Literature Review
ECM3401 – Final Project
David Gardner
Candidate Number: 043265
University of Exeter BSc
Computer Science
I certify that all material in this dissertation
which is not my own work has been identified.
26th November 2009
CONTENTS
1
2
3
Introduction ................................................................................................................................................................ 3
1.1
Background ................................................................................................................................................................ 3
1.2
Aims ............................................................................................................................................................................ 3
Current Home Automation .......................................................................................................................................... 3
2.1
What is Home Automation? ....................................................................................................................................... 3
2.2
Why is it important? ................................................................................................................................................... 3
2.3
Current Home Automation Systems .......................................................................................................................... 4
2.4
Problems with the Current Systems ........................................................................................................................... 6
2.5
How devices are controlled ........................................................................................................................................ 6
Networks and Power line Technology ......................................................................................................................... 7
3.1
Networks .................................................................................................................................................................... 7
3.1
X10 ............................................................................................................................................................................. 8
3.1.1
How X10 is used to send commands.................................................................................................................. 8
3.1.2
X10 Device Commands ...................................................................................................................................... 9
3.2
3.2.1
3.3
4
Insteon ..................................................................................................................................................................... 10
How Insteon Sends Commands........................................................................................................................ 11
Comparison of Technologies .................................................................................................................................... 11
Chosen Technology .................................................................................................................................................... 12
4.1
Development Decisions for my Home Automation System ..................................................................................... 12
4.2
Justification .............................................................................................................................................................. 12
Overview ........................................................................................................................................................................... 12
Bibliography ...................................................................................................................................................................... 13
Appendicies ....................................................................................................................................................................... 16
Appendix 1............................................................................................................................................................................. 16
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1
INTRODUCTION
1.1
BACKGROUND
Home Automation is a concept that has been developing reasonably slowly when you compare it to how other
technology such as televisions have progressed. Whereas other technologies such as high-definition televisions
have developed and become much cheaper (around 20% per annum (1)), home automation is still generally
quite an expensive and exclusive concept for most people. This report will look into what Home Automation is
and what current technologies exist. I will look at how technologies are currently implemented and the groups
of people that will use the technologies. I will look at the use of automation as a disability aid as well as it just
being a luxury within a home.
1.2
AIMS
In this report I aim to choose the appropriate technologies and methods for when I create my implementation
of a Web-based Home Automation System. To do this is will look at current Home Automation
implementations and the technologies that are currently available for creating web based client-server
systems. I will also look at other technologies which I feel will be appropriate for my project that might improve
on the existing systems available.
2
CURRENT HOME AUTOMATION
2.1
WHAT IS HOME AUTOMATION?
Home Automation (also referred to as Domotics) is “the use of one or more computers to control basic home
functions and features automatically and sometimes remotely, an automated home is sometimes called a
smart home” (2) . Home Automation can be used for a wide variety of purposes; from turning lights on and off
to programming appliances within a home and the programming of timers for these various devices. Home
Automation is often used as a luxury convenience system within a home and often it is expensive to have
installed due to their relative exclusivity in the current market (3). As Home Media devices become cheaper,
Home Automation is a technology that more people will be looking into to install in their house.
2.2
WHY IS IT IMPORTANT?
Home Automation (HA) is quite a broad area and therefore has a variety of uses. Some areas are very
important and can greatly improve the quality of life for individuals, whilst other aspects of HA are used for
convenience rather than an essential item. Starting off with the more essential aspect of HA are security
aspects. Cameras and sensors can be connected to a HA system. These can be used to monitor and record
activity around a building/house and can make remote monitoring much easier. This can then make the
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technology of burglar alarms much more complex as they not only recognise movement with sensors but they
can also store and relay video images for the owner (4) to then show the police if necessary.
Another use for HA is with the elderly and people with impaired physical mobility (5). Tasks that are simple for
some people are much harder if you are less mobile can be made much easier using an automated system.
Automated systems can be linked to motors and switches to perform tasks controlled on a simple control
panel. For example the opening and closing of curtains in a room could be controlled by a remote control. The
most dominant uses of HA are with home lighting, multimedia and smart home appliance control. This tends to
be the more exclusive market and often quite expensive.
Home Automation will only be adopted if it is at least as easy to use as the original task in which it is replicating
(6). For example if switching on a light via a HA system is more complicated than pressing a button on a wall
then there is arguably no advantage to having the device automated and it might just promote user
aggravation.
HA software in Australia is being used to shut down lighting and devices in homes from their computers and
mobile phones. A pilot study from the company who produced the software showed that an office building was
able to cut its energy consumption by 25 percent (7). With the constant strive to create a greener planet, HA
could certainly help us in doing so.
2.3
CURRENT HOME AUTOMATION SYSTEMS
In the past many distributed audio systems within a house have consisted with a large number of wired remote
controls around a house which controls a central CD player or Radio. The problem with these systems is that
there is one audio source for many rooms and each room cannot listen to a different CD concurrently. For this
reason many of the more modern systems are computer based systems.
Most of the HA solutions that are currently on sale use specialist hardware both to store the media and to
distribute it. An example is the Sonos™ Wireless Music Centre (8). The Sonos™ system uses your current home
computer (or a dedicated computer to store your music), Sonos™ ZonePlayers in each of the rooms you require
music which then have speakers attached and a graphical remote control for each device.
Figure 1: Sonos™ Wireless Music Centre Components (8)
This system is designed so that it takes only basic computer skills to set up and therefore saves the user money
in not having to pay for a professional installation of the product. It uses wireless technology for the
ZonePlayers, Controllers and the Computer to communicate and therefore doesn’t require the inconvenience
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of installation of network cabling to the building. I have had a demonstration of the system and it is very simple
to use (very similar to navigating an iPod if not a little simpler). The drawbacks with the Sonos™ system is that
it only covers music streaming within a home and does not control lighting and other appliances. The other
disadvantage is the system costs upwards of £650 (9) (November 2009) for the smallest room package and that
doesn’t include the cost of the computer that acts as a server if you don’t already have one. Another similar
solution to the Sonos™ system is the Cambridge Audio incognito system (10). This uses more dedicated
hardware and has more wired components compared to the Sonos™ system. More of the components are
integrated into walls which makes a cleaner finish but are harder to setup and move to a different room or
house. The Cambridge Audio has optional modules to allow video to be streamed as well as music. Neither of
these system offer remote web access to the system and they cannot control lighting or other appliances. The
next few products I will look at offer increases functionality beyond the scope of music and video.
There is a selection of companies in the United Kingdom that offer more bespoke systems for their customers.
An example company that I have been looking at is ‘Cyber Homes’ (11). They offer bespoke HA solutions for
individuals and families. They consult with the client and discover their needs then come up with a selection of
proposed solution and prices. They offer automation is Multi-room Audio and Visual, Automated Lighting, CCTV
and Security, Heating and Air-conditioning and Occupancy Simulation. Occupancy Simulation is achieved by
using the other methods of HA they offer to achieve a realistic simulation that a house is being lived in, aiming
to achieve a house that appears to be occupied, and therefore less of a target to burglary (12).
The advantages with companies such as Cyber Homes, is that they can offer solution that are tailored to you
need rather than having to adjust your home to work with the technology. The problem is that using bespoke
solution gains considerable extra cost. A large proportion of this is paying for the design consultancy for
designing your system and also the installation costs that you will incur. Although the bespoke systems are an
expensive option, there is very little input required from the client apart from their wishes on what they want
the system to do, not how they are going to do it. This is why very little technological experience is required for
this option.
At the other end of the spectrum, there is DIY (Do-it-yourself) Home Automation. This option is quite different
to the bespoke systems that companies such as Cyber Homes have to offer. These can still offer a vast range of
control within the home, the difference being that this method is often very limited by a fixed amount of
available funds to equip the home. It is also necessary to be technologically minded as the research into
components needed and their installation and maintenance all has to be carried out by the home owner
themselves. Websites such as DIY Home Automation (13) offer consumer advice to people trying to set up a
system themselves. Sites like these are generally written to give friendly advice, rather than a business, so may
not necessarily contain the most up to date information, or even the best practices in which to design a system.
The authors of the sites are usually enthusiasts rather than experts in the field. This is why it is necessary for
the home owner to have a fair amount of technical knowledge or be technically minded, to help them siphon
out the best information to allow them to create a system that meets their needs.
The type of HA that is usually referred to in DIY HA is usually controlled by a computer (usually an existing
computer within the home) and signals are usually sent through both wired or wireless Local Area Networks
(LANs) . Many of the examples I have looked at have used X10 (14) for sending commands along power lines. I
will talk more about X10 in the next section of this report. Lighting and Appliance can then be controlled by
remote controls or by a computer connected to the network. The software for use in these systems varies from
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free open source software such as MisterHouse (15) to more costly solutions such as PowerHome2 which costs
$99 (on 10th November 2009) (16).
2.4
PROBLEMS WITH THE CURRENT SYSTEMS
The systems that I spoke about in the ‘Current Home Automation Systems’ section all have their own
advantages and disadvantages, but I mainly concentrated on their disadvantages. The purpose of this section is
to outline some of the major downfalls to the systems and mark out key points that make a system efficient
and useful and summarise these so as I can best address these issue when I come to develop my own Home
Automation System.
The first issue to look at is the ease of installation. Systems like the Sonos Media system are relatively straight
forward to install. They don’t require much (if any) additional wiring to be put in the house and this therefore
limits disruption to the home with installation. It also means that the system is not tied down to having to stay
in the rooms in which it was initially installed as the components are relatively easy to relocate. Other systems
such as the bespoke systems on offer by companies such as Cyber Homes hardwire components and require
cabling routed throughout a house. Often control panels are sunken into the walls to give a nice sleek finish.
This does however limit the ease of relocating components significantly. DIY Home Automation usually consists
of message receiver modules (X10 or Insteon for example). I will discuss the different types of receiver modules
in the ‘Network and Power line Technology’ Section. The receiver modules can be swapped around devices
easily and the whole device and its receiver can easily be moved to other locations around the house.
The second clear disadvantages to some of the systems are cost. If money is not object then you can get some
really great systems, but seeing as this is not the case for many people, budget is a key factor. If a product is to
become successful it needs to be financial accessible to the mass market. Bespoke HA systems are not an
option for a lot of people, therefore affordable plug and play and easily configurable solutions need
developing, even if they do have slightly less functionality than the bespoke systems. According to Kirchhof and
Linz (6) they say that for HA to be successful “home automation cannot require technicians come to the user’s
home to integrate any kind of devices to home networks” (6 p. 325).
The problem with current HA systems is that the HA standards are extremely fragmented (6). The problem with
this is there is no universal standard, and lots of protocols and devices are proprietary and this makes it harder
for new systems to be developed as quickly as we would like (17). When I design my system I will either have to
create something that “encompasses all existing technologies” or I need to create a system that can be
integrated with existing technologies and standards. I will analyse this when discussing what technologies I will
use later on in this report.
2.5
HOW DEVICES ARE CONTROLLED
In the examples I have used so far, the majority use a remote control of some sort to control the devices. The
Sonos system uses a graphical remote which has real-time user interface to navigate the system. The bespoke
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systems often use a similar type of remote control although on more expensive systems, they can be touch
screen displays embedded into a wall near other commonly used switches like light switches.
The advantages to a DIY home automation system is that you can make the system as you need it and you
don’t have to pay for functionality that you don’t need.
To best get an idea of how home devices communicate we need to look at Networks and Power line
Technology.
3
NETWORKS AND POWER LINE TECHNOLOGY
3.1
NETWORKS
Now I have got this far, I am going to narrow down to creating a type of DIY Home Automation that is easy to
implement and change for the user for my project. To do this I will need to look into various types of
communication methods.
As high speed internet connections have become common place in homes, it has never been a better time to
control you HA system remotely across the internet. One of the key aims for my system is for it to be able to be
controlled over the internet. With an average download speed of 3.6 megabits per second in the UK (18) we
can do more bandwidth hungry tasks than we used to be able to, making the scope for HA even greater.
There are many networks that usually exist in home already. Local Area Networks (LANs) and Wireless Local
Area Networks (WLANs) are more obvious networks that can be used to automate your home, whereas some
others are less obvious. The less obvious networks are Power line networks and Phone line networks.
A LAN network usually makes use of twisted pair cables with Category 5 (Cat5) and Category 5e (Cat5e) being
the most commonly used. New faster Category6 and Category7 cables are being developed but are not in wide
enough use within homes currently and don’t currently have approved standards (19). Cat5 and Cat5e offer
data of 100 Mb/s (20) and 1000 Mb/s (21) respectively. They provide reliability and quick connections and are
arguably the best choice for networking devices together. The disadvantage is these cables have to be run
around the house to each device. Although the cabling itself is reasonably inexpensive the cost and
inconvenience of installation into an existing home can work out to be quite expensive. It is relatively cheap to
install the cable when building a house and it is become more and more common for new homes to come with
Cat5 cables already installed. This is because cables can be installed at the ‘first fix’ electrical stage when the
walls aren’t fully in place and cables can be more easily routed, then the rest of the interior of the house is built
around the cables.
To overcome the problem of installing networks to existing houses, wireless networking within the home is
often used. It is very simple to add a wireless network to a house as usually one wireless transmitter is
sufficient to be able to deliver a wireless signal throughout a house. Most laptop and many mobile devices now
come with Wi-Fi as standard so they can then connect to the wireless transmitter. The issues with wireless
networks are their unreliability, as sometimes connections can drop or become slow. There are also other
security issues that are not an issue on a wired network. Wired networks don’t require password control
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usually as to be able to connect you have to physically plug into the network, and those network plugs will be
in your home, whereas with wireless some of the signal may pass into neighbouring properties so password
protection is required to stop unauthorised access. Wireless security has become better in the last few years
with the move from WEP encryption to WPA; however it is still not one hundred percent secure (22). Speeds of
Wi-Fi have also improves with 54 Mb/s being common and new faster technologies capable of achieving up to
240 Mb/s (23) although speeds decrease with distance from the transmitter.
When looking at the vast majority of home automation we just want to send signal to devices rather than
stream data (unlike the Sonos Audio Streaming System). Often music and video streaming are dealt with by a
separate system that then in turn is controlled by a house HA system. I am going to look at the HA control
systems rather than media streaming systems so power line communication is very suitable. Power line
communication can be used to link up Ethernet cables wirelessly in a house but there are also other protocols
that have been developed more specifically for use in home automation. I am going to look at the two most
popular technologies and compare them, one of them with then be the basis in which my implementation of a
HA system will operate on. I am going to look at X10 (24) and Insteon (25) power line technologies.
3.1
X10
X10 is the standard used to control other X10 connected devices using the building’s built in electrical system
to transmit the signals (24). Lights and devices can be plugged into X10 modules such as the ones sold by
Habitek (26). The modules are the interface between the devices and the power lines which receive the
commands from an X10 control device. This can be a basic device such as a remote control (27) delivering X10
commands to the relevant X10 modules or a controller that is software based and runs on some sort of
computer. An example of such software is X10 Controller (28). It uses a graphical user interface to control your
X10 modules both locally on your computer and across the web. It runs as a windows service which allows
command to be issued when the computer is on, but the user isn’t logged on (28). The only problem with this is
that it has to be used on Windows and other types of operating systems, such as versions of Linux and Mac OS
will not run the program. Computer controlled X10 controllers allow more flexibility than pre-programmed X10
controllers and can be adapted to your needs.
3.1.1 HOW X10 IS USED TO SEND COMMANDS
The theory of transmitting commands to the X10 devices consists of transmitting byte codes along a power
line. To connect devices to a computer we need to use a two-way interface called CM12U (this is the U.K 240v
version of 110v CM11A which you will see widely used in HA in the US (29).) connects to the Computer and
then to the power line.
AC (alternating current) is the current that we have in our homes in the UK. AC has a “current that changes
polarity or direction, respectively, over time” (30). This type of current forms a sine wave as shown in Figure 2.
Commands are sent along the power lines and “transmissions are synchronized to the zero crossing point of the
AC power line”.
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Figure 2: Sine Wave
The zero crossing points are when the sine curve crosses the x axes (as marked by the red crosses above). The
transmitter (in our case CM12U) provides a square sine wave (31). “The rate of changing direction (from
positive to negative) is called the frequency of the Alternating Current and is measured in hertz (Hz)” (32). In the
UK our electricity is delivered to our homes with a frequency of 50Hz (32). This means that one cycle/sine wave
takes 1/50 seconds, which is 20 milliseconds.
X10 transmissions are sent at the zero crossing point of the AC Sine Wave. The aim should be to transmit the
data with a 200 microsecond threshold of the zero crossing point (31).
X10 transmissions are made up of a series of binary values. “A Binary 1 is represented by a 1 millisecond burst
of 120kHz, at the zero crossing point and a Binary 0 is represented by the absence of 120kHz” (31).
3.1.2 X10 DEVICE COMMANDS
X10 Device Commands consist of a bit ‘Start Code’, followed by a ‘House Code’ (denoted by letters A-P but
transmitted in Binary), then followed by either a ‘Device Code’ (denoted by numbers 1-16 but transmitted in
Binary) or by a ‘Function Code’, then followed by a ‘Function’ bit which is tagged on to the end of the
Device/Function code to let the X10 modules know whether it is an addressing command or a function
command (33). “Except for the Start Code, each bit of data is sent in its true and complement form (Data Data
bar)” (33).
Figure 3: X10 Transmission Format. [Information extracted from (33)].
We first send a message consisting of the Start Code, House Code and Device Code. The next message we need
to send consists of the Start Code, House Code and Function. Each message is sent in full twice, with at least
three power line cycles between each message (31). This does not apply with the dimming commands as then
the messages are sent continuously.
For example if we want to transmit the verbal command “turn on Device 1, in House A” we would send the
following: (Spaces are for ease of reading only)
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The House Code for A is: 0110 The Device Code for 1 is: 01100 The Function Code for On is: 00101
For the rest of the Codes see Appendix 1.
1110 01101001 1010100101
1110 01101001 1010100101
(Power cycle gap of greater than 3 cycles)
1110 01101001 0101100110
1110 01101001 0101100110
Figure 4: Decoding True bit and
complement bit codes
X10 also offers the facility to extend the protocol to allow it to send data. However for my lighting and device
model that I would like to create, I do not need to be able to send data.
3.2
INSTEON
Insteon is a brand name for another alternative to X10. While X10 can trace its beginnings back to the late 70s,
Insteon has only been around since the 1990’s (34). Insteon like X10 “allows devices to be networked together
using the power line or Radio Frequency (RF) or both (25 p. 1)”. Insteon uses modules between each device and
the power line. Each module acts as both a transmitter and a receiver, so no dedicated transmitter modules are
required. Adding more devices to an Insteon network only makes the network more stable as each is acting as
a transmitter, the more devices there are the more links there will be between devices in case of a specific
device failing (25) creating a big network with a mesh topology. Another plus factor to the Insteon technology
is that it is backwards compatible with X10. People who already own X10 devices can use them in their Insteon
network without the need to replace them. Developers at Insteon have looked more deeply into devices and
looking at how they can control air-conditioning and heating systems relatively easily, taking the HA arguably to
the next step past X10. The reason they wanted to develop this product was that they thought that there were
reliability issues with X10 and wanted to improve on the X10 technology (25 pp. 3-4).
Insteon devices don’t use house and device codes. Instead every single device that Insteon make has a unique
number code in which the device can be identified by (25 p. 5). When an Insteon device receives a message it
sends back a confirm command (as each device is also a transmitter). This means you can get instant feedback
to whether a signal has been received rather than just finding the device hasn’t worked or waiting for timeout
errors. Insteon, like X10 is a standalone technology, but Insteon also has the option to be able to expand it to
bridge to other networks such as Wi-Fi LANs, The Telephone network and the Internet (25 p. 6). Like X10 you
can also have an Insteon device linked up to a PC to allow further control over pre-programmed remote
controls.
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3.2.1 HOW INSTEON SENDS COMMANDS
Insteon devices like X10 have to message methods, a standard and an extended message. The standard
message length for Insteon is 10 bytes. “The only difference between the two is that the Extended message
contains 14 User Data Bytes not found in the Standard message” (25 p. 15).
Figure 5: Insteon Standard Message Structure (25 p. 15)
The Insteon messages are much larger than X10 messages; they are as a minimum 80 bits (10 bytes) but 14
bytes longer for extended messages. It does however mean that both the message and the command are
stored together and sent together rather than in two separate messages as they are in X10. Although the
messages in Insteon are larger they are still sent very quickly, so I see this only as a small disadvantage as X10.
Messages also have 1 byte for a Cyclic Redundancy Check (CRC) which is used to check that all the rest of the
message has arrive correctly (35 pp. 26-34).
3.3
COMPARISON OF TECHNOLOGIES
Insteon and X10 are both designed to achieve very similar goals. X10 has been around the longest and there is
a lot of information regarding the technology, both in the form of technical documents as well as user advice
forums. The message signals of X10 are smaller than Insteon and are well established.
Insteon offers a broader scope for development in the future and its mesh network topology should make the
system the more reliable of the two. Insteon is not currently available for sale in the UK yet, although it has
been sold in the US in 110v form for a number of years. The technology is expected to reach the UK but no
dates have been confirmed (36). Insteon prices in the US are considerably more expensive (34), but as Insteon
is not on sale in the UK, it is hard to make a direct comparison.
When writing my own web-based Home Automation application it will be easier to get information on how to
write my own program as there are more existing X10 programs for HA than Insteon ones. Insteon’s greater
flexibility will actually be a negative point for my project as the types of actions I wish to perform are well
within X10s capabilities and the more simple protocol of X10 will be easier for me to implement. One of the
biggest factors is that I cannot currently purchase any Insteon devices in the UK for me to test my system. For
this reason I will use X10.
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4
CHOSEN TECHNOLOGY
4.1
DEVELOPMENT DECISIONS FOR MY HOME AUTOMATION SYSTEM
As discussed in the previous section (3.3), I am going to develop my system using the X10 power line
communication standard. There are two X10 APIs in the Java programming language. One was developed by
Jesse Peterson (37) and the other by AgaveBlue (38) and provides the interface for Java programs to
communicate with X10 devices. This means that I will not have to program the exactly timing and sending of
bits along the power line, but create and send the X10 messages the X10 API. This is the AgaveBlue version of
the API and it has been used in projects such as OpenRemote (38).
4.2 JUSTIFICATION
Using the API already available in Java will enable me develop a feature rich application without having to
devote all my time to developing complicated X10 transmission methods. I aim to have an easy to use
computer interface that is easily understandable by a wide range of ages. Each task in the HA system should be
as easy as the original task in which it is replicating. I must also be web accessible and run on a variety of
devices.
I have chosen Java as my development language, not only as it has an X10 API but because there are a lot of
Java virtual machines for different devices. This will allow my interface to run on a variety of devices from
Home Computers with a variety of operating systems to a large number of mobile phones. Mobile devices with
web/network access are great devices to use as controllers for the systems as they are something that most
people carry with them. This will then able them to check and control their system without being tied to having
to use a PC.
OVERVIEW
This report has allowed me to look at the existing products in the market and how they can help make our lives
easier. I have also looked into the problems with the current systems and compared the positive and negative
points for each of the systems. I looked deeper into some of the communication methods that are used with
the view on them being candidate technologies for use in my project.
From my research I then concluded with the main technologies that I will use in my own Home Automation
System. I will use X10 in my system as it is a relatively simple protocol that is ideal for developing a HA system
in the timescale I have. Java will be used as the main language for my system due to its multi-platform
compatibility and its X10 API.
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APPENDICES
APPENDIX 1
http://www.x10.com/technology1.htm
X10.com
(Last
Accessed
14th
November
2009)
[1] Hail Request is transmitted to see if there are any X10 transmitters within listening range. This allows the
O.E.M. to assign a different House code if a "Hail Acknowledge" is received.
[2] In a Pre-Set Dim instruction, the D8 bit represents the Most Significant Bit of the level and H1, H2, H4 and
H8 bits represent the Least Significant Bits.
[3] The Extended Data code is followed by 8 bit bytes which can represent Analogue Data (after A to D
conversion). There should be no gaps between the Extended Data code and the actual data, and no gaps
between data bytes. The first 8 bit byte can be used to say how many bytes of data will follow. If gaps are left
between data bytes, these codes could be received by X10 modules causing erroneous operation.
Extended Code is similar to Extended Data: 8 Bit bytes which follow Extended Code (with no gaps) can
represent additional codes. This allows the designer to expand beyond the 256 codes presently available. .
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