Transformer Protection From Over Load

And Monitoring of Load current in PC

ABSTRACT

The aim of the project work is to protect the distribution transformer or any other power

transformer, burning due to the overload. Normally most of the transformers are burning

because of over load; hence by incorporating monitoring and control circuits, life of the

transformer can be.

In this project we designed a system in such a way that it will monitor the load of the

transformer continuously and that information is transferred to the control room. In the main

station these parameters are displayed on the PC monitor. In the display unit we can view the

continuous information of transformer i.e. due to what reason the transformer has been failed,

when the power is resumed etc.,. With the help of this kind of system, the maintenance staff

of the department can have a continuous vigilance over the transformer.

In this project work, for the demonstration purpose a small step-down transformer of 12V, 1

amps rating at secondary is considered and small bulbs are connected as a load. In this

project we are using CT transformer for measuring load current. All these parameters are

converted into digital value by using ADC. If the parameters of the transformer (Current)

regain the limited range values then Transformer will automatically shutdown.

Microcontroller near the transformer section will continuously transmit all the parameters of

the transformer to PC of control room.

HARDWARE COMPONENTS:

Microcontroller

Power supply

Relay

Loads

ADC 0804

Current Transformer

PC

SOFTWARE TOOLS:

Keil micro vision

Embedded C

Express PCB

Applications:

This project is used for protecting Transformers in sub stations, generating stations etc.

Used for Industrial protection

BLOCK DIAGRAM:

Microcontroller

Power supply

Transformer

CT

ADC

RELAY

PC

LOAD

INDEX

CONTENTS

Abbreviations

1. Figure Locations2. Introduction to the project3. Block Diagram4. Block Diagram Description5. Schematic6. Schematic Description7. Hardware Components

Micro controllers ADC 0804 Relay Power Supply

8. Circuit Description9. Software components

a. About Keilb. Embedded ‘C’

10. Conclusion (or) Synopsis

11.Future Aspects

Bibliography

Abbreviations:

ACC - Accumulator

B - B Register

PSW - Program Status Word

SP - Stack Pointer

DPTR - Data pointer

DPL - Low byte

DPH - High byte

P0 - Port 0

P1 - Port 1

P2 - Port 2

P3 - Port 3

IE - Interrupt Enable control

IP - Interrupt Priority control

TMOD - Timer/Counter Mode control

TCON - Timer/Counter control

T2CON - Timer/counter 2 control

T2MOD - Timer/counter mode2 control

TH0 - Timer/counter 0high byte

TL0 - Timer/counter 0 low byte

TH1 - Timer/counter 1 high byte

TL1 - Timer/counter 1 low byte

TH2 - Timer/counter 2 high byte

TL2 - Timer/counter 2 low byte

RCAP2H - T/C 2 capture register high byte

RCAP2L - T/C 2 capture register low byte

SCON - Serial control

SBUF - Serial data buffer

PCON - Power control

PCB - Printed circuit Board

AGC - Automatic Gain Control

RF - Radio Frequency

HT - Holtek’s Company

LCD - Liquid Crystal Display

IR - Infrared Radio Frequency

INTRODUCTION:

EMBEDDED SYSTEM:

An embedded system is a special-purpose system in which the computer is completely

encapsulated by or dedicated to the device or system it controls. Unlike a general-purpose computer,

such as a personal computer, an embedded system performs one or a few predefined tasks, usually with

very specific requirements. Since the system is dedicated to specific tasks, design engineers can optimize

it, reducing the size and cost of the product. Embedded systems are often mass-produced, benefiting

from economies of scale.

Personal digital assistants (PDAs) or handheld computers are generally considered embedded

devices because of the nature of their hardware design, even though they are more expandable in

software terms. This line of definition continues to blur as devices expand. With the introduction of the

OQO Model 2 with the Windows XP operating system and ports such as a USB port — both features

usually belong to "general purpose computers", — the line of nomenclature blurs even more.

Physically, embedded systems ranges from portable devices such as digital watches and MP3

players, to large stationary installations like traffic lights, factory controllers, or the systems controlling

nuclear power plants.

In terms of complexity embedded systems can range from very simple with a single

microcontroller chip, to very complex with multiple units, peripherals and networks mounted inside a

large chassis or enclosure.

Examples of Embedded Systems:

Avionics, such as inertial guidance systems, flight control hardware/software and other

integrated systems in aircraft and missiles

Cellular telephones and telephone switches

Engine controllers and antilock brake controllers for automobiles

Home automation products, such as thermostats, air conditioners, sprinklers, and security

monitoring systems

Handheld calculators

Handheld computers

Household appliances, including microwave ovens, washing machines, television sets,

DVD players and recorders

Medical equipment

Personal digital assistant

Videogame consoles

Computer peripherals such as routers and printers.

Industrial controllers for remote machine operation.

BLOCK DIAGRAM:

EXPLANATION:

Power supply:

In this system we are using 5V power supply for microcontroller of Transmitter section

as well as receiver section. We use rectifiers for converting the A.C. into D.C and a step down

transformer to step down the voltage. The full description of the Power supply section is given in this

documentation in the following sections i.e. hardware components.

Microcontroller:

In this project the microcontroller plays a major role, here micro controller scan the output of

current transformer through adc and send respective signals to PC and PC displays the status of the

transformer under test in monitor..

Microcontroller

Power supply

Transformer

CT

ADC

RELAY

PC

LOAD

ADC0804:

The output of the current transformer connected to adc0804. Actually current transformer is an analog devise, so the output will be in analog form but the microcontroller not understanding the analog values. So, we need to convert the analog output into digital form. ADC0804 performs the conversion to digital from analog. ADC0804 is a 8 bit converter.

Relay:

It is used as electro mechanical switch.

Current transformer:

It is used to measure the load on transformer. And the output of this transformer is connected to ADC. Because it is analog device and the output is in the form of analog variable. So, we need to convert it to digital.

SCHEMATIC:

EXPLANATION:

Aim of our project is continuously monitor of the transformer and if any load on that transformer increases we protect that transformer. In this project we make use of PC, Micro controller, Transformer under test and relay.

In this project current transformer acts as input. We are connecting the output of current transformer to 6th pin of ADC0804. The 6th pin of ADC0804 acts as analog input.

In this project PC acts as output. And PC is connected to microcontroller through RS232. We use MAX232 IC to interface RS232 to uc. The RX and TX pin means 2nd and 3rd pins of RS232 is connected to 14 and 13th pins of MAX232. 11th and 12th pins of MAX232 is connected to 10th and 11th pins of controller. 10th and 11th pins of controller are P3.0 and P3.1. This entire section acts as output and

controller sends the signal through RS232 to PC and it will displayed on PC. We are using serial communication.

We use one relay to provide 230 volts for load. Relay is a electro mechanical switch.

Power supply is connected to 40th pin of the uc. 20th pin is grounded. Crystal oscillator is connected to 18th and 19th pin of uc. Resets switch is connected to 9th pin of uc.

MICROCONTROLLER (AT89S51)

Features:

• Compatible with MCS-51® Products

• 4K Bytes of In-System Programmable (ISP) Flash Memory

– Endurance: 1000 Write/Erase Cycles

• 4.0V to 5.5V Operating Range

• Fully Static Operation: 0 Hz to 33 MHz

• Three-level Program Memory Lock

• 128 x 8-bit Internal RAM

• 32 Programmable I/O Lines

• Two 16-bit Timer/Counters

• Six Interrupt Sources

• Full Duplex UART Serial Channel

• Low-power Idle and Power-down Modes

• Interrupt Recovery from Power-down Mode

• Watchdog Timer

• Dual Data Pointer

• Power-off Flag

• Fast Programming Time

• Flexible ISP Programming (Byte and Page Mode)

Description:

The AT89S51 is a low-power, high-performance CMOS 8-bit microcontroller with 4K bytes of in-system

programmable Flash memory. The device is manufactured using Atmel’s high-density nonvolatile

memory technology and is compatible with the industry- standard 80C51 instruction set and pinout. The

on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional

nonvolatile memory programmer. By combining a versatile 8-bit CPU with in-system programmable

Flash on a monolithic chip, the Atmel AT89S51 is a powerful microcontroller which provides a highly-

flexible and cost-effective solution to many embedded control applications.

The AT89S51 provides the following standard features:

4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, two 16-bit

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

and clock circuitry. In addition, the AT89S51 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 contents but freezes the oscillator, disabling all other chip functions

until the next external interrupt or hardware reset.

Pin Description:

VCC - Supply voltage.

GND - Ground.

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 during 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 internal 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. Port 1 also receives the low-order address bytes during

Flash programming and verification.

Port 2 Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers

cansink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the internal

pull-ups and can be used as inputs. As inputs, Port 2 pins that 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 during 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 Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers can

sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by the internal pull-

ups and can be used as inputs. As inputs, Port 3 pins that 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 AT89S51, as shown in the

following 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 (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 during 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 AT89S51

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 external 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

Special Function Registers

A map of the on-chip memory area called the Special Function Register (SFR) space is shown in Table 1.

Note that not all of the addresses are occupied, and unoccupied addresses may not be implemented on

the chip. Read accesses to these addresses will in general return random data, and write accesses will

have an indeterminate effect.

User software should not write 1s to these unlisted locations, since they may be used in future products

to invoke new features. In that case, the reset or inactive values of the new bits will always be 0.

Interrupt Registers: The individual interrupt enable bits are in the IE register. Two priorities can be set

for each of the five interrupt sources in the IP register.

Dual Data Pointer Registers: To facilitate accessing both internal and external data memory, two banks

of 16-bit Data Pointer Registers are provided: DP0 at SFR address locations 82H- 83H and DP1 at 84H-

85H. Bit DPS = 0 in SFR AUXR1 selects DP0 and DPS = 1 selects DP1. The user should always initialize the

DPS bit to the appropriate value before accessing the respective Data Pointer Register.

Power Off Flag: The Power Off Flag (POF) is located at bit 4 (PCON.4) in the PCON SFR. POF is set to “1”

during power up. It can be set and rest under software control and is not affected by reset.

Memory Organization

MCS-51 devices have a separate address space for Program and Data Memory. Up to 64K bytes each of

external Program and Data Memory can be addressed.

Program Memory If the EA pin is connected to GND, all program fetches are directed to external

memory. On the AT89S51, if EA is connected to VCC, program fetches to addresses 0000H through

FFFH are directed to internal memory and fetches to addresses 1000H through FFFFH are directed to

external memory.

Data Memory the AT89S51 implements 128 bytes of on-chip RAM. The 128 bytes are accessible via

direct and indirect addressing modes. Stack operations are examples of indirect addressing, so the 128

bytes of data RAM are available as stack space.

Watchdog Timer (One-time Enabled with Reset-out)

The WDT is intended as a recovery method in situations where the CPU may be subjected to software

upsets. The WDT consists of a 14-bit counter and the Watchdog Timer Reset (WDTRST) SFR. The WDT is

defaulted to disable from exiting reset. To enable the WDT, a user must write 01EH and 0E1H in

sequence to the WDTRST register (SFR location 0A6H). When the WDT is enabled, it will increment every

machine cycle while the oscillator is running. The WDT timeout period is dependent on the external

clock frequency. There is no way to disable the WDT except through reset (either hardware reset or

WDT overflow reset). When WDT overflows, it will drive an output RESET HIGH pulse at the RST pin.

Using the WDT To enable the WDT, a user must write 01EH and 0E1H in sequence to the DTRST register

(SFR location 0A6H). When the WDT is enabled, the user needs to service it by writing 01EH

and 0E1H to WDTRST to avoid a WDT overflow. The 14-bit counter overflows when it reaches 16383

(3FFFH), and this will reset the device. When the WDT is enabled, it will increment every machine cycle

while the oscillator is running. This means the user must reset the WDT at least every 16383 machine

cycles. To reset the WDT the user must write 01EH and 0E1H to WDTRST. WDTRST is a write-only

register. The WDT counter cannot be read or written. When WDT overflows, it will generate an output

RESET pulse at the RST pin. The RESET pulse duration is 98xTOSC, where TOSC=1/FOSC. To make the

best use of the WDT, it should be serviced in those sections of code that will periodically be executed

within the time required to prevent a WDT reset.

WDT During Power-down and Idle

In Power-down mode the oscillator stops, which means the WDT also stops. While in Powerdown

mode, the user does not need to service the WDT. There are two methods of exiting Power-down mode:

by a hardware reset or via a level-activated external interrupt, which is enabled prior to entering Power-

down mode. When Power-down is exited with hardware reset, servicing the WDT should occur as it

normally does whenever the AT89S51 is reset. Exiting Power-down with an interrupt is significantly

different. The interrupt is held low long enough for the oscillator to stabilize. When the interrupt is

brought high, the interrupt is serviced. To prevent the WDT from resetting the device while the interrupt

pin is held low, the WDT is not started until the interrupt is pulled high. It is suggested that the WDT be

reset during the interrupt service for the interrupt used to exit Power-down mode. To ensure that the

WDT does not overflow within a few states of exiting Power-down, it is best to reset the WDT just

before entering Power-down mode. Before going into the IDLE mode, the WDIDLE bit in SFR AUXR is

used to determine whether the WDT continues to count if enabled. The WDT keeps counting during IDLE

(WDIDLE bit =

0) as the default state. To prevent the WDT from resetting the AT89S51 while in IDLE mode, the user

should always set up a timer that will periodically exit IDLE, service the WDT, and reenter IDLE mode.

With WDIDLE bit enabled, the WDT will stop to count in IDLE mode and resumes the count upon exit

from IDLE.

UART The UART in the AT89S51 operates the same way as the UART in the AT89C51.

Timer 0 and 1 Timer 0 and Timer 1 in the AT89S51 operate the same way as Timer 0 and Timer 1 in the

AT89C51.

Interrupts The AT89S51 has a total of five interrupt vectors: two external interrupts (INT0 and INT1),

two timer interrupts (Timers 0 and 1), and the serial port interrupt. These interrupts are all shown in

Figure 1. Each of these interrupt sources can be individually enabled or disabled by setting or clearing a

bit in Special Function Register IE. IE also contains a global disable bit, EA, which disables all interrupts at

once. Note that Table 4 shows that bit position IE.6 is unimplemented. In the AT89S51, bit position IE.5

is also unimplemented. User software should not write 1s to these bit positions, since they may be used

in future AT89 products. The Timer 0 and Timer 1 flags, TF0 and TF1, are set at S5P2 of the cycle in which

the timers overflow. The values are then polled by the circuitry in the next cycle.

Oscillator Characteristics

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that can be configured

for use as an on-chip oscillator, as shown in Figure 2. Either a quartz crystal or ceramic resonator may be

used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1

is driven, as shown in Figure 3. There are no requirements on the duty cycle of the external clock signal,

since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and

maximum voltage high and low time specifications must be observed.

Idle Mode In idle mode, the CPU puts itself to sleep while all the on-chip peripherals remain active. The

mode is invoked by software. The content of the on-chip RAM and all the special function registers

remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a

hardware reset. Note that when idle mode is terminated by a hardware reset, the device normally

resumes program execution from where it left off, up to two machine cycles before the internal reset

algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to

the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when idle

mode is terminated by a reset, the instruction following the one that invokes idle mode should not write

to a port pin or to external memory.

Power-down Mode

In the Power-down mode, the oscillator is stopped, and the instruction that invokes Powerdown is the

last instruction executed. The on-chip RAM and Special Function Registers retain their values until the

Power-down mode is terminated. Exit from Power-down mode can be initiated either by a hardware

reset or by activation of an enabled external interrupt into INT0 or INT1. Reset redefines the SFRs but

does not change the on-chip RAM. The reset should not be activated before VCC is restored to its

normal operating level and must be held active long enough to allow the oscillator to restart and

stabilize.

Program Memory Lock Bits

The AT89S51 has three lock bits that can be left unprogrammed (U) or can be programmed (P) to obtain

the additional features listed in the following table.

When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the

device is powered up without a reset, the latch initializes to a random value and holds that value until

reset is activated. The latched value of EA must agree with the current logic level at that pin in order for

the device to function properly.

Programming the Flash – Parallel Mode

The AT89S51 is shipped with the on-chip Flash memory array ready to be programmed. The

programming interface needs a high-voltage (12-volt) program enable signal and is compatible with

conventional third-party Flash or EPROM programmers. The AT89S51 code memory array is

programmed byte-by-byte.

Programming Algorithm: Before programming the AT89S51, the address, data, and control signals

should be set up according to the Flash programming mode table and Figures 13 and 14. To program the

AT89S51, take the following steps:

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

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

3. Activate the correct combination of control signals.

4. Raise EA/VPP to 12V.

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

timed and typically takes no more than 50 μs. 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 AT89S51 features Data Polling to indicate the end of a byte write cycle. During a write

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

P0.7. Once the write cycle has been completed, true data is 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.

P3.0 is pulled low after ALE goes high during programming to indicate BUSY. P3.0 is pulled high again

when programming is done to indicate READY.

Program Verify: If lock bits LB1 and LB2 have not been programmed, the programmed code data can be

read back via the address and data lines for verification. The status of the individual lock bits can be

verified directly by reading them back.

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

verification of locations 000H, 100H, and 200H, except that P3.6 and P3.7 must be pulled to a logic low.

The values returned are as follows.

(000H) = 1EH indicates manufactured by Atmel

(100H) = 51H indicates 89S51

(200H) = 06H

Chip Erase: In the parallel programming mode, a chip erase operation is initiated by using the proper

combination of control signals and by pulsing ALE/PROG low for a duration of 200 ns - 500 ns. In the

serial programming mode, a chip erase operation is initiated by issuing the Chip Erase instruction. In this

mode, chip erase is self-timed and takes about 500 ms. During chip erase, a serial read from any address

location will return 00H at the data output.

Programming the Flash – Serial Mode

The Code memory array can be programmed using the serial ISP interface while RST is pulled to VCC.

The serial interface consists of pins SCK, MOSI (input) and MISO (output). After RST is set high, the

Programming Enable instruction needs to be executed first before other operations can be executed.

Before a reprogramming sequence can occur, a Chip Erase operation is required.

The Chip Erase operation turns the content of every memory location in the Code array into FFH. Either

an external system clock can be supplied at pin XTAL1 or a crystal needs to be connected across pins

XTAL1 and XTAL2. The maximum serial clock (SCK) frequency should be less than 1/16 of the crystal

frequency. With a 33 MHz oscillator clock, the maximum SCK frequency is 2 MHz.

Serial Programming Algorithm

To program and verify the AT89S51 in the serial programming mode, the following sequence is

recommended:

1. Power-up sequence:

Apply power between VCC and GND pins.

Set RST pin to “H”.

If a crystal is not connected across pins XTAL1 and XTAL2, apply a 3 MHz to 33 MHz clock to XTAL1 pin

and wait for at least 10 milliseconds.

2. Enable serial programming by sending the Programming Enable serial instruction to pin MOSI/P1.5.

The frequency of the shift clock supplied at pin SCK/P1.7 needs to be less than the CPU clock at XTAL1

Divided by 16.

3. The Code array is programmed one byte at a time in either the Byte or Page mode. The write cycle is

self-timed and typically takes less than 0.5 ms at 5V.

4. Any memory location can be verified by using the Read instruction that returns the content at the

selected address at serial output MISO/P1.6.

5. At the end of a programming session, RST can be set low to commence normal device operation.

Power-off sequence (if needed):

Set XTAL1 to “L” (if a crystal is not used).

Set RST to “L”.

Turn VCC power off.

Data Polling: The Data Polling feature is also available in the serial mode. In this mode, during a write

cycle an attempted read of the last byte written will result in the complement of the MSB of the serial

output byte on MISO.

Serial Programming Instruction Set

The Instruction Set for Serial Programming follows a 4-byte protocol and is shown in Table 8 on page 18.

Programming Interface – Parallel Mode

Every code byte in the Flash array can be programmed 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.

Please contact your local programming vendor for the appropriate software revision.

After Reset signal is high, SCK should be low for at least 64 system clocks before it goes high to clock in

the enable data bytes. No pulsing of Reset signal is necessary. SCK should be no faster than 1/16 of the

system clock at XTAL1.

For Page Read/Write, the data always starts from byte 0 to 255. After the command byte and upper

address byte are

latched, each byte thereafter is treated as data until all 256 bytes are shifted in/out. Then the next

instruction will be ready to be decoded.

*NOTICE: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent

damage to the device. This is a stress rating only and functional operation of the device at these or any

other conditions beyond those indicated in the operational sections of this specification is not implied.

Exposure to absolute maximum rating

conditions for extended periods may affect device reliability.

Serial Communication:

Computers can transfer data in two ways: parallel and serial. In parallel data transfers, often 8

or more lines (wire conductors) are used to transfer data to a device that is only a few feet away.

Examples of parallel data transfer are printers and hard disks; each uses cables with many wire strips.

Although in such cases a lot of data can be transferred in a short amount of time by using many wires in

parallel, the distance cannot be great. To transfer to a device located many meters away, the serial

method is used. In serial communication, the data is sent one bit at a time, in contrast to parallel

communication, in which the data is sent a byte or more at a time. Serial communication of the 8051 is

the topic of this chapter. The 8051 has serial communication capability built into it, there by making

possible fast data transfer using only a few wires.

If data is to be transferred on the telephone line, it must be converted from 0s and 1s to audio

tones, which are sinusoidal-shaped signals. A peripheral device called a modem, which stands for

“modulator/demodulator”, performs this conversion.

Serial data communication uses two methods, asynchronous and synchronous. The

synchronous method transfers a block of data at a time, while the asynchronous method transfers a

single byte at a time.

In data transmission if the data can be transmitted and received, it is a duplex transmission.

This is in contrast to simplex transmissions such as with printers, in which the computer only sends data.

Duplex transmissions can be half or full duplex, depending on whether or not the data transfer can be

simultaneous. If data is transmitted one way at a time, it is referred to as half duplex. If the data can go

both ways at the same time, it is full duplex. Of course, full duplex requires two wire conductors for the

data lines, one for transmission and one for reception, in order to transfer and receive data

simultaneously.

Asynchronous serial communication and data framing

The data coming in at the receiving end of the data line in a serial data transfer is all 0s and 1s;

it is difficult to make sense of the data unless the sender and receiver agree on a set of rules, a protocol,

on how the data is packed, how many bits constitute a character, and when the data begins and ends.

Start and stop bits

Asynchronous serial data communication is widely used for character-oriented transmissions,

while block-oriented data transfers use the synchronous method. In the asynchronous method, each

character is placed between start and stop bits. This is called framing. In the data framing for

asynchronous communications, the data, such as ASCII characters, are packed between a start bit and a

stop bit. The start bit is always one bit, but the stop bit can be one or two bits. The start bit is always a 0

(low) and the stop bit (s) is 1 (high).

Data transfer rate

The rate of data transfer in serial data communication is stated in bps (bits per second).

Another widely used terminology for bps is baud rate. However, the baud and bps rates are not

necessarily equal. This is due to the fact that baud rate is the modem terminology and is defined as the

number of signal changes per second. In modems a single change of signal, sometimes transfers several

bits of data. As far as the conductor wire is concerned, the baud rate and bps are the same, and for this

reason we use the bps and baud interchangeably.

The data transfer rate of given computer system depends on communication ports

incorporated into that system. For example, the early IBMPC/XT could transfer data at the rate of 100

to 9600 bps. In recent years, however, Pentium based PCS transfer data at rates as high as 56K bps. It

must be noted that in asynchronous serial data communication, the baud rate is generally limited to

100,000bps.

Computers can transfer data in two ways: parallel and serial. In parallel data transfers,

often 8 or more lines (wire conductors) are used to transfer data to a device that is only a few feet away.

Examples of parallel transfers are printers and hard disks; each uses cables with many wire strips.

Although in such cases a lot of data can be transferred in a short amount of time by using many wires in

parallel, the distance cannot be great. To transfer to a device located many meters away, the serial

method is used. In serial communication, the data is sent one bit at a time, in contrast to parallel

communication, in which the data is sent a byte or more at a time. The 8051 has serial communication

capability built into it, there by making possible fast data transfer using only a few wires. The PC uses RS

232 as a Serial Communication Standard.

RS232 Standards

To allow compatibility among data communication equipment made by various manufacturers,

an interfacing standard called RS232 was set by the Electronics Industries Association (EIA) in 1960. In

1963 it was modified and called RS232A. RS232B AND RS232C were issued in 1965 and 1969,

respectively. Today, RS232 is the most widely used serial I/O interfacing standard. This standard is used

in PCs and numerous types of equipment. However, since the standard was set long before the advert

of the TTL logic family, its input and output voltage levels are not TTL compatible. In RS232, a 1 is

represented by -3 to -25V, while a 0 bit is +3 to +25V, making -3 to +3 undefined. For this reason, to

connect any RS232 to a microcontroller system we must use voltage converters such as MAX232 to

convert the TTL logic levels to the RS232 voltage levels, and vice versa. MAX232 IC chips are commonly

referred to as line drivers.

RS232 pins

RS232 cable connector commonly referred to as the DB-25 connector. In labeling, DB-

25P refers to the plug connector (male) and DB-25S is for the socket connector (female). Since

not all the pins are used in PC cables, IBM introduced the DB-9 Version of the serial I/O

standard, which uses 9 pins only, as shown in table.

DB-9 pin connector

1 2 3 4 5

6 7 8 9

(Out of computer and exposed end of cable)

Pin Functions:

Pin Description

1 Data carrier detect (DCD)

2 Received data (RXD)

3 Transmitted data (TXD)

4 Data terminal ready(DTR)

5 Signal ground (GND)

6 Data set ready (DSR)

7 Request to send (RTS)

8 Clear to send (CTS)

9 Ring indicator (RI)

Note: DCD, DSR, RTS and CTS are active low pins.

The method used by RS-232 for communication allows for a simple connection of three lines

namely Tx, Rx, and Ground.

TXD: carries data from DTE to the DCE.

RXD: carries data from DCE to the DTE

SG: signal ground

8051 connection to RS232

The RS232 standard is not TTL compatible; therefore, it requires a Line Driver such as the

MAX232 chip to convert RS232 voltage levels to TTL levels, and vice versa.

The 8051 has two pins that are used specifically for transferring and receiving data serially.

These two pins are TXD and RXD and are a part of the port 3 (P3.0 and P3.1). Pin 11 of the 8051 is

designated as TXD and pin 10 as RXD. These pins are TTL compatible; therefore, they require a line

driver to make them RS232 compatible. One such line driver is the MAX232 chip.

MAX232 converts from RS232 voltage levels to TTL voltage levels, and vice versa. One advantage

of the MAX232 chip is that it uses a +5V power source which, is the same as the source voltage for the

8051. In the other words, with a single +5V power supply we can power both the 8051 and MAX232,

with no need for the power supplies. The MAX232 has two sets of line drivers for transferring and

receiving data. The line drivers used for TXD are called T1 and T2, while the line drivers for RXD are

designated as R1 and R2. In many applications only one of each is used.

MAX 232 Serial Line Drivers:

The pin-out diagram of MAX 232 is shown below.

MAX 232E Dual Driver/Receiver

MAX 232 Operating Circuit:

Pin 10, 11 form the dual inputs with TTL logic whereas 14, 7 form the outputs for RS 232 logic. And the

12, 9, 13, 8 form the vice versa inputs and outputs as shown in fig.

The inputs and outputs of the drivers and receivers are shown in fig above.

Power supply

The power supplies are designed to convert high voltage AC mains

electricity to a suitable low voltage supply for electronics circuits and other devices. A power

supply can by broken down into a series of blocks, each of which performs a particular function.

A d.c power supply which maintains the output voltage constant irrespective of a.c mains

fluctuations or load variations is known as “Regulated D.C Power Supply”

For example a 5V regulated power supply system as shown below:

Transformer:

A transformer is an electrical device which is used to convert electrical power from one

Electrical circuit to another without change in frequency.

Transformers convert AC electricity from one voltage to another with little loss of power.

Transformers work only with AC and this is one of the reasons why mains electricity is AC.

Step-up transformers increase in output voltage, step-down transformers decrease in output

voltage. Most power supplies use a step-down transformer to reduce the dangerously high mains

voltage to a safer low voltage. The input coil is called the primary and the output coil is called

the secondary. There is no electrical connection between the two coils; instead they are linked by

an alternating magnetic field created in the soft-iron core of the transformer. The two lines in the

middle of the circuit symbol represent the core. Transformers waste very little power so the

power out is (almost) equal to the power in. Note that as voltage is stepped down current is

stepped up. The ratio of the number of turns on each coil, called the turn’s ratio, determines the

ratio of the voltages. A step-down transformer has a large number of turns on its primary (input)

coil which is connected to the high voltage mains supply, and a small number of turns on its

secondary (output) coil to give a low output voltage.

An Electrical Transformer

Turns ratio = Vp/ VS = Np/NS

Power Out= Power In

VS X IS=VP X IP

Vp = primary (input) voltage

Np = number of turns on primary coil

Ip = primary (input) current

RECTIFIER:

A circuit which is used to convert a.c to dc is known as RECTIFIER. The process of conversion a.c

to d.c is called “rectification”

TYPES OF RECTIFIERS:

Half wave Rectifier

Full wave rectifier

1. Centre tap full wave rectifier.

2. Bridge type full bridge rectifier.

Comparison of rectifier circuits:

Parameter

Type of Rectifier

Half wave Full wave Bridge

Number of diodes

1

2

4

PIV of diodes

Vm

2Vm

Vm

D.C output voltage Vm/ 2Vm/ 2Vm/

Vdc,at

no-load

0.318Vm

0.636Vm 0.636Vm

Ripple factor

1.21

0.482

0.482

Ripple

frequency

f

2f

2f

Rectification

efficiency

0.406

0.812

0.812

Transformer

Utilization

Factor(TUF)

0.287 0.693 0.812

RMS voltage Vrms Vm/2 Vm/√2 Vm/√2

Full-wave Rectifier:

From the above comparison we came to know that full wave bridge rectifier as more advantages than

the other two rectifiers. So, in our project we are using full wave bridge rectifier circuit.

Bridge Rectifier: A bridge rectifier makes use of four diodes in a bridge arrangement to achieve

full-wave rectification. This is a widely used configuration, both with individual diodes wired as

shown and with single component bridges where the diode bridge is wired internally.

A bridge rectifier makes use of four diodes in a bridge arrangement as shown in fig(a) to achieve

full-wave rectification. This is a widely used configuration, both with individual diodes wired as shown

and with single component bridges where the diode bridge is wired internally.

Fig(A)

Operation:

During positive half cycle of secondary, the diodes D2 and D3 are in forward biased while D1 and D4 are

in reverse biased as shown in the fig(b). The current flow direction is shown in the fig (b) with dotted

arrows.

Fig(B)

During negative half cycle of secondary voltage, the diodes D1 and D4 are in forward biased while D2

and D3 are in reverse biased as shown in the fig(c). The current flow direction is shown in the fig (c) with

dotted arrows.

Fig(C)

Filter:

A Filter is a device which removes the a.c component of rectifier output but allows the d.c component to reach the load

Capacitor Filter:

We have seen that the ripple content in the rectified output of half wave rectifier is 121% or that of

full-wave or bridge rectifier or bridge rectifier is 48% such high percentages of ripples is not acceptable

for most of the applications. Ripples can be removed by one of the following methods of filtering.

(a) A capacitor, in parallel to the load, provides an easier by –pass for the ripples voltage though it due

to low impedance. At ripple frequency and leave the d.c.to appears the load.

(b) An inductor, in series with the load, prevents the passage of the ripple current (due to high

impedance at ripple frequency) while allowing the d.c (due to low resistance to d.c)

(c) Various combinations of capacitor and inductor, such as L-section filter section filter, multiple

section filter etc. which make use of both the properties mentioned in (a) and (b) above. Two cases of

capacitor filter, one applied on half wave rectifier and another with full wave rectifier.

Filtering is performed by a large value electrolytic capacitor connected across the DC

supply to act as a reservoir, supplying current to the output when the varying DC voltage from

the rectifier is falling. The capacitor charges quickly near the peak of the varying DC, and then

discharges as it supplies current to the output. Filtering significantly increases the average DC

voltage to almost the peak value (1.4 × RMS value).

To calculate the value of capacitor(C),

C = ¼*√3*f*r*Rl

Where,

f = supply frequency,

r = ripple factor,

Rl = load resistance

Note: In our circuit we are using 1000µF. Hence large value of capacitor is placed to

reduce ripples and to improve the DC component.

Regulator:

Voltage regulator ICs is available with fixed (typically 5, 12 and 15V) or variable output voltages. The

maximum current they can pass also rates them. Negative voltage regulators are available, mainly for

use in dual supplies. Most regulators include some automatic protection from excessive current

('overload protection') and overheating ('thermal protection'). Many of the fixed voltage regulator ICs

have 3 leads and look like power transistors, such as the 7805 +5V 1A regulator shown on the right. The

LM7805 is simple to use. You simply connect the positive lead of your unregulated DC power supply

(anything from 9VDC to 24VDC) to the Input pin, connect the negative lead to the Common pin and then

when you turn on the power, you get a 5 volt supply from the output pin.

Fig 6.1.6 A Three Terminal Voltage Regulator

78XX:

The Bay Linear LM78XX is integrated linear positive regulator with three terminals. The LM78XX

offer several fixed output voltages making them useful in wide range of applications. When used as a

zener diode/resistor combination replacement, the LM78XX usually results in an effective output

impedance improvement of two orders of magnitude, lower quiescent current. The LM78XX is available

in the TO-252, TO-220 & TO-263packages,

Features:

• Output Current of 1.5A

• Output Voltage Tolerance of 5%

• Internal thermal overload protection

• Internal Short-Circuit Limited

• No External Component

• Output Voltage 5.0V, 6V, 8V, 9V, 10V,12V, 15V, 18V, 24V

• Offer in plastic TO-252, TO-220 & TO-263

• Direct Replacement for LM78XX

ANALOG TO DIGITAL CONVERTER

8-Bit, Microprocessor-Compatible, A/D Converters

The ADC080X family is CMOS 8-Bit, successive approximation A/D converters which use a

modified potentiometer ladder and are designed to operate with the 8080A control bus via three-state

outputs. These converters appear to the processor as memory locations or I/O ports, and hence no

interfacing logic is required. The differential analog voltage input has good common mode-rejection and

permits offsetting the analog zero-input voltage value. In addition, the voltage reference input can be

adjusted to allow encoding any smaller analog voltage span to the full 8 bits of resolution.

Features

• 80C48 and 80C80/85 Bus Compatible - No Interfacing

Logic Required

• Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . <100us

• Easy Interface to Most Microprocessors

• Will Operate in a “Stand Alone” Mode

• Differential Analog Voltage Inputs

• Works with Band gap Voltage References

• TTL Compatible Inputs and Outputs

• On-Chip Clock Generator

• Analog Voltage Input Range

(Single + 5V Supply) . . . . . . . . . . . . . . . . . . . . . . 0V to 5V

• No Zero-Adjust Required

• 80C48 and 80C80/85 Bus Compatible - No Interfacing

Logic Required

As the peripheral signals usually are substantially different from the ones that micro-

controller can understand (zero and one), they have to be converted into a pattern which can be

comprehended by a micro-controller. This task is performed by a block for analog to digital

conversion or by an ADC. This block is responsible for converting an information about some

analog value to a binary number and for follow it through to a CPU block so that CPU block can

further process it.

fig- 4.1

This analog to digital converter (ADC) converts a continuous analog input signal, into an n-bit binary

number, which is easily acceptable to a computer.

As the input increases from zero to full scale, the output code stair steps. The width of an ideal

step represents the size of the least significant Bit (LSB) of the converter and corresponds to an input

voltage of VES/2n for an n-bit converter. Obviously for an input voltage range of one LSB, the output

code is constant. For a given output code, the input voltage can be any where within a one LSB

quantization interval.

An actual converter has integral linearity and differential linearity errors. Differential linearity error is

the difference between the actual code-step width and one LSB. Integral linearity error is a measure of

the deviation of the code transition points from the fitted line.

The errors of the converter are determined by the fitting of a line through the code transition

points, using least square fit, the terminal point method, or the zero base technique to provide the

reference line.

A good converter will have less than 0.5 LSB linearity error and no missing codes over its full

temperature range. In the basic conversion scheme of ADC, the un-known input voltage VX is connected

to one input of an analog signal comparator, and a time dependant reference voltage VR is connected to

the other input of the comparator.

In this project work ADC 080X (8 Bit A/D converter) is used to convert analog voltage variations

(according to the condition of the parameters) into digital pulses. This IC is having built in multi-plexer

so that channel selection can be done automatically.

FUNCTIONAL DESCRIPTION:

The ADC 0804 shown in figure can be functionally divided into 2 basic sub circuits.

These two sub circuits are an analog multiplexer and an A/D Converter. The multiplexer uses

8 standard CMOS analog switches to provide to up to 4 analog inputs. The switches are

selectively turned on, depending on the data latched in to 3-bit multiplexer address register.

The second functional block, the successive approximation A/D converter, transforms the

analog output of the multiplexer to an 8-bit digital word. The output of the multiplexer goes to

one of two comparator inputs. The other input is derived from a 256R resistor ladder, which is

tapped by a MOSFET transistor switch tree. The converter control logic controls the switch tree,

funneling a particular tap voltage to comparator. Based on the result of this comparison, the

control logic and the successive approximation register (SAR) will decide whether the next tap to

be selected should be higher or lower than the present tap on the resistor ladder. This algorithm is

executed 8 times per conversion, once every 8-clock period, yielding a total conversion time of

clock periods.

When the conversion cycle is complete the resulting data is loaded into the TRI-STATE output

latch. The data in the output latch can be then be read by the host system any time before the end of

the next conversion. The TRI-STATE capability of the latch allows easy interfaces to bus oriented

systems.

The operation on these converters by a microprocessor or some control logic is very

simple. The controlling device first selects the desired input channel. To do this, a 3-bit channel

address is placed on the A, B, C in and out pins; and the ALE input is pulsed positively, clocking

the address into the multiplexer address register. To begin the conversion, the START pin is

pulsed. On the rising edge of this pulse the internal registers are cleared and on the falling edge

the start conversion is initiated.

As mentioned earlier, there are 8 clock periods per approximation. Even though there is no

conversion in progress the ADC0804 is still internally cycling through these 8 clock periods. A start pulse

can occur any time during this cycle but the conversion will not actually begin until the converter

internally cycles to the beginning of the next 8 clock period sequence. As long as the start pin is held

high no conversion begins, but when the start pin is taken low the conversion will start within 8 clock

periods. The EOC output is triggered on the rising edge of the start pulse. It, too, is controlled by the 8

clock period cycle, so it will go low within 8 clock periods of the rising edge of the start pulse. One can

see that it is entirely possible for EOC to go low before the conversion starts internally, but this is not

important, since the positive transition of EOC, which occurs at the end of a conversion, is what the

control logic is looking for.

Once EOC does go high this signals the interface logic that the data resulting from the

conversion is ready to be read. The output enable(OE) is then raised high. This enables the TRI-

STATE outputs, allowing the data to be read. Figure shows the timing diagram.

MUX

Address

4 x 1

Analog

MUX

CONTROL LOGIC

SAR

TRI- STATE

Output

RELAYS

Relay is an electrically operated switch. Current flowing through the coil of the relay creates a magnetic

field which attracts a lever and changes the switch contacts. The coil current can be on or off so relays

have two switch positions and they are double throw (changeover) switches.

Relays allow one circuit to switch a second circuit which can be completely separate from the

first. For example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit. There is

no electrical connection inside the relay between the two circuits; the link is magnetic and mechanical.

The coil of a relay passes a relatively large current, typically 30mA for a 12V relay, but it can be

as much as 100mA for relays designed to operate from lower voltages. Most ICs (chips) cannot provide

this current and a transistor is usually used to amplify the small IC current to the larger value required

for the relay coil. The maximum output current for the popular 555 timer IC is 200mA so these devices

can supply relay coils directly without amplification.

Relays are usually SPDT or DPDT but they can have many more sets of switch contacts, for

example relays with 4 sets of changeover contacts are readily available. For further information about

switch contacts and the terms used to describe them please see the page on switches.

Most relays are designed for PCB mounting but you can solder wires directly to the pins

providing you take care to avoid melting the plastic case of the relay. The supplier's catalogue should

show you the relay's connections. The coil will be obvious and it may be connected either way round.

Relay coils produce brief high voltage 'spikes' when they are switched off and this can destroy transistors

and ICs in the circuit. To prevent damage you must connect a protection diode across the relay coil.

The animated picture shows a working relay with its coil and switch contacts. You can see a

lever on the left being attracted by magnetism when the coil is switched on. This lever moves the switch

contacts. There is one set of contacts (SPDT) in the foreground and another behind them, making the

relay DPDT.

The relay's switch connections are usually labeled as COM, NC and NO:

COM = Common, always connect to this, it is the moving part of the switch.

NC = Normally Closed, COM is connected to this when the relay coil is off.

NO = Normally Open, COM is connected to this when the relay coil is on.

Connect to COM and NO if you want the switched circuit to be on when the relay coil is on.

Connect to COM and NC if you want the switched circuit to be on when the relay coil is off.

Choosing a relay

You need to consider several features when choosing a relay:

1. Physical size and pin arrangement If you are choosing a relay for an existing PCB you will need to

ensure that its dimensions and pin arrangement are suitable. You should find this information in

the supplier's catalogue.

2. Coil voltage the relay's coil voltage rating and resistance must suit the circuit powering the relay

coil. Many relays have a coil rated for a 12V supply but 5V and 24V relays are also readily

available. Some relays operate perfectly well with a supply voltage which is a little lower than

their rated value.

3. Coil resistance the circuit must be able to supply the current required by the relay coil. You can

use Ohm's law to calculate the current:

Relay coil current = supply voltage

coil resistance

4. For example: A 12V supply relay with a coil resistance of 400 passes a current of 30mA. This is

OK for a 555 timer IC (maximum output current 200mA), but it is too much for most ICs and they

will require a transistor to amplify the current.

5. Switch ratings (voltage and current) the relay's switch contacts must be suitable for the circuit

they are to control. You will need to check the voltage and current ratings. Note that the voltage

rating is usually higher for AC, for example: "5A at 24V DC or 125V AC".

6. Switch contact arrangement (SPDT, DPDT etc).

Most relays are SPDT or DPDT which are often described as "single pole changeover" (SPCO) or

"double pole changeover" (DPCO). For further information please see the page on switches

Protection diodes for relays

Transistors and ICs (chips) must be protected from the brief high voltage 'spike' produced when the

relay coil is switched off. The diagram shows how a signal diode (eg 1N4148) is connected across the

relay coil to provide this protection. Note that the diode is connected 'backwards' so that it will normally

not conduct. Conduction only occurs when the relay coil is switched off, at this moment current tries to

continue flowing through the coil and it is harmlessly diverted through the diode. Without the diode no

current could flow and the coil would produce a damaging high voltage 'spike' in its attempt to keep the

current flowing.

Relays and transistors compared

Like relays, transistors can be used as an electrically operated switch. For switching small DC

currents (< 1A) at low voltage they are usually a better choice than a relay. However transistors cannot

switch AC or high voltages (such as mains electricity) and they are not usually a good choice for

switching large currents (> 5A). In these cases a relay will be needed, but note that a low power

transistor may still be needed to switch the current for the relay's coil! The main advantages and

disadvantages of relays are listed below:

Advantages of relays:

Relays can switch AC and DC, transistors can only switch DC.

Relays can switch high voltages, transistors cannot.

Relays are a better choice for switching large currents (> 5A).

Relays can switch many contacts at once.

Disadvantages of relays:

Relays are bulkier than transistors for switching small currents.

Relays cannot switch rapidly (except reed relays), transistors can switch many times per second.

Relays use more power due to the current flowing through their coil.

Relays require more current than many chips can provide, so a low power transistor may be

needed to switch the current for the relay's coil.

Details:

These SPDT relays covers switching capacity of 10A in spite of miniature size for PCB Mount.

Contact Rating

12A at 120VAC

10A at 120VAC

10A at 24VDC

Coil Resistance400ohm 12VDC

Life expectancy Mechanical 10,000,000 operations at no load

Electrical 100,000 at rated resistive load

Applications:

Domestic Appliances

Office Machines

Audio Equipment

Coffee-Pots

Control units

CIRCUIT DESCRIPTION:

In this project we designed a system in such a way that it will monitor the load of the transformer

continuously and that information is transferred to the control room. In the main station these

parameters are displayed on the PC monitor. In the display unit we can view the continuous

information of transformer i.e. due to what reason the transformer has been failed, when the power is

resumed etc.,. With the help of this kind of system, the maintenance staff of the department can have

a continuous vigilance over the transformer.

In this project work, for the demonstration purpose a small step-down transformer of 12V, 1 amps

rating at secondary is considered and small bulbs are connected as a load. In this project we are

using CT transformer for measuring load current. All these parameters are converted into digital

value by using ADC. If the parameters of the transformer (Current) regain the limited range values

then Transformer will automatically shutdown. Microcontroller near the transformer section will

continuously transmit all the parameters of the transformer to PC of control room.

Software Components:

ABOUT SOFTWARE

Software’s used are:

*Keil software for c programming

*Express PCB for lay out design

*Express SCH for schematic design

What's New in µVision3?

µVision3 adds many new features to the Editor like Text Templates, Quick Function Navigation, and

Syntax Coloring with brace high lighting Configuration Wizard for dialog based startup and debugger

setup. µVision3 is fully compatible to µVision2 and can be used in parallel with µVision2.

What is µVision3?

µVision3 is an IDE (Integrated Development Environment) that helps you write, compile, and debug

embedded programs. It encapsulates the following components:

A project manager.

A make facility.

Tool configuration.

Editor.

A powerful debugger.

To help you get started, several example programs (located in the \C51\Examples, \C251\Examples, \

C166\Examples, and \ARM\...\Examples) are provided.

HELLO is a simple program that prints the string "Hello World" using the Serial Interface.

MEASURE is a data acquisition system for analog and digital systems.

TRAFFIC is a traffic light controller with the RTX Tiny operating system.

SIEVE is the SIEVE Benchmark.

DHRY is the Dhrystone Benchmark.

WHETS is the Single-Precision Whetstone Benchmark.

Additional example programs not listed here are provided for each device architecture.

Building an Application in µVision2

To build (compile, assemble, and link) an application in µVision2, you must:

1. Select Project -(forexample,166\EXAMPLES\HELLO\HELLO.UV2).

2. Select Project - Rebuild all target files or Build target.

µVision2 compiles, assembles, and links the files in your project.

Creating Your Own Application in µVision2

To create a new project in µVision2, you must:

1. Select Project - New Project.

2. Select a directory and enter the name of the project file.

3. Select Project - Select Device and select an 8051, 251, or C16x/ST10 device from the Device

Database™.

4. Create source files to add to the project.

5. Select Project - Targets, Groups, Files. Add/Files, select Source Group1, and add the source files

to the project.

6. Select Project - Options and set the tool options. Note when you select the target device from

the Device Database™ all special options are set automatically. You typically only need to

configure the memory map of your target hardware. Default memory model settings are optimal

for most applications.

7. Select Project - Rebuild all target files or Build target.

Debugging an Application in µVision2

To debug an application created using µVision2, you must:

1. Select Debug - Start/Stop Debug Session.

2. Use the Step toolbar buttons to single-step through your program. You may enter G, main in the

Output Window to execute to the main C function.

3. Open the Serial Window using the Serial #1 button on the toolbar.

Debug your program using standard options like Step, Go, Break, and so on.

Starting µVision2 and Creating a Project

µVision2 is a standard Windows application and started by clicking on the program icon. To create a new

project file select from the µVision2 menu.

Project – New Project…. This opens a standard Windows dialog that asks you

for the new project file name.

We suggest that you use a separate folder for each project. You can simply use the icon Create New

Folder in this dialog to get a new empty folder. Then select this folder and enter the file name for the

new project, i.e. Project1. µVision2 creates a new project file with the name PROJECT1.UV2 which

contains a default target and file group name. You can see these names in the Project.

Window – Files.

Now use from the menu Project – Select Device for Target and select a CPU for your project. The Select

Device dialog box shows the µVision2 device database. Just select the micro controller you use. We are

using for our examples the Philips 80C51RD+ CPU. This selection sets necessary tool options for the

80C51RD+ device and simplifies in this way the tool Configuration.

Building Projects and Creating a HEX Files

Typical, the tool settings under Options – Target are all you need to start a new application. You may

translate all source files and line the application with a click on the Build Target toolbar icon. When you

build an application with syntax errors, µVision2 will display errors and warning messages in the Output

Window – Build page. A double click on a message line opens the source file on the correct location in a

µVision2 editor window. Once you have successfully generated your application you can start

debugging.

After you have tested your application, it is required to create an Intel HEX file to download the

software into an EPROM programmer or simulator. µVision2 creates HEX files with each build process

when Create HEX files under Options for Target – Output is enabled. You may start your PROM

programming utility after the make process when you specify the program under the option Run User

Program #1.

CPU Simulation

µVision2 simulates up to 16 Mbytes of memory from which areas can be mapped for read, write, or

code execution access. The µVision2 simulator traps and reports illegal memory accesses.

In addition to memory mapping, the simulator also provides support for the integrated peripherals of

the various 8051 derivatives. The on-chip peripherals of the CPU you have selected are configured from

the Device.

Database selection

you have made when you create your project target. Refer to page 58 for more Information about

selecting a device. You may select and display the on-chip peripheral components using the Debug

menu. You can also change the aspects of each peripheral using the controls in the dialog boxes.

Start Debugging

You start the debug mode of µVision2 with the Debug – Start/Stop Debug Session command. Depending

on the Options for Target – Debug Configuration, µVision2 will load the application program and run the

startup code µVision2 saves the editor screen layout and restores the screen layout of the last debug

session. If the program execution stops, µVision2 opens an editor window with the source text or shows

CPU instructions in the disassembly window. The next executable statement is marked with a yellow

arrow. During debugging, most editor features are still available.

For example, you can use the find command or correct program errors. Program source text of your

application is shown in the same windows. The µVision2 debug mode differs from the edit mode in the

following aspects:

_ The “Debug Menu and Debug Commands” described on page 28 are Available. The additional debug

windows are discussed in the following.

_ The project structure or tool parameters cannot be modified. All build Commands are disabled.

Disassembly Window

The Disassembly window shows your target program as mixed source and assembly program or just

assembly code. A trace history of previously executed instructions may be displayed with Debug – View

Trace Records. To enable the trace history, set Debug – Enable/Disable Trace Recording.

If you select the Disassembly Window as the active window all program step commands work on CPU

instruction level rather than program source lines. You can select a text line and set or modify code

breakpoints using toolbar buttons or the context menu commands.

You may use the dialog Debug – Inline Assembly… to modify the CPU instructions. That allows

you to correct mistakes or to make temporary changes to the target program you are debugging.

Steps for executing the Keil programs:

1. Click on the Keil uVision Icon on Desktop

2. The following fig will appear

3. Click on the Project menu from the title bar

4. Then Click on New Project

5. Save the Project by typing suitable project name with no extension in u r own folder sited in either C:\ or D:\

6. Then Click on Save button above.

7. Select the component for u r project. i.e. Atmel……

8. Click on the + Symbol beside of Atmel

9. Select AT89C51 as shown below

10. Then Click on “OK”

11. The Following fig will appear

12. Then Click either YES or NO………mostly “NO”

13. Now your project is ready to USE

14. Now double click on the Target1, you would get another option “Source group 1” as shown

in next page.

15. Click on the file option from menu bar and select “new”

16. The next screen will be as shown in next page, and just maximize it by double clicking on its

blue boarder.

17. Now start writing program in either in “C” or “ASM”

18. For a program written in Assembly, then save it with extension “. asm” and for “C” based

program save it with extension “ .C”

19. Now right click on Source group 1 and click on “Add files to Group Source”

20. Now you will get another window, on which by default “C” files will appear.

21. Now select as per your file extension given while saving the file

22. Click only one time on option “ADD”

23. Now Press function key F7 to compile. Any error will appear if so happen.

24. If the file contains no error, then press Control+F5 simultaneously.

25. The new window is as follows

26. Then Click “OK”

27. Now Click on the Peripherals from menu bar, and check your required port as shown

in fig below

28. Drag the port a side and click in the program file.

29. Now keep Pressing function key “F11” slowly and observe.

30. You are running your program successfully

Conclusion

The project “PC BASED TRANSFORMER MONITOR AND PROTECTION” has been successfully designed and tested.

Integrating features of all the hardware components used have developed it. Presence of

every module has been reasoned out and placed carefully thus contributing to the best working of

the unit.

Secondly, using highly advanced IC’s and with the help of growing technology the

project has been successfully implemented.

Future Enhancement

In this project, we can use the RF technology for transmitting the signals from transformer to the

PC at the substation. The RF module covers the minimum range. Whereas in the place of RF

module if we use the latest technology called “Zig-bee” that covers the maximum range than RF.

If there is any extension of the bus station the Zig-bee will able to transmit the address to the

receiver station.

BIBLIOGRAPHY

The 8051 Micro controller and Embedded Systems

-Muhammad Ali Mazidi

Janice Gillispie Mazidi

The 8051 Micro controller Architecture, Programming & Applications

-Kenneth J. Ayala

Fundamentals Of Micro processors and Micro computers

-B. Ram

Micro processor Architecture, Programming & Applications

- Ramesh S. Gaonkar

Electronic Components

-D.V. Prasad

References on the Web:

www.national.com

www.atmel.com

www.microsoftsearch.com

www.geocities.com