Lightswitch for indoor light sometimes triggers outdoor PIR sensor light

[jamesmacwhite]

I've noticed that a simple one way switch for my downstairs toilet light, seems to be able to trigger my Outdoor PIR light to turn on.

This is what I could determine:

1. The downstairs toilet light and the outdoor light are on the same circuit, looking at my consumer unit marked "Downstairs lighting".
2. The outdoor light can sometimes be triggered when the downstairs toilet light is switched to OFF but it doesn't always happen. It doesn't appear to happen ever when switching the light ON.
3. If I turn off the actual switch for the outdoor light itself, repeating point two doesn't appear to activate the light, but I'd imagine this should be expected when the actual switch for it is OFF.

What could be the cause of a switch not related to outdoor light triggering it? Other than being on the same circuit, could there potentially be electrical signals being interpreted by the outdoor light incorrectly? I'm confident, it's not the PIR sensor being triggered by any movement outside.

 

[BS3036]

Does your downstairs loo have a CFL bulb?

 

[Harry Bloomfield]

Could the PIR be sensing the light level changing maybe through a window? Failing that, it must be the PIR is over sensitive to switching surges.

 

[jamesmacwhite]

Does your downstairs loo have a CFL bulb?

I haven't confirmed as never removed the light casing, but it's likely it's a CFL blub as it briefly flickers when first switching on before being illuminated fully, that would suggest it's a fluorescent blub isn't it?

 

[jamesmacwhite]

Could the PIR be sensing the light level changing maybe through a window? Failing that, it must be the PIR is over sensitive to switching surges.

It's an interesting point, although the position of the outdoor light and it's field of view should in theory not be effected by any change in light level from that area. The downstairs toilet and the window is behind the field of view of the sensor.

Looks like this from a floor plan, the red circle is the rough position of the outdoor light on the outside wall. The nearest light source from the downstairs WC window is behind the sensor. The hall in theory could cause that through the glass on the door and even more likely the larger window area from the living room, but I tested this in complete darkness so no other possible light could have been present. Leaning towards perhaps the outdoor light itself very sensitive to changes in the circuit?

 

[Harry Bloomfield]

I haven't confirmed as never removed the light casing, but it's likely it's a CFL blub as it briefly flickers when first switching on before being illuminated fully, that would suggest it's a fluorescent blub isn't it?

Yes! You could try swapping it for an LED.

 

[jamesmacwhite]

Yes! You could try swapping it for an LED.

Thanks, that's relatively a cheap experiment to try and also potentially better anyway generally, given LED are meant to be more energy efficient? No harm either way I guess!

 

[BS3036]

Sounds good. I've had experience of florescent lights creating quite bad spikes when being switched off.

 

[jamesmacwhite]

Sounds good. I've had experience of florescent lights creating quite bad spikes when being switched off.

Just had a look properly and took the base off the light itself, it's a 2D 16W 2pin lamp bulb which I believe is quite commonly CFL, but there do seem to be LED variants, will have a look around at suppliers.

Edit: Potentially, https://www.screwfix.com/p/luceco-gr8-2-pin-2d-led-light-bulb-750lm-6-5w/8156x.

 

[Harry Bloomfield]

Just had a look properly and took the base off the light itself, it's a 2D 16W 2pin lamp bulb which I believe is quite commonly CFL, but there do seem to be LED variants, will have a look around at suppliers.

Edit: Potentially, https://www.screwfix.com/p/luceco-gr8-2-pin-2d-led-light-bulb-750lm-6-5w/8156x.

I would not go to that expense / trouble for a simple test - just fit a lampholder and an ordinary light bulb in it's stead.