wk 234

Improved Structure of Solar Tracker to power up

household Appliances

The Design and Implementation of a Solar Tracking Generating Power System

1

IndexTechnical Specifications --- 4

IEEE Reference Citation --- 5

Project Abstract --- 7

Project Block Diagram --- 9

Introduction --- 11

Solar Cell Description --- 13

Flowchart --- 16

Explanation of each block --- 18

AT89S52 Microcontroller --- 23

LCD Interfacing --- 34

Regulated Power Supply --- 39

DC Motor Interfacing --- 45

Stepper Motor Interfacing --- 53

Software Tools --- 55

Keil Compiler --- 54

Proload Flash --- 55

Source Code --- 58

Advantages --- 70

Applications --- 62

Conclusion --- 74

Reference --- 76


2

Tables & Diagrams

Block Diagram --- 10

Flowchart --- 17

Block Diagram of 89S52 --- 24

MCU Flash Circuit --- 32

Modes of flash programming --- 31

16X2 LCD Pin Diagram --- 36

LCD Pin Discretion --- 37

Block Diagram of Power Supply --- 41


3

Technical Specifications

Title of the project : The Design and Implementation of maximum

Power Tracking System by automatic control of

Solar panel direction according to the sun direction

(Model Sunflower)

Domain : Renewable Energy Management, Embedded

Design, Energy System

Software : Embedded C, Keil, Proload

Microcontroller : AT89S52

Power Supply : +5V, 750mA Regulated Power Supply

Display : 16 X 2 Alphanumeric LCD

Crystal : 11.0592MHz

Applications : Emergency lighting, water heaters, Hotels,

Hostels and House hold applications and

industrial applications

Developed By : M/S Wine Yard Technologies

Phone : 040-6464 6363

Website : www.WineYardProjects.com


4

IEEE Reference


5

Design and Implementation of Maximum Power Tracking System by

Automatic control of Solar Panel Direction according to the Sun

Direction (Model Sun Flower)

IEEE Reference:

A microprocessor controlled automatic sun tracker

Koyuncu, B.; Balasubramanian, K.

Consumer Electronics, IEEE Transactions on

Volume 37, Issue 4, Nov 1991 Page(s):913 - 917

Digital Object Identifier 10.1109/30.106958

Summary:

A microprocessor-based automatic sun-tracking system is proposed. This unit

controls the movement of a solar panel that rotates and follows the motion of the sun.

There are two limit switches attached to the panel to mark its maximum angular positions

in the east and west. The status of the limit switches is read by the microprocessor and

indicates that the maximum angular position in either direction has been reached and the

panel should not be driven any further. As the plane of the panel is always kept normal to

the direction of the sun, maximum thermal energy is obtained from the solar panels


6

Abstract


7

Abstract

Solar energy systems have emerged as a viable source of

renewable energy over the past two or three decades, and are now

widely used for a variety of industrial and domestic applications. Such

systems are based on a solar collector, designed to collect the sun’s

energy and to convert it into either electrical power or thermal energy.

In general, the power developed in such applications depends

fundamentally upon the amount of solar energy captured by the

collector, and thus the problem of developing tracking schemes

capable of following the trajectory of the sun throughout the course of

the day on a year-round basis has received significant coverage in this

project.

In Aden city (Yemen), the improvement in the performance of a

solar cooker during summer was found to be as much as 40% for

higher elevation angle and 70% for lower elevation angle, based on the

developed tracking algorithms. Moreover, it was shown that the

amount of solar energy captured by a tilted collector could be

increased by more than 40% by adjusting the tilt angle on a seasonal

basis.

This project is designed with AT89S52 MCU. Depending upon the light

falls on LDR the data will be read by the Microcontroller and the

direction of the motor will be changed. With this direction the Solar

plates which are fixed to the stand will also rotates to gain the

maximum sun rays.


8

This project uses regulated 12V, 500mA power supply. 7805 three terminal voltage

regulator is used for voltage regulation. Bridge type full wave rectifier is used to rectify

the ac out put of secondary of 230/12V step down transformer.

Block Diagram


9


10

Power supply to all sections

Step down T/F

Bridge Rectifier

Filter Circuit Regulator

AT89S52

Transistor Switching

Circuit

16 X 2 LCD

H BridgeDriver

DCMotor

Contrast Control

CrystalReset

High Sensitive

LDR

Transistor Switching

Circuit

High Sensitive

LDR

Mechanical Coupling to Solar Panel

Solar PanelSolar Panel Lead Acid Battery

Lead Acid Battery

InverterInverterHome

Appliances Bulb

Home Appliances

Bulb

IntroductionIntroduction


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IntroductionIntroductionThe green energy also called the regeneration energy, has gained much attention

nowadays. Green energy can be recycled, much like solar energy, water power, wind

power, biomass energy, terrestrial heat, temperature difference of sea, sea waves,

morning and evening tides, etc [1, 2]. Among these, solar energy is the most powerful

resource that can be used to generate power. So far the efficiency of generating power

from solar energy is relatively low. Thus, increasing the efficiency of generating power

of solar energy is very important. In the past, solar cells have been hooked with fixed

elevating angles. They do not track the sun and therefore, the efficiency of power

generation is low. For example, the elevating angle of a solar cell for the largest volume

of illumination in daytime is 23.5°in southern Taiwan. Since the fixed-type solar panel

can not obtain the optimal solar energy, the transformation efficiency of solar energy is

limited.

Many scholars have proposed different methods for tracking the sun [3-9]. Many

different light source sensors, light intensity sensors, intelligent vision techniques, and

CCD equipments were applied to compute the absorbed time of the sun radiation in

everyday for measuring the volume of solar energy. So far the majority of solar cell

panels worldwide are hooked with fixed angles. Thus, it is clear that the method of

tracking the sun is a technique worthy of being developed. In this paper, the main goal is

to design and implement a solar tracking control system using field programmable gate

array (FPGA). The CdS light sensitive resistors are used. From the experimental results,

the proposed tracking system is verified more efficiently in generating energy than the

fixed system.


12

SSOLAR OLAR CCELL ELL DDESCRIPTIONESCRIPTION


13

The solar cell is composed of the semiconductors of the P-N junctions [10-11]. It can

convert light into electric energy. Therefore we can assume that electricity produced

using sunlight shining on the solar cell can be used like common electricity. The

equivalent circuit of the solar cell is shown in Fig. 1. The current supply I ph represents

the electric current generated from the sun beaming on the solar cell. Rj is the non-linear

impedance of the P-N junction. Dj is a P-N junction diode, Rsh and Rs represent the

equivalent lineup with the interior of the materials and connecting resistances in series.

Usually in general analysis, Rsh is large, and the value of Rs is small. Therefore in order

to simplify the process of analysis, one can ignore Rsh and Rs . The symbol Ro represents

the external load. I and V represent the output current and the voltage of the solar cell,

respectively. From the equivalent circuit, and based on the characteristics of the P-N

junction, (1) presents the connection between the output current I and the output voltage

V :

Where np represents the parallel integer of the solar cell; ns represents the series

connected integer of the solar cell; q represents the contained electricity in an electro

(1.6×10−19 Columbic); k is the Boltzmann constant (1.38×10−23 J / °K ); T is the

temperature of the solar cell (absolute temperature °K ); and A is the ideal factor of the

solar cell ( A = 1 ~ 5 ). The current sat I in (1) represents the reversion saturation current

of the solar power. Further, sat I can be determined by using the following formula:


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Where Tr represents the reference temperature of the solar cell; Irr is the reversion

saturation current at the time when the solar cell reaches its temperature Tr ; and EGap is

the energy needed for crossing the energy band gap for the semiconductor materials. (the

crystalline EGap ≅ 1.1eV ). From the study we are able to know that when the

temperature is fixed, the stronger the sunlight is, and the higher the open-circuit voltage

and short-circuit current are. Here we can see the obvious effects of illumination on the

short-circuit current, rather than the open-circuit current. Therefore the solar cell can

provide higher output rate as the sunlight becomes stronger, i.e. solar cell facing the sun.


15

MCUMCU

Flow Chart


16


17

MCU sends a stop signal to motor

Explanation of Each BlockExplanation of Each Block


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AT89S52 MCU:

AT89S52 is 8-bit microcontroller from Atmel Semiconductors. This comes into

8051 family microcontroller. This is the heart of the project. The complete control logic

program is stored in this microcontroller. It sends and receives control and data signals to

LCD, Stepper motor and to the other Devices based on the program logic.

Solar Panel:

This is a photo voltaic cell. This converts light energy into electrical energy. The

output voltage of the solar panel depends on the amount of light falling on the panel.

Voltage Sampling Circuit:

The output voltage of the solar panel is given to voltage sampling circuit. This is a

voltage divide network. The sample voltage is given to Analog to Digital converter

circuit.

High Sensitivity LDR

This is a light dependent resistor. The resistance of the device is inversely

proportional to the amount of light falling on its surface. This is used to detect the day –

night mode.

Transistor Switching Circuit

In this section a NPN transistor is used as a switch. The transistor is driven into

saturation and cut off region based on the output voltage of the LDR. This sends a logic

HIGH or LOW signal to microcontroller.


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H-BRIDGE:

An H-bridge is an electronic circuit which enables DC electric motors to be run

forwards or backwards. These circuits are often used in robotics. H-bridges are available

as integrated circuits, or can be built from discrete components.

DC Motor

The DC motor is used to rotate the solar panel. The DC motor makes actual and

exact number of turns or degrees of rotation instructed by the microcontroller.

16X2 LCD:

16 X 2 LCD is used to display the operating instructions and status of the output.

HD44780U is used in the project. The HD44780U dot-matrix liquid crystal display

controller and driver LSI displays alphanumeric, Japanese kana characters, and symbols.

It can be configured to drive a dot-matrix liquid crystal display under the control of a 4-

or 8-bit microprocessor. Since all the functions such as display RAM, character

generator, and liquid crystal driver, required for driving a dot-matrix liquid crystal

display are internally provided on one chip, a minimal system can be interfaced with this


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controller/driver. A single HD44780U can display up to one 8-character line or two 8-

character lines. The HD44780U has pin function compatibility with the HD44780S which

allows the user to easily replace an LCD-II with an HD44780U. The HD44780U

character generator ROM is extended to generate 208 5X8 dot character fonts and 32

5X10 dot character fonts for a total of 240 different character fonts.

Contrast Control:

It is a simple variable resistor (preset) with linear characteristics. This is used to adjust

the contrast of the display.


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Reset:

Reset control circuit is used to reset the microcontroller at any stage of work. This

section also comprises of auto power on reset. If the reset switch is pressed, the

microcontroller restarts and the function will start from the begin. This circuit is

connected to 9th pin of microcontroller.

Crystal:

A crystal is used to supply clock frequency to the microcontroller. The clock

frequency is 11.0592MHz. 11.0592 MHz crystals are often used because it can be

divided to give you exact clock rates for most of the common baud rates for the

UART, especially for the higher speeds (9600, 19200). Despite the "oddball" value, these

crystals are readily available and commonly used.

Power Supply Section:

This project needs 5V regulated DC power supply. This power supply is built

with a full wave bridge rectifier, C- filter and a three terminal voltage regulator. An LED

is provided for visual identification of the power supply. 230V / 18V step down

transformer is used to step down the AC 230 V to 18V AC.

Fig13: Power supply


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RegulatorFilterBridge Rectifier

Step down transformer

230V AC 50Hz

D.C Output

AT89S52 Microcontroller


23

Description

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller

with 8K bytes of in-system programmable Flash memory. The device is manufactured

using Atmel’s high-density nonvolatile memory technology and is compatible with the

indus-try-standard 89S52 instruction set and pinout.

The on-chip Flash allows the program memory to be reprogrammed in-system or

by a conventional nonvolatile memory pro-grammer. By combining a versatile 8-bit CPU

with in-system programmable Flash on a monolithic chip, the Atmel AT89S52 is a

powerful microcontroller which provides a highly-flexible and cost-effective solution to

many embedded control applications.

The AT89S52 provides the following standard features: 8K bytes of Flash, 256

bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit

timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-

chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic

for operation down to zero frequency and supports two software selectable power saving

modes.

The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial

port, and interrupt system to continue functioning. The Power-down mode saves the

RAM con-tents but freezes the oscillator, disabling all other chip functions until the next

interrupt or hardware reset.


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Pin Configuration


25

Block Diagram


26

Pin Description

Port 0 :

Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each pin can

sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-

impedance inputs. Port 0 can also be configured to be the multiplexed low-order

address/data bus during accesses to external program and data memory. In this mode, P0

has internal pull-ups. Port 0 also receives the code bytes during Flash programming and

outputs the code bytes dur-ing program verification. External pull-ups are required

during program verification.

Port 1:

Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output

buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are

pulled high by the inter-nal pull-ups and can be used as inputs. As inputs, Port 1 pins that

are externally being pulled low will source current (IIL) because of the internal pull-ups.

In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count

input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown

in the follow-ing table. Port 1 also receives the low-order address bytes during Flash

programming and verification.


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Port 2




are externally being pulled low will source current (IIL) because of the internal pull-ups.

Port 2 emits the high-order address byte during fetches from external program memory

and dur-ing accesses to external data memory that use 16-bit addresses (MOVX @

DPTR). In this application, Port 2 uses strong internal pull-ups when emitting 1s. During

accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits

the contents of the P2 Special Function Register. Port 2 also receives the high-order

address bits and some control signals during Flash programming and verification.

Port 3:




are externally being pulled low will source current (IIL) because of the pull-ups. Port 3

receives some control signals for Flash programming and verification. Port 3 also serves

the functions of various special features of the AT89S52, as shown in the fol-lowing

table.

RST:

Reset input. A high on this pin for two machine cycles while the oscillator is

running resets the device. This pin drives high for 98 oscillator periods after the

Watchdog times out. The DISRTO bit in SFR AUXR (address 8EH) can be used to

disable this feature. In the default state of bit DISRTO, the RESET HIGH out feature is

enabled.

ALE/PROG:

Address Latch Enable (ALE) is an output pulse for latching the low byte of the

address during accesses to external memory. This pin is also the program pulse input


28

(PROG) during Flash programming. In normal operation, ALE is emitted at a constant

rate of 1/6 the oscillator frequency and may be used for external timing or clocking

purposes. Note, however, that one ALE pulse is skipped dur-ing each access to external

data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location

8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction.

Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the

microcontroller is in external execution mode.

PSEN:

Program Store Enable (PSEN) is the read strobe to external program memory.

When the AT89S52 is executing code from external program memory, PSEN is activated

twice each machine cycle, except that two PSEN activations are skipped during each

access to exter-nal data memory.

EA/VPP:

External Access Enable. EA must be strapped to GND in order to enable the

device to fetch code from external program memory locations starting at 0000H up to

FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on

reset. EA should be strapped to VCC for internal program executions. This pin also

receives the 12-volt programming enable voltage (VPP) during Flash programming.

XTAL1:

Input to the inverting oscillator amplifier and input to the internal clock operating

circuit.

XTAL2 :

Output from the inverting oscillator amplifier.


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PROGRAMMING THE FLASH:

The AT89S52 is normally shipped with the on-chip Flash memory array in the

erased state (that is, contents = FFH) and ready to be programmed. The programming

interface accepts either a high-voltage (12-volt) or a low-voltage (VCC) program enable

signal. The low-voltage programming mode provides a convenient way to program the

AT89S52 inside the user’s system, while the high-voltage programming mode is

compatible with conventional third party Flash or EPROM programmers. The AT89S52

is shipped with either the high-voltage or low-voltage programming mode enabled. The

respective top-side marking and device signature codes are listed in the following table.

The AT89S52 code memory array is programmed byte-byte in either

programming mode. To program any nonblank byte in the on-chip Flash Memory, the

entire memory must be erased using the Chip Erase Mode.

Programming Algorithm:

Before programming the AT89S52, the address, data and control signals should

be set up according to the Flash programming mode table. To program the AT89S52, the

following steps should be considered:

1. Input the desired memory location on the address lines.

2. Input the appropriate data byte on the data lines.


30

3. Activate the correct combination of control signals.

4. Raise EA/VPP to 12V for the high-voltage programming mode.

5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-

write cycle is self-timed and typically takes no more than 1.5 ms.

Repeat steps 1 through 5, changing the address and data for the entire array or until the

end of the object file is reached.

Data Polling:

The AT89S52 features Data Polling to indicate the end of a write cycle. During a

write cycle, an attempted read of the last byte written will result in the complement of the

written datum on PO.7. Once the write cycle has been completed, true data are valid on

all outputs, and the next cycle may begin. Data Polling may begin any time after a write

cycle has been initiated.

Ready/Busy:

The progress of byte programming can also be monitored by the RDY/BSY

output signal. P3.4 is pulled low after ALE goes high during programming to indicate

BUSY. P3.4 is pulled high again when programming is done to indicate READY.

Chip Erase:

The entire Flash array is erased electrically by using the proper combination of

control signals and by holding ALE/PROG low for 10 ms. The code array is written with

all “1”s. The chip erase operation must be executed before the code memory can be re-

programmed.

Reading the Signature Bytes: The signature bytes are read by the same procedure as a

normal verification of locations 030H, 031H, and 032H, except that P3.6 and P3.7 must

be pulled to a logic low. The values returned are as follows.


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(030H) = 1EH indicates manufactured by Atmel

(031H) = 51H indicates 89S52

(032H) = FFH indicates 12V programming

(032H) = 05H indicates 5V programming

Programming Interface:

Every code byte in the Flash array can be written and the entire array can be

erased by using the appropriate combination of control signals. The write operation cycle

is self timed and once initiated, will automatically time itself to completion. All major

programming vendors offer worldwide support for the Atmel microcontroller series.

Tables: Flash Programming Modes


32


33

Fig: Programming and Verifying the Flash


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LCD Interfacing

Description:

The HD44780U dot-matrix liquid crystal display controller and driver LSI

displays alphanumerics, Japanese kana characters, and symbols. It can be configured to

drive a dot-matrix liquid crystal display under the control of a 4- or 8-bit microprocessor.

Since all the functions such as display RAM, character generator, and liquid crystal

driver, required for driving a dot-matrix liquid crystal display are internally provided on

one chip, a minimal system can be interfaced with this controller/driver. A single

HD44780U can display up to one 8-character line or two 8-character lines. The

HD44780U has pin function compatibility with the HD44780S which allows the user to

easily replace an LCD-II with an HD44780U. The HD44780U character generator ROM

is extended to generate 208 5 X 8 dot character fonts and 32 5 X 10 dot character fonts

for a total of 240 different character fonts. The low power supply (2.7V to 5.5V) of the

HD44780U is suitable for any portable battery-driven product requiring low power

dissipation.

The most commonly used Character based LCD’s are based on Hitachi's

HD44780 controller or other which are compatible with HD44580. In this tutorial, we

will discuss about character based LCD’s, their interfacing with various microcontrollers,

various interfaces (8-bit/4-bit), programming, special stuff and tricks you can do with

these simple looking LCD’s which can give a new look to your application.

Pin Description:

The most commonly used LCD’s found in the market today are 1 Line, 2 Line or

4 Line LCD’s which have only 1 controller and support at most of 80 charachers, where

as LCD’s supporting more than 80 characters make use of 2 HD44780 controllers.

Most LCD’s with 1 controller has 14 Pins and LCD’s with 2 controller has 16 Pins (two

pins are extra in both for back-light LED connections). Pin description is shown in the

table below.


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Fig10: LCD Pin Diagram

Table 1: Character LCD pins with 1 Controller

Pin No. Name Description

Pin no. 1 D7 Data bus line 7 (MSB)Pin no. 2 D6 Data bus line 6Pin no. 3 D5 Data bus line 5Pin no. 4 D4 Data bus line 4


Pin no. 1 VSS Power supply (GND)Pin no. 2 VCC Power supply (+5V)Pin no. 3 VEE Contrast adjust

Pin no. 4 RS0 = Instruction input1 = Data input

Pin no. 5 R/W0 = Write to LCD module1 = Read from LCD module

Pin no. 6 EN Enable signalPin no. 7 D0 Data bus line 0 (LSB)Pin no. 8 D1 Data bus line 1Pin no. 9 D2 Data bus line 2Pin no. 10 D3 Data bus line 3Pin no. 11 D4 Data bus line 4Pin no. 12 D5 Data bus line 5Pin no. 13 D6 Data bus line 6Pin no. 14 D7 Data bus line 7 (MSB)

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Pin no. 5 D3 Data bus line 3Pin no. 6 D2 Data bus line 2Pin no. 7 D1 Data bus line 1Pin no. 8 D0 Data bus line 0 (LSB)

Pin no. 9 EN1Enable signal for row 0 and 1 (1stcontroller)

Pin no. 10 R/W0 = Write to LCD module1 = Read from LCD module

Pin no. 11 RS0 = Instruction input1 = Data input

Pin no. 12 VEE Contrast adjustPin no. 13 VSS Power supply (GND)Pin no. 14 VCC Power supply (+5V)

Pin no. 15 EN2Enable signal for row 2 and 3 (2ndcontroller)

Pin no. 16 NC Not Connected

Table 2: Character LCD pins with 2 Controller

Sending Commands to LCD

To send commands we simply need to select the command register. Everything is same as we have done in the initialization routine. But we will summarize the common steps and put them in a single subroutine. Following are the steps:

Move data to LCD port select command register select write operation send enable signal wait for LCD to process the command

CODE:void LCD_command(unsigned char var){ LCD_data = var; //Function set: 2 Line, 8-bit, 5x7 dots LCD_rs = 0; //Selected command register LCD_rw = 0; //We are writing in instruction register LCD_en = 1; //Enable H->L LCD_en = 0; LCD_busy(); //Wait for LCD to process the command}// Using the above function is really simple// var will carry the command for LCD// e.g.


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//// LCD_command(0x01);

Sending Data to LCD

To send data we simply need to select the data register. Everything is same as the command routine. Following are the steps:

Move data to LCD port select data register select write operation send enable signal wait for LCD to process the data

Keeping these steps in mind we can write LCD command routine as.

CODE:void LCD_senddata(unsigned char var){ LCD_data = var; //Function set: 2 Line, 8-bit, 5x7 dots LCD_rs = 1; //Selected data register LCD_rw = 0; //We are writing LCD_en = 1; //Enable H->L LCD_en = 0; LCD_busy(); //Wait for LCD to process the command}// Using the above function is really simple// we will pass the character to display as argument to function// e.g.//// LCD_senddata('A');


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Power Supply Design


39

POWER SUPPLY:

The input to the circuit is applied from the regulated power supply. The a.c. input

i.e., 230V from the mains supply is step down by the transformer to 12V and is fed to a

rectifier. The output obtained from the rectifier is a pulsating d.c voltage. So in order to

get a pure d.c voltage, the output voltage from the rectifier is fed to a filter to remove any

a.c components present even after rectification. Now, this voltage is given to a voltage

regulator to obtain a pure constant dc voltage.

Fig: Power supply


40

RegulatorFilterBridge Rectifier

Step down transformer

230V AC 50Hz

D.C Output

Transformer:

Usually, DC voltages are required to operate various electronic equipment and

these voltages are 5V, 9V or 12V. But these voltages cannot be obtained directly. Thus

the a.c input available at the mains supply i.e., 230V is to be brought down to the

required voltage level. This is done by a transformer. Thus, a step down transformer is

employed to decrease the voltage to a required level.

Fig11: Transformer

Rectifier:

The output from the transformer is fed to the rectifier. It converts A.C. into

pulsating D.C. The rectifier may be a half wave or a full wave rectifier. In this project, a

bridge rectifier is used because of its merits like good stability and full wave rectification.

The Bridge rectifier is a circuit, which converts an ac voltage to dc voltage using

both half cycles of the input ac voltage. The Bridge rectifier circuit is shown in the figure.


41

The circuit has four diodes connected to form a bridge. The ac input voltage is applied to

the diagonally opposite ends of the bridge. The load resistance is connected between the

other two ends of the bridge.

Fig 12: Rectifier Circuit

For the positive half cycle of the input ac voltage, diodes D1 and D3 conduct,

whereas diodes D2 and D4 remain in the OFF state. The conducting diodes will be in

series with the load resistance RL and hence the load current flows through RL.

For the negative half cycle of the input ac voltage, diodes D2 and D4 conduct

whereas, D1 and D3 remain OFF. The conducting diodes D2 and D4 will be in series

with the load resistance RL and hence the current flows through RL in the same direction

as in the previous half cycle. Thus a bi-directional wave is converted into a unidirectional

wave.


42

Fig13: Rectifier output Waveforms


43

Filter:

Capacitive filter is used in this project. It removes the ripples from the output of rectifier

and smoothens the D.C. Output received from this filter is constant until the mains

voltage and load is maintained constant. However, if either of the two is varied, D.C.

voltage received at this point changes. Therefore a regulator is applied at the output stage.

Voltage regulator:

As the name itself implies, it regulates the input applied to it. A voltage regulator

is an electrical regulator designed to automatically maintain a constant voltage level. In

this project, power supply of 5V and

12V are required. In order to obtain

these voltage levels, 7805 and 7812

voltage regulators are to be used.

The first number 78 represents

positive supply and the numbers 05,

12 represent the required output voltage levels. The L78xx series of three-terminal

positive regulators is available in TO-220, TO-220FP, TO-3, D2PAK and DPAK

packages and several fixed output voltages, making it useful in a wide range of

applications. These regulators can provide local on-card regulation, eliminating the

distribution problems associated with single point regulation. Each

type employs internal current limiting, thermal shut-down and safe

area protection, making it essentially indestructible. If adequate heat

sinking is provided, they can deliver over 1 A output current. Although

designed primarily as fixed voltage regulators, these devices can be

used with external components to obtain adjustable voltage and

currents.


44

DC Motor Interfacing


45

BASICS OF DC MOTOR

The speed of a DC motor is directly proportional to the supply voltage, so if we

reduce the supply voltage from 12 Volts to 6 Volts, the motor will run at half the speed.

How can this be achieved when the battery is fixed at 12 Volts? The speed controller

works by varying the average voltage sent to the motor. It could do this by simply

adjusting the voltage sent to the motor, but this is quite inefficient to do. A better way is

to switch the motor's supply on and off very quickly. If the switching is fast enough, the

motor doesn't notice it, it only notices the average effect.

When you watch a film in the cinema, or the television, what you are actually

seeing is a series of fixed pictures, which change rapidly enough that your eyes just see

the average effect - movement. Your brain fills in the gaps to give an average effect.

Now imagine a light bulb with a switch. When you close the switch, the bulb

goes on and is at full brightness, say 100 Watts. When you open the switch it goes off (0

Watts). Now if you close the switch for a fraction of a second, then open it for the same

amount of time, the filament won't have time to cool down and heat up, and you will just

get an average glow of 50 Watts. This is how lamp dimmers work, and the same principle

is used by speed controllers to drive a motor. When the switch is closed, the motor sees

12 Volts, and when it is open it sees 0 Volts. If the switch is open for the same amount of

time as it is closed, the motor will see an average of 6 Volts, and will run more slowly

accordingly. The graph below shows the speed of a motor that is being turned on and off

H-BRIDGE:

An H-bridge is an electronic circuit which enables DC electric motors to be run

forwards or backwards. These circuits are often used in robotics. H-bridges are available

as integrated circuits, or can be built from discrete components.


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Fig14: H-Bridge Circuit

The two basic states of an H-bridge.The term "H-bridge" is derived from the

typical graphical representation of such a circuit. An H-bridge is built with four switches

(solid-state or mechanical). When the switches S1 and S4 (according to the first figure)

are closed (and S2 and S3 are open) a positive voltage will be applied across the motor.

By opening S1 and S4 switches and closing S2 and S3 switches, this voltage is reversed,

allowing reverse operation of the motor.

Using the nomenclature above, the switches S1 and S2 should never be closed at

the same time, as this would cause a short circuit on the input voltage source. The same

applies to the switches S3 and S4. This condition is known as shoot-through.

Operation

The H-Bridge arrangement is generally used to reverse the polarity of the motor,

but can also be used to 'brake' the motor, where the motor comes to a sudden stop, as the

motors terminals are shorted, or to let the motor 'free run' to a stop, as the motor is

effectively disconnected from the circuit. The following table summarizes operation.


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S1 S2 S3 S4 Result

1 0 0 1 Motor moves right

0 1 1 0 Motor moves left

0 0 0 0 Motor free runs

0 1 0 1 Motor brakes

H-Bridge Driver:

The switching property of this H-Bridge can be replaced by a Transistor or a

Relay or a MOSFET or even by an IC. Here we are replacing this with an IC named

L293D as the driver whose description is as given below.

Features:

600mA OUTPUT CURRENT CAPABILITY

PER CHANNEL

1.2A PEAK OUTPUT CURRENT (non repetitive)

PER CHANNEL

ENABLE FACILITY

OVERTEMPERATURE PROTECTION

LOGICAL "0" INPUT VOLTAGE UP TO 1.5 V

(HIGH NOISE IMMUNITY)

INTERNAL CLAMP DIODES


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DESCRIPTION:

The Device is a monolithic integrated high voltage, high current four channel

driver designed to accept standard DTL or TTL logic levels and drive inductive loads

(such as relays solenoids, DC and stepping motors) and switching power transistors. To

simplify use as two bridges each pair of channels is equipped with an enable input. A

separate supply input is provided for the logic, allowing operation at a lower voltage and

internal clamp diodes are included. This device is suitable for use in switching

applications at frequencies up to 5 kHz. The L293D is assembled in a 16 lead plastic

package which has 4 center pins connected together and used for heat sinking The

L293DD is assembled in a 20 lead surface mount which has 8 center pins connected

together and used for heat sinking.

BLOCK DIAGRAM

Fig: Block Diagram of H-Bridge


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ABSOLUTE MAXIMUM RATINGS:

PIN CONNECTIONS:

Fig: Pin Diagram of L293D H-Bridge


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LIGHT DEPENDENT RESISTOR:

An LDR is an input transducer (sensor) which converts

brightness (light) to

resistance. It is made from

cadmium

sulphide (CdS) and the

resistance

decreases as the

brightness of

light falling on the

LDR increases.

LDR’s or Light Dependent Resistors are very

useful especially in light/dark sensor

circuits. Normally the resistance of an LDR is very high, sometimes as high as 1,000,000

ohms, but when they are illuminated with light, the resistance drops dramatically.

Thus in this project, LDR plays an important role in controlling the electrical

appliances based on the intensity of light i.e., if the intensity of light is more (during

daytime) the loads will be in off condition. And if the intensity of light is less (during

nights), the loads will be switched on.


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Fig:

In the above circuit we are controlling the load with an LDR device which in turn

depends on the transistor and a switch i.e., nothing but the operation of the above circuit

behaves like a transistor as a switch.

A transistor is a semi conductor device commonly used to amplify or switch electronic

signals.

In electronics, a switch is an electrical component that can break an electrical circuit,

interrupting the current or diverting it from one conductor to another.

• Transistor can be used as an electronic switch, in grounded-emitter configuration.

• Transistors are commonly used as electronic switches, for both high power

applications including switched mode power supply and low power applications

such as logic gates.

• In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as

the base voltage rises the base and collector current rise exponentially, and the

collector voltage drops because of the collector load resistor.

• If the emitter-base and base-collector are in forward bias then it act as a switch.

• At that instant the collector to emitter is shorted, it act as a closed switch.


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LEAD ACID BATTERY


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Lead-acid batteries are the most common in PV systems because their initial cost is

lower and because they are readily available nearly everywhere in the world. There are

many different sizes and designs of lead-acid batteries, but the most important

designation is that they are deep cycle batteries. Lead-acid batteries are available in both

wet-cell (requires maintenance) and sealed no-maintenance versions. AGM and Gel-cell

deep-cycle batteries are also popular because they are maintenance free and they last a lot

longer.

Lead acid batteries are reliable and cost effective with an exceptionally long life.

The Lead acid batteries have high reliability because of their ability to withstand

overcharge, over discharge vibration and shock. The use of special sealing techniques

ensures that our batteries are leak proof and non-spillable. Other critical features include

the ability to withstand relatively deeper discharge, faster recovery and more chances of

survival if subjected to overcharge. The batteries have exceptional charge acceptance,

large electrolyte volume and low self-discharge, which make them ideal as zero-

maintenancebatteries.

Lead acid batteries are manufactured/ tested using CAD (Computer Aided

Design). These batteries are used in Inverter & UPS Systems and have the proven ability

to perform under extreme conditions. The batteries have electrolyte volume, use PE

Separators and are sealed in sturdy containers, which give them excellent protection

against leakage and corrosion.

Features

Manufactured/tested using CAD

Electrolyte volume

PE Separators

Protection against leakage


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Number of batteries needed:

If you use the numbers from the sample load numbers link at the end of the page,

you turn out needing 6310W peak and a total of 20950Wh/day. This comes out at 51

Amps peak and a total of 174 Amp Hours in a day at 120 Volts. To handle these peak

loads, it is important to use electrical wiring of the correct gauge to carry the current. 51

Amps @ 120 Volts (or 526 Amps@12vDC) is hazardous. One should not forget that

batteries have a limited life span. Any system should be designed such that you can easily

replace batteries without disrupting much of your load. You may need to diagnose to

determine what batteries have lost their ability to retain a charge.

Battery connections:

Lead-acid batteries are normally available in blocks of 2V, 6V or 12V. In most

cases, to generate the necessary operating voltage and the capacity of the batteries for the

Solar Inverter, many batteries have to be connected together in parallel and/or in series.

Following three examples are shown:

Parallel Connection:


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Series Connection:


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Parallel-Series Connection:


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INVERTER


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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.

Solid-state 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.

There are two main types of inverter. The output of a modified sine wave inverter

is similar to a square wave output except that the output goes to zero volts for a time

before switching positive or negative. It is simple and low cost and is compatible with

most electronic devices, except for sensitive or specialized equipment, for example

certain laser printers. A pure sine wave inverter produces a nearly perfect sine wave

output (<3% total harmonic distortion) that is essentially the same as utility-supplied grid

power. Thus it is compatible with all AC electronic devices. This is the type used in grid-

tie inverters. Its design is more complex, and costs 5 or 10 times more per unit

power. 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.


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http://en.wikipedia.org/wiki/Rectifier

http://en.wikipedia.org/wiki/Mechanical_rectifier

http://en.wikipedia.org/wiki/Electronic_oscillator

http://en.wikipedia.org/wiki/Total_harmonic_distortion

http://en.wikipedia.org/wiki/Laser_printer

http://en.wikipedia.org/wiki/Square_wave

http://en.wikipedia.org/wiki/Battery_(electrical)

http://en.wikipedia.org/wiki/Solar_panel

http://en.wikipedia.org/wiki/High-voltage_direct_current

http://en.wikipedia.org/wiki/Electric_utility

http://en.wikipedia.org/wiki/Electric_utility

http://en.wikipedia.org/wiki/Switched-mode_power_supply

http://en.wikipedia.org/wiki/Alternating_current

http://en.wikipedia.org/wiki/Alternating_current

http://en.wikipedia.org/wiki/Direct_current

Software Tools


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KEIL SOFTWARE:

Keil compiler is a software used where the machine language code is written and

compiled. After compilation, the machine source code is converted into hex code which

is to be dumped into the microcontroller for further processing. Keil compiler also

supports C language code.

STEPS TO WRITE AN ASSEMBLY LANGUAGE PROGRAM IN KEIL AND

HOW TO COMPILE IT:

1. Install the Keil Software in the PC in any of the drives.

2. After installation, an icon will be created with the name “Keil uVision3”. Just

drag this icon onto the desktop so that it becomes easy whenever you try to write

programs in keil.

3. Double click on this icon to start the keil compiler.

4. A page opens with different options in it showing the project workspace at the

leftmost corner side, output window in the bottom and an ash coloured space for

the program to be written.

5. Now to start using the keil, click on the option “project”.

6. A small window opens showing the options like new project, import project, open

project etc. Click on “New project”.

7. A small window with the title bar “Create new project” opens. The window asks

the user to give the project name with which it should be created and the

destination location. The project can be created in any of the drives available. You

can create a new folder and then a new file or can create directly a new file.


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8. After the file is saved in the given destination location, a window opens where a

list of vendors will be displayed and you have to select the device for the target

you have created.

9. The most widely used vendor is Atmel. So click on Atmel and now the family of

microcontrollers manufactured by Atmel opens. You can select any one of the

microcontrollers according to the requirement.

10. When you click on any one of the microcontrollers, the features of that particular

microcontroller will be displayed on the right side of the page. The most

appropriate microcontroller with which most of the projects can be implemented

is the AT89S52. Click on this microcontroller and have a look at its features. Now

click on “OK” to select this microcontroller.

11. A small window opens asking whether to copy the startup code into the file you

have created just now. Just click on “No” to proceed further.

12. Now you can see the TARGET and SOURCE GROUP created in the project

workspace.

13. Now click on “File” and in that “New”. A new page opens and you can start

writing program in it.

14. After the program is completed, save it with any name but with the .asm

extension. Save the program in the file you have created earlier.

15. You can notice that after you save the program, the predefined keywords will be

highlighted in bold letters.

16. Now add this file to the target by giving a right click on the source group. A list of

options open and in that select “Add files to the source group”. Check for this file

where you have saved and add it.

17. Right click on the target and select the first option “Options for target”. A window

opens with different options like device, target, output etc. First click on “target”.


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18. Since the set frequency of the microcontroller is 11.0592 MHz to interface with

the PC, just enter this frequency value in the Xtal (MHz) text area and put a tick

on the Use on-chip ROM. This is because the program what we write here in the

keil will later be dumped into the microcontroller and will be stored in the inbuilt

ROM in the microcontroller.

19. Now click the option “Output” and give any name to the hex file to be created in

the “Name of executable” text area and put a tick to the “Create HEX file” option

present in the same window. The hex file can be created in any of the drives. You

can change the folder by clicking on “Select folder for Objects”.

20. Now to check whether the program you have written is errorless or not, click on

the icon exactly below the “Open file” icon which is nothing but Build Target

icon. You can even use the shortcut key F7 to compile the program written.

21. To check for the output, there are several windows like serial window, memory

window, project window etc. Depending on the program you have written, select

the appropriate window to see the output by entering into debug mode.

22. The icon with the letter “d” indicates the debug mode.

23. Click on this icon and now click on the option “View” and select the appropriate

window to check for the output.

24. After this is done, click the icon “debug” again to come out of the debug mode.

25. The hex file created as shown earlier will be dumped into the microcontroller with

the help of another software called Proload.


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PROLOAD:

Proload is a software which accepts only hex files. Once the machine code is

converted into hex code, that hex code has to be dumped into the microcontroller placed

in the programmer kit and this is done by the Proload. Programmer kit contains a

microcontroller on it other than the one which is to be programmed. This microcontroller

has a program in it written in such a way that it accepts the hex file from the keil

compiler and dumps this hex file into the microcontroller which is to be programmed. As

this programmer kit requires power supply to be operated, this power supply is given

from the power supply circuit designed above. It should be noted that this programmer kit

contains a power supply section in the board itself but in order to switch on that power

supply, a source is required. Thus this is accomplished from the power supply board with

an output of 12volts or from an adapter connected to 230 V AC.

Steps to work with Proload:

1. Install the Proload Software in the PC.

2. Now connect the Programmer kit to the PC (CPU) through serial cable.

3. Power up the programmer kit from the ac supply through adapter.

4. Now place the microcontroller in the GIF socket provided in the programmer kit.

5. Click on the Proload icon in the PC. A window appears providing the information

like Hardware model, com port, device type, Flash size etc. Click on browse

option to select the hex file to be dumped into the microcontroller and then click

on “Auto program” to program the microcontroller with that particular hex file.

6. The status of the microcontroller can be seen in the small status window in the

bottom of the page.


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7. After this process is completed, remove the microcontroller from the programmer

kit and place it in your system board. Now the system board behaves according to

the program written in the microcontroller.

ADVANTAGESADVANTAGES


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Advantages:

Highly sensitive

Works according to the sun direction

Fit and Forget system

Night – Day mode sensing

Low cost and reliable circuit

Complete elimination of manpower


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APPLICATIONSAPPLICATIONS


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Applications:

Street lights

Garden Lights

Solar water heater

Hotels, hostels and house hold applications

Offices

Industries


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CCONCLUSIONONCLUSION


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CONCLUSION

This project presents a solar tracking power generation system. The tracking

controller based on the closed loop algorithm is designed and implemented with Atmel

89S52 MCU in embedded system domain. Set up on the solar tracking system, the light

sensitivity resistors are used to determine the night – day vision. The proposed solar

tracking power generation system can track the sun light automatically. Thus, the

efficiency of solar energy generation can be increased. Experimental work has been

carried out carefully. The result shows that higher generating power efficiency is indeed

achieved using the solar tracking system. The proposed method is verified to be highly

beneficial for the solar power generation.


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REFERENCEREFERENCE


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REFERENCE

Text Books:

Website:

www.howstuffworks.com

www.answers.com

www.radiotronix.com

www.WineYardProjects.com

Magazines:

Electronics for you

Electrikindia


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wk 234

Documents

Transcript of wk 234