Calculation gives wrong value (solved)

Projects Programming
1

Hi All,

I'm trying to read potentiometer values and to use millis() for no blocking delay. Everything works fine until potentiometer value goes over ~305.

Can anybody please help me figure out what is the problem that suddenly calculation result gets wrong when potentiometer value reaches certain level.

Code:

unsigned long time_now = 0;

int potValue = 0;

void setup() {

 Serial.begin(9600);

}

void loop() {

 potValue = analogRead(A2);

 if(millis() > time_now + (100 * potValue)){
     time_now = millis();
             Serial.println("..................");
             Serial.println(time_now);
             Serial.println(potValue);
             Serial.println(time_now + (100 * potValue));
             Serial.println("..................");
 }
}

Results:

..................
14557
68
21357
..................
..................
21372
68
28172
..................
..................
38962
175
56462
..................
..................
69329
303
99629
..................
..................
71432
328
38696
..................
..................
71434
328
38698
..................
2

You need to change the variable potValue to unsigned long. The maximum value for an int is 32767, after that it immediately goes to -32768

A simple rule is always use unsigned long for variables that work with millis()

...R

3



Aka, read How to use the forum and edit your post to use code tags please :wink:

And you're barking up the wrong three :wink: Nothing to do with millis().

Try adding

Serial.println(100 * potValue);

and see if that rings a bell :slight_smile:

Robin2, spoilers :stuck_out_tongue: Or simpler (and in my opinion more sensible), use 100UL instead of 100.

4

Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html . Then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks.. Tom.. :slight_smile:

5

I forgot about int maximum value and I also edited my post to be more readable.

Thank you all!