What is the best way to position a PIR sensor

I have one of these:

I have a staircase that looks like this (its not that nice):

So Im wondering where would be the best place to position the PIR:

  1. Above the staircase on the ceiling, facing down towards both segments of the staircase.
  2. On the wall over the landing

I read the plastic cap has these lenses that increase detection angle. So does it allow for motion detection all around, 180 degrees? In that case either setting would be good, right?

Thanks

stairs.jpg

Up to you where you want to put it. All you have to know is that the PIR doesn't detect anything directly towards/away from it. Only sideways movements are detected. The warm object (you) has to move between the facets of the fresnel lens. PIR sensors are cheap, so you could use more than one. They might also take a second or so to react, depending one the sensitivity setting (sensitivity != range). Leo..

Ok I was indeed wondering about that. So then positioning it on the wall of the landing wouldn't be effective because I'm a sense people coming up or going down are moving towards and away from the landing wall.

On the other hand above would be best because the warm body is crossing it's path in either direction.

Thanks