Design of a wireless platform for wearable and home automation applications
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In the recent past, a great deal of attention has been given to wireless sensors. Wireless sensors enable a multitude of applications such as environmental monitoring, medical care, disaster response, home automation, urban scale monitoring, gaming etc. These small, low-power, multifunctional sensors includes sensing, data processing and communication components representing a significant improvement over the traditional sensors. The two attractive wireless sensor applications investigated in this thesis are wearable sensors for bio-medical applications and a ZigBee wireless network for home automation applications. The targeted bio-medical application is bone strain monitoring. The current setup to collect strain data is composed of a data acquisition unit connected to a bench top load instrument. For accurate measurements the lab animals have to be sedated and immobilized in the current setup which is also bulky. A telemetry unit equipped with strain gages designed for implantable measurement of bone strain was designed to address this problem. The measurements collected by an implantable telemetry unit are of high interest to orthopedic researchers who wish to know the load acting on an orthopedic implant and hence to help guide the rehabilitation outcomes in a patient. This thesis describes two small telemetry units with multiple configurable sensor channels which can be used to sense resistance and voltage. Thus, the designed units can be used in home energy monitoring applications as well. The units have low power consumption and were designed using off-the-shelf components. Their dimensions are 24 mm x 13 mm and 10 mm x 10 mm. The sensor signals are multiplexed, modulated and transmitted to a remote computer by means of a radio transceiver. Besides measuring strain integrated levels the telemetry units can also measure acceleration in 3 axes. Wireless battery charging is another feature that was included in our design which is a key feature for surgically implanted devices. To show that our telemetry units has comparable accuracy and compactness to the current setup, we present the readings from both setups. A ZigBee wireless sensor network to monitor and control home appliances was designed and successfully tested. A central control unit is the coordinator which sets up the network and configures the ZigBee network parameters. The battery powered sensors are configured as end-devices which periodically report sensor data such as light, temperature, accelerometer and energy consumption values to the coordinator. Any home appliance limited to less than 10 Amps in the ZigBee network can be turned on or off from the central control unit. With bidirectional communication achieved between the central control unit and the end-device, we were able to achieve a home automation system.
Table of Contents
Introduction -- Background -- Telemetry unit architecture -- Data collection and results -- Conclusion and future work -- Appendix A.1. Four layer PCB layout of the eight channel telemetry unit -- Appendix A.2. Four layer PCB layout of the four channel telemetry unit