An Internet-based sensor network and its applications
In recent ten years, Internet already became part of our daily life. As part of Internet suite, Ethernet is the most widely deployed network. It is available in many offices and industrial buildings. Ethernet is based on IEEE 802.3 standards, which provides reliable network connection and data transmission services and ensures interoperability. Internet will also solve the problem of remote communication with the sensor applications. Once the sensors are connected to an Ethernet network, they can be monitored or controlled through the Internet. Communication over the Internet removes any distance barrier that may have inhibited remote communication previously. Remote monitoring, control, diagnostics, data collection, and data sharing are all benefits from using Ethernet in sensor applications. However, bringing Internet connection to sensors is a challenging task. Most sensors are often required to be physically small and inexpensive. The microcontrollers used in sensor devices have very limited memory and processing power, comparing with regular PC. This thesis has two targets: the first one is to develop an embedded sensor network which can communicate with local Ethernet networks and with the Internet. I present two solutions: one is "Interneted" sensor, which can be directly connected to Ethernet functioning as a regular web server. Users can use any Internet browser to remotely monitor or control the sensor. The second solution is by adding a fieldbus interface to the "Interneted" sensor, the device will also works as a gateway to other sensors on the filedbus. All sensors share the same Internet connection and users can visit each sensor without noticing the existence of the fieldbus. This solution brings the Internet capability to very simple sensors, removes the resource requirements and provides the flexible interconnection method for sensor nodes. The last chapter of this thesis presents the applications of this Internet-based sensor network, which includes an Internet-based electric field sensing system, web-controlled incubator and stand-alone web sensor. Unlike traditional capacitance sensor which usually works as an independent unit, this electric field sensing system consists of sensing arrays connected by DALI bus. The measurements are collected from sensor nodes in different locations through DALI bus and sent to Internet. The data exchanged between each sensor node and Internet user is transparent. The web-controlled incubator and web sensor applications show the control capacity and friend human-machine interface features of the Internet-based sensor platform.