Analyzing Sensitivity Characteristics according to Decrease in Intensity of Light from LED Light Source of Photoelectric Spot-Type Detector

Abstract

After the revision of “Fire Safety Standards for Automatic Fire Alarm System and Visual Alarm Equipment (NFSC 203)” in 2015 made it mandatory to install smoke detectors in apartments and medical facilities, their number has increased significantly. The detector used in the experiment was a photoelectric spot-type analog smoke detector. The experiment was conducted by configuring a real-time smoke monitoring system. In addition, the sensitivity characteristics of the smoke detector according to the decrease in intensity of light were analyzed. This was achieved by controlling the intensity of light related to the lifespan of the LED, a vital component of the smoke detector. When a intensity of LED light decreased by 10%, the sensitivity of the smoke detector decreased by 12.5%. When a intensity of light decreased by 30%, it decreased to 61% of the smoke detector sensitivity value. From these results, An equation for the change in sensitivity of a smoke detector according to the decrease in intensity of light was derived. It was confirmed that when the light intensity of the LED decreases, the sensitivity of the smoke detector decreases by about 37% more than the decrease in light intensity. Therefore, when developing a photoelectric spot-type smoke detector, establishing the LED current-radiation light characteristic curve and the correlation between the current of the light source and the ambient temperature will significantly improve the product's function and post-management.