light keeps switching on (wifi interference)

[rrozema]

Thought I'd share this little story with other users as it might help them in finding what is going on.

A neo coolcam NAS-PD01Z motion sensor (PIR) switches on the light in my hallway.This has worked well for quite some time now. Yesterday however I noticed that the light was on much more than i'd expect. It kept going on immediately after it switched off. There was nobody in the hallway, so why did the light go on? Sometimes one of my cats trigger this light too, but there were none in the hallway either. So was it the battery in the sensor going weak? I replaced the battery in the unit and it still switched the light on. Looking at domoticz' log file i see that it really is the sensor sensing motion. What is going on? Am I being haunted? According to the deive log the device has been doning this for almostr 2 days now. And then it hit me: 2 days ago I replaced my wifi router by a new, stronger one. This router was bigger than the previous one, and it didn't fit in the location the old router was in. So I had to find a new location for the router and I had placed it inside the meteringcloset (is this even a word in english?). The sensor was no more than 10 centimeters away from the router's antennas, separated only by 1 wood board. So I moved the sensor a little bit further away from the router (roughly 1 meter was the most I could move it) and since then the sensor works fine again.

So it turns out these pir sensors can send out a signal to switch on when influenced by strong wifi signals. The advice to keep some distance between (powerfull) electrical devices is a valid one

[lost]

So it turns out these pir sensors can send out a signal to switch on when influenced by strong wifi signals. The advice to keep some distance between (powerfull) electrical devices is a valid one

Hi,

Already experienced similar issue with an external PIR (simple relay driving device, no radio control) that switches a spotlight. This PIR is located close to an external IP camera using wifi to send captures (using it's internal, video based, motion detection) on a FTP.

Issue was showing mostly at twilight: When the camera was sending captures, or I was connecting to the video stream (thus triggering wifi connection), the external light was switching even if nobody/no heat source was there.

At full/dark night, issue was not showing.

=> My bet: PIR sensing is subject to noise, especially at dawn (maybe switching level from my PIR was more noise immune in dark night?), induced by close wifi devices. I just screwed a small stainless steel sheet between them (a ferrite on the PIR wires did not do the job, so noise was not coming from wires) & no more problems.

So very close Wifi definitely disturb PIR device, probably inducing current in the sensor output.