GSM BASED PRE-PAID ENERGY METER Aeisha Vyas1, Sahil Kamboj2 1

Department of Electrical Engineering,G.Z.S. University, Bathinda, Punjab(India)

2

Department of Electronics and Communication Engineering, SRM University, NCR Campus(India)

ABSTRACT The aim of the project is to restrict the usage of electricity automatically and to eliminate paper based electricity bills. The project also aims at proposing a system that will reduce the loss of power and revenue due to power thefts and other illegal activities. The work system adopts a totally new concept of “Prepaid Electricity”. The GSM technology is used so that the consumer would receive messages about the consumption of power (in watts) and if it reaches the minimum amount, it would automatically alert the consumer to recharge. This technology holds good for all electricity distribution companies, private communities, IT parks and self-containing housing projects. The implementation of this project will help in conservation and management of energy, also it will rule out the unnecessary hassles over incorrect billing. It will reduce the consumption and also the confusion over the billing system.

Keywords: Global System for Mobile Communication (GSM), Microcontroller I. INTRODUCTION The GSM technology is used so that the consumer would receive messages about the consumption of power (in watts) and if it reaches the minimum amount, it would automatically alert the consumer to recharge. This technology holds good for all electricity distribution companies, private communities, IT parks and selfcontaining housing projects. The implementation of this paper will help in better energy management, conservation of energy and also in doing away with the unnecessary hassles over incorrect billing. The automated billing system will keep track of the real time consumption and will leave little scope for disagreement on consumption and billing. In this project we have shown the concept of prepaid energy meter which will automatically sense the energy consumed in the home and when it reaches to that value which is initially fed in the hardware it will disconnect the power line. A user interface is given in the hardware for user interface which will interact with the user with hardware, through user interface user can set a value or we can say a credit limit after which the user wants to be informed about that. GSM Decoder Section is that interface in this project, which will make the user to interact with the hardware so that user is able to initialize the hardware or can initially set the value. Power consumption measuring circuit will side by side measures the power which is being used in the house. The measured values are then sent to the microcontroller for further process and finally the SMS is send to the user via GSM Modem interfaced using a Max-232 circuit with the microcontroller. A keypad will be used to recharge the system.

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The present billing system is minimally able to detect power theft and even when it does it is at the end of the month. Also, the distribution company is unable to keep track of the changing maximum demand for domestic consumers. The consumer is facing problems like receiving due bills for bills that have already been paid as well as poor reliability of electricity supply and quality even if bills are paid regularly. The remedy for all these problems is to keep track of the consumers load on a timely basis, which will help assure accurate billing, track maximum demand, and detect online theft. These are all the features to be taken into account for designing an efficient energy billing system. The project “Microcontroller based prepaid energy meter”. Incorporate features to address the problems faced by both the consumers and the distribution companies. The paper mainly deals with the pre-paid energy meter: which utilizes the features of embedded system, which is the combination of hardware and software in order to implement desired functionality. The next session of the paper discuss comparison between microcontrollers and the compiler used to program the microcontroller. With the use of GSM modem one can recharge energy meter with the help of mobile. Also the amount left for usage will be continuously displayed on the LCD. This project will help in remote monitoring and control of the domestic energy meter. This system enables the electricity. Also the electricity department need not to go individually check the meters in order to take the readings. can be achieved by the use of microcontroller unit that continuously monitors and records the energy meter reading in its permanent (nonvolatile) memory location. This system also makes use of a GSM modem for remote monitoring and control of energy meter. The microcontroller based system continuously records the reading and the live meter reading can be sent to the electricity department on request. This system also can be used to disconnect the power supply to the house in case of non-payment of electricity bills. A dedicated GSM modem with SIM card is required for each energy meter.

II. VARIOUS COMPONENTS OF THE SYSTEM 2.1 Regulated Power Supply Power supplies are designed to convert high voltage AC mains to a suitable low voltage supply for electronic circuits and other devices. In our project the various electronic modules are being used for which power supply requirement is +5V DC. The Microcontroller unit needs a pure regulated +5V DC. A power supply can be broken down into a series of blocks, each of which performs a particular function. For example a 5V regulated supply. 2.1.1 Working of Power Supply  Transformer: Basically a step down transformer is used to step down 220V ac supply to a low voltage that is used to run electronic devices. Transformer + Rectifier: The low

voltage AC output is suitable for lamps,

heaters and special AC motors. It is not suitable for electronic circuits unless they include a rectifier and a smoothing capacitor.  Transformer + Rectifier + Smoothing: The varying DC output is suitable for lamps, heaters and standard motors. It is not suitable for electronic circuits unless they include a smoothing capacitor  Transformer + Rectifier + Smoothing + Regulator: The regulated DC output is very smooth with no ripple. It is suitable for all electronic circuits.

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2.2 Microcontroller 8051 Family A microcontroller has a CPU (a microprocessor) in addition to the fixed amount of RAM, ROM, I/O ports, and timers are all embedded together on the chip. Therefore, the designer cannot add any external memory, I/O, or timer to it. Microcontroller Unit is the heart of our project. It controls all the major activities of our project. The Microcontroller unit used in our project is based on MCS-51. In 1981, Intel Corporation introduced an 8-bit microcontroller called the 8051.This microcontroller had 128 bytes of RAM, 4K bytes of on-chip ROM, two timers, one serial port, and four ports (8-bit) all on a single chip. The other two members of MCS-51 series were 8052 and 8031 with different features. The 8051 became widely popular after Intel allowed other manufacturers to make any flavor of the 8051 they please with the condition that they remain code compatible with the 8051. This has led to many versions of the 8051 with different speeds and amount of on-chip ROM marketed by more than half a dozen manufacturers. It is important to know that although there are different flavors of the 8051, they are all compatible with the original 8051 as far as the instructions are concerned. This means that if you write your program for one, it will run on any one of them regardless of the manufacturer. The major 8051 manufacturers are Intel, Atmel, Dallas Semiconductors, Philips Corporation, Infineon. The Microcontrollers manufactured by these companies which were based on 8051 architecture are the MCS-51 based microcontrollers. In our project we will use from Atmel corporation AT89C52/AT89S52 having similar features of 8052. The benefit of using AT89S52 is that it is In-circuit system programmable (ISP) i.e. it can be reprogrammed without removing it from the application using ISP Programmer. But if we are using AT89C52 then if we have to reprogram it then first of all we have to remove it from our application then program it using its programmer and then install it again in the application to use. 2.2.1 Simple Switch Pad A switch is used as a human machine interface and is used to give input to the Microcontroller unit. A particular task can be performed by pressing a particular switch so microcontroller when senses that a switch is pressed then it performs the task corresponding to that switch. A switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another. A micro switch is a switch which can be operated using a very small force and also possibly using a small movement. This is a two terminal switch. Both terminals get shorted when it is pressed (i.e. in closed state) and both the terminals get disconnected when it is released (i.e. in open state). Any input signal is applied at one of its terminals and when it is pressed (i.e. in closed position) the same input signal is received at the other terminal. In our switch pad, there are three micro switches connected to the microcontroller I/O pins. One end of each switch is grounded and other is connected to the microcontroller port, as in Figure. When any switch is pressed that particular port pin is grounded. The microcontroller always monitors these switches in real time (i.e. in continuous mode). The configuration of micro switches is as follows: (1) Switch1 (S1): To increment (2) Switch2 (S2): To decrement (3) Switch3 (S3): To finalize/set

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2.2.2 Display Unit (Liquid Crystal Display) Display unit used in our project will be Liquid crystal display (LCD) which makes our project user friendly by displaying everything on the display. Liquid crystal displays (LCD) are widely used in recent years as compared to LEDs or seven segment displays, because LCD can be used to display alphanumeric as well as special characters (like * @!# % & etc.). Also due to the declining prices of LCD, the ability to display numbers, characters and graphics, incorporation of a refreshing controller into the LCD, there by relieving the CPU of the task of refreshing the LCD and also the ease of programming for characters and graphics. HD 44780 based LCDs are most commonly used. The LCD, which is used as a display in our project, is LMB162A. The main features of this LCD are: 16 X 2 display, intelligent LCD, used for alphanumeric characters & based on ASCII codes. This LCD contains 16 pins, in which 8 pins are used as 8-bit data I/O, which are extended ASCII. Three pins are used as control lines these are Read/Write pin, Enable pin and Register select pin. Two pins are used for Backlight and LCD voltage, another two pins are for Backlight & LCD ground and one pin is used for contrast change. 2.2.3 Relay River Using Optocoupler (Auto Electro Switching) Relay is an electrically operated switch. The relay's switch connections are usually labeled as COM, NC and NO: COM = Common, always connect to the moving part of the switch. NC = Normally Closed, COM is connected to this when the relay coil is off. NO = Normally Open, COM is connected to this when the relay coil is on. An Auto Electro Switching/Relay Driver circuit comprises of an Optocoupler which will isolate the controller from the outer spikes or fluctuations or from the external hardware and at the same time it drives a power transistor i.e. make it on when a signal from the controller pin is applied to it. Optocoupler actually comprises of a diode and a phototransistor. It comes in a DIP IC package. Thus signal from the MCU is given to the LED part or the driving part. When LED begins to glow then the phototransistor acts as on switch or short circuit. This output is given to power transistor, which will amplify the current of the signal and then can be used to drive a relay. The I/P signal is connected to the Relay’s “common” terminal and the O/P can be taken from the relay’s “NO” terminal. When relay is ON then “NO” is connected to the “common” terminal of the relay. 2.2.4 TTL to RS232 Line-Driver Module (MAX232) Some devices like PC, GSM Modem, and GPS Modem works on RS232 voltage standards which are not compatible with MCU’s TTL voltage standards. So MAX232 has to be used to make their communication compatible to each other. 2.2.5 RS232 Voltage Standards The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels for the data transmission and the control signal lines. Valid signals are plus or minus 3 to 15 volts; the ±3 V range near zero volts is not a valid RS-232 level. The standard specifies a maximum open-circuit voltage of 25 volts: signal levels of ±5 V, ±10 V, ±12 V, and ±15 V are all commonly seen depending on the power supplies available within a device. RS-232 drivers and receivers must be able to withstand indefinite short circuit to ground or to any voltage level up to ±25 volts.

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For data transmission lines (TXD, RXD and their secondary channel equivalents) logic one is defined as a negative voltage, the signal condition is called marking, and has the functional significance. Logic zero is positive and the signal condition is termed spacing. Control signals are logically inverted with respect to what one sees on the data transmission lines. When one of these signals is active, the voltage on the line will be between +3 to +15 volts. The inactive state for these signals is the opposite voltage condition, between −3 and −15 volts. Examples of control lines include request to send (RTS), clear to send (CTS), data terminal ready (DTR), and data set ready (DSR). Because the voltage levels are higher than logic levels typically used by integrated circuits, special intervening driver circuits are required to translate logic levels. These also protect the device's internal circuitry from short

circuits or transients that may appear on the RS-232 interface, and provide sufficient current to comply with the slew rate requirements for data transmission. 2.2.6 MAX232 This chip is used when interfacing micro controller with PC to check the Baud rate and changes the voltage level because micro controller is TTL compatible whereas PC is CMOS compatible. The MAX 232 IC contains the necessary drivers {two} and receivers {two}, to adapt the RS- 232 signal voltage levels to TTL logic. It became popular, because it just needs one voltage {+5V} and generates the necessary RS-232 voltage levels {approx. -10V AND +10V} internally. This greatly simplified the design of circuitry. And this made the IC so popular. MAX232 is just a driver/receiver. It does not generate the necessary RS-232 sequence of marks and spaces with the right timing, it does not decode RS-232 signal, it does not provide a serial /parallel conversion. All it does is to convert signal voltage levels.

2.2.7 GSM Voice & Data Transceiver (GSM MODEM) A GSM modem is a wireless modem that works with a GSM wireless network. A wireless modem behaves like a dial-up modem. The main difference between them is that a dial-up modem sends and receives data through a fixed telephone line while a wireless modem sends and receives data through radio waves. A GSM modem can be an external device or a PC Card / PCMCIA Card. Typically, an external GSM modem is connected to a computer through a serial cable or a USB cable. A GSM modem in the form of a PC Card /

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PCMCIA Card is designed for use with a laptop computer. It should be inserted into one of the PC Card / PCMCIA Card slots of a laptop computer. Like a GSM mobile phone, a GSM modem requires a SIM card from a wireless carrier in order to operate. Computers/MCUs use AT commands to control modems. Both GSM modems and dial-up modems support a common set of standard AT commands. You can use a GSM modem just like a dial-up modem. 2.2.8 Energy Meter IC (7768) The ADE7768 is an accurate electrical energy measurement integrated circuit. It is a pin reduction version of ADE7755 with an enhancement of a precise oscillator circuit that serves as a clock source to the chip. The ADE7768 eliminates the cost of an external crystal or resonator, thus reducing the overall cost of a meter built with this IC. The chip directly interfaces with shunt resistor. The ADE7768 provides instantaneous and average real power based on line current and voltage, and only accumulates when the power is positive – ignoring negative power. The part specifications surpass the accuracy requirements as quoted in the IEC61036 standard. The only analog circuitry used in the ADE7768 is in the ADCs and reference circuit. All other signal processing (e.g., multiplication and filtering) is carried out in the digital domain. This approach provides superior stability and accuracy over extremes in environmental conditions and over time. The small analog input full-scale allows the chip to interface to low value shunt resistances without losing dynamic range. The ADE7768 is available in 16-lead SOIC narrow-body package. The ADE7768 supplies positive-only average real power information on the low frequency outputs, F1 and F2. These outputs can be used to directly drive electromechanical counter or interface with an MCU. The high frequency CF logic output, ideal for calibration purposes, provides instantaneous positive-only, real power information. The ADE7768 includes a power supply monitoring circuit on the VDD supply pin. The ADE7768 remains inactive until the supply voltage on VDD reaches approximately 4 V. If the supply falls below 4 V, the ADE7768 also remains inactive and the F1, F2, and CF outputs are in their non-active modes. An internal no-load threshold ensures that the ADE7768 does not exhibit creep when no load is present. When REVP is logic high, the ADE7768 does not generate any pulse on F1, F2, and CF. The ADE7768 comes in a 16-lead, narrow body SOIC package.

III. WORKING The Microcontroller AT89S52 acts as the primary controller. The primary controller collects information from energy meter as well as from the smart card. Here, switches are used instead of the IC. Smart card, which is the switch, gives information about the limitation of units. The energy meter reading is compared with the smart card information by the microcontroller. Depending upon the result, the microcontroller will activate the buzzer if the credit is low and the Controller will trigger the Relay if the credit goes very low. The relay is the switching device to cut off and restore power supply.

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The LCD is interfaced to microcontroller using parallel port connection. The microcontroller based system, continuously records the readings. The coding emphasizes the fact that it reduces human labour but increases the efficiency in calculation of bills for used electricity. The user can be notified about the low balance in their credit with the help of the GSM module. The GSM modem is serially connected with the controller which is the major communication module between user and meter. The GSM uses its own network for the transfer of information. The programming makes use of messaging features of GSM AT command. And, once the relay is triggered, the electricity supply will be cut off. The power will be supplied again only if the meter is recharged with enough credit.

IV.

ADVANTAGES

OF

PROPOSED

METHODOLOGY

OVER

EXISTING

METHODOLOGY The present power usage reading is made manually by moving to the consumer locations. This requires large number of labor operators and long working hours to accomplish the task. Manual billing is sometimes restricted and delayed by bad weather conditions. The printed billing also has the tendency of getting lost. Over the last few years, Smart (Prepaid) Energy Meter has been proposed as an innovative solution aimed at facilitating affordability and reducing the cost of utilities. This mechanism, essentially, requires the users to pay for the electricity before its consumption. In this way, consumers hold credit and then use the electricity until the credit is exhausted. If the available credit is exhausted then the electricity supply is cutoff by a relay. Readings made by human operators are prone to errors. This project addresses the above mentioned problems. The development of GSM infrastructure in past two decades made meter reading system wireless. The GSM infrastructure, which has national wide coverage, can be used to request and retrieve power consumption notification over individual houses and flats. Apart from making readings using GSM communication, billing system is needed to be made prepaid to avoid unnecessary usage of power. The use of Prepaid Energy meter is still controversial. On the one hand, those that support the diffusion of prepaid meters claim that they benefit both consumers and utilities because they help users to consume more efficiently and to improve the management of their budget, while allowing firms to reduce financial costs. On the other hand, those that are against prepaid meters argue that their adoption is expensive for firms and risky for low income consumers, as the insecurity and volatility of their income may force them to make little use of the service, or ultimately, bring about involuntary self-disconnection.

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V. SOFTWARE REQUIREMENTS 5.1 Keil Software Keil software is used to provide us with software development tools for 8051based microcontrollers. With the help of Keil tools, we can generate embedded applications for virtually every 8051 derivative. The supported microcontrollers are listed in the µVision Device Database. The Keil software 8051 development tools are designed for the professional software developer, but any level of programmer can use them to get most out of the 8051 microcontroller architecture.

5.2 Software Development Cycle When we use the Keil µVision, the project development cycle is roughly the same as it is for any other software development project. 

Create a project. Select the target chip from the device database and configure the tool settings.



Create source files in C or assembly language.



Build the application with the project manager.



Correct the errors in source files.



Test the linked application.

VI. CONCLUSION Paper presents an overview of pre-paid energy meter, which can control the electricity usage on consumer side to avoid wastage of power. Pre-paid meter proves to be a boon in the power sector since it helps in efficient use of power. The major drawback of a postpaid system is that there is no control of usage from the consumer's side therefore there is a lot of wastage of power due to the consumer’s lack of planning of electrical consumption in an efficient way. Since the supply of power is limited, as a responsible citizen, there is a need to utilize electricity in a better and efficient way. The billing system is minimally able to detect power theft and even when it does at the end of the month. Also, the distribution company is facing many problems in terms of losses. The distribution company is unable to keep track of the changing maximum demand for domestic consumers. The consumer is facing problems like receiving due bills for bills that have already been paid as well as poor reliability of electricity supply and quality even if bills are paid regularly. The remedy for all these problems is to keep track of the consumers load on a timely basis, which will help assure accurate billing, track maximum demand, and detect online theft, which is possible with a prepaid energy meter. These are all the features to be taken into account for designing an efficient energy billing system. The present project incorporates these features to address the problems faced by both the consumers and the distribution companies.

VII. FUTURE SCOPE Rather than sending the bill we can send it using a printer. When the command is given by the electricity company, bill will be generated automatically at the user end.

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VIII. ACKNOWLEDGMENT To begin with, we would like to express our gratitude to our beloved HOD, Dr. Sarabjeet Kaur Bath, for having given us an opportunity to pursue our academic interests and for the insightful comments and support throughout. We are deeply indebted to our project guide Er. Sonia Grover, Assistant Professor, Department of Electrical Engineering, for her constant support and encouragement throughout the course of our major project. We are grateful for her constructive criticism during the course of the major project, which helped us to make necessary improvements. Last not the least we would like to thank all the teachers of the Electrical Department for giving us opportunity and their kind cooperation.

REFERENCES [1] Saptarshi De, Rahul Anand, A Naveen and SiratMoinuddin, “E-Metering Solution for checking energy thefts and streamlining revenue collection in India”, Student Member, IEEE, 2003. [2] Ali Zaidi.S.K., “Design and implementation of low cost electronic prepaid energy meter”, Multitopic Conference, 2008.INMIC 2008.IEEE International 2008. [3] Syed Khizar Ali Zaidi I, HuraMasroor I, Syed Rehan Ashraf I and Ahmed Hassan, “Design and Implementation of Low Cost Electronic Prepaid Energy Meter”, NED University of Engineering and Technology, Karachi, Pakistan, 2010. [4] Hura Masroor I, Syed Rehan Ashraf I and Ahmed Hassan, “Design and Implementation of low cost Electronic Prepaid Energy Meter’, NED University of Engineering and technology, Karachi, Pakistan, 2010.

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