Coin Acceptor Money Amount

Projects Programming
1

Hi, I am making a vending machine for a school project and I am using a coin acceptor I bought from e-Bay for the money aspect of the machine. I want it to accept a specific amount of money and then the person can choose their snack with a keypad. The problem is that when the amount of money reaches the "target amount" it would need to go over the amount so it would activate the next event. I feel like it is the floats but I just have no idea. Thank you in advance.

Here the relevant part of my code(If anyone needs the full code I can post that too):

#include <LiquidCrystal_I2C.h>
#include <Wire.h>

LiquidCrystal_I2C lcd(0x3F, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);

// Constants
const int coinpin = 2;
const int ledpin = 3;
const float targetcents = 1.00;

// Variables
volatile float cents = 0.00;
int credits = 0;

// Setup
void setup() {
  
  Serial.begin(9600);
  lcd.begin(16,2);
  lcd.backlight();
  pinMode(coinpin, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(coinpin), coinInterrupt, RISING);
  pinMode(ledpin, OUTPUT);
  
}

// Main loop
void loop() {
  
  // If we've hit our target amount of coins, increment our credits and reset the cents counter
  if (cents >= targetcents) {
    credits = credits + 1;
    cents = cents - targetcents;
  }

  // If we haven't reached our target, keep waiting...
  else {
  }

  // Debugging zone
  Serial.println(cents);
  lcd.setCursor(0,0);
  lcd.print("Insert Coin");
  lcd.setCursor(0, 1);
  lcd.print(cents);


  while (credits > 0) {
    lcd.setCursor(0,0);
    lcd.print("Select Snack:");
    delay(2500);
    break;
  }
  
}

// Interrupt
void coinInterrupt(){
  
  // Each time a pulse is sent from the coin acceptor, interrupt main loop to add 1 cent and flip on the LED
  cents = cents + 0.01;
  
}

P.S. I am pretty sure it is the code as it would not be the wiring and that is why I didn't post any pictures and schematics of the wiring. But I can post it if we need it to fix the problem.

2

A much better approach is to change all your currency variables into ints and treat your money like pennies rather than dollars. E.g. target = 100 (pennies), each interrupt increments 1 (penny), etc.

3

blh64:
A much better approach is to change all your currency variables into ints and treat your money like pennies rather than dollars. E.g. target = 100 (pennies), each interrupt increments 1 (penny), etc.

Ok thank and do you know how to make it show like cents (ex. $0.25) instead of just 25?

4

When you display it, that is the time to convert it to a float and divide by 100.

Serial.print( cents / 100.0, 2 );
lcd.print( cents / 100.0, 2 );
5

blh64:
When you display it, that is the time to convert it to a float and divide by 100.

Serial.print( cents / 100.0, 2 );

lcd.print( cents / 100.0, 2 );

Thank you so much