Wireless Based Load Control and Power Monitoring System

Transcription

1 Wireless Based Load Control and Power Monitoring System Raj Makwana, Jaypal Baviskar *, Niraj Panchal and Deepak Karia Department of Electronics and Telecommunication Sardar Patel Institute of Technology, Mumbai , India * nirajp101@gmail.com, Abstract Automations in industrial, commercial or residential sectors mostly depends upon the power systems, which requires distant controlling and monitoring. With the proliferation of wireless technologies, it is more efficient to implement an appropriate technology depending upon the cost, speed and distance requirements of the proposed system. This paper provides a comparative study of different wireless protocols such as ZigBee (over IEEE ) and Bluetooth (over IEEE ) for the selection of appropriate technology for Load Control. Further it describes a project model for remote controlling and monitoring of various loads/appliances and a means of efficient power utilization through real-time power consumption with the help of a PC-based GUI application. Keywords - Automation, Wireless Technologies, Load Control, Power Monitoring, ZigBee. I. INTRODUCTION In the past few decades, research and advancement in various areas including wireless communication has resulted into development in the field of automation. It incorporates different modern disciplines including communication, information, computer, control and wireless sensors in an integrated way leading to new solutions, better performance and complete systems [1]. Accessing networks and services without cables, wireless communication is a fast growing technology to provide flexibility and mobility. Reducing the cable restrictions will be one of the major benefits of wireless over cabled devices. Other benefits include the dynamic network formation, low cost, and easy deployment. On the other hand, managing the move to wireless, the challenge is to understand how to utilize wireless solutions as replacement for wired systems in time-critical scenarios. Wireless Sensor Networks (WSNs) have revolutionized the design of emerging embedded systems and triggered a new set of potential applications. As stated by Palanisamy et al. in [2] the unique characteristics of WSNs are: Limited power they can harvest or store Ability to withstand in harsh environmental conditions Ability to cope with node failures Mobility of nodes Dynamic network topology Heterogeneity of nodes Large scale of deployment Unattended operation Node capacity is scalable, only limited by bandwidth of gateway node. In [3], Jin-Shyan Lee et al. have given a detailed comparative study of different short-range wireless protocols viz. Bluetooth (over IEEE ), UWB (over IEEE ), ZigBee (over IEEE ) and Wi-Fi (over IEEE a/b/g). Main features and behaviors in terms of various metrics, including capacity, network topology, security, quality of service support, and power consumption are studied for the comparison. Our proposed model consists of two modules i.e. one Transmitter and one or more Receiver modules. The transmitter module which is interfaced to the controlling computer via serial connector consists of a Radio Frequency (RF) device. The receiver modules placed at the remote end consists of RF device interfaced with a micro-controller for controlling the loads via relays. The load considered for our model can have rating upto 230V (AC)/5A single phase. It can be resistive load such as incandescent bulb (residential), load bank or any electric heating load like Heater (Industrial). Even it can be an inductive load like various electric motors, transformers, etc. The power consumption can be estimated by measuring the electrical parameters i.e. voltage and current which will be processed and routed back to the RF device connected to the computer to provide real-time monitoring [4]. This paper is organized as follows. Section II deals with the different wireless technologies. Section III provides the comparative study of different technologies. Further details regarding the ZigBee protocol and network topologies are discussed in Section IV. Section V describes our designed system and the final Section presents the conclusion of our paper. II. WIRELESS TECHNOLOGIES The short-range wireless communication is held by four technologies viz. Bluetooth, UWB, ZigBee and Wi-Fi. Out of the seven layers of the Open Systems Interconnection (OSI) reference model, the IEEE standardizes only PHY and MAC layers for these wireless technologies. The specifications of Network, Security and Application Profile Layer are developed /13/$ IEEE 1207

2 by separate alliances of companies to realize the commercial potential of the standards. A brief overview of different wireless technologies is given below. A. Bluetooth over IEEE Bluetooth is a standard designed for short-range wireless radio systems to configure as Wireless Personal Area Network (WPAN). It can be used to replace cables for computer peripherals such as mice, keyboards, joysticks and printer. There are two network topologies defined i.e. the piconet and scatternet. A piconet is the type of connection that is formed between two or more Bluetooth-enabled devices such as modern cell phones or Personal Digital Assistants (PDA). A scatternet is a number of interconnected piconets that supports communication between more than 8 devices [5]. B. ZigBee over IEEE ZigBee is a standard created specifically for control and sensor networks for low data rate WPAN(LR-WPAN). Formed by the ZigBee Alliance in 2002, it restricts the data rate to 250 kbps in the global 2.4-GHz Industrial, Scientific, Medical (ISM) band while specifying low power consumption and cost. ZigBee provides self-organized, multi-hop, and reliable mesh networking with long battery lifetime [5], [6]. ZigBee protocol supports two functionality for its devices: a full-function device (FFD) and a reduced-function device (RFD). The FFD can operate in three modes serving as a PAN coordinator, a coordinator, or a device. The FFD can communicate with other FFDs and RFDs but an RFD can communicate only with an FFD. Out of the various devices in a PAN, only the PAN coordinator has greater computational resources as compared to other devices. C. Wi-Fi over IEEE a/b/g Wireless Fidelity (Wi-Fi) operates over IEEE a/b/g standards for Wireless Local Area Network (WLAN). It allows an electronic device to exchange data wirelessly over a computer network, including high-speed internet connections when connected to an Access Point (AP) or in an ad-hoc mode. The basic cell is called a basic service set (BSS), which is a set of mobile or fixed stations. As shown in Fig. 1 below, Independent BSS (IBSS) is possible when the stations can communicate directly without AP. The Distribution Systems (DS) used to connect BSS allows the creation of an Extended Service Set (ESS) network of arbitrary size and complexity. III. COMPARATIVE STUDY Table I below summarizes [7], [8] the key differences between the three short-range wireless technologies. As shown below, Wi-Fi provides higher data rates for multimedia access as compared to both ZigBee and Bluetooth which provides lower data transfer rates. ZigBee and Bluetooth are intended for WPAN communication (about 10m), while Wi-Fi is designed for WLAN (about 100m). Although certain ZigBee chipsets can reach a range of upto 100m. TABLE I COMPARISON OF THE BLUETOOTH, ZIGBEE, AND WI-FI PROTOCOLS Standard Bluetooth ZigBee Wi-Fi Application Focus Cable Monitoring and Web, , Replacement Control Video Frequency Band 2.4 GHz 868/915 MHz; 2.4 GHz 2.4 GHz; 5 GHz Max Signal Rate 1 Mb/s 250 Kb/s 54 Mb/s Nominal Range 10 m m 100 m Channel 1 MHz 0.3/0.6 MHz; 2 22 MHz Bandwidth MHz Data protection 16-bit CRC 16-bit CRC 32-bit CRC Max number of cell nodes 8 more than Table II below provides the comparison of the electrical parameters for the different chipsets of BlueCore2 [7] from Cambridge Silicon Radio (CSR), XB24-B [8] from Digi International Inc. and CX53111 [9] from Conexant (previous Intersils Prism), while Fig. 2 indicates power consumption in mw unit for each protocol. TABLE II ELECTRICAL PARAMETERS OF CHIPSETS FOR EACH PROTOCOL Standard Bluetooth ZigBee Wi-Fi Chipset BlueCore2 XB24-B CX5311 VDD (volt) TX (ma) RX (ma) Nominal TX power 0 to to 0 15 to 20 (dbm) Battery Life (days) Fig. 1. IBBS and ESS configuration of Wi-Fi network. Fig. 2. Comparison of the power consumption for each protocol. 1208

3 Since our proposed model is mainly concerned with the controlling and monitoring purpose, the data rates provided by Bluetooth and ZigBee are suitable for our application, whereas Wi-Fi is basically designed for multimedia access. Also the power consumption of Bluetooth and ZigBee is much less than Wi-Fi. Along with low power consumption and the possibility to increase the range of deployment, the network scalability offered by ZigBee is large as compared to Bluetooth [10], [11]. The comparison of above parameters leads us to select ZigBee as the wireless interface technology for our proposed system. IV. ZIGBEE PROTOCOL ZigBee is designed as a low-cost, low power, low-data rate wireless mesh technology. The applications those can be benefited from the ZigBee protocol are building automation networks, home security systems, industrial control networks, patient monitoring, remote metering, etc. modules are available with Advanced coding and Modulation techniques which can provide data rates upto 250 kbps. B. Network Topology for ZigBee The network layer of ZigBee supports star, tree and mesh topologies. The ZigBee Alliance s core specification defines ZigBee as an innovative, self-configuring, self-healing system of redundant, and a very low-power nodes [13]. In mesh networks each wireless node communicates with the one adjacent to it as shown in Fig. 4 below. If any one of the node fails, the information is automatically rerouted to allow devices to go on communicating without the failure of communication. Because of their rerouting capability, nodes on a ZigBee can walk through walls and even communicate with each other through building floors thereby making it suitable to be employed in office premises, campuses or factory units. A. ZigBee Protocol stack ZigBee uses the IEEE PHY and MAC layers to provide standard-based, reliable wireless data transfer (Refer Fig. 3). The ZigBee Alliance specifies the Logical Network, Security and Application Software to complete the communication suite. Further the interoperability and intercompatibility between similar products from different manufacturers are provided by ZigBee profiles defined in application layer [12]. Fig. 4. Network Topology for ZigBee The star topology being the most common network configuration is useful when endpoints are closely clustered and communicate with a single router node. This helps in reduction of the battery consumption at client nodes. Similarly the tree topology brings together several star networks with the data and control messages being transferred using hierarchical routing strategy. V. SYSTEM DESIGN Our designed system using ZigBee protocol is divided into three parts viz. User End System (UES), Load End System (LES) and Power Measurement Unit (PMU). The block diagram is as shown in Fig. 5 below: Fig. 3. ZigBee Protocol Stack The IEEE provides three frequency bands for communications. ZigBee uses a Direct Sequence Spread Spectrum (DSSS) radio signal in the 868 MHz band (Europe), 915 MHz band (North America) and the 2.4 GHz ISM band (available worldwide). In the 2.4-GHz ISM band sixteen channels are defined; each channel occupies 3 MHz and channels are centered 5 MHz from each other, giving a 2-MHz gap between pairs of channels. ZigBee uses an 11-chip PN code, with 4 information bits encoded into each symbol giving it a maximum data rate of 128 kbps. Currently, ZigBee Fig. 5. Block diagram of proposed system 1209

4 A. User End System (UES) UES mainly consists of two parts: PC and ZigBee module interfaced with PC via UART (Universal Asynchronous Receiver/Transmitter) port. Module of XBEE Series2 of Digi Inc. [8] is used as a part of ZigBee stack. The Xbee radios are programmed using X-CTU software in Application Programming Interface (API) mode with the desired baud rate [14]. Unlike the Transparent mode (AT mode), the API mode unleashes the full power of the Xbees and allows to construct a real wireless network consisting of two or more devices in the network. The module connected to PC is configured as ZigBee Coordinator API. A Java based GUI application is developed on PC which enables the user to control the load remotely. Fig. 6 and Fig. 7 below show the GUI windows. This application carries out operations such as switching ON/OFF the load and indicating their status. It also receives data from PMU through LES transreceiver and plots the real-time power consumption graph. different relays and the XBee radio reads its status and transmits it back to the UES. The relay card mainly consists of relays and the relay driving circuitry. Circuit layout for the same is shown in Fig. 8. Relays are used to provide isolation between a control circuit and load. In the circuit below, the transistor which drives the relay is used as switch and it is controlled by the control output pin of MCU. Change in the input voltage at base of transistor causes change in the base and collector current and eventually in the collector voltage. When the current in the relay coil (i.e. the collector current) exceeds a certain value, the relay switches on hence causes load to be turned on. The freewheeling diode provides (dv/dt) protection to control circuitry by reducing the large transient voltages that are produced due to the Inductive Kick. It is a phenomenon caused when the current through an inductor (the relay coil) varies rapidly. Fig. 6. GUI for Appliance Control. Fig. 8. Relay card circuit layout. In our project, the relay card is developed for controlling four different loads. Fig. 9 shows the actual relay card with Load no. 1 turned ON and its status reflected back on the GUI. Fig. 7. GUI for Power Monitoring. B. Load End System (LES) Both UES and LES are wirelessly linked by ZigBee with STAR topology. At LES, the ZigBee transceiver module is interfaced with the Controller Board and is configured as Zig- Bee Router API. Arduino controller board with ATmega328 microcontroller serves as MCU which is used to drive the relay or contactor to turn the load ON/OFF. The purpose of using Arduino board is because it is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software [15]. Also the microcontroller on the board (Atmel ATmega328) can be programmed using the Arduino programming language which is similar to the C programming language. The LES transceiver Module receives the control commands from the UES in the form of packages and forwards those to the controller board. The controller manages the Fig. 9. Relay Board with Appliance 1 turned ON. C. Power Measurement Unit (PMU) The PMU consists of a high-accuracy CMOS energy measurement IC CS5490 from Cirrus Logic that uses two Delta-Sigma ADCs to measure line voltage and current [16]. It 1210

5 calculates active, reactive and apparent power as well as RMS voltage and current. It works on a single 3.3V power supply along with low power consumption (less than 13mW). It is optimized to interface with current transformer, shunt resistors or Rogovaski coils for current measurement. It can also be interfaced with resistive dividers or voltage transformers for voltage measurement. The PMU design configuration using CS5490 to measure power in single-phase, two wire single voltage and current system as illustrated in Fig. 10. A current transformer (CT) is used to sense the line load current and a resistive voltage divider is used to sense the line voltage. The energy measurement IC CS5490 includes UART serial host to interface to an external microcontroller. MCU uses UART signals and reads the electrical parameters cyclically to forward it to the UES to plot the power consumption graph in real-time. Fig. 10. Power Measuring Unit. VI. CONCLUSION The wireless technology has been superseding the wired system design, by providing features such as mobility, low maintenance along with more security and compact systems. Moreover it can provide network communication at places where wired infrastructure would not be possible. ZigBee is one such efficient wireless protocol in terms of power consumption, scalability and it also provides a suitable data rate for controlling and monitoring purpose. This paper describes an embedded wireless system build using the ZigBee technology. A GUI application developed on the java platform provides a simple way of controlling and monitoring the various loads. Also the PMU unit continuously monitors the power consumption and displays a real time graph enabling the user to detect any over/under power consumption of the desired rated load. It will eventually help the user to detect some fault in the device or load connected to the system and carry out repair work in order to conserve energy. ACKNOWLEDGMENT We would like to express our gratitude towards Dr. Deepak Karia for his crucial guidance and assistance in our project and for being a constant source of inspiration to us. We are also thankful to our institute Sardar Patel Institute of Technology, Mumbai, India for providing the facilities to carry out our research and project work. REFERENCES [1] A. R. Raut, Dr. L. G. Malik, ZigBee: The Emerging Technology in Building Automation, Proceedings of International Journal on Computer Science and Engineering (IJCSE), vol. 3, no. 4, pp , Apr [2] S. Palanisamy, S. Senthil Kumar, and J. Lakshmi Narayanan, Secured Wireless Communication for Industrial Automation and Control, Proceedings of 3rd International Conference on Electronics Computer Technology (ICECT), vol. 5, pp , April [3] J. S. Lee, Y. W. Su, and C. C. Shen, A Comparative Study of Wireless Protocols: Bluetooth, UWB, ZigBee, and Wi-Fi, Proceedings of the 33 rd Annual Conference of the IEEE Industrial Electronics Society (IECON), pp , November [4] C. H. Lien, H. C. Chen, Y. W. Bai, and M. B. Linl, Power Monitoring and Control for Electric Home Appliances Based on Power Line Communication, Proceedings of IEEE International Instrumentation and Measurement Technology Conference, pp , May [5] E. Ferro and F. Potorti, Bluetooth and Wi-Fi wireless protocols: a survey and a comparison, Wireless Communications, IEEE, vol. 12, no. 1, pp , February [6] J. S. Lee, Performance Evaluation of IEEE for Low-Rate Wireless Personal Area Networks, IEEE Transactions on Consumer Electronics, vol. 52, no. 3, pp , August [7] BlueCore2-External Product Data Sheet, Cambridge Silicon Radio, Cambridge, UK, August [8] XBee Series 2 OEM RF Modules Product Manual, Digi nternational, Inc., June [9] Single-Chip WLAN Radio CX53111, Conexant Newport Beach, CA, [10] N. Baker, ZigBee and Bluetooth: Strengths and weaknesses for industrial applications, Proceedings of IEE Computing and Control Engineering, vol. 16, no. 2, pp 20-25, April/May [11] R. V. Sakhare, B. T. Deshmukh, Electric Power Management Using ZigBee Wireless Sensor Network, Proceedings of International Journal of Advances in Engineering and Technology (IJAET), vol. 4, Issue 1, pp , July [12] J. S. Lee and Y. C. Huang, ITRI ZBnode: A ZigBee/IEEE Platform for Wireless Sensor Networks, Proceedings of IEEE International Conference on Systems, Man, and Cybernetics, Taipei, Taiwan, vol. 2, pp , October 2006 [13] ZigBee-Setting Standards for Energy-Efficient Control Networks, White Paper by Schneider Electric Industries SAS, no. P EN, June [14] X-CTU Configuration and Test Utility Software User Guide, Digi International, Inc., August [15] Information about Arduino, [16] Two Channel Energy Measurement IC, Cirrus Logic,