pls post me with ir sensor speed measurement code

am using an ir sensor with a +pin , a -pin and a output pin i tried many codes to get the output with lcd ......pls help me with a code

pls help me with a code

That's not the way it works. You post your non-working code, and we help you understand why it doesn't work, and how to fix it.

volatile byte rpmcount = 0;
unsigned long rpm = 0;
unsigned long timeold = 0;
int interrupt = 0;
sen_analog=A0;
#include <LiquidCrystal.h>
LiquidCrystal lcd(8, 9, 10, 11, 12, 13);
void setup()
{lcd.begin(16, 2);
Serial.begin(9600);
attachInterrupt(interrupt,rpmtrigger,FALLING);

}
void loop()
{
if (rpmcount >= 20)
{
rpm=((15000)/(millis()-timeold))*rpmcount;
timeold = millis();
int time = (millis()/1000);
int timedec = (millis()% 1000);
rpmcount = 0;
lcd.print(“RPM = “);
lcd.print(rpm);
lcd.print(” Time = “);
lcd.print(time);
lcd.print(”.”);
lcd.print(timedec);
lcd.println();
}

}
void rpmtrigger()
{
rpmcount++;
}

And we also get very, very upset with people who post the same question in different parts of the forum.

This is called cross-posting and we hate it because IT WASTES TIME.

Cross-post deleted.

Edit: . . . and we also hate it when people don't read the simple posting guidelines displayed at the top of every section of the forum.

It hasn't started well, has it?

i have posted my code sir

tanveer: i have posted my code sir

You have posted it without using code tags. Did you read the posting guidelines at the top of the forum?

unsigned long rpm = 0;

If you are expecting rpm values greater than 32, 767, you are dreaming.

    rpm=((15000)/(millis()-timeold))*rpmcount;

Magic numbers don’t cut it.

    timeold = millis();
    int time = (millis()/1000);
    int timedec = (millis()% 1000);
    rpmcount = 0;

You’ve got a shitload of slow stuff going on before you reset rpmcount. Hope that +/- 50% is good enough.

So, what is the problem with the code?