Recently, smart home applications are increasing fast, including but not limited to smart thermostats, smart lighting, smart cameras, surveillance system, etc. Passive infrared (PIR) sensors play an important role in these applications to perceive the presence and/or the motion of humans. However, PIR sensors are not able to detection stationary occupants while stationary presence takes up the most time of the day. And thus, the resulted false-negative detection leads to uncomfortable light/temperature swings, shortened equipment’s lifespan, and/or energy waste, etc. To address this issue, our group developed Synchronized Low-Energy Electronically-chopped PIR (SLEEPIR) sensors that integrate an electronic liquid crystal (LC) infrared shutter with an off-the-shelf PIR sensor. More specifically, the infrared shutter made of polymer dispersed liquid crystal (PDLC) sandwiched by two germanium windows will periodically chop the long-wave infrared signal received by the PIR sensor so that any human presence can still be detected due to the electronically shuttering. The result shows that the proposed SLEEPIR could detect both stationary and moving occupants with high accuracy. A SLEEPIR sensor network is also developed to monitor the presence detection in a residential house. With the help of machine learning and sensor fusion, the sensor network achieves high accuracy in room-level presence detection. Thanks to the high modulation, low driving voltage, facile and low-cost fabrication approach, the SLEEPIR sensor has a high potential in smart home applications.


True Presence Detection via Passive Infrared Sensor Network Using Liquid Crystal Infrared Shutters

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

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