Photo Interrupter

I bought 10 photo interrupters, thinking I might need them to zero stepping motor positions.

uxcell 10 Pcs 1/8 inches Slot PCB Photo Interrupter Slotted Optical Sensor Switch HY860N (No longer available)

 
#define PI_LED 4
 
int detectorVal = 0;
 
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(PI_LED, OUTPUT);
  digitalWrite(PI_LED, HIGH);
}
 
void loop() {
  // put your main code here, to run repeatedly:
 
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(500);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(500);                       // wait for a second
  detectorVal = analogRead(A0);
  Serial.println(detectorVal);
 
}