Motion-Activated Lighting: The Mounting Height That Covers a Driveway Without Leaving a Dark Path Beneath the Sensor

A motion-activated light protects only the ground its sensor actually sees, and mounting height moves two boundaries at once: the far edge of detection, set by the sensor's 12 m slant range, and the dead zone beneath the fitting, which grows with height. This study samples a 5 m by 8 m driveway on a 0.1 m grid from stated assumptions, testing each point against the range limit and a dead zone whose radius is 0.45 times the mounting height. Coverage is highest at the lowest tabulated height and falls as the dead zone swallows the near corner: 97.5 percent at 2.5 m against 90.2 percent at 5 m, where the dead radius reaches 2.25 m and an approach hugging the wall passes beneath the sensor entirely. The practical rule balances this geometry against reach and tampering: mount the sensor between about 2.5 m and 3.5 m, above casual reach but low enough that the dead zone stays under about 1.6 m, and aim the fitting across the likely approach path rather than along the wall it is mounted on. SIMULATED, NOT MEASURED.