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International Appliance Manufacturing 2004

Connecting white goods to a home network at a very low cost Valerio Aisa, Paolo Falcioni, Piero Pracchi Wrap S.p.A., Italy

The information generated and stored by a digital household appliance during normal operation can become very useful when acquired and processed by a remote Service Centre. This can be achieved through the connection of the appliance to a homenetwork via a proper "communication node", based on a suitable protocol (EHS/Konnex, LonTalk, Echonet, Z-Wave, Zig-Bee, Bluetooth, CEBus, X-10, UPB ‌).

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nfortunately, the cost of any communication node available today is absolutely incompatible with the well-known economic constraints that are peculiar to the white goods industry. Furthermore, a home network protocol recognized as a standard by all the actors involved with home automation isn’t yet available. Therefore it is presently impossible, for manufacturers of white goods, to produce and sell high volume of products with a communication node inside. To solve this problem, Wrap S.p.A.

(the R&D firm created through a spin-off by Merloni Elettrodomestici, the third European producer of white goods) has developed a breakthrough technology able to move the communication node (based on any protocol) from the white good to the electric mains (wiring system), without affecting the capability of the appliance to exchange information in a bidirectional way with the home network. As a consequence of this, white goods and any other electrical household appliance become completely free from communication cost and standard protocol selection issues. Therefore, according to this

Figure 1: Digital appliance fundamental requirements

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International Appliance Manufacturing 2004

inexpensive technology called "power modulation", any electrical appliance, simple or complex, could be connected to a home network for contributing in optimising the inhouse use of electricity and yet in helping manufacturers to guarantee high level maintenance services for the customer at a reasonable cost. Such a new technology is described in this document.

Digital Household Appliances The concept of "digital" applied to white goods involves something more than a simple use of a microcontroller, since it includes at least three distinctive elements: the existence of an electronic control system, the ability to generate and store useful information, and the possibility of exchanging this information with the outside world. The heart of the new generation of control systems for white goods applications is usually a microcontroller, able to manage signals generated by sensors, to control electric loads (solenoid valves, motors, pumps, fans, water heaters, and so on), to save useful data into non-volatile memories, and to exchange data outbound through a proper communication line. The information generated by the control system of a white good not only should include the data necessary to guarantee the correct operation of the appliance itself, but also data suitable for applications deriving from the network connection of said appliance. The information required for the correct operation of a digital appliance (Fig. 1) concerns the system status variables like temperatures, time intervals, water levels, working cycle progress phases, and so on. Another important information comes from

following two: EHS/Konnex and LonTalk. The former is implemented inside a standard microcontroller with specific software routines and uses a solid-state transceiver; the latter is included in the firmware of a As far as it concerns the NeuronChip (a specific device for information required for other networking purposes) and uses a purposes, it includes for instance statistical data (how many and which hybrid DSP based transceiver. Both of them are effective, robust and operating cycles were performed, reliable, but absolutely too expensive how the optional functions offered when used inside a white good; their by the appliance are used, how the detergent is used...), and data related full cost, in fact, ranges from 30 to 40 to electricity and water consumption. Euros (all included: PCB, connectors, power supply, box...) and can be This information can become very useful when acquired and processed accepted only by very high-end products. Furthermore, the European by a remote service centre, and this manufacturers of white goods are can be achieved by connecting the appliance to a proper home network presently divided in two "parties": some of them prefer EHS/Konnex, using a suitable "communication others prefer LonTalk, and others are node", that is a device able to dealing with both of them. But the communicate with other devices on market needs just a unique protocol the same network according to a to avoid confusion. specific protocol (set of rules for exchanging data inside a network). How to solve this problem? CECED, the European organization Typically a communication node of white goods manufacturers, has must be able to exchange data with the related digital appliance through created a specific working group to solve it and it is still investigating. a two-way serial link, and to communicate with the network using Furthermore, even though CECED will issue soon an Application a standard protocol and a proper Interworking Specification transceiver for the physical document, it is not recommending connection to the transmission line. any specific technology. Since white goods manufacturers have already decided to use power Therefore, the only way to solve line as transmission media, the the problem seems to be the transceiver included in the communication node is a "power line following: "eliminating the communication node from a white modem". Amongst the power line good, without affecting its capability based protocols that can be used in to exchange data with a home Europe, the most important are the diagnostic data, which are generated by a specific software routine that verifies the correct functionality for each individual operation.

Figure 2: Communication system based on "power modulation"

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International Appliance Manufacturing 2004

the smart adapter communicates with the home bus; with the power meter it analyses the electric current absorbed by the appliance and generates useful information (functional, statistical, diagnostic, and power/energy consumption data) related to the appliance itself. How a smart adapter can communicate with a digital appliance

Figure 3: Concept of Smart Adapter

network using any protocol". This statement could appear unrealistic, but, on the other hand, it is possible to demonstrate that it is absolutely realistic when a new inexpensive communication technology, called "power modulation", is used.

presented (see Fig. 1); on the other hand, the concept of smart adapter is a new one, created few years ago for networking traditional appliances.

Smart Adapter

"Power Modulation" Concept

The "smart adapter" (Fig. 3) is a device for connecting to a network any electrical appliance, which isn’t capable of communicating .

As shown in Fig. 2, power modulation technology comes from the following two concepts: digital appliance and smart adapter. Digital appliance concept has already been

The smart adapter embeds a communication node and a power meter, and it is located between an electrical appliance and its outlet. Thanks to the communication node,

Figure 4: Functional diagram of the Smart Adapter

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When the electrical appliance is a digital one, the "smart adapter" can communicate directly with it using its internal power meter to measure the electric current absorbed by the appliance during each cycle of the supply voltage. According to this concept, the digital appliance is able to send at least one bit per cycle (i.e.: 50 or 60 bits per second, depending on the value of the power line frequency) in a very robust and reliable way by just absorbing a small electric current (10 mA, for instance) using a small triac driving an inexpensive resistive load. Furthermore, the smart adapter can send commands to the digital appliance by just generating short and precise interruptions of the white good’s power supply; the digital control system of the appliance can then decode easily such commands by just measuring the variation of the time interval between two consecutive zerocrossing transitions of the line voltage. It is easy to demonstrate the possibility to send at least one nibble (four bits) at a time, without affecting the proper functionality of the appliance. According to Fig. 4, a smart adapter can be connected, for instance, to a network through a communication node based on LonTalk protocol and a PLT-22 power line transceiver, produced by Echelon Corporation (San Jose, CA); furthermore, it uses a power meter to receive bits (one bit at a time) from the appliance by measuring its instantaneous power consumption


International Appliance Manufacturing 2004

delay the current flowing to the appliance after a zero-current detection. The appliance microcontroller (MC2) recognizes the command by just measuring the variation of the time interval between two consecutive zerovoltage detections. Supposing a mains frequency of 50 Hz, the time interval between two consecutive zero-voltage detections is 10 milliseconds (t1 = 10 mS). When the microcontroller MC1 imposes a delay of 3 or 5 mS to the flow of the electric current, the time interval measured by MC2 becomes 7 (t2) or 5 (t3) milliseconds respectively. For instance, assuming a fixed delay of 5 Figure 5: Appliance-to-smart adapter transmission mS (or 5000 µS) and considering a four-bit transmission (one nibble at a power absorbed by the appliance time), we can adopt time increments during each cycle of the mains, and to send bits (four bit at a time) to the during each period of the mains, and, of 125 microsecond (µS) to move if the measured value is below a appliance through small and precise from the first configuration ("0000") determined low threshold (5 W, for voltage interruptions generated by to the last one ("1111"). In such a instance), it is recognized as a logical case, the total delay ranges from 5000 the triac. "zero"; otherwise, when this value is µS (5000 + 0 µS, "0000" configuration) to 7000 µS (5000 + 2000 µS, "1111" Fig. 5 shows how the appliance can greater than a given high threshold (7 W, for instance), it is recognized as configuration). send a logical "one" or "zero" by just a logical "one". The smart adapter absorbing/not absorbing power considers as invalid all the values during each cycle of the supply Power Modulation comprised between the two voltage. The appliance Concept thresholds. microcontroller (MC2) manages the electric current flow through a low According to the previous power (10 W, for instance) resistive Fig. 6 shows how the smart adapter statements and considering the smart load by sending pulses to the gate of microcontroller (MC1) can send adapter as part of the domestic the triac as soon as a voltage zero commands to the appliance by means electric system, power modulation is crossing is detected. The power just a very simple method for of small interruptions of the supply meter measures continuously the transferring information from the voltage. To do this, a triac is used to appliance to the wiring system in a robust and reliable way, without adding any significant cost to the appliance itself. Regarding the network protocol, it is included in the communication node related to the smart adapter concept; therefore the white goods manufacturer can produce high volumes of appliances able to communicate with the external world, avoiding to deal with strange, risky, and expensive concepts like "net-protocols" and "communication nodes". This communication capability not only dramatically speeds up the in-line testing phase and reduces the cost to 1/10, but it can also be adopted for better assisting products on the field. Figure 6: Smart adapter-to-appliance transmission

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International Appliance Manufacturing 2004

Implementing "Power Modulation" According to the above concept, implementing power modulation means considering the following two aspects: the smart adapter and the electronic control system of the digital appliance.

Figure 7: power modulation versus standard home networks

It doesn’t mean that it is possible to exclude definitively the communication node from the white goods, because such a node is necessary when it is required to exchange continuously a big amount of data. It can happen, for instance, in the case of specific applications involving high-end solutions (see Fig. 7). However, it is possible to install a communication node inside a power modulation based appliance without any interference, because the two

technologies are perfectly compatible and can freely live together. Therefore, a power modulation based appliance can be considered as an inexpensive and very open solution, having the natural capability to exchange data through its power cord, while being able to host a communication node inside when a higher bit rate is requested. It means: power modulation technology can become a "de facto standard".

Regarding the smart adapter, we have to consider it as a part of the domestic wiring system. According to Fig. 8, there are several possibilities to include the concept of smart adapter inside a domestic electrical wiring system. The first example shows smart adapter as a device interposed between a normal outlet and an electrical appliance, whether it is digital or not. The second example shows a smart adapter embedded in the wall outlet which becomes a "smart" one. In the third example a "multiple smart adapter" is included in the wiring system and each power meter is connected to a normal outlet that becomes again a "smart" one. This inexpensive approach (only one communication node for several outlets, as shown in Fig. 9) is particularly suited for new houses and renovation. As concerns the appliance digital control system, Fig. 10 shows how to implement power modulation using a standard microcontroller: its internal software program can control the two pins for receiving and sending data. Another way for implementing power modulation through a microcontroller is by using a specific hardware function (peripheral) inside of it: a macrocell controlling A and B pins.

Figure 8: smart adapter inside the wiring system

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Using a "power modulation macrocell" inside the microcontroller is absolutely the best way to


International Appliance Manufacturing 2004

power modulation based control system.

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

guarantee repetitive operations in transmitting and receiving data. Therefore it is the preferred method for implementing power modulation at the appliance level.

Power Modulation Road Map As described above, power modulation technology involves two independent although complementary groups of activities: developing a "specific microcontroller" for designing new generation of appliance control systems, and promoting the concept of domestic "smart wiring system" based on the smart adapter technology. Fig. 11 shows all the main activities necessary to quickly develop power modulation based microcontrollers

and to promote the medium term concept of "smart wiring system". Smart adapter technology, already developed and validated through several indoor trials, is going to produce a complete family of commercial products, whose first example was already shown as "case 1" in the previous Fig. 8. Such a product uses Zensys’ Z-Wave protocol, based on 868/915 MHz radio frequency transmission. The concept of smart wiring system, supported by multiple smart adapter technology (Fig. 8, case 3), is an inexpensive mean to transform any domestic outlet in a measuring point, able to monitor the energy consumption (class 1 measurement!) of the relative electrical appliance, to create useful information about its functionality, and to talk directly with digital products embedding the

However, to implement microcontrollers with a power modulation peripheral inside, it is first necessary to develop and test the "power modulation macrocell" using FPGA technology. In fact, the macrocell VHDL description will be used to quickly and easily implement the power modulation peripheral inside the next generation of white goods microcontrollers.

Liberalizing Power Modulation According to Wrap’s road map for developing power modulation, the first microcontroller with such a peripheral inside will be available by 2005. This microcontroller will be proposed as the future solution for domestic electrical appliances, available as a royalty-free device for any manufacturer of white goods. Wrap, in fact, decided to liberalize power modulation technology to open the market to the connected home. Two main benefits for the white goods manufacturers: 1) Producing white goods ready to connect to a network at no added cost and without the need to choose a home network protocol 2) Reducing time and cost for inline products testing. The last point is today the most important one, because it offers to the white goods manufacturer the opportunity to reduce both production and maintenance costs. Fig. 11 shows an important example for dramatically reducing, from hours to minutes, the testing process for refrigerators.

Figure 10: microcontroller for white goods applications

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Using the lamp inside each product as resistive load for transmitting data to the smart


International Appliance Manufacturing 2004

they ask for inexpensive solutions suitable for high volumes and able to meet the market’s constraints. Furthermore, they are very interested in producing white goods that can be tested easily and quickly without adding costs to the product.

Figure 11: power modulation road map

adapter, it is possible to inform the PC about the temperature decrements directly measured by the internal probes, without using any external data acquisition apparatus based on thermocouples.

been presented. This technology, called "power modulation", is inexpensive and open, so it is very suitable to solve the present big problems regarding white goods inside a connected home: high cost of the communication node and lack of a unique standard protocol.

Furthermore, the smart adapter related to each refrigerator is able to Power modulation can be easily analyse the "electric signature" of its electric loads (compressor, valve, fan, implemented just using a new generation of microcontrollers with a lamp ‌) to check for their proper specific macrocell inside. functionality. In order to simplify the use of power modulation based microcontrollers, Wrap intends to support them with several detailed application notes.

Silicon manufacturers are interested in producing such microcontrollers since the white goods industry is a very attractive market to them considering its high volumes.

Conclusion A new technology for connecting electrical appliances to a network has

Manufacturers of white goods, like Merloni Elettrodomestici, are interested in developing products ready to connect to a network, but

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

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Because power modulation technology can completely meet both the above needs, Wrap intends to liberalize it in order to open the market for "web ready" appliances, and also intends to licence the complementary technology (based on "multiple smart adapter") for developing "smart wiring systems" for future connected home.


2004 - Connecting white goods to a home network at a very low cost