X-10 Home Automation -Content

MANI PRINCE SUBROTO SWAPAN KUMAR (06EC019)PATEL JIGAR MANUBHAI (06EC030)L D R P I n s t i t u t e o f T e c h n o l o g y & R e s e a r c h , G a n d h i n a g a r

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CONTENTSCONTENTS1. INTRODUCTION............................................................................................................................................5

1.11.1 HOME WIRING HISTORYHOME WIRING HISTORY............................................................................................................................6

1.21.2 OVERVIEW AND BENEFITSOVERVIEW AND BENEFITS.........................................................................................................................7

1.31.3 STANDARDS AND BRIDGESSTANDARDS AND BRIDGES........................................................................................................................8

1.41.4 SOME HOME AUTOMATION STANDARDSSOME HOME AUTOMATION STANDARDS.................................................................................................9

1.51.5 THE ELEMENTS OF A DOMOTICS SYSTEM ARE:THE ELEMENTS OF A DOMOTICS SYSTEM ARE:.......................................................................................11

1.61.6 ARCHITECTUREARCHITECTURE........................................................................................................................................11

1.6.11.6.1 CCENTRALIZEDENTRALIZED A ARCHITECTURERCHITECTURE...........................................................................................................11

1.6.21.6.2 DDISTRIBUTEDISTRIBUTED A ARCHITECTURERCHITECTURE...........................................................................................................11

1.6.31.6.3 MMIXEDIXED A ARCHITECTURERCHITECTURE.....................................................................................................................11

1.71.7 INTERCONNECTIONINTERCONNECTION.................................................................................................................................11

1.7.11.7.1 BBYY WIREWIRE::..........................................................................................................................................11

1.7.21.7.2 WWIRELESSIRELESS::........................................................................................................................................12

1.7.31.7.3 BBOTHOTH W WIRELESSIRELESS ANDAND W WIREIRE...............................................................................................................12

1.81.8 CLASSIFICATIONS OF DOMESTIC NETWORK TECHNOLOGIESCLASSIFICATIONS OF DOMESTIC NETWORK TECHNOLOGIES..................................................................12

1.8.11.8.1 DDEVICEEVICE INTERCONNECTIONINTERCONNECTION::.............................................................................................................12

1.8.21.8.2 CCONTROLONTROL ANDAND AUTOMATIONAUTOMATION NETSNETS::...................................................................................................12

1.8.31.8.3 DDATAATA NETSNETS::......................................................................................................................................13

1.91.9 TASKSTASKS......................................................................................................................................................13

1.9.11.9.1 HVACHVAC..............................................................................................................................................13

1.9.21.9.2 LLIGHTINGIGHTING.........................................................................................................................................13

1.9.31.9.3 NNATURALATURAL LIGHTINGLIGHTING..........................................................................................................................14

1.9.41.9.4 AAUDIOUDIO..............................................................................................................................................14

1.9.51.9.5 VVIDEOIDEO..............................................................................................................................................14

1.9.61.9.6 SSECURITYECURITY.........................................................................................................................................14

1.9.71.9.7 DDETECTIONETECTION OFOF POSSIBLEPOSSIBLE INTRUSIONINTRUSION.................................................................................................15

1.9.81.9.8 IINTERCOMSNTERCOMS.......................................................................................................................................15

1.9.91.9.9 RROBOTICSOBOTICS.........................................................................................................................................15

1.9.101.9.10 OOTHERTHER S SYSTEMSYSTEMS...............................................................................................................................15

1.101.10 COSTSCOSTS......................................................................................................................................................16

1.111.11 SMART GRIDSMART GRID............................................................................................................................................16


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2. X10 HOME AUTOMATION.........................................................................................................................17

2.12.1 POWER LINE CARRIER CONTROL OVERVIEWPOWER LINE CARRIER CONTROL OVERVIEW...........................................................................................18

2.22.2 X10 PROTOCOLX10 PROTOCOL........................................................................................................................................19

2.32.3 HOW DOES THE X-10 PROTOCOL WORK?HOW DOES THE X-10 PROTOCOL WORK?...............................................................................................19

2.42.4 LIST OF X10 COMMANDS:LIST OF X10 COMMANDS:.......................................................................................................................23

2.52.5 POWER LINE PROTOCOL PHYSICAL LAYER DETAILSPOWER LINE PROTOCOL PHYSICAL LAYER DETAILS.................................................................................24

2.62.6 THE RADIO PROTOCOLTHE RADIO PROTOCOL............................................................................................................................25

2.72.7 DEVICE MODULESDEVICE MODULES...................................................................................................................................26

2.82.8 CONTROLLERSCONTROLLERS.........................................................................................................................................27

2.92.9 X10 THEORYX10 THEORY............................................................................................................................................28

3. HARDWARE.................................................................................................................................................33

3.13.1 BASIC MODEL OF THE SYSTEMBASIC MODEL OF THE SYSTEM................................................................................................................34

3.23.2 SUMMARY OF MICROCONTROLLER RESOURCE USESUMMARY OF MICROCONTROLLER RESOURCE USE...............................................................................35

3.33.3 MEMORY USAGEMEMORY USAGE.....................................................................................................................................36

3.43.4 ZERO-CROSSING DETECTORZERO-CROSSING DETECTOR....................................................................................................................37

3.53.5 BASIC LOW FREQUENCY CIRCUITBASIC LOW FREQUENCY CIRCUIT............................................................................................................38

3.5.13.5.1 CCOMPARATORSOMPARATORS.................................................................................................................................41

3.63.6 120 KHZ CARRIER DETECTOR120 KHZ CARRIER DETECTOR...................................................................................................................44

3.73.7 120 KHZ CARRIER GENERATOR120 KHZ CARRIER GENERATOR................................................................................................................45

3.83.8 TRANSFORMER-LESS POWER SUPPLYTRANSFORMER-LESS POWER SUPPLY.....................................................................................................47

3.93.9 LOAD SWITCHLOAD SWITCH..........................................................................................................................................48

3.103.10 LCD MODULELCD MODULE...........................................................................................................................................49

3.113.11 REAL-TIME CLOCKREAL-TIME CLOCK...................................................................................................................................49

3.123.12 PUSH BUTTONSPUSH BUTTONS.......................................................................................................................................50

3.133.13 LIGHT SENSORLIGHT SENSOR.........................................................................................................................................50

3.143.14 IN-CIRCUIT DEBUGGER IN-CIRCUIT DEBUGGER...........................................................................................................................50

3.153.15 CONTROL DATA STORAGECONTROL DATA STORAGE.......................................................................................................................51

3.163.16 ENVELOPE DETECTORENVELOPE DETECTOR..............................................................................................................................52

3.16.13.16.1 DDEFINITIONEFINITION OFOF THETHE ENVELOPEENVELOPE.........................................................................................................53

3.16.23.16.2 DDIODEIODE DETECTORDETECTOR.............................................................................................................................54

3.16.33.16.3 PPRECISIONRECISION DETECTORDETECTOR.......................................................................................................................54


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3.16.43.16.4 DDRAWBACKSRAWBACKS.....................................................................................................................................54

3.16.53.16.5 DDEMODULATIONEMODULATION OFOF SIGNALSSIGNALS............................................................................................................55

3.16.63.16.6 AAUDIOUDIO..............................................................................................................................................55

3.173.17 SCOPE ADAPTER CIRCUITSCOPE ADAPTER CIRCUIT........................................................................................................................56

3.183.18 HIGH-PASS FILTERHIGH-PASS FILTER...................................................................................................................................57

3.18.13.18.1 FFIRSTIRST--ORDERORDER CONTINUOUSCONTINUOUS--TIMETIME IMPLEMENTATIONIMPLEMENTATION..........................................................................58

3.18.23.18.2 DDISCRETEISCRETE--TIMETIME REALIZATIONREALIZATION............................................................................................................59

4. ALL CIRCUIT DIAGRAM AT A SCOPE.....................................................................................................61

5. SOFTWARE...................................................................................................................................................66

5.15.1 APPLICATION FIRMWARE OVERVIEWAPPLICATION FIRMWARE OVERVIEW.....................................................................................................66

5.25.2 X-10 LIBRARYX-10 LIBRARY...........................................................................................................................................66

5.2.15.2.1 SSKIPKIPIIFFTTXXRREADYEADY...............................................................................................................................67

5.2.25.2.2 SSENDENDX10AX10ADDRESSDDRESS (H (HOUSEOUSE, U, UNITNIT))...................................................................................................67

5.2.35.2.3 SSENDENDX10AX10ADDRESSDDRESSVVARAR.....................................................................................................................68

5.2.45.2.4 SSENDENDX10CX10COMMANDOMMAND (H (HOUSEOUSE, F, FUNCTIONUNCTION))........................................................................................68

5.2.55.2.5 SSENDENDX10CX10COMMANDOMMANDVVARAR...................................................................................................................69

5.2.65.2.6 SSKIPKIPIIFFRRXXDDONEONE................................................................................................................................69

5.2.75.2.7 SSKIPKIPIIFFAADDRESSDDRESSRRCVDCVD.......................................................................................................................70

5.2.85.2.8 SSKIPKIPIIFFCCOMMANDOMMANDRRCVDCVD.....................................................................................................................70

5.2.95.2.9 RREADEADX10MX10MESSAGEESSAGE...........................................................................................................................70

5.35.3 INTRODUCTION TO KEIL SOFTWAREINTRODUCTION TO KEIL SOFTWARE.......................................................................................................71

5.45.4 WHAT IS ΜVISION3?WHAT IS ΜVISION3?...............................................................................................................................71

5.55.5 STEPS FOLLOWED IN CREATING AN APPLICATION IN ΜVISION3:STEPS FOLLOWED IN CREATING AN APPLICATION IN ΜVISION3:...........................................................71

5.65.6 DEVICE DATABASEDEVICE DATABASE...................................................................................................................................77

5.75.7 PERIPHERAL SIMULATIONPERIPHERAL SIMULATION.......................................................................................................................77

5.85.8 PROGRAMMERPROGRAMMER........................................................................................................................................77

5.95.9 PROLOAD PROGRAMMING SOFTWAREPROLOAD PROGRAMMING SOFTWARE..................................................................................................78

6. HOME CONTROLLER OPERATING INSTRUCTIONS.............................................................................80

6.16.1 “WELCOME SCREEN”“WELCOME SCREEN”..............................................................................................................................80

6.1.16.1.1 SSELECTELECT F FUNCTIONUNCTION S SCREENCREEN...............................................................................................................81

6.1.26.1.2 SSETET S SYSTEMYSTEM T TIMEIME S SCREENCREEN................................................................................................................82

6.1.36.1.3 SSELECTELECT S SYSTEMYSTEM A ADDRESSDDRESS S SCREENCREEN....................................................................................................83


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6.1.46.1.4 SSETET L LIGHTIGHT S SENSORENSOR S SCREENCREEN..............................................................................................................84

6.1.56.1.5 PPROGRAMROGRAM U UNITNIT S SCREENCREEN...................................................................................................................85

7. WEAK POINTS AND LIMITATIONS..........................................................................................................86

7.17.1 COMPATIBILITY WITH INSTALLED WIRING AND APPLIANCESCOMPATIBILITY WITH INSTALLED WIRING AND APPLIANCES.................................................................86

7.27.2 COMMANDS GETTING LOSTCOMMANDS GETTING LOST...................................................................................................................87

7.37.3 RELATIVELY SLOWRELATIVELY SLOW...................................................................................................................................88

7.47.4 LIMITED FUNCTIONALITYLIMITED FUNCTIONALITY........................................................................................................................88

7.57.5 INTERFERENCE AND LACK OF ENCRYPTIONINTERFERENCE AND LACK OF ENCRYPTION............................................................................................88

7.67.6 BRIDGESBRIDGES..................................................................................................................................................88

8. ADVANTAGE...............................................................................................................................................89

9. CONCLUSION...............................................................................................................................................90

10. TROUBLE SHOOTING.............................................................................................................................91


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1. INTRODUCTION

e live in a world where everything can be controlled and operated

automatically, but there are still a few important sectors in our country where

automation has not been adopted or not been put to a full-fledged use, perhaps because

of several reasons one such reason is cost. One such field is that of Home Automation.

W

Home automation (also called Domotics) designates an emerging practice of

increased automation of household appliances and features in residential dwellings,

particularly through electronic means that allow for things impracticable, overly

expensive or simply not possible in recent past decades. The term may be used in

contrast to the more mainstream "building automation", which refers to industrial uses of

similar technology, particularly the automatic or semi-automatic control of lighting,

doors and windows, Heating, Ventilation and Air Conditioning, and security and

surveillance systems.

The techniques employed in home automation include those in building

automation as well as the control of home entertainment systems, houseplant watering,

pet feeding, changing the ambiance "scenes" for different events (such as dinners or

parties), and the use of domestic robots.

Typically, it is easier to more fully outfit a house during construction due to the

accessibility of the walls, outlets, and storage rooms, and the ability to make design

changes specifically to accommodate certain technologies. Wireless systems are

commonly installed when outfitting a pre-existing house, as they obviate the need to

make major structural changes. These communicate via radio or infrared signals with a

central controller.


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1.11.1 HOME WIRING HISTORYHOME WIRING HISTORY

Traditionally, homes have been wired for four systems: electrical power,

telephones, TV outlets (cable or antenna), and a doorbell. Typically, components and

wiring for these are kept within a closet, power metering box or a patch panel.

A television remote control was first

patented in 1950, [citation needed] and a remote

control device was first used by the Germans in

World War I to control motorboats. With the

invention of the electronic micro (auto)

controller and the widespread uptake of digital

communication technology, the cost of

electronic control fell rapidly and reliability

improved. Remote and intelligent control

technologies were adopted by the building

services industry and appliance manufacturers

worldwide, as they offer the end user easily

accessible and/or greater control of their

products.


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1.21.2 OVERVIEW AND BENEFITSOVERVIEW AND BENEFITS

As the amount of controllable fittings and domestic appliances in the home rises,

the ability of these devices to interconnect and communicate with each other digitally

becomes a useful and desirable feature. The consolidation of control or monitoring

signals from appliances, fittings or basic services is an aim of Home automation.

In simple installations this may be as straightforward as turning on the lights when

a person enters the room. In advanced installations, rooms can sense not only the

presence of a person inside but know who that person is and perhaps set appropriate

lighting, temperature, music levels or television channels, taking into account the day of

the week, the time of day, and other factors. Other automated tasks may include setting

the air conditioning to an energy saving setting when the house is unoccupied, and

restoring the normal setting when an occupant is about to return. More sophisticated

systems can maintain an inventory of products, recording their usage through an RFID

tag, and prepare a shopping list or even automatically order replacements. Home

automation can also provide a remote interface to home appliances or the automation

system itself, via telephone line, wireless transmission or the internet, to provide control

and monitoring via a Smart Phone or Web browser. An example of a remote monitoring

implementation of home automation could be when a smoke detector detects a fire or

smoke condition, and then all lights in the house will blink to alert any occupants of the

house to the possible fire. If the house is equipped with a home theatre, a home

automation system can shut down all audio and video components to display the alert or

make an audible announcement. The system could also call the home owner on their

mobile phone to alert them, or call the fire brigade or alarm monitoring company to bring

it to their attention.


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1.31.3 STANDARDS AND BRIDGESSTANDARDS AND BRIDGES

There have been many attempts to standardise the forms of hardware, electronic

and communication interfaces needed to construct a home automation system. Specific

domestic wiring and communication standards include:

BACnetINSTEONX10KNX (Standard)LonWorksC-BusSCS BUS with OpenWebNetUniversal Powerline bus (UPB)ZigBeeZ-Wave

Some standards use additional communication and control wiring, some embed

signals in the existing power circuit of the house, some use radio frequency (RF) signals,

and some use a combination of several methods. Control wiring is hardest to retrofit into

an existing house. Some appliances include USB that is used to control it and connect it

to a domotics network. Bridges translate information from one standard to another (eg.

from X10 to European Installation Bus).


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1.41.4 SOME HOME AUTOMATION STANDARDSSOME HOME AUTOMATION STANDARDS

Technology Transmission medium Transmission speedMaximum distance to the device

Ethernet {IEEE 802.3}

Unshielded twisted pair 10 Mbit/s – 1 Gbit/s 100 m

Optical fiber 1 Gbit/s – 10 Gbit/s 2 km – 15 km

HomePlug {IEEE P1901}Electrical wiring 14 Mbit/s - 200 Mbit/s 200 m

Universal Powerline AssociationElectrical wiring 200 Mbit/s 200 m

ITU G.hn {G.9960}Electrical wiring / Telephone line / Coaxial cable

up to 1 Gbit/s N/A

HomePNA {G.9951, G.9952, G.9953, and G.9954}

Telephone line 10 Mbit/s 300 m

Wi-Fi {IEEE 802.11}Radio frequency 11 Mbit/s – 248 Mbit/s 30 m – 100 m

FireWire {IEEE 1394}Unshielded twisted pair / Optical fiber 400 Mbit/s – 3.2

Gbit/s4.5 m – 70 m

Bluetooth {IEEE 802.15.1 (v1.1 only)}

Radio frequency 1 Mbit/s – 10 Mbit/s 10 m – 100 m

IRDAInfrared 9600 bit/s – 4 Mbit/s 2 m

C-BusTwisted pair / Electrical wiring / Radio frequency / Infrared / Ethernet / Wi-Fi

1200 bit/s – 9600 bit/s 1000 m


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LonWorks {ISO/IEC 14908}

Twisted pair / Electrical wiring / Radio frequency / Infrared / Coaxial /Optical fiber / IP tunneling

1.70 kbit/s – 1.28 Mbit/s

1500 m – 2700 m

INSTEON

Electrical wiring / Radio frequency 1.2 kbit/s 1,000 m+ (Electrical wiring), 50 m+ (Wireless)

X10Electrical wiring 50 bit/s – 60 bit/s

European Installation Bus / KNX {ISO/IEC 14543-3}

Twisted pair / Electrical wiring / Radio frequency / Infrared / Ethernet

1200 bit/s – 9600 bit/s 300 m – 1000 m

EHSTwisted pair / Electrical wiring 2.4 kbit/s – 48 kbit/s

BatibusTwisted pair 4800 bit/s 200 m – 1500

m

ZigBee / ZigBee Pro{IEEE 802.15.4 (radio-layer only, not

protocol)}

Radio frequency 20 kbit/s – 250 kbit/s 10 m – 1500 m

Z-WaveRadio frequency 9.6 kbit/s – 40 kbit/s 1 m – 75 m

USBTwisted pair 12 Mbit/s – 480 Mbit/s 5 m

Table: 1.1


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1.51.5 THE ELEMENTS OF A DOMOTICS SYSTEM ARE:THE ELEMENTS OF A DOMOTICS SYSTEM ARE:

Hardware controllers or software controllers

Sensors

Actuators

1.61.6 ARCHITECTUREARCHITECTURE

From the point of view of where the intelligence of the domotic system resides, there are three different architectures:

1.6.11.6.1 CCENTRALIZEDENTRALIZED A ARCHITECTURERCHITECTURE

A centralized controller receives information of multiple sensors and, once processed, generates the opportune orders for the actuators.

1.6.21.6.2 DDISTRIBUTEDISTRIBUTED A ARCHITECTURERCHITECTURE

All the intelligence of the system is distributed by all the modules that are sensors or actuators. Usually it is typical of the systems of wiring in bus.

1.6.31.6.3 MMIXEDIXED A ARCHITECTURERCHITECTURE

Systems with decentralized architecture as far as which they have several small devices able to acquire and to process the information of multiple sensors and to transmit them to the rest of devices distributed by the house.

1.71.7 INTERCONNECTIONINTERCONNECTION

1.7.11.7.1 BBYY WIREWIRE::

Optical fiberCable (coaxial and twisted pair), including : xDSLPowerline, including : INSTEONX10


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1.7.21.7.2 WWIRELESSIRELESS::

Radio frequency, including: INSTEONWi-FiGPRS and UMTSBluetoothDECTZigBeeZ-WaveONE-NETEnOceanInfra-red, including : Consumer IR

1.7.31.7.3 BBOTHOTH W WIRELESSIRELESS ANDAND W WIREIRE

INSTEON

1.81.8 CLASSIFICATIONS OF DOMESTIC NETWORKCLASSIFICATIONS OF DOMESTIC NETWORK TECHNOLOGIESTECHNOLOGIES

1.8.11.8.1 DDEVICEEVICE INTERCONNECTIONINTERCONNECTION::

FireWireBluetoothUSBIrDA

1.8.21.8.2 CCONTROLONTROL ANDAND AUTOMATIONAUTOMATION NETSNETS::

C-Bus (protocol)Universal Powerline BusKonnexLonworksX10ONE-NETEIBEHSBatiBUS


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ZigBeeEnOceanSCS BUS - OpenWebNet

1.8.31.8.3 DDATAATA NETSNETS::

EthernetHomeplugHomePNAWiFi

1.91.9 TASKSTASKS

1.9.11.9.1 HVACHVAC

Heating, Ventilation and Air Conditioning (HVAC) solutions include temperature

and humidity control. This is generally one of the most important aspects to a

homeowner. An Internet-controlled thermostat, for example, can both save money and

help the environment, by allowing the homeowner to control the building's heating and

air conditioning systems remotely.

1.9.21.9.2 LLIGHTINGIGHTING

Lighting control systems can be used to control household electric lights in a

variety of ways:

Extinguish all the lights of the house.

Replace manual switching with Automation of on and off signals for any or all

lights.

Regulation of electric illumination levels according to the level of ambient light

available.

Change the ambient color of lighting via control of LEDs or electronic dimmers


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1.9.31.9.3 NNATURALATURAL LIGHTINGLIGHTING

Natural lighting control involves controlling window shades, LCD shades,

draperies and awnings. Recent advances include use of RF technology to avoid wiring to

switches and integration with third party home automation systems for centralized

control.

1.9.41.9.4 AAUDIOUDIO

This category includes audio switching and distribution. Audio switching determines the selection of an audio source. Audio distribution allows an audio source to be heard in one or more rooms. This feature is often referred to as 'multi-zone' audio.

There are three major components that allow listen to audio throughout your home, or business:

CAT 5e/ CAT6 cable from a central audio unit.

A keypad to control volume and sources.

2 sets of speaker cabling (4 ply from amplifier, and 2 ply from key pad to the

speakers).

1.9.51.9.5 VVIDEOIDEO

This includes video switching and distribution, allowing a video source to be viewed on multiple TVs. This feature is often referred to as 'multi-zone' video. Integration of the intercom to the telephone, or of the video door entry system to the television set, allowing the residents to view the door camera automatically.

1.9.61.9.6 SSECURITYECURITY

With Home Automation, the consumer can select and watch cameras live from an Internet source to their home or business. Security cameras can be controlled, allowing the user to observe activity around a house or business right from a Monitor or touch panel. Security systems can include motion sensors that will detect any kind of unauthorized movement and notify the user through the security system or via cell phone.


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1.9.71.9.7 DDETECTIONETECTION OFOF POSSIBLEPOSSIBLE INTRUSIONINTRUSION

Sensors of detection of movement

Sensors of magnetic contact of door/window

Sensors of glass breaking

Sensors of pressure changes

Simulation of presence.

Detection of fire, gas leaks, water leaks (see fire alarm and gas alarm)

Medical alert. Teleassistance.

Precise and safe closing of blinds.

1.9.81.9.8 IINTERCOMSNTERCOMS

An intercom system allows communication via a microphone and loud speaker

between multiple rooms. Ubiquity in the external control as much internal, remote

control from the Internet, PC, wireless controls (eg. PDA with WiFi), electrical

equipment.

Transmission of alarms.

Intercommunications.

1.9.91.9.9 RROBOTICSOBOTICS

Control of home robots, using if necessary domotic electric beacon.

Home robot communication (i.e. using WiFi) with the domotic network and other home

robots.

1.9.101.9.10 OOTHERTHER S SYSTEMSYSTEMS

A homemade Internet-enabled cat feeder. Using special hardware, almost any device can be monitored and controlled automatically or remotely.


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Including:

Coffee pot

Garage door

Pet feeding and watering

Plant watering

Pool pump(s) and heater, Hot tub and Spa

Sump Pump

1.101.10 COSTSCOSTS

An automated home can be a very simple grouping of controls, or it can be heavily

automated where any appliance that is plugged into electrical power is remotely

controlled. Costs mainly include equipment, components, furniture, and custom

installation.

1.111.11 SMART GRIDSMART GRID

In 2009 President Barack Obama asked the United States Congress "to act without

delay" to pass legislation that included doubling alternative energy production in the next

three years and building a new electricity "smart grid". On April 13, 2009, George W.

Arnold was named the first National Coordinator for Smart Grid Interoperability. In June

2009, the NIST announced a smart grid interoperability project via IEEE P2030.

Home automation technologies like Zigbee, INSTEON and Zwave are viewed as

integral additions to the Smart Grid. The ability to control lighting, appliances, HVAC as

well as Smart Grid applications (load shedding, demand response, real-time power usage

and price reporting) will become vital as Smart Grid initiatives are rolled out.


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2. X10 HOME AUTOMATION

10 is an international and open industry standard for communication among

electronic devices used for home automation, also known as domotics. It

primarily uses power line wiring for signaling and control, where the signals involve

brief radio frequency bursts representing digital information. A wireless radio based

protocol transport is also defined.

X

X10 was developed in 1975 by PICO Electronics of Glenrothes, Scotland, in order

to allow remote control of home devices and appliances. It was the first general

purposedomotic network technology and remains the most widely available.The official

website for PICO Electronics is “http://www.picoelectronics.com/”. Although a number

of higher bandwidth alternatives exist including KNX, INSTEON, BACnet, and

LonWorks, X10 remains popular in the home environment with millions of units in use

worldwide, and inexpensive availability of new components. Plug-in modules available

from various vendors enable users to create home automation systems by using the AC

wiring ready installed within a home.

PIC® microcontrollers can easily be used in conjunction with X-10 technology to

create home automation applications. The specific PIC microcontroller (MCU) used

should be selected based on RAM, ROM, operating frequency, peripheral, and cost

requirements of the particular application. The PIC16F877A was selected for this

application because of its versatility as a general purpose microcontroller, its Flash

program memory (for ease of development), data EEPROM and ample I/O. This

application note discusses the implementation of X-10 on a PIC MCU to create a home

controller that can both send and receive X-10 signals. The reader may implement the

home controller as is, or adapt the circuits and firmware to other applications. A library


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of X-10 functions is provided to facilitate development of other X-10 applications using

PIC MCUs.

2.12.1 POWER LINE CARRIER CONTROL OVERVIEWPOWER LINE CARRIER CONTROL OVERVIEW

Household electrical wiring (the same which powers lights and appliances) is used

to send digital data between X10 devices. This digital data is encoded onto a 120 kHz

carrier which is transmitted as bursts during the relatively quiet zero crossings of the 50

or 60 Hz AC alternating current waveform. One bit is transmitted at each zero crossing.

The digital data consists of an address and a command sent from a controller to a

controlled device. More advanced controllers can also query equally advanced devices to

respond with their status. This status may be as simple as "off" or "on", or the current

dim level, or even the temperature or other sensor reading. Devices usually plug into the

wall where a lamp, television, or other household appliance plugs in; however some

built-in controllers are also available for wall switches and ceiling fixtures.

carrying the signal cannot pass through a

power transformer or across the phases of a

multiphase system. For split phase systems, the

signal can be passively coupled from phase-to-phase

using a passive capacitor, but for three phase

systems or where the capacitor provides insufficient

coupling, an active X10 repeater can be used. To allow signals be coupled across phases

and still match each phase's zero crossing point, each bit is transmitted three times in

each half cycle, offset by 1/6th cycle.

It may also be desirable to block X10 signals from leaving the local area so, for

example, the X10 controls in one house don't interfere with the X10 controls in a


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neighboring house. In this situation, inductive filters can be used to attenuate the X10

signals coming into or going out of the local area.

2.22.2 X10 PROTOCOLX10 PROTOCOL

Whether using power line or radio communications, packets transmitted using the

X10 control protocol consist of a four bit house code followed by one or more four bit

unit code, finally followed by a four bit command. For the convenience of users

configuring a system, the four bit house code is selected as a letter from A through P

while the four bit unit code is a number 1 through 16.

When the system is installed, each controlled device is configured to respond to

one of the 256 possible addresses (16 house codes × 16 unit codes); each device reacts to

commands specifically addressed to it, or possibly to several broadcast commands.

The protocol may transmit a message that says "select code A3", followed by "turn

on", which commands unit "A3" to turn on its device. Several units can be addressed

before giving the command, allowing a command to affect several units simultaneously.

For example, "select A3", "select A15", "select A4", and finally, "turn on", causes units

A3, A4, and A15 to all turn on.

2.32.3 HOW DOES THE X-10 PROTOCOL WORK?HOW DOES THE X-10 PROTOCOL WORK?

X-10 transmissions are synchronized with the zero-crossings on the AC power line. By

monitoring for the zero-crossings, X-10 devices know when to transmit or receive X-10

information. A binary ‘1’ is represented by a 1 ms long burst of 120 kHz, near the zero-

crossing point of the AC. A binary zero is represented by the lack of the 120 kHz burst.


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X-10 TRANSMISSION TIMING

Note 1: These 120 kHz carrier bursts are timed to coincide with the zero-crossing of the

other phases, when implemented.

A complete X-10 message is composed of a start code (1110), followed by a house code,

followed by a key code. The key code may be either a unit address or a function code,

depending on whether the message is an address or a command. Table 1 and Table 2

show the possible values of the house and key codes.


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TABLE 1: HOUSE CODES TABLE A-2: KEY CODES

When transmitting the codes in Table 1 and Table 2, two zero-crossings are used to

transmit each bit as complementary bit pairs (i.e., a zero is represented by 0-1, and a one

is represented by 1-0). For example, in order to send the house code A, the four-bit code

in Table A-1 is 0110, and the code transmitted as complimentary bit pairs is 01101001.

Since house and key codes are sent using the complimentary format, the start code is the

only place where the pattern 1110 will appear in an X-10 data stream.

The key code, which is 5-bits long in Table 2, takes 10 bits to represent in the

complimentary format. Because the last bit of the key code is always zero for a unit

address and one for a function code, the last bit of the key code can be treated as a suffix


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that denotes whether the key code is a unit address or function code. A complete block of

data consists of the start code, house code, key code and suffix. Each data block is sent

twice, with 3 power line cycles, or six zero-crossings, between each pair of data blocks.

For example, to turn on an X-10 module assigned to house code A, unit 2, the following

data stream would be sent on the power line, one bit per zero-crossing.

First, send the address twice:

Next, wait for three cycles (six zero-crossings):

000000

Then, send the command twice:

Lastly, wait for three cycles (six zero-crossings) before sending the next block:

000000

There are exceptions to this format. For example, the bright and dim codes do not require

the 3-cycle wait between consecutive dim commands or consecutive bright commands.


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2.42.4 LIST OF X10 COMMANDS:LIST OF X10 COMMANDS:

Code Function Description

0 0 0 0 All units off Switch off all devices with the house code indicated in the message

0 0 0 1 All lights on Switches on all lighting devices (with the ability to control brightness)

0 0 1 0 On Switches on a device

0 0 1 1 Off Switches off a device

0 1 0 0 Dim Reduces the light intensity

0 1 0 1 Bright Increases the light intensity

0 1 1 1 Extended code Extension code

1 0 0 0 Hail request Requests a response from the device(s) with the house code indicated in the message

1 0 0 1 Hail acknowledge Response to the previous command

1 0 1 x Pre-set dim Allows the selection of two predefined levels of light intensity

1 1 0 1 Status is on Response to the Status Request indicating that the device is switched on

1 1 1 0 Status is off Response indicating that the device is switched off

1 1 1 1 Status request Request requiring the status of a device


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2.52.5 POWER LINE PROTOCOL PHYSICAL LAYER DETAILSPOWER LINE PROTOCOL PHYSICAL LAYER DETAILS

In the 60 Hz AC current flow, a bit value of one is represented by a 1 millisecond

burst of 120 kHz at the zero crossing point (nominally 0°, but within 200 microseconds

of the zero crossing point), immediately followed by the absence of a pulse. A zero value

is represented by the absence of 120 kHz at the zero crossing point (pulse), immediately

followed by the presence of a pulse. All messages are sent twice to reduce false

signaling. After allowing for retransmission, line control, etc, data rates are around 20

bit/s, making X10 data transmission so slow that the technology is confined to turning

devices on and off or other very simple operations.

In order to provide a predictable start point, every data frame transmitted always

begin with a start code of 1110. Immediately after the start code, a house code (A–P)

appears, and after the letter code comes afunction code. Function codes may specify a

unit number code (1–16) or a command code, the selection between the two modes being

determined by the last bit where 0=unit number and 1=command. One start code, one

letter code, and one function code is known as an X10 frame and represent the minimum

components of a valid X10 data packet.

Each frame is sent twice in succession to make sure the receivers understand it

over any power line noise for purposes of redundancy, reliability, and to accommodate

line repeaters.

Whenever the data changes from one address to another address, from an address

to a command, or from one command to another command, the data frames must be

separated by at least 6 clear zero crossings (or "000000"). The sequence of six zeros

resets the device decoder hardware.


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2.62.6 THE RADIO PROTOCOLTHE RADIO PROTOCOL

To allow the operation of wireless keypads, remote

switches, and the like, a radio protocol is also defined.

Operating at a frequency of 310 MHz in the U.S. and 433

MHz inEuropean systems, the wireless devices send data

packets that are very similar to ordinary X10 power line

control packets. A radio receiver then provides a bridge

which translates these radio packets to ordinary X10 power line control packets.

The devices available using the radio protocol include:

Keypad controllers ("clickers").

Keychain controllers that can control one to four X10 devices.

Burglar alarm modules that can transmit sensor data.

Passive infrared switches to control lighting and X-10 chimes.

Non-passive information bursts.


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2.72.7 DEVICE MODULESDEVICE MODULES

Depending on the load that is to be controlled,

different modules must be used. For incandescent lamp

loads, a lamp module or wall switch module can be used.

These modules switch the power using a TRIAC solid state

switch and are also capable of dimming the lamp load.

Lamp modules are almost silent in operation, and generally

rated to control loads ranging from around 40 watts to 500

watts.

For loads other than incandescent lamps, such as fluorescent lamps, high-intensity

discharge lamps, and electrical home appliances, the TRIAC-based electronic switching

in the lamp module is unsuitable and an appliance module must be used instead. These

modules switch the power using an impulse relay. Many device modules offer a feature

called local control. If the module is switched off, operating the power switch on the

lamp or appliance will cause the module to turn on. In this way, a lamp can still be lit or

a coffee pot turned on without the need to use an X10 controller. Wall switch modules

may not offer this feature. Some wall switch modules offer a feature called local

dimming. Ordinarily, the local push button of a wall switch module simply offers on/off

control with no possibility of locally dimming the controlled lamp. If local dimming is

offered, holding down the push button will cause the lamp to cycle through its brightness

range. Higher end modules have more advanced features such as programmable on

levels, customizable fade rates, the ability to transmit commands when used (referred to

as 2-way devices), and scene support.There are sensor modules that sense and report

temperature, light, infra-red, motion, or contact openings and closures. Device modules

include thermostats, audible alarms and controllers for low voltage switches.


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2.82.8 CONTROLLERSCONTROLLERS

X10 controllers range from extremely simple to

very sophisticated.

The simplest controllers are arranged to control four

X10 devices at four sequential addresses (1–4 or 5–8).

The controllers typically contain the following buttons:

Unit 1 on/off

Unit 2 on/off

Unit 3 on/off

Unit 4 on/off

Brighten/dim (last selected unit)

All lights on/all units off

More sophisticated controllers can control more units and/or incorporate timers

that perform preprogrammed functions at specific times each day. Units are also

available that use passive infrared motion detectors or photocells to turn lights on and off

based on external conditions. Finally, very sophisticated units are available that can be

fully programmed or, like the X10 Firecracker, use a program running in an external

computer. These systems can execute many different timed events, respond to external

sensors, and execute, with the press of a single button, an entire scene, turning lights on,

establishing brightness levels, and so on. Control programs are available for computers

running Microsoft Windows, Apple's Macintosh, Linux and FreeBSD operating systems.

Burglar alarm systems are also available. In these systems, the controller uses X10

protocols or ordinary wiring to interrogate a number of remote sensors that may monitor

doors, windows, and other access points. The controller may then use X10 protocols to

activate lights, sirens, etc.


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2.92.9 X10 THEORYX10 THEORY

X-10 communicates between transmitters and receivers by sending and receiving

signals over the power line wiring. These signals involve short RF bursts which represent

digital information.

X10 transmissions are synchronized to the zero

crossing point of the AC power line. The goal should

be to transmit as close to the zero crossing point as

possible, but certainly within 200 microseconds of the

zero crossing point. The PL513 and TW523 provide a

60 Hz square wave with a maximum delay of 100 microseconds from the zero crossing

point of the AC power line. The maximum delay between signal envelope input and 120

kHz output bursts is 50 microseconds. Therefore, it should be arranged that outputs to

the PL513 and TW523 be within 50 microseconds of this 60 Hz zero crossing reference

square wave.

A Binary 1 is represented by a 1 millisecond

burst of 120 kHz at the zero crossing point, and a

Binary 0 by the absence of 120 kHz. The PL513 and

TW523 modulate their inputs (from the O.E.M.) with

120 kHz, therefore only the 1 ms "envelope" need be applied to their inputs. These 1

millisecond bursts should equally be transmitted three times to coincide with the zero

crossing point of all three phases in a three phase distribution system. Figure 1 shows the

timing relationship of these bursts relative to zero crossing.


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A complete code transmission encompasses

eleven cycles of the power line. The first two

cycles represent a Start Code. The next four

cycles represent the House Code and the last

five cycles represent either the Number Code (1

thru 16) or a Function Code (On, Off, etc.). This

complete block, (Start Code, House Code, Key

Code) should always be transmitted in groups of

2 with 3 power line cycles between each group

of 2 codes. Bright and dim are exceptions to this

rule and should be transmitted continuously (at

least twice) with no gaps between codes. See

Figure 2

Within each block of data, each four or

five bit code should be transmitted in true compliment form on alternate half cycles of

the power line. I.E. if a 1 millisecond burst of signal is transmitted on one half cycle

(binary 1) then no signal should be transmitted on the next cycle, (binary 0). See Figure

3. The Tables in Figure 4 show the binary codes to be transmitted for each House Code

and Key Code. The Start Code is always 1110 which is a unique code and is the only

code which does not follow the true complimentary relationship on alternate half cycles.

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 Housecode if a "Hail Acknowledge"

is received. 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.

The Extended Data code is followed by 8 bit bytes which can represent Analog

Data (after A to D conversion). There should be no gaps between the Extended Data


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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.

NOTE 1. X10 Receiver Modules require a "silence" of at least 3 power cycles

between each pair of 11 bit code transmissions (no gaps between each pair). The one

exception to this rule is bright and dim codes. These are transmitted continuously with

no gaps between each 11 bit dim code or 11 bit bright code. A 3 cycle gap is necessary

between different codes, i.e. between bright and dim, or 1 and dim, or on and bright, etc.

NOTE 2. The TW523 Two-Way Power Line Interface cannot receive Extended

Code or Extended Data because these codes have no gaps between them. The TW523

can only receive standard "pairs" of 11 bit X10 codes with 3 power line cycle gaps

between each pair.

NOTE 3. The TW523 can receive dim and bright codes but the output will

represent the first dim or bright code received, followed by every third code received. i.e.

the output from the TW523 will not be a continuous stream of dim and bright codes like

the codes which are transmitted.


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A Square wave representing zero

crossing detect is provided by the

PL513/TW523 and is within 100

microseconds of the zero crossing point of the

AC power line. The output signal envelope

from the O.E.M. should be within 50 microseconds of this zero crossing detect. The

signal envelope should be 1 ms (-50 microseconds +100 microseconds). See Figure 5

Opto-Coupled 60 Hz reference output (from the PL513/TW523) Transmissions are

to be synchronized to the zero crossing point of the AC power line and should be as

close to true zero crossing as possible. The PL513 and TW523 are designed to be

interfaced to other microprocessor circuitry which outputs X10 codes synchronized to

the zero crossing point of the AC power line. It is therefore necessary to provide a zero

crossing reference for the O.E.M. microprocessor. It is likely that this microprocessor

will have its own "isolated" power supply. It is necessary to maintain this isolation,

therefore the trigger circuit normally used in X10 POWERHOUSE controllers is not

desirable as this would reference the O.E.M. power supply to the AC power line. It is

also not desirable to take the trigger from the secondary side of the power supply

transformer as some phase shift is likely to occur. It is therefore necessary to provide an

opto-coupled 60 Hz reference.

An opto-coupled 60 Hz square wave is provided at the output of the PL513 and

TW523. X10 codes generated by the O.E.M. product are to be synchronized to this zero

crossing reference. The X10 code envelope generated by the O.E.M. is applied to the

PL513 or TW523 which modulates the envelope with 120 kHz and capacitively couples

it to the AC power line.


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Opto-Coupled Signal Input (to the PL513/TW523)

The input signal required from the O.E.M. product is the signal "envelope" of the X10 code format, i.e.

High for 1 ms. coincident with zero crossing represents a binary "1" and gates the

120 kHz oscillator through to the output drive circuit thus transmitting 120 kHz onto the

AC power line for 1 ms.

Low for 1 ms. coincident

with the zero crossing point

represents a binary "0" and turns

the 120 kHz oscillator/output

circuit off for the duration of the 1 ms. input.

Opto-Coupled Signal Output (from the TW523)

The "X10 received" output from the TW523 coincides with the second half of

each X10 transmission. This output is the envelope of the bursts of 120 kHz received.

Only the envelope corresponding to the first burst of each group of 3 bursts is available

at the output of the TW523. See Figures 6, 7 and 8.


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3. HARDWARE

he home controller application described in this application note allows the user to

program on and off times for up to sixteen devices, using a 2 x 16 liquid crystal

display and five push buttons. A built-in light sensor can be used to turn on lights at

dusk, and turn them off at dawn. The home controller is designed to facilitate

experimentation with home automation using the PIC16F877A. In addition to the

PIC16F877A, the board will accept any other PIC MCU that shares the same pinout,

such as the PIC18F452. Therefore, experimenters may expand on the application using

the higher performance of the PIC18 family of parts without changing the hardware.

With care, engineers and home control enthusiasts can experiment with home automation

using the MPLAB ICD 3 development tool. However, proper circuit isolation

precautions must be taken to avoid damage to your computer or development tools.

T


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3.13.1 BASIC MODEL OF THE SYSTEMBASIC MODEL OF THE SYSTEM

An overview of the home controller application hardware is shown in Figure

The hardware functionality of X-10 circuitry can be divided into four functional

blocks:

Zero-crossing detector

120 kHz carrier detector

120 kHz signal generator

Transformer less power supply

There are several application functions that are not directly associated with the X-

10 interface. User interface functions are accomplished with an LCD display and five

push buttons. A real-time clock is created using Timer1 and an external 32 kHz

oscillator. User modified control data, such as unit on and off times, are stored in the PIC

MCU’s built-in EEPROM. A light sensor and load switch are also used in this

application.


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3.23.2 SUMMARY OF MICROCONTROLLER RESOURCE USESUMMARY OF MICROCONTROLLER RESOURCE USE


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3.33.3 MEMORY USAGEMEMORY USAGE

Memory usage for the X-10 portion of the application is summarized in Table below

SUMMARY OF MEMORY USAGE FOR X-10 FUNCTIONALITY

Memory usage for the entire home controller application is summarized in Table below

SUMMARY OF MEMORY USAGE FOR THE HOME CONTROLLER


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3.43.4 ZERO-CROSSING DETECTORZERO-CROSSING DETECTOR

In X-10, information is timed with the zero-crossings of the AC power. A zero-

crossing detector is easily created by using the external interrupt on the RB0 pin and just

one external component, a resistor, to limit the current into the PIC MCU. In the United

States, Vrms = 117 VAC, and the peak line voltage is 165V. If we select a resistor of 5

MΩ, Ipeak = 165V/5 MΩ = 33 μA, which is well within the current capacity of a PIC

MCU I/O pin. Input protection diodes (designed into the PIC MCU I/O pins) clamp any

voltage higher than VDD or lower than VSS. Therefore, when the AC voltage is in the

negative half of its cycle, the RB0 pin will be clamped to VSS - 0.6V. This will be

interpreted as a logic zero. When the AC voltage rises above the input threshold, the

logical value will become a ‘1’. In this application, RB0 is configured for external

interrupts, and the input buffer is a Schmitt trigger. This makes the input threshold 0.8

VDD = 4V on a rising edge and 0.2 VDD = 1V on a falling edge. Upon each interrupt,

the Interrupt Edge Select bit within the OPTION_REG register is toggled so that an

interrupt occurs on every zero-crossing. Using the following equation, it is possible to

calculate when the pin state will change relative to the zero-crossing:

V = Vpk*sin(2*π*f*t),

where Vpk = 165Vand f = 60 Hz On a rising edge, RB0 will go high about 64 μs after

the zero-crossing, and on a falling

edge, it will go low about 16 μs before

the zero-crossing. More information on

interfacing PIC MCUs to AC power

lines can be found in the application

note AN521, “Interfacing to AC Power

Lines”, which is available for download from the Microchip web site.


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A zero crossing detector literally detects the transition of a signal waveform from

positive and negative, ideally providing a narrow pulse that coincides exactly with the

zero voltage condition. At first glance, this would appear to be an easy enough task, but

in fact it is quite complex, especially where high frequencies are involved. In this

instance, even 1 kHz starts to present a real challenge if extreme accuracy is needed.

The not so humble comparator plays a vital role - without it, most precision zero crossing

detectors would not work, and we'd be without digital audio, PWM and a multitude of

other applications taken for granted.

3.53.5 BASIC LOW FREQUENCY CIRCUITBASIC LOW FREQUENCY CIRCUIT

Figure below shows the zero crossing detector as used for the dimmer ramp

generator in Project 62. This circuit has been around (almost) forever, and it does work

reasonably well. Although it has almost zero phase inaccuracy, that is largely because

the pulse is so broad that any inaccuracy is completely swamped. The comparator

function is handled by transistor Q1 - very basic, but adequate for the job.

Basic 50/60Hz Zero Crossing Detector


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The circuit is also sensitive to level, and for acceptable performance the AC

waveform needs to be of reasonably high amplitude. 12-15V AC is typical. If the voltage

is too low, the pulse width will increase. The arrangement shown actually gives better

performance than the version shown in Project 62 and elsewhere on the Net. In case you

were wondering, R1 is there to ensure that the voltage falls to zero - stray capacitance is

sufficient to stop the circuit from working without it. The pulse width of this circuit (at

50Hz) is typically around 600us (0.6ms) which sounds fast enough. The problem is that

at 50Hz each half cycle takes only 10ms (8.33ms at 60Hz), so the pulse width is over 5%

of the total period. This is why most dimmers can only claim a range of 10%-90% - the

zero crossing pulse lasts too long to allow more range. While this is not a problem with

the average dimmer, it is not acceptable for precision applications. For a tone burst

generator (either the cosine burst or a 'conventional' tone burst generator), any

inaccuracy will cause the switched waveform to contain glitches. The seriousness of this

depends on the application. Precision zero crossing detectors come in a fairly wide range

of topologies, some interesting, others not. One of the most common is shown in Project

58, and is commonly used for this application. The exclusive OR (or XOR) gate makes

an excellent edge detector, as shown

Exclusive OR Gate Edge Detector


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There is no doubt that the circuit shown above is more than capable of excellent

results up to quite respectable frequencies. The upper frequency is limited only by the

speed of the device used, and with a 74HC86 it has a propagation delay of only 11ns [1],

so operation at 100 kHz or above is achievable.

The XOR gate is a special case in logic. It will output a 1 only when the inputs are

different (i.e. one input must be at logic high (1) and the other at logic low (0v). The

resistor and cap form a delay so that when an edge is presented (either rising or falling),

the delayed input holds its previous value for a short time. In the example shown, the

pulse width is 50ns. The signal is delayed by the propagation time of the device itself

(around 11ns), so a small phase error has been introduced. The rise and fall time of the

squarewave signal applied was 50ns, and this adds some more phase shift.

There is a pattern emerging in this article - the biggest limitation is speed, even for

relatively slow signals. While digital logic can operate at very high speeds, we have well

reached the point where the signals can no longer be referred to as '1' and '0' - digital

signals are back into the analogue domain, specifically RF technology.

The next challenge we face is converting the input waveform (we will assume a

sinewave) into sharply defined edges so the XOR can work its magic. Another terribly

under-rated building block is the comparator. While opamps can be used for low speed

operation (and depending on the application), extreme speed is needed for accurate

digitisation of an analogue signal. It may not appear so at first glance, but a zero crossing

detector is a special purpose analogue to digital converter (ADC).


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3.5.13.5.1 CCOMPARATORSOMPARATORS

The comparator used for a high speed zero crossing detector, a PWM converter or

conventional ADC is critical. Low propagation delay and extremely fast operation are

not only desirable, they are essential. Comparators may be the most underrated and

under utilised monolithic linear component. This is unfortunate because comparators are

one of the most flexible and universally applicable components available. In large

measure the lack of recognition is due to the IC Opamp, whose versatility allows it to

dominate the analog design world. Comparators are frequently perceived as devices that

crudely express analog signals in digital form - a 1-bit A/D converter. Strictly speaking,

this viewpoint is correct. It is also wastefully constrictive in its outlook. Comparators

don't “just compare” in the same way that opamps don't "just amplify". The above quote

was so perfect that I just had to include it. Comparators are indeed underrated as a

building block, and they have two chief requirements ... low input offset and speed. For

the application at hand (a zero crossing detector), both of these factors will determine the

final accuracy of the circuit. The XOR has been demonstrated to give a precise and

repeatable pulse, but its accuracy depends upon the exact time it 'sees' the transition of

the AC waveform across zero. This task belongs to the comparator.

Comparator Zero Crossing Detector


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In Figure of previoua page we see a typical comparator used for this application.

The output is a square wave, which is then sent to a circuit such as that in Figure 2. This

will create a single pulse for each square wave transition, and this equates to the zero

crossings of the input signal. It is assumed for this application that the input waveform is

referenced to zero volts, so swings equally above and below zero.

Comparator Timing Error

Figure above shows how the comparator can mess with our signal, causing the

transition to be displaced in time, thereby causing an error. The significance of the error

depends entirely on our expectations - there is no point trying to get an error of less than

10ns for a dimmer, for example.

The LM339 comparator that was used for the simulation is a very basic type

indeed, and with a quoted response time of 300ns it is much too slow to be usable in this

application. This is made a great deal worse by the propagation delay, which (as

simulated) is 1.5us. In general, the lower the power dissipation of a comparator, the

slower it will be, although modern IC techniques have overcome this to some extent.


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You can see that the zero crossing of the sine wave (shown in green) occurs well

before the output (red) transition - the cursor positions are set for the exact zero crossing

of each signal. The output transition starts as the input passes through zero, but because

of device delays, the output transition is almost 5us later. Most of this delay is caused by

the rather leisurely pace at which the output changes - in this case, about 5us for the total

7V peak to peak swing. That gives us a slew rate of 1.4V/us which is useless for

anything above 100Hz or so.

One of the critical factors with the comparator is its supply voltage. Ideally, this

should be as low as possible, typically with no more than ±5V. The higher the supply

voltage, the further the output voltage has to swing to get from maximum negative to

maximum positive and vice versa. While a slew rate of 100V/us may seem high, that is

much too slow for an accurate ADC, pulse width modulator or zero crossing detector.

At 100V/us and a total supply voltage of 10V (±5V), it will take 0.1us (100ns) for

the output to swing from one extreme to the other. To get that into the realm of what we

need, the slew rate would need to be 1kV/us, giving a 10ns transition time. Working

from Figure 3, you can see that even then there is an additional timing error of 5ns - not

large, and in reality probably as good as we can expect.

The problem is that the output doesn't even start to change until the input voltage

passes through the reference point (usually ground). If there is any delay caused by slew

rate limiting, by the time the output voltage passes through zero volts, it is already many

nanoseconds late. Extremely high slew rates are possible, and Reference 2 has details of

a comparator that is faster than a TTL inverter! Very careful board layout and attention

to bypassing is essential at such speeds, or the performance will be worse than woeful.


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3.63.6 120 KHZ CARRIER DETECTOR120 KHZ CARRIER DETECTOR

To receive X-10 signals, it is necessary to detect the presence of the 120 kHz

signal on the AC power line. This is accomplished with a decoupling capacitor, a high-

pass filter, a tuned amplifier, and an envelope detector. Because the impedance of a

capacitor is: Zc = 1/(2*π*f*C), a 0.1 μF capacitor presents a low impedance (13Ω) to the

120 kHz carrier frequency, but a high impedance (26.5 kΩ) to the 60 Hz power line

frequency. This high-pass filter allows the 120 kHz signal to be safely coupled to the 60

Hz power line, and it doubles as the coupling stage of the 120 kHz carrier generator

described in the next section. Since the 120 kHz carrier frequency is much higher than

the 60 Hz power line frequency, it is straightforward to design an RC filter that will pass

the 120 kHz signal and completely attenuate the 60 Hz. For a simple high-pass filter, the

-3 db breakpoint is: ƒ3 db = 1/(2*π*R*C). For C = 150 pF and R = 33 kΩ, ƒ3 db =

1/(2*π*150 pF *33 kΩ) = 32 kHz. This ƒ3 db point assures that the 60 Hz signal is

completely attenuated, while the 120 kHz signal is passed through to the amplifier

stages. Next, the 120 kHz signal is amplified using a series of inverters configured as

high gain amplifiers. The first two stages are tuned amplifiers with peak response at 120

kHz. The next two stages provide additional amplification. The amplified 120 kHz signal

is passed through an envelope detector, formed with a diode, capacitor, and resistor. The

envelope detector output is buffered through an inverter and presented to an input pin

(RC3) of the PIC16F877A. Upon each zero-crossing interrupt, RC3 is simply checked

within the 1 ms transmission envelope to see whether or not the carrier is present.


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3.73.7 120 KHZ CARRIER GENERATOR120 KHZ CARRIER GENERATOR

X10 uses 120 kHz modulation to transmit information over 60 Hz power lines. It

is possible to generate the 120 kHz carrier with an external oscillator circuit. A single

I/O pin would be used to enable or disable the oscillator circuit output. However, an

external oscillator circuit can be avoided by using one of the PIC MCU’s CCP modules.

The CCP1 module is used in PWM mode to produce a 120 kHz square-wave with

a duty cycle of 50%. Because X-10 specifies the carrier frequency at 120 kHz (+/- 2

kHz), the system oscillator is chosen to be 7.680 MHz, in order for the CCP to generate

precisely 120 kHz. Calculations for setting the PWM period and duty cycle are shown in

the code listing comments for the function InitPWM. After initialization, CCP1 is

continuously enabled, and the TRISC bit for the pin is used to gate the PWM output.

When the TRISC bit is set, the pin is an input and the 120 kHz signal is not

presented to the pin. When the TRISC bit is clear, the pin becomes an output and the 120

kHz signal is coupled to the AC power line through a transistor amplifier and capacitor.

Since the impedance of a capacitor is Zc = 1/(2*π*f*C), a 0.1 ΜF capacitor presents a

low impedance to the 120 kHz carrier frequency, but a high impedance to the 60 Hz

power line frequency. This high-pass filter allows the 120 kHz signal to be safely


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coupled to the 60 Hz power line, and it doubles as the first stage of the 120 kHz carrier

detector, described in the previous section.

To be compatible with other X-10 receivers, the maximum delay from the zero-

crossing to the beginning of the X-10 envelope should be about 300 Μs. Since the zero-

crossing detector has a maximum delay of approximately 64 μs, the firmware must take

less than 236 μs after detection of the zero-crossing to begin transmission of the 120 kHz

envelope.


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3.83.8 TRANSFORMER-LESS POWER SUPPLYTRANSFORMER-LESS POWER SUPPLY

The PIC16F877A and other board circuits require a 5V supply. In this application,

the X-10 controller must also transmit and receive its data over the AC line. Since X-10

components are intended to be plugged into a wall outlet and have a small form factor, a

transformer-less power supply is used. Two characteristics of transformer-less supplies

that should be kept in mind are limited current capacity, and lack of isolation from the

AC mains.

To protect the circuit from spikes on the AC power line, a 130V VDR (voltage

dependent resistor) is connected between Line and Neutral. The 47Ω resistor limits

current into the circuit, and the 1 MΩ resistor provides a discharge path for the voltage

left on the capacitor when the circuit is unplugged from the wall. Two diodes rectify the

voltage across the 1000 ΜF capacitor and 5.1V Zener diode to produce a 5V supply. The

reader may wish to refer to the application note AN954, “Transformer-less Power.


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3.93.9 LOAD SWITCHLOAD SWITCH

A load switch is included on the home controller so that it may act as a lamp

module, with its own house and unit address. A TRIAC was selected as the load switch,

because its medium power switching capacity and rapid switching capability make it

well-suited for lamp control and dimming. A TRIAC is an inexpensive, three-terminal

device that basically acts as a high-speed, bidirectional AC switch. Two terminals, MT1

and MT2, are wired in series with the load. A small trigger current between the gate and

MT1 allow conduction to occur between MT1 and MT2. Current continues to flow after

the gate current is removed, as long as the load current exceeds the latching value.

Because of this, the TRIAC will automatically switch off near each zero-crossing as the

AC voltage falls below the latching voltage.

A Teccor® L4008L6 Triac was selected because it has a sensitive gate that can be

directly controlled from the logic level output of the PIC MCU I/O pin. The sensitive

gate Triac can control AC current in both directions through the device, even though the

PIC MCU can provide only positive voltages to the gate. A variable dimmer is created

by including a delay between the time of each zero-crossing and the time that the trigger

current is provided to the Triac from the PIC MCU. The design and control of a lamp

dimmer using a PIC MCU is discussed in detail in PICREF-4 Reference Design,

“PICDIM Lamp Dimmer for the PIC12C508”.


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3.103.10 LCD MODULELCD MODULE

The 2-line x 16-character display uses the

HD44780U Display Controller. Eight data lines

and three control lines are used to interface to

the PIC MCU. If fewer I/O pins are available,

the LCD can be operated in Nibble mode using

only four data lines, with some additional software overhead. A basic LCD library is

included in this application, which provides the necessary functions for controlling this

type of LCD.

3.113.11 REAL-TIME CLOCKREAL-TIME CLOCK

A real-time clock is implemented using Timer1. The real-time clock keeps track of

the present time using a routine called UpdateClock. It also determines the rate that the

buttons are read by a routine called ScanKeys. Timer1 is set to cause an interrupt each

time it overflows. By adding a specific offset to Timer1 each time it overflows, the time

before the next overflow can be precisely controlled. The button reading routine,

ScanKeys, is called each time a Timer1 interrupt occurs. Since ScanKeys performs

debouncing of the button presses, a suitable rate to check the buttons is once every 25

ms. With a 32 kHz crystal, the counter increments once every 31.25 Μs when the

prescaler is set to 1:1. In order for Timer1 to generate an interrupt once every 25 ms,

TMR1H:TMR1L are pre-loaded with 0xFCE0h. The Timer1 interrupt interval, or tick,

can be seen in the following equation: (FFFFh – FCE0h)*1/32 kHz = .025 s = 1 tick.

Each time ScanKeys is called (every 25 ms), it calls UpdateClock. UpdateClock keeps

track of the time unit variables: ticks, seconds, minutes, and hours. Since every 25 ms


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equals one tick, seconds are incremented every 40 ticks. Minutes and hours are

incremented in a similar fashion.

3.123.12 PUSH BUTTONSPUSH BUTTONS

Five push buttons, connected to RB1-RB5, are used for user interaction with the

application. Each normally open push button will pull a port pin low when it is pressed.

3.133.13 LIGHT SENSORLIGHT SENSOR

To detect the ambient light level, a CdS photoresistor is

used in conjunction with an 820Ω resistor to create a voltage

divider. The voltage on the divider varies with the intensity of

ambient light and is connected to an analog channel (AN0) of

the microcontroller.

3.143.14 IN-CIRCUIT DEBUGGER IN-CIRCUIT DEBUGGER

RB6 and RB7 have been reserved for In-Circuit Serial ProgrammingTM

(ICSPTM) and the In-Circuit Debugger (ICD). However, do not connect the ICD or any

other development tool, without taking first isolating the entire application from wall

power.


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3.153.15 CONTROL DATA STORAGECONTROL DATA STORAGE

Certain control data that is programmable by the user must be stored in non-

volatile memory. The PIC MCU’s built-in EEPROM is well-suited to this task. To use

EEPROM memory space most

efficiently (by avoiding wasted bits),

on/off times and light sensor control

flags are stored using the format shown

in Figure 8. Figure 9 shows the location of on/off times and other information within the

data EEPROM. Using this data organization, only

48 bytes of EEPROM are required to store the

on/off times and light sensor control flags for 16

units.

Each time that minutes are incremented

within the UpdateClock routine, a flag is set that

enables a routine called CheckOnOffTimes to be

called from the main loop. CheckOnOff Times

compares the present time with the unit on and off

times stored in EEPROM memory. If there is a

match, then a flag is set to either turn the unit on or

off, by sending it the appropriate X-10 command

when the routine ControlX10Units is called.


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3.163.16 ENVELOPE DETECTORENVELOPE DETECTOR

An envelope detector is an electronic circuit that takes a high-frequency signal as

input and provides an output which is the "envelope" of the original signal. The capacitor

in the circuit stores up charge on the rising edge, and releases it slowly through the

resistor when the signal falls. The diode in series rectifies the incoming signal, allowing

current flow only when the positive input terminal is at a higher potential than the

negative input terminal.

A signal and its envelope marked with red

A simple envelope demodulator circuit.


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A signal in blue and the magnitude of its analytic signal in red, showing the envelope effect

Most practical envelope detectors use either half-wave or full-wave rectification of

the signal to convert the AC audio input into a pulsed DC signal. Filtering is then used to

smooth the final result. This filtering is rarely perfect and some "ripple" is likely to

remain on the envelope follower output, particularly for low frequency inputs such as

notes from a bass guitar. More filtering gives a smoother result, but decreases the

responsiveness; thus, real-world designs must be optimized for the application.

3.16.13.16.1 DDEFINITIONEFINITION OFOF THETHE ENVELOPEENVELOPE

Any AM or FM signal can be written in the following form


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In the case of AM, φ(t), the phase component of the signal, is constant and can be

ignored, so all the information in the signal is in R(t). R(t) is called theenvelope of the

signal. Hence an AM signal is given by the equation

with m(t) representing the original audio frequency message, C the carrier amplitude

and R(t) equal to C + m(t). So, if the envelope of the AM signal can be extracted, the

original message can be recovered.

3.16.23.16.2 DDIODEIODE DETECTORDETECTOR

The simplest form of envelope detector is the diode detector which is shown

above. A diode detector is simply a diode between the input and output of a circuit,

connected to a resistor and capacitor in parallel from the output of the circuit to the

ground. If the resistor and capacitor are correctly chosen, the output of this circuit should

approximate a voltage-shifted version of the original (baseband) signal. A simple filter

can then be applied to filter out the DC component.

3.16.33.16.3 PPRECISIONRECISION DETECTORDETECTOR

An envelope detector can also be constructed to use a precision rectifier feeding

into a low-pass filter.

3.16.43.16.4 DDRAWBACKSRAWBACKS

The envelope detector has several drawbacks:

The input to the detector must be band-pass filtered around the desired signal, or else the

detector will simultaneously demodulate several signals. The filtering can be done with a

tunable filter or, more practically, a superheterodyne receiver

It is more susceptible to noise than a product detector


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If the signal is over modulated, distortion will occur

Most of these drawbacks are relatively minor and are usually acceptable tradeoffs

for the simplicity and low cost of using an envelope detector.

3.16.53.16.5 DDEMODULATIONEMODULATION OFOF SIGNALSSIGNALS

An envelope detector can be used to demodulate a previously modulated signal by

removing all high frequency components of the signal. The capacitor and resistor form a

low-pass filter to filter out the carrier frequency. Such a device is often used to

demodulate AM radio signals because the envelope of the modulated signal is equivalent

to the baseband signal.

3.16.63.16.6 AAUDIOUDIO

An envelope detector is sometimes referred to as an envelope

follower in musical environments. It is still used to detect the amplitude variations of an

incoming signal to produce a control signal that resembles those variations. However, in

this case the input signal is made up of audible frequencies.

Envelope detectors are often a component of other circuits, such as

a compressor or an auto-wah or envelope-followed filter. In these circuits, the envelope

follower is part of what is known as the "side chain", a circuit which describes some

characteristic of the input, in this case its volume.

Both expanders and compressors use the envelope's output voltage to control of

the gain of an amplifier. Auto-wah uses the voltage to control the cutoff frequency of a

filter. The voltage-controlled filter of an analog synthesizer is a similar circuit.


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3.173.17 SCOPE ADAPTER CIRCUITSCOPE ADAPTER CIRCUIT

An AC adapter which reduces the amount of power drawn

from an AC power source when a system is disconnected from

the adapter, includes: a rectifier bridge for rectifying an AC

voltage from an AC power supply; a conversion circuit coupled

to the rectifier bridge for converting the rectified AC voltage to a

DC voltage; and an opto-coupler coupled to the conversion

circuit for monitoring an output connection of the circuit,

wherein when a system is not coupled to the output connection,

the opto-coupler substantially prevents the AC voltage from being drawn from the AC

power supply. The adapter circuit uses an opto-coupler comprising a diode and a

transistor to reduce the amount of current drawn from an AC power supply when a

system is not connected to the AC adapter. In this manner, the AC adapter is prevented

from becoming heated when no system is connected.


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3.183.18 HIGH-PASS FILTERHIGH-PASS FILTER

A high-pass filter, or HPF, is an LTI filter that passes high frequencies well

but attenuates (i.e., reduces the amplitude of) frequencies lower than the filter's cutoff

frequency. The actual amount of attenuation for each frequency is a design parameter of

the filter. It is sometimes called a low-cut filter or bass-cut filter.


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3.18.13.18.1 FFIRSTIRST--ORDERORDER CONTINUOUSCONTINUOUS--TIMETIME IMPLEMENTATIONIMPLEMENTATION

A passive, analog, first-order high-pass filter, realized by an RC circuit

The simple first-order electronic high-pass filter shown in Figure 1 is implemented

by placing an input voltage across the series combination of a capacitor and

a resistor and using the voltage across the resistor as an output. The product of the

resistance and capacitance (R×C) is the time constant (τ); it is inversely proportional to

the cutoff frequency fc, at which the output power is half the input power. That is,

where fc is in hertz, τ is in seconds, R is in ohms, and C is in farads.

An active high-pass filter

Figure shows an active electronic implementation of a first-order high-pass filter

using an operational amplifier. In this case, the filter has a pass band gain of -R2/R1 and

has a corner frequency of


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Because this filter is active, it may have non-unity passband gain. That is, high-

frequency signals are inverted and amplified by R2/R1.

3.18.23.18.2 DDISCRETEISCRETE--TIMETIME REALIZATIONREALIZATION

For another method of conversion from continuous- to discrete-time, see Bilinear

transform.

Discrete-time high-pass filters can also be designed. Discrete-time filter design is

beyond the scope of this article; however, a simple example comes from the conversion

of the continuous-time high-pass filter above to a discrete-time realization. That is, the

continuous-time behavior can be discretized.

From the circuit in Figure 1 above, according to Kirchoff's Laws and the definition

of capacitance:

where Qc(t) is the charge stored in the capacitor at time t. Substituting Equation (Q) into

Equation (I) and then Equation (I) into Equation (V) gives:

This equation can be discretized. For simplicity, assume that samples of the input

and output are taken at evenly-spaced points in time separated by ΔT time. Let the

samples of Vin be represented by the sequence , and let Vout be


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represented by the sequence which correspond to the same points in

time. Making these substitutions:

And rearranging terms gives the recurrence relation

That is, this discrete-time implementation of a simple continuous-time RC high-

pass filter is

By definition, . The expression for parameter α yields the

equivalent time constant RC in terms of the sampling period ΔT and α:

If α = 0.5, then the RC time constant equal to the sampling period. If ,

then RC is significantly smaller than the sampling interval, and


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4. ALL CIRCUIT DIAGRAM AT A SCOPE


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5. SOFTWARE

5.15.1 APPLICATION FIRMWARE OVERVIEWAPPLICATION FIRMWARE OVERVIEW

he firmware is divided into several different files to facilitate adaptation of the

code to other applications.TFollowing is a summary of the files associated with this application note:

x10lib.asm Defines X-10 functions.

x10lib.inc Defines X-10 constants and macros.

x10hc.asm Main application code for the home controller.

x10demo.asm Example code that shows how to use the X-10 library macros.

lcd.asm Defines the routines necessary for driving the LCD.

p16f877A.lkr Standard linker file for PIC16F877A parts.

p16f877A.inc Standard include file for PIC16F877A parts.

Detailed descriptions of operation can be found in the comments within the code

listing.

5.25.2 X-10 LIBRARYX-10 LIBRARY

A simple library of commands was developed and used for the home controller. It

can be used with little or no modification in a user’s application. The library consists of

two files: x10lib.asm and x10lib.inc.

To use the library, a user need only understand the function of the macros defined

in x10lib.inc. The macros greatly simplify the use of the library by eliminating the need

for the user to understand every X-10 function in x10lib.asm. Examples of how the

macros are used are included in the file x10demo.asm.


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The macros are explained below:

InitX10

This macro is used to initialize the peripherals that provide X-10 functionality. It

must be called in the application program before any of the below macros will work. It is

used as follows:

InitX10

5.2.15.2.1 SSKIPKIPIIFFTTXXRREADYEADY

Before sending an X-10 message, it is necessary tomake sure that another message

is not already being sent, which is signified by the X10TxFlag being set. This macro

simply checks that flag and skips the next instruction if it is okay to begin a new

transmission. Otherwise, there is a chance that a new transmission will interrupt an

ongoing transmission. It is used as follows:

SkipIfTxDone

GOTO $-1 ;loop until ready to

;transmit next message

5.2.25.2.2 SSENDENDX10AX10ADDRESSDDRESS (H (HOUSEOUSE, U, UNITNIT))

This macro is used to send an X-10 address for a particular unit. It requires two

arguments, a house address and unit address. The definitions for all house and unit

addresses are defined in x10lib.inc. To use this macro to send the address for unit 16 at

house P, one simply types:

SendX10Address HouseP, Unit16


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5.2.35.2.3 SSENDENDX10AX10ADDRESSDDRESSVVARAR

This macro is used to send an X-10 address, defined by variables rather than

constants. To send an address contained in the user variables MyHouse and MyUnit, the

following sequence would be applied:

MOVF MyHouse, W ;contains a value

;from 0-16

MOVWF TxHouse

MOVF MyUnit, W ;contains a value

;from 0-16

MOVWF TxUnit

SendX10AddressVar

5.2.45.2.4 SSENDENDX10CX10COMMANDOMMAND (H (HOUSEOUSE, F, FUNCTIONUNCTION))

This macro is used to send an X-10 command. It requires two arguments, the

house address and function code. The definitions for all house addresses and function

codes are defined in x10lib.inc. To use this macro to send the command ‘All Lights On’

to all units at house A, one types:

SendX10Command HouseA, AllLightsOn


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5.2.55.2.5 SSENDENDX10CX10COMMANDOMMANDVVARAR

This macro is used to send an X-10 command, defined by a variable rather than a

constant. To use this macro to send the command stored in the user variable

MyCommand to all units at MyHouse, one types:

MOVF MyHouse, W ;contains a value

;from 0-16

MOVWF TxHouse

MOVF MyCommand, W ;any X-10

;function

;defined in

;x10lib.inc

MOVWF TxFunction

SendX10CommandVar

5.2.65.2.6 SSKIPKIPIIFFRRXXDDONEONE

Before reading an X-10 message, it is necessary to make sure that a complete

message has been received. This is signified by the X10RxFlag being set. This macro

simply checks that flag and skips the next instruction if a new X-10 message has been

received. It is used as follows:

SkipIfRxDone

GOTO $-1 ;loop until message

;received


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5.2.75.2.7 SSKIPKIPIIFFAADDRESSDDRESSRRCVDCVD

It may be necessary to make sure that an address was received by using this

macro, which checks to see if the RxCommandFlag is clear. It is used as follows:

SkipIfAddressRcvd

GOTO $-1 ;loop until address

;received

5.2.85.2.8 SSKIPKIPIIFFCCOMMANDOMMANDRRCVDCVD

Or, it may be necessary to make sure that a command was received by using this

macro, which checks to see if the RxCommandFlag is set. It is used as follows:

SkipIfCommandRcvd

GOTO $-1 ;loop until command

;received

5.2.95.2.9 RREADEADX10MX10MESSAGEESSAGE

This macro is called to read a received X-10 message, which may be either an

address or a command. If the message was an address, then the received house and unit

codes will be stored in the variables RxHouse and RxUnit, respectively. If the message

was a command, then the received house address and function code will be stored in the

variables RxHouse and RxFunction. It is simply called as follows:

ReadX10Message


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5.35.3 INTRODUCTION TO KEIL SOFTWAREINTRODUCTION TO KEIL SOFTWARE

Keil Micro Vision is an integrated development environment used to create

software to be run on embedded systems (like a microcontroller). It allows for such

software to be written either in assembly or C programming languages and for that

software to be simulated on a computer before being loaded onto the microcontroller.

5.45.4 WHAT IS ΜVISION3?WHAT IS ΜVISION3?

µVision3 is an IDE (Integrated Development Environment) that helps write,

compile, and debug embedded programs. It encapsulates the following components:

A project manager.

A make facility.

Tool configuration.

Editor.

A powerful debugger.

5.55.5 STEPS FOLLOWED IN CREATING AN APPLICATION INSTEPS FOLLOWED IN CREATING AN APPLICATION IN ΜVISION3:ΜVISION3:

To create a new project in uVision3:

Select Project - New Project.

Select a directory and enter the name of the project file.

Select Project –Select Device and select a device from Device Database.

Create source files to add to the project

Select Project - Targets, Groups, and Files. Add/Files, select Source Group1, and

add the source files to the project.


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Select Project - Options and set the tool options. Note that when the target device

is selected from the Device Database™ all-special options are set automatically.

Default memory model settings are optimal for most applications.

Select Project - Rebuild all target files or Build target

To create a new project, simply start Micro Vision and select

“Project”=>”New Project” from the pull–down menus. In the file dialog that appears,

choose a name and base directory for the project. It is recommended that a new

directory be created for each project, as several files will be generated. Once the project

has been named, the dialog shown in the figure below will appear, prompting the user

to select a target device. In this lab, the chip being used is the “AT89S52,” which is

listed under the heading “Atmel

Window for choosing the Target Device

Next, Micro Vision must be instructed to generate a HEX file upon program

compilation. A HEX file is a standard file format for storing executable code that is to

be loaded onto the microcontroller. In the “Project Workspace” pane at the left, right–

click on “Target 1” and select “Options for ‘Target 1’ ”.Under the “Output” tab of the


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resulting options dialog, ensure that both the “Create Executable” and “Create HEX

File” options are checked. Then click “OK” as shown in the two figures below.

Project Workspace Pane Project Options Dialog

Next, a file must be added to the project that will contain the project code. To do

this, expand the “Target 1” heading, right–click on the “Source Group 1” folder, and

select “Add files…” Create a new blank file (the file name should end in “.asm”), select

it, and click “Add.” The new file should now appear in the “Project Workspace” pane

under the “Source Group 1” folder. Double-click on the newly created file to open it in

the editor. All code for this lab will go in this file. To compile the program, first save

all source files by clicking on the “Save All” button, and then click on the “Rebuild All

Target Files” to compile the program as shown in the figure below. If any errors or

warnings occur during compilation, they will be displayed in the output window at the

bottom of the screen. All errors and warnings will reference the line and column

number in which they occur along with a description of the problem so that they

can be easily located. Note that only errors indicate that the compilation failed,

warnings do not (though it is generally a good idea to look into them anyway).


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“Save All” and “Build All Target Files” Buttons

When the program has been successfully compiled, it can be simulated using the

integrated debugger in Keil Micro Vision. To start the debugger, select

“Debug”=>”Start/Stop Debug Session” from the pull–down menus.

At the left side of the debugger window, a table is displayed containing several

key parameters about the simulated microcontroller, most notably the elapsed time

(circled in the figure below). Just above that, there are several buttons that control code

execution. The “Run” button will cause the program to run continuously until a

breakpoint is reached, whereas the “Step Into” button will execute the next line of code

and then pause (the current position in the program is indicated by a yellow arrow to

the left of the code).


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µVision3 Debugger window

Breakpoints can be set by double–clicking on the grey bar on the left edge of the

window containing the program code. A breakpoint is indicated by a red box next to the

line of code.


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‘Reset’, ‘Run’ and ‘Step into’ options

The current state of the pins on each I/O port on the simulated microcontroller

can also be displayed. To view the state of a port, select “Peripherals”=>”I/O

Ports”=>”Port n” from the pull–down menus, where n is the port number. A checked

box in the port window indicates a high (1) pin, and an empty box indicates a low (0)

pin. Both the I/O port data and the data at the left side of the screen are updated

whenever the program is paused.

The debugger will help eliminate many programming errors, however the

simulation is not perfect and code that executes properly in simulation may not always

work on the actual microcontroller.


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5.65.6 DEVICE DATABASEDEVICE DATABASE

A unique feature of the Keil µVision3 IDE is the Device Database, which

contains information about more than 400 supported microcontrollers. When you

create a new µVision3 project and select the target chip from the database, µVision3

sets all assembler, compiler, linker, and debugger options for you. The only option you

must configure is the memory map.

5.75.7 PERIPHERAL SIMULATIONPERIPHERAL SIMULATION

The µVision3 Debugger provides complete simulation for the CPU and on-chip

peripherals of most embedded devices. To discover which peripherals of a device are

supported, in µVision3 select the Simulated Peripherals item from the Help menu. You

may also use the web-based Device Database. We are constantly adding new devices

and simulation support for on-chip peripherals so be sure to check Device Database

often.

5.85.8 PROGRAMMERPROGRAMMER

The programmer used is a powerful programmer for the Atmel 89 series of

microcontrollers that includes 89C51/52/55, 89S51/52/55 and many more.

It is simple to use & low cost, yet powerful flash microcontroller programmer for the

Atmel 89 series. It will Program, Read and Verify Code Data, Write Lock Bits, Erase

and Blank Check. All fuse and lock bits are programmable. This programmer has

intelligent onboard firmware and connects to the serial port. It can be used with any

type of computer and requires no special hardware. All that is needed is a serial

communication port which all computers have.


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All devices also have a number of lock bits to provide various levels of software

and programming protection. These lock bits are fully programmable using this

programmer. Lock bits are useful to protect the program to be read back from

microcontroller only allowing erase to reprogram the microcontroller.

Major parts of this programmer are Serial Port, Power Supply and Firmware

microcontroller. Serial data is sent and received from 9 pin connector and converted

to/from TTL logic/RS232 signal levels by MAX232 chip. A Male to Female serial

port cable, connects to the 9 pin connector of hardware and another side connects to

back of computer.

All the programming ‘intelligence’ is built into the programmer so you do not

need any special hardware to run it. Programmer comes with window based software

for easy programming of the devices.

5.95.9 PROLOAD PROGRAMMING SOFTWAREPROLOAD PROGRAMMING SOFTWARE

‘Proload’ is a software working as a user friendly interface for programmer

boards from Sunrom Technologies. Proload gets its name from “Program Loader” term,

because that is what it is supposed to do. It takes in compiled HEX file and loads it to

the hardware. Any compiler can be used with it, Assembly or C, as all of them generate

compiled HEX files. Proload accepts the Intel HEX format file generated from

compiler to be sent to target microcontroller. It auto detects the hardware connected to

the serial port. It also auto detects the chip inserted and bytes used. The software is

developed in Delphi and requires no overhead of any external DLL.


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The programmer connects to the computer’s serial port (Comm 1, 2, 3 or 4) with

a standard DB9 Male to DB9 Female cable. Baud Rate - 57600, COMx Automatically

selected by window software. No PC Card Required. After making the necessary

selections, the ‘Auto Program’ button is clicked as shown in the figure below which

burns the selected hex file onto the microcontroller.

Programming window


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6. HOME CONTROLLER OPERATING

INSTRUCTIONS

6.16.1 “WELCOME SCREEN”“WELCOME SCREEN”

The home controller user interface consists of five buttons and a 2 x 16 LCD.

Upon power-up, the Welcome screen is displayed. This screen displays a welcome

message and the time. Immediately, the seconds begin incrementing and the PIC MCU

begins keeping track of the time. Figure below shows the Welcome screen and the

location and functionality of each button. Depending on the screen viewed, each of the

five buttons performs a different function. When the Welcome screen is displayed, the

buttons enable access to the following functions:

Press menu to enter the Select Function screen.Press up to brighten the lamp that is plugged into the home controller.Press down to dim the lamp.Press enter to turn the lamp on.Press exit to turn the lamp off.

WELCOME SCREEN


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6.1.16.1.1 SSELECTELECT F FUNCTIONUNCTION S SCREENCREEN

When viewing the Welcome screen, the menu button enables access to the Select

Function screen. Each successive press of the menu button cycles through the four main

functions of the user interface: setting the system time, setting the system address,

setting the light sensor, or programming the unit on and off times, as illustrated in

Figure below.

SELECT FUNCTION SCREENS


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6.1.26.1.2 SSETET S SYSTEMYSTEM T TIMEIME S SCREENCREEN

Use the Set System Time screen to set the time.

SETTING SYSTEM TIME

1. Starting from the Welcome screen, press menu until the Set System Time screen is

displayed and press enter.

2. Press up/down to set the hours.

3. Press enter when the correct hour, including AM or PM, has been selected.

4. Repeat this process to set the minutes.

5. If the time is correct, select Y (the default) using the up/down buttons and press

enter. This returns to the Welcome screen with the new time displayed.

6. If the time is not correct, select N and press enter. This will return the user to step 2

so the correct time can be entered.

7. Press exit at any time to return the user to the Welcome screen without saving the

new time.

SET SYSTEM TIME SCREENS


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6.1.36.1.3 SSELECTELECT S SYSTEMYSTEM A ADDRESSDDRESS S SCREENCREEN

Use the Set System Address screen to set the house address and unit address of

the home controller.

SETTING HOUSE/UNIT ADDRESS

1. From the Welcome screen, press menu until the Set System Addr screen is displayed

and press enter.

2. Press up or down to set the house address (a letter from A - P).

3. Press enter when the house address has been selected.

4. Repeat steps 2 and 3 to set the unit address (a number from 1 - 16).

5. If the house and unit addresses are correct, select Y (the default) using the up/down

buttons and press enter. This returns to the Welcome screen with the new address

stored in non-volatile memory.

6. If the address is not correct, select N and press enter. This will return the user to step

2.

7. Press exit at any time to return the user to the Welcome screen without saving the

new address.

SET SYSTEM ADDRESS SCREENS


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6.1.46.1.4 SSETET L LIGHTIGHT S SENSORENSOR S SCREENCREEN

Use the Set Light Sensor screen to select whether units turn on at dusk, or off at

dawn.

SETTING THE LIGHT SENSOR

1. From the Welcome screen, press menu until the Set Light Sensor screen is displayed

and press enter.

2. Press up or down to select the desired unit. The house address will already be set to

the system house address.

3. Press enter when the desired unit address has been selected.

4. Press up or down to select whether or not the unit should turn on at dusk, and press

enter.

5. Repeat this process to set other units as desired.

6. Press exit to return to the Welcome screen.

Pressing exit while the “On at Dusk” or “Off at Dawn” prompt is displayed will return

the user to the Welcome screen without modifying that parameter.

SET LIGHT SENSOR SCREENS


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6.1.56.1.5 PPROGRAMROGRAM U UNITNIT S SCREENCREEN

Use the Program Unit screen to program on and off

times for different units.

PROGRAMMING UNIT ON AND OFF TIMES

1. From the Welcome screen, press menu repeatedly until

the Program Unit screen is displayed and press enter.

2. Press up or down to select the desired unit. The house

address will already be set to the system house address.

3. Press enter when the unit address has been selected.

4. Press up or down to set the ‘on’ time hours. Hours set to

‘00’ means that the unit will not be turned on at any time.

5. Press enter when the correct hour, including AM or PM,

has been selected.

6. Repeat this process to set the ‘on’ time minutes. If the

hour has been set to ‘00’, then the minutes will be set to ‘00’ automatically.

7. If the time is correct, select Y (the default) using the up/down buttons and press

enter. The user will be prompted to program the ‘off’ time in a similar fashion.

8. If the time is not correct, select N and press enter. This allows the user to re-enter the

hour and minutes by returning to step 2.

9. Repeat this process to set the ‘on’ and ‘off’ time for other units as desired.

10. Press exit to return to the Welcome screen. Pressing exit while the “Set Hours” or

“Set Min” prompt is displayed will return the user to the Welcome screen without

modifying any parameters.


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7. WEAK POINTS AND LIMITATIONS

7.17.1 COMPATIBILITY WITH INSTALLED WIRING AND COMPATIBILITY WITH INSTALLED WIRING AND APPLIANCESAPPLIANCES

One problem with X10 is excessive attenuation of signals between the two live

conductors in the 3-wire 120/240 volt system used in typical North

American residential construction. Signals from a transmitter on one live conductor

may not propagate through the high impedance of the distribution transformer winding

to the other live conductor. Often, there's simply no reliable path to allow the X10

signals to propagate from one phase wire to the other; this failure may come and go as

large 240 volt devices such as stoves or dryers are turned on and off. (When turned on,

such devices provide a low-impedance bridge for the X10 signals between the two

phase wires.) This problem can be permanently overcome by installing

a capacitor between the phase wires as a path for the X10 signals; manufacturers

commonly sell signal couplers that plug into 240 volt sockets that perform this

function. More sophisticated installations install an active repeater device between the

phases, while others combine signal amplifiers with a coupling device. A repeater is

also needed for inter-phase communication in homes with three-phase electric power.

In many countries outside North America, entire houses are typically wired from a

single 240 volt single phase wire so this problem does not occur.

An RCD/GFCI can attenuate X10 signals passing through the device. This means

that X10 signals passing through an RCD may not be strong enough to provide reliable

communication.


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Other problems: TVs or wireless devices may cause spurious off or on signals.

Noise filtering (as installed on computers as well as many modern appliances) may help

keep external noise out of X10 signals, but noise filters not designed for X10 may also

filter out X10 signals traveling on the branch circuit to which the appliance is

connected.

Also, certain types of power supplies used in modern electronic equipment (such

as computers, television sets, and satellite receivers) "eat" passing X10 signals by

providing a low impedance path to high frequency signals. Typically, the capacitors

used on the inputs to these power supplies short the X10 signal from line to neutral,

suppressing any hope of X10 control on the circuit near that device. Filters are

available that will block the X10 signals from ever reaching such devices; plugging

offending devices into such filters can cure mysterious X10 intermittent failures.

Some X10 controllers may not work well or at all with low power devices (below 50

watts) or devices like fluorescent bulbs that do not present resistive loads. Use of an

appliance module rather than a lamp module may resolve this problem.

7.27.2 COMMANDS GETTING LOSTCOMMANDS GETTING LOST

X10 signals can only be transmitted one command at a time, first by addressing

the device to control, and then sending an operation for that device to perform. If two

X10 signals are transmitted at the same time they may collide or interleave, leading to

commands that either cannot be decoded or that trigger incorrect operations.


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7.37.3 RELATIVELY SLOWRELATIVELY SLOW

The X10 protocol is also slow. It takes roughly three quarters of a second to

transmit a device address and a command. While generally not noticeable when using a

tabletop controller, it becomes a noticeable problem when using 2-way switches or

when utilizing some sort of computerized controller. The apparent delay can be

lessened somewhat by using slower device dim rates. With more advanced modules

another option is to use group control (lighting scene) extended commands. These

allow to adjust several modules at once by a single command.

7.47.4 LIMITED FUNCTIONALITYLIMITED FUNCTIONALITY

X10 protocol does support more advanced control over the dimming speed,

direct dim level setting and group control (scene settings). This is done via extended

message set, which is an official part of X10 standard. However support for all

extended messages is not mandatory, and a lot of cheaper modules implement only the

basic message set. These require adjusting each lighting circuit one after the other,

which can be visually unappealing and also very slow.

7.57.5 INTERFERENCE AND LACK OF ENCRYPTIONINTERFERENCE AND LACK OF ENCRYPTION

The standard X10 power line and RF protocols lack support for encryption, and

can only address 256 devices. Unless filtered, power line signals from close neighbours

using X10 may interfere with each other if the same device addresses are used by each

party. Interfering RF wireless signals may similarly be received, with it being easy for

anyone nearby with an X10 RF remote to wittingly or unwittingly cause mayhem if an

RF to power line device is being used on a premises.

7.67.6 BRIDGESBRIDGES


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There are bridges to translate X10 to other domotic standards.

8. ADVANTAGE

It is estimated that X10 compatible products can be found in over 10 million American

homes. This is because it has so many advantages over other types of remote control

products and systems:

Inexpensive

No new wiring is required -- perfect for retrofit

Simple to install

100's of compatible products

Control up to 256 lights and appliances

Time proven


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9. CONCLUSION

The PIC MCU is well-suited to X-10 applications. With its plethora of on-chip

peripherals and a few external components, a PIC MCU can be used to implement an

X-10 system that can transmit and receive messages over the AC power line wiring.

The small code size of the X-10 library leaves ample space for the user to create

application specific code. PIC MCUs, such as the PIC16F877A, have plenty of

additional resources for creating more complex X-10 applications, while smaller PIC

MCUs can be selected for economical use in simpler X-10 applications.


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10. TROUBLE SHOOTING

In case of a system hang-up condition, the reset button in the vicinity of the Microcontroller can be used to revive the system.

Documents

X-10 Home Automation -Content