Multiple motion sensors required to trigger intrusion alarm

I am relatively new to SmartThings, and I’m trying to convert from Lowes Iris. On both platforms, I find many of the motion sensors are too sensitive. Iris had a simple setting to require multiple sensors to be activated prior to triggering an alarm. (i.e. intruder opens a door and then walk into view of a motion sensor, or breaks window and moves past two motion sensors).

I’d like to set this up with the Smart Home Monitor, but I only see how to include/exclude certain sensors and not to require multiple before triggering the alarm. Any suggestions on how to handle this and avoid unnecessary false alarms? I’m using Hub v2

There isn’t any stock behavior that I’m aware of to do that. I can think of two possibilities.

One is a custom virtual device type that aggregates all the sensors into one uber-sensor. That custom device type would have the logic on when to trigger based on which and how many sensors were active in a certain time period.

The other is a custom smart app to replace Smart Home Monitor.

However, it might be worth looking at the cause of the sensitivity problems. Are they being caused pets? In that case using an “armed stay” mode where motion sensors are ignored might be more appropriate (and you get out of the box). Are the sensors outside? A lot of the motion sensors seem prone to false positives when used outside. Or is it something else going on?

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Thanks for the ideas. I’m not familiar with the virtual device, so I’ll check into that.

I don’t have pets, so that’s not what’s causing the alarms. I can’t actually figure out what is, perhaps sunlight/shadow movement or other temperature changes causing the sensor to move.

Right now the sensor is just sitting on a window ledge, I was holding off on mounting it until I had tested it for a bit. I am impressed with how quickly it responds to actual motion.

Which sensors are you using? Do you have problems with the motion sensors triggering other events when they shouldn’t be? (i.e… lights turning on/off) Are these sensors outside or inside?

I have one tilt sensor in the garage that constantly gives me false readings, but I was aware the sensor is faulty sometimes. Other than that, my motion sensors are spot on.

You can try this beta smart app. I’ve been meaning to try it myself.

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Is this a SmartThings motion sensor or some other brand? I’ve used ST’s, an Aeon multisensor and some Fibaros and have never seen false positives except when I tried to use the Aeon outside looking down from the porch ceiling (that had lots of false positives).

Is it sitting in direct sunlight when it happens? Odds are you aren’t home when this is going on so you may not know, but it’s probably worth spending time so you can uncover the root cause. If you can’t trust your sensors then it’s hard to trust the system and you don’t want to get in the habit of ignoring reports.

You could always setup a “notify me” alert when there is motion on the problem sensors. Then if SHM gives you an alert and you DO NOT receive a txt or push notification, it could be a bug with SHM.

PIR Motion sensors are temperature-sensitive. It’s the reason that many of them are intended for indoor use only. Even a passing warm breeze, or cloud cover on the sun, can create enough of a temperature differential to set them off.

This is why the placement matters so much and why one person might have no false alarms at all with a particular model and another one have them every few minutes. A climate like Florida’s, for example, with humidity, breeze, warmth, but variable temperatures during the day, plus flying insects, is famous for setting off motion detectors with temperature false alerts.

Motion detectors also do much worse when they are right on the window ledge because the window itself creates temperature variance due to the lack of insulation in the glass. It will get hotter in the sun, it will get colder as the weather gets cold then wood or brick.

So typically if you did want to put a motion detector outdoors on a sheltered porch, you would keep it away From windows, instead putting it in a very sheltered area against wood or brick. (And avoiding areas of reflection.)

Even indoors, a motion detector near a window often varies in temperature by 10° compared to the rest of the room. So again, we try to avoid windows when placing motion detectors. They’re good places for contact sensors. But not motion sensors.

Air-conditioners and heating systems can also cause problems. Many people get false alarms because they place a motion sensor in a room with an air conditioner in in the winter, not realizing that temperature variation as the air conditioner comes on and off in the spring will set off the motion detector.

Zone detection is a good way to handle this, although even that won’t necessarily work outdoors in Florida since warm breeze might indeed hit all three motion detectors at the same time.

So sometimes it’s just a matter of trying several different placement areas for a few days until you can find an area of stable temperature to create the background against which the introduced motion will be measured.


This has been the most helpful statement I have seen for diagnosing my Motion Sensor woes. I’m definitely now going to go home and play with the placement of my motion sensors, as I’m getting a lot of false flags from the downstairs bathroom sensor… which is on the windowsill pointing inwards

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