How to interface LDR( Light Dependent Resistor ) with AT89C51

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

Description

 This article helps you to understand the concept behind the interfacing of LDR(Light Dependent Resistor). The value of resistance is totally depends upon the  light. With increase in light on ldr resistance decreases and vice versa and the same is shown in video below.Sensors are basically input device that provide us the input signal when they sense the thing for which they are designed. Here I will show you how to read input from a ldr sensor and how to control output with that input pulse.

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 continuous 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:    }  

For enhance concept just visit www.salahtutorials.com

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

Thanks :)