29-12-2012, 06:18 PM
Power Line Communication Based Automation System Using a Handheld Wi-Fi Device
1Power Line Communication.pdf (Size: 1.12 MB / Downloads: 77)
Abstract
An open source automation system for controlling
electrical appliances using power line communication is presented
here. Control messages are sent over Wi-Fi network from a
Wi-Fi device to the micro-controller which then couples the
messages to the power lines. Ubiquitous power lines are used
as physical media to transmit data over 220V/50Hz signal to
control appliances/equipment. The data from the microcontroller
is coupled onto the power lines using a PLC (Power Line
Communication) modem and DCSK (Differential Code Shift
Keying) modulation technique is employed to transmit data.
Each receiver unit consists of PLC modem plus microcontroller
and can be connected anywhere in the power line network. The
receivers have addresses assigned to them and only respond to
the commands sent to them by the transmitter PLC modem.
The receiver unit controls the flow of electricity to the socket.
The entire system is devoid of a computer to save power and
make it low cost. Use of open source hardware, Power Line
Communication and micro-controller collectively reduce the cost
of controlling appliances remotely.
INTRODUCTION
Automation essentially involves leveraging the power of
technology to reduce the dependency on human presence
and decision making for any process. It leverages different
electronic equipment (either standalone or interlinked with
appropriate applications) to control different parameters of any
process. In these days of energy scarcity, it is prudent to save
energy in every way possible. It is paramount to make such
systems as easy to use as possible so that people can use their
appliances in a smarter way to save energy. It also enables
people to be more energy conscious by enabling them to have
a real time status of electric appliances.
Automation also helps reduce peak hour power consumption
by enabling people to turn off appliances at will remotely.
This facilitates a constant power supply by having varied
pricing policies for different times of day and night. Aim
of this project is to simplify the process of human-machine
interaction through the use of a generic interaction system
and to make things around us smarter and interactive. We
envisaged building an interaction system that would allow us
to interact with the physical/analog world.
SYSTEM OVERVIEW
A Wi-Fi enabled device is used as means of input. An iPod
Touch is used for this purpose, which provides the user with a
touch screen interface facilitating ease of use. A Wi-Fi network
is first setup using a wireless router. The micro-controller
connects to the wireless router through an Ethernet interface
card. The Ethernet interface card and the micro-controller
communicate over a Serial Peripheral Interface (SPI) bus. An
application on the device consists of 3 buttons and 1 slider and
enables us to send messages in Open Sound Control format.
OSC (Open Sound Control) protocol is used to communicate
between the iPod Touch and the micro- controller over a
Wi-Fi network. When a user presses a particular button,
specific messages are sent over the Wi-Fi network to the
micro-controller which decodes the messages. The microcontroller
converts these messages into simple control signals.
The commands sent by the micro-controller to switch ON/OFF
an appliance are not sent directly to the appliance, but rather
these commands are broadcasted over the power lines using
a Power Line Communication (PLC) transmitter. The microcontroller
sends data to the PLC modem using UART protocol.
POWER LINE COMMUNICATION (PLC)
Power Line Communication is a technology which uses
power lines as physical media for data transmission. PLC
offers a no new wires solution because the infrastructure has
already been established. PLC modems are used for transmitting
data at a rapid speed through a power line in a house,
an office, a building, and a factory, etc. Here, the existing
alternating current (AC) power wires serve as a transmission
medium by which information is relayed from a transmitter or
control station to one or more receivers.
OPEN SOUND CONTROL
Open Sound Control (OSC) is a protocol for real time
communication between computers, sound synthesizers and
other multimedia devices which are optimized for networking
technology. OSC is touted as the next generation replacement
for the MIDI format. OSC is a transport independent protocol
which means that it is a format for data that can be carried
across a variety of networking technologies like USB, Firewire
and Ethernet. OSC offers bandwidth greater than 10mbps
compared to MIDI‘s 31.25kbps.
IMPLEMENTATION
An iPod touch is used for sending control commands to the
micro-controller over Wi-Fi using OSC protocol. OSC can be
used to encode integers, real numbers and text. Using the OSC
protocol over the device‘s built-in Wi-Fi connection, the OSC
application communicates with other compatible hardware and
software nodes over the network. Any client which supports
the OSC format could be used, for example Mrmr, Touch
OSC, OSCemote. The iOSC application on the iPod allows us
to send customized messages in the OSC format over Wi-Fi.
The interface consists of three buttons (to send high and low
values) and a slider for pulse width modulation.The sliders can
be used for varying brightness of light bulbs or for controlling
the speed of fans. This application will convert the button
presses into predetermined OSC messages and will append
specific IP and port addresses to the message. A router is
used in the setup to host a local wireless network. The Ethernet
interface card connected to the microcontroller is initialized to
a specific IP address so that it is in the same network as the
iPod. The IP address and port addresses are set to be the same
in both Ethernet interface card and in the iOSC application.
APPLICATIONS
Agriculture, Soil monitoring, Weather station reporting,
Remote data acquisition, Power line fault monitoring, Home
and industrial automation, Home networking, Automatic meter
reading systems, Real time monitoring of energy consumption,
Building management solutions.
Use of the system shown above for the implementation of
a particular application is explained briefly- The increase in
public demand for energy creates the need for Energy Saving
and Energy Management procedures. Utilities can lower cost
by reading meters remotely, charging according to time of use
or according to level of power used, automating power failure
recovery and lowering the investments in new power stations.
Utilities can increase revenue by offering more services to the
customers (besides just offering power).
RESULTS AND CONCLUSION
The system was tested using a Power Line transmitter
and two receivers connected to appliances kept at different
locations but within the same electric network. The appliances
were controlled by sending specific commands to trigger the
relays which were the switch link in the circuit. The signals
do not get transmitted through the MCB so the signals sent
from one house don’t interfere with that of the neighbor’s.
The response to commands sent by the iPod interface had a
lag of 0.6 to 1 second.