EX1 = 1;     
     TR1 = 1;
}
 
void ex1_isr (void) interrupt 2 {
 
     if(waitCounter == 0) {
          RELAY = ON;        //Continuous ON
 
          ET1 = 1;
          IT1 = 0;
          EX1 = 0;
          
          TMOD = 0x10;
          TH1 = 0x27;
          TL1 = 0xFD;
          TR1 = 0;
          
          waitCounter = 0;
     }
     else if(waitCounter == 1) {
          RELAY = ON;        //Pulse between 60 and 120 sec
 
     }
 
     pulseDetectedFlag = 1;
}
 
void timer1_isr (void) interrupt 4 {
 
        TF1 = 0;
        TH1 = 0x27;
        TL1 = 0xFD;
          
        if(++count == 100) {
             count = 0;
             waitCounter++;
             if(waitCounter == 2) {
                    if(pulseDetectedFlag == 0) {
                            RELAY = OFF;
                            
                            EX0 = 1;                            
                            EX1 = 0;                            
                            TR1 = 0;
                    }
             }
 
        }
     
        TF1 = 0;
 
}
 
void main() {
 
    P0 = 0x00;
    P1 = 0x00;
    P2 = 0x00;
    P3 = 0x0C;
 
        EX0 = 1;
    IT0 = 0;
    EA = 1;
    
        while(1);
 
}


broken link removed
 

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  • Relay Control.rar
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  • relay_control.png
    relay_control.png
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