Light switching itself on....

[amfisted]

Seems like a totally daft question, but I have to ask.

When we moved into our bungalow last May, there was an old halogen PIR on the wall outside the kitchen door that didn't work, so I replaced it with a modern, low wattage LED PIR unit. There was no fused switch in the loft between the lighting circuit and the old light, so I fitted one when I installed the new unit.

My habit most days is to turn the wall switch for this unit on at night, and switch it off in the morning. Its on a double wall switch, the other switch being for the kitchen lights. In recent days I've been surprised to find in the evening that the light switch is already on when I thought I'd turned it off that same morning, and its beginning to seem as if the rocker switch is turning itself on. I've read some stuff online that suggest this can happen if there's a wiring fault, but at no point has the light circuit ever tripped.

Can light switches turn themselves on, as I suspect this one is?

 

[ericmark]

Very unlikely with a standard switch as the system normally goes over centre to ensure fast connection or disconnection, the switch would feel slack if it was likely to switch its self on. However my light switches could switch themselves on, they are designed to do just that, they switch on at dusk and off at dawn and also off at midnight and on at 5 am, so if I have the on in the morning latter than the off at dawn time, then yes they could be on all day, hence set at 5 am not 6 am but the switch is designed to do that.

 

[bernardgreen]

Some PIR sensors have an override function.

The lamp can be turned permanently ON by switching the supply to the PIR in the sequence ON -- OFF -- ON ( some PIRs need ON--OFF--ON--OFF--ON )

These sequences can be created by a switch with loose connection and/or worn contacts.

Its on a double wall switch, the other switch being for the kitchen lights. I

It might be that switching the kitchen lamp ON creates a transient dip in the supply voltage to the PIR sensor. A dip that the PIR sees as the OFF in the ON--OFF--ON sequence and thus switches to permanently ON mode.

The dip in the supply is due to the in-rush current that occurs when the kitchen lamp(s) are switched ON.

 

[amfisted]

Very unlikely with a standard switch as the system normally goes over centre to ensure fast connection or disconnection, the switch would feel slack if it was likely to switch its self on. However my light switches could switch themselves on, they are designed to do just that, they switch on at dusk and off at dawn and also off at midnight and on at 5 am, so if I have the on in the morning latter than the off at dawn time, then yes they could be on all day, hence set at 5 am not 6 am but the switch is designed to do that.

Thanks for that. The switches are fairly new, so not slack, but in order to check whether I'm simply forgetting to turn the switch off, I've decided that for the foreseeable future I'll tape it in the off position each morning, so that it takes the Electric Fairies a fair bit of effort to turn it on again.

 

[amfisted]

Some PIR sensors have an override function.

The lamp can be turned permanently ON by switching the supply to the PIR in the sequence ON -- OFF -- ON ( some PIRs need ON--OFF--ON--OFF--ON )

These sequences can be created by a switch with loose connection and/or worn contacts.


It might be that switching the kitchen lamp ON creates a transient dip in the supply voltage to the PIR sensor. A dip that the PIR sees as the OFF in the ON--OFF--ON sequence and thus switches to permanently ON mode.

The dip in the supply is due to the in-rush current that occurs when the kitchen lamp(s) are switched ON.

Thanks also. I'm aware of the override function in the PIR sensors, but neither this facility nor any dip in the supply voltage to the PIR sensor caused by the use of other switches should cause the interior wall switch to physically turn on or off, should it?

 

[Old Salt]

Has anybody died in that bungalow? They may still be trying to find the way out

 

[amfisted]

Has anybody died in that bungalow? They may still be trying to find the way out

That was my first thought also....alongside amnesia on my part.

 

[EFLImpudence]

Why do you switch it off every morning?

 

[bernardgreen]

should cause the interior wall switch to physically turn on or off, should it?

The switch should not be able to move it's rocker without assistance from a finger, a paw or other source of mechanical energy.

 

[amfisted]

Why do you switch it off every morning?

It’s just a habit I’ve got into. Similarly I switch the kettle off at the wall after it’s boiled. Used to drive my daughter mad, but since she became a homeowner, she does it too.

 

[amfisted]

The switch should not be able to move it's rocker without assistance from a finger, a paw or other source of mechanical energy.

My thoughts exactly. It’s now taped in the off position, so let battle commence

 

[Speedy23]

Poltergeist.

 

[ericmark]

I was switching mine off, and forgetting to turn it back on again. Not sure if bats, cats, foxes, badgers or squirrels, but PIR's seem to turn the lights on all the time, I don't mind lighting the drive for visitors, including milkman and postwoman, but not for captain beaky and his band, so moved in the main to simple timed or use phone to turn them on.

Although it feels as if one is switching the switch on/off, behind the facade there is a push button, well in fact three, and a pair of AAA batteries. That's for main door. Other lamps have other methods, including a relay which allows standard switches to be used, I don't expect you have anything like that, but some day I will die and some one will buy the house from my children, can you imagine trying to work out what is going on with a relay like that, the bottom two wires go to the switch and are extra low voltage, we never use the switch, always use voice commands to google Nest Mini's, in hind sight should have not fitted the relay in the lamp, that lamp is not going to be easy to open to gain access to the relay inside, hind sight and hind sight is easy, should have just used 5 smart GU10 bulbs, but wanted the switches to work with the app, and as fitted the app is just like the intermediate switch.

As said unlikely you have that system, but some day some one is going to buy a house with smart devices and they may not realise they even have them.

 

[Harry Bloomfield]

It’s just a habit I’ve got into. Similarly I switch the kettle off at the wall after it’s boiled. Used to drive my daughter mad, but since she became a homeowner, she does it too.

I habitually leave our kettle, after use, off the stand - just to force me to ensure it has water in it, before I can turning it on. Besides, kettle has LED's in the base - it lights blue when off, red when switched on. Seems such a waste, sat there glowing blue in the dark.

 

[amfisted]

Thanks again for the further replies. I've decided to leave the switch on permanently, even though it goes against all my instincts. So far Percy the Poltergeist hasn't got round to turning it off when I'm not looking.