SmartSense Motion Sensor Range

I just getting started with SmartThings and am pretty excited about it. I am thinking about using a SmartSense Motion Sensor to watch a window and a hole the wall for a through wall AC in my kids room and set off an alarm if there is movement. However I want to position it in a way that it will not go off if we walk into the room or turn on the light to check on him. I have looked around and cant seem to find a range or the “cone” that it will detect. I would prefer not to have to change from away to home mode every time we wanted to go in there.


It all depends on the exact positioning. I use one as a touchless switch–it is inside a bento box, sitting on a bookshelf, facing up, and it will not go off if someone just walks past. You have to wave a hand over it to trigger it. But we intentionally set it up with a very limited trigger area.

Before going any further though–breezes will trigger these type of motion sensors. So typically an air conditioner coming on would trigger it anyway, not sure if that’s what you want.

Were you intending this to notify you if the kids got too close to the air conditioner or were you concerned about an intruder trying to come in that way? Or?

It is intended for going off if an intruder broke in. The sensor is IR correct? This will trip if there is no visual movement but air passing by? That seems weird but I’m no expert. If that’s the case then I guess I can position it differently or limit its view like you have. Ill just have to play with it once I get it.

Check out the “hundreds” of images you can get with this Bing Search (or do a Google equivalent).

But, roughly, for the fun of trying to describe it…

PIR’s (Passive Infra-Red Sensors) are like very dumb cameras that see “warm light” (i.e., infrared); generally that means the warmth coming from a body. Most look for “motion” of this light, by a very simple method … the wavy segmented Fresnel lens. The “wavy” nature of this lens means that if the warm body is in one location, the “image” of the detected heat is a certain intensity on the internal sensor. As the body moves, the next part of the lens does the “focusing” and it will be more in focus or less in focus … thus changing the intensity of the infrared light on the sensor. This flurry of intensity is reported as “activity” – i.e., motion detected.

Can “warm air” trigger the sensor? I’ve never experienced it, but I guess if gust of air “looked” like a warm body to the very low resolution IR sensor, then… Yes.

If you can try to put yourself “inside the sensor behind the lens” then you can get an idea of what the shape of the coverage area is. Some lenses are spheres, some are half-cylinders. You can often successfully cover a part of the lens with electrical tape to limit the “view” of the sensor.

Such as:



I believe the OP was trying to look for a direct answer, like a technical drawing of the effective “cone” of the specific ST motion sensor.

So even though your explanation is very detailed and helpful, it didn’t actually answer the question, which I am also looking for.

For me I need to know that if I hang the ST motion sensor on one corner of my room,what is the area it can monitor so that I would know where to place more sensors to cover the whole room without overkill. It’s not like a camera where you can just look at the picture to determine the coverage area yourself.

Agree with jayle on OP and for the same use case. I am looking for a cone diagram for the ST motion sensor. I have one for the aeon lab ones I bought for outside as it was in the included mini-manual.

Anyone have one for the ST?