The Internet Power Line Adapter - University of Queensland

Home Automation, Power Lines and the Internet Quenten Alick
add some external EEPROM to the microprocessor. One option for this would
be the Microchip 25C080 serial EEPROM which contains 8k of EEPROM,
arranged as 1024 x 8.
This EEPROM uses an SPI interface. Although this could be connected to the
SPI interface on the microprocessor, it is preferred that this SPI be devoted to
communicating with the P300. Port pins can still be used to access serial
EEPROM by “bit-banging” the interface. The final fallback is to use a
MC68HC11E2 microprocessor without the serial EEPROM. The MC68HC11E2
is identical to the MC68HC11A1 except that it has 2048 bytes of EEPROM. The
drawback is that the recording time for the power meter will have to be reduced.
4.5 Power Supply
The power supply for the client and server was relatively straightforward. The
Intellon PIII interface chip requires a 10V DC supply and the microprocessor
and the P300 network chip require 5V DC supplies. These are the only two
requirements of the power supply. Since both the adapter and the controller need
to be plugged into the 240V AC mains supply for the communications, this also
provides a simple way of powering the two devices.
The Intellon development boards required the use of a separate wall adapter that
stepped the 240V AC mains supply down to 12V AC. From this supply, a diode
bridge and capacitor were used to rectify the AC signal to a DC one. From here,
two voltage regulators were used. The first was an LM2940T-10, which gives
10V from 14-16V. From the 10V supply a LM7805 voltage regulator was used
to provide the 5V supply. These regulators can supply sufficient power for the
circuitry.
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