PIR false trigger by house light switch

[88v8]

External LED flood with standalone PIR.
There are two house light switches, which when switched off, cause the the flood to come on.
One switch is about 3ft from the PIR on the same level, the other about 5ft down on the floor below.

The flood comes on for its normal timed On period, then shuts off. Otherwise the flood/PIR work as they're supposed to.

The triggers are both ceiling switches, cord pull. We have similar switches throughout the house, no other issues with them.

Just to confirm in case you were wondering, the PIR is powered from the same light circuit.

This has been going on for the three years the flood has been there, but I would like to stop it. Is there anything I can put in the circuit to prevent this false triggering?

TIA.

 

[Alec_t]

Sounds like a voltage spike is generated on switch-off. What sort of lights (incandescent, fluorescent, LED, .....) do those two switches control?

 

[88v8]

Both incandescent.
One is 1 x 40W, the other 2 x 40W.

 

[88v8]

I wonder if it's RFI from the spark as the contacts break.
I see this filter for DC applications, https://www.directindustry.com/prod/act-meters-international-ltd/product-116273-1401185.html perhaps there's one for mains.

 

[Taylortwocities]

Google snubber or spark suppressor.

This sort of thing you want

 

[88v8]

Aha, thankyou.

Where do I put it/them?
In the live feed to the switch, or from the switch to the light, or the live to the PIR?

 

[Taylortwocities]

Usually across the load (the two lights) that seem to cause the problem.