Security lighting and floodlights

A passive infra red detector responds to heat moving across its field rather than toward it, which is why a unit aimed straight down a path performs poorly and one aimed across an approach performs well. Mounting height matters for the same reason: too high and the detection pattern flattens and loses range, too low and every fox sets it off. Most units want somewhere around two and a half metres and a slight downward tilt, with the pattern stopping short of the boundary.

Output has gone the wrong way for a decade. LED floods are cheap and bright and it is now easy to fit something that lights the whole street, which annoys neighbours, ruins night vision for anybody walking up, and does nothing for security. A more useful arrangement is modest output on a wide beam, aimed at the ground around a door rather than outward at head height, so an approaching face is lit rather than silhouetted. Where cameras are involved this matters twice over, because a bright light behind a subject makes the footage useless.

Wiring is usually a spur from a nearby lighting or power circuit, or a dedicated circuit where several lights are being run. Override switching indoors is worth specifying: being able to force the light on, or off, from inside covers both the evening you are working outside and the night it starts triggering on snow. A separate supply from the main lighting circuit means a trip indoors does not leave the outside dark.