Introduction
The HomeNet system is designed to provide convenient and central control over a wide variety of home appliances through a local wireless network. The system achieves this via an extremely simple wireless network involving only a PC, a PC connector, and various controls that attach to appliances. The PC runs the primary program that displays information on, and allows one to send commands to home appliances. It sends commands through a com port connection to the PC attachment device. This device then uses radio signals to send messages to the outlying nodes that directly control appliances. These nodes are also capable of responding with information which is used by the PC to update the state that each of the appliance nodes is in.
Both the PC connector and the appliance nodes are controlled using Atmega16L 8 MHz microcontroller processors. These microcontrollers offer more than enough processing power and speed to achieve all the functionality that is required, as well as being extremely cheap. We chose to use the com port as the connector between the PC and attachment because it offers plenty of bandwidth, is often free on the PC, and because the STK 500 test board on which the microcontroller is mounted offers a com port connection for both programming the microcontroller and for data flow.
In our original proposal, we envisioned a system that could also be remotely controlled through the use of a mobile device, such as a PDA, to enable the user to manage the household environment while away. However, we quickly realized that this system would be too broad to complete in a Master of Engineering project, we chose to create a scaled down prototype for our project. For the prototype, we decided to attempt to make the core structure, the Master Node and PC program, as well as at least one appliance node type. The most basic node type is one that simply controls wall power, so we decided to make at least two of these. Later on we decided to slightly expand our goal to actually make it a light control that, in addition to on/off functionality could also dim the light. We were able to complete all of these goals by the end of the project, and so would deem it a success.
HomeNet stands apart from other home automation solutions in that it is completely wireless and will work with existing appliances. Other commercial approaches have been taken, such as X10 and using Bluetooth devices, but neither of thee approaches are as convenient as the HomeNet system. Additionally, HomeNet will provide centralized control through a PC that neither of these systems can support. These products require that existing wires (such as power lines) are used or that all the appliances to be controlled be repurchased with wireless control built in. Utilizing existing wires means that there is an inherently noisy environment which will limit reliability and replacing all existing appliances could never be a cost-effective solution. The HomeNet solution overcomes both of these problems by providing an interface to control existing appliances and using its own RF network to be both convenient and reliable.