A Study on Illuminance Thresholds That Trigger Occupants'Autonomous Light Switching in Response to Changes in Ambient Lighting

WU Mingxuan; LI Sijia; ZHANG Songbo; YANG Biao

doi:10.3969∕j.issn.1004-440X.2026.01.003

Abstract：Intelligent lighting is a crucial component in realizing smart buildings.The currently widely discussed inputs for intelligent lighting control include occupant presence sensing and real-time illuminance monitoring.Typically,real-time illuminance data are usually compared with preset illuminance thresholds and combined with occupant presence information to generate control outputs for switching lights on or off,achieving energy savings.Although this strategy attempts to mimic human control patterns,its performance in practical applications has been unsatisfactory.This study focuses on the thresholds corresponding to the environmental light triggering mechanisms for switching lights on or of,respectively.Through psychophysical experiments conducted under a reading scenario,the following conclusions were obtained:(1)The median illuminance threshold for environment-light-triggered switching on(i.e.,the switch-on threshold)is 212.65 lx,while the median illuminance threshold for switching off(i.e.,the switch-off threshold)is 472.75 lx,and the dispersion of the switch-off threshold is significantly greater than that of the switch-on threshold;(2)the initial illuminance level of the environment light change(decrease)significantly affects the switch-on threshold—the higher the initial illuminance,the higher the switch-on threshold—whereas the switch-off threshold is not affected;(3)the illuminance level of the controlled light significantly affects the switch-off threshold—the higher the illuminance of the controlled light,the higher the switch-off threshold—while the switch-on threshold is not affected.These results provide a scientific basis for intelligent lighting control strategies.