SmartThings Community

FAQ: Where to locate motion sensor for fastest response?

(Jim Newman) #1

I have a downstairs hallway that’s perhaps 12 feet long, with a doorway to a spiral staircase at one end (where the picture is taken from) and a door into the garage on the other end. As you can see in the picture, there’s a jog in the hallway. Not seen here are another doorway about 4 feet to the right of the one by the staircase, a bedroom door to the left at a 45-degree angle (you can just make out a bit of the trim on the corner of the wall, near the top), and a laundry room doorway on the right as you go through the jog.

The hallway is dark and I want to automatically turn on the lights when I come off the stairway or enter from the garage. I have an Ecolink motion sensor and I’ve tried placing it in each of the four locations marked with circles. (The two near the top are on the hallway side of the door, of course.) All four locations have a clear line of sight to the area I want covered. I’ve mounted it with the long axis vertical, and horizontal. Occasionally the lights will go on very quickly - but most of the time, I can walk the entire length of the hall before the lights go on. Sometimes, I’ve even had to stop at the end of the hallway and “dance around” a bit before it “sees” me - and I’m not a small guy. The pet immunity jumpers on the sensor are OFF.

Any suggestions on placement? Or will this particular sensor not do the job and I need to use a different brand?

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The first thing I always look at with PIR motion sensors is the angle of incidence.

These sensors detect very small variation in heat moving across the sensor field. For this reason, they will trigger much more quickly if a person is walking crosswise to the sensor rather than if they’re walking straight on towards it.

So sometimes it’s just a matter of changing the position of the sensor, typically by 90°, to see a much faster response time. :sunglasses:

In your case, I would place a motion sensor at shoulder height on the wall rather than trying to angle it from the ceiling.

There are couple of sensor models which are designed to be placed on the ceiling, so you could try one of those instead. But they are still designed for a crosswise detection, it’s just that you are walking crosswise underneath it.

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(Jim Newman) #3

Thanks. Just FYI, when I said “horizontally” or “vertically” before, I meant the direction of the long axis of the sensor when mounted on the wall - I wasn’t trying to use a ceiling mount. But I do think I have a spot where a shoulder-height wall mount might work. Thanks for the suggestion!

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What model is your sensor?

(Jim Newman) #5



OK, that model does have a sensitivity adjustment and also has a test mode. In test mode the light will flash when motion is detected. So if you put it into test mode, you can see if the issue is that the sensor is not detecting you or if the issue is that the sensor is detecting you but your smartthings network is slow to process the detection message.

In other regards, it’s a standard PIR sensor. So shoulder height 90° to the person is going to get the quickest response. Or anything down to knee height. You want to get the body mass traveling across the detection zone.

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(Ben W) #7

Ecolink’s are slow. I have one in my garage and it takes a bit. Its pretty slow at detecting motion.

Iris Motion with smartlighting usually triggers a little less than 1 second once it detects motion. Have them all over my house now.

With Core, its about 1.5 seconds. Maybe 2 seconds if its a little slow. Only have one rule triggered with Core.

You can always try placing it on the ground and see if it triggers a little faster. A simple test is just to have the motion sensor in a box. Move you hand over it and see how long it takes to respond (turn on lights).


I have one of these that I put low in my hallway and I leave it on “Test” mode all the time. It might be my imagination, but it seems to respond faster, plus I like to see the red light flash for confirmation. I have it placed down towards the corner end of the hallway at a 45 degree angle so if I’m walking towards it, it does a pretty good job of sensing me. Since it’s at a 45 degree angle, when I walk out of my bedroom which is perpendicular to the hallway, it still picks me up pretty quickly.

(Ryan) #9

I use all ecolink sensors I also leave mine in test mode , I like the 5 second time. I think their great motion sensors. Their cheap, easy to setup and reliable. I had 6 of them for 2 years now and still have 90% battery left. I use them outside and inside they have yet to fail me.

(Jason "The Enabler" as deemed so by @Smart) #10

I started out with the ecolink sensors and hated them. They were never fast enough for me.

I now use some ceiling mount sensors, I have five of them… Used in the garage, office, hallway, and master bedroom.

But, I also use the iris sensors. They are cheap, very fast detection, and very short recovery time. I have them all over the house! Even in the showers…

I prefer the iris sensors and I stay away from the ecolink because the exact reasons you are staying. My two ecolink sensors are sitting in the garage… Being useless to me…

You can get the iris sensors at Lowe’s.

(Eric) #11

What ceiling sensors do you use?


Concur, while I haven’t use all models of motion detectors, the Iris ones are super fast… I predominantly use mine with Smart Lighting, and very rarely do I have to wait for a light to turn on.


(Ben W) #13

Set up the ecolink in test mode. Still took about 3 seconds to detect me. I walked towards it, starting about 20 feet away and my lights triggered when I was about 5-6 feet away.

Another bonus of the iris is that they are tiny. They blend into the surroundings. I have them on top of door fames/windows and they are barely noticeable.


Walking towards it is always slower with any PIR sensor. These are intended to catch motion that walks across the field 90° to the sensor. Not directly towards the sensor. Some sensors and sensitivity settings are better at catching direct motion than others, but it’s not the way they are designed to be used. Position the sensor so that it will catch motion walking across the field and you will always get faster detection regardless of brand. :sunglasses:

(Ben W) #15

Just did another test walking at 90 degrees at a distance of about 15 feet away from sensor.

I was able to to take 5 steps into my garage, about 3 seconds, before it triggered (the red led on it). The ecolinks are just slow.


No question, with the exception of the Lowe’s Iris (which probably benefits from a much larger production run), most of the less expensive sensors are much slower than the more expensive sensors.

It’s one of the reasons I always recommend buying electronics from a place with a good returns policy. Sometimes there’s no way to tell if a device will meet your particular use case until you give it a try. :sunglasses:

(Jim Newman) #17

In my situation, the only way to walk across the field would be to mount one perpendicular to each of the two doorways, or mount one halfway down the hall in which case I’d be several steps into the hallway before I’d be at a point that would reasonably be considered to be “across the field”. I had no luck getting an Iris Smart Button to work, if I try the motion sensor I hope it goes more smoothly.

(Jim Newman) #18

Well, to their credit, Amazon gave me full credit and prepaid shipping on my return of the Smart Button. In fact, they posted the credit to my account as soon as UPS scanned the barcode on the return package.

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(Jim Newman) #19

Which Iris sensor? Their website has a MOT501 “Iris 120-Degree Passive Infrared Security Motion Detector” and 3326-L “Iris Motion Sensor”.


What about a ceiling version mounted overhead? That’s often a good way to get a crosswise angle of incidence, but you need one with a wide field, which is why it’s better to choose a device designed for a ceiling mount. But you can try it with any motion sensor it’s just a question of where the field catches you. If you want to catch someone coming out of a bedroom into a hallway, a ceiling mount sensor will often work fine.

Also, you can see this in the first graphic I posted upthread, but I didn’t call out specifically that the detection field widens with distance. This can be a help for a ceiling mount, that extra foot or two of distance gives you wider coverage below. Sometimes you just need to experiment to find the best placement.