PACT CAM: Wearable Sensor System to Capture the Details of Cigarette Smoking in Free-Living

Recently, body-worn sensor systems have extensively been studied to assess the manifestations of cigarette smoking in the free-living. This paper provides a detailed description of a camera-based wearable sensor system, PACT CAM, that can capture the most relevant images of cigarette smoking at every second from the eye level. Along with a 5MP camera, PACT CAM includes inertial sensors to detect the wearer's motion, a micro-SD card capable of storing similar to 1 million images, a rechargeable LiPo battery to support the image capture for similar to 32 hours with a single charge, etc. This circuitry was enclosed within a plastic enclosure with a provision to facilitate attachment to the eye-glass temple of the wearer. To support multi-day data collection, imaging was configured to pause while the sensor system was stationary or put to charge, and resume while out of inactivity or removed from the charger. During this inactivity state, the system was configured to enter into the low power sleep mode with similar to 0.05mA power consumption. The EXIF header of the captured images contained detailed information on the image capture timestamp, inactivity time, the wearer's walking steps at the moment of image capture, etc. This EXIF information can be accessed from a computer application without requiring the manual image review. The smoking context, as captured objectively by PACT CAM for multiple days, is critical to infer the overall smoking behavior of a person and select proper cessation intervention methods. The performance of PACT CAM was also validated involving two volunteer smokers wearing it for multiple days.