Soffit lights to work with a PIR

I have soffit down lights around my bungalow . I was thinking to add a PIR to the circuit, with a power supply cable from the isolation switch then to an existing timer this turns the lights on at any preset time, m however when I look at the wiring to one of the first lamps closest to the isolation switch and timer I see these ( see attached) if I use a non contact sensor, I get a low pulse on the black cables a high pulse in the brown , earth nothing ( thankfully) but a low pulse on one of the grey cable and a high pulse on the other grey cable . Separating them still sees the lights illuminate? I do have a security light fitted to the rear of the property that runs from the mains box next to where the down light insulation switch and the timer is located If I turn the rear security light off using the isolation switch provided all cables are then dead . I assume there much be some form of neutral feed from the rear security light when power is on . So now unsure where to put a sensor in within this wiring set up and also how to wire it ? Any suggestions please Kind regards in

Have a look in the timer see what colour wire is doing what.

This is what I have wired . It goes from the timer, to the junction box and then on to the two isolation switches

Do you have a wider picture of the wiring around the timer and isolators?

As an aside, have you thought or using something like the Steinel NIghtmatic in place of the timer?


This will automatically adjust for lowere light levels and can be set to turn off over night.

An Alexa compatible switch, could be set to turn on, or off, at any times of your choice, or on at dusk, off at dawn, or be switched by your phone from almost anywhere, or a combination of.