int analogPin = A0;
int led_1 = 3;
int led_2 = 6;
int led_3 = 9;
float val = 0;
float voltage;
int brightness = 0;
void setup() {
  // put your setup code here, to run once:
  pinMode(led_1, OUTPUT);
  pinMode(led_2, OUTPUT);
  pinMode(led_3, OUTPUT);
  Serial.begin(9600);

}

void loop() {
  // put your main code here, to run repeatedly:
  val = analogRead(analogPin);
  voltage = val * 5 / 1023;
  Serial.println(voltage);
  if (voltage < 1.25) {
    digitalWrite(led_1, HIGH);
    digitalWrite(led_2, HIGH);
    digitalWrite(led_3, HIGH);
  }
  else if (voltage >= 1.25 and voltage < 2.5) {
    digitalWrite(led_1, HIGH);
    digitalWrite(led_2, HIGH);
    digitalWrite(led_3, LOW);
  }
  else if ( 2.5 <= voltage and voltage < 3.75) {
    digitalWrite(led_1, HIGH);
    digitalWrite(led_2, LOW);
    digitalWrite(led_3, LOW);
  }
  else {
    digitalWrite(led_1, LOW);
    digitalWrite(led_2, LOW);
    digitalWrite(led_3, LOW);
  }
}