Auto Battery Charger Switch

#include <Wire.h>
#include <LiquidCrystal.h>

LiquidCrystal lcd(8, 9, 4, 5, 6, 7);

// define some values used by the panel and buttons
int lcd_key     = 0;
int adc_key_in  = 0;
#define btnRIGHT  0
#define btnUP     1
#define btnDOWN   2
#define btnLEFT   3
#define btnSELECT 4
#define btnNONE   5

// read the buttons
int read_LCD_buttons()
{
 adc_key_in = analogRead(0);      // read the value from the sensor 
 // my buttons when read are centered at these valies: 0, 144, 329, 504, 741
 // we add approx 50 to those values and check to see if we are close
 if (adc_key_in > 1000) return btnNONE; // We make this the 1st option for speed reasons since it will be the most likely result
 // For V1.1 us this threshold
 if (adc_key_in < 50)   return btnRIGHT;  
 if (adc_key_in < 250)  return btnUP; 
 if (adc_key_in < 450)  return btnDOWN; 
 if (adc_key_in < 650)  return btnLEFT; 
 if (adc_key_in < 850)  return btnSELECT;  


 return btnNONE;  // when all others fail, return this...
}

//Charger state on/off
int chargerstate = 0;
float chargertarget = 13.6;
#define ChargerRelay 0
int ChargerRelayState =0;

// number of analog samples to take per reading
#define NUM_SAMPLES 20

int sum = 0;                    // sum of samples taken
unsigned char sample_count = 0; // current sample number
float voltage = 0.0;            // calculated voltage

void setup()
{
    lcd.begin(16, 2);              // start the library
    lcd.setCursor(0,0);
    lcd.print("Voltage:"); // print a simple message
    pinMode(ChargerRelay, OUTPUT);
    
}

void loop()
{
    // take a number of analog samples and add them up
    while (sample_count < NUM_SAMPLES) {
        sum += analogRead(A5);
        sample_count++;
        delay(10);
    }
    // calculate the voltage
    // use 5.0 for a 5.0V ADC reference voltage
    // 5.015V is the calibrated reference voltage
    voltage = ((float)sum / (float)NUM_SAMPLES * 5.015) / 1024.0;
    // send voltage for display on Serial Monitor
    // voltage multiplied by 5 when using voltage divider that
    // divides by 5. 4.96 is the calibrated voltage divide
    // value
    lcd.setCursor(8,0);
    lcd.print(voltage * 4.85);
    lcd.print ("V");
    lcd.setCursor(12,1);
    lcd.print(chargertarget);
    lcd.print("V");
    sample_count = 0;
    sum = 0;

    if ((voltage * 4.85) <= 12.20) {
      chargerstate = 1;
      digitalWrite(ChargerRelay, HIGH);
    } else if ((voltage * 4.85) >= chargertarget) {
      chargerstate = 0;
      digitalWrite(ChargerRelay, LOW);
    }
    
    lcd.setCursor(0,1);
    lcd.print("Charger:");
    
    if (chargerstate == 0) {
      lcd.setCursor(8,1);
      lcd.print("OFF");
    } else {
      lcd.setCursor(8,1);
      lcd.print("ON ");
    }

    lcd_key = read_LCD_buttons();  // read the buttons
    switch (lcd_key)               // depending on which button was pushed, we perform an action
 {
   case btnRIGHT:
     {
     chargertarget ++;
     break;
     }
   case btnLEFT:
     {
     chargertarget --;
     break;
     }
   case btnUP:
     {
     chargerstate = 1;
     digitalWrite(ChargerRelay, HIGH);
     break;
     }
   case btnDOWN:
     {
     chargerstate = 0;
     digitalWrite(ChargerRelay, LOW);
     break;
     }
   case btnSELECT:
     {
     //lcd.print("SELECT");
     break;
     }
     case btnNONE:
     {
     //lcd.print("NONE  ");
     break;
     }
 }
    
}