PHOTO ENCODING OF ANALOG WATER METER FOR USER ACCESS AND PAYMENT SYSTEM

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1 PHOTO ENCODING OF ANALOG WATER METER FOR USER ACCESS AND PAYMENT SYSTEM GODFREY A. MILLS Department of Computer Engineering, University of Ghana, P. O. Box LG 25, Legon, Accra, Ghana MOSES A. ACQUAH Department of Computer Engineering, University of Ghana, P. O. Box LG 25, Legon, Accra, Ghana APPAH BREMANG Department of Computer Engineering, University of Ghana, P. O. Box LG 25, Legon, Accra, Ghana Abstract This paper presents design reconfiguration of analog water meter to provide remote access to user water consumption and billing records, payments, and meter device monitoring using photo-encoding as the detecting method for water consumption, a PIC18F2423 microcontroller for data processing, and SMS (short message service) technology for data transportation. To validate the system design, an analog water meter was converted into a digital equivalent and interfaced to the cellular network to transmit parameters of the meter to-and-from a consolidation server (CS). The prototype was tested for operations such as user consumption and billing records, payments, device control, and tamper notification. Test results conducted within a 12km radius gave an average response time of 16 seconds spanning from time of SMS request to the CS to read data from meter through data processing and submission to user. To manage system congestion from multi-users, a multi-threaded algorithm was implemented with each SMS request handling a single thread. Keywords: Photo-encoding; Microcontroller; GSM; GPRS; SMS; Consolidation Server; Google Map 1. Introduction Conventionally, water meter reading and billing in many countries have largely followed a mechanical process where agents of the utility physically visit the premises of the users and manually record the consumption data for bill development and delivery for payment. With the advent of solid state electronics coupled with modernization of the telecommunication networks, electronic meters with remote operational capabilities have been developed and implemented by many companies for the water, electric, and gas utilities [1-4]. The key element in these electronic meters apart from the flow detection is the communication systems for the transmission of the data and control signals between the meter interface and the central office. Several communication technologies such as radio frequency (RF), telephone lines, and TCP/IP protocols for the data transportation over the internet and other data distributed technologies have been proposed and implemented [3, 4]. With the emergence and proliferation of wireless and mobile networks, there has been a renewed interest in the deployment of mobile technologies in remote metering operations. Incidentally, in many developing countries, however, the analog water meter is still the dominant device and replacing these meters may come with enormous financial challenges. A technique that will make it possible for reconfiguration of the meters to ISSN : Vol. 4 No.07 July

2 take advantage of the popular GSM/GPRS (global system for mobile communications/general packet radio service) platform to send and receive SMS will improve on the automation level of water service delivery. Various attempts have been made over the past few years on the use of mobile technologies for remotely reading meter data and operation [6-11]. In the work of Ma et al, [7], a digital water metering system using Zigbee wireless communication protocol was implemented for remote acquisition of user water consumption data. The system architecture used was based on a centralized system (network of meters) before transferring the data to the central database for billing. One of the challenges of the central system however, is the fact that the concentrator that collects the data reading from all the meters in the network and processes it needs a pool of the communication devices for parallel access to the meters, which does not scale quite well especially when many meters to read regularly. The work of Ma et al was further enhanced by the work of Li Quan-Xi et al [8] through the addition of a GPRS technology to the Zigbee. The system architecture that was employed here also involved the use of remote terminals and a collection center, and the user consumption data were transported to the billing house using GPRS. The GPRS technology is useful for meters that need to transmit a lot of data. In this work, we present the design process and prototype development for the automation of an analog water meter to a digital equivalent to facilitate user water consumption access and payment system. We propose to use a combination of the GPRS/GSM and the SMS technology for direct communication of the meter data to the central access database for the billing. The study also employs a photo-encoding technique to compute the amount of water consumption rather than the Hall-effect flow sensor that has been employed in most of the studies conducted. The advantage of the photo-encoding technique lies in its higher resolution or ability to transfer more bits per second compared with the Hall-effect flow sensor. The proposed system will bring benefits to both the users and the water utility in terms of improved water resource management, reducing the cost of meter reading, regulation of the meter in the event of a user exhausting available credit facility stored on the system, and regular monitoring to detect error and tampering among others. 2. System architecture The architecture of the proposed design of the water metering system is presented in Figure 1. The design consists of three principal components: regulated power supply system; a meter interface module that consists of a photo-encoder, microcontroller, and GSM circuitry to allow data transfer to-and-from the interface module; a consolidation server (CS) system which consists of SMS gateway, database server (voucher records, billing, and user account), and application system that consists of billing, payment, voucher generator, and alarm and mapping interface. The water flow captured by the photo-encoder on the meter interface is transferred to the microcontroller which in turn sends the data to the CS via SMS. The CS running the data management system generates the user billing record using a pre-coded tariff structure to compute the consumption. A request for consumption and billing information is accessed via the SMS gateway of the CS system. To effect payment, a user sends a voucher code together with the meter ID and password via SMS to the CS system which upon authentication, proceeds to confirm acceptance of payment by issuing an acknowledgment. To regulate water usage on the basis of credit availability on the system, a solenoid control technology was used. If an available credit is identified as inadequate or exhausted, a signal is initiated that energizes the solenoid to shut the system. In the event of detection of meter tampering or malfunction, an SMS is automatically generated and sent to the CS, which in turn triggers a tamper alarm and a plot of the location is initiated on a mapping system with the corresponding GPS coordinates. The Google mapping API was used for this study. ISSN : Vol. 4 No.07 July

Figure 1: Hardware architectural view of the water metering system 2.1. Regulated power supply system The power supply circuit required for driving the system was designed using the Proteus simulation suite.

3 Figure 1: Hardware architectural view of the water metering system 2.1. Regulated power supply system The power supply circuit required for driving the system was designed using the Proteus simulation suite. Figure 2 shows the circuit simulation model for the voltage supply required for the meter interface module. The circuit was designed to give an output voltage of 4.5V. The choice for this output value was based on the operating voltage requirements of the hardware components used for the prototype development: microcontroller voltage: V, photo-encoder voltage: 5V ± 10% and GSM circuit voltage: 3-4.7V. The equation governing the output of the LM317 voltage regulator may be described by (manufacturer s datasheet) the following equation: V out R2 VREF 1 I ADJ R2 R. (1) 1 In the above equation, R 1 and R 2 are dividing resistors, V REF is a constant voltage across one of the dividing resistors with a typical value of 1.25V, and I ADJ is the adjusting terminal current which is typically considered negligible - 50μA. To ensure good voltage regulation and also reduce the level of noise in the output voltage in the analog environment, coupling capacitors C1 to C4 were included in the power circuit model. To achieve the output voltage of 4.5V, the following component values were determined for the circuit model: V IN - 9V, R1-180Ω, R2-470Ω, C1-0.1μF, C2-10nF, C3-1000μF, and C4-10nF. Figure 2: Proteus circuit model for the regulated power supply system ISSN : Vol. 4 No.07 July

2.2. Meter interface system The meter interface circuitry has three major integrated systems: the photo-encoder, microcontroller, and the GSM circuitry.

4 2.2. Meter interface system The meter interface circuitry has three major integrated systems: the photo-encoder, microcontroller, and the GSM circuitry. The photo encoder system, which is the front-end unit, converts the flow of water through the meter into representative electrical pulses that are processed, manipulated, stored, and transmitted. As the water flows through the meter, the impeller rotates and with the aid of patterned disks, light source, and photosensitive elements embodied in the device, the volume flow information is derived and converted into electrical pulses. For this study, a single-turn photo-encoder with word length of 10 bits per revolution was used. To create a model of this, the photo-encoder device was first connected in circuit and its characteristic waveform pattern was acquired. This pattern which was observed as square waveform with short or long period depending on the rate of flow of water was modeled in Proteus and interfaced to the microcontroller model for processing as depicted in Figure 3 below. The microcontroller converts the photo-encoder electrical signal into numerical representation of the water flow reading through the meter, which is stored in the EEPROM and made available to the CS system as required. The PIC18F2423 microcontroller with the following basic features was used for the simulation due to the availability of the device for the prototype: 0-40MHz operating frequency, 12-bit ADC with 8192 word, 16Kbytes flash program memory, 768bytes data memory, and serial (SSP and USART) communication peripheral. The microcontroller was also configured to check events such as meter errors or defects, battery condition, and tampering and send the notification message to the CS via SMS as and when such events occur. Figure 4 shows the flow diagram of the microcontroller operation. Figure 3: Proteus circuitry for the photo-encoder signal and microcontroller system To facilitate data transmission to and from the CS system, the microcontroller was interfaced to a GSM board, which was modeled as a virtual terminal in Proteus. Figure 5 shows a simulation of SMS data transmission from the water meter to the CS system via the GSM board. The microcontroller sends the SMS data using the UART, which is initialized using baud rate. The Port RB0 of the microcontroller was used as an interrupt initiator to detect only high values or voltage level of the waveform. With the detection of a high value, the system computes the volumetric equivalent of the signal received. Anytime a meter request is received from the CS, the microcontroller sends an AT command to the GSM board. For example, a command such as AT+CMGR=1, corresponds to reading of a message from location 1 of the inbox of the GSM. ISSN : Vol. 4 No.07 July

5 Figure 4: Microcontroller flow operation 2.3. Consolidation server system The architecture for the CS system implemented is shown in Figure 5. The CS system has three main interface elements comprising an SMS gateway, application system software, and a database server. With the CS gateway, two forms of data communication systems were implemented as shown in Figure 1 above: in-bound and out-bound. The in-bound involves the inter-communication between the microcontroller and the CS without any external request from an end-user. The microcontroller initiates communication with the CS based on a precoded schedule for such activity. This schedule is dependent on the how often the water utility house wants such request to be implemented. For this work, data transfer on consumption from the microcontroller to the CS system was scheduled to take once a week (four times) in a month for bill processing. In the event of meter tampering or malfunction, the microcontroller was scheduled to initiate an alarm signal to the CS for review and subsequent issuing of notification signal to the integrated application system for the requisite action. With the out-bound communication, the CS initiates communication as a result of response to query by an end-user seeking for information. The current system supports real-time cumulative consumption data only for any period within a month and also only one historical monthly record. Charges for consumption are only computed on monthly basis. Figure 6 shows a simulation model of the SMS data transmission from the microcontroller to the CS gateway for the case of SMS transmission arising from tampering detection. ISSN : Vol. 4 No.07 July

6 Figure 5: Architecture of the CS system 2.4. Application system The data collected on consumption is sent to the billing table of the database where it is stored. The application system was developed using the visual studio.net. The system serves as an intermediary and it controls the CS by invoking the required applications. To handle users request on consumption data, billing, payment or control operations the sequence diagram in Figure 7 was implemented. The application system issues scheduled monthly information to users via SMS with content such as volume consumed, the bill, and any payments made covering the month and date as well as available credit. The rate structure used for the bill development was based on the tariff structure of the water utility in Ghana. To provide security in the transaction process, a user is required to register the meter ID and password. These are used to authenticate the user anytime an SMS request is submitted to the CS for processing. For example, a user seeking to make payment is required to submit a voucher code together with the meter ID to CS. The voucher generator system decodes the voucher to confirm the amount involved, which is then followed by authentication of the meter ID before the transaction is concluded. With regards to general access to information, a user is required to provide the meter ID and password for authentication before access is granted to the user. A mechanism that controls the operation of the meter device in the event of unavailable credit facility was incorporated in the design. Following detection of unavailable user credit facility on the system, the billing system is scheduled to generate a signal that stops the water flow automatically through the control of a solenoid. ISSN : Vol. 4 No.07 July

7 Figure 6: Proteus model of SMS data transactions with the CS and the Microcontroller 3. Prototype development and testing Figure 7: Sequence diagram for data billing and payment operation To implement the prototype system, an existing analog water meter and off-the shelf components were used as shown in Figure 8. The photo-encoder was integrated to the impellor of the water meter to measure the volume of water through the meter in the form of electronic signals. The photo-encoder used was the Hamamatsu P6921 photo-interrupter device with a high-power infra-red LED and a photo IC. The encoder has input voltage of 3V - 5V and power of 80mW. The signal from the photo-encoder was integrated to the microcontroller for processing and transmission. The microcontroller used was PIC18F2423 with voltage range of 2-5.5V, run mode current of 11μA, and crystal frequency of 0-40MHz. The microcontroller output was interfaced to the GSM board to facilitate data transmission. The GSM board used was from the Samsung SGH 330 mobile phone with input voltage of 3.7V, current of 800mA, and power rating of 29mW. The GSM board was connected to the meter circuit. The meter interface system was powered using a 9V battery which was regulated to give an output of 4.5V. The system was tested for performance and response time as well as other functionalities such as billing and data management applications. ISSN : Vol. 4 No.07 July

8 Figure 8: Prototype development of the metering system 4. Results and discussion To validate the functionality of the prototype, an SMS was first generated and sent from the application system to the microcontroller to request for user meter reading of consumption and billing information and a response on the volume of water consumed in cubic meters and bill were received. This was followed by an SMS query from a mobile phone to access data from the meter via CS gateway. The requested information was received on the phone to confirm the functionality of the system. During the testing phase the average time of 16 seconds round trip was recorded from the time of SMS request to the CS for meter reading request and back to the user. Bulk of the time (over 90%) was used for the SMS transmission on the GSM network. The worst case time that was recorded for the SMS transmission to the CS was 6 seconds whilst the best case time recorded was 3 seconds for the SMS transmission. This gave a total round trip time of 24 seconds and 12 seconds respectively. It is clear therefore that if the state and health of the GSM network is good, the time demand may be reduced significantly and the operational performance may be improved. The system was also tested against tampering, malfunction, error in meter reading, and battery condition such as inadequate battery power. The Google Map API was used to plot the location of the testing device and the nature of the problem encountered. Figure 9 shows a sample map indicating location of a meter device that was tampered by the end-user. The case of low power supply (battery) to the system was also detected especially as the system was left to operate over a long time due to the continuous testing and the alarm system was able to detect this problem. Much as the prototype produced expected results and also the application system deployment to satisfactory level, it was however, difficult to examine the complexities associated with handling of congestion from multiusers since only one meter was practically deployed for the test. This was however tested at the application system level and it produced good results due to the multi-threading algorithm that was implemented. Another challenge is the duration of the power source or battery power. Since power supply is very critical to the smooth operation of the system, it is important that the battery power should be capable of serving the life time of meter. To determine the power requirement, an average power consumption based on the average power consumption of the hardware components of the meter interface module (based on specification provided under the prototype development) was estimated using an assumption of 50% time of operation per day (24hrs). To provide sustainable power to the system, possible sources of power supply is under investigation consideration. These include the use of solar power, natural flow of water through the meter or the rotation of the impellor to recharge the battery, and solid state or lithium-based battery. ISSN : Vol. 4 No.07 July

9 Figure 9: Sample meter tamper notification using Google map system 5. Conclusions In this paper, design of reconfiguration of an analog water meter using the photo-encoding detection method and the SMS with GSM/GPRS to enable users to access data and payment has been presented. To demonstrate the functionality of the system, a prototype was developed and tested. Results showed that it is possible for the system to be deployed. This will help minimize the cost of replacing the analog meter with their digital equivalent by carrying out reconfiguration. Further, it will help both end-users and the water utility to take advantage of the prevailing GSM networks to provide value added services. It will enable the users to directly access exactly how much water has been consumed, easy payment system, mechanism to automatically stop the water flow where credit facility stored on the system has been exhausted, and regular monitoring to detect error and tampering to quickly resolve any potential problems that may inconvenience users. Acknowledgments The authors would like to express their gratitude to the Ghana Water Company Limited (Mr. Bediako and Max) for their support through the supply of the analog water meter for the project. The authors are also grateful to the Texas Instruments Inc. (Mr. Ben Sarpong and Tuli Dake) for the supply of the MSP430 microcontroller board for the preliminary works. References [1] Gastouniotis, C. S., Bandeira, N., and Wilson, K. C. (1990): Automated Remote Water Meter Readout System. Patent No [2] Verma, S. P., Lin, K. S. (1989): System for Automatically Reading Utility Meters from a Remote Location. Patent No [3] Ardalan, S. H., Van den Bout, D. E. (2002): Remote Access to Electronic Meters using a TCP/IP Protocol Suite. Patent No. US B1. [4] Carpenter, R. C., Kelley, R., Scoggins, S. M, and Ardalan, S. (2006): Network-enabled extensible metering system. Patent No. US B2. [5] Boaz, J. A. (2007): Automated meter reading system, communication and control, network for automated meter reading, meter data collector program, products and associated methods. Patent No. US B2. [6] Wahab, M., Abdullah, N., Johari, A., and Abdul Kadir, H. (2010): GSM Based Electrical Control System for Smart Home Application. Journal of Convergence Information Technology, Vol. 5, No.1, pp [7] Ma, Y. (2007): Application of SoC ZigBee Technology in Remote Reading Meter system. World Academy of Science, Engineering and Technology, pp 1-3. [8] Quan-Xi, L., and Gang, L. (2010): Design of Remote Automatic Meter Reading System based on ZigBee and GPRS. 3 rd International Symposium on Computer Science and Computational Technology (ISCSCT 10), China, pp [9] Hallal, H., Haidar, M., Barake, T., AlKhaldi, S., AlOrayfij, M., AlBalawi, A., and Aljehani, R. (2007). GSM-based Embedded Water Meter System. Fahad Bin Sultan University, PP. 1-3, [10] Yunpeng, L., and Chen, Y, (2011). Based on GSM network of intelligent telemetry water system. International Conference on Electronics and Optoelectronics, pp. V2-220 V [11] Abdollahi, A., Dehghani, M., and Zamanzadeh, N. (2007). SMS-based reconfigurable automatic meter reading system. IEEE International Conference on Control Applications, pp ISSN : Vol. 4 No.07 July

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