Design of Gsm Based Power Management

Monitoring of power has been a neglected area in developing countries particularly, Nigeria. Most of these developing countries have always been facing the problem of irregular power supply not because they do not have the capacity to generate the required electricity supply but failure to manage or monitor power consumption by their appliances. The lack of power management result in the development of a GSM based power management system. This system allows monitoring and control power consumption by household appliances.

The GSM technology is well deployed in most developed countries due to its features like easy interfacing with appliances via radio frequency, accessibility at remote area. In this paper, software and hardware were developed. The software allows the user of the system to request for an action from the hardware components. The micro-controller is connected with GSM and relays each of which controls its connected power outlets. GSM – based power management is convenient, more secure, less costly and user – friendly for end user. It is very useful in the area of power management.

Introduction

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Power management has been an area of neglect mostly in the developing nations of the world. Most developing countries have always been batling with the problem of constant power supply not because they do not have the capacity to generate the required electricity supply but because they have failed in their culture of management. Management has been an issue with developing countries. That is the main difference between developed countries and developing countries, Nigeria being a developing country, is not any better.

It is also affected with the poor management virus and power is also part of the things marjoly mismanaged in this part of the world. Timo (2002) researches and studies have shown that Nigeria is one of the blessed countries in terms of natural resources but due to poor management culture we have failed as a nation in harnessing them properly, and for the resources we have harnessed we have refused to gain a total control over them. Often times, people consume power without being made responsible for it.

Responsibility in this sense goes beyond the payment of bills which is being calculated by estimation which is done by the power regulating body the power holding company of Nigeria. In view of this problem, the power holding company of Nigeria which is the power regulating body of the country (Nigeria) tried to curb this power consumption mismanagement issue by introducing an electronic digitized meter which is pre-paid and it is called a pre paid meter. With the introduction of pre-paid meter billing system to consumers, their power consumption have changed and have increased tremendously.

The billing system have became outrageous so there has been an issue of how to manage power by a household in order to be able to consume a specific amount of power so that bills will be strictly based on the amount of power consumed. Limitation This design is only implemented for a home that does not consume more than 200w of power. It has been designed to accommodate only four appliances whose sum total of power rating must not exceed 200w GSM Technology As mentioned by Timo (2002), GSM is widely deployed and is a growing technology supporting a number of new applications being used for it.

GSM is a digital cellular radio system that operates on two frequency bands 900 and 1800MHz. It is a European standard but now has been globally accepted, that reduces the cost of manufacturing and increases the market target. Standardizations are still evolving and so far they have had up to two phases: 1 and 2. (GSM Technical Specification, 2007) This evolution has achieved higher operational boundaries to what was expected at the birth of the technology. Some of the excepted features of the system are: High audio quality and integrating. High level of security preventing fraud and boasting confidentiality. -International and intersystem roaming. -Low cost infrastructure and interpretability with existing infrastructure. GSM Architecture A GSM system as defined could be thought of as a combination of three subsystems: Base station subsystem (BSS), Network subsystem and operational and maintenance subsystem (Vijay, K. G. , and Joseph, E. W. 2009). Base station subsystem is a radio link subsystem and is responsible for management of connection including handovers of calls from coverage area (cell) to cell.

BSS is formed by a combination of mobile set (MS), Base Transceiver Station (BTS) and Base Station Controller (BSC) several BTSs are connected and controlled by a single BSC. This single BSC is responsible for handover, radio link control and power control for transmission. ‘The network subsystem is the core of the GSM system. It controls mobility, switching and management of the subscriber. It consist of switching centre (MSC), Visitor Location Register (VLR), Home Location Register (HLR),Authentication Centre (AUC), and Equipment Identity Register (EIR).

One MSC is communicating with number of BSCs, and therefore it is used for call setup, routing and handover between the two subsystems. Also for billing purposes MSC is in control’. (Siegmund, M. R. Matthins, K. W. and Malcolm W. O. 2005). The four data bases for control and network management are AUC, EIR, HLR, and VLR; they operate almost the same way. HLR is a database for mobile sets registered to a particular mobile network. And a MS is registered to only one HLR even if the network has many HLRs. This database is usually combined with the AUC. Together they are responsible for service profile and routine information.

AUC verifies authenticity of the subscriber and provides the HLR with ciphering information for mobile transportation. VLR is usually combined with MSC and called MSC/VLR, provides location information to the servicing MSC. This is a database of all roaming MS in a particular MSC, and database is updated as soon as a mobile set leaves the MSC. The HLR is notified of where the MS is, so that all the calls to that particular MS are re-routed correctly. This does not mean VLR cannot control call setup by itself, it has all the needed information and it acts like a moving HLR.

EIR is a database that stores the identity of each MS. Each MS has a unique identifier called identity mobile equipment identity (IMEI). This database can be used to stop giving service to a stolen set. The operation and maintenance (OMC) subsystem is responsible for maintenance of the entire network and GSM equipment, therefore it needs to be connected to all equipment in the BSC and switching system. Also, communication with these equipment should be guaranteed so that at all times it can monitor and update the entire system.

According to English, J. , Fielding, E. , and Howard, N. (2002), the network used to communicate is different from the one subscribers are using; usually a fixed signaling network is used such as SS7, GSM network has also an optional part called short message service center (SMSC). This was developed after the realization that not only voice communication can be offered through network but also short message and data can be transmitted. Peter, H. A. (2007) defined short message as a message of less than or equal to 150 characters.

The SMSC stores the sent messages until it can find the destination addressed in the message. The period of storing a message is dependent on the service provider. Fig 1 Overview of GSM architecture; Asha, M. (2006) Software Basically the response of the micro-controller to the signal or message from the GSM is being controlled through a program written in micro-basic which hardwired on the micro-controller. The user interface which allows the user to select appliance(s) to be turned OFF or ON was designed and coded in visual basic 6 languages.

The choice of visual basic was due to its flexibility. This program communicates with the micro-controller by sending the option of the user (i. e. to turn on or off) through the one the messages from the monitoring phones to the micro-controller of which in turn effects the necessary action. The program was written in such a manner that the phone might require an administrator, which users’ personal can turn off appliances on which output he so desires to turn off at a particular point in time or allows automatically switches off appliances on ports according to priority.

HardwareThis involves arrangement of several components which are integrated together to form a circuitry device that performs a function switching off and on ports which serves power to the following appliances. Working Operation of the Model The following are the components that constitute the block diagram of the model Fig. 2. Block Diagram of the Model Step-Down Transformer. Power is fed into the circuit through the mains and is step-down to 12v which is the required voltage for the circuit. This is rectified using device and also filtered with the aid of a filtering capacitor.

The essence of this is to convert the AC voltage from the mains to DC voltage because the micro-controller is powered by a DC source. The micro-controller requires just 5v to power, so the 12v is attempted using resistors (potential divider).

Voltage Transformer

This is used in measuring the voltage flowing through the appliance and is rectified using half-wave rectification and also filtered using a capacitor. The input impedance from the analogue signal must not be higher than 2km, the buffer amplifier is used to achieve this purpose. It has unity gain amplifier to ensure input is replicated at the output. The buffer amplifier consists of operational amplifier.

Current Transformer

This provides isolation and also steps down current. In practice, it is difficult to find a current transformer, so we made the primary side of a voltage transformer to function as the secondary thereby making it work as current transformer. The analogue to digital circuit in the micro-controllers needs analogue voltage and not current, the current flowing is made to pass over a resistor to give a voltage that is proportional to the current flowing. This resistor is called the shunt resistor and should be as low as possible.

This voltage measured is later converted to current through the aid of the code. Micro-Controller The micro-controller used here is the PIC16F877A type. It provides the following in the functions in the model.  Digitization of both the current and voltage measured and the resultant power. Multiplication of the measured parameters (current and voltage) to give power the current and voltage measure is fed into the micro-controller where the multiplier circuit embedded in it multiplies them to obtain power. Conversion of binary digitals to BCD. The binary digits coming as output from the multiplier needs to be converted to BCD.

The power that is being calculated is sent phone, and the program picks this up and compares it if it is within the limit of the power consumption that is allowed. If it is more than the limit, the administrators can switch off which ever appliance that is of lower priority to him or her. The phone might be put on automatic, which on its own turns off appliance based on its order of priority. Relay Switches When the computer does the comparison, it then sends a request back to the controller which in turn excites the relay that controls the appliance to be controlled, either to be turned OFF or ON.

Seven Segment Display The BCD generated by the micro controller will be displayed on the seven segment display which eradicates the need for a seven segment decoder and its driver. Radio Frequency Communication between the phone and the microprocessor is achieved by radio frequency technology used by the GSM. Initial Testing and Setting of the Model The monitoring phone must be configured with the application used and it must support it. The application configured onto the GSM has a default number which will be allowed to communicate with the micro-controller.

All the four appliances were set to OFF initially before they were being controlled by the GSM through the following steps. ? Go to the application from the mobile phone. Then mobile control menu from the application. Select mark or check on the appliance you wish to turn on. Software Implementation The operational implementation of the system is in software, meaning; its control is software based. The processor is programmed to be in continuous polling mode, meaning its operation is not triggered by an interrupt but rather continuously executing the code as long as it is powered.

This kind of operation may be costly for non critical kinds of communication but good for real – time communication. As mentioned earlier that the starting of the system operation is when the GSM reads the message through reading RS232 port at the decided band rate, and convert it to BCD which the micro-controller understands. Hardware Implementation The implementation of hardware begins with the message received by the GSM phone which later converted to a BCD in form of tone and sent to the micro-controller. Microcontrollers in turn send signals to the relays to witch OFF or ON the particular appliances as the case may be. Sending Message to the Mobile Station Message could be sent to check the status and control the appliances from any other configured GSM paired with the base phone (i. e. connected with the circuit) Checking of the Status. To check for the status of the appliances from any distance, the steps to follow are the following: Open the contact option from the phone application. Go to the GSM contact to change destination number to defaulted number. Then go to appliance control.

The status of the appliances will be automatically sent back to the GSM. Control of the Appliances from the Remote Area. The following steps must be followed when controlling the appliances: Open the contact option from the GSM application. Go to the GSM contact to change destination number to the defaulted number.  Then go to appliance control. Type the request message using the format *MWM* appliance number* action ON (1) or OFF (0) * acknowledgement# ? Press send. Performance of the Model The model built was tested by connecting four appliances whose sum total of power consumption was not more than 200w.

The system worked perfectly well. Also we set the range of power consumption to 150w, this indicates that whenever appliances are connected to it and their sum total power consumption is more than 150w, then the user turns off any of the appliances or the system automatically turns it off or on. Conclusion and Recommendations From the design and the implementation of the system presented in this document, it can be concluded that GSM system could solve many of the challenges most developing countries are facing particularly the problem of misuse of power supply.

Because of the flexibility and ease of the system design, GSM system could be adapted for any application ranging from control of appliances to monitoring remotely. Also, the high level of security of the GSM network is an advantage for securing data transmission; therefore this system should be implemented without fear of eavesdroppers for future this system can solve many technological challenges, for example a company manager could use his GSM set anywhere in the world and log data to his system allowing him to monitor power consumption in semi-real time to reduce cost.

The system could be used in manufacturing industry, for example to monitor the consumption of power used by each equipment used for production thereby useful for cost benefit measurement. There are number of applications that could be developed with the system, and for further security measures, the system could be developed such that it connects to severance cameras, allowing the user to visually see his assets at anytime, anywhere. Also, it would be nice to develop the system such that it can convert the message into voice so as to accommodate blind users. As mentioned earlier that this system is not complex to assemble, and the fact that the GSM technology is everywhere means it can be sold at an affordable price.

References

1. Asha, M. (2006) GSM System Engineering. New York: Artech House. Charles, R. K.
2. Morris, M. (2001) Logic And Computer Design Fundamentals. London: Prentice Hall. English, J. Fielding, E.
3. Howard, N (2002) Professional Communication 5th Edition Maidenhead; Open University Press. GSM Technical
4. Specification(2007) Digital Cellular Telecommunications System. London: Croom Helm. Peter, H. A. (2007): Pic 16C84 – Outputting To A Serial Device Baltimore: Morgan State University.
5. Siegmund, M. R. , Matthins, K. W. and Malcolm, W. O. (2005) An Introduction to GSM. Boston: Arteer Honge.
6. Timo, H. Javier, R. and Juan Meler. (2002) GSM, GPRS and EDGE Performance. New York: John Wiley and sons.
7. Vijay, K. G. Joseph, E. W (2009) Principles and Applications of GSM. London: Prentice Hall.

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