Last night: battery PIR lights going crazy

Perhaps seeing a reflection in the window that is not normally open.

In the past I have found that PIR lights can be triggered by a breeze causing hedge branches to wave about (solved by cutting back the hedge!), or nocturnal animal activity, such as fox, badger or even cat. Have you recently acquired neighbours with a cat, or even got one yourself?

Wind can do that outdoors. I have two of these outside, and I normally turn them off on windy nights, which aren't that common. Yes, I suppose it's air currents at a different temperature to the average.

I once made the mistake of placing an IR movement sensor facing my front door - to trigger the burglar alarm when someone entered the premises. It was soon moved to be above the door facing into the hallway. Cold envelopes delivered through the letter box triggered the alarm more than once :(

We had birds on one premises who built a nest inside the factory roof, just where the sensors were...

In our previous house, I had installed a PIR controlled light which seemed to trigger for no reason.

It turned out to be a ‘waft’ of warm air from the central heating boiler flue.

The layout of the house etc and relative positions sometimes causes a ‘waft’ of warm air to pass in front of the sensor.

As it happens, we wanted a gate down the side of the house. That changed the air flow, at least when closed, problem solved.

I’m sure our sensor was a ‘dumb’ one, it just detected moving a moving heat source, not a person.

Jethro <jethro snipped-for-privacy@hotmailbin.com wrote

Never ever get anything like that with my Philips Hues and have quite a few of them and have massive great patio doors open in the summer

Discussing this reminds me that sometimes in cooler times, opening the patio door - which is directly below the floodlight PIR - can trigger it to come on. Again I can only presume a body of distinctly warmer air has looked like something passing by.

Have you seen the Qinetiq milli-centigrade resoution IR video imagery of flying bats. Their wing muscle areas glowing "white" after flying for a while. Local to me ,heavy rain, sets off a neighbours floodlights.