PT333B 5mm Infrared Photo Transistor

Finally a photo transistor that actually blocks ambient light properly—the dark blue casing makes a real difference in my indoor projects. Sensitive enough to trigger from a standard IR LED across the room.

I needed a sensor that wouldn't pick up ambient room lights, and the dark blue package on these does exactly that — they only trigger on my IR remote. Worked perfectly for my line-following robot project.

The dark blue casing does a decent job filtering out ambient light, but the sensitivity seems a bit inconsistent compared to other NPN transistors I've used. It works fine for basic proximity sensing indoors.