Display Potentiometer value as percentage

Using Arduino Programming Questions
1

Hello,

I'm controlling a dc motor speed by a potentiometer
I want to display the potentiometer value as percentage. Here's the code

I'm a beginner so go easy on me . :slight_smile:

// Arduino DC motor speed and direction control
 
#define button   8
#define pot      0
#define pwm1     9
#define pwm2    10

// include the library code:
#include <LiquidCrystal.h>

// initialize the library by associating any needed LCD interface pin
// with the arduino pin number it is connected to
const int rs = 7, en = 6, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs,en,d4,d5,d6,d7);

int potPin0 = A0;
int potPin1 = A2; 
boolean motor_dir = 0;
int motor_speed;
 
void setup() {
  pinMode(button, INPUT_PULLUP);
  pinMode(pwm1,   OUTPUT);
  pinMode(pwm2,   OUTPUT);

lcd.begin(16, 2);
lcd.clear();

pinMode(potPin0, INPUT);
pinMode(potPin0, INPUT);
}
 
void loop() {
 lcd.setCursor(0,0); // Sets the cursor to col 0 and row 0
lcd.print("Motor speed: "); // Prints Sensor Val: to LCD
lcd.print(analogRead(potPin0)); // Prints value on Potpin1 to LCD
lcd.setCursor(0,1); // Sets the cursor to col 1 and row 0
lcd.print("E-polytechnique "); // Prints Sensor Val: to LCD
lcd.print(analogRead(potPin1)); // Prints value on Potpin1 to LCD

  motor_speed = analogRead(pot) / 4;
  if(motor_dir)
    analogWrite(pwm1, motor_speed);
  else
    analogWrite(pwm2, motor_speed);
  if(!digitalRead(button)){                // If direction button is pressed
    while(!digitalRead(button));           // Wait until direction button released
    motor_dir = !motor_dir;                // Toggle direction variable
    if(motor_dir)
      digitalWrite(pwm2, 0);
    else
      digitalWrite(pwm1, 0);
  }
}
2 
lcd.print(analogRead((int)((potPin0)/1023.0)*100)); // Prints value on Potpin1 to LCD as percent
3

analogRead() will return a value between 0 and 1023

If I told you that it had just returned say 123, could you calculate that as a percentage of 1023 ?

If not, then I fear that programming is not for you

4

accountsays:
Hello,

I'm controlling a dc motor speed by a potentiometer
I want to display the potentiometer value as percentage. Here's the code

I'm a beginner so go easy on me . :slight_smile:

// Arduino DC motor speed and direction control

#define button   8
#define pot      0
#define pwm1     9
#define pwm2    10

// include the library code:
#include <LiquidCrystal.h>

// initialize the library by associating any needed LCD interface pin
// with the arduino pin number it is connected to
const int rs = 7, en = 6, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs,en,d4,d5,d6,d7);

int potPin0 = A0;
int potPin1 = A2;
boolean motor_dir = 0;
int motor_speed;

void setup() {
 pinMode(button, INPUT_PULLUP);
 pinMode(pwm1,   OUTPUT);
 pinMode(pwm2,   OUTPUT);

lcd.begin(16, 2);
lcd.clear();

pinMode(potPin0, INPUT);
pinMode(potPin0, INPUT);
}

void loop() {
lcd.setCursor(0,0); // Sets the cursor to col 0 and row 0
lcd.print("Motor speed: "); // Prints Sensor Val: to LCD
lcd.print(analogRead(potPin0)); // Prints value on Potpin1 to LCD
lcd.setCursor(0,1); // Sets the cursor to col 1 and row 0
lcd.print("E-polytechnique "); // Prints Sensor Val: to LCD
lcd.print(analogRead(potPin1)); // Prints value on Potpin1 to LCD

motor_speed = analogRead(pot) / 4;
 if(motor_dir)
   analogWrite(pwm1, motor_speed);
 else
   analogWrite(pwm2, motor_speed);
 if(!digitalRead(button)){                // If direction button is pressed
   while(!digitalRead(button));           // Wait until direction button released
   motor_dir = !motor_dir;                // Toggle direction variable
   if(motor_dir)
     digitalWrite(pwm2, 0);
   else
     digitalWrite(pwm1, 0);
 }
}

Welcome to the Arduino forum. I am not really sure what you want to do.

How do you have the potentiometer wired? Is it part of a voltage divider? What voltage do you have feeding the voltage divider? Which Arduino are you using?

The analog read will NOT give you a resistance value. The best it can do is give you a value from 0 to 1023. Which is based on the voltage applied to the analog pin. Depending on how you have the pot connected, you can actually have a smaller range of values, so percentage is of questionable use.

Paul

5

Thank you all for answering but it didn't change. the display still showing the potentiometer value

6

Post your new program that shows the problem

7

Hi, I've spent weeks trying to get the answer for this, and now that I have, I want to share the information for all those who will struggle in the future :smiley:

int potentiometerValue = analogRead(potentiometerPin);
int percent = map(potentiometerValue , 0, 1023, 0, 100);
Serial.println(percent);

Here's where I got the solution:
https://www.browncountylibrary.org/wp-content/uploads/2018/03/arduino_potentiometer.pdf

8

I've spent weeks trying to get the answer for this

If only you had asked here weeks ago ...

9

I always use the map function.

and never failed on me, This is the code that I use.

int oldVal;
int TOLERANCE= 5
      int val = analogRead(pot);
      val = map(val, 0, 1023, 0, 100);

      int diff = abs(val - oldVal);

      if (diff > TOLERANCE) )
      {
        Serial.print(val);
        Serial.println("%");
        oldVal = val;// only save if the val has changed enough to avoid slowly drifting
      }

it helped me a lot when I need a certain value that isn't jumping around.

aideax:
int potentiometerValue = analogRead(potentiometerPin);
int percent = map(potentiometerValue , 0, 1023, 0, 100);
Serial.println(percent);

Here's where I got the solution:
https://www.browncountylibrary.org/wp-content/uploads/2018/03/arduino_potentiometer.pdf