Lite-On LTH-1550 Reflective Photointerruptor¶
This part combines an infrared LED side-by-side with a NPN phototransistor. When no object is present in front of the sensor, the infrared light dissipates and the transistor stays off. When an object is close (but not touching), it can reflect light into the phototransistor so it can turn on.
Lite-On LTH-1550-01
Jameco 2202378, PHOTOINTERRUPTER,REFLECTIVE, NPN PHOTOTRANSISTOR,940/PTR
datasheet: https://www.jameco.com/Jameco/Products/ProdDS/2202378LiteON.pdf
In typical use, the part needs two resistors, one to limit the LED current and the other to form a voltage divider with the phototransistor. Typical values for 5V operation are 220 Ohms for the LED ballast and 22K for the phototransistor bias.