Mobile Charging System

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

// Initialize the LCD
LiquidCrystal_I2C lcd(0x27, 20, 4);  // Set the I2C address of the LCD

// Pin definitions
const int relayPins[4] = { 2, 3, 4, 5 };   // Relay pins
const int buttonPins[4] = { 6, 7, 8, 9 };  // Button pins
const int buzzerPin = 10;                  // Buzzer pin
const int coinSlotPin = 11;                // Coin slot pin

// Timing variables
unsigned long relayEndTimes[4] = { 0, 0, 0, 0 };  // End time for each relay
const unsigned long chargeTimePerCoin = 120;      // 2 minutes per coin in seconds

int coinsInserted = 0;

unsigned long lastUpdateTime = 0;
const unsigned long updateInterval = 1000;  // Update every second

// Variables to store previous LCD values for comparison
int prevCoinsInserted = -1;
unsigned long prevRelayTimes[4] = { 0, 0, 0, 0 };

void setup() {
  // Set up the LCD
  lcd.init();
  lcd.backlight();

  // Set relay and button pins as output/input
  for (int i = 0; i < 4; i++) {
    pinMode(relayPins[i], OUTPUT);
    digitalWrite(relayPins[i], LOW);       // Ensure relays are off
    pinMode(buttonPins[i], INPUT_PULLUP);  // Buttons are active LOW
  }

  pinMode(buzzerPin, OUTPUT);
  pinMode(coinSlotPin, INPUT_PULLUP);  // Use internal pull-up resistor

  // Display initial message on the LCD
  lcd.setCursor(0, 0);
  lcd.print("E-Piso Charger");
  lcd.setCursor(0, 1);
  lcd.print("2 mins/PHP");
  lcd.setCursor(0, 2);
  lcd.print("1|00:00  2|00:00");
  lcd.setCursor(0, 3);
  lcd.print("3|00:00  4|00:00");
}

void loop() {
  // Check for coin insertion
  if (digitalRead(coinSlotPin) == LOW) {    // Coin detected
    delay(50);                              // Debounce
    if (digitalRead(coinSlotPin) == LOW) {  // Confirm coin detection
      coinsInserted++;
      tone(buzzerPin, 1000, 100);  // Beep the buzzer
      while (digitalRead(coinSlotPin) == LOW) {
        // Wait until the coin is removed
        delay(10);
      }
    }
    delay(500);  // Prevent double counting
  }

  // Check buttons for starting charging
  for (int i = 0; i < 4; i++) {
    if (digitalRead(buttonPins[i]) == LOW) {  // Button pressed
      delay(50);                              // Debounce
      if (digitalRead(buttonPins[i]) == LOW && coinsInserted > 0 && digitalRead(coinSlotPin) == HIGH) {
        startCharging(i);
        delay(300);  // Avoid multiple triggers
      }
    }
  }

  // Update relay timing
  for (int i = 0; i < 4; i++) {
    if (relayEndTimes[i] > 0 && millis() >= relayEndTimes[i]) {
      stopCharging(i);
      relayEndTimes[i] = 0;  // Reset the relay end time
    }
  }

  // Only update the LCD every second
  if (millis() - lastUpdateTime >= updateInterval) {
    updateLCD();
    lastUpdateTime = millis();
  }
}

void startCharging(int relay) {
  digitalWrite(relayPins[relay], HIGH);                                        // Turn on the relay
  relayEndTimes[relay] = millis() + coinsInserted * chargeTimePerCoin * 1000;  // Set the end time for the relay based on the number of coins inserted
  coinsInserted = 0;                                                           // Reset the coin count after starting the charging
}

void stopCharging(int relay) {
  digitalWrite(relayPins[relay], LOW);  // Turn off the relay
}

void updateLCD() {
  // Update only if values have changed
  if (coinsInserted != prevCoinsInserted) {
    lcd.setCursor(14, 1);
    lcd.print("C: ");
    lcd.print(coinsInserted);
    prevCoinsInserted = coinsInserted;
  }

  for (int i = 0; i < 4; i++) {
    unsigned long remainingTime = relayEndTimes[i] > 0 ? (relayEndTimes[i] - millis()) / 1000 : 0;
    if (remainingTime != prevRelayTimes[i]) {
      // Update relay time display
      int row = i < 2 ? 2 : 3;
      int col = i % 2 == 0 ? 0 : 11;
      lcd.setCursor(col, row);
      lcd.print(i + 1);
      lcd.print("|");
      lcd.print(formatTime(remainingTime));

      prevRelayTimes[i] = remainingTime;
    }
  }
}

String formatTime(unsigned long timeInSeconds) {
  unsigned long minutes = timeInSeconds / 60;
  unsigned long seconds = timeInSeconds % 60;
  char buffer[6];
  sprintf(buffer, "%02lu:%02lu", minutes, seconds);
  return String(buffer);
}