cjames53's profile

Thu, Mar 24, 2022 3:00 PM

3 False Alarms in One Night from Motion Detectors!

Our system has been working well for about six months with no problem. Last night, three false alarm from two different sensors! First one was in the garage, which was closed, no animals, door sensor not tripped, no heater vents, no sunlight. I.e. nothing could possible have tripped it. The second sensor was in a closed, unused bedroom. The door was locked (sensor not triggered), heater vent is closed, bedroom door was closed. I.e. nothing could possibly have tripped it.

One sensor could plausibly be defective. But two in one night? Impossible. This sounds either a software flaw, or sensitivity to some inexplicable RF signal.

A good night's sleep ruined, and now I don't trust the system. What can I do?

Community Admin

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2.9K Messages

5 m ago

Hi @cjames53 ,

You're already on the right track. The only way that a Motion Sensor can be triggered is by a source of heat entering the field of view. It isn't possible to trigger from RF interference or anything like that.

And you're right, it's a bizarre coincidence that two different Motion Sensors in totally different rooms could both have false alarms at the same time - yet not totally impossible!

It might help to know that the Motion Sensor works by detecting a contrast in heat. So if it was particularly cold in your garage, or that room, even smaller heat sources might appear larger. I wouldn't be surprised if it was some sort of bug or lizard getting right up close that did it.

The other thing that would help is to know more about what both sensors were pointed at. What else is in those two rooms that the sensors can see? And what about windows? That can help us piece together a better picture of what happened.

3 Messages

5 m ago

Thanks Davey.

There was a moth in the garage that was captured by the camera; could a moth trigger the motion detector? Nothing else you suggest would apply in the garage; there is no source of heat.

The one in the bedroom is in a corner above the door, pointed across the room. There is no source of heat (the vent is shut off) and the vent is under the bed anyway. There are four windows, but the blinds were drawn. The outside door was locked, and the door to the hallway was closed. To the best of my knowledge, there are no insects or other in the room.

The other weird fact is that both motion detectors were triggered at exactly the same time -- yet one is in a detached garage, 30 feet away from the house, and the bedroom is on opposite side of the house from the garage. I.e. the two sensors are at least 70 feet apart and completely isolated from each other.

How can that be possible? It can't be that two moths flew in front of two motion detectors at the exact same moment.

Community Admin

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2.9K Messages

5 m ago

The only thing I could think of is if both sensors were facing windows on the same side of the house, and maybe there might have been lightning or something else that was strong enough to get through the class (which you might know is an insulator).

At this point, we might not ever find out what caused both triggers. But I would suggest setting either one or both of those Motion Sensors to "low" sensitivity, meaning that they need larger heat signatures to trigger. You can do that through the switch in the back of the unit, next to the battery.

3 Messages

@davey_d​ I actually checked the USGS to see if there had been an earthquake, which would have explained it. But no luck. The garage sensor is in a dark garage, facing away from the windows, which are covered with blinds. So no luck there. I think you're right; it's inexplicable for now.

Regarding lowering the sensitivity: They're already set to low. Which is really unfortunate, because it makes the garage sensor nearly useless -- it only detects motion about ten feet away, so most of the garage is unprotected.

All in all, it's rather disappointing.

Thanks for your suggestions.

6 Messages

@davey_d​ let me understand on the back of the most detector you have high medium and low but this is this is sensitivity to the heat signature or is this distance if it sensitivity that would be great because I could cut it down and hopefully avoid false alarms could somebody give me a definitive answer on this thank you Tom