Miniaturisation of wireless sensor nodes for smart digital home

With the aging of the global population there is a growing number of elderly people needing care with proportionally fewer caregivers and lesser resources to support them. While many older people move into a managed care environment, there is a significant portion that, for various reasons, chooses to live alone. A system has been conceived and developed to provide assistance in caring for the elderly living alone that uses a network of wireless sensors to monitor the appliance usage of such a person. In order to detect the usage of appliances the sensor nodes measure the current that the appliance is using and report this information to a master node via a wireless communication link. If the usage pattern does not fit within a set of predefined rules an alarm can be raised. While such a system has been tested as a proof of concept system, this work looks to miniaturise the sensor nodes and the master unit so that they can be more easily used and accepted in a domestic environment. The required functionality for the sensor nodes includes a current sensor, wireless transceiver, power supply, microcontroller and user interface. The evaluation of suitable current sensors has been done and the details of the final hardware and software designs are presented. The design of the sensor and master node firmware is outlined and the development of the PC based software that controls the system is presented.