Characterization of Passive Infrared Sensors for Monitoring Occupancy Pattern

Monitoring the occupancy pattern of elderly people can reveal changing trends in their health status. In this paper, we investigate the spatial characteristics of a pyro-electric infrared sensor at different walking speeds at different distances to design and develop a low cost and low power unobtrusive monitoring system. The pyro-electric infrared sensor has high performance for infrared radiation detection at room temperature. The choice of pyro-electric infrared sensor for the design of unobtrusive activity monitoring system is due to the fact that they are inexpensive and consume very low power. As these sensors are passive and are wall mounted, the system is relatively unobtrusive. An occupancy monitoring system using ZigBee wireless technology and infrared sensors has been developed by Biomedical System Laboratory at university of New South Wales, Australia. The analog signal from the sensor is proportional to the surface temperature, velocity of movement and the distance of the object from the sensor. Experimental results show that the sensor output is non uniform at different distances and at different angles for different walking speeds