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IEEE Transactions on Consumer Electronics, Vol. 53, No. 4, NOVEMBER 2007

Contributed Paper Manuscript received September 11, 2007 0098 3063/07/$20.00 © 2007 IEEE

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Remote-Controllable Power Outlet System for Home Power Management

Chia-Hung Lien, Ying-Wen Bai, and Ming-Bo Lin, Member, IEEE

Abstract — In this paper we describe the Wireless Power-

Controlled Outlet Module (WPCOM) with a scalable mechanism for home power management which we have developed. The WPCOM integrates the multiple AC power sockets and a simple low-power microcontroller into a power outlet to switch the power of the sockets ON/OFF and to measure the power consumption of plugged electric home appliances. Our WPCOM consists of six scalable modules, that is, the Essential Control Module, the Bluetooth Module, the GSM Module, the Ethernet Module, the SD Card Module and the Power Measuring Module, which together provide an indoor wireless, and an outdoor remote control and monitor of electric home appliances. We have designed a PDA control software and remote control software which support the Graphic User Interface, thus allowing the user to easily monitor the electric home appliances through the PDA and the Internet individually. In addition, we use a Short Message Service to achieve control and monitoring through a GSM cellular mobile phone for remote use anytime and anywhere1.

Index Terms — Home Power Management, Bluetooth, Short Message Service, Remote-Controllable Outlet System.

I. INTRODUCTION Home power consumption tends to grow in proportion to

the increase in the number of large-sized electric home appliances. Home power management is required to save energy and reduce carbon dioxide emissions [1]. To implement home power management, networked electric home appliances with control/monitoring capabilities and home networks without new wiring are indispensable. Together with the construction of access networks, several standards for wired home networks have been proposed and developed [2].

The Plug & Play function is indispensable for a home network so that the user can install and replace electric home appliances without need for any special knowledge. The Plug & Play function discovers electric home appliances in a network, assign an ID to each appliance, and generates an entry for controlling and monitoring the interface from the home network [3]. However, electric home appliances without expansive functions and a conventional power plug which have deteriorated from their interference have made it difficult to build such advanced systems [4].

1 Chia-Hung Lien and Ming-Bo Lin are with the Department of Electronic

Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, 106, R.O.C. (e-mail: [email protected]).

Ying-Wen Bai are with Department of Electronic Engineering, Fu Jen Catholic University, Taipei, Taiwan, 242, R.O.C.

The Home Energy Management System (HEMS) divides the network capability by means of both minimum interface software embedded in electric home appliances and separated network adapters. Setting up a system without new wiring is a major concern in a wide variety of applications such as video monitoring, power control and the management of electric home appliances [1]. Imagine a private home equipped with motion, light, temperature and other sensors and actuators for opening the door, dimming the light, controlling the heating and so on. These sensors/actuators can be used to enhance the individual’s lifestyle, e.g. the heating is turned on automatically when the owner of the house comes home and the light is switched on in rooms where motion is detected. Existing solutions for home automation fall short in that most of them do not address security aspects in an appropriate way [5]-[7].

RS-232 hardware is an interface of easy design and in popular in today’s industrial environment. However, RS-232 communications have a very big drawback in that floor environments often generate electrical noise and transients which can cause errors in transmission and damage to the interface components. Another drawback of RS-232 is its point-to-point characteristic and a distance limitation of 15 m.

A typical IP power device can remotely control all power switches of electric home appliances. As this module is without limitation and is conveniently applied with any computer or software, the user need not open the computer chassis. By use of the Internet connection with an RJ45 this module can be connected to any computer.

Home network devices are categorized as wired devices. The power line communications (PLC) provide high bit-rate data services by using the power grid residing in the vast infrastructure already in place for power distribution, which means that the potential effect of the service could be much higher than that of any other wire line alternative [1]. The PLC are used to connect lighter appliances like refrigerators, microwave ovens and washing machines. Despite the enormous potential of the PLC, there still is skepticism about this technology and its commercial viability. This is mainly due to several still unresolved technical problems and regulatory issues.

The other main category of wireless technology is radio frequency (RF). RF technology is a more flexible technology which allows the users to link electric home appliances that are distributed throughout the house [7]. RF can be categorized as a narrow band or spread spectrum. Narrow band technology requires a clear channel uninterrupted by other digital appliances. Since each transmitter/receiver

C.-H. Lien et al.: Remote-Controllable Power Outlet System for Home Power Management 1635

appliance transmits using its own frequency, it is unlikely to interfere with other RF appliances connected to the home network. However, if the wireless appliance is moved to another part of the house, it is possible that interference may occur. This limitation makes the use of this technology unsuitable for a number of home network applications [8].

Bluetooth technology provides a universal bridge to existing data networks, a peripheral interface and a mechanism to form small private ad hoc groupings of connected devices away from fixed network infrastructures. Designed to operate in a noisy radio frequency environment such as a home, the Bluetooth technology uses a fast acknowledgement and frequency-hopping scheme to make the link robust. Bluetooth technology would replace the cumbersome cables used today to connect the PDA to any other digital device which is part of the Bluetooth network [9].

Mobile phones have become one of the most popular communication devices among most of the people around the world, and the Short Message Service (SMS) is popular among mobile phone users as a cheap and convenient method of communicating. Therefore, SMS technology is a common feature with all mobile network service providers. Since the use of SMS technology is a cheap, convenient and flexible way of conveying data, researchers are trying to apply this technology in many different areas that are not covered by service providers at present [10], [11].

A comparison of home power management methods is shown in Table I. These technologies show the large difference between indoor and outdoor communication.

TABLE I

TECHNICAL COMPARISON

Method 1

Method 2

Method 3

Method 4

Method 5 (Our

design) Indoor

commu-nication

RS 232 Wired Ethernet

LAN

Power Line

Communi-cation

RF Bluetooth

Indoor control device

PC PC PC PC and device

with RF receiver

PDA or Bluetooth devices

Outdoor commu-nication

Tele-phone

network

Internet Internet Internet Internet/ GSM

Remote control device

PC PC PC PC PC/ GSM phone

A remote-controllable power outlet system (Method 5) with

a wireless mechanism for home power management has been developed in this paper. By using the Bluetooth technology, electric home appliances can be controlled and monitored without wire lines. The user can also manage electric home appliances remotely by the GSM and Internet technologies to save power, as shown in Fig. 1. We have designed the Wireless Power-Controlled Outlet Module (WPCOM) which integrates the multiple AC power sockets and six scalable

modules into a power outlet to perform the control and monitoring of the power consumption of plugged electric home appliances, and which is set up easily and is user-friendly. Moreover, the Bluetooth technology supports both point-to-point and point-to-multi-point connections. A collection of the PDA with Bluetooth that is connected to the WPCOM plugged electric home appliances via Bluetooth network is called a piconet, as shown in Fig. 1.

Fig. 1. Remote-controllable power outlet system.

This paper is organized as follows. In Section 2 the

WPCOM is introduced. In Section 3 the user-friendly control design is described. In Section 4 the implementation results are summarized. In Section 5 our conclusions are presented.

II. WPCOM DESIGN An AC power outlet is an electrical device consisting of a

cord with a plug on one end and several sockets on the other. The WPCOM connected to an AC power outlet is made up of multiple AC power sockets, an Essential Control Module, a Bluetooth Module, a GSM Module, an Ethernet Module, a SD

IEEE Transactions on Consumer Electronics, Vol. 53, No. 4, NOVEMBER 2007 1636

Card Module and a Power Measuring Module. The complete block of the WPCOM is shown in Fig. 2.

Fig. 2. The complete block of the WPCOM.

To provide a scalable configuration with different costs and characteristics, we have designed the WPCOM based on the function module mechanism. Table II shows the basic functions of each module.

TABLE II THE BASIC FUNCTIONS OF EACH MODULE

Module Function GSM Module Allows a GSM mobile to send text messages to turn

electric home appliances ON/OFF and to receive up-to-date measurement information directly

Bluetooth Module

Electric home appliances can be controlled by PDA over the Bluetooth home network in the home

Ethernet Module Allows the user to configure and monitor electric home appliances over the Internet

SD Card Module Uses an SD card for storage to hold the measurement information

Power Measuring Module

Shows the real time measuring power status of the electric home appliances

Essential Control Module

Executes the basic functions of the system and carries out electric home appliances control

We have used the Solid State Relays (SSR) to switch each

socket into which an electric home appliance can be plugged. SSR have been utilized to replace mechanical relays because of their many advantages, including miniaturized configuration, elimination of contact bounce, low-energy consumption, decreased electrical noise, compatibility with digital circuitry and high-speed switching performance. These SSR also provide isolation between a control circuit and a switched circuit.

The microcontroller in the Essential Control Module has four functions: processing commands from the Bluetooth Module and the Ethernet Module and SMS commands from the GSM Module, controlling the SSR ON/OFF, monitoring

the status of electric home appliances and transmitting the power status and measured data to the SD (Secure Digital) Card Module. The complete circuit diagram of the Essential Control Module is given in Fig. 3.

Fig. 3. Circuit diagram of the Essential Control Module.

The GSM Module is specifically designed to connect to the

Essential Control Module thus allowing calls to be made using the GSM cellular mobile phone network. Because the GSM Module is supplied SIM Card-free by the service provider the user can use the network of his choice. The GSM Module provides a remote GSM mobile to control the system using the SMS. The complete circuit diagram of the GSM Module is given in Fig. 4.

Fig. 4. Circuit diagram of the GSM (SMS) Module.


The Bluetooth Module is a low-power embedded Bluetooth v2.0+EDR module with a built-in high-output antenna. The module is a fully Bluetooth compliant device for data communication with a transmission power of up to +8dBm and receiver sensibility of down to -83dBm combined with low power consumption.

The Bluetooth Module delivers opportunities for rapid ad hoc connections and the possibility of automatic, unconscious, connections between WPCOMs. The complete circuit diagram of the Bluetooth Module is given in Fig. 5.

Fig. 5. Circuit diagram of the Bluetooth Module.

The Ethernet Module is a true Serial-to-Ethernet converter

that connects electric home appliances to the Internet based on UDP protocol, thus allowing the user to control and monitor electric home appliances over the Internet. The complete circuit diagram of the Ethernet Module is given in Fig. 6.

Fig. 6. Circuit diagram of the Ethernet Module.

To show the actual status of the electric home appliances,

and to control the power ON/OFF we use the Power Measuring Module, which is a measuring circuit containing four parts: six current transformers (CT), an electrical power detector, a multiplexer and a power load microprocessor. The six CT are installed in the AC power outlet, as shown in Fig. 3. The load current of each socket is measured by the CT. By using the Hall Principal Effect the charge carriers in the CT become deflected by the magnetic field and give rise to an electric field which is perpendicular to both the current and the magnetic field, as the load current changes the output voltage signal. The voltage signal is transited to the power

measuring module via the connector. The electrical power detector transforms the voltage signal as digitized data for the power load microprocessor. The power load microprocessor receives each socket datum via the multiplexer. The complete circuit diagram of the Power Measuring Module is given in Fig. 7.

Fig. 7. Circuit diagram of the Power Measuring Module.

The SD Card Module is to store the status and measurement

data of the electric home appliances. It provides an interrupt type of transfer mode to improve the data transfer performance between the microcontroller and the SD Card. The complete circuit diagram of the SD Card module is given in Fig. 8.

Fig. 8. Circuit diagram of the SD Card Module.

Fig. 9 shows the control flow chart of the WPCOM. In the

initial mode of the WPCOM the system mechanism checks the hardware configuration to detect which module is installed in the WPCOM.

If the Power Measuring Module is installed in the WPCOM, the system measures the power consumption of each socket cyclically. The sources of the control commands can be the


PDA, the Internet and the GSM. If there are no control commands, the microcontroller stores the current power status. If the system has received a command, it checks to see whether the command is for the room controlled by the WPCOM or not. If it is, the microcontroller turns the power ON/OFF or sends power data according to the command. If the command is not for any room controlled by the WPCOM, the command is broadcast over the Bluetooth home network.

Fig. 9. The control flow chart of the WPCOM program.

III. USER-FRIENDLY CONTROL DESIGN

A. Remote Control by GSM Cellular Mobile Phone The WPCOM provides the user with a way to control and

monitor the power of electric home appliances by using GSM cellular mobile phone as shown in Fig. 1. When the remote user send the SMS with a control command by a GSM cellular mobile phone to the phone number of the WPCOM, the WPCOM receives it and checks whether the sender is allowed to control the home network. Then the WPCOM confirms the SMS command format. If the message fits in with the command format, the WPCOM changes the power state of electric home appliances or sends an SMS with the power data to the GSM cellular mobile phone. Thus the user can control and monitor the power state by use of the GSM cellular mobile phone anytime, anywhere.

With a GSM module installed in a WPCOM it is possible using a GSM cellular mobile phone to:

1. Request the current status (ON/OFF) and power consumption of any socket in a WPCOM.

2. Set any the current status of any socket in a WPCOM to a new status.

3. Receive a notification (alert) message that a predefined condition has been met.

Tables III and IV show all possible commands that can be sent via an SMS with a brief description of the command functions. The current readings of information monitored by the WPCOM can be requested at any time by simply sending an SMS containing the desired command to the WPCOM, as shown in Table III.

TABLE III

“ GET” COMMANDS

Command Execution Get help Returns a message listing all valid commands

Get sockets Returns a message showing a summary of all socket status

Get values Returns a message showing the current readings of monitored power values

Get alarm Returns a message showing a summary of alarm conditions

Example 1: Fig. 10 shows how to get the current readings

of the power monitored. The first line of the message displays the Room name followed by a colon (:).

Fig. 10. Getting the current readings of the monitored power using SMS.

The following commands which start with the word “Set”

are used to request a power datum from the WPCOM for changing or entering information into the unit, such as alarm threshold values, alarm enables, entering passwords or switching sockets ON/OFF, as shown in Table IV.


TABLE IV “ SET” COMMANDS

Command Execution Set sockets Switches the sockets ON/OFF

Set alarms Selects which alarms are to be enabled

Set limits Sets the various alarm thresholds

Set system Sets various system values, such as the user name, passwords etc

Example 2: Fig. 11 shows how to switch the sockets

ON/OFF. The template shows the current status of the socket and provides the correct format for changing the settings. Setting the socket value to “1” turns the corresponding socket on; setting the socket value to “0” turns the corresponding socket off.

Fig. 11. Switching the sockets ON/OFF using SMS.

B. Wireless Control by PDA The PDA with Bluetooth that is connected to the WPCOM

plugged electric home appliances via the Bluetooth network controls and monitors the electric home appliances indoor.

We have designed this PDA control software using Visual Studio 2005, which supports the Graphic User Interface (GUI) thus allowing the user to easily control and monitor the electric home appliances’ power ON/OFF. As shown in Fig. 12, the PDA shows the power status of each socket in the display area. The status fields show whether any electric home appliances plugged in the sockets are in use or not. The PDA shows the power consumption and the accumulated energy used by each electric home appliance in the display area.

In the control field of Fig. 12 the PDA sets up ON/OFF and sends a command to the WPCOM immediately after pressing the “ON/OFF” button. The PDA waits for an acknowledge command from the WPCOM. The control field sends its command every three seconds if it doesn’t receive an acknowledge command, to guarantee that the power control command can be executed without being lost.

Fig. 12. The GUI of the PDA control software.

C. Remote Control by Internet We have designed this remote control software using a

typical Winsock and network protocol component to transmit/receive commands. The remote control software is installed in the PC or the Notebook connected to the Internet. It can control electrical home appliances when the user is outdoor.

The structure of the network connection of the remote control by Internet is a Host-Client structure. The client installed remote control software sets the IP address and PORT, then sends a request to the WPCOM, creates a link and starts to link both client and WPCOM, as shown in Fig. 13. The remote user can access a WPCOM with the Internet connection.


By means of the Internet the user can control and monitor the power consumption status of the electric home appliances. The remote control software uses a GUI which provides the user with an easy way to control/monitor the power status of electric home appliances.

As shown in Fig. 13, the remote control software shows the power status of each socket at the display area. The red light shows that the electric home appliance is in use and the white light shows that the appliance is off. The remote control software also shows the accumulated energy of each electric home appliance in the display area. In the control area the user can set up the sockets for the ON/OFF state and send the command to the WPCOM immediately after pressing the “Set up” button. The remote control mechanism provides the user with a way to penetrate the Internet to monitor and control the power status of the electric home appliance.

Fig. 13. The GUI of the remote control software.

IV. IMPLEMENTATION RESULTS The final implementation of the WPCOM is shown in Fig.

14. The entire hardware prototype circuit of the WPCOM is now implemented on a 5 cm × 6.5 cm printed circuit board (excluding the SSR and sockets).

Fig. 14. The AC power plug controlled by the MCU.

By using Bluetooth the WPCOM enables the home network user to connect a wide range of electric home appliances easily and simply, thus eliminating the need to purchase proprietary or additional cabling to connect individual devices. The user needs only to follow three steps to finish installing the remote- controllable power outlet system indoors.

1. Replace the conventional outlet with a WPCOM to provide AC power for the electric home appliances.

2. Install the PDA control software in the PDA by which the user controls the electric home appliances.

3. Connect the PDA to the WPCOM by the Bluetooth search. Then the user can display and control the electric home appliance’s power ON/OFF by using the PDA.

The WPCOM also consumes power. The average current of a GSM Module is 65 mA with maximal 82 mA while communicating, that of the Bluetooth Module is 33 mA and 45 mA. The average current of an Ethernet Module is 25 mA, that of the SD Card Module, the Power Measuring Module and the Essential Control Module is 21 mA, 23 mA and 47 mA respectively. The average power consumption of the WPCOM can be calculated as shown in Table V. The total power consumption of a WPCOM is about 1.04 W and increases when the number of sockets of the WPCOM increases.

TABLE V

THE AVERAGE POWER CONSUMPTION OF THE WPCOM MODULE Item Average

current (mA) Operation voltage (V)

Average power consumption (W)

GSM Module (1800MHz)

65 5 0.32

Bluetooth Module 33 5 0.16

Ethernet Module 25 5 0.12

SD Card Module 21 5 0.10

Power Measuring Module

23 5 0.11

Essential Control Module

47 5 0.23

Total 214 5 1.04

An additional advantage of the Power Measuring Module is that it also detects the use status of an electric home appliance’s power, in addition to controlling the sockets’ ON/OFF state. In this experiment the Power Measuring Module detects an electric home appliance’s power consumption ranging from 1 W to 1200 W. We can extend the range to detect lower and higher power consumption from 0.47 W to 2500 W by changing the CT which can increase its volume by half.

We have compared our design with other home power management designs. The result demonstrates that our design is better than others because it has more integrated functions. The details of our comparison detail are shown in Table VI.


TABLE VI COMPARISON OF THE HOME POWER MANAGEMENT DESIGNS Wireless Portable Length* Setup Power

Detection Method 1 X Yes Line Com-

plicated X

Method 2 X X Line (3-5 m)

Com-plicated

X

Method 3 X X Line Easy Yes

Method 4 Yes X Line Com-plicated

X

Method 5 (Our design)

Yes Yes 10 m Easy Yes

*Because at present the Bluetooth technology transmission length is about 10-20 m, the WPCOM transmission is between 10-20 m. Other methods use a transmission line.

V. CONCLUSION In this paper a remote-controllable power outlet system and

the key components for home power management have been developed. To realize remote control, the Bluetooth, the GSM and the Internet technologies for power management have been integrated. The proposed WPCOM is designed for wireless monitoring and controlling of different electric home appliances connected over a Bluetooth network in a home environment. The WPCOM also allows a GSM cellular mobile phone using SMS and PC or Notebook using the Internet to monitor and control electric home appliances at remote locations.

The field experiments reported in this paper have demonstrated that this new system can be practically implemented and provides adequate results. While this study has its limitations, it is hoped that it will serve as a basis for further study of home power management strategies for various electric home appliances.

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Chia-Hung Lien is currently working toward the Ph.D. degree in Electronic Engineering at National Taiwan University of Science and Technology. He received his M.S. degree in electronic engineering from Fu-Jen Catholic University in 2000. His research interests include low power systems design, mobile computing, parallel architectures and algorithms, and embedded computer systems.

Ying-Wen Bai is a professor in the Department of Electronic Engineering at Fu-Jen Catholic University. His research focuses on mobile computing and microcomputer system design. He obtained his M.S. and Ph.D. degrees in electrical engineering from Columbia University, New York, in 1991 and 1993, respectively. Between 1993 and 1995, he worked at the Institute for Information Industry, Taiwan.

Ming-Bo Lin (S'90-M'93) received the B.Sc. degree in electronic engineering from the National Taiwan Institute of Technology (now is National Taiwan University of Science and Technology), Taipei, the M.Sc. degree in electrical engineering from the National Taiwan University, Taipei, and the Ph.D. degree in electrical engineering from the University of Maryland, College Park. Since February 2001, he has been a professor with the Department of Electronic Engineering at the National

Taiwan University of Science and Technology, Taipei, Taiwan. His research interests include VLSI systems design, mixed-signal integrated circuit designs, parallel architectures and algorithms, and embedded computer systems.