Emplaced Sensors
This network includes sensor devices deployed in the environment (rooms, hallways, furniture) to support sensing and monitoring, including: temperature, humidity, motion, acoustic, camera, etc. It provides environmental sensing and control, interfaces for other devices, and a spatial context for operation.
General Properties
All devices are connected to a more resourceful gateway backbone, potentially by multiple hops. Sensors communicate wirelessly and may use either wired or battery power. Nodes in this network may vary in their capabilities, but generally do not perform extensive calculation or store much data. The sensor network also interfaces to multiple body networks, seamlessly managing hand-off of reported data and maintaining patient presence information.
Sub-Systems
Illustration of the MARC bed sub-system.
Some of the emplaced sensors may form a semi-autonomous sub-system. For example, the sensors illustrated at right are placed in/by a bed and can detect breathing rate, pulse, movement, and bed-exit falls. These are unobtrusive sensors that do not require interaction with the resident (integrated from the MARC).
The bed sensor is based on a air-pressure strip which measures the heart rate (low/high/normal), the breathing rate (abnormal/normal) and four levels of movement. The strip is located on the bed and is in contact with a person’s trunk when the person lies on the bed.
A gait monitor is used to detect when the patient leaves or enters the bed. This sensor also detects five levels of gait (impact and a combination between fast/slow and near/far). It is located on the floor by the bed, and can detect falls when the residente exits the bed.
A motion sensor detects movement during the night, to aid in quantifying restlessness, a measure of sleep disturbance.
Bed sensor processing in AlarmNet.
MARC bed sub-system.
Location and Light Tracking
We have adapted a low-cost sensor module that is capable of detecting motion and light intensity changes. The module also has a simple one-button and one-LED user interface for testing and diagnostics. The module is interfaced to a MicaZ type wireless sensor node that processes the sensor data and forwards the information to the rest of the wireless network.
Motion Mote
The image at left shows a MicaZ detached from its normal battery-pack and interfaced to the motion sensor via the 51-pin connector.
A set of such modules is used to track human presence and to monitor the lighting conditions in various locations of the living space. These activity data are used to maintain location context, and are fed to the back-end Circadian rhythm analysis software.
You can read details about the hardware design, including a circuit schematic. X-10 RF circuits were removed, making this a low-power sensor.
Other Hardware
Other sensors and hardware have been developed or integrated in AlarmNet. Some prototypes are shown below.
