tsop4838 hangs at 5V


I'm trying to figure out what I'm doing wrong with the tsop4838 IR sensor. I assumed you can just connect the pins directly (1->analong in, 2->ground, 3->5v), but it seem to hang at 5v. I then tried with a 3v source which again hangs at that voltage. I then place a 100 ohms in front of 5v/3v which had no impact. Each of these attempts was with a different sensor to avoid reusing a damaged sensor. Keep in mind, in all these cases, no IR sources were pointed at it, just the ambient light of the room.

Is there something I'm not understanding about the tsop4838 sensor? Isn't Pin 1 to the left with the bump facing you? Shouldn't I be seeing little to nothing (~0V) with no IR source in a lit room?

Hi, I think you will find that the output is HIGH for NO SIGNAL. Fire a IR remote at it and see what happens.

Tom.... :)

Yep it’s active low.

'Scope shot atached shows it goes to 0 (yellow) in the presence of a 38kHz carrier (blue).

Edit: attached shot of datasheet.

38kHz 555 IR.jpg

tsop active low.JPG