Newbie here, trying to figure out correct way to setup numbers

Projects Programming
1

I am new to Arduino (and the looping structure of it) and am writing a program that tracks beers poured from a keg. I am having trouble logically thinking about the setup of the variables/code though.

There is going to be a toggle switch determining what size keg we are using- a half keg or a pony keg. From here, we know the total ounces in the keg so we can figure out how many ounces remain which will be displayed on a screen.

The problem is I am unsure how to set the ouncesRemaining or kegSize without it being overwritten constantly when the program runs. If I were to hard code something like int ouncesRemaining = 661 at the beginning of the program outside of the loop, it would be easy. But I need to offer the user a choice of keg size with a physical switch and am unsure what to do to only set the number at the beginning of the program and not constantly reset it.

I have an idea to get around it but I'm unsure if this is the best way to do it. Since I am learning I am looking to see if there is a better/easier/correct way to do this type of thing.

This is not the exact code but simplified to show the idea:

int buttonPin=2;
int buttonState=0;
int i = 0;
int kegSize;
int ouncesRemaining;
int maxPony = 661;      
int maxHalf = 1984;   
float kegRemaining = 100;

void setup() {
pinMode(buttonPin, INPUT);
}

void loop() {

buttonState = digitalRead(buttonPin);
if (buttonState == LOW){ //LOW = keg is a Pony keg
  ouncesRemaining=maxPony;
  kegSize=maxPony;
  //alreadyRan == 1
}
else if (buttonState = HIGH){ //HIGH = keg is a Half barrel keg
  ouncesRemaining=maxHalf;
  kegSize=maxHalf;
}



while (i != 10){  //Not the real condition that happens in program
  ouncesRemaining=(ouncesRemaining - 1);
  i++;
  delay(1000);
}

kegRemaining=((float)ouncesRemaining/kegSize * 100); //Print this to LCD display

}

Here is my idea to fix/get around my issue. I add a variable to make sure the 'program setup' only runs once at the beginning of the program:

int buttonPin=2;
int buttonState=0;
int i = 0;
int kegSize;
int ouncesRemaining;
int maxPony = 661;      
int maxHalf = 1984;   
float kegRemaining = 100;
int programSetup = 0;

void setup() {
pinMode(buttonPin, INPUT);
}

void loop() {


if (programSetup == 0) {

buttonState = digitalRead(buttonPin);
if (buttonState == LOW){ //LOW = keg is a Pony keg
  ouncesRemaining=maxPony;
  kegSize=maxPony;
  //alreadyRan == 1
}
else if (buttonState = HIGH){ //HIGH = keg is a Half barrel keg
  ouncesRemaining=maxHalf;
  kegSize=maxHalf;
}
}

while (i != 10){  //Not the real condition that happens in program
  ouncesRemaining=(ouncesRemaining - 1);
  i++;
  delay(1000);
}

kegRemaining=((float)ouncesRemaining/kegSize * 100); //Print this to LCD display

}
2

You don't need to create your own programSetup check, you just put the code into the setup() method instead :slight_smile:

3

Not sure I understand completely, but if you have two kegs of different sizes, and the size can be changed on the fly with a toggle switch, and you want to track the amount in each keg, then you will need two "ouncesRemaining" variables. This is exactly what arrays are for.

e.g.,


int ouncesRemaining[2] = {661 /* pony */, 1984 /* half */};
...
void loop()
{
  if (buttonState)
  {
    ouncesRemaining[0]--;
  }
  else
  {
    ouncesRemaining[1]--;
  }
}
4

Oof. Duh. Thank you so much. Sometimes it's the simplest of things that you look over. Thanks again

5

This is interesting. In this use case the change only has to be noted when the program is started but an array probably is the answer to make things smoother. Thank you I'll look into this also.

6

Add another button that has the functionality of "reset counter to new and full keg"

then you do two steps

  1. turn switch for the keg-size into the correct position for the new keg.
  2. then press button with function "reset counter to new and full keg"

Your code checks for the button "reset counter to new and full keg" and only in case this button is pressed do

if (buttonState == LOW){ //LOW = keg is a Pony keg
  ouncesRemaining=maxPony;
  kegSize=maxPony;
  //alreadyRan == 1
}
else if (buttonState = HIGH){ //HIGH = keg is a Half barrel keg
  ouncesRemaining=maxHalf;
  kegSize=maxHalf;
}

best regards Stefan

7

In that case the ternary operator is your friend:

int ouncesRemaining = -1;

void setup()
{
   ouncesRemaining = digitalRead(buttonPin) ? 661 : 1984;
}