I recently bought this (http://www.ebay.com/itm/291302426564?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
and I wanted to set it up. All over internet, there were only ones with analog pins, even if there was a digital pin in their tutorial, they didnt use it. Any ideas how to use it?
Educated guess.
Digital output.
Pot sets the threshold.
Leo..
Yes, the description clearly says it has a comparator output.
Well, that means? I tried to connect it like just d0 to digital 2 and use it as a button but it doesn work, it shines all the time...
Hi,
Hi, what is your electronics, programming, arduino, hardware experience?
Tom.... 
michalas:
...it shines all the time...
What does that mean. The output LED?
Did you try to cover the IR LED, or adjust the trimpot.
Post a circuit diagram of the module.
If you can't find it, draw it yourself.
It's not that uncommon having to reverse-engineer things like that to know how they work.
Leo..