#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 10, 9, 8, 7);
int upButton = 3;
int downButton = 4;
int selectButton = 5;
int voltagePin = A0;

float batteryVoltage = 0;
float lowVoltage = 0;
float highVoltage = 0;
int state = 0;
int LED = A1;

void setup() {
  pinMode(upButton, INPUT);
  pinMode(downButton, INPUT);
  pinMode(selectButton, INPUT);
  pinMode(LED, OUTPUT);
  lcd.begin(16, 2);
  lowVoltage = 0;
  highVoltage = 0;
}

void loop() {
  batteryVoltage = analogRead(voltagePin) * (24.0 / 1023.0); // voltage divider

  if (digitalRead(selectButton) == HIGH) {
    state = (state + 1) % 3;
    delay(200);
  }

  if (state == 0) {
    lcd.clear();
    lcd.print("Battery Voltage:");
    lcd.setCursor(0, 1);
    lcd.print(batteryVoltage);
  delay(500);
  } else if (state == 1) {
    if ((digitalRead(upButton) == HIGH)&&( lowVoltage < 24.50)) {
      lowVoltage += 0.5;
      delay(200);
    }
    if ((digitalRead(downButton) == HIGH)&&( lowVoltage > 0.00)) {
      lowVoltage -= 0.5;
      delay(200);
    }
    lcd.clear();
    lcd.print("Low Voltage:");
    lcd.setCursor(0, 1);
    lcd.print(lowVoltage);
  } else if (state == 2) {
    if ((digitalRead(upButton) == HIGH)&&( highVoltage < 24.50)) {
      highVoltage += 0.5;
      delay(200);
     
    }
    if ((digitalRead(downButton) == HIGH)&&( highVoltage > 0.00)) {
      highVoltage -= 0.5;
      delay(200);
    }
    lcd.clear();
    lcd.print("High Voltage:");
    lcd.setCursor(0, 1);
    lcd.print(highVoltage);
  }
  if(batteryVoltage <  lowVoltage)
{
  digitalWrite(LED, HIGH);
}
else if(batteryVoltage > highVoltage)
{
  digitalWrite(LED, LOW);
}
}