Log Potentiometer: specific ranges

Projects General Guidance
1

Hi! Hope i can find some help for my project. Basically I'm matching the movement of a log potentiometer (slider) to the change of led on a led strip using specific values. But the problem seems to be that when at the "extermes" of the potentiometer, so moving from first to second and from second-last to last, there might be little jumps. So I'm asking if anyone can help me fixing this little problem. I'm also attaching the code part regarding the ranges, if needed.

Thanks in advance!

int mapToRange(int value) {
       if (value >= 0   && value <= 26)   return 0;
  else if (value >= 27  && value < 53)   return 1;
  else if (value >= 53  && value < 285)  return 2;
  else if (value >= 285 && value < 530)  return 3;
  else if (value >= 530 && value < 780)  return 4;
  else if (value >= 780 && value < 970)  return 5;
  else if (value >= 970 && value <= 998) return 6;
  else if (value >= 999) return 7;
}
2

What about just averaging a number of readings ?
There's a few other schemes too, which I've tried, but this is light-weight and easy to understand. It's quite reusable in different sketches because you can adjust the number of readings and delays to suit other timing requirements.

int   i;            // used in for loops
float        Sensor_Average;
const int    Sensor_Readings    = 10;    // number of repeated sensor readings to average, maximum 30
const int    Sensor_Delay       = 5;     // ms delay between repeated sensor readings

void setup()
{
}    // end void setup

void loop()
{
    Value = Get_Sensor_Val(Pot_Pin);
    // now call your mapToRange here
}    // end void loop

int Get_Sensor_Val(byte Sensor_Pin)
{
    // Arithmetic average
    Sensor_Average = 0;
    for (i = 1; i <= Sensor_Readings; i++)
    {
        Sensor_Average += analogRead(Sensor_Pin);
        delay(Sensor_Delay);
    }
    Sensor_Average = Sensor_Average / float(Sensor_Readings);
    return int(Sensor_Average + 0.5);
}    // end void Get_Sensor_Val
1 Like
3

If you really mean a LOG potentiometer (A taper), you could create a lookup array or formula to flatten out the curve, or simply replace it with a LINEAR (B taper) pot.

4

Why do you think that?

6

Please read this thread on handling a potentiometer and mapping it to a small number of output values.

HTH

a7

1 Like
7

i wrote might because it's not a frequent error, it might happen after a while using it or in some moments

8

Then there must be something else wrong in your code somewhere else.

9

maybe something interfering?

10

Very possible.

11

The contacts in the pot may be a bit dirty, and occasionally give you a bad reading.

Are you using any other analog inputs? Alternating between analog inputs might cause errors in the reading, a common technique is to read the analog input twice, ignoring the first reading.

Incidentally, your code can be written in a much simpler way, since an "else if" statement will never be reached if the previous if condition is true.


int mapToRange(int value) {
  if (value < 27)   return 0;
  else if (value < 53)   return 1;
  else if (value < 285)  return 2;
  else if (value < 530)  return 3;
  else if (value < 780)  return 4;
  else if (value < 970)  return 5;
  else if (value < 990) return 6;
  else return 7;
}
1 Like
12

ok I'll revise it all, thanks!

13

Thanks to all! I'll try the different solutions. You were all very helpful :slight_smile:

14

That means it can even be

int mapToRange(int value) {
  if (value < 27)   return 0;
  if (value < 53)   return 1;
  if (value < 285)  return 2;
  if (value < 530)  return 3;
  if (value < 780)  return 4;
  if (value < 970)  return 5;
  if (value < 990) return 6;
  return 7;
}
2 Likes
15

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