Converting analog readout to percentage

Patty0465 · April 16, 2021, 8:19pm

I dont seem to understand this
Trying to print to lcd in percentage's instead of 0 to 1023
My range is 200 to 1000
This is what I have but does not seem to work

/*
   
 * LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 5
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * LCD VSS pin to ground
 * LCD VCC pin to 5V
 * 10K resistor:
 * ends to +5V and ground
 * wiper to LCD VO pin (pin 3)
 
  Second Potentiometer connection with Arduino
 * Potentiometer 5v to Arduino 5v
 * Potentiometer GND to Arduino GND
 * Potentiometer Wiper/Vout to Arduino A0(Analog pin 0)
*/

// include the library code:
#include <LiquidCrystal.h>
int sensorValue = 0;
float value;
float percentage;


// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() 
{
  pinMode(A0, INPUT);
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  Serial.begin(9600);
}

void loop() 
{
  // read the input on analog pin 0:
  sensorValue = analogRead(A0);
   percentage =100-(value-0) /( 1023.0-0) * 100; 
  lcd.println(percentage);
  delay(700);
  // set the cursor to column 0, line 0:
  lcd.setCursor(0, 0);
  // print out the value at LCD Display:
  lcd.print("level ");
  lcd.print(percentage);
  // print out the value at Serial Monitor:
  Serial.println(sensorValue);
  delay(1000);
  lcd.clear();  
}

groundFungus · April 16, 2021, 8:24pm

Does using the map() function work?

percentage = map(sensorValue, 0, 1023, 200, 1000);

Patty0465 · April 16, 2021, 8:27pm

for some reason it displays 200 to 100 instead of 0 to 100

ToddL1962 · April 16, 2021, 8:34pm

percentage =100-(value-0) /( 1023.0-0) * 100;

This line doesn't make any sense to me. I don't see value getting set anywhere. Also, when you say the range is 200 to 1000 do you mean that you should only see analog values between 200 and 1000 or you need to convert the range 0 to 1023 to the range 200 to 1000?

shaell · April 16, 2021, 8:39pm

There are some mistakes in your code:

You declare value but you do not relate it with anything, so it is not used.
As percentage is not related to sensorValue but to value, it makes no sense when it is displayed on the LCD.
You should map sensorValue from 0 to 100 using sensorValue variable, like this: [code]percentage = map(sensorValue, 0, 1023, 0, 100);[/code]

missdrew · April 16, 2021, 8:39pm

percentage = map(sensorValue, 200, 1023, 0, 100);

Patty0465 · April 16, 2021, 8:49pm

I have to characters after.00 is that from my sketch

/*
   
 * LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 5
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * LCD VSS pin to ground
 * LCD VCC pin to 5V
 * 10K resistor:
 * ends to +5V and ground
 * wiper to LCD VO pin (pin 3)
 
  Second Potentiometer connection with Arduino
 * Potentiometer 5v to Arduino 5v
 * Potentiometer GND to Arduino GND
 * Potentiometer Wiper/Vout to Arduino A0(Analog pin 0)
*/

// include the library code:
#include <LiquidCrystal.h>
int sensorValue = 0;
float value;
float percentage;


// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() 
{
  pinMode(A0, INPUT);
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  Serial.begin(9600);
}

void loop() 
{
  // read the input on analog pin 0:
  sensorValue = analogRead(A0);
  percentage = map(sensorValue, 200, 1023, 0, 100);
  lcd.println(percentage);
  delay(500);
  // set the cursor to column 0, line 0:
  lcd.setCursor(0, 0);
  // print out the value at LCD Display:
  lcd.print("level ");
  lcd.print(percentage);
  // print out the value at Serial Monitor:
  Serial.println(sensorValue);
  delay(50);
  lcd.clear();  
}

shaell · April 16, 2021, 9:05pm

erase value, which you do not use and change int and float to byte.

Then change:
percentage = map(sensorValue, 200, 1023, 0, 100); to
percentage = map(sensorValue, 0, 1023, 0, 100);

Patty0465 · April 16, 2021, 9:09pm

Thanks but it reads from 0 to 24 and still have those strange charaters

/*
   
 * LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 5
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * LCD VSS pin to ground
 * LCD VCC pin to 5V
 * 10K resistor:
 * ends to +5V and ground
 * wiper to LCD VO pin (pin 3)
 
  Second Potentiometer connection with Arduino
 * Potentiometer 5v to Arduino 5v
 * Potentiometer GND to Arduino GND
 * Potentiometer Wiper/Vout to Arduino A0(Analog pin 0)
*/

// include the library code:
#include <LiquidCrystal.h>
byte sensorValue = 0;

byte percentage;


// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() 
{
  pinMode(A0, INPUT);
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  Serial.begin(9600);
}

void loop() 
{
  // read the input on analog pin 0:
  sensorValue = analogRead(A0);
  percentage = map(sensorValue, 0, 1023, 0, 100);
  lcd.println(percentage);
  delay(500);
  // set the cursor to column 0, line 0:
  lcd.setCursor(0, 0);
  // print out the value at LCD Display:
  
  lcd.print(percentage);
  // print out the value at Serial Monitor:
  Serial.println(sensorValue);
  delay(50);
  lcd.clear();  
}

groundFungus · April 16, 2021, 9:30pm

@missdrew, Iguess that I misunderstood the OP requirement.

The LiquidCrystal library does not support println, just print. Control the cursor with setCursor().

JCA34F · April 16, 2021, 11:26pm

Whoops, ignore me.

JCA34F · April 16, 2021, 11:45pm

Try:

percentage = 100 * (sensorValue - 200) / (1000 - 200.0);

Or better:

const int min = 200, max = 1000;
const float span = max - min, hundred = 100.0;
percentage = hundred * (sensorValue - min) / span;

Patty0465 · April 17, 2021, 1:38am

Thanks guys. The funny characters are gone from the end of the line but as I turn the potentiometer it goes from 0 to 24 (first half) then starts a 0 again to 24(for the second half)

/*
   
 * LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 5
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * LCD VSS pin to ground
 * LCD VCC pin to 5V
 * 10K resistor:
 * ends to +5V and ground
 * wiper to LCD VO pin (pin 3)
 
  Second Potentiometer connection with Arduino
 * Potentiometer 5v to Arduino 5v
 * Potentiometer GND to Arduino GND
 * Potentiometer Wiper/Vout to Arduino A0(Analog pin 0)
*/

// include the library code:
#include <LiquidCrystal.h>
byte sensorValue = 0;

byte percentage;


// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() 
{
  pinMode(A0, INPUT);
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  Serial.begin(9600);
}

void loop() 
{
  // read the input on analog pin 0:
  sensorValue = analogRead(A0);
const int min = 0, max = 1023;
const float span = max - min, hundred = 100.0;
percentage = hundred * (sensorValue - min) / span;
  lcd.print(percentage);
  delay(500);
  // set the cursor to column 0, line 0:
  lcd.setCursor(0, 0);
  // print out the value at LCD Display:
  
  lcd.print(percentage);
  // print out the value at Serial Monitor:
  Serial.println(sensorValue);
  delay(50);
  lcd.clear();  
}

JCA34F · April 17, 2021, 5:47am

Change:

To

float percentage;

hammy · April 17, 2021, 6:51am

As mentioned , Those characters are the carriage return/new line type stuff being printed to the display .

Change println to print.

Patty0465 · April 17, 2021, 1:22pm

Thats a no go jca34f the display only displays "inf"
If i turn the pot off it displays "nan"

/*
   
 * LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 5
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * LCD VSS pin to ground
 * LCD VCC pin to 5V
 * 10K resistor:
 * ends to +5V and ground
 * wiper to LCD VO pin (pin 3)
 
  Second Potentiometer connection with Arduino
 * Potentiometer 5v to Arduino 5v
 * Potentiometer GND to Arduino GND
 * Potentiometer Wiper/Vout to Arduino A0(Analog pin 0)
*/

// include the library code:
#include <LiquidCrystal.h>
float sensorValue = 0;
float percentage;
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() 
{
  pinMode(A0, INPUT);
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  Serial.begin(9600);
}

void loop() 
{
  // read the input on analog pin 0:
  sensorValue = analogRead(A0);
const int min = 0, max = 1023;
const float span = max - max, hundred = 100.0;
percentage = hundred * (sensorValue - min) / span;

  lcd.print(percentage);
  delay(500);
  // set the cursor to column 0, line 0:
  lcd.setCursor(0, 0);
  // print out the value at LCD Display:
  lcd.print(percentage);
  // print out the value at Serial Monitor:
  Serial.print(sensorValue);
  delay(50);
  lcd.clear();  
}

PieterP · April 17, 2021, 1:43pm

span = max - max

Oops ...

Patty0465 · April 17, 2021, 1:56pm

Thanks PieterP
Working now
Just one more question. How do I insert "level at" before the number

TomGeorge · April 17, 2021, 3:19pm

Hi,
Can you post your now working code please?

Thanks.. Tom..

Patty0465 · April 17, 2021, 3:24pm

Thanks guys got it working good.

/*
   
 * LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 5
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * LCD VSS pin to ground
 * LCD VCC pin to 5V
 * 10K resistor:
 * ends to +5V and ground
 * wiper to LCD VO pin (pin 3)
 
  Second Potentiometer connection with Arduino
 * Potentiometer 5v to Arduino 5v
 * Potentiometer GND to Arduino GND
 * Potentiometer Wiper/Vout to Arduino A0(Analog pin 0)
*/

// include the library code:
#include <LiquidCrystal.h>
float sensorValue = 0;
float percentage;

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() 
{
  pinMode(A0, INPUT);
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  Serial.begin(9600);
  lcd.print("Tank Level:");
}

void loop() 
{
  // read the input on analog pin 0:
  sensorValue = analogRead(A0);
const int min = 0, max = 1023;
const float span = max - min, hundred = 100.0;
percentage = hundred * (sensorValue - min) / span;
lcd.setCursor(0, 0);
lcd.print("Tank Level:");
lcd.setCursor(4,1);
  lcd.print(percentage);
  lcd.print("%");
  delay(2000);
 
// print out the value at Serial Monitor:
  Serial.print(sensorValue);
  delay(50);
  lcd.clear();  
}

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Converting analog readout to percentage

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