1. Reflectance Sensors
TYWu

2. Photo Interrupter
ON1120
ON1120 is a photocoupler in which a high efficiency GaAs infrared light emitting diode is used as the light emitting element, and a high sensitivity phototransistor is used as the light detecting element.
The two elements are arranged so as to face each other, and objects passing between them are detected.

3. Photo Interrupter
Features
Fast response : tr, tf = 6 μs (typ.)

4. Photo Interrupter
Package Dimension and Circuit
Mark
Label
Bottom View

5. OS25B10
Application Circuit and Waveforms

6. OS25B10
Application
Tape-end sensors
Edge sensors

7. My Experiment
Placement a1
GND
Arduino
Pin 2
GND
5V or 3.3V
Necessary

8. Discussion
GaAs infrared light emitting diode is easy to be destroyed by high voltage!

9. Arduino Code int sensorPin = 2; boolean sensorState = false;
void setup() {
Serial.begin(9600);
pinMode(sensorPin, INPUT);
digitalWrite(sensorPin, HIGH); // Pull High }

10. Arduino Code (Cont’d) void loop() {
if((digitalRead(sensorPin) == LOW) && !sensorState) {
sensorState = true;
Serial.println("Object Gone"); }
else if((digitalRead(sensorPin) == HIGH) && sensorState) {
sensorState = false;
Serial.println("Object Present");

11. Execution
Snapshot

12. Photo Reflective Sensor
This is a reflective sensor combines a GaA1As infrared light emitting diode with a high sensitive Darlington phototransistor in a mini package.

13. Photo Reflective Sensor
Package Dimension and Circuit

14. Photo Reflective Sensor
Applications
Edge sensors
Level sensors of liquid

15. QTR-1A Reflectance Sensor
Sold by Pololu

16. QTR-1A Reflectance Sensor
Function