IR detector question

Hello-
Some IR transistors come with 2 leads, some with 3.
How do I hook up the 3rd lead (which I assume is the base) in this case?

If I want to shine the IR transmitter/LED continuously and send a signal when I disrupt the beam, is that OK?
I am reading lots of stuff about 38kHz frequencies being needed.
I am not building a TV remote, just a circuit that sends a signal when the beam is interrupted.
Thank you,
Nora

By "looking" for a frequency, intelligence, you can avoid false triggering from ambient sources. [That's not just sunlight or something, it's my favourite frequency.]
38kHz detectors (for remotes) don't make great beam-break detectors as there's a timing issue. Not that that cannot be overcome, it's just a complication.

38kHz detectors (for remotes) don't make great beam-break detectors as there's a timing issue.

You can use the TSOP4038 they are designed to do exactly what you want.

You can use the TSOP4038 they are designed to do exactly what you want.

"It can receive continuous 38 kHz signals or 38 kHz bursts." [datasheet]

They tweaked it for "light barrier" applications. 70ยข at mouser.com
Good to know.

hey i think you are looking for tsop....
arduinoguides.blogspot.com

check it out