False PIR switching

[kez1]

Hi,

Some of my house PIR's switch falsely, in an apparently random way.
Others trigger correctly only when light levels are low and movement is detected.

For example the hall way cupboard light cannot be triggered by the PIR in the ceiling of the cupboard when the door is closed as there is no window and when the door is closed no movement can be detected. So triggering should not occur.
And yet, often I come into the house and can see from under the door of the hallway cupboard the light is on! False triggering.
In the hall way cupboard is the Gigabit switch for distributing CAT6 internet around the house, a rasp-pi, and the TV amplifier for distributing the TV signal around the house via coax. Some of these devices may generate a small amount of consistent heat and have flickering leds. I don't think this would trigger the PIR though ... not 100 % sure.

Rather I feel there many be some electrical noise on the PIR? though I have no idea where this could come from.

The bathroom lights are connected to PIR's and work perfectly. Never false triggering.

The hallway lights are connected to PIR's and generally work perfectly, though there is occasional false triggering.

The kitchen, galley and breakfast room are all on PIR's and false switching does occur more than occasionally.

There do appear to be at least 3 lighting circuits on the mains domestic RCD box in the garage.

Anyone any ideas.

 

[deadshort]

There's a moose loose aboo't yer hoose !


DS

Translation- You have a rodent in your dwelling !

 

[kez1]

Hi deadshort,

Thanks for that. Never thought of that
If there was I would see the droppings.
I never hear that kind of scratchy scampering sound U hear when U have mice.
It's a very clean house.
Rodents in a clean house that you never hear?
I suppose it's possible.

I do definitely have a few spiders. A large arachnid? Would it give off a large enough IR signal?

 

[deadshort]

When I use my microwave oven, the hallway lights which are PIR controlled come on! But only if it's an M+S ready meal !

How's that !!

DS

 

[JohnW2]

If there was I would see the droppings. ... Rodents in a clean house that you never hear? I suppose it's possible.

Very little is impossible, but rodents that don't leave droppings must be getting close

A large arachnid? Would it give off a large enough IR signal?

I seriously doubt it, with any 'UK arachnid'! Far more likely, I would suspect, would be 'electromagnetic interference' (interfering with the electronics, not the IR detection), such as DS's microwave - and also, I suppose, it's not impossible that some of the PIRs are faulty. Any WiFi in addition to the wired CAT6, or anything 'wirelessly controlled'?

Kind Regards, John

 

[JohnW2]

I seriously doubt it, with any 'UK arachnid'

On reflection, if it actually crawled across the face of the PIR window, I suppose that might do it.

Kind Regards, John

 

[kez1]

Hi JohnW2

Yes e-m interference. Seems possible. Hallway cupboard does have e-m associated equipment in it and electronics that could potentially generate e-m frequencies. May wrap upper part of PIR in Al kitchen foil as an e-m shield, though triggering is likely from lower part? - which obviously - cannot be shielded as such.

Yes, PIR devices could be faulty. I think I may have a new spare, and if so will swap out the cupboard one to see if there is any difference.

I'm wandering if electrical noise could overwhelm sensitive PIR electronics. Would have thought domestic design would have been with this in mind. Could be wrong though.

 

[JohnW2]

I'm wandering if electrical noise could overwhelm sensitive PIR electronics. Would have thought domestic design would have been with this in mind. Could be wrong though.

That could be wishful thinking, particularly if they were 'budget' products. AFAIAA, regulations only relate to emission of EMI, not susceptibility to it!

Kind Regards, John

 

[kez1]

JohnW2

We covered e-m interference .. what about on mains circuit electrical noise, and if so are there circuit damping options?

 

[JohnW2]

JohnW2 We covered e-m interference .. what about on mains circuit electrical noise, and if so are there circuit damping options?

Theoretically possible, but difficult to diagnose.

Kind Regards, John

 

[Iggifer]

Don't know what kind of light fitting you have in these cupboards but I was on a rewire where a pendant was causing false switching. Putting a lampshade on the lamp cured the problem

 

[ban-all-sheds]

For example the hall way cupboard light cannot be triggered by the PIR in the ceiling of the cupboard when the door is closed as there is no window and when the door is closed no movement can be detected. So triggering should not occur.

And if you have a normal switch, that cannot be triggered by movement when the door is closed.

Or when it's open.

Or by mice, spiders, flickering LEDs, gusts of warm air or stray microwaves.

So excellent are they at discrimination that the only thing that will trigger them is physical movement of the rocker.

Anyone any ideas.

Install a switch instead.

 

[JohnW2]

Install a switch instead.

I wish I'd put a bet on your piping in with that!

Kind Regards, John

 

[ban-all-sheds]

Seems the simplest, most obvious solution.

 

[JohnW2]

Seems the simplest, most obvious solution.

It is. However, some people clearly perceive a benefit in the less simple, less obvious (and less cheap) approach, even though it comes with some downsides!

Kind Regards, John