Water Management System Using Solar Powered AC Motor

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                                 ABSTRACT

The conventional energy supplied by the electricity department is not able to meet the demand and because of the power deficiency people are accepting power cuts. Particularly at domestic side the consumers are facing many problems because of frequent power cuts, to avoid this problem alternative source is essential. Solar energy is one of the best alternative sources of energy. In this regard this project work is taken up, which is aimed to utilize solar energy for driving the pumps. The Solar Power System designed with power MOSFETS and PWM chip is aimed to utilize solar energy, by which any low power domestic electrical appliance can be operated when required.

The main intention of this project work is to run a low rating AC water pumping motor without main (conventional) power. The solar panel used in the project work is 20 watts and can deliver a maximum voltage of 18V and a current of 1.5 amps under the bright Sun light. And this energy is used for charging the battery; here a heavy-duty battery of 12V/14 AH is used for operating the AC water pumping motor. This stored water can be distributed for household, irrigation purpose, hospitals etc., using a distribution channel.

The project is designed to deliver 220V AC from 12V DC source availed from the battery. For this purpose high power rechargeable battery is used as a back-up source, there by the system can be used to drive the load when required.In this regard,the power system is designed to drive 60 to 80 Watt loads. This power system is quite useful for remote areas, where the availability of main power is critical.

The demonstration module consists of a heavy-duty battery, solar panel, charge control circuit, inverter, water pumping motor, distribution channel etc. For demonstration the proto type module is constructed with low rating components and for real applications these have to be upgraded.

CONTENTS

Description        Page No

 

Certificate          iii

Acknowledgements        iv

Abstract          v

List of Contents         vi

List of Figures         ix
List of Tables         x

 

Chapter

 

  1. Introduction        1

 

  1. Functional Description of Project Work    5
    1. Solar Energy
    2. Battery & It’s Charging Circuit
    3. Dual Inverted Outputs Oscillator
    4. Driver Stage Using Power MOSFETs
    5. Main Output Transformer
    6. Microcontroller
    7. Liquid Crystal Display
    8. Relays
    9. Pumps
  1. Block & Circuit Diagrams      23
    1. Block Diagram
    2. Circuit Diagram
  1. Description of The Power System Operation  26
    1. Integrated PWM Controller
    2. Drive Stage
  1. Non Conventional Sources of Energy-An Overview 37
    1. Non Conventional/Renewable Energy Sources
      1.   Wind Energy
      2.   Bio Energy
      3.   Solar Energy
      4.   Other Sources
    2. Potential & Exploitation of Renewable Energy

Sources

  1. Description of Inverters      42
    1. Uninterruptible Power Drives
    2. Variable Frequency Drives
  1. Description of Power MOSFETs    45
    1. Circuit Symbols
    2. MOSFET Operation
  1. Description of  Microcontrollers    51
    1. Necessity of Microcontrollers
    2. Advantages of Microcontrollers
    3. Architecture of 8051µc
    4. Oscillator & Clock
    5. Types of Memory
      1.   Special Function Registered Memory
    6. I/O Ports
    7. Interrupts
  1.  Description of  Solar Panels     64
    1. Introduction
    2. Photovoltaic Cells
    3. Overview of The Technology
  1.  Relays & Their Applications     68
    1.     Electro-Mechanical Relays
    2.     Solid State Relays
    3.     SSRs Vs EMRs
    4.     Relay Applications
  1.  Description of  LCD Interfacing    73
    1.     Interfacing LCD to the Microcontroller
  1.  Software Description Along With Chip Burning 78

Process

  1.     Chip Burning Process
    1.  C51 ‘C’ Compiler
    2.  KEIL Compiler
  1.  Hardware Details       83
  2.  Conclusions & Future Scope     84

 

References        86

 

Appendix

 

  1. Microcontroller Code     87

LIST OF FIGURES

 

Figure no    Description      Page no

2.1  Interfacing the display unit to the microcontroller  16

3.1  Block Diagram       23

3.2  Circuit Diagram       25

4.1  Building blocks of PWM controller    28

4.2  Corresponding waveforms of PWM    29

4.3   Output waveforms of PWM controller with   32

Ramp/Saw-tooth input

4.4  Circuit diagram of PWM oscillator    33

4.5  MOSFET drive stage circuit diagram    35

7.1  Various circuit symbols of JFETs & MOSFETs  47

7.2  Example application of an N-Channel MOSFET,  48

when the switch is pushed, the LED lights up.

7.3  Cross section of an NMOS without channel    49

formed: OFF state

7.4  Cross section of an NMOS with channel    49

formed: ON state

8.1  PIN diagram of 89C51 IC     56

8.2  Functional block diagram of microcontroller (8051µC) 57

8.3  Oscillator & timing circuit     59

10.1  Electro mechanical Relay (EMR)    69

10.2  Solid State Relay (SSR)      70

11.1  Interfacing the display unit to the microcontroller  73

LIST OF TABLES

Table no.    Description      Page no

2.1   Function of each pin of LCD    17

8.1   Special functions of Port 3 pins (8051µC)  58

8.2   Port 3 alternate uses (8051µC)    62

8.3   Interrupts memory location (8051µC)   63

11.1    Function of each pin of LCD    74

11.2    Instruction Command codes for LCD   76

CHAPTER – 1

INTRODUCTION

As the availability of fossil fuel declines, there is need to find alternate energy sources, of the many sources, solar energy available in abundance and renewable is the ultimate source of all known forms of energy. It is clear, safe, and free, does not pollute the environment and thus will be an extremely viable alternative in the days to come.

One way to utilize the solar energy is to generate electricity directly from the sunlight by photovoltaic conversion. Since photovoltaic modules have now become extensively available in the country. Solar energy has long been regarded as an ideal energy source but for the fact that we knew little to tap or use it to our advantage. The advancement in science and technology brought out by mankind had lead to developments like the photovoltaic cell. Solar panels comprise of a number of such PV Cells. The output of the Solar Panel is proportional to the intensity of incident radiation from the sun.

As the power generated is dependent on incident radiation and also the intensity varies with time and season at a particular point, the efficiency of the fixed system is far less to exploit commercially. For optimum generation of electric power the PV Panels need to be maintained or positioned normal always to the incident radiation. The panel used in the project work can deliver a maximum power of 10 watts under the bright Sun.

Solar energy is increasingly used these days for wide variety of applications, in this regard this project work is considered, which is aimed to design a low cost solar power system for domestic applications. Solar energy, with its virtually infinite potential and free availability, represents a non-polluting and endless or inexhaustible energy source which can be developed to meet the energy needs of mankind in a major way. The high cost, fast depleting fossil fuels and the public concern about the eco-friendly power generation of power have led to a surge of interest in the utilization of solar energy. To evaluate the energy potential at particular place, detailed information on its availability is essential. These include data on solar intensity, spectrum, incident angle and cloudiness as a function of time.

Presently the panel manufacturers are offering 15 years life to their panels; few of them are claiming that their panels can work up to 20 years. So validation of the panel is important by comparison of different technologies. Panels must be tested perfectly before they install, for this reason proper testing equipment & methods are essential for various reasons. One main reason is to measure the working power at different conditions. The solar panel testing should be done close to the operating conditions. The measurement system can be designed to determine the electrical parameters of a PV cell. The main function of the solar panel is to utilize the solar energy by generating electricity directly from the sunlight by photovoltaic conversion.

Importance of non-conventional sources of energy:

1. The non-conventional sources of energy are abundant in nature. According to energy experts the non-conventional energy potential of India is estimated at about 95,000 MW.

2. These are renewable resources. The non-conventional sources of energy can be renewed with minimum effort and money.

3. Non-conventional sources of energy are pollution-free and eco-friendly

Now coming to the project work, In order to generate 230V ac from 12V battery for the inverter application, the best method of inverter with higher efficiency technique is to be evolved which shall be high efficient, less power consumption, easy interface, and modular design. For this purpose an IC 3524 based (pulse width modulator) circuit is designed which can work on a 12V sealed maintenance free battery there by it can provide an uninterruptible power supply. The main function of this power system is to provide power to the low power home appliances like fan, TV, light, etc., because the power system designed here can generate less power. By these three non-conventional sources of energy, the battery gets charged and the appliance will be energized when required.

Initially the ac pulses at 50Hz in the form of square waves are generated from the inverter chip; this device generates dual inverted outputs. The output of the oscillator is amplified in terms of voltage and current, the drive circuit is designed with power MOSFETs and main output transformer is configured as push-pull amplifier. With the help of a duty cycle control circuit interfaced with SG3524 chip, the output voltage is can be controlled linearly.

The solar panel used in this project work generates unregulated output, this voltage as it is cannot be used to charge the battery, this panel generates the maximum voltage of 18V under the bright Sun and if the battery is charged with this voltage it may spoil due to excess voltage charging. There by the panel output is regulated and the battery is charged with a constant voltage source of 13.5V. The energy stored in the battery is used to operate the water pump motors depending on the input given through the controller.

In India the water is distributed in regions on time basis e.g. a specific area get water daily only between 3pm to 5pm and then in adjoining area the water is provided between 5pm to 7pm, etc.  This process is done manually where a person goes in that area and turns ON/OFF the valve manually. This is a very tedious and time consuming process. Moreover these valves are not locked and can be easily turned ON/OFF by a common man thereby wasting lot of water. Looking at all these problems we decided to make a circuit which will help in minimizing the water loss, fuel, greater timing precision by not depending on humans to turn ON/OFF the valve.

So here concept of water management is practically shown in a demo module where we can control water distribution in 2 areas. In this we will be using a simple 8051 based microcontroller along with the help of relays and pumps we will control the timings at which we have to provide water in specific area. Two keys are used to set two different timings for the individual water pumping motors. Using relays we will be controlling valves/pumps and provide water supply to corresponding areas.

The control system is designed with 89C51 microcontroller, this is an 8 bit controller and it is the most popular chip in use today. Eight bits have proven to be a very useful word size to develop controller based projects. The controller based projects often they are called embedded systems; because the controller is having processor inside, a processor is an important unit in the embedded system hardware. A microcontroller is an integrated chip that has the processor, memory and other important architecture like ROM, RAM, inputs and outputs, timers, counters, registers, oscillator, etc. With these facilities, the device can be called as single chip computer, popularly known as a Computer on chip. The detailed description of this microcontroller is provided in the later chapters.

CHAPTER – 2

Functional Description of the Project Work

The functional description of the project work is explained in this chapter. For better understanding, the total project work is divided into various blocks and each block explanation is provided here. The complete block and circuit diagrams of this project work are provided at the end of this chapter. The following is the description of overall function of the project.

2.1 Solar Energy

Solar power is the conversion of sunlight into electricity, either directly using photovoltaic’s (PV), or indirectly using concentrated solar power (CSP). Photovoltaic’s convert light into electric current using the photoelectric effect. The solar panel used in this project work is rated for 0.8 Amps; it generates a maximum power of 10 watts under the bright sun. Solar panels consisting of photo voltaic (PV) cells convert the solar energy in to electrical energy. The electrical energy produced by the solar panel is stored in the battery, and the stored energy is used to drive the load through power system. This is the main function of the power system.

The most useful way of harnessing solar energy is by directly converting it into electricity by means of solar photovoltaic cells. When sunshine is incident on solar cells, they generate DC electricity without the involvement of any mechanical generators, i.e. in this system of energy conversion there is direct conversion of solar radiation into electricity. The photovoltaic effect is defined as the generation of an electromotive force as a result of the absorption of ionizing radiation. Energy conversion devices, which are used to convert sunlight to electricity by the use of the photovoltaic effect, are called solar cells.

The solar panel used in this project work is designed to deliver a maximum voltage of 18 under the bright Sun; this is known as no load voltage, when it is loaded, the voltage may fall down according to the load applied to the panel. As per the ratings specified by the panel manufacturer, when a 10 watts load is connected across the panel terminals, then the voltage may fall down by less than 13V. This voltage varies according to the load applied to the panel. As the battery consumes total power when it is in discharge condition and though the panel output is regulated, the voltage may fall down by less than 13V, as the battery is charging slowly, the terminal voltage level boosts and the charging current will be reduced gradually. As the charging current is reduced, battery terminal voltage will be increased, and this voltage reaches to a maximum level of 13.5V, because panel output is regulated by 13.5V. As the panel output will not exceed beyond 13.5V, the battery will be charged with this constant voltage.

As described above, the panel voltage is not stable, it varies based on many factors, the first reason is availability of solar energy, this is the input source to the solar panel and it is varied, accordingly panel output also varies. The second reason is that the panel voltage varies according to the load applied to it. Based on these two reasons, the panel output as it is cannot be used for charging. Therefore here using a charge control circuit, panel output is regulated at 13.5V i.e., under any condition (though the panel is exposed to the bright Sun) the panel final output voltage will not exceed more than 13.5V. This regulated source is used to charge the battery. As the battery is charged with constant voltage source, the life of the battery can be increased.

2.2 Battery & its charging circuit

The battery used in the project work is rated for 7Ah at 12V; this is a maintenance free type rechargeable battery generally called as secondary cell. A battery is rated in terms of the discharge current, it can supply continuously for a specified interval of time. The output voltage should remain constant at a minimum level of rating over the entire period of time. The current rating depends up on the size and surface area of the electrodes. Current rating varies in the case of a lead-acid battery; in general a battery cell with a high ampere-hour capacity is called as heavy duty battery.

Since low power panel is used, the battery will take lot of time to charge fully. As the panel generates 0.8 Amps under bright sun, the charging time is defined as, battery rating, i.e. 7AH / charging current, i.e. 1 Amp (approx.) = 7 hours approximately. If the battery is charged with high power panel, charging time can be reduced. As the solar power is un-stable, the panel may not produce continuous output, the power output may vary incidentally, thereby average power will be always less than the rating. There by it is recommended to use high power panels for charging the higher rating batteries.

When compared with power system configurations, the battery used in the demo module can be said as low power battery, in general high power inverters contains high power batteries of 60 Ah and above ratings are preferred for long back-up time. Though the panel is unable to generate energy continuously for a period of 3 to 4 days, the battery should able to generate required power. Accordingly the battery back-up time must be calculated & implemented.

The battery back-up time can be defined as battery rating / consumed energy by the power system. The power system designed here generates 0.3Amps at 220V output, i.e. the power output is 66Watts approximately. When the system is connected with 0.3A load, then the system may consume nearly 6.5 Amps from the battery, this is the input power. According to the energy consumed from the battery, the input power is defined as 78 watts. Therefore the power system efficiency is defined as 84.6%. When average power of battery is considered as 6.5Ah, the back time will be 1 hour approximately. During utilization of battery power (in absence of main power), if panel is also producing energy then back-up time will be increased slightly. For example, if a higher rating panel is used, which can generate more than 6.5 amps, irrespective of battery power, the power system consumes energy directly from the panel.

The battery is charged with constant voltage charger, this circuit is designed with 7815 three terminal voltage regulator chip, as the regulator itself can not generate sufficient current, with the help of a power transistor configured as series pass regulator, energy produced by the panel is supplied to the battery at constant voltage. The output of the voltage regulator is applied to the transistor base; the final output is taken from transistor emitter. The regulator establishes the base voltage for the transistor, this voltage is stabilized at 15V, but the voltage at the emitter will be about 0.7V less, and the difference will become grater as the load current increases. In addition to the above loss, as this circuit contains power diode connected in series with the charging circuit to prevent from flow of reverse current, another 0.7V drop will be occurred across the diode junction. After estimating these losses approximately, it is concluded that the charging circuit is generating nearly 13.5V, means finally the voltage applied to the battery will be 13.5V. If the battery is fully discharged, then it will consume more power from the panel, in this condition the voltage may fall down by less than 12V. As the battery is getting charged, the voltage level will be boosted slowly. Once the battery is charged fully, the battery terminal voltage will become equal to the charger voltage, when both levels are equal; battery will not consume energy from the panel. As the panel generates very less energy of 0.8Amps, & where as the transistor can withstand up to 8 Amps, heat sink is not required. The regulator used here can generate sufficient base current, there by the transistor allows maximum load current through its junction, i.e. between collector and emitter.

The battery used in this project work is known as lead acid type of rechargeable battery, these batteries are supposed to be charged with constant voltage chargers. During charging condition, though the battery is fully charged, the battery terminal voltage should not exceed more than 13.5V, otherwise it may damage due to the excess voltage charging.

The power ‘P’ produced by the panel can be calculated easily, initially the battery that consumes energy from the panel for storing in to it is denoted as product of the voltage & current (E & I). Thus P = E X I watts, if E is in volts and I in amperes, and the voltage across the battery terminals can be measured with a volt meter, similarly current can be measured with an ammeter connected in series with the load. Finally the power is calculated in watts by multiplying voltage & currents produced by the panel. If the value of the load resistance (battery terminal resistance) RL is known in ohms, power in watts can also be calculated by use of the formula P = I2 RL or P = E2 / RL.

The power system designed with power MOSFETs is aimed to generate 230V ac from 12 V dc, since it is a prototype module a low power system is designed which can deliver a maximum power of around 70Watts. Since the system consumes more power, the output of the panel is not sufficient to drive the system directly. Therefore stored energy is used to energize the load when required. The following is the description of basic oscillator of the power system that generates 50Hz ac signal in dual inverted output.

2.3 Dual inverted outputs Oscillator

The oscillator circuit designed with 3524 chip can generate inverted square pulses at two different output pins of the IC. Based on this signal, the drive stage is configured in push-pull mode of operation. This circuit consisting of two power MOSFETs switches the transformer alternatively; there by continuous output can be obtained from the transformer secondary. The advantage of generating dual inverted outputs is that the transformer primary remains in energized condition continuously. As this transformer primary is having centre tap, it is divided in to two equal sections, and both sections are energized continuously one after another. In this regard switching losses can be minimized.

The output voltage of the single-phase inverter is roughly square wave and it can be controlled by means of pulse width Modulation. PWM technique is a control within the inverter and is also known as variable duty cycle regulation. This method of regulation employs variation of the conduction time per cycle to alter the RMS output voltage of the inverter. PWM oscillator is constructed using IC 3524. It consists of built in oscillator, comparators, error amplifiers and output control circuitry. In this IC, a 5V internal regulator is also provided. Internally, for the comparators one input is fed with a saw-tooth voltage and the other input is fed with a feedback monitoring voltage. As this inverter is configured in open loop operation PWM technique is not implemented here, there by output voltage is not regulated. The output voltage will be varied according to the load applied to the inverter. In our trail runs we found that the power system generates around 240V in no load condition, when the system is connected with rated load of around 70 watts, the voltage is fallen down by 220V.

The oscillator operates at a fixed frequency that is programmed by one timing resistor, RT and one timing capacitor, C; RT establishes a constant charging current for C. This results in a linear voltage ramp at C, which is fed to the comparator, providing linear control of the output pulse duration (width) by the error amplifier. The IC on board 5V regulator that serves as a reference, as well as supplying the internal regulator control circuitry. The internal reference voltage is divided externally by a resistor ladder network to provide a reference within the common mode range of the error amplifier. The output is sensed by a second resistor divider network and the error signal is amplified. This voltage is then compared to the linear ramp at C. The resulting modulated pulse out of the high-gain comparator then is steered to the appropriate output pass transistor (Q1 to Q2) by the pulse-steering flip-flop, which is synchronously toggled by the oscillator output.

 

2.4 Driver Stage Using Power MOSFETs

The driver stage designed with power MOSFETs is configured as class ‘B’ mode of push-pull amplifier. The advantage of class ‘B’ push-pull amplifiers are, it provides linear amplification. Apart from that the DC collector current is less than the peak AC current. Thus, less collector dissipation results and the efficiency increases. In the project work, center tapped transformer is used, which supplies two base currents of equal amplitudes but 1800 out of phase. There by in the first half cycle one MOSFET is off and the other MOSFET is conducting. Whereas in the second half cycle other MOSFET is conducting i.e., roles of power MOSFETS are reversed. The current in the conducting MOSFET flows through the upper half of the primary winding and the resulting time varying flux in the transformer core induce a voltage in the secondary winding. The voltage in turn produces the first half cycle of the current through the load. Similarly, when the MOSFET roles are changing, the flux in the transformer core in a direction opposite to the flux of previous half cycle of the load current. The final current of the load under these conditions is thus directly proportional to the signal current.  In practice the load current would be extremely distorted near the zero crossing. This effect is called cross over distortion and is due to Gate-source voltage in MOSFET ‘VGS’ being zero when no signal is applied.  However linear operation of the (transistor) MOSFET begins only when (base) Gate current is positive enough to cross the cut in voltage. To eliminate the distortion base-emitter junction is biased at approximately 0.7V. The result is class ‘AB’ rather than class ‘B’ operation but is very close to class ‘B’ mode. The bias is called the turn-on bias in practice, one often allows cross over distortion and relies on the transformer and internal and stray capacitors to filter it out.

 

2.5 Main Output Transformer                                                  

The main output transformer used in the driver stage is designed to deliver 0.35 amps current at the secondary. This is a step up transformer and the primary of this transformer is designed for 12V. This is a center tapped primary transformer and the primary is wounded with by-filler winding, i.e., the primary is wounded with two copper enamelled wires simultaneously. Starting of the one winding is clubbed with ending of another wire to form a center tap. The advantage of adopting by-filler winding concept at primary side of the transformer is to maintain the accurate balance; there by the current flowing through both sections of primary remains equal.  Detailed description about the power system is provided in the next chapter.

2.6 Micro-Controller

Using the controller, the water pumping motors are controlled independently for water management through the relays. For this two relays are used to control two pumping motors. Through two push buttons connected to the controller, the two pumping motors are controlled for two different timings individually. Micro-controller unit is constructed with ATMEL 89C51 Micro-controller chip. This is a low power, higher performance CMOS 8-bit microcomputer with 4K bytes of flash programmable and erasable read only memory (PEROM).  Its high-density non-volatile memory compatible with standard MCS-51 instruction set makes it a powerful controller that provides highly flexible and cost effective solution to control applications. Since this IC is having 32 I/O lines more hardware can be interfaced with single chip for multiple applications. In this project work, the task is to control the motors depending up on the information generated by the keys.

Low cost high volume products requiring a relatively simple and cheap computer controller have traditionally characterized micro-controllers. The design optimization parameters require careful consideration of architectural tradeoffs, memory design factors, instruction size, memory addressing techniques and other design constraints with respect to area and performance.  Micro-controllers functionality, however, has been tremendously increased in the recent years. Advanced versions of the micro-controller in 16-bit configuration have been introduced for high performance requirements particularly in applications where good arithmetical capabilities are required.  In this project work ATMEL 89C51 micro-controller is used, this is 8-bit micro-controller.

The micro-controller used in this block acts as an embedded system.   Here the micro-controller is getting the digital information from the keyboard and displaying the drill data on LCD panel.   In this project work, the micro-controller performing three important functions i.e., (a) Collecting the digital information from the keyboard and storing the same in ROM (b) displays the digital information. (c) And controlling the motors according to the data produced by keyboard. The program is prepared in assembly language for performing the above three functions.

Micro-controller works according to the program written in it. Most microcontrollers today are based on the Harvard architecture, which clearly defined the four basic components required for an embedded system. These include a CPU core, memory for the program (ROM or Flash memory), memory for data (RAM), one or more timers (customizable ones and watchdog timers), as well as I/O lines to communicate with external peripherals and complementary resources — all this in a single integrated circuit. A microcontroller differs from a general-purpose CPU chip in that the former generally is quite easy to make into a working computer, with a minimum of external support chips. The idea is that the microcontroller will be placed in the device to control, hooked up to power and any information it needs, and that’s that.

For instance, a typical microcontroller will have a built in clock generator and a small amount of RAM and ROM (or EPROM or EEPROM), meaning that to make it work, all that is needed is some control software and a timing crystal (though some even have internal RC clocks). Microcontrollers will also usually have a variety of input/output devices, such as analog-to-digital converters, timers, UARTs or specialized serial communications interfaces like I²C, Serial Peripheral Interface and Controller Area Network. Often these integrated devices can be controlled by specialized processor instructions. Originally, microcontrollers were only programmed in assembly language, or later in C code. Recent microcontrollers integrated with on-chip debug circuit accessed by In-circuit emulator via JTAG (Joint Text Action Group) enables a programmer to debug the software of an embedded system with a debugger.

2.7 Liquid Crystal Display (LCD)

The display section is designed to display the status of the pumping motors. For this purpose an LCD panel is used and is interfaced with microcontroller through its output port. This display is having two rows and each row can display 16 characters.

The LCD panel used in this block interfaced with micro-controller through the output port. This is a 16 character x 2 Line LCD module, depending up on the availability of LCD panel 3 lines or 4 lines panels can be used for the purpose, so that more information can be displayed simultaneously. These panels are capable of display numbers, characters, and graphics. The display contains two internal byte-wide registers, one for commands (RS=0) and the second for characters to be displayed (RS=1). It also contains a user. Programmed RAM area(the character RAM) that can be programmed to generate any desired character that can be formed using a dot matrix. To distinguish between these two data areas, the hex command byte 80 will be used to signify that the display RAM address 00h is chosen.

In this project work, two lines X 16 characters LCD panel is used for displaying the demodulated information. Since the panel contains 2 lines more information can be displayed simultaneously. The LCD contains 16 pins of which 8 are data pins and 3 are control pins. The LCD is interfaced to the Microcontroller using one of its ports. The Microcontroller used in this project work is having 36 I/O lines and 10 I/O lines are interfaced with LCD panel, D0 – D7 of LCD panel are called as 8 – bit data pins and this panel acquires the information from Microcontroller through this data pins. Detailed description about LCD interfacing is provided in chapter – 11, and regarding detailed description of the LCD panels is provided in Chapter –8. The following is the figure shows how the display unit is interfaced to the Microcontroller.

Fig 2.1 Interfacing the display unit to the Microcontroller

As seen from the above figure, Pins from 7 to 14 are data pins used for the selection of a particular character and pins 4 to 6 are Control signal pins used for performing Register bank selection, Read / Write and Enable pins respectively. By adjusting the voltage at pin number 3 we can change the contrast of the display. To display a particular character its associated logic sequence has to be placed on the data pins and write signal (Pin-6) has to be enabled. Microcontroller takes care of all these things based on the program loaded into it. All that we need to do is to depress the desired keys during the text message preparation. The display section is same at the transmitting end as well as at the receiving end. In the receiving end, Microcontroller places the logic sequence on the data pins based on the information obtained from the decoder output.

The LCD panel used in this project work is having 14 pins.   The function of each pin is given in the following table.

Table No: 2.1 Function of each pin of LCD

Pin    Symbol        I/O  Description

1 Vss  —        Ground

2 Vcc  —        +5V Power Supply

3 VEE  —        Power supply to Control Contrast

4 RS   I        RS = 0 to select command register,

RS=1 to select data register

5 R/W   I         R/W =0 for write, R/W=1 for read

6 E  I/O         Enable

7 DB0  I/O        The 8-bit data bus

8 DB1  I/O        The 8-bit data bus

9 DB2  I/O        The 8-bit data bus

10 DB3  I/O        The 8-bit data bus

11 DB4  I/O        The 8-bit data bus

12 DB5  I/O        The 8-bit data bus

13 DB6  I/O        The 8-bit data bus

14 DB7  I/O        The 8-bit data bus

In the above table Vcc and Vss are supply pins and VEE (Pin no.3) is used for controlling LCD contrast. Pin No.4 is Rs pin for selecting the register, there are two very important registers are there inside the LCD. The RS pin is used for their selection as follows. If RS = 0, the instruction command code register is selected, allowing the user to send a command such as clear display. If RS=1, the data register is selected, allowing the user to send data to be displayed on the LCD.

R/W is a read or write Pin, which allows the user to write information to the LCD or read information from it.   R/W=1 when reading, R/W=0 when writing. The enable (E) pin is used by the LCD to latch information presented to its data pins. When data is supplied to data pins, a high–to-low pulse must be applied to this pin in order for the LCD to latch in the data present at the data pins. This pulse must be a minimum of 450 ns wide.

The 8-bit data pins, D0-D7, are used to send information to the LCD or read the contents of the LCD’S internal registers. To display letters and numbers, we must send ASCII (American Standard Code for Information Inter Change, pronounced “ask – E”) codes for the letters A – Z, and numbers 0 – 9 to these pins while making RS=1.

2.8 Relays

The electromagnetic relay, one of mankind’s first electrical device, was used practically in telegraphy as early as 1850. The modern relay, properly applied, is one of the most simple, effective and dependable component available. In the majority of instances, it can achieve better reliability at lesser cost than an equivalent solid-state complex type of relay. The term ‘relay’ was used for the first time to describe an invention made by Samuel Morse in 1836. The device invented by Morse was a “Telegraph Amplifying Electromagnetic Device” which enabled a small current flowing in a coil to switch on a large current in another circuit and thus helped in “relay” of signals.

A relay is a device that opens or closes an auxiliary circuit under some predetermined condition in the main circuit.  The object of a relay is generally to act as a sort of electric magnifier, that is to say, it enables a comparatively weak current to bring into operation a much stronger current. It also provides complete electrical isolation between the controlling circuit and the controlled circuit.

The relay used in this project work is electromagnetic relay. The electromagnetic relay is basically a switch (or a combination of switches) operated by the magnetic force generated by a current flowing through a coil.  Essentially, it consists of four parts an electromagnet comprising a coil and a magnetic circuit, a movable armature, a set of contacts, and a frame to mount all these components. However, very wide ranges of relays have been developed to meet the requirements of the industry. This relay is nothing but a switch, which operates electromagnetically. It opens or closes a circuit when current through the coil is started or stopped.  When the coil is energized armature is attracted by the electromagnet and the contacts are closed. That is how the power is applied to the signals (indicators). The construction of the typical relay contains a code surrounded by a coil of copper wire. The core is mounted on a metal frame. The movable part of the relay is called armature. When a voltage is applied to the coil terminals, the current flowing through the coil produces a magnetic field in the core. In other words, the core acts as an electromagnet and attracts the metal armature. When the armature is attracted to the core, the magnetic path is from the core through armature, through the frame, and back to the core. On removing the voltage the spring attached to the armature returns the armature to its original position.   In this position, there is a small air-gap in the magnetic path. Hence, more power is needed to pull in the armature than that needed to keep it held in the attracted position.

The relay contacts and the terminals are mounted on an insulated board. When no current flows through the relay coil, the contact arm, or pole as it is called, mounted on the armature, touches the “top” contact.   When the coil is energized by flow of current, the armature along with the contact arm assembly moves downwards; so that the contact arm touches the “bottom” contact. When an electric current is flowing through a relay coil, it is said to be energized, and when the current flow stops, the relay is said to be de-energized. They have a set of parallel contacts, which are all pulled in when the electromagnet pulls in the armature. On being energized, whether a relay makes contact(s) or breaks them depends on the design of contact arrangements. Though the contacts are open or close simultaneously, the sequence of operation cannot be guaranteed in this of construction. To have a definite switching sequence, stacked contacts are used.

2.9 Pumps

Pumps commonly used for various purposes fall into the following categories based on the design of the pump. This tutorial addresses electric powered pumps only. While most of the information here also applies to fuel powered pumps the formulas don’t! You must use different formulas for calculating the size and flow information for fuel powered pumps. If you have an engine powered pump (gas, diesel, propane, corn liquor, etc.) you should contact the pump manufacturer and request a copy of the pump performance curve. As a general rule, fuel powered pumps require more horsepower than electric pumps.

1.    Displacement Pumps:

Displacement pumps force the water to move by displacement. This means pumps such as piston pumps, diaphragm pumps, roller-tubes, and rotary pumps. The old fashioned hand-pumps, the ones you operate by moving a long lever handle up and down, are piston displacement pumps. So are those grasshopper-like oil well pumps. Displacement pumps are used for moving very thick liquids, creating very precise flow volumes, or creating very high pressures. In addition to oil wells they are also used for fertilizer injectors, spray pumps, air compressors, and hydraulic systems for machinery. With the exception of fertilizer injectors you will not see them typically used for irrigation systems, so that is all I’m going to say about them.

2.     Centrifugal Pumps:

Almost all irrigation pumps fall into this category. A centrifugal pump uses an “impeller” (sort of like a propeller, but a little different) to spin the water rapidly inside a “casing”, “chamber”, or “housing” (any of those terms may be used). This spinning action moves the water through the pump by means of centrifugal force. Centrifugal pumps may be “multi-stage”, which means they have more than one impeller and casing, and the water is passed from one impeller to another with an increase in pressure occurring each time. Each impeller/casing combination is referred to as a “stage”. All centrifugal pumps must have a “wet inlet”, that is, there must be water in both the intake (inlet) pipe and the casing when the pump is started. They can’t suck water up into the intake pipe.  They must be “primed” by filling the intake pipe and case with water.  To prime a pump you simply fill the intake pipe with water and then quickly turn on the pump.  Most centrifugal pumps are designed to trap water in the intake once they have been primed the first time, thus they “maintain their prime” between uses.

There are various types of centrifugal pumps based on the usage.

  1. End-suction Centrifugal Pumps
  2. Submersible Pumps
  3. Jet Pumps
  4. Turbine Pump

CHAPTER – 3

 

 

BLOCK & CIRCUIT DIAGRAMS

Block & circuit diagrams give the detail explanation of the project. They play a key role in making the project a prototype model.

3.1 BLOCK DIAGRAM

Block Diagram gives an overview of the project working. Here the flow of power takes place from the solar panel to the battery & then to the pumps through relays which are regulated by the microcontroller.

Block 2.jpg

Fig 3.1 Block Diagram

Parts of Block Diagram

 

  1. Solar Panel – It is the primary source of energy. It collects the energy of solar radiation & is transferred in desired specifications to the battery through charge control circuit.
  2. Charge control circuit – It helps in collecting & storing the collected energy in a battery such that there are no considerable heat losses & damages to the equipment.
  3. Dual Inverted Oscillator – Circuit is designed with SG3524 to produce 50Hz inverted outputs used to convert the DC power from battery to AC through transformer.
  4. Drive Stage with MOSFETs- To amplify the current given to the transformer is achieved with a drive stage employed using power MOSFETs.
  5. 89C51 Microcontroller – It is controlling part of the circuit. It takes input from the operator & accordingly switches the supply to pumps through relays. Also it is programmed to display the status of pumping in LCD screen.
  6. LCD Display – It shows the status of the pumping as it is interfaced to a microcontroller. The contrast of the LCD display can be regulated by changing the tap in a variable resistor.
  7. Relays – They switch the supply to the pumps according to the outputs of the microcontroller which changes as per input & user-defined program.
  8. Water Pumps – They are the load connected to the circuit which delivers the water through the distribution channel.

3.2 CIRCUIT DIAGRAM

The main circuit diagram gives the necessary idea needed to understand the project. Circuit diagram forms the heart for any electrical operation. Here all the parts of the circuit are placed at one location for a one look go.

circuit 1.jpg

 

Fig 3.2 Circuit diagram

CHAPTER – 4

Description of the Power System Operation

The complete circuit diagram shown at the end of this chapter is explained in detail, as the oscillator circuit designed with SGS3524 IC playing major roll, the description is concentrated over internal structure of this device. Though the PWM technique is not implemented here, it is explained well because this device offers good regulated output at lower voltages. This IC is having 16 pins with all built-in features and this device is used for wide variety of applications like inverters, converters, switch mode power supplies, etc. The following are the key points.

It offers wide range frequency output; the frequency can be adjusted from 1Hz to 50 KHz. Pin numbers 6 & 7 are the frequency compensation pins, by connecting a resistor & capacitor externally to these pins, frequency can be set to required level. Here the required frequency is 50Hz, according to that the values of RT & CT (Resistor for timing & Capacitor for timing) can be selected. The capacitor is charged with constant current through a fixed resistor, there by regulated pulse output can be obtained either from common emitters or common collectors.

The pre-drive stage built in with the chip can be able to supply a maximum current of 150ma from each output, hence additional pre-amplifier to drive the power stage is not required.

As this chip is designed to generate dual inverted outputs, drive stage is configured in push-pull amplifier. The advantage of using this amplifier is that the output transformer remains in energized condition continuously, thereby continuous output can be achieved from the power system.

This chip offers +5V regulated output from pin number 16; this can be used as a reference voltage for the control circuit. This voltage remains constant irrespective of variations in the input source.

In this IC pin number 10 is a shut-down pin, always it remains in zero state, whenever any control circuit generates high signal & is fed to this pin, automatically output of this chip will become zero. (As the inverter designed here doesn’t contain any protection circuits, this facility is not used.)

Soft start provision is made in the oscillator circuit, such that the power system is protected burning from sudden switching. This circuit is designed with RC network and it is connected to 9TH pin, this is a compensation pin. When the power system is switched on, the capacitor charges through resistor, based on the values of capacitor and resistor, the capacitor will take some time to charge fully, until then the outputs will not be adjusted to its maximum levels.

The main important feature offered by this chip is varying the duty cycle very linearly. This can be done by varying the voltage at compensation pin through a potential dividing network designed with a preset.

Although many switching techniques can be employed to implement a switched mode power supply, either it is converter or inverter, the fixed frequency PWM system, a square wave pulse is normally generated to drive the switching transistor / MOSFETS ON or OFF. By varying the width of the pulse, the conduction time of the MOSFET is accordingly increased or decreased, thus regulating the output voltage. The PWM control circuit may be single ended, capable of driving a single MOSFET converter, such as Fly back or forward. If two or more MOSFET’S have to be driven, as with half-bridge or full-bridge circuits, a dual channel PWM circuit is necessary. In this project work dual inverted outputs are taken from the PWM IC, so that the drive stage is designed in push-pull configuration with two power MOSFET’s.

4.1 General description of an integrated PWM controller

In recent years, a number of integrated circuits have been developed which include all the functions necessary to build a PWM switching power supply in a single package with little addition of few external components. The basic building blocks of simple PWM controller and its associated waveforms are shown below.

Fig 4.1 Building blocks of PWM controller

Fig 4.2 Corresponding waveforms of PWM controller

An op-amp compares the feedback signal from the output of the power supply to a fixed reference voltage (V-ref). The error signal is amplified and fed in to the inverting input of a comparator. The non-inverting input of the comparator accepts a saw-tooth waveform with a linear slope, generated by a fixed frequency oscillator. The oscillator output is also used to toggle a flip-flop, producing square wave outputs Q and Q. The comparator square wave output and the Flip-Flop outputs are both used to drive the AND gates, enabling each output when both inputs to the gate are high. The result is a variable duty cycle pulse train at channels ‘A’ and ‘B’. In the above figure shows the output pulse width is modulated when the error signal changes its amplitude, as detected by the dotted lines. Normally the outputs of the PWM controller are externally buffered to drive the main power switching power MOSFETS. This type of circuit may be used to drive two transistors / MOSFETS or a single Transistor / MOSFET. The merits of a PWM controller are pro-found, including the programmable fixed frequency oscillator, Linear PWM section with duty cycle from 0 to 100 percent, adjustable dead time to prevent output transistor or MOSFET simultaneous conduction, and above all simplicity, reliability, and cost effectiveness. The PWM control circuit is IC 3524, which was designed to become the industry standard. These PWM controllers are the heart for the complete switching power supply design and may be used equally well in single ended or dual channel applications. The PWM comparator provides a means for the error amplifier to adjust the output pulse width from the maximum percent on time, established by the dead-time control input, down to zero, as the voltage at the feedback varies from 0.5V to 3.5V. The error amplifier outputs are active high. With this configuration, the amplifier that demands minimum output on time dominates control of the loop.

The following are the salient features of PWM controllers

  1. Fixed frequency operation, user programmable by a simple RC Network.
  2. A variable slope Ramp generator for constant volt per second operation, providing open loop line regulation and minimizing, or in some cases eliminating the need for feedback control.
  3. A drive switch for low current start-up with direct off-line bias.
  4. A precision reference generator with internal over voltage protection
  5. Under voltage and over current protection including programmable shutdown and re-start.
  6. A high current, single ended PWM output optimized for fast turn-off of an external power switch.
  7. Logic control for pulse commendable or DC power sequencing

In this IC 3524, the internal linear saw-tooth oscillator is frequency programmable by resistor ‘RT’ and capacitor ‘CT’ (0.1 uF) which are connected to Pins 6 and 7 of the IC. To tune the frequency, in addition to 100K Resistor, 50K potentiometer is also connected. The oscillator frequency f out = 1 / RT CT. The Ramp voltage swings approximately 2.5V to change the comparator output from 0 to 1, by comparing it to either one of two control signals, i.e., the error amplifier output or the current limit amplifier output. The error amplifier input range exceeds beyond 5V, eliminating the need for a pair of dividers, for 5V outputs. To provide a reference voltage to the error amplifier, the on board 5V regulator provides with an accuracy of ± 1 percent. In this, the output pulse width modulation is accomplished by steering the resulting modulated pulse output of the high gain comparator to the PWM latch along with the pulse steering Flip-Flop, which is synchronously toggled by the oscillator output.

The PWM latch insures, freedom from multiple pulsing within a period, even in noisy environments in addition, the shutdown circuit feeds directly to this latch, which will disable the outputs within 200 n. sec. of activation. The current limit amplifier is a wide-band, high gain amplifier, which is useful for either linear or pulse by pulse current limiting in the ground or power supply lines. Its threshold is set at 200mV. An under voltage lockout will disable the internal circuitry, except the reference, until the input voltage is 8V. This action holds stand by current low until turn on, simplifies the design of low power, off line switchers. These are the advantages of this versatile controller, there by this can be used in a variety of Isolated or non-isolated switching power supplies like inverters or converters.  Hence, in this project work, this controller is selected for usage and the inverter is designed using this PWM controller.

The basic concept of pulse width Modulation is given below; In the case of op-amp, when it is configured in open loop configuration, the output will go to either +V sat or –V sat due to its high gain.   The switching of +V sat and –V sat is, whenever the inverting input is slightly more than Non-inverting input voltage, the output will be in –V sat. i.e., if inverting input dominates Non-inverting input, immediately the output will be –V sat.  The V sat will be V ± 1.5V.  Similarly, if the non-inverting voltage is slightly more over the inverting input voltage, the output voltage will be +V sat. Thus, the output will be only either +V sat or –V sat.  Now we will give RAMP or saw-tooth voltage to the non-inverting input and the feedback or some variable DC voltage will be given to the inverting input and we will see how the output voltage changes.

Fig 4.3 Output waveforms of PWM controller with Ramp/Sawtooth input

As we see the output, it’s on / off periods is changing every cycle depending up on the feedback voltage. This concept is called pulse width Modulation. Also this concept is called duty cycle variation. Duty cycle is equals to

Fig 4.4 Circuit diagram of PWM Oscillator

 

In the above circuit, the inverting input of Error amplifier (Pin No.2) is fed from V ref, built in 5V regulator through a voltage divider of two 4.7K resistors. This +5V regulator is available inside the IC.

The voltage at Pin NO.2 is 5V x 4.7K / 4.7K + 4.7K   = 2.5V.

The current limit amplifier is not used at present, hence are connected to ground.  The frequency of the internal Oscillator is adjusted with RT and CT. The Ramp generator is internally connected inside the IC to the pulse width Modulator. For details related to the internal details of the IC, it was described in the Chapter Hardware details. To shutdown the IC, i.e., to disable the PWM output, such as excess current drawn by load, the high signal to shutdown pin disables the output, and thereby inverter is protected from overload. The built in PWM generator, the complementary ‘Q’ and ‘Q’ output from the internal Flip-Flop and passes through internal NOR gates clocked by the internal Oscillator. These outputs are at 50Hz frequency (approximately) PWM output, are further amplified using class ‘B’ push-pull stages. The Pin .9 compensation input is connected with soft start circuit. This makes the PWM regulator to generate the output, when the switch ‘ON’ the unit, slowly, thereby it avoids false triggering of the protection circuits. The time constant RC is designed with 82K x 10MF = 820m sec. To reduce this delay a 6.8K and 10K potentiometer are connected as a voltage divider.

By varying the voltage at Pin no.9 (Compensation Pin) output duty cycle can be changed, for this purpose 10K Pot (variable resistor) is connected between Pin No.9 and ground. By varying the resistance reference voltage at compensation pin also can be varied very linearly. Hence by varying duty cycle output voltage can be controlled.

4.2 Description about drive stage

As described in previous chapters, the drive stage is configured as push-pull amplifier. The main purpose of this amplifier is to amplify the voltage and current levels to the required level; the required level is to drive a 60Watts load, which may consume a maximum current of 300ma at 220V ac. Therefore to be safe side, this amplifier is designed to generate 350ma maximum. In a voltage amplifier, the output voltage is many times greater than the input voltage. Similarly current is also amplified. The components in an amplifier are selected to give high gain or amplification which is the ratio of the output voltage to input voltage. The output of the oscillator, where ac signal is produced at low voltage and low currents is extremely small, and need amplification before being really useful to drive the motor. A power amplifier may have voltage gain, but the main consideration is the power output which is the product of current and voltage.

In a class ‘B’ push-pull amplifier consists of two identical drive stages at output circuitry, designed with power MOSFETs drives the main transformer. These MOSFETs are excited with equal but opposite (180 degrees out of phase) voltages from the input signal. When operated in this manner, one of the MOSFET amplifies the positive half cycles of the signal voltage while the other MOSFET amplifies the negative half cycles. The amplified half cycles are then combined in the output transformer in such a manner as to produce an amplified reproduction of the input voltage and current. In actual practice, the two MOSFETs are switched in a sequence one after another according to the biasing signals produced by the oscillator. This avoids crossover distortion. The MOSFETs are conducted one after another according to the time period, based on this frequency produced by the oscillator, a gap between the time when one MOSFET shuts off and the other is turned on and this produces a clipping effect on the output voltage. In this condition output is distorted, this type of distortion is called crossover distortion.

Fig 4.5 MOSFET drive stage circuit diagram  

In the above circuit, BC 557 general-purpose PNP switching transistors are used to drive the Power MOSFETS. The PWM outputs of regulator, which are obtained from emitters of A and B transistors (provided inside IC) are amplified to drive the load. For this, class ‘B’ push-pull stages are used in pre-driver stage and driver stage. Thus, a great deal of this distortion introduced by the Non-linearity of the dynamic transfer characteristic may be eliminated by push-pull configuration. In this case when the signal on one MOSFET is positive, the signal on other is negative by an equal amount. The advantage of push-pull amplifier is it will eliminate even harmonics. The fact that the output current contains no-even-harmonic terms means that the push-pull possesses ‘Half wave’ or ‘mirror’ symmetry in addition to the zero axis symmetry.

Because no even harmonics are present in the output of a push-pull amplifier, such a circuit will give more output per active device for a given amount of distortion. For the same reason, the push-pull arrangement is used to obtain less distortion for a given power output per MOSFET. Another advantage of push-pull arrangement is that the DC components of the collector current oppose each other magnetically in the transformer core. This eliminates any tendency toward core saturation and consequent Non-linear distortion that might arise from the curvature of the transformer magnetization curve. Another advantage is effects of ripple voltages that may be contained in the power supply because of inadequate filtering will be balanced out.

The advantage of using power MOSFETS, when compared with bipolar power transistors, because of its input high impedance No load current can be reduced and efficiency can be increased.

CHAPTER – 5

Non-Conventional Sources Of Energy – An Over View

Introduction

The Industrial Revolution of the 19th century ushered in new technologies. The spurt in inventions in that century was unprecedented in many ways. Some of these inventions involved use of natural resources like coal and oil. The thought of exhaustible nature of these resources and the environmental damage from the use of these resources never occurred either to the inventors or the subsequent generations. In the quest to sustain galloping economic activity, the dependence on coal and oil has soared at a phenomenal rate over the years. The burnt fuels result in the release of carbon-dioxide and other gases into the atmosphere causing environmental damage. It has become imperative to look at energy technology with a new perspective. There are abundant renewable sources of energy such as wind, sun, water, sea, biomass apart from even daily wastes. These sources are pollution free and hence clean energy apart from being unlimited/inexhaustible.

Power generation in India has grown in size to around 1 lakh MW and in Tamil Nadu it has increased to 7924 MW which is distributed through a vast network of transmission, sub-transmission and distribution lines that reach all villages even in remote areas. The demand for power is growing rapidly. The problem will be compounded due to fast depletion of fossil fuel deposits, quality of fuels, heavy price to be paid for basic materials plus their transportation cost and above all the environmental degradation caused by the use of conventional energy sources. Under such conditions, environment friendly and pollution-free, non-conventional and renewable energy sources known as ‘clean and green energy’ have emerged as an important alternatives to conventional energy sources. The renewable energy sources are clean and inexhaustible as they rely on sun, wind, biomass, etc., as primary sources of energy. It is estimated that, about 2000 MW can be generated from wind potential available in Tamil Nadu. As against this potential, 19 MW of power in the State Sector mostly through demonstration wind farms and 838 MW in the private sector have been harnessed as on 31.3.02, Under Biomass, the estimated potential is about 500 MW and 154MW capacity has been expected using biomass/biogases.

5.1 Non – Conventional or Renewable Energy Sources

5.1.1. Wind Energy

The evolution of windmills into wind turbines did not happen overnight and attempts to produce electricity with windmills date back to the beginning of the century. After the oil crisis of 1973, many European countries started pursuing the development of wind turbine technology seriously and their development efforts are continuing even today. The technology involves generation of electricity using turbines, which converts mechanical energy created by the rotation of blades into electrical energy; sometimes the mechanical energy from the mills is directly used for pumping water from well also. The wind power program in India was started during 1983-84 with the efforts of the Ministry of Non-Conventional Energy Sources. In India the total installed capacity from wind mills is 1612 MW, of which, Tamilnadu has an installed capacity of 858 MW as on 31.03.2002.

5.1.2. Bio Energy

Biomass is yet another important source of energy with potential to generate power to the extent of more than 50% of the country’s requirements. India is predominantly an agricultural economy, with huge quantity of biomass available in the form of rice husk&straw, jute, cotton shells of coconuts wild bushes etc. Biomass can be obtained by raising energy farms or may be obtained from organic waste. The biomass resources including large quantities of cattle dung can be used in bio-energy technologies viz., biogas, gasifier, biomass combustion, cogeneration etc., to produce energy-thermal or electricity. Biomass can be used in three ways – one in the form of gas through gasifiers for thermal applications, second in the form of methane gas to run gas engines and produce power and the third through combustion to produce steam and thereby power.

 

5.1.3. Solar Energy

Solar Power was once considered, like nuclear power, ‘too cheap to meter’ but this proved illusory because of the high cost of photovoltaic cells and due to limited demand. Experts however believe that with mass production and improvement in technology, the unit price would drop and this would make it attractive for the consumers in relation to conventional power. The Solar Photo Voltaic (SPV) technology enables the direct conversion of sun light into electricity can be used to run pumps, lights, refrigerators, TV sets, etc., and it has several distinct advantages, as it does not have moving parts, produces no noise or pollution, requires very little maintenance and can be installed anywhere. These advantages make them an ideal power source for use especially in remote and isolated areas which are not served by conventional electricity making use of ample sunshine available in India, for nearly 300 days in a year.

5.1.4. Other Sources

The other sources of renewable energy are geothermal, ocean, hydrogen and fuel cells. These have immense energy potential, though tapping this potential for power generation and other applications calls for development of suitable technologies.

(i) Geo-Thermal Energy

(ii) Ocean thermal and Tidal energy

(iii) Hydrogen and Fuel Cells

(iv) Bio fuels

5.2 Potential and Exploitation of Renewable Energy Sources

India ranks fifth in the world in Wind power with installed capacity of 1612 MW out of an estimated potential of 45,000 MW. Tamilnadu ranks first in the country in Wind power with a capacity of 858 MW out of an estimated potential of 3050 MW. In biomass power the country has an installed capacity of 381 MW out of total potential of 19500 MW. In Tamilnadu the installed capacity is 142 MW against the potential of 1000 MW. The potential available under solar photovoltaic energy is 20 MW per Sq. Km. But in view of high cost and heavy investment involved the progress is rather slow.

In Solar thermal energy (Solar Water Heater system) 15 lakh M2 collector area has been installed in the country against a potential of 1400 lakh M2. In Tamilnadu, 20084 M2 area has been installed. There is considerable scope for expanding this activity with suitable incentives.

The most note-worthy achievement of Tamilnadu has been in creating an installed capacity of about 1000 MW from the non-conventional energy sources alone in the State, i.e., 13% of the total TNEB grid capacity against 3.2% only for the country. The major component of this has come from Wind Energy (858 MW) followed by co-generation in sugar industries (142 MW). Further, this has largely come about through private investment due to attractive policy initiatives of the State and Central Governments. It may be worthwhile to offer various incentives to enhance its share further in view of the vast potential available.

CHAPTER – 6

Description of Inverters

An inverter is an electrical device that converts direct current (DC) to alternating current (AC); the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits.

Static inverters have no moving parts and are used in a wide range of applications, from small switching power supplies in computers, to large electric utility high-voltage direct current applications that transport bulk power. Inverters are commonly used to supply AC power from DC sources such as solar panels or batteries.

The electrical inverter is a high-power electronic oscillator. It is so named because early mechanical AC to DC converters was made to work in reverse, and thus was “inverted”, to convert DC to AC. The inverter performs the opposite function of a rectifier.

Many inverters are designed to provide 220 VAC from the 12 VDC source, these types of inverters can be used for many applications at domestic or industrial sides. The current outputs are differed according to the application. In this project work, one amp output inverter is designed to drive the ac motor.

An inverter converts the DC electricity from sources such as batteries, solar panels, or fuel cells to AC electricity. The electricity can be at any required voltage; in particular it can operate AC equipment designed for mains operation, or rectified to produce DC at any desired voltage. Grid tie inverters can feed energy back into the distribution network because they produce alternating current with the same wave shape and frequency as supplied by the distribution system. They can also switch off automatically in the event of a blackout. Micro-inverters convert direct current from individual solar panels into alternating current for the electric grid.

6.1 Uninterruptible power supplies

An uninterruptible power supply (UPS) uses batteries and an inverter to supply AC power when main power is not available. When main power is restored, a rectifier is used to supply DC power to recharge the batteries.

6.2 Variable-frequency drives

Variable-frequency drive controls the operating speed of an AC motor by controlling the frequency and voltage of the power supplied to the motor. An inverter provides the controlled power. In most cases, the variable-frequency drive includes a rectifier so that DC power for the inverter can be provided from main AC power. Since an inverter is the key component, variable-frequency drives are sometimes called inverter drives or just inverters.

The general case

A transformer allows AC power to be converted to any desired voltage, but at the same frequency. Inverters, plus rectifiers for DC, can be designed to convert from any voltage, AC or DC, to any other voltage, also AC or DC, at any desired frequency. The output power can never exceed the input power, but efficiencies can be high, with a small proportion of the power dissipated as waste heat.

Basic designs

In one simple inverter circuit, DC power is connected to a transformer through the centre tap of the primary winding. A switch is rapidly switched back and forth to allow current to flow back to the DC source following two alternate paths through one end of the primary winding and then the other. The alternation of the direction of current in the primary winding of the transformer produces alternating current (AC) in the secondary circuit.

The electromechanical version of the switching device includes two stationary contacts and a spring supported moving contact. The spring holds the movable contact against one of the stationary contacts and an electromagnet pulls the movable contact to the opposite stationary contact. The current in the electromagnet is interrupted by the action of the switch so that the switch continually switches rapidly back and forth. This type of electromechanical inverter switch, called a vibrator or buzzer, was once used in vacuum tube automobile radios. A similar mechanism has been used in door bells, buzzers and tattoo guns. As they became available with adequate power ratings, transistors and various other types of semiconductor switches have been incorporated into inverter circuit designs.

Output waveforms

The switch in the simple inverter described above produces a square voltage waveform as opposed to the sinusoidal waveform that is the usual waveform of an AC power supply. Using Fourier analysis, periodic waveforms are represented as the sum of an infinite series of sine waves. The sine wave that has the same frequency as the original waveform is called the fundamental component. The other sine waves, called harmonics that are included in the series have frequencies that are integral multiples of the fundamental frequency.

The quality of output waveform that is needed from an inverter depends on the characteristics of the connected load. Some loads need a nearly perfect sine wave voltage supply in order to work properly. Other loads may work quite well with a square wave voltage.

CHAPTER – 7

 

Description of Power MOSFETs

A Power MOSFET is a specific type of metal oxide semiconductor field-effect transistor (MOSFET) designed to handle large amounts of power. Compared to the other power semiconductor devices, its main advantages are high commutation speed and good efficiency at low voltages. It shares with the IGBT an isolated gate that makes it easy to drive. It was made possible by the evolution of CMOS technology, developed for manufacturing Integrated circuits in the late 1970s. The power MOSFET shares its operating principle with its low-power counterpart, the lateral MOSFET. The power MOSFET is the most widely used low-voltage switch. It can be found in most power supplies, inverters, DC to DC converters, and low voltage motor controllers. In general this device is used for amplifying or switching electronic signals. The basic principle of the device was first proposed by Julius Edgar Lilienfeld in 1925. In MOSFETs, a voltage on the oxide-insulated gate electrode can induce a conducting channel between the two other contacts called source and drain. The channel can be of n-type or p-type, and is accordingly called an NMOSFET or a PMOSFET (also commonly nMOS, pMOS).

Usually the semiconductor of choice is silicon, but some chip manufacturers, most notably IBM, recently started using a compound (mixture) of silicon and germanium (SiGe) in MOSFET channels. Unfortunately, many semiconductors with better electrical properties than silicon, such as gallium arsenide, do not form good semiconductor-to-insulator interfaces, thus are not suitable for MOSFETs. In order to overcome power consumption increase due to gate current leakage, high-κ dielectric replaces silicon dioxide for the gate insulator, while metal gates return by replacing poly silicon.

The gate is separated from the channel by a thin insulating layer, traditionally of silicon dioxide and later of silicon oxynitride. Some companies have started to introduce a high-κ dielectric + metal gate combination in the 45 nanometer node. When a voltage is applied between the gate and body terminals, the electric field generated penetrates through the oxide and creates an alleged “inversion layer” or “channel” at the semiconductor-insulator interface. The inversion channel is of the same type, P-type or N-type, as the source and drain, thus it provides a channel through which current can pass. Varying the voltage between the gate and body modulates the conductivity of this layer and allows controlling the current flow between drain and source.

7.1 Circuit symbols

A variety of symbols are used for the MOSFET. The basic design is generally a line for the channel with the source and drain leaving it at right angles and then bending back at right angles into the same direction as the channel. Sometimes three line segments are used for enhancement mode and a solid line for depletion mode. Another line is drawn parallel to the channel for the gate.

The bulk connection, is shown connected to the back of the channel with an arrow indicating PMOS or NMOS. Arrows always point from P to N, so an NMOS has the arrow pointing in (from the bulk to the channel). If the bulk is connected to the source  it is sometimes angled to meet up with the source leaving the transistor. If the bulk is not shown an inversion symbol is sometimes used to indicate PMOS, alternatively an arrow on the source may be used in the same way as for bipolar transistors.

Comparison of enhancement-mode and depletion-mode MOSFET symbols, along with JFET symbols (drawn with source and drain ordered such that higher voltages appear higher on the page than lower voltages):

JFET P-Channel Labelled.svg IGFET P-Ch Enh Labelled.svg IGFET P-Ch Enh Labelled simplified.svg Mosfet P-Ch Sedra.svg IGFET P-Ch Dep Labelled.svg P-channel
JFET N-Channel Labelled.svg IGFET N-Ch Enh Labelled.svg IGFET N-Ch Enh Labelled simplified.svg Mosfet N-Ch Sedra.svg IGFET N-Ch Dep Labelled.svg N-channel
JFET MOSFET enh MOSFET enh (no bulk) MOSFET dep

Fig 7.1 Various circuit symbols of JFETs & MOSFETs

For the symbols in which the bulk, or body, terminal is shown, it is here shown internally connected to the source. This is a typical configuration, but by no means the only important configuration. In general, the MOSFET is a four-terminal device, and in integrated circuits many of the MOSFETs share a body connection, not necessarily connected to the source terminals of all the transistors.

7.2 MOSFET operation

For the symbols in which the bulk, or body, terminal is shown, it is here shown internally connected to the source. This is a typical configuration, but by no means the only important configuration. In general, the MOSFET is a four-terminal device, and in integrated circuits many of the MOSFETs share a body connection, not necessarily connected to the source terminals of all the transistors.

H:\MOSFET_files\220px-Mosfet_n-ch_circuit.png

Fig 7.2 Example application of an N-Channel MOSFET, when the switch is pushed, the LED lights up.

Metal–oxide–semiconductor structure

A traditional metal–oxide–semiconductor (MOS) structure is obtained by growing a layer of silicon dioxide (SiO2) on top of a silicon substrate and depositing a layer of metal or polycrystalline silicon (the latter is commonly used). As the silicon dioxide is a dielectric material, its structure is equivalent to a planar capacitor, with one of the electrodes replaced by a semiconductor.

When a voltage is applied across a MOS structure, it modifies the distribution of charges in the semiconductor. If we consider a P-type semiconductor (with NA the density of acceptors, p the density of holes; p = NA in neutral bulk), a positive voltage, VGB, from gate to body (see figure) creates a depletion layer by forcing the positively charged holes away from the gate-insulator/semiconductor interface, leaving exposed a carrier-free region of immobile, negatively charged acceptor ions (see doping (semiconductor)). If VGB is high enough, a high concentration of negative charge carriers forms in an inversion layer located in a thin layer next to the interface between the semiconductor and the insulator. Unlike the MOSFET, where the inversion layer electrons are supplied rapidly from the source/drain electrodes, in the MOS capacitor they are produced much more slowly by thermal generation through carrier generation and recombination centers in the depletion region. Conventionally, the gate voltage at which the volume density of electrons in the inversion layer is the same as the volume density of holes in the body is called the threshold voltage. This structure with P-type body is the basis of the N-type MOSFET, which requires the addition of an N-type source and drain regions.

MOSFET structure and channel formation

220px-N-channel_enhancement-type_MOSFET

Fig 7.3 Cross section of an NMOS without channel formed: OFF state

220px-N-channel_mosfet

Fig 7.4 Cross section of an NMOS with channel formed: ON state

A metal–oxide–semiconductor field-effect transistor (MOSFET) is based on the modulation of charge concentration by a MOS capacitance between a body electrode and a gate electrode located above the body and insulated from all other device regions by a gate dielectric layer which in the case of a MOSFET is an oxide, such as silicon dioxide. If dielectrics other than an oxide such as silicon dioxide (often referred to as oxide) are employed the device may be referred to as a metal–insulator–semiconductor FET (MISFET). Compared to the MOS capacitor, the MOSFET includes two additional terminals (source and drain), each connected to individual highly doped regions that are separated by the body region. These regions can be either p or n type, but they must both be of the same type, and of opposite type to the body region. The source and drain (unlike the body) are highly doped as signified by a ‘+’ sign after the type of doping.

If the MOSFET is an n-channel or n-MOSFET, then the source and drain are ‘n+’ regions and the body is a ‘p’ region. As described above, with sufficient gate voltage, above a threshold voltage value, electrons from the source (and possibly also the drain) enter the inversion layer or n-channel at the interface between the p region and the oxide. This conducting channel extends between the source and the drain, and current is conducted through it when a voltage is applied between source and drain. For gate voltages below the threshold value, the channel is lightly populated, and only a very small sub threshold leakage current can flow between the source and the drain.

If the MOSFET is a p-channel or p-MOSFET, then the source and drain are ‘p+’ regions and the body is a ‘n’ region. When a negative gate-source voltage (positive source-gate) is applied, it creates a p-channel at the surface of the n region, analogous to the n-channel case, but with opposite polarities of charges and voltages. When a voltage less negative than the threshold value (a negative voltage for p-channel) is applied between gate and source, the channel disappears and only a very small sub threshold current can flow between the source and the drain. The source is so named because it is the source of the charge carriers (majority) that flow through the channel; similarly, the drain is where the charge carriers leave the channel.

CHAPTER – 8

DESCRIPTION of MICROCONTROLLERS

Introduction

A Micro controller consists of a powerful CPU tightly coupled with memory, various I/O interfaces such as serial port, parallel port timer or counter, interrupt controller, data acquisition interfaces-Analog to Digital converter, Digital to Analog converter, integrated on to a single silicon chip. If a system is developed with a microprocessor, the designer has to go for external memory such as RAM, ROM, EPROM and peripherals. But controller is provided all these facilities on a single chip. Development of a Micro controller reduces PCB size and cost of design. One of the major differences between a Microprocessor and a Micro controller is that a controller often deals with bits not bytes as in the real world application.

Intel has introduced a family of Micro controllers called the MCS-51.The microcontroller plays the major role in any embedded project. In this my project we use one microcontroller made by the ATMEL Company i.e., AT89C51.

8.1 Necessity of Microcontrollers

Microprocessors brought the concept of programmable devices and made many applications of intelligent equipment. Most applications, which do not need large amount of data and program memory, tended to be costly.

The microprocessor system had to satisfy the data and program requirements so; sufficient RAM and ROM are used to satisfy most applications. The peripheral control equipment also had to be satisfied. Therefore, almost all-peripheral chips were used in the design. Because of these additional peripherals cost will be comparatively high.

An Example:

 

8085 chip needs:

An Address latch for separating address from multiplex address and data. 32-KB RAM and 32-KB ROM to be able to satisfy most applications. As also Timer / Counter, Parallel programmable port, Serial port, and Interrupt controller are needed for its efficient applications.

In comparison a typical Micro controller 8051 chip has all that the 8051 board has except a reduced memory as follows. 4K bytes of ROM as compared to 32-KB, 128 Bytes of RAM as compared to 32-KB.          

 

Bulky

On comparing a board full of chips (Microprocessors) which is bulky with one chip with all components in it (Micro controller) which is very simple.

Debugging

Lots of Microprocessor circuitry and program to debug. In Micro controller there is no Microprocessor circuitry to debug.

 

 

Slower Development time

Micro controller do not have the excessive circuitry and the built-in peripheral chips are easier to program for operation. So peripheral devices like Timer/Counter, Parallel programmable port, Serial Communication Port, Interrupt controller and so on, which were most often used were integrated with the Microprocessor to present the Micro controller .RAM and ROM also were integrated in the same chip. The ROM size was anything from 256 bytes to 32Kb or more. RAM was optimized to minimum of 64 bytes to 256 bytes or more.

Typical Micro controller has all the following features

  • 8/16/32 CPU
  • Instruction set rich in I/O & bit operations.
  • One or more I/O ports.
  • One or more timer/counters.
  • One or more interrupt inputs and an interrupt controller
  • One or more serial communication ports.
  • Analog to Digital /Digital to Analog converter
  • One or more PWM output
  • Network controlled interface

8.2 Advantages of Micro Controllers

1. If system is developed with a microprocessor, the designer has to go for external memory such as RAM, ROM or EPROM and peripherals and hence the size of PCB will be large enough to hold all the required peripherals. But, the micro controller has got all this peripheral facility on a single chip. So development of a similar system with a micro controller reduces PCB size and cost of the design.

2. One of the major differences between a micro controller and a microprocessor is that a controller often deals with bits, not bytes as in the real world  application, for example switch contacts can only be open or close, indicators should be lit or dark and motors can be either turned on or off and so forth.

Features of 89C51 Architecture

  • Optimized 8 bit CPU for control applications and extensive Boolean processing capabilities.
  • 64K Program Memory address space.
  • 64K Data Memory address space.
  • 128 bytes of on chip Data Memory.
  • 32 Bi-directional and individually addressable I/O lines.
  • Two 16 bit timer/counters.
  • Full Duplex UART.
  • 6-source / 5-vector interrupt structure with priority levels.
  • On chip clock oscillator.

Now we may be wondering about the non-mentioning of memory space meant for the program storage, the most important part of any embedded controller. Originally this 8051 architecture was introduced with on-chip, ‘one time programmable’ version of Program Memory of size 4K X 8.

Intel delivered all these microcontrollers (8051) with user’s program fused inside the device.  The memory portion was mapped at the lower end of the Program Memory area. But, after getting devices, customers couldn’t change anything in their program code, which was already made available inside during device fabrication.

 

8.3 8051 Micro controller Architecture

The 8051 architecture consists of these specific features:

  • Eight –bit CPU with registers A (the accumulator) and B
  • Sixteen-bit program counter (PC) and data pointer (DPTR)
  • Eight- bit stack pointer (PSW)
  • Eight-bit stack pointer (Sp)
  • Internal ROM or EPROM (8751) of 0(8031) to 4K (8051)
  • Internal RAM of 128 bytes:
  1. Four register banks, each containing eight registers
  2. Sixteen bytes, which maybe addressed at the bit level
  3. Eighty bytes of general- purpose data memory
  • Thirty –two input/output pins arranged as four 8-bit ports:p0-p3
  • Two 16-bit timer/counters: T0 and T1
  • Full duplex serial data receiver/transmitter: SBUF
  • Control registers: TCON, TMOD, SCON, PCON, IP, and IE
  • Two external and three internal interrupts sources.
  • Oscillator and clock circuits.

PIN DIAGRAM

PIN

Fig 8.1 PIN DIAGRAM OF 89C51 IC

FUNCTIONAL BLOCK DIAGRAM OF MICROCONTROLLER

C:\Users\shiva-pc\Desktop\89c51.PNG

Fig 8.2 Functional block diagram of micro controller

VCC: -Supply voltage (+5V)

VSS: -Circuit ground potential

All four ports in the 89C51 are bidirectional. Each consists of a latch (Special Function Registers P0 through P3), an output driver, and an input buffer. The output drivers of Ports 0 and 2, and the input buffers of Port 0, are used in accesses to external memory. In this application, Port 0 outputs the low byte of the external memory address, time-multiplexed with the byte being written or read. Port 2 outputs the high byte of the external memory address when the address is 16 bits wide. Otherwise, the Port 2 pins continue to emit the P2 SFR content. All the Port 3 pins are multifunctional. They are not only port pins, but also serve the functions of various special features as listed below

 

Table No: 8.1 Special functions of Port 3 pins (8051µC)

Port Pin                          Alternate Function

P3.0                           RxD (serial input port)

P3.1                           TxD (serial output port)

P3.2                           INT0 (external interrupt)

P3.3                           INT1 (external interrupt)

P3.4                           T0 (Timer/Counter 0 external input)

P3.5                           T1 (Timer/Counter 1 external input)

P3.6                           WR (external Data Memory write strobe)

P3.7                           RD (external Data Memory read strobe)

8.4 The 8051 Oscillator and Clock

The heart of the 8051 circuitry that generates the clock pulses by which all the internal all internal operations are synchronized. Pins XTAL1 and XTAL2 is provided for connecting a resonant network to form an oscillator. Typically a quartz crystal and capacitors are employed. The crystal frequency is the basic internal clock frequency of the microcontroller. The manufacturers make 8051 designs that run at specific minimum and maximum frequencies typically 1 to 16 MHz.

Fig 8.3 Oscillator and timing circuit

8.5 Types of memory

The 8051 have three general types of memory. They are on-chip memory, external Code memory and external Ram. On-Chip memory refers to physically existing memory on the micro controller itself. External code memory is the code memory that resides off chip. This is often in the form of an external EPROM. External RAM is the Ram that resides off chip. This often is in the form of standard static RAM or flash RAM.

 

Code memory

 

Code memory is the memory that holds the actual 8051 programs that is to be run. This memory is limited to 64K. Code memory may be found on-chip or off-chip. It is possible to have 4K of code memory on-chip and 60K off chip memory simultaneously. If only off-chip memory is available then there can be 64K of off chip ROM. This is controlled by pin provided as EA.

Internal RAM

The 8051 have a bank of 128 bytes of internal RAM. The internal RAM is found on-chip. So it is the fastest Ram available. And also it is most flexible in terms of reading and writing. Internal Ram is volatile, so when 8051 is reset, this memory is cleared. 128 bytes of internal memory are subdivided. The first 32 bytes are divided into 4 register banks. Each bank contains 8 registers. Internal RAM also contains 128 bits, which are addressed from 20h to 2Fh. These bits are bit addressed i.e. each individual bit of a byte can be addressed by the user. They are numbered 00h to 7Fh. The user may make use of these variables with commands such as SETB and CLR.

8.5.1 Special Function registered memory

Special function registers are the areas of memory that control specific functionality of the 8051 micro controller.

Accumulator (8-bit)

B register

Stack pointer

Data pointer

Program counter

PCON (Power Control)

TCON (Timer Control)

TMOD (Timer Mode)

Timer 0 (T0)

Timer 1 (T1)

Port 0 (P0)

Port 1 (P1)

Port 2 (P2)

Port 3 (P3)

Interrupt Enable (IE)

Interrupt Priority (IP)

Program Status Word (PSW)

Serial Buffer (SBUF)

 

8.6 I/O Ports

One major feature of a microcontroller is the versatility built into the input/output (I/O) circuits that connect the 8051 to the outside world. The main constraint that limits numerous functions is the number of pins available in the 8051 circuit. The DIP had 40 pins and the success of the design depends on the flexibility incorporated into use of these pins. For this reason, 24 of the pins may each used for one of the two entirely different functions which depend, first, on what is physically connected to it and, then, on what software programs are used to “program” the pins.

PORT 0

Port 0 pins may serve as inputs, outputs, or, when used together, as a bi directional low-order address and data bus for external memory. To configure a pin as input, 1 must be written into the corresponding port 0 latch by the program. When used for interfacing with the external memory, the lower byte of address is first sent via PORT0, latched using Address latch enable (ALE) pulse and then the bus is turned around to become the data bus for external memory.

 

PORT 1

Port 1 is exclusively used for input/output operations. PORT 1 pins have no dual function. When a pin is to be configured as input, 1 is to be written into the corresponding Port 1 latch.

PORT 2

Port 2 may be used as an input/output port. It may also be used to supply a high –order address byte in conjunction with Port 0 low-order byte to address external memory. Port 2 pins are momentarily changed by the address control signals when supplying the high byte a 16-bit address. Port 2 latches remain stable when external memory is addressed, as they do not have to be turned around (set to 1) for data input as in the case for Port 0.

PORT 3

Port 3 may be used to input /output port. The input and output functions can be programmed under the control of the P3 latches or under the control of various special function registers. Unlike Port 0 and Port 2, which can have external addressing functions and change all eight-port b se, each pin of port 3 maybe individually programmed to be used as I/O or as one of the alternate functions. The Port 3 alternate uses are:

 

Table No: 8.2 Port 3 Alternate Uses (8051µC)

Pin (SFR) Alternate Use
P3.0-RXD (SBUF) Serial data input
P3.1-TXD (SBUF) Serial data output
P3.2-INTO 0  (TCON.1) External interrupt 0
P3.3 – INTO 1  (TCON.3) External interrupt 1
P3.4 – T0 (TMOD) External Timer 0 input
P3.5 – T1 (TMOD) External timer 1 input
P3.6 – WR External memory write pulse
P3.7 – RD External memory read pulse

 

8.7 INTERRUPTS

Interrupts are hardware signals that are used to determine conditions that exist in external and internal circuits. Any interrupt can cause the 8051 to perform a hardware call to an interrupt –handling subroutine that is located at a predetermined absolute address in the program memory.

Five interrupts are provided in the 8051. Three of these are generated automatically by the internal operations: Timer flag 0, Timer Flag 1, and the serial port interrupt (RI or TI) Two interrupts are triggered by external signals provided by the circuitry that is connected to the pins INTO 0 and INTO1. The interrupts maybe enable or disabled, given priority or otherwise controlled by altering the bits in the Interrupt Enabled (IE) register, Interrupt Priority (IP) register, and the Timer Control (TCON) register. . These interrupts are mask able i.e. they can be disabled. Reset is a non maskable interrupt which has the highest priority. It is generated when a high is applied to the reset pin. Upon reset, the registers are loaded with the default values.

Each interrupt source causes the program to do store the address in PC onto the stack and causes a hardware call to one of the dedicated addresses in the program memory. The appropriate memory locations for each for each interrupt are as tabulated below.

Table No: 8.3 Interrupts memory location (8051µC)

Interrupt  Address
RESET 0000
IE0 (External interrupt 0) 0003
TF0 (Timer 0 interrupt) 000B
IE1 (External interrupt 1) 0013
TF1 (Timer 1 interrupt) 001B
SERIAL 0023

CHAPTER – 9

 

Description of Solar Panels

9.1 Introduction

Solar photovoltaic systems use solar energy to produce electricity. The term photovoltaic is composed of “photo”, the Greek root for “light”, and “volt”, a common measurement of electricity named after Alessandro Volta, a scientist renowned for his research on electricity. Together, these terms literally mean “light electricity”. Photovoltaic technology can be referred to in short as photovoltaic’s or PV. Photovoltaic technology relies on the electrical properties of certain materials known as semiconductors. When hit by sunlight, a semiconductor material responds by creating an electrical charge which can then be transferred to anything that uses electricity. These semiconductors are produced in the form of cells, which can then be assembled in groups in a panel. Individual panels are often used to charge batteries that power small or remote electric equipment. Depending on the amount of electricity needed, these panels can then be connected in an array to provide larger amounts of electricity to a building or other large user of electricity.

Photovoltaic cells and panels can be manufactured and installed at almost any scale, and as a result are used to power a broad variety of applications. At its smallest, photovoltaic technology powers calculators, laptop computers and other appliances that run on batteries. At its largest, it powers homes, offices and other buildings that use large amounts of electricity, and can be connected to utilities to increase the diversity of our collective electricity supply.

There are many benefits to using photovoltaics as an electricity source, most notably their environmental benefits. As one of the cleanest electricity-generating technologies available, photovoltaics hold much promise for reducing environmental impacts from energy production. At the same time, several barriers exist for widespread use of this technology, the largest of which is its current cost. In spite of its barriers, photovoltaics are becoming more widely used each year, and many examples exist throughout the world.

 

9.2 Photovoltaic Cells

Photovoltaic cells, which convert light directly into electricity, have become commonplace on devices such as calculators and watches. There are a number of technologies in development with the aim of making PV more economic for electrical power generation. All use semiconductor materials like those used in silicon chips.

The heart of a PV cell is the interface between two different types of semiconductor. When a light photon hits a silicon atom in this region, it throws out an electron. The electron can travel through the n-type semiconductor to metal contacts on the surface. The hole left by the absence of the electron travels in the opposite direction. Once at the metal contact the electron flows through an electrical circuit back to meet up with a hole at the other contact. As it flows through the external circuit, the electron does useful work, like charging a battery, or operating an electrical appliance. Photovoltaic systems have been reducing in cost, and increasing in efficiency in recent years. The most efficient commercially available systems can convert up to 16% of the light energy that strikes them into electrical energy.

Solar energy is harnessed using photovoltaic cells. Groups of photovoltaic cells are known as solar modules. There are a range of products using single crystal solar cells producing 30 to 165 watts of power. The modules can be adapted to off-grid or on-grid power generation needs. The modules offer a 20-25 year warranty. The modules based on crystalline silicon are one of the most efficient available on a commercial basis. The modules are formed by a series of cells wired together and are available in complete packages for residential, commercial, and industrial purposes. PV panels, on the other hand, convert light into electricity. Most commonly, these panels are placed on the roof. The power generated by PV panels is transmitted to a battery for storage. Household power needs are drawn from this storage.

Photovoltaic cells work by transforming the photon energy in solar radiation directly into electrical energy without an intermediate mechanical or thermal process. A photovoltaic cell consists of layers of semiconductor materials in contact with each other and fitted with metallic contacts to transfer the released electrons to the external load. Most commercial photovoltaic cells now available are manufactured from crystalline silicon. This is then fitted with the metallic contacts and encapsulated for protection. PV cells operate on the principle that electricity will flow between two different semiconductors when they are put in contact with each other and exposed to light. By linking a number of these cells together a flow of electricity can be achieved.

9.3 Overview of the technology

Sunlight is composed of photons containing energy which correspond to the different wavelengths of the solar spectrum. When photons strike a PV cell, their energy is transferred to an electron in the semiconductor material of the cell. With this extra energy, the electron is then able to escape from its normal position in the atom creating a “hole”, which will become part of a current in an electrical circuit.

When photons fall on these layers they transfer energy and momentum to charge carriers, which increase their potential energy by an amount depending on the diode’s material properties. Because of their electrical properties, PV modules produce direct current (DC) rather than alternating current (AC). In the simplest PV systems, DC current is used immediately in applications but where AC is required; an inverter is added to the system to convert DC into AC. The efficiency of the photovoltaic conversion process would be about 85% if each photon could transfer all its energy into that of charge carriers. However, this is normally not the case as any transfer of energy from photon to charge carrier can only be of the amount given by the band-gap of the semiconductor material. Photons with energies below the energy band-gap of the material are lost from the photovoltaic effect and converted into heat. In addition, photons with energies above the band-gap transfer no more than the band-gap energy, and any excess energy is lost. In today’s cells, both of these effects individually limit the theoretical efficiency to 50%. Currently, practical maximum efficiencies are in the range of 15-20%. Ideally, PV cells would consist of material layers with different band-gaps, for each photon to be absorbed exactly where its energy matches the band-gap energy.

The output from a PV module depends on the amount of incident light and other factors such as temperature and the cleanliness of the cell surface. Modules are rated in terms of their peak output (Peak Watts, or Wp), which is the maximum power that they will produce given calibrated solar input and operating conditions.

CHAPTER – 10

Relays & Their Applications

In a relay’s most basic function, the switching of a load circuit is controlled by a low power, electrically isolated input signal. In the past, Electromechanical Relays (EMRs) have been the component of choice, largely due to price, function, and availability. Now, however, the emergence of semiconductor technology has provided the means to manufacture solid-state relays (SSRs), which in many applications outperform their predecessors.

Solid-state relays provide the advantages of almost infinite switching lives, bounce-free operation, and immunity to EMI, higher operating speeds, low-level control signals, small package size, and multi-function integration. These advantages can save the design engineer board space, component count, time and money while improving product life, performance, and reliability.

Solid State Optronics, Inc. has been a leader in the design, development, and production of low cost, high performance SSRs over the past 15 years. SSO offers a wide range of MOSFET & SCR based relays, complemented by a growing selection of multifunction telecommunication components. By reducing cost and package size while increasing function and performance, solid state relays from SSO now serve as a viable and superior option to electromechanical relays. This application note will compare the operation of a typical EMR to that of a solid state relay, and examine advantages of each in different types of applications.

10.1 The Electromechanical Relay

Figure 10.1 shows the topology of a typical electro-mechanical relay. An input voltage is applied to the coil mechanism. The input voltage magnetizes the core which pulls the arm towards it. This action causes the output contacts to touch, closing the load circuit. When the input voltage is removed, the spring lever will push the contacts away from each other, breaking the load circuit connection.

Inherent in its design, the EMR must make mechanical contacts in order to switch a load. At the point of these contacts, oxidation breakdown occurs over extended life cycling (typically 106 operations), and the relay will need to be replaced. When an EMR is activated, bounce occurs at the contact site. Bounce creates a window of time where the load circuit is flickering between open and closed, a condition which may need to be considered in load design. Because there are internal mechanical components with physical dimension restraints, the package size of an EMR can limit the size of a PCB design. Isolation voltage is another area where EMRs are limited. Most EMRs are typically rated for minimum input to output isolation voltages of 1500 to 2000 VAC.

Figure 1:  Electromechanical Relay (EMR)
Fig 10.1 Electro mechanical Relay (EMR)

10.2 The Solid State Relay

Figure 2 shows the topology of a typical 1 Form A, MOSFET based SSR. An input current is applied to the LED, which in most cases is a Gallium Arsenide (GaAs) infrared LED. The emitted light is reflected within an optical dome, generally constructed of a gel-like lensing material, onto a series of photo diodes. The photodiodes generate a resulting voltage which, through driver circuitry, is used to control the gates of two MOSFETs.

All of the components are fabricated out of semiconductor material and as a result, the solid state relay combines many operational characteristics not found in other types of devices. Because there are no moving parts, solid state relays have established switching lives of more than 1010 cycles, and exhibit bounce-free operation. The input LEDs require low signal levels (<5mA) to guarantee operation, making SSRs ideal for TTL and CMOS controlled circuits or products where low power consumption is a necessity. The input to output isolation of solid state relays is determined by material properties of the molding compound and lensing material. These properties allow for minimum isolation voltages of 2500 VAC and up to 5000 VAC in some cases. As semiconductor technology has developed smaller and smaller components, the overall package size of solid state relays has shrunk, allowing the designer to conserve PCB space, and makes them valuable in PCMCIA applications.

Figure 2:  Solid State Relay (SSR)

Fig 10.2 Solid State Relay (SSR)

10.3 SSRs vs. EMRs

By the nature of design, one can see the differences between an electromechanical relay and a solid-state relay. In an effort to demonstrate inherent advantages of each type of relay, the following characteristics should be examined: Service Life, Reliability, Isolation Voltage, On Resistance, Capacitance and Package Dimensions.

  • Service Life: Because of solid-state technology, the SSR definitely exhibits a longer operational life. Since there are no moving parts to jam, degrade or warp, the life span is virtually infinite.
  • Reliability: During initial operation, both types of relay will exhibit similar levels of reliability. Over time, however, the solid state relay will gain the edge for the same reasons it has a longer service life, there are no moving parts. Also, bounce free operation increases reliability and ensures consistent load control.
  • Isolation Voltage: Again, by the characteristics of construction, the solid-state relay will almost always exhibit higher input to output isolation voltages than an electromechanical relay. For many telecommunication applications, a minimum of 3750VAC is desired, clearly making the SSR the optimal choice in telecom design.
  • On Resistance: Electromechanical relays have an On Resistance in the range of 100 milliohms, whereas SSRs have an On Resistance in the range of 10 Ohms. The higher On Resistance of SSRs is due to the nature of the MOSFET. The low On Resistance of the EMR allows for greater load current capability and less signal attenuation.
  • Output Capacitance: Electromechanical relays typically have an output capacitance of less than 1 picoFarad, whereas SSRs typically have a capacitance of greater than 20 picoFarads. Capacitance becomes an issue in high frequency signals, and EMRs are a better option for HF applications.
  • Package Dimensions: The internal components of the relays control the overall package dimensions. Because there are mechanical parts (coil, core, arm, contact lever arms, spring mechanism) within the EMR, the package size is limited to the physical dimensions of functional internal components. The SSR on the other hand, is limited to only the size of the semiconductor components, and is clearly capable of being manufactured in a much smaller package.

10.4 Relay Applications

In general, the point of a relay is to use a small amount of power in the electromagnet — coming, say, from a small dashboard switch or a low-power electronic circuit — to move an armature that is able to switch a much larger amount of power. For example, you might want the electromagnet to energize using 5 volts and 50 milliamps (250 milliwatts), while the armature can support 120V AC at 2 amps (240 watts).

Relays are quite common in home appliances where there is an electronic control turning on something like a motor or a light. They are also common in cars, where the 12V supply voltage means that just about everything needs a large amount of current. In later model cars, manufacturers have started combining relay panels into the fuse box to make maintenance easier. For example, the six gray boxes in this photo of a Ford Windstar fuse box are all relays: In places where a large amount of power needs to be switched, relays are often cascaded. In this case, a small relay switches the power needed to drive a much larger relay, and that second relay switches the power to drive the load. Relays can also be used to implement Boolean logic. See How Boolean Logic Works for more information.

Chapter – 11

 

Description of LCD Interfacing

The display section is designed with LCD panel; this panel is interfaced with microcontroller through its output port. This panel is having two rows, and each row contains 16 characters. These panels are capable of display numbers, characters, and graphics. The display contains two internal byte-wide registers, one for commands (RS=0) and the second for characters to be displayed (RS=1), it also contains a user. Programmed RAM area (the character RAM), that can be programmed to generate any desired character can be formed using a dot matrix. To distinguish between these two data areas, the hex command byte 80 will be used to signify that the display RAM address 00h is chosen.

The LCD circuit is constructed with 89C51 microcontroller. The LCD contains 16 pins of which 8 are data pins and 3 are control pins. The microcontroller used in this project work is having 32 I/O lines and 10 I/O lines are interfaced with LCD panel, D0 – D7 of LCD panel are called as 8 – bit data pins and this panel acquires the information from microcontroller through this data pins. The following figure shows how the display unit is interfaced to the Microcontroller.

         Fig 11.1 Interfacing the display unit to the microcontroller

Interfacing the display unit to the microcontroller

As seen from the above figure, Pins from 7 to 14 are data pins used for the selection of a particular character and pins 4 to 6 are Control signal pins used for performing Register bank selection, Read / Write and Enable pins respectively. By adjusting the voltage at pin number 3 we can change the contrast of the display. To display a particular character its associated logic sequence has to be placed on the data pins and write signal (Pin-6) has to be enabled. Microcontroller takes care of all these things based on the program loaded into it. In the receiving end, Microcontroller places the logic sequence on the data pins based on the information obtained from the decoder output.

 

Table No: 11.1 Function of each pin of LCD

Pin    Symbol          I/O         Description

1           Vss  —        Ground

2           Vcc  —        +5V Power Supply

3           VEE  —         Power supply to Control Contrast

4           RS   I         RS = 0 to select command  register,

RS=1 to select data register

5           R/W   I        R/W =0 for write, R/W=1 for read

6     E  I/O        Enable

7           DB0  I/O        The 8-bit data bus

8   DB1  I/O        The 8-bit data bus

9           DB2  I/O        The 8-bit data bus

10 DB3  I/O        The 8-bit data bus

11 DB4  I/O        The 8-bit data bus

12 DB5  I/O        The 8-bit data bus

13 DB6  I/O        The 8-bit data bus

14 DB7  I/O        The 8-bit data bus

In the above table Vcc and Vss are supply pins and VEE (Pin no.3) is used for controlling LCD contrast. Pin No.4 is Rs pin for selecting the register, there are two very important registers are there inside the LCD. The RS pin is used for their selection as follows. If RS = 0, the instruction command code register is selected, allowing the user to send a command such as clear display. If RS=1, the data register is selected, allowing the user to send data to be displayed on the LCD.

R/W is a read or writes Pin, which allows the user to write information to the LCD or read information from it. R/W=1 when reading, R/W=0 when writing. The enable (E) pin is used by the LCD to latch information presented to its data pins. When data is supplied to data pins, a high –to-low pulse must be applied to this pin in order for the LCD to latch in the data present at the data pins. This pulse must be a minimum of 450 ns wide.

The 8-bit data pins, D0-D7, are used to send information to the LCD or read the contents of the LCD’S internal registers. To display letters and numbers, we must send ASCII (Antenna Standard Code for Information Inter Change, Pronounced “ask – E”) codes for the letters A – Z, and numbers 0 – 9 to these pins while making RS=1.

 

 

 

 

11.1 Interfacing LCD to Microcontroller

This section explains about how to interface the LCD to Microcontroller, before interfacing we have to study the operation modes of LCD’s and how to program using assembly language and C.

The instruction command codes from microcontroller can be sent to the LCD to clear the display, depending up on the command the cursor can be brought to home position or blink the cursor. The LCD is having two important resistors internally, command resistor and data register; RS pin is used to select either command register or data register. If RS = 0, the instruction command code register is selected and allowing the user to send a command to clear the display. If RS = 1 the data register is selected, there by the user is allowed to send data that is to be displayed on LCD screen. By making RS pin to zero, we can also check the busy flag bit to see if the LCD is ready to receive information. As already mentioned that D0 – D7 of LCD pins are 8 – bit data pins and the busy flag is D7, it can be read when R/W (Read or Write) pin is high (R/W = 0) and RS = 0, as follows; if R/W = 1, R/S = 1. When D7 pin is high, the LCD is busy taking care of internal operations and will not accept any new information. When D7 = 0, the LCD is ready to receive new information. It is recommended to check the busy flag before writing any data to the LCD.

 

Table No: 11.2 Instruction command codes for LCD

Code Command to LCD Instruction
1 Clear display screen
2 Return home
4 Decrement cursor (shift cursor to left)
6 Increment cursor (shift cursor to right)
5 Shift display right
7 Shift display left
8 Display off, cursor off
A Display off, cursor on
C Display on, cursor off
E Display on, cursor blinking
F Display on, cursor blinking
10 Shift cursor position to left
14 Shift cursor position to right
18 Shift the entire display to the left
IC Shift the entire display to the right
80 Force cursor to beginning of first line
CO Force cursor to beginning of second line
38 2 Lines and 5×7 Matrix

To send any commands from instruction command code table to the LCD, make RS pin to zero. For data, feed high signal to RS pin, then send a high – to – low pulse to the E pin to enable the internal latch of the LCD. For this, the suitable program is to be prepared for LCD connections.

CHAPTER – 12

Software Description with Chip Burning Process

Developing software and hardware for micro controller based Embedded systems involves the use of a range of tools that can include editors, assemblers, Compilers, debuggers, simulators, emulators and Flash/OTP programmers. To the Newcomer to micro controller development it is often not clear how all of these Different components play together in the development cycle and what differences There are for example between Trainer kits, emulators and simulator. The basic operations that are involved in above micro controller development cycle are:

1. Writing Micro controller Code.

2. Translating the Code.

3. Debugging the code.

Writing micro controller code:

Software Code for a micro controller is written in a programming language of choice (often Assembler or C). This source code is written with a standard ASCII text editor and saved as an ASCII text file. Programming in assembler involves learning a micro controller’s specific instruction set (assembler mnemonics), but results in the most compact and fastest code. A higher-level language like C is for the most part independent of a micro controller’s specific architecture, but still requires some controller specific extensions of the standard language to be able to control all of a chip’s peripherals and functionality. The penalty for more portable code and faster program development is a larger code size (20%…40% compared to assembler).

Translating the code:

Next the source code needs to be translated into instructions the micro controller can actually execute. A microcontroller’s instruction set is represented by “op codes”. Op codes are unique sequences of bits (“0” and “1”) that are decoded by the controller’s instruction decode logic and then executed. Instead of writing op-codes in bits, they are commonly represented as hexadecimal numbers, whereby one hex number represents 4 bits within a byte, so it takes two hex numbers to represent 8 bits or 1 byte. For that reason a micro controller’s firmware in Machine-readable form is also called Hex-Code and the file that stores that code Hex-File.

Debugging the Code

A debugger is a piece of software running on the PC, which has to be tightly integrated with the emulator that you use to validate your code. For that reason all emulator manufacturers ship their own debugger software with their tools, but also compiler manufacturers frequently include debuggers, which work with certain   emulators, into their development suites

Advantages

1. One of the advantages of an embedded system is to decrease power consumption and space.

2. All embedded systems that are based on micro controller have low power consumption in addition to some form of I/O, COM port and ROM all on a single chip.

12.1 Chip Burning Process

The process of chip burning depends up on the compiler kit, the CA51 Compiler Kit for the 8051 micro controller family supports all 8051 derivatives including those from companies like Analog Devices, Atmel, Cypress Semiconductor, Dallas Semiconductor, Goal, Hynix, Infineon, Intel, OKI, Philips, Silicon Labs, SMSC, ST Microelectronics, Synopsis, TDK, Temic, Texas Instruments, and Winbond.

The following components are included in the CA51 8051 C-compiler & Assembler Kit:

12.1.1 C51 ‘C’ Compiler

The Keil C51 ‘C’ Compiler for the 89C51 micro controller is the most popular 8051 ‘C’ compiler in the world. It provides more features than any other 8051 ‘C’ compiler available today.

The C51 Compiler allows you to write 89C51 micro controller applications in C that have the efficiency and speed of assembly language. Language extensions in the C51 Compiler give you full access to all resources of the 8051.

C51 translates C source files into a re-locatable object module. When the DEBUG control is used, the object file contains full symbolic information for debugging with the µVision3 Debugger or an in-circuit emulator. In addition to the object file, the C51 Compiler generates a listing file, which optionally may include symbol table and cross-reference information.

A51 Macro Assembler

The A51 Assembler is a macro assembler for the 8051 family of micro controllers. It supports all 8051 derivatives. It translates symbolic assembly language mnemonics into relocatable object code where the utmost speed, small code size, and hardware control are critical. The macro facility speeds development and conserves maintenance time since common sequences need only be developed once. The A51 assembler supports symbolic access to all features of the 8051 architecture.

The A51 assembler translates assembler source files into a relocatable object module. The DEBUG control adds full symbolic information to the object module and supports debugging with the µVision3 Debugger or an in-circuit emulator. In addition to object files, the A51 assembler generates list files, which optionally may include symbol table and cross reference information.

OH51 Object-HEX Converter

The OH51 Object-HEX converter creates Intel HEX files from absolute OMF51 object modules, created by the Keil A51 assembler, BL51 code banking linker, or OC51 banked object converter.

Intel HEX files are ASCII files that contain a hexadecimal representation of your program. They easily may be loaded into a device programmer for writing EPROM’s or other memory devices.

12.1.2 KEIL Compiler

It’s very easy to work with Keil as we can write the programs in C or assembly language. The basic steps to compile and run a program in assembly language:

1. Open the Keil

2. Open project window and then select a new project and save it by any name like exam1.

3. Now a “select device for target ‘target1’ ” window will appear.
Select the name of the chip vendor (Intel, Philips,  etc.) in the Vendor box. Select the device family from the drop down menu in the Family box. Enter the part number for the device in the Device box. I select ATMEL, after clicking on Atmel it will give device no. I select AT89C51.

4. Now in “project workspace”(window on the left side), target1 will appear. Click on target1, source group1 will appear.

5. Open new file and write a program in assembly. Save it with .asm (like ‘exam.asm’).

6. Now right click on the ‘source group1’. Select add files to group ‘source group1’

7. Give the file name like ‘exam.asm’ and add it and close that window. Again left click on the source group1; you can see the added file.

8. Right click on this added file and select “build target”. By this you can compile your program. Check the output window. If you’re pro is compiled properly then go to ‘Debug’.

9. Select ‘start/stop debug session’.

10. In project workspace you can see how your program is running.

11. Again go to ‘Debug’ and see F11 is there for running your program step-by-step.

12. Press F11 or F5.

13. Again go toDebug and select ‘start/stop debug session’ to stop the program.

CHAPTER – 13

Hardware Details

The IC’s and other important components used in this project work are procured from the Hyderabad Electronics Market. The details or data sheets of the IC 3524 are down loaded from the Internet

The following are the IC and other important components used in this project work

1) SG 3524 Regulating Pulse Width Modulation

2) Z44 Power MOSFET

3) Voltage Regulators (7805, 7815)

4) Mains output transformer

5) 2N5296 NPN Transistor

6) 555 Timer Chip

7) AT89C51 Controller chip

8) Relays

9) Pumps

The required PCB’S (Printed Circuit boards) for the project work fabricated by SUN RISE CIRCUITS, Kushaiguda Industrial Estate, Hyderabad.  Kushaiguda Industrial Estate is very famous for fabricating the Industrial grade PCB’s.

CHAPTER – 14

Conclusions & Future Scope

Conclusions:

The project work “Solar Power System with Timely controlled water management System” is successfully designed tested and a demo unit is fabricated. Since it is a demonstration unit, a low power inverter is designed which can able to deliver a maximum current of 350 milliamps at 220V at the system output. But for the practical applications, a higher rating inverter can be designed which can be used for the multiple applications simultaneously.

As the power system is designed to deliver less power, protection circuits are not included. In general the higher rating inverters are equipped with thermal protection, over load cut off circuits, etc. With the help of a load monitoring circuit often designed with CT, the load applied to the inverter will be monitored continuously, whenever the load exceeds more than the rated value, immediately system will be shut-down. After reducing the load and by activating the reset button power will be resumed. Similarly thermal protection system also protects the power system burning due to over temperature. These are the features to be added in our future work.

In this project work solar is used for charging the battery, this is a type of method, which comes under non-conventional method of power generation. Sun is the primary source of the energy; the energy radiated by the sun is in the form of electromagnetic waves. In the same way the other natural energy sources are also abundant in nature. The great advantage of using these methods in non-conventional energy resources, the energy produced by these methods is plentiful, inexhaustible, non-polluting and it does not require in a operator and also does not require any maintenance.

Future Scope:

The actual project is aimed at making demo of the genuine ways of controlling the water supply system. It can be further developed based in terms of timing durations, giving input signals to the controller etc.
The best suitable applications of the project appear to be like for regular house-hold purposes, industries, hospitals, drinking water supply for municipal corporations and so on. As said earlier, for every application we can change the input methods to ease the use of usage mechanism.

 

References:

In order to select a suitable topic for the project, few books are referred. The list is as follows:

  1.         Power systems                       By: J.B. GUPTA
  2.         Solar Energy Utilization                   By: G.D. Rai
  3.         Power from the Sun – A practical guide to   By: Dan Chiras

solar electricity

  1.         Wind and solar power systems      By:  Mukund R. Patil
  2.         Solar electricity hand book             By: Michael boxwel
  3.         Power Electronics                            By: P.C. Sen
  4.         Basic electronics    By: GROB
  5.         Electronic Circuit guide book – Sensors – By JOSEPH J.CARR
  6.         Linear Integrated Circuits – By: D. Roy Choudhury, Shail Jain
  7.   Digital Electronics By JOSEPH J.CARR
  8.   Digital and Analog Communication System By: K. sam Shanmugam
  9.   The concepts and Features of Micro-controllers – By: Raj Kamal
  10.   The 8051 Micro-controller Architecture, programming & Applications – By: Kenneth J. Ayala
  11.   Programming and Customizing the 8051 Micro-controller – By: Myke Predko
  12.   The IC 555 Timer Applications Source book – By: HOWARD M. BERLIN
  13.   Electronic Devices & Circuits – ALLEN MOTTERSHEAD
  14.   Practical transistor circuit design and analysis By: GERALD E.            WILLIAMS
  15.   Electronic Instrumentation and Measurement Techniques By: William

APPENDIX

 

Microcontroller Code

RS         BIT  P2.6

EN        BIT  P2.7

RLY1      BIT  P2.0

RLY2       BIT  P2.1

KEY1      BIT  P3.2

KEY2      BIT  P3.3

org  0000h

CLR     RLY1

CLR     RLY2

MOV    a,#30H

lcall  com

LCALL   DELAY

mov     a,#38h   ;2 line lcd intialization

lcall   com

lcall   delay

mov     a,#01h   ;clear the screen

lcall   com

lcall   delay

mov     a,#0Ch

lcall   com

lcall   delay

mov     a,#01h   ;clear the screen

lcall   com

lcall   delay

mov     a,#80h

lcall   com

lcall   delay

lcall   menu

main:         JB       KEY1,XX

SETB     RLY1

LCALL    R1ON

LCALL    SECS_30

CLR      RLY1

LCALL    R1OFF

SETB     RLY2

LCALL    R2ON

LCALL    SECS_30

CLR      RLY2

LCALL    R2OFF

XX:           JB       KEY2,MAIN

SETB     RLY1

SETB     RLY2

LCALL    R1ON

LCALL    R2ON

LCALL    SECS_30

CLR      RLY1

CLR      RLY2

LCALL    R1OFF

LCALL    R2OFF

LJMP     MAIN

R1OFF:

mov     a,#89h

lcall   com

lcall   delay

mov     a,#’O’

lcall   rata

lcall   delay

mov     a,#’F’

lcall   rata

lcall   delay

mov     a,#’F’

lcall   rata

lcall   delay

RET

R1ON:

mov     a,#89h

lcall   com

lcall   delay

mov     a,#’O’

lcall   rata

lcall   delay

mov     a,#’N’

lcall   rata

lcall   delay

mov     a,#’ ‘

lcall   rata

lcall   delay

RET

R2OFF:

mov     a,#0C9h

lcall   com

lcall   delay

mov     a,#’O’

lcall   rata

lcall   delay

mov     a,#’F’

lcall   rata

lcall   delay

mov     a,#’F’

lcall   rata

lcall   delay

RET

R2ON:

mov     a,#0C9h

lcall   com

lcall   delay

mov     a,#’O’

lcall   rata

lcall   delay

mov     a,#’N’

lcall   rata

lcall   delay

mov     a,#’ ‘

lcall   rata

lcall   delay

RET

SECS_30:MOV R4,#240D

Zz2: MOV R5,#240D

Zz1: MOV R6,#240D

DJNZ R6,$

DJNZ R5,Zz1

DJNZ R4,Zz2

RET

com:

mov     p0,a

clr     rs

setb    en

clr     en

ret

Rata:

mov     p0,a

setb    rs

setb    en

clr     en

ret

delay:

mov     r2,#20h

ll7:    mov     r3,#22h

djnz    r3,$

djnz    r2,ll7

ret

menu:

mov      dptr,#0C20h         ;welcome

mov      r6,#12h

ll81:mov      a,#00h

movc     a,@a+dptr

lcall    Rata

lcall    delay

inc      dptr

djnz     r6,ll81

mov      a,#0c0h

lcall    com

lcall    delay

mov      dptr,#0C40h         ;welcome

mov      r6,#12h

ll82:mov      a,#00h

movc     a,@a+dptr

lcall    Rata

lcall    delay

inc      dptr

djnz     r6,ll82

RET

org     0C20h

db      ‘ZONE 1:  OFF    ‘

org     0C40h

db      ‘ZONE 2:  OFF    ‘

END

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