home automation thesis

Auto-MATE:Intelligent Home Automation Using

Mains Power Communications

byWarren Hastings

Department of Computer Science and Electrical Engineering,University of Queensland.

Submitted for the degree ofBachelor of Engineering (Honours)

in the division of Electrical Engineering.

October 2000

ii

117 Addison RoadCAMIRA QLD 4300

20 October 2000

The Dean

School of Engineering

University of Queensland

ST LUCIA QLD 4072

Dear Professor Simmons

In accordance with the requirements of the degree of Bachelor of Engineering

(Honours) in the division of Electrical Engineering, I submit this thesis entitled

Auto-MATE: Intelligent Home Automation Using Mains Power

Communications. This work was performed in partnership with Mr Shane

Hingst under the supervision of Dr Mark Schulz.

I declare that the work submitted in this thesis is entirely my own except where

appropriately acknowledged and referenced. This thesis has not been

previously submitted for a degree at the University of Queensland or any other

institution.

Yours Sincerely

Warren Hastings

iii

Abstract

This thesis document describes the design, development and successful

prototype implementation of an integrated home automation system titled Auto-

MATE. The Auto-MATE system replaces dumb electrical outlets and switches

found throughout the home with intelligent modules controlled by a central

computer. The new modules connect to form a network using the existing

power lines and the CEBus Protocol. The prototype system contains an

appliance module, a light dimmer module, a motion detector module and

climate sensing modules. The design is unique in that there are presently no

comparable products available in Australia. A set of design specifications and

criteria are developed against which the product implementation is realised. At

the completion of the project the final design is shown to compare favourably

with the specifications and several future directions that the project may take

are suggested. The Auto-MATE system serves as a proof of concept model

for ensuing development.

iv

Acknowledgments

I would like to thank the following people who helped to make this thesis

possible.

Shane Hingst for being without a doubt the best possible thesis partner.

Mark Schulz for sharing his enthusiasm and knowledge of home automation.

Geoff Walker for circuit design suggestions.

Graham Vayro of Vayrotec Pty Ltd for design advice and component

donations.

Andrew Sallaway for cunningly providing a television in the lab under the guise

of a thesis project.

vFor Justine and Jasmine,

I may not be a smart man but I know what love is.

Forrest Gump

vi

Contents

Abstract iii

Acknowledgments iv

Contents vi

List of Figures x

List of Tables xi

1. Introduction 1

1.1 What is Home Automation?...................................................................1

1.2 The Home Automation Maze.................................................................2

1.3 The Auto-MATE Vision..........................................................................3

1.4 Auto-MATE Features.............................................................................4

1.5 Structure and Organisation of this Document........................................4

2. Review of Existing Home Automation Technologies 6

2.1 X-10.......................................................................................................7

2.1.1 The X-10 Protocol.....................................................................7

2.1.2 X-10 Products...........................................................................9

2.1.3 X-10 Summary........................................................................12

2.2 LonWorks.............................................................................................13

2.2.1 LonTalk...................................................................................13

2.2.2 LonWorks Products.................................................................16

2.2.3 LonWorks Summary................................................................17

2.3 CEBus..................................................................................................17

2.3.1 The CEBus Protocol................................................................17

2.3.2 CEBus Products......................................................................21

2.3.3 CEBus Summary.....................................................................23

2.4 European Home Standard...................................................................23

2.4.1 The EHS Protocol...................................................................23

2.4.2 EHS Products..........................................................................23

2.4.3 EHS Summary........................................................................24

vii

2.5 Review Summary.................................................................................24

3. System Design Specifications 27

3.1 The Auto-MATE System......................................................................27

3.2 Design Criteria.....................................................................................28

3.3 System Topology.................................................................................29

3.4 Central Controller.................................................................................30

3.4.1Controller Platform.......................................................................30

3.4.2 Modes of Control.....................................................................31

3.4.3 Additional Services..................................................................31

3.4.4 PC to Power Line Interface.....................................................32

3.5 Mains Power Communications............................................................32

3.5.1 Reliability.................................................................................32

3.5.2 Baud Rate...............................................................................32

3.5.3 Transmission Distance............................................................33

3.5.4 Network Communications IC...................................................33

3.5.5 Microcontroller.........................................................................33

3.6 Intelligent Modules...............................................................................34

3.6.1 Minimum Functionality............................................................34

3.6.2 Light Switch / Dimmer.............................................................34

3.6.3 Appliance Module....................................................................34

3.6.4 Motion Detector.......................................................................35

3.6.5 Climate Sensor........................................................................35

3.6.6 Load Sensing..........................................................................35

3.7 Summary of Design Specifications......................................................35

4. Hardware Implementation 36

4.1 Overview of Hardware Requirements..................................................36

4.1.1 Physical Orientation of Subsystems........................................37

4.2 Mains Power Communications............................................................38

4.2.1 Network Communications Transceiver IC...............................38

4.3 Microcontroller Selection......................................................................42

4.4 Load Control........................................................................................43

4.4.1 Zero Voltage Crossing Detection............................................43

4.4.2 Load Switching........................................................................44

4.5 Load Sensing.......................................................................................44

viii

4.6 Local Control Buttons..........................................................................44

4.7 Power Supplies....................................................................................45

4.8 Temperature Sensing Circuit...............................................................45

4.9 Humidity Sensing Circuit......................................................................45

4.10Motion Detector Circuit........................................................................45

4.11Three Phase Signal Coupling..............................................................46

4.12Remote Voice Activation......................................................................46

4.13PC Power Line Interface...................................................................46

4.14Hardware Design Summary.................................................................47

5. Software Implementation 48

5.1 Overview of Software Requirements....................................................48

5.2 Central Controller Software..................................................................49

5.2.1 CEBus Conformance...............................................................49

5.2.2 The Common Application Language.......................................49

5.2.3 Internet Connectivity...............................................................50

5.2.4 Speech Recognition................................................................50

5.3 Communications Software...................................................................50

5.3.1 Communications Protocol.......................................................51

5.3.2 Communications Driver...........................................................52

5.3.3 PC to Mains Power Interface...................................................55

5.4 Module Application Software...............................................................55

5.4.1 CEBus Conformance...............................................................55

5.4.2 Appliance Module....................................................................55

5.4.3 Light Dimmer Module..............................................................56

5.4.4 Motion Detection.....................................................................56

5.4.5 Temperature & Humidity Sensing...........................................56

5.5 Software Design Summary..................................................................57

6. Performance Evaluation of the Auto-MATE System 58

6.1 Terminal Status of Project....................................................................58

6.1.1 Hardware.................................................................................58

6.1.2 Software..................................................................................59

6.1.3 Mains Power Communications................................................59

6.1.4 Status Summary......................................................................59

6.2 Comparison with Design Specifications...............................................59

ix

6.2.1 Central Controller....................................................................60

6.2.2 Mains Power Communications................................................60

6.2.3 Intelligent Nodes.....................................................................61

6.2.4 Phase Coupling.......................................................................61

6.2.5 Comparison Summary.............................................................62

6.3 Introspective Engineering Performance Evaluation.............................62

6.3.1 Utilisation of Project Tools.......................................................62

6.3.2 Application of Design Techniques...........................................63

6.3.3 Critical Analysis of Personal Performance..............................63

6.4 Performance Summary........................................................................64

7. Future Developments for Auto-MATE 65

7.1 Design Review.....................................................................................65

7.1.2 Voice Command Control.........................................................65

7.1.3 Power Supply..........................................................................66

7.2 Possible Product Extensions...............................................................66

7.2.1 Power Measurement...............................................................66

7.2.2 SMS Text Messaging..............................................................67

7.2.3 Set Top Box............................................................................67

7.3 Summary of Future Developments......................................................68

8. Concluding Remarks 69

References 70

Appendices 74

A. Circuit Schematics and PCB Layouts..................................................75

B. Source Code Listings...........................................................................81

C. CAL Contexts Objects and Methods..................................................101

xList of Figures

Figure 2.1: X-10 Signal Transmission.............................................................7

Figure 2.2: X-10 Transmission Start Code ......................................................8

Figure 2.3: X-10 Transmission Cycle..............................................................9

Figure 2.4: Decorator Dimmer.......................................................................11

Figure 2.5: Two Way Lamp Module...............................................................11

Figure 2.6: Appliance Module........................................................................12

Figure 2.7: Eagle Eye Sensor........................................................................12

Figure 2.8: Powerline Interface......................................................................12

Figure 2.9: Leviton Dimmer...........................................................................16

Figure 2.10:Leviton Occupancy Sensor..........................................................16

Figure 2.11:Infinitelan Controller....................................................................17

Figure 2.12:OSI Model...................................................................................18

Figure 2.13:Spread Spectrum Chirp...............................................................19

Figure 2.14:Manager Plus..............................................................................22

Figure 2.15:Smart Switch...............................................................................22

Figure 2.16:Appliance Port.............................................................................22

Figure 2.17: Sensor Port................................................................................23

Figure 2.18:EHS Development Board............................................................24

Figure 3.1: Auto-MATE Block Diagram..........................................................28

Figure 3.2: Star Topology..............................................................................30

Figure 4.1: CEBus Control Board..................................................................37

Figure 4.2: CEBus Power Board...................................................................37

Figure 4.3: Hardware Block Diagram.............................................................38

Figure 4.4: EK P300 Development Board......................................................39

Figure 4.5: Flow Chart of P300 Initialisation..................................................40

Figure 4.6: Domosip......................................................................................41

Figure 5.1: Communications Flow Chart 1....................................................54

xi

List of Tables

Table 2.1: Comparison of Home Automation Protocols..................................25

Table 2.2: Comparison of Controllers.............................................................25

Table 2.3: Comparison of modules.................................................................26

Table 4.1: Comparison of Microcontrollers.....................................................43

1Chapter 1

Introduction

Home automation is predicted to become a boom industry by technology

pundits including Microsoft CEO Bill Gates [1]. Home automation can provide

additional time for recreational pursuits, monetary savings through power

management and peace of mind that valued homes and contents are being

monitored 24 hours a day. For elderly or disabled people home automation

could prove to enhance their quality of life immensely.

At present, there are still few complete integrated systems available

particularly in Australia, which lags behind other countries in development of

this technology.

There is a potential niche for the development of a reliable, cost-effective

fully integrated home automation system.

1.1 What is Home Automation?

By definition, automation refers to:

The automatic operation or control of equipment, a process, or a system without

conscious thought. [2]

Home Automation provides for the centralised control of lights and

electric devices throughout the home. These devices are controlled by the

occupant or by sensors or timed events. The central controller can also act as

a gateway into the home allowing for remote control and monitoring.

Chapter 1

2

Automation Benefits Include:

Personal Convenience

Security

Peace of Mind

Energy Efficiency

Although not a new concept, home automation has long been the realm of

electronics enthusiasts and hobbyists or separate proprietary devices that

control individual sections of the home. Only recently has there been a drive by

industry to develop integrated systems with a focus on connectivity of all

household appliances and fixtures. The ultimate goal is to produce Plug n Play

type appliances that connect directly to the home automation network and

register themselves with the host controller without any consumer intervention.

1.2 The Home Automation Maze

At present, according to Home Toys [3], there are 6 open and 5 proprietary

home automation standards all vying to be the leading industry standard.

These standards operate over a variety of communications mediums1. This

confusing array of protocols and mediums has resulted in appliance

manufacturers being loath to commit to developing Plug n Play type products

until it becomes apparent which of the competing standards will eventually win

consumer support.

As a result specialist home automation companies have been

concentrating their efforts on developing automated versions of traditionally

dumb devices such as light switches, power points and sensors as a method

of easing the consumer into the automated world.

These products are primarily targeted at American markets and are

therefore either unavailable in Australia due to non-compatible voltage and

frequency, or are priced at around five to ten times the equivalent American

price.

Chapter 1

3

1.3 The Auto-MATE Vision

The goal of this project is to engineer a home automation system that would be

suitable for integrating into new and existing homes. The product would have to

satisfy three minimum requirements.

Functionality

The system has to provide features that appeal to the mass market and not only

to enthusiasts.

Ease of Use

The system must be able to be used by a broad range of people. As a

benchmark a familiarity with Microsoft Windows environment is assumed.

Cost

While cost at the prototype stage is not of paramount concern a light dimmer

that costs $1000 is probably not a feasible product so some budgetary caution

must be observed.

The Auto-MATE vision is then this:

To develop a cheap, reliable, entry level home automation system

In keeping with this vision the final product is expected to consist of a

central controller with some form of remote access such as a telephone or

Internet connection as well as modules for controlling lighting and power loads

typical of those found in an average home. It will include sensors for motion

detection, temperature and humidity. The controller and the modules will have

reliable, two-way communications over the mains power lines. Thus the Auto-

MATE system will follow a No New Wires policy of implementation.

1 Possible mediums are Powerlines, Infra-red, Twisted Pair, Radio Frequency, Coax, Fibre Optic

Chapter 1

4

1.4 Auto-MATE Features

The Auto-MATE vision has been realised over the course of the past nine

months. The details of the design implementation are located in Chapter 4

(Hardware Implementation) and Chapter 5 (Software Implementation). While

full details of the system functionality can be found in Chapter 6 a brief

summary is included below:

Successful adaptation of an existing freeware home automation controller.

Internet access to the system.

Development of a master module to interface the controller to the power

line.

Development of a light dimmer switch with local control and two-way

communication.

Development of a 10A appliance module with local control and two-way

communication.

Development of a climate sensor module with a temperature sensor and

humidity sensor.

Development of a motion detector module.

1.5 Structure and Organisation of this Document

This thesis provides an overview of the design and subsequent implementation

of an integrated home automation system tentatively titled Auto-MATE.

Following this introductory chapter the next section, Chapter 2, explores the

currently available products that are comparable to the desired Auto-MATE

product. From this product review a core set of features common to all home

automation systems is detailed.

Chapter 3 then builds upon this feature set and extends it where

necessary by utilising a top down approach to break the system into

components. Beginning with the highest level and working down a

comprehensive set of specifications is derived.

Chapter 1

5

This set of specifications allows for a discussion of the Hardware

implementation in Chapter 4 and the Software implementation in Chapter 5.

Having specified the system and described the implementation it is then

appropriate to describe the status of the project at the end of the thesis period.

As the product has a working prototype it is possible to revisit the original

requirements and provide a comparison with the final working product. This is

presented in Chapter 6.

Chapter 7 provides a design review listing areas of the design that

performed sub-optimally and with hindsight would be changed. Included in this

chapter is a discussion of possible future directions for the Auto-MATE system.

Finally Chapter 8 provides some brief concluding remarks on what may

be considered a successful thesis project.

6Chapter 2

Review of Existing Home AutomationTechnologies

As stated in Chapter 1 there are several communications protocols available.

Of these only a few can utilise the mains power as the physical layer for

transmission. Further reducing this only four protocols are sufficiently

developed to the point where actual commercial products have been developed.

These are X-10, LonWorks, EHS2 and CEBus3.

This chapter reviews these mains power communications standards as

well as the associated software and hardware products in order to derive a

suitable specification for the proposed Auto-MATE system. A subset of

available products is presented that is indicative of the range, functionality and

cost of present devices.

The currently available home automation products share some common

attributes. They can all be categorised as one of three distinct sub-systems at

the highest level:

A communications protocol

A central controller/interface

Modules for control or sensing

Each standard and its associated products is evaluated below:-

2 European Home Standard3 Consumer Electronics Bus

Chapter 2

7

2.1 X-10

X-10 is the home automation industry incumbent standard [4]. In 1978 Dave

Rye and the design team at Pico Electronics riding high on the success of

projects X-1 to X-94 decided to embark on a home automation project [5]. Their

goal was to develop a system to control lights and appliances over the existing

house power wiring. X-10 was originally designed as a protocol for one way

communications only. Recently a few products with limited two-way capabilities

have become available.

2.1.1The X-10 Protocol

The transmission method used by X-10 is based on a simple data frame with

eight data bits (one byte) preceded by a predetermined start code. The X-10

binary data is transmitted by sending 1ms bursts of 120kHz just past the zero

crossing of the AC waveform. A binary "1" is defined as the presence of a

pulse, immediately followed by the absence of a pulse. A binary "0" is defined

as the absence of a pulse, immediately followed by the presence of a pulse [6].

The X-10 devices all have a zero voltage-crossing detector built in so the

transmitters and receivers can synchronise.

This is shown in Figure 2.1: X-10 Signal Transmission.

Figure 2.1: X-10 Signal Transmission

4 X-1 to X-8 were calculator ICs, X-9 was an automated record changer.

Chapter 2

8

The transmitted pulses have a duration of 1ms and the receivers open a

receive window of 0.6ms. The setting of the transmission start point is achieved

by transmitting a sequence beginning with at least 6 leading clear zero

crossings, then a start code of "pulse", "pulse", "pulse", "absence of a pulse" (or

1110). This is shown in Figure 2.2: X-10 Transmission Start Code.

Figure 2.2: X-10 Transmission Start Code

Each device on an X-10 network is described with a house code and a

unit code. The house code is a 4 bit nibble that is given a letter code

designation from A to P. The unit code is also a nibble with a numerical code

designation from 1 to 16. After the initialisation sequence the house code is

transmitted followed by the unit code. Once a receiver has processed its

address data, it is ready to receive a command. As before, all data frames must

begin with a start code then the following nibble gives the letter code. The next

nibble is the command. An additional bit, the function bit, is added to the end of

the second nibble to differentiate between unit code and command. This

function bit takes the value 0 when the second nibble is a unit code and 1

when the second nibble is a command. Since the last bit is the function bit all

the commands end in a binary 1.

All X-10 frames then require a minimum of eleven AC cycles to transmit

one frame consisting of six clear zero voltage crossings, the start code and the

Chapter 2

9

required two data nibbles. For purposes of redundancy, reliability and to

accommodate line repeaters, the X-10 protocol calls for every frame of data to

be transmitted twice. In addition whenever the data changes from one address

to another address or from an address to a command or from one command to

another command the data frames must be separated by at least six clear zero

crossings (or "000000"). Therefore the full transmission of an X-10 command

takes 47 AC cycles as shown in Figure 2.3: X-10 Transmission Cycle.

Figure 2.3: X-10 Transmission Cycle

2.1.2X-10 Products

X-10 is the most established of the home automation protocols and as such it

has the largest product base.

2.1.2.1 ActiveHome

ActiveHome [7] is a PC based home automation program that allows for control

of up to 256 X-10 devices. The devices can be controlled in three ways. The

program has a scheduler that controls devices at preset times, there is a

handheld remote control and devices can be controlled at the computer using a

graphical interface. ActiveHome does not support two way communications so

there is no way of polling the status of a device.

ActiveHome retails for US $133 (No distributor in Australia).

Chapter 2

10

2.1.2.2 HAL 2000

HAL 2000 [8] is a PC based home automation program similar to ActiveHome.

It too can control 256 devices with one way communications only. HAL 2000

has the ability to be controlled via voice either locally or over a telephone in

addition to preset scheduled control and control at the computer. HAL can

access the Internet to retrieve information such as weather, sports reports etc.

HAL 2000 retails for US $399 ($749 in Australia).

2.1.2.3 HomeSeer

HomeSeer [9] is a PC based home automation program with two way

communication capabilities it incorporates a communication interface that keeps

track of device states when used with devices capable of two way

communications. In addition to scheduling and control of X10 devices from the

computer, HomeSeer offers voice recognition and interaction using Microsoft

Voice Agent, as well as access to X10 devices from the Internet via a web

browser or by using e-mail. HomeSeer allows the user to include scripts written

in Visual Basic or Perl for logic dependant operations.

HomeSeer retails for US $80 (No distributor in Australia).

2.1.2.4 MisterHouse

MisterHouse [10] is a freeware open source home automation that can be run

on a PC under either Windows or Unix. MH is written in the Perl language and

can be extended by the addition of objects and methods. For example, the

following will create an object for a light and turn it on 15 minutes after sunset:

$backyard_light = new X10_Item "C4";

if (time_now "$Time_Sunset + 0:15") {

speak "I just turned the backyard light on at $Time_Now";

set $backyard_light ON;

}

X10_Item, time_now, speak, $Time_xxx, and set are all home automation

related objects, methods, functions, and variables defined in MH.

Chapter 2

11

Figure 2.5: Two-Way Lamp Module

MisterHouse executes actions based on voice input, scheduling, file data

and serial port data. There is a web interface to allow control and feedback

from any browser on the Internet. MisterHouse has two way communications

with capable devices. It also shares a modem for caller ID and paging, reads

MS Outlook calendars for event reminders as well as reading and writing e-mail,

HTTP5, and FTP6 files unattended.

2.1.2.5 Decorator Dimmer Switch

The Decorator switch [11] (shown in Figure 2.4:

Decorator Dimmer) is available in 110V version only.

It is capable of local and remote control but is limited

to one way communications meaning that a local

change of status is not updated in the controller.

Retails for US $19.99 (No distributor in Australia.)

2.1.2.6 ActiveHome Two Way Lamp Module

The ActiveHome lamp module [12] (shown in Figure 2.5:

Two way lamp module) has limited two-way control. When

used with a two-way compatible controller the module can

respond to a status request command with an indication as

to whether the module is on or off but not the level of

dimming. The module is capable of local and remote

control. The device can switch an incandescent load of

300 watts and is available in a 110 volt version only.

Retails for US $32.99 (No distributor in Australia).

5 Hypertext Transfer Protocol6 File Transfer Protocol

Figure 2.4: DecoratorDimmer

Chapter 2

12

Figure 2.6: ApplianceModule

Figure 2.7: Eagle EyeSensor

Figure 2.8: Power Line Interface

2.1.2.7 Power House Three Pin Appliance Module

The Three Pin Appliance Module [13] (shown in Figure 2.6:

Appliance Module) is capable of being turned on and off using

one-way communication and has no local control. The device

can be purchased in 240 and 110 volt versions with the 240

volt version being capable of switching 10 Amps.

Retails for US $13.99 ($79 in Australia.)

2.1.2.8 The Power House Eagle Eye Motion Sensor

The Eagle Eye [14] (shown in figure 2.7: Eagle Eye

Sensor) sensors motion over a range of 7 meters and

then can transmit a signal to a two-way computer

interface indicating that motion has been detected.


2.1.2.9 Power House Two-Way Power Line Interface

The Power House interface [15] (shown in

Figure 2.8: Power Line Interface) allows for

two-way communications between a PC

RS2327 port and the power line.

Retails for US $24.99 (No distributor in

Australia.)

2.1.3X-10 Summary

X-10 is the most popular and cheapest form of home automation currently

available. In the USA it is estimated that over 100 million X-10 products have

been sold since its inception in 1978 [16]. X-10 requires nearly a second for a

7 Serial Communications Standard

Chapter 2

13

byte to be transmitted in a 50Hz system. In spite of the slow transmission

speed X-10 still suffers from unreliable transmission, as there is no form of error

checking for lost frames from noise or signal collisions. Although some new

devices have two-way communications the command is limited to a simple

status check whereby the device responds that it is either on or off. The X-10

devices then act as slave devices and are not capable of initiating a

transmission when a change of state occurs locally.

2.2 LonWorks

The LonWorks standard was developed by Echelon [17]. The standard consists

of the LonTalk protocol, Neuron chips and LonWorks transceivers. The Neuron

chip is a proprietary device of LonWorks and consists of three resident 8-bit

processors: two processors dedicated to LonTalk protocol processing, and a

third dedicated to the node's application program. The transceivers can only

interface with the Neuron chip which in turn can only be programmed using a

LonWorks proprietary version of the C language known as Neuron C.

Although the standard has been in existence for ten years it was until

October 1999 a closed proprietary standard. LonWorks has been primarily

used in the automation of buildings and factories and is used extensively in

energy management applications. Within the last two years Echelon have

made a push into the home automation market.

2.2.1LonTalk

LonTalk [18] is the communications protocol for the LonWorks system. The

LonTalk protocol design follows the International Standards Organisations

Reference Model for Open Systems Interconnection (ISO OSI), which

prescribes the structure for open communications protocols. LonTalk

implements all seven layers of this model.

Layer 1: Network Physical Layer

This layer addresses the specifics of wiring and connections.

Chapter 2

14

Layer 2: Data Link Layer

This layer defines the rules of access to the physical layer. Services provided

by this layer include error detection, flexible allocation of bandwidth, priority

access mechanisms, message collision avoidance and collision detection.

Layer 3: Network Layer

This layer specifies the destination of a message on the network. Services

provided by this layer include the node address information. It provides for

routing of messages to control network bandwidth usage as well as determining

which nodes on the network receive various messages.

Layer 4: Transport Layer

This layer establishes the type of services required for the node messages

depending on the level of reliability required by the application. The services

provided are broadcast addressing, acknowledged service, unacknowledged

service, duplicate packet detection and authentication.

Layer 5: Session Layer

This layer provides the communications to request action from another node.

Layer 6: Presentation Layer

This layer provides translation of the network data for the application.

Examples of services provided in this layer include Input, output, and

configuration variables for the node and standard data representations for

physical quantities. The standard data representations are important to assure

interoperability between products from different manufacturers.

Layer 7: Application Layer -

This layer includes services to simplify development of application programs to

interface to specific sensors, actuators, and external microprocessors.

The LonTalk protocol provides a common applications framework that

ensures interoperability by using network variables and Standard Network

Variable Types (SNVTs) [19]. Network variables communication between

Chapter 2

15

nodes on a network takes place using the network variables that are defined in

each node. The product developer defines the network variables when the

application program is created as part of the application layer of the protocol.

Some nodes may send a network variable while others may receive. By only

allowing links between inputs and outputs of the same type, network variables

enforce an object-oriented approach to product development. Whenever a

node program writes a new value into one of its output variables, the new value

is propagated across the network to all nodes with input network variables

connected to that output network variable. This action is handled by the

protocol within the Neuron Chip. The user defines the network variable

connections when the nodes are installed on the network. The use of SNVTs

contributes to the interoperability of LONWORKS products from different

manufacturers.

The following are examples of SNVTs:

Variable Type Units

Temperature Degrees Celsius

Relative Humidity Percent

Device State Boolean

Day of Week Enumerated List (Mon-Sun)

LonTalk Network Management Services are a formal part of the LonTalk

protocol. Support for these services is contained in every LonWorks node. This

guarantees that all nodes, regardless of origin, can respond to LonTalk

commands from nodes designed to perform network management functions.

Each node has a 48-bit unique ID assigned during manufacture.

The Neuron Chip is the heart of the LONWORKS technology. Nodes

contain a Neuron Chip to process all LonTalk protocol messages, sense inputs

and manipulate outputs, implement application-specific functions and store

installation-specific parameters. Neuron chips are programmed in Neuron C,

which extends ANSI Standard C to support an object-oriented approach to

developing distributed applications.

Chapter 2

16

Figure 2.9: LevitonDimmer

Figure 2.10: LevitonOccupancy Sensor

Power line transceivers communicate with either a proprietary spread

spectrum or a narrow band technology that provides reliable communications

for up to 2000 meters on a clear line

2.2.2LonWorks Products

As Echelon are relatively new to the home automation industry there are fewer

devices available. It appears that LonWorks has been used to successfully

develop custom industrial automation systems for several years and the devices

being put forward for home automation use are scaled back versions of these.

2.2.2.1 i.LON 1000 Internet Server Starter Kit

The i.Lon starter kit [20] is available through Echelon and includes network

control software and the PC to mains power interface for mains power

communications. The software includes a web browser for complete control

over the Internet.


2.2.2.2 Leviton Dimmer Switch

The Leviton switch [21] (shown in Figure 2.10: Leviton

Dimmer) has local and remote control with full two-way

communications. The switch turns on/off and has dimming

increments of 1%.


2.2.2.3 Leviton Occupancy Sensor

The Leviton sensor [22] (shown in Figure 2.11: Leviton

Occupancy Sensor) is capable of sensing motion up to 30

meters away and reporting this back to the host controller.


Chapter 2

17

Figure 2.11: Infinitelan Controller

2.2.2.4 INFINITELAN Single Phase Meter/Controller

The INFINITELAN controller [23] (shown in

Figure 2.12: Infinitelan Controller) allows for

control of loads up to 30 Amps as well as

the monitoring of the power supplied to the

load. The energy use data can be

transmitted in ASCII format back to the host

controller. This device has no local control.

Retails for US $260.00 (No distributor in

Australia.)

2.2.3LonWorks Summary

LonWorks is still very much a controlled proprietary technology. Although the

Neuron chips required in all LonWorks modules can be purchased from

manufacturers including Motorola, the development tools such as the Neuron

C compiler must be purchased directly from LonWorks. The development

tools are expensive.

2.3 CEBus

The CEBus Standard [24] is an open standard, developed and controlled via the

standards processes of the EIA8 and ANSI9. CEBus is designed specifically for

home automation networks and as such all product developments have been

with the home consumer in mind. Within the EIA the standard has the

designation EIA-600.

2.3.1The CEBus Protocol

The CEBus standard implements four of the seven layers of the open systems

interconnection (OSI) model of the International Organisation Standardisation

as shown in Figure 2.13: OSI Model [25].

8 Electronics Industry Association9 American National Standards Institute

Chapter 2

18

Figure 2.12: OSI Model

Layer 1: Network Physical Layer

The physical layer exchanges symbols with the data link layer, encoding and

decoding the symbols to and from the medium states. The states required to

represent the symbols are modulated and demodulated with the medium carrier

by the physical layer.

The CEBus standard defines that there are two different states, superior

and inferior. The inferior state is defined as the idle state. To begin a

transmission, the medium starts in the superior state. It then alternates states

for each successive symbol that is transmitted. The length that each state is

transmitted for determines the transmitted signal. There are four different

symbols, logical one, logical zero, end-of-field and end-of-packet. The

transmission lengths for different symbols are Logical One 100ms, Logical Zero

200ms, End-of-Field 300ms and End-of-Packet 400ms.

For the power line medium the superior state is described as a chirp of

noise. The chirp is defined as a signal that changes frequency from 200kHz to

400kHz, and then 100kHz to 200kHz within the space of 100s. The spread-

spectrum chirp is shown in Figure 2.14: Spread Spectrum Chirp.

Chapter 2

19

Fig 2.13: Spread Spectrum Chirp

In order to create the different length states for the different symbols, this

100s chirp is repeated to create the required length symbol. Finally, the

frequency sweep means that the chirp is spread-spectrum, which gives the

signal better noise resistance. All data in the CEBus protocol is transmitted in

packets with a header and a message. The header contains information on the

type of service being provided as well as source and destination addresses with

the total length being nine bytes. The packet message can be up to 32 bytes

long. Using the spread spectrum technology transmission speeds of 10kbps

are standard with a low error rate especially when used in the address

acknowledged modes.

Layer 2: Data Link Layer

The data link layer is responsible for receiving all of the packet types:

ACK_DATA, UNACK_DATA, ADR_ACK_DATA, and ADR_UNACK_DATA as

well as rejecting duplicate packets of type ACK_DATA, ADR_ACK_DATA, or

ADR_UNACK_DATA.

It allows the node to recognise its own system and node address and the

broadcast address (system and/or node address = 0000).

Chapter 2

20

Layer 3: Network Layer

The network layer is required to generate an ID_Packet when first configured

(addresses installed), upon power-up after being configured, or after system or

unit address changes and generate an ID_Packet if a request for an ID header

is received.

Layer 4: Application Layer

The Application layer contains the Common Application Language CAL. This is

the language by which CEBus devices communicate. The CEBus Application

Language is a set of common language and data constructs created to enable

inter-operation between products used in residential automation. The reasoning

behind CAL is to provide interoperability between different manufacturers

products without prior knowledge of the products.

An easy way to gain a high-level understanding of CAL command syntax

is to view it in terms of object-oriented design. In the world of CEBus devices,

each control within a device may be thought of as an object. For example to

turn up the volume on a radio by three levels, the CAL Control function would

somehow need to deliver a message -- "turn yourself up 3 notches" -- to the

Volume Control Object associated with the radio in question. Upon receiving

the message, the Volume Control Object would add 3 to the value of one of its

instance variables, such as current_volume_level. This action by the object

would then increase the volume of the radio.

CAL bundles one or more of these messages into an Application Layer

Service Data Unit ASDU, and sends it out over the CEBus network. An ASDU

can be sent to one node, a group of nodes, or all nodes on the CEBus network.

Physically, these nodes are associated with particular devices (television,

stereo, VCR, washing machine, light, air conditioner etc.).

CAL Objects are not organised in a class hierarchy. The exact behaviour

of a CAL Object depends on the device context under which it exists. CAL

supports a hierarchy within a device. A device, characterised by its unique Unit

address, is functionally subdivided into contexts. The Universal Context is

always present and handles device level commands, such as naming, and

addressing. The Universal Context contains instance variables that store node

specifications (manufacturer, model, name, class, etc.) as well as node

Chapter 2

21

variables (such as power on/off and device online/offline. As well as the

Universal Context, a device may contain one or more additional contexts.

These other contexts represent functional subsystems within the device. Audio

and Tuning are examples of contexts within a television. Contexts are

subdivided into objects. Objects represent particular controls or functions within

a context. Objects are divided into classes which represent common

functionality. For example, an object class 07 (Analog Control Object) may be

used to represent a volume control, a thermostat, or a light dimmer. The exact

function of an object is solely dependent on the context in which the object is

instantiated.

Contexts other than the Universal Context fall under the heading of

Operation Group Contexts. These contexts represent functional subsystems of

consumer devices. Examples of Operation Group Contexts are Audio Context,

Lighting Context, Security Zone Context, and Environmental Zone Context.

Each context specification consists of the name of the context and its ID

number used to address the context within the product. A general description of

the context is given along with possible applications of the context. The objects

that could make up the context are then listed. Not all objects listed in a context

need be provided in a particular implementation of a product.

Each device on a CEBus network has its own address consisting of a

house code and a device address each of which have 64 thousand (216)

addresses.

2.3.2CEBus Products

As CEBus is a protocol specifically targeted at home automation the developed

products are designed with the home consumer in mind. The most

comprehensive range of products developed for the CEBus protocol is the

SmartGear range by GE-Smart [26]. This range is expected to be available in

the USA in the fourth quarter of 2000. Initially the devices will only be for 110

volt systems.

Chapter 2

22

Figure 2.14: Manager Plus

Figure 2.15:Smart Switch

Figure 2.16:Appliance Port

2.3.2.1 GE-Smart Manager Plus

The Manager Plus [27] (shown in Figure 2.15:

Manager Plus) is a stand alone programmable

control panel. Devices connected to the network

can be monitored and controlled using an LCD

display and a menu driven interface. The controller

allows for scheduled events as well as inputs from

sensors such as temperature and motion

detection. A separate RF remote provides control

from up to 30 meters away.

Expected retail price US $900.

2.3.2.2 GE-Smart Smart Switch

The Smart Switch [28] (shown in Figure 2.16: Smart

Switch) is capable of turning on/off up to 500W of load

with dimming functionality. The switch can be

controlled locally or remotely over the home network.

The output state can be queried via the network by the

host controller.

Expected retail price US $175.

2.3.2.3 GE-Smart Appliance Port

The Appliance Port [29] (Shown in Figure 2.17:

Appliance Port) plugs into the existing mains power

point and an appliance such as a coffee maker or radio

can be plugged into it. The port can supply a load of

20 Amps on a 110 volt supply. The port can be turned

on/off locally and remotely by the controller.

Chapter 2

23

2.3.2.4 GE-Smart Sensor Port

The Sensor Port [30] (shown in Figure 2.18: Sensor

Port) interfaces between sensors such as motion

detectors, light or temperature sensors that have a

digital or analog output and the mains power line.

The data is then available to the central controller via

the network.

2.3.3CEBus Summary

The CEBus protocol and associated products are well placed to be the front

runners in the home automation industry in terms of functionality and range.

CEBus products are unavailable in Australia at present.

2.4 European Home Standard

The European Home Standard [31] is the European equivalent of the American

CEBus Standard. EHS is an open technology and development requires only a

modem chip and a microcontroller. EHS is behind the other standards reviewed

in terms of product development.

2.4.1The EHS Protocol

EHS specifies a network protocol that covers layers 1, 2, 3 and 7 of the OSI

reference model. It also specifies a Network Management section and uses a

spread spectrum chirp to transmit the data [32].

The protocol supports several media: power-line, coaxial cable, twisted

pair, infrared and radio frequency. Initial efforts have been focused on the

power-line medium at 2400 bits/sec.

2.4.2EHS Products

As stated earlier EHS lags competing standards. The only product available for

comparison is the ST7 Development Board (shown in Figure 2.19: EHS

Figure 2.17: SensorPort

Chapter 2

24

Development Board) manufactured by Trialog [33]. This board enables

communications over the power line between two ST7 development boards

when connected to a host microcontroller.

Figure 2.18: EHS Development Board

2.4.3EHS Summary

EHS is several years behind other standards at present and is unlikely to be a

dominant force in home automation without the support of a product

manufacturer.

2.5 Review Summary

In this chapter a subset of available home automation protocols and products

were reviewed. From this review it is possible to identify a set of minimum

products and functionality necessary to provide a useful home automation

system for entry level consumers. The three sub-systems of protocol, controller

and modules are each summarised in table 2.1, 2.2 and 2.3 respectively. From

these tables the following minimum set of desired features has been identified:

Chapter 2

25

Two way data transmission at an acceptable speed with error and collision

checking.

Scheduled and sensor triggered events.

Internet connectivity allowing remote control and monitoring.

Light switch/dimmer module.

Appliance module.

Motion detector module.

Climate sensor module.

Modules with full two-way communications and local control were applicable.

The derived list of features represents only a small subset of the possibilities

for a home automation system. It is however sufficient for an entry-level

system. From these features a specification for the proposed Auto-MATE home

automation system can be formalised. The complete specification is presented

in Chapter 3.

Protocol Baud Rate error detection

collision detection

Noise immunity

Proprietry software required?

Number of possible

addresses

X-10 10bps no no poor yes 256LonWorks 10kbps yes yes good yes 64k

CEBus 10kbps yes yes good no 64k

EHS 2.4kbps yes yes good no 64k

Table 2.1: Comparison of Home Automation Protocols

Protocol Product 2-Way Internet Connect-

ivity

Event Scheduling

Voice Control

Hand Held

Remote

Cost $US

X-10 Active Home no no yes no yes $133.00X-10 HAL 2000 no yes yes yes no $399.00X-10 Home Seer yes yes yes yes no $80.00X-10 Mister House yes yes yes yes no Freeware

LonWorks i.Lon yes yes yes no no $1,975.00CEBus Smart Manager yes no yes no yes $900.00

Table 2.2: Comparison of Controllers

Chapter 2

26

Protocol Device 2-Way Local Control

Cost $US

X-10 Decorator Dimmer

no yes $19.99

X-10 Lamp Module limited yes $32.99

X-10 Appliance Module

no no $13.99

X-10 Eagle Eye Motion

Detector

n/a n/a $24.99

X-10 Powerline Interface

yes n/a $24.99

LonWorks Leviton Dimmer

yes yes $75.95

LonWorks Leviton Occupancy

Sensor

n/a n/a $35.95

LonWorks INFINITELAN 30A controller

yes no $260.00

CEBus GE Smart Switch

yes yes $175.00

CEBus GE Appliance Port

yes yes unavailable

CEBus GE Sensor Port

yes yes unavailable

Table 2.3: Comparison of modules

27

Chapter 3

System Design Specifications

Having reviewed the current state of the home automation market it is now

possible to specify the requirements for a new, low cost, reliable, entry level

home automation system to satisfy the vision statement in Chapter 1. An

overview of the complete system requirements will be presented before

detailing the specifications for each of the sub-sections as listed in Chapter 1.

At each juncture the emphasis will be on satisfying the core functionality derived

from the technology review of Chapter 2.

The specifications developed in this chapter will be sufficiently detailed to

allow for the subsequent design of the hardware and software components in

chapters five and six.

3.1 The Auto-MATE System

The Auto-MATE system is intended as a low cost, entry level product. This

means that the system will have the minimum functionality necessary to be a

useful integrated home automation system. From the previous chapter the

minimum specifications for the complete system are:

Reliable two-way mains power communications at an acceptable speed with

minimum transmission errors.

Controller for monitoring system status and handling timed and sensor

triggered events.

Remote control and monitoring of the system using a web interface and e-

mail messages.

Control and sensor modules with local control and load sensing intelligence

where applicable.

Chapter 3

28

This minimum set of specifications leads to the block diagram of Figure 3.1:

Auto-MATE Block Diagram.

Figure 3.1: Auto-MATE Block Diagram

In addition to fulfilling the desired functionality the system must also adhere to a

set of design criteria as set out below.

3.2 Design Criteria

The following criteria are necessary to ensure the Auto-MATE system is a

desirable product and does not become quickly redundant.

Functionality

The system has to provide a level of functionality that appeals to the mass

market and not only to enthusiasts. To ensure this the Auto-MATE system is

initially limited to automating only devices that are common to most homes.

Ease of Use

The system must be able to be used by a broad range of people. There is

however a limit on the minimum level of complexity possible in an automated

Chapter 3

29

product. A testament to this is the number of programmable VCRs around the

world flashing 12:00. As a benchmark a familiarity with Microsoft Windows

environment is assumed.

Cost

While cost at the prototype stage is not of paramount concern some budgetary

caution must be observed if the product is to be feasible in the long term. The

present cost of an X-10 appliance module in Australia is $79 ($AUS). The

equivalent Auto-MATE module is expected to have superior features so an

initial prototype cost of twice the X-10 cost seems reasonable.

3.3 System Topology

The basic premise of a home automation system is that the automated devices

be linked together so that the action of one device may be dependent on the

state or action of one or more other devices. The interconnection of similar

devices is commonly referred to as a network.

There are three possible network topologys to be considered, these are

Star, Ring and Bus. In Australia power and lighting circuits are radial wired

which precludes the use of a ring network. The use of a Bus would be an

interesting method of control as each module would need to be intelligent

enough to know what other modules require the information they have as well

as being able to know which node can use the network at any time. The use of

a Bus would however prevent any direct control by the home occupant as well

as being unable to provide a gateway into the home for the purposes of external

control and monitoring. The final topology considered then is the Star. This

type of network is predominant in existing home automation systems and is the

preferred network for the Auto-MATE system. With a Star network (shown in

Figure 3.2: Star Topology) all attached modules are controlled by a central

controller. The advantage of a Star system is that nodes can be added or

removed or malfunction at any time without affecting the network.

Chapter 3

30

Figure 3.2: Star Topology

Having derived the system topology to be a star network in this section it is

necessary to now specify the requirements for each of the Auto-MATE sub-

systems.

3.4 Central Controller

The central controller is responsible for monitoring and updating the status of

each connected device. In keeping with the design criteria the controller must

provide a user friendly interface to the system. The central controller also

requires an interface to the power lines to enable the mains power

communications.

3.4.1Controller Platform

From the product review of Chapter 2 it can be seen that the most popular

platform for developers of home automation systems is a PC. The only

competitor to the PC based controllers at present is the stand alone controller

such as the GE-Smart Manager.

The choice of a suitable platform for the system controller is dependent

on a wide range of variables such as useability, reliability, cost and extensibility.

The continuing prevalence of Personal Computers in homes makes them an

ideal choice as they can satisfy the useability, cost and extensibility

requirements. The additional cost can be limited to the required software and

Chapter 3

31

the interface module to the power line. Adapting an already familiar device

satisfies the useability requirement and a PC iof capable of being extended with

peripheral devices as needed.

The reliability issue is less easily satisfied with the selection of a PC as

the controller platform. The reliability of a PC suffers from software crashes and

power failures. The software crashes can be limited by the use of a dedicated

PC used only for the home automation system. A back up power supply such

as an UPS10 would be required to keep the system running during power

outages. Both of these solutions would add to the overall cost of the system

[34]. As the Auto-MATE system is not intended to control sensitive applications

such as fire alarms the use of a shared PC is acceptable.

3.4.2Modes of Control

The use of a PC as the central controller allows for several modes of control.

From the product comparison the most useful modes of control are local control

at the computer, remote access to the system via the Internet and control from

within the home using voice commands. A GUI11 should be provided to allow

an easy to use interface between the occupant and the Auto-MATE system.

The controller must initiate events based on time scheduled commands or as a

result of inputs from sensor modules.

3.4.3Additional Services

In addition to the modes of control the central controller can perform other

services to enhance the performance of the automation system. If the system is

to be connected to the Internet for the purposes of remote control the same

connection can be utilised for additional purposes. The Auto-MATE system will

include the ability to retrieve information from the Internet. Such information

may include, but is not limited to, weather reports, sports information and

television guides. This information can then be presented to the home

occupant or used by the controller to make decisions such as turning on a

module that controls an irrigation system.

10 Uninterruptable Power Supply

Chapter 3

32

3.4.4PC to Power Line Interface

The selection of a PC as the controller platform requires that a dedicated

module must be included into the design to provide a seamless interface

between the computer and the power line. This interface should be able to

connect directly to the computer using an existing IO12 port as well as

connecting to the power line. This connection should appear transparent to the

end user.

3.5 Mains Power Communications

The mains power communications is an integral component of the automation

system. Some existing systems suffer from unreliable, slow communications. It

is unlikely that a home automation system would become a widespread product

with such problems.

3.5.1Reliability

Reliability is probably the most important criteria for an automation system of

any description. The communications protocol must provide error checking for

transmissions with automatic retries on unsuccessful attempts. As the power

line is a noisy environment the transmitted signal should be either spread

spectrum or multi-channel to maximise successful transmissions.

3.5.2Baud Rate

Although most home automation applications are not time critical the

transmission rate should be the maximum possible to allow for possible future

extensions to the home network. At present the best transmission rates are in

the vicinity of 10kbps [35] so this is the specified rate for the proposed Auto-

MATE system.

11 Graphical User Interface12 Inout/Output

Chapter 3

33

3.5.3Transmission Distance

According to the AS30013 [36] the maximum distance for a lighting or power

sub-circuit in a residential installation is 50 meters. Therefore allowing for the

central controller and a module to be at the furthest extremities of different

circuits the maximum transmission distance would be 100 meters. Therefore

this distance is the minimum specification for the Auto-MATE system.

3.5.4Network Communications IC

The mains power communications is not possible without the use of a dedicated

network communications chip. The chip selected must fulfil the following

functionality:

Application programmable or allow connection to a host microcontroller.

Support the power line as the Physical Layer.

Provide for automatic retries of unsuccessful transmissions.

Capable of transmission rates of at least 10kbps.

3.5.5Microcontroller

A microcontroller will be required for the purposes of responding to received

commands as well as initiating data transmissions back to the central controller.

The microcontroller may be a host device or embedded in the network

communications chip depending on the hardware implementation. The

microcontroller will need to comply with the subsequent minimum feature set:

8 bit registers

UART serial communications interface

Two external interrupt pins

Analog to digital converter

8 bit timer

20 IO pins

13 Australian Standard 3000 specifies the rules for wiring in Australian installations

Chapter 3

34

Sufficient memory for protocol implementation and device control code

written in a procedural language such as C.

3.6 Intelligent Modules

The level of intelligence of the reviewed products varies from devices that can

simply turn on/off when a command is received to devices with full two way

communications and power measurement capabilities. The Auto-MATE

modules are intended to provide features comparable to existing products.

3.6.1Minimum Functionality

The modules must have full two-way communications. By this it is meant that

the modules can respond to commands sent to them as well as initiating

communications when the status is changed locally. When a command is sent

from the central controller the receiving module must respond acknowledging

that the command has been successfully performed. Each device must have a

unique address as well as a group address to enable commands such as all

lights off. The product review of Chapter two identified the minimum sub-set of

possible devices for an entry-level system to be functional. The individual

specifications for each of these devices is detailed below:

3.6.2Light Switch / Dimmer

The light switch must be rated to control a 240 Volt, 10 Amp load. The switch

needs to be capable of turning the load on/off as well as dimming to any one of

ten levels. The switch must be controlled by the central controller as well as

locally at the switch. The switch should default to a safe off state after a power

down reset.

3.6.3Appliance Module

The appliance module is intended to mimic the functionality of the light switch

module without the dimming capability.

Chapter 3

35

3.6.4Motion Detector

The motion detector module should sense motion from a distance of at least 10

meters. When motion is detected the central controller should be alerted. The

detector should be able to be activated and deactivated remotely.

3.6.5Climate Sensor

The climate sensor is intended to provide useful information about the local

conditions within the home. This will enable the central controller to make

decisions such as controlling heating and cooling devices. When requested the

sensor should provide a temperature and a humidity reading with reasonable

accuracy.

3.6.6Load Sensing

Most of the home automation devices available do not provide any means of

sensing whether the load has actually been turned on or off. For a device to be

considered intelligent it is not sufficient that it simply switches the load and then

reports back that the task has been performed it must also ensure that the load

is in fact on. As an example the light switch may turn on but if the bulb has

blown the command was not successful. For this reason it is necessary to

include some load sensing hardware into the light and appliance modules.

3.7 Summary of Design Specifications

In this chapter the specifications for each subsection of the proposed system

have been derived. The specifications have been developed to comply with the

both the required functionality and the outlined design criteria. With the

proposed product now specified it is possible to detail the design and

implementation of the final Auto-MATE product. The hardware implementation

is presented in Chapter 4 and the software implementation in Chapter 5.

36

Chapter 4

Hardware Implementation

With a set of design specifications now in place the hardware implementation

can be detailed. The hardware design can be divided into several sub-systems

at the lowest level. These sub-systems are first identified and then the actual

implementation is described as the chapter progresses. Each of the hardware

modules for the Auto-MATE system is made up of these building blocks. The

full hardware schematics and PCB layouts are included as Appendix A.

4.1 Overview of Hardware Requirements

The hardware sub-systems required for implementing all of the proposed Auto-

MATE modules are as follows:

1) Mains Power Network Communications circuit.

2) Load switching circuit

3) Load sensing circuit

4) Zero voltage crossing circuit

5) Power supply circuit

6) Local control buttons circuit

7) Host microcontroller

8) Temperature sensor circuit

9) Humidity sensing circuit

10) Motion detector circuit

Chapter 4

37

With these ten hardware blocks all of the proposed features of the Auto-MATE

system modules can be implemented. The only exception is the PC / power

line interface module that will be discussed separately.

4.1.1Physical Orientation of Subsystems

Although not all modules require all of the hardware blocks it was decided early

in the implementation process to build generic printed circuit boards capable of

being implemented as any one of the required modules. The hardware blocks

are separated into being either power or control blocks and are incorporated

onto one of two printed circuit boards depending on this designation. The

CEBus Power Module (shown in Figure 4.2: CEBus Power Module) consists of

sub-systems 1 4. The remaining circuitry is located on the CEBus Control

Module (shown in Figure 4.1: CEBus Control Module).

Figure 4.1: CEBus Control Board

A block diagram of the hardware is shown in Figure 4.3: Hardware Block

Diagram.

Figure 4.2: CEBus Power Board

Chapter 4

38

PowerLine

ControlledDevice

CEBus PowerlineCoupling

Load Switching

5V & 15V PowerSupply

Zero VoltageCrossingDetection

Load Sensing

Auto-MATEControl Module

Power Board

Microcontroller

Humidity Sensor

TemperatureSensor

Local ControlButtons

Motion Detector

Control Board

Figure 4.3: Hardware Block Diagram.

4.2 Mains Power Communications

The mains power communications component is an integral section of this

thesis project. As set out in section 3.5 of the specifications the

communications must be inherently reliable and reasonably fast. From the

product review of Chapter 2 the possible choices are LonWorks, CEBus or

EHS. Of these three the chosen protocol was CEBus. This implementation

decision was due to the fact that CEBus is a completely open standard and

therefore requires no proprietary development tools. CEBus has the edge over

EHS in terms of available literature and the fact that it has already been proven

in product development. To implement the CEBus protocol using the mains

power lines as the physical layer requires two components. The first is a

CEBus compliant Network Interface Transceiver and its necessary signal

isolation circuitry. The second is a host microcontroller to implement

transmitted commands and data.

4.2.1Network Communications Transceiver IC

The selection of CEBus as the protocol for the mains power communications

enables the implementation to progress to the selection of a suitable network

communications chip. Three CEBus transceiver ICs were considered. These

Chapter 4

39

were the SSC P300 PL Network Interface IC from Intellon Corporation [37], the

IT800 Power Line Modem from Itran Communications [38] and the CEWay PL-

111 Power Line Communication Transceiver from Domosys Corporation [39].

The Itran product was quickly disregarded as it does not become available until

the fourth quarter of 2000.

The initial selection was the Intellon SSC P300. This selection was

based solely on availability as an evaluation kit for this chip had been

purchased the previous year for another thesis project [40]. Attempts over a six

week period to communicate over the power lines using the P300 proved

remarkably unsuccessful. The following sections detail the difficulties

encountered with the use of the P300 and the successful implementation of its

successor the CEWay PL-111.

4.2.1.1 The Intellon SSC P300

The evaluation kit contains two EK P300 development boards (shown in Figure

4.3: EK P300 Development Board) and allows for an interface to the power line

through supplied plug packs.

Figure 4.4: EK P300 Development Board

The development board requires connection to a host microcontroller to

initialise the P300 chip and process the data to and from the chip. The P300

Chapter 4

40

communicates to the host microcontroller using the SPI14. The host

microcontroller and the network interface controller have a master/slave

relationship. The NIC15 can not send data to the host until commanded to do

so. The NIC can only request service from a host via an interrupt line. The host

must respond to the interrupt request with a command that allows the chip to

return its data. Commands from the host allow the host to read or write the

internal registers of the NIC [41]. When the P300 chip is first powered up or

after a power down reset it is required that the host microcontroller initialise the

Layer_Config_Info data structure. This data structure consists of 7 bytes and

includes such information as the device address. This register is written to by

first sending a Layer Management Write command (0x03) followed by the seven

data bytes. After each data byte has been successfully received by the NIC it

will generate another interrupt to the host which will then send through the next

byte [42]. This process is shown graphically in Figure 4.5: Flow Chart of P300

Initialisation.

Figure 4.5: Flow Chart of P300 Initialisation

14 Serial Peripheral Interface15 Network Interface Controller

Chapter 4

41

Figure 4.6: DomoSIP

Difficulties were encountered when attempting to perform this initialisation

routine. It seemed that the required interrupt was not generated by the NIC

every time that a byte was transferred serially from the host microcontroller to

the P300. On some occasions all seven data bytes were transmitted

successfully but most often they were not. This in turn meant that the

microcontroller had no means of knowing when to send the next byte. Attempts

to isolate the problem using a digital oscilloscope and logic analyser seemed to

indicate that the correct signals were on all of the pins and the failure lay with

the Intellon chip. Technical assistance was sought from the Engineers at

Intellon and screen captures of the generated signals were e-mailed to them but

they were unable to explain the lack of interrupts. A query posted to the

comp.home.automation newsgroup provided no solution but it did provoke a

thread dedicated to the unreliability of the Intellon product. Without being able

to even initialise the P300 chip there seemed little else to do than move on to

another product!

4.2.1.2 CEWay PL-111

Having dispensed with the P300 the next (and

preferred) product was the CEWay PL-111.

This is a power line communications transceiver

that implements the CEBus physical and data

link layers. The CEWay PL-111 includes a

proprietary DSP16 for superior performance in

noisy environments. The PL-111 is available in

a pre-mounted package that includes the

necessary amplification and filtering circuitry for

the CEBus spread spectrum chirp to be

transmitted and received. The pre-mounted

package is labelled the DomoSIP Power Line

Interface (shown in Figure 4.6: DomoSIP).

16 Digital Signals Processor

Chapter 4

42

The DomoSIP has a twenty pin SIP17 connector which can be simply plugged

into a matching socket to interface with the Auto-MATE PCB.

DomoSIP package necessitates the use of a host microcontroller to

implement the Auto-MATE modules. The DomoSIP board requires a 5 volt and

a 15 volt supply and it communicates to the host using the serial UART18

interface. The DomoSIP still requires additional circuitry to interface with the

power lines. This circuit is discussed next.

4.2.1.3 Peripheral CEBus Circuitry

Domosys provide the circuit schematic for the interface between the power line

and the DomoSIP board. This circuit was successfully implemented. The

circuit consists of a CEBus 12/12 turn transformer 100-400 kHz supplied by

General Magnetic Technologies, a high pass filter formed by R1 and C1 and on

either side of the transformer is a transient voltage surge suppressor indicated

by V1 and V2. The circuit schematic is included in Appendix A: Circuit

Schematics.

4.3 Microcontroller Selection

The selection of the DomoSIP board means that a host microcontroller is

necessary. A number of possible 8-bit devices were considered. The required

features were outlined in the previous chapter but in terms of hardware

development two additional requirements are availability and ease of

implementation. Considered microcontrollers were

Motorola 68HC11

PIC 16F871

ATMEL 90S4414

ATMEL 90S8535

The comparison of features and cost is presented in table 4.1: Comparison of

Microcontrollers.

17 Single Inline Package18 Universal Asynchronous Receiver Transmitter

Chapter 4

43

MCUProgram memory

EEPROM RAMExt

InterruptsIO pins

A/D Converter

UART Cost

68HC11 512 bytes none 128 1 40 8-bit yes $2816F871 4k bytes 128 128 1 32 10-bit yes $2090S4414 4k bytes 256 256 2 40 none yes $790S8535 8k bytes 512 512 2 40 10-bit yes $9

Table 4.1: Comparison of Microcontrollers

Of the reviewed microcontrollers the two ATMEL products had the

greatest range of features for the least cost and were available immediately.

The 4414 is ideal for use on the PC / power line interface circuit as this requires

less code and does not need an analogue to digital converter for the

implementation. The 8535 is suitable for the module development and excellent

development resources are available for the ATMEL products in terms of

product data and software compilers [43].

4.4 Load Control

As the Auto-MATE modules are designed to replace existing light switches and

power points within the home they must be capable of switching the loads that

are commonly connected in homes. All Australian homes use switches and

GPOs19 that are rated to a minimum of 10 Amps. Therefore a circuit capable of

switching this load and being controlled by the output of the host microcontroller

is required. For the purposes of light dimming the commonly used phase

control technique is utilised. For this method the load is switched on at varying

points in the AC waveform depending on the level of current and voltage

required. The time that the load is switched depends on a software delay. The

software requires a reference input corresponding to the zero voltage crossing

of the waveform. This is discussed next.

4.4.1Zero Voltage Crossing Detection

This circuit was implemented using a Sharp PC814 AC input photocoupler. The

input is connected via a resistor to the AC supply and the output stage of the

19 General Purpose Outlet

Chapter 4

44

coupler is connected to a 5 volt supply and a pull down resistor. During the

period when the AC waveform passes through 0.7 to 0.7 volts the output stage

does not conduct and an external interrupt on the microcontroller is pulled low.

4.4.2Load Switching

The switching of the 10 Amp load is facilitated by the use of a BTA 16 600B

Triac. The Triac is fired by a micro controller output pin through a MOC3041

Optoisolated Triac Driver. A snubber circuit consisting of a 100 Ohm resistor

and a 0.1 F capacitor enables the switching of inductive loads without damage

to the Triac.

4.5 Load Sensing

The load sensing functionality was included to add an element of intelligence to

the Auto-MATE design. The goal was not to provide a power measurement but

to simply give an indication of whether the load was connected. This circuit was

implemented by placing two power diodes in series with the connected load.

This provides a 1.4 volt drop across the diodes while current is conducting

through the load. A series combination of a Sharp PC814 photocoupler and a

100 Ohm resistor is placed in parallel with the diodes. While the current is

conducting the output stage of the 814 is conducting and a microcontroller pin is

held high.

4.6 Local Control Buttons

The Auto-MATE modules that are used for controlling lights and appliance loads

require local control at the switch or outlet. This was implemented simply using

a pushbutton for each operation (these being on, off, increment & decrement).

Each pushbutton is connected to an input pin of the microcontroller as well as

an input pin to a 74HCT02 CMOS NOR gate. The output of the NOR gate

generates an external interrupt on the host microcontroller then differentiating

between buttons is performed in software.

Chapter 4

45

4.7 Power Supplies

The Auto-MATE boards require a 5 volt and a 15 volt rail. These voltages are

supplied from a 240:18 volt transformer through a rectifier and then regulated

using a MC7805 and a MC7815 regulator respectively.

4.8 Temperature Sensing Circuit

As a feature of the Auto-MATE system a temperature sensing module allows for

control of climate sensitive devices to be activated or deactivated. The

temperature sensor selection was based on cost. The most economical sensor

available was the LMM 355 National Semiconductor [44]. This device produces

as linear change in output voltage for a change in temperature and has an

accuracy of 1 degree. The output of this sensor is connects to the A/D

converter input of the microcontroller.

4.9 Humidity Sensing Circuit

The humidity sensor selection was also based on cost. The chosen sensor was

the HU10 from Thermometrics [45]. This sensor provides a linear voltage

output with changes in humidity between 20 and 100 percent.

4.10Motion Detector Circuit

home automation thesis

Documents

automate system

knowledge of home automation

home automation maze

thesis entitledautomate

automate vision

automate features

thesis project

design advice