Passive Infrared Sensor connected to 8051

[poovi]

HI,

In my project, I am using a PIR sensor to control the lights. When I connect the sensor output to the ULN Driver (which is in turn connected to LEDs though relays), I was able to get proper working of the circuit. But when I use AT89C51 microcontroller to control the system i.e the PIR to the input of the microcontroller (say P2) and ULN driver connected to an output port (say P0), I was not able to get a proper response.  The LEDs would glow continuously when the reset switch on the microcontroller board was kept pressed.  The followinf is the code used. Please help me.

 

 

#include <reg51.h>

sbit pir_in=P2^6;        //PIR module's output pin
sbit ULN_in1= P0^6;     //ULN input pin 1 LED1
sbit ULN_in4= P0^4;    //ULN input pin 4 LED3

int i,j,k;            //looping variables

void init_delay (int a);     //to generate initial delay for the PIR to stabilise

void main()
{
pir_in=1;                     //as input to microcontroller
ULN_in1=0;         //as output
ULN_in4=0;         //as output

init_delay(120);     // 1 minute delay to activate the PIR module

while(1)        //to continuously monitor PIR output
{
while(pir_in==1)
{
ULN_in1=1;          //because the ULN output is the inverse of the ULN input
ULN_in4=1;
}
ULN_in1=0;
ULN_in4=0;
}
}

void init_delay (int a)
{
for(k=a;k>0;k–)
for(i=0; i<1000; i++)
for(j=0; j<1275; j++);
}

[Author]

Posts