want ir LONG RANGE ciruit for reflected type ir sensor

#include <REG2051.H>
void delay1(void);
sbit mybit=P1^2;

void main(void)
{
while(1)
{
mybit=~mybit;
delay1();

}
}
void delay1(void)
{

TMOD=0X02;
// TL0=0XF4;
TH0=0xf4;
TR0=1;
while(TF0==0);
TR0=0;
TF0=0;
}

sir plz telll me now whats wrong with this code why is not produce excat 38khz i have checked on proteus the frequency its producing is 16khz..:(

if I were you, I would use interrupt for generating 38Khz square wave.

void timer0_isr () interrupt 1
{
	mybit = ~mybit;
}

void main ()
{
	TMOD = 0X02;
	TH0 = 0xf4;
	TL0 = 0xF4
	IE = 0x82;
	TR0 = 1;
	while(1);
}

but y sir..isnt my code and calculation was correct?? i have to use interrupt when i detect the person and perform sum function in that..!

At 38kHz a full cycle is 26.3 micro seconds.
You would need to toggle the output every 13 micro seconds.
This 13 micro seconds includes the time for the micro to call delay() and set up the registers.

Given the processing overheads trial and error may be the best method , but it may not be possible !
Try a simple loop in assembly code .

now i have genrated the 38khz frequency using crystal vallue 11.0582mhz but still no good sign of detection low output at tsop1738,also the pin a microcontroller as per where pulses are genrating i am getting no variation in voltage practical its shold 5v then 0 on off on off resulting pulses but voltage is constant 2.5v..:(

#include <REG2051.H>

void delay1(void);
sbit mybit=P1^7;


void timer0_isr () interrupt 1
{
        mybit = ~mybit;
}

void main ()
{
	P1=0x00;
        TMOD = 0X02;
        TH0 = 0xf4;
        TL0 = 0xF4;
        IE = 0x82;
        TR0 = 1;
        while(1);
	
}

Are you sure you are using TSOP1738? its not 1736? coz market has all kind of variants and often seller mix them up. they are one of the common part of TV IR receivers. Try 36Khz too and see what happens.

ok sir i will first chck,,..!

ok now when i started detecting low voltage at TSOP but range too short as in just 5cm hardly..!
the 38khz output pin of micntrl have voltage 2.4v which is further feed to ir transmitter with resistace of 100ohm..

2.4 is fine as we have 50% duty cycle. so output voltage becomes half when you check using a multimeter. if you check on Oscilloscope you will see pulses going from 0 to 5V. Make sure you driver IR led using a transistor like 2N2222. remote control uses similar transistor for driving IR LEDs for good range.