Can negative number in delay function?

Using Arduino Programming Questions
1

I found from a site. I have a question regarding to programming.. I am wondering what happened more than 151 negative number of distance? if 150 - 151(151 is convert distance number) will be negative 1. because it said delay(150 - distance); , so will it work if delay(-1) function?

here example code...

void buzzer(){

if (distance>1){

if(distance>100){ // continuous sound if the obstacle is too close

digitalWrite(11,HIGH);

}

else{ // beeps faster when an obstacle approaches

digitalWrite(11,HIGH);

delay(150-distance); // adjust this value for your convenience

digitalWrite(11,LOW);

delay(150-distance); // adjust this value for your convenience

}

}

else{ // off if there is no obstacle
digitalWrite(11,LOW);
}
}
2

The parameter to delay is unsigned long. Unsigned means it can't be negative. If you try to put -1 in there, it will be read as 4,294,967,295

So delay(-1) really means delay(4,294,967,295). I doubt that's what you want.

3

It certainly won't work as noted above. You'll get an exceptionally long delay, so why not just constrain the distance value to prevent negative delays?

4

You mean you can't reverse time by using a negative delay. Pity.... That would be so useful.... :slight_smile:

Regards,
Ray L.