How to interface MOC (motorola opto-coupler) sensor with AT89C51

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Let's learn how to interface a MOC sensor with our baby (8051uC)

Description

 This article helps you to understand the concept behind the interfacing of MOC(Motorola Opto Coupler). It basically consists of IR(Infra-red) transmitter and  a photo-diode. Normally Photo-diode continuously receives the signal form IR transmitter, the moment between any obstacle inside the sensor, photo-diode stops receiving the IR from IR Transmitter and transmits a low pulse. We have to read that low pulse and have to make logic , what we have to control as an output device.

Programming

1:  #include<reg51.h>      // header file  
2:  void delay(int time)    // function to generate delay  
3:     {  
4:     int i,j;  
5:     for(i=0;i<=time;i++) // i will run from 0 to user defined value  
6:     for(j=0;j<=1275;j++); // j will run from 0 to 1275 "time" times  
7:     }  
8:  sbit sensor=P3^0;  
9:  sbit led=P3^1;  
10:               /*if sensor transmits high pulse*/  
11:  void main()       // main function  
12:    {  
13:    led=0;        // setting led initially off  
14:    sensor=0;// putting sensor pin to 0 so that we can read high pulse  
15:     while(1)      // while(1)used to provide continous loop  
16:      {  
17:       if(sensor==1)  // if sensor provides high input  
18:        {  
19:        led=1;    // light will be on  
20:        delay(200)  // light will remain on for this specified delay  
21:        led=0; // light will off and again on when sensor will be 1   
22:        }   
23:      }  
24:    }  

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Hope you all like this post and I wish this must be useful for you.

Thanks :)