School of Electrical Engineering

1
Wireless Sensor Networks Platform
2005
Authors Arnon (Nonie) Politi and Tomas Renard
Djunaedi Supervisor Dr. Saeid Nooshabadi
POWER METERING APPLICATION Introduction This
application has been developed in order to
demonstrate and test the functionalities of the
hardware platform. This application utilises a
series of current sensors attached to different
power points in a home or industrial environment
in order to monitor the total energy consumed by
different electrical appliances attached to these
power points. Current Sensor
ABSTRACT Wireless sensor networks is a rapidly
emerging technology that will change the way we
interact and control our environment. The purpose
of this project is to design and produce hardware
platform as a basis for developing wireless
sensor networks applications. Importantly, this
platform must be able to satisfy the triple
constraints of cost, size, and power imposed on
wireless sensor networks devices. It is hoped
that this platform could eventually form the
basis of further research into the technology at
UNSW and beyond. Additional aspect of this
thesis involves the development of power metering
application based on the produced hardware
devices. The application will measure and log the
power consumption of different household or
office appliances and transmit collected
information wirelessly to a base station.
The design of the current sensor module is based
on U_RDs CTL-6-S32-8F-CL clamp-on current sensor
attached to the active wire of a modified power
board (see image above). Current drawn by
appliances connected to the power board will
cause the current sensor to generate a
proportional voltage across its lead. This small
AC voltage is then passed through an envelope
detector (low pass filter) to produce a
relatively constant DC voltage that can be easily
measured by the ADC on the microcontroller. Experi
mental Setup
School of Electrical Engineering
Telecommunications
HARDWARE DESIGN Modular Design Concept Design of
the wireless sensor network platform is
undertaken with hardware modularity as primary
consideration. Modularity would allow for maximum
flexibility which is crucial for the devices
intended use as a development platform for
wireless sensor networks applications. The
platform comprises of modules that can be
classified into the following categories 1.
Mainboard Module 2. Sensor Module 3. Peripheral
Devices 4. Power Supply Module
To demonstrate the flexibility of the Wireless
Sensor Networks module, the path from the edge
node to the base station is dynamically
determined. Every intermediate node is set to
periodically broadcasts a short packet at a fixed
power level. Through the RSSI (Received Signal
Strength Indicator) functionality of the
mainboard, each edge node can determine which
intermediate node is closest to it by comparing
the signal strength from the received broadcast
packets. Data collected by the base station is
then forwarded to a PC through a serial link for
display or storage. The following table is a
sample output from the application as displayed
on hyperterminal.
Central to this project is the design of the
mainboard module which has the following
features ? CC1010 microcontroller running at
14.7456 MHz ? 433 MHz RF transceiver at up to
76.8 kbauds ? 1 Mbit onboard flash memory
accessible via SPI ? Three 10-bits Analog to
Digital Converters ? 17 General Purpose I/O pins
ENGINEERING _at_ UNSW