Please help a complete newbie

Projects General Guidance
1

Hello All! I am completely new to electronics and programming. I am thoroughly loving learning about this stuff. And I feel like I have learned a lot in a short time. I have however run into a situation I cannot figure out on my own, and my googling has not helped. I have written the code below that will read the position of a potentiometer and report it on the lcd as a percentage and also let the potentiometer control a fan. This lets me see what percentage of power the fan is running off of. I know its simple but I feel extremely happy about being able to figure just that all out haha. My problem is that after I go all the way up to 100% and turn back down, it will show percent signs where numbers used to be. ie. 2%%% when it was 100%. Could someone point me in the right direction on how to fix this?

Thanks for any help!

Here's the code.

#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
 LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
 
 int tipcontrolPin = 9; // TIP 120 pin controlling fan speed
 int potcontrolPin = A0; // Reads Potentiometer posistion
 int potval; // Value of potentiometer
 int lcdpercentageVal; // Fan speed percentage converted from raw to percentage format
 int fanspeedVal; // Value to control fan speed
 
 void setup()
 {
   lcd.begin(16,2);
   lcd.print("Fan Sketch Test");
   delay(5000);
   lcd.clear();
   pinMode(tipcontrolPin, OUTPUT);
 }
 
 void loop()
 {
   {
   potval = analogRead(potcontrolPin);
   lcdpercentageVal = map(potval, 0, 1024, 0, 101);
   lcd.setCursor(0,0);
   lcd.print("Fan Speed");
   lcd.setCursor(0,1);
   lcd.print(lcdpercentageVal);
   lcd.print("%");
   }
   
   {
   fanspeedVal = map(potval, 0, 1024, 0, 255);
   analogWrite(tipcontrolPin, fanspeedVal);
   }
   
   delay(100);
 }
2

You could always print spaces after your string, or you could insert leading spaces, depending on the value you're about to print.

3

Or clear the line before you print to it'

void lcdClearLine (byte line) {
   lcd.setCursor(0,line);
   lcd.print("                      "; // number of spaces as char width
   lcc.setCursor(0,line);
}
4

Look into sprintf. You probably want to do something like
In the global variables:
char[30] s; //Character utility buffer

for the LCD print:
sprintf(s, "% 3d%%", lcdpercentageVal);
lcd.print(s);

'% 3d' => substitute a decimal integer in here, up to 3 digits, leading with spaces for zeros.
'%%' => Percent sign

5

Thanks everyone that helps a lot!