Use IR photodiodes to measure levels 1-5.

pelletmeter.ino

int power = A5; // This is the power side of our photodiodes. The other side is plugged into the "photoresistor" pin (above).
int lowout = A4;
int led = D0; // This is where your LED is plugged in. The other side goes to a resistor connected to GND.
int boardLed = D7; // This is the LED that is already on your device.

int read1 = D1;
int read2 = D2;
int read3 = D3;
int read4 = D4;
int read5 = D5;

int meter1;
int meter2;
int meter3;
int meter4;
int meter5;

int dht = D6;

int gauge;


void setup() {
  pinMode(led,OUTPUT); // Our LED pin is output (lighting up the LED)
  pinMode(boardLed,OUTPUT); // Our on-board LED is output as well

  pinMode(power,OUTPUT); // The pin powering the photoresistor is output (sending out consistent power)
  pinMode(lowout, OUTPUT);
  
  digitalWrite(power,HIGH);
  digitalWrite(lowout, LOW);

  pinMode(read1, INPUT_PULLDOWN);
  pinMode(read2, INPUT_PULLDOWN);
  pinMode(read3, INPUT_PULLDOWN);
  pinMode(read4, INPUT_PULLDOWN);
  pinMode(read5, INPUT_PULLDOWN);
  
}

void loop() {

  gauge = 0;
  
  if (digitalRead(read1) == HIGH) { gauge += 1; meter1 = 1; }
  else { meter1 = 0; }
  
  if (digitalRead(read2) == HIGH) { gauge += 1; meter2 = 1; }
  else { meter2 = 0; }
  
  if (digitalRead(read3) == HIGH) { gauge += 1; meter3 = 1; }
  else { meter3 = 0; }
  
  if (digitalRead(read4) == HIGH) { gauge += 1; meter4 = 1; }
  else { meter4 = 0; }
  
  if (digitalRead(read5) == HIGH) { gauge += 1; meter5 = 1; }
  else { meter5 = 0; }
  
  Particle.variable("pelletmeter1", meter1);
  Particle.variable("pelletmeter2", meter2);
  Particle.variable("pelletmeter3", meter3);
  Particle.variable("pelletmeter4", meter4);
  Particle.variable("pelletmeter5", meter5);
  Particle.variable("gauge",gauge);

  Particle.publish("percentage", String(gauge/5.0));
  
  delay(2000);
  if (gauge <= 2) { 
      Particle.publish("fillhopper", "1");
      digitalWrite(boardLed, HIGH);
  } else {
      Particle.publish("fillhopper", "0");
      digitalWrite(boardLed, LOW);
  }

}