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The informationgenerated and stored by adigital householdappliance during normaloperation can becomevery useful whenacquired and processedby a remote ServiceCentre.

This can be achievedthrough the connection ofthe appliance to a home-network via a proper"communication node",based on a suitableprotocol (EHS/Konnex,LonTalk, Echonet, Z-Wave,Zig-Bee, Bluetooth,CEBus, X-10, UPB …).

Unfortunately, the costof any communicationnode available todayis absolutelyincompatible with the

well-known economic constraintsthat are peculiar to the white goodsindustry. Furthermore, a homenetwork protocol recognized as astandard by all the actors involvedwith home automation isn’t yetavailable. Therefore it is presentlyimpossible, for manufacturers ofwhite goods, to produce and sellhigh volume of products with acommunication node inside.

To solve this problem, Wrap S.p.A.

(the R&D firm created through aspin-off by Merloni Elettrodomestici,the third European producer of whitegoods) has developed abreakthrough technology able tomove the communication node(based on any protocol) from thewhite good to the electric mains(wiring system), without affectingthe capability of the appliance toexchange information in a bi-directional way with the homenetwork. As a consequence of this,white goods and any other electricalhousehold appliance becomecompletely free from communicationcost and standard protocol selectionissues. Therefore, according to this

Connecting white goodsto a home network at avery low cost

Valerio Aisa, Paolo Falcioni, Piero PracchiWrap S.p.A., Italy

Figure 1: Digital appliance fundamental requirements

inexpensive technology called"power modulation", any electricalappliance, simple or complex, couldbe connected to a home network forcontributing in optimising the in-house use of electricity and yet inhelping manufacturers to guaranteehigh level maintenance services forthe customer at a reasonable cost.

Such a new technology isdescribed in this document.

Digital HouseholdAppliances

The concept of "digital" applied towhite goods involves somethingmore than a simple use of amicrocontroller, since it includes atleast three distinctive elements: theexistence of an electronic controlsystem, the ability to generate andstore useful information, and thepossibility of exchanging thisinformation with the outside world.

The heart of the new generation ofcontrol systems for white goodsapplications is usually amicrocontroller, able to managesignals generated by sensors, tocontrol electric loads (solenoidvalves, motors, pumps, fans, waterheaters, and so on), to save usefuldata into non-volatile memories, andto exchange data outbound througha proper communication line.

The information generated by thecontrol system of a white good notonly should include the datanecessary to guarantee the correctoperation of the appliance itself, butalso data suitable for applicationsderiving from the networkconnection of said appliance.

The information required for thecorrect operation of a digitalappliance (Fig. 1) concerns thesystem status variables liketemperatures, time intervals, waterlevels, working cycle progressphases, and so on. Anotherimportant information comes from

diagnostic data, which are generatedby a specific software routine thatverifies the correct functionality foreach individual operation.

As far as it concerns theinformation required for otherpurposes, it includes for instancestatistical data (how many and whichoperating cycles were performed,how the optional functions offeredby the appliance are used, how thedetergent is used...), and data relatedto electricity and water consumption.This information can become veryuseful when acquired and processedby a remote service centre, and thiscan be achieved by connecting theappliance to a proper home networkusing a suitable "communicationnode", that is a device able tocommunicate with other devices onthe same network according to aspecific protocol (set of rules forexchanging data inside a network).

Typically a communication nodemust be able to exchange data withthe related digital appliance througha two-way serial link, and tocommunicate with the network usinga standard protocol and a propertransceiver for the physicalconnection to the transmission line.Since white goods manufacturershave already decided to use powerline as transmission media, thetransceiver included in thecommunication node is a "power linemodem". Amongst the power linebased protocols that can be used inEurope, the most important are the

following two: EHS/Konnex andLonTalk. The former is implementedinside a standard microcontrollerwith specific software routines anduses a solid-state transceiver; thelatter is included in the firmware of aNeuronChip (a specific device fornetworking purposes) and uses ahybrid DSP based transceiver. Bothof them are effective, robust andreliable, but absolutely too expensivewhen used inside a white good; theirfull cost, in fact, ranges from 30 to 40Euros (all included: PCB, connectors,power supply, box...) and can beaccepted only by very high-endproducts. Furthermore, the Europeanmanufacturers of white goods arepresently divided in two "parties":some of them prefer EHS/Konnex,others prefer LonTalk, and others aredealing with both of them. But themarket needs just a unique protocolto avoid confusion.

How to solve this problem?CECED, the European organizationof white goods manufacturers, hascreated a specific working group tosolve it and it is still investigating.Furthermore, even though CECEDwill issue soon an ApplicationInterworking Specificationdocument, it is not recommendingany specific technology.

Therefore, the only way to solvethe problem seems to be thefollowing: "eliminating thecommunication node from a whitegood, without affecting its capabilityto exchange data with a home

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Figure 2: Communication system based on "power modulation"

network using any protocol". Thisstatement could appear unrealistic,but, on the other hand, it is possibleto demonstrate that it is absolutelyrealistic when a new inexpensivecommunication technology, called"power modulation", is used.

"Power Modulation"Concept

As shown in Fig. 2, powermodulation technology comes fromthe following two concepts: digitalappliance and smart adapter. Digitalappliance concept has already been

presented (see Fig. 1); on the otherhand, the concept of smart adapter isa new one, created few years ago fornetworking traditional appliances.

Smart Adapter

The "smart adapter" (Fig. 3) is adevice for connecting to a networkany electrical appliance, which isn’tcapable of communicating .

The smart adapter embeds acommunication node and a powermeter, and it is located between anelectrical appliance and its outlet.Thanks to the communication node,

the smart adapter communicateswith the home bus; with the powermeter it analyses the electric currentabsorbed by the appliance andgenerates useful information(functional, statistical, diagnostic,and power/energy consumptiondata) related to the appliance itself.

How a smart adapter cancommunicate with a digitalappliance

When the electrical appliance is adigital one, the "smart adapter" cancommunicate directly with it usingits internal power meter to measurethe electric current absorbed by theappliance during each cycle of thesupply voltage. According to thisconcept, the digital appliance is ableto send at least one bit per cycle (i.e.:50 or 60 bits per second, dependingon the value of the power linefrequency) in a very robust andreliable way by just absorbing asmall electric current (10 mA, forinstance) using a small triac drivingan inexpensive resistive load.Furthermore, the smart adapter cansend commands to the digitalappliance by just generating shortand precise interruptions of thewhite good’s power supply; thedigital control system of theappliance can then decode easilysuch commands by just measuringthe variation of the time intervalbetween two consecutive zero-crossing transitions of the linevoltage. It is easy to demonstrate thepossibility to send at least one nibble(four bits) at a time, without affectingthe proper functionality of theappliance.

According to Fig. 4, a smartadapter can be connected, forinstance, to a network through acommunication node based onLonTalk protocol and a PLT-22power line transceiver, produced byEchelon Corporation (San Jose, CA);furthermore, it uses a power meter toreceive bits (one bit at a time) fromthe appliance by measuring itsinstantaneous power consumption

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Figure 3: Concept of Smart Adapter

Figure 4: Functional diagram of the Smart Adapter

during each cycle of the mains, andto send bits (four bit at a time) to theappliance through small and precisevoltage interruptions generated bythe triac.

Fig. 5 shows how the appliance cansend a logical "one" or "zero" by justabsorbing/not absorbing powerduring each cycle of the supplyvoltage. The appliancemicrocontroller (MC2) manages theelectric current flow through a lowpower (10 W, for instance) resistiveload by sending pulses to the gate ofthe triac as soon as a voltage zerocrossing is detected. The powermeter measures continuously the

power absorbed by the applianceduring each period of the mains, and,if the measured value is below adetermined low threshold (5 W, forinstance), it is recognized as a logical"zero"; otherwise, when this value isgreater than a given high threshold(7 W, for instance), it is recognized asa logical "one". The smart adapterconsiders as invalid all the valuescomprised between the twothresholds.

Fig. 6 shows how the smart adaptermicrocontroller (MC1) can sendcommands to the appliance by meansof small interruptions of the supplyvoltage. To do this, a triac is used to

delay the current flowing to theappliance after a zero-currentdetection. The appliancemicrocontroller (MC2) recognizes thecommand by just measuring thevariation of the time intervalbetween two consecutive zero-voltage detections. Supposing amains frequency of 50 Hz, the timeinterval between two consecutivezero-voltage detections is 10milliseconds (t1 = 10 mS). When themicrocontroller MC1 imposes a delayof 3 or 5 mS to the flow of the electriccurrent, the time interval measuredby MC2 becomes 7 (t2) or 5 (t3)milliseconds respectively. Forinstance, assuming a fixed delay of 5mS (or 5000 µS) and considering afour-bit transmission (one nibble at atime), we can adopt time incrementsof 125 microsecond (µS) to movefrom the first configuration ("0000")to the last one ("1111"). In such acase, the total delay ranges from 5000µS (5000 + 0 µS, "0000" configuration)to 7000 µS (5000 + 2000 µS, "1111"configuration).

Power ModulationConcept

According to the previousstatements and considering the smartadapter as part of the domesticelectric system, power modulation isjust a very simple method fortransferring information from theappliance to the wiring system in arobust and reliable way, withoutadding any significant cost to theappliance itself. Regarding thenetwork protocol, it is included inthe communication node related tothe smart adapter concept; thereforethe white goods manufacturer canproduce high volumes of appliancesable to communicate with theexternal world, avoiding to deal withstrange, risky, and expensiveconcepts like "net-protocols" and"communication nodes". Thiscommunication capability not onlydramatically speeds up the in-linetesting phase and reduces the cost to1/10, but it can also be adopted forbetter assisting products on the field.

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Figure 5: Appliance-to-smart adapter transmission

Figure 6: Smart adapter-to-appliance transmission

It doesn’t mean that it is possibleto exclude definitively thecommunication node from the whitegoods, because such a node isnecessary when it is required toexchange continuously a big amountof data. It can happen, for instance,in the case of specific applicationsinvolving high-end solutions (seeFig. 7).

However, it is possible to install acommunication node inside a powermodulation based appliance withoutany interference, because the two

technologies are perfectly compatibleand can freely live together.Therefore, a power modulationbased appliance can be considered asan inexpensive and very opensolution, having the naturalcapability to exchange data throughits power cord, while being able tohost a communication node insidewhen a higher bit rate is requested. Itmeans: power modulationtechnology can become a "de factostandard".

Implementing "PowerModulation"

According to the above concept,implementing power modulationmeans considering the following twoaspects: the smart adapter and theelectronic control system of thedigital appliance.

Regarding the smart adapter, wehave to consider it as a part of thedomestic wiring system. Accordingto Fig. 8, there are severalpossibilities to include the concept ofsmart adapter inside a domesticelectrical wiring system.

The first example shows smartadapter as a device interposedbetween a normal outlet and anelectrical appliance, whether it isdigital or not.

The second example shows a smartadapter embedded in the wall outletwhich becomes a "smart" one.

In the third example a "multiplesmart adapter" is included in thewiring system and each power meteris connected to a normal outlet thatbecomes again a "smart" one. Thisinexpensive approach (only onecommunication node for severaloutlets, as shown in Fig. 9) isparticularly suited for new housesand renovation.

As concerns the appliance digitalcontrol system, Fig. 10 shows how toimplement power modulation usinga standard microcontroller: itsinternal software program cancontrol the two pins for receivingand sending data.

Another way for implementingpower modulation through amicrocontroller is by using a specifichardware function (peripheral)inside of it: a macrocell controlling Aand B pins.

Using a "power modulationmacrocell" inside the microcontrolleris absolutely the best way to

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Figure 7: power modulation versus standard home networks

Figure 8: smart adapter inside the wiring system

guarantee repetitive operations intransmitting and receiving data.Therefore it is the preferred methodfor implementing power modulationat the appliance level.

Power Modulation RoadMap

As described above, powermodulation technology involves twoindependent althoughcomplementary groups of activities:developing a "specificmicrocontroller" for designing newgeneration of appliance controlsystems, and promoting the conceptof domestic "smart wiring system"based on the smart adaptertechnology.

Fig. 11 shows all the main activitiesnecessary to quickly develop powermodulation based microcontrollers

and to promote the medium termconcept of "smart wiring system".

Smart adapter technology, alreadydeveloped and validated throughseveral indoor trials, is going toproduce a complete family ofcommercial products, whose firstexample was already shown as "case1" in the previous Fig. 8. Such aproduct uses Zensys’ Z-Waveprotocol, based on 868/915 MHzradio frequency transmission.

The concept of smart wiringsystem, supported by multiple smartadapter technology (Fig. 8, case 3), isan inexpensive mean to transformany domestic outlet in a measuringpoint, able to monitor the energyconsumption (class 1 measurement!)of the relative electrical appliance, tocreate useful information about itsfunctionality, and to talk directlywith digital products embedding the

power modulation based controlsystem.

However, to implementmicrocontrollers with a powermodulation peripheral inside, it isfirst necessary to develop and testthe "power modulation macrocell"using FPGA technology. In fact, themacrocell VHDL description will beused to quickly and easily implementthe power modulation peripheralinside the next generation of whitegoods microcontrollers.

Liberalizing PowerModulation

According to Wrap’s road map fordeveloping power modulation, thefirst microcontroller with such aperipheral inside will be available by2005. This microcontroller will beproposed as the future solution fordomestic electrical appliances,available as a royalty-free device forany manufacturer of white goods.Wrap, in fact, decided to liberalizepower modulation technology toopen the market to the connectedhome.

Two main benefits for the whitegoods manufacturers:

1) Producing white goods ready toconnect to a network at no addedcost and without the need to choosea home network protocol

2) Reducing time and cost for in-line products testing.

The last point is today the mostimportant one, because it offers tothe white goods manufacturer theopportunity to reduce bothproduction and maintenance costs.Fig. 11 shows an important examplefor dramatically reducing, fromhours to minutes, the testing processfor refrigerators.

Using the lamp inside eachproduct as resistive load fortransmitting data to the smart

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Figure 9:"smart wiring system" using multiple smart adapter technology

Figure 10: microcontroller for white goods applications

adapter, it is possible to inform thePC about the temperaturedecrements directly measured by theinternal probes, without using anyexternal data acquisition apparatusbased on thermocouples.

Furthermore, the smart adapterrelated to each refrigerator is able toanalyse the "electric signature" of itselectric loads (compressor, valve, fan,lamp …) to check for their properfunctionality.

In order to simplify the use ofpower modulation basedmicrocontrollers, Wrap intends tosupport them with several detailedapplication notes.

Conclusion

A new technology for connectingelectrical appliances to a network has

been presented. This technology,called "power modulation", isinexpensive and open, so it is verysuitable to solve the present bigproblems regarding white goodsinside a connected home: high cost ofthe communication node and lack ofa unique standard protocol.

Power modulation can be easilyimplemented just using a newgeneration of microcontrollers with aspecific macrocell inside.

Silicon manufacturers areinterested in producing suchmicrocontrollers since the whitegoods industry is a very attractivemarket to them considering its highvolumes.

Manufacturers of white goods, likeMerloni Elettrodomestici, areinterested in developing productsready to connect to a network, but

they ask for inexpensive solutionssuitable for high volumes and able tomeet the market’s constraints.Furthermore, they are very interestedin producing white goods that can betested easily and quickly withoutadding costs to the product.

Because power modulationtechnology can completely meet boththe above needs, Wrap intends toliberalize it in order to open themarket for "web ready" appliances,and also intends to licence thecomplementary technology (based on"multiple smart adapter") fordeveloping "smart wiring systems"for future connected home.

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Figure 11: power modulation road map

Figure 12: White goods in-line testing (refrigerator case study)