The Internet Power Line Adapter - University of Queensland

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Home Automation, Power Lines and the Internet Quenten Alick Chapter 4 4.1 Hardware Implementation This chapter will look at the hardware design decisions that were made for the adapter. The design decisions will be examined with reference to the specifications mentioned in the previous chapter. 4.2 Power Lines Network Controller It had already been decided to use a CEBus compatible power lines network controller. Of the companies that offered CEBus compatible network chips, the Intellon and Domosys chips seemed to be the most suited. With the only requirement that the system be simple, the main determining factor became the cost of purchasing a development kit. In the end, the Intellon P300 kit proved to be the most suitable. It was the cheapest solution available that provided two development boards with the provision for the use of either a MC68HC05 microprocessor or another alternative microprocessor. The alternative Domosys development board had the option of either a combined microprocessor with network chip or a standalone network chip. However, both these options also required the further purchase of a circuit to interface the chip to the power lines. With the Intellon boards, the power line interface circuitry, network controller and microprocessor were all in the same development kit. This made the Intellon board cheaper. The P300 development kit made use of three separate chips. See figure 4-1 for a picture of the development board. These were the microprocessor, a MC68HC705C9, the P300 power line network controller and the P111 media interface IC. The P300 chip takes information from the microprocessor and - 18 -
Home Automation, Power Lines and the Internet Quenten Alick converts it into a CEBus compliant analogue signal. This output signal is in the form of the chirps mentioned earlier. However, it is not possible to directly couple this signal to the power line power signal. It must first be filtered and amplified before it can be coupled. The P111 is responsible for the amplification of the output signal. Discrete components are used to filter the input from the P300 to the P111 as well as the signal from the power line, which is sent directly to the P300. Figure 4-1 P300 Evaluation Board 4.3 Power Measurement & Switching Proper measurement of power for an appliance can be a difficult proposition. An entire thesis could be written on the topic of accurate power measurements itself. For this reason, a relatively simple circuit was designed to measure the power consumed by the appliance connected to the adapter. - 19 -
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The Internet Power Line Adapter - University of Queensland

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