Change max and min read value of potentiometer

Question

I'd like to know if there is a function or some way to define min and max value to potentiometer, for example: I'm using a mechanical part that only tour the potentiometer a little bit, what means the potentiometer doesn't start in the beginning and doesn't finish in the end. So, how can I make this space the potentiometer tour means 0 to 255 the start to end, respectively?

Answer 1

You cannot declare that the min and max values of a potentiometer are x and y. What you can do is map() the values of the potentiometer to your own desired scale.

To do this, you'll have to get the following values:

• Minimum value of the potentiometer, pMin
• Maximum value of the potentiometer, pMax

But these values aren't what you want. For example, what you want is pmin to be 0 and pMax to be 100. So, you'll have to scale pMin and pMax to those values.

For this, you use the map() function. What map() does is changing the value in a given scale, to that of another scale. Let's get some example code:

int pMin = 14; //the lowest value that comes out of the potentiometer
int pMax = 948; //the highest value that comes out of the potentiometer.
int x = 0; //we will use this value to store the readings of the potentiometer
void setup(){
 Serial.begin(9600); //Serial monitor can be used to check the values
}
void loop(){
 x = analogRead(A0); //connect the potentiometer to the A0 pin of the Arduino
 Serial.print(x); //prints the original reading
 x = map(x, pMin, pMax, 0, 100) //take the value of x, compared it to the scale of the potentiometer pMin to pMax, and translate that value to the scale of 0 to 100
 Serial.print("\t"); //a tab to make the reading more easy
 Serial.println(x); //post mapped value, println is a linebreak as well
 delay(100); //so we don't post to much in the serial and you can read data better.
}

With this example you can clearly see how your potentiometer behaves and how you can use the 'weird' values from its readings in a useful way for your projects.

• Dampmaskin: You can even make it auto-calibrating. In the loop, if (x > pMax) { pmax = x ), and vice versa for pMin. But then the user would have to twiddle the pot every time the device starts, unless you save the min and max to eeprom.

Answer 2

Either use a reference voltage closer to the maximum voltage the potentiometer is capable of, or use map() to map the existing limited range to a larger range. Note that using map() will not improve precision.

Answer 3

If the values from the pot are 0 - 1023 you can divide the number by 4 which would give you a closer range to what you need. The map() function can be used instead.