pc interfacednmissile firing system

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PC INTERFACED MISSILE FIRING SYSTEM

WITH SONAR

CONTENT1. ABSTRACT

2.INTRODUCTION.

3.DESIGN PRINCIPLE.

4.CIRCUIT DESCRIPTION.

A. Power Supply.

B. Mother Board.

C. IR Transmitter.

D. IR Receiver.

E. Bidirectional motor driver.

F. PMDC MOTOR

G. Relay Driver

H. Signal Conditioning Circuit

I. SERIAL INTERFACING UNIT

J. BUZZER DRIVER

4.FUTURE EXPANSION.5.CONCLUSION.



1. ABSTRACT:

The PC based missile firing System with SONAR primarily functions to identify the

source of signal. The signal may be of any type and any kind, it automatically identifies

the presence of a particular signal and the antenna will remain stationary as long as the

signal link is established. Whenever the signal link break between the antenna and the

source the antenna revolves continuously in search of the signal. This system also has

advance connectivity with the computer to indicate the antenna position on the computer

terminal.

In this project the source of signal is simulated by a Infrared (IR) source. And a

corresponding IR receiver is used for detecting the signal. The receiver part includes one

mono-stable that improves the stability of the system, against the transient interruption

and momentary absence of the signal. The controller circuit is developed on a MCS –51-

core micro controller. The controller is designed on the base of embedded technology.

This controller mainly search the availability of the signal, when ever the signal found

absence at the receiver, the controller drives the dc motor to rotate and goes on till the

receiver found the signal. The controller provides necessary signal to the dc motor driver

on which the antenna is mounted. The driver circuit provides adequate current and

necessary voltage level to drive the motor in turn to move the antenna. Also the controller

communicates with the PC through its Serial Port, for indicating the position of the

antenna.



The entire system is constructed modularly; there are different sections in this

system which are as follows.

1. Power Supply.

2. Receiver.

3. Transmitter

4. Controller.

5. DC Motor.

6. Motor Driver.

7. Computer Interfacing

8. Software

All the above-mentioned sub systems contribute for the better functionality of the entire

system.

1. POWER SUPPLY: The Power supply section provides +5V DC and +12 V

DC, with a capacity of 1Amp current. This consists of mainly a bridge

rectifier and two series regulators 7812 and 7805. This power supply can

provide maximum 1 Amp current at + 5volt or +12 volt. How ever the

maximum current is limited to 1 amp by each component. Where as our

requirement is 750 mA at +5V and +12V.

2. RECEIVER: The receiver consists of two parts such as, sensor and

indicator. The IR sensor used here is a semiconductor device which respond



to IR signal. The sensor is IR detector diode, which is connected; in reverse

biased condition so the normal current during the absence of the IR signal is

very small. When the IR signal fall on the detector diode then the current in

the IR diode increases. The diode is connected in series with a resistor in a

voltage divider configuration. This change of voltage drop due to difference

of current flow in the resistance is detected by a comparator and the out put is

feed to a signal conditioning circuit to convert the out put in to a TTL

compatible signal and feed to the microcontroller for further processing..

3. TRANSMITTER: The transmitter is a simple LED driver which is drives a

IR LED This signal is given to a driver section which drives an IR LED to

generate IR signal in a continuous or discontinuous mode.

4. CONTROLLER: This is an embedded controller which is configured around

89C51 micro controller. The controller is designed with internal memory and

components of the micro controller. The controller unit receives signal from

the receiver and commands the driver to run the stepper motor and also

communicate with the PC to indicate the position of the antenna.

5. STEPPER MOTOR: The stepper motor is an electro mechanical device

which converts electrical energy into mechanical energy. The specialty of

this motor over d.c. motors that, it is a digital motor so moves in steps, so a

accurate position control is possible. The stepper motor rotates on rotation of

the bit pattern appearing to its coil. The speed of the motor depends on the

fastness at which the bit pattern rotates, but the magnitude of the bit voltage



decides the driving torque. The stepper motor holds the rotating antenna,

which rotates as per the instruction of the controller.

6. STEPPER MOTOR DRIVER: The stepper motor driver provides adequate

voltage and current to run the stepper. The driver receives control signal

from the controller at CMOS logic level, that is at 5 volt and 10 mA.

7. COMPUTER INTERFACE: The computer COM port is used here for

interfacing . This is a RS232 standard port which accepts serial data from the

microcontroller. The communication protocol is in the simplex mode. The PC

is running with a C++ program to monitor the position of the antenna. This is

the concept has been used to interface the controller with PC.

8. SOFTWARE: There are two types of software in this system. The controller

designed with MCS-51 Core based micro controller, assembly language

programs. Where as the controller interfacing program with PC has been

developed on C ++language.

SCOPE:

This Automatic Tracking System can be implemented in different ways for

different application with slight modification in hard ware and software.

1. The receiver in the antenna can be changed and by that this antenna can track

to different signals.



2. This system can further modified and developed for application into radar and

chasing a source for its continuous monitoring.

1. INTRODUCTION:

The development of electronically steerable, automatically self-directing,

antennas is described here is a small and tiny antenna which is mounted on the missile to

guide the missile to the target. This type of antenna is used for guiding the target when

the it changes its direction. When a missile or shut is fired to a target object the missile

approaches the target, in the mean while if the target changes its direction then the missile

should follow the target instead of misfiring. This type of antenna can be used at the

boarder areas to detect and enemy planes and track its movement. This antenna can chase

the target and acquire information regarding the target. This type of antenna is very

useful for application in defense purpose.

The target guided Antenna is designed with a microcontroller based system to control a

parabolic antenna to observe the movement of the target. This project is designed with

the concept of close loop control system and artificial memory. In the real application

when a target needs to be chased and tracked this type of antenna may be used. Missile

firing system and RADAR system may use this type of antenna for its application



The transmitter and receiver are designed for a particular type of modulated signal having

a particular characteristic. In this prototype the receiver is designed to receive IR signal.

A IR transmitter is used for transmitting 38KHz modulated signal as a source of signal

and an IR receiver is used for receiving the same modulated signal. So the prototype

antenna developed here acts as a Infra-Red signal guided Antenna.

2. DESIGN PRINCIPLE

This project is designed on the principle of feedback control system. The control

system designed here to control the movement of a DC motor. The receivers /

sensors are used in this project is sensitive to Infra- red signal. The parabolic

antenna designed here consisting of three sensors arranged as shown in the

figure below.

The center, left and right sensors are connected to the micro controller and process the

signal after receiving those. The receivers receive infrared signal and feed to the micro



controller after conditioning. In this project on starting condition the antenna remains

stationary and wait until the target comes into the proximity of any of the sensor, once the

sensor detects the target the target moves until the target is aligned with center. After the

target get aligned with center the antenna moves in the same direction as the target moves

and the antenna movement continue until the antenna center again aligned with the

targeted.

The basic principle for designing this project is based on the IR transmitter and

receiver. The out put of the sensor is send to the microcontroller and PC. And PC

plotted a circular graphics on the Screen to measure the distance of the target. In

the C++ programmed threshold limit is fixed for the target. If the target move

beyond the minimum proximity level then the microcontroller sends a signal to

the missile to destroy the target. In this project the firing system is simulated by a

laser light.

3. CIRCUIT DESCRIPTION

A. POWER SUPPLY :-( +ve)

Circuit connection: - In this we are using Transformer (0-12) VAC/1Amp, IC 7805 &

7812, diodes IN 4007, LED & resistors.

Here 230V, 50 Hz ac signal is given as input to the primary of the transformer

and the secondary of the transformer is given to the bridge rectification diode.

The o/p of the diode is given as i/p to the IC regulator (7805 &7812) through



capacitor (1000uf/35v). The o/p of the IC regulator is given to the LED through

resistors.

Circuit Explanations: - When ac signal is given to the primary of the

transformer, due to the magnetic effect of the coil magnetic flux is induced in the

coil (primary) and transfer to the secondary coil of the transformer due to the

transformer action.” Transformer is an electromechanical static device which

transformer electrical energy from one coil to another without changing its

frequency”. Here the diodes are connected in a bridge fashion. The secondary

coil of the transformer is given to the bridge circuit for rectification purposes.

During the +ve cycle of the ac signal the diodes D2 & D4 conduct due to the

forward bias of the diodes and diodes D1 & D3 does not conduct due to the

reversed bias of the diodes. Similarly during the –ve cycle of the ac signal the

diodes D1 & D3 conduct due to the forward bias of the diodes and the diodes D2

& D4 does not conduct due to reversed bias of the diodes. The output of the

bridge rectifier is not a power dc along with rippled ac is also present. To

overcome this effect, a capacitor is connected to the o/p of the diodes (D2 & D3).

Which removes the unwanted ac signal and thus a pure dc is obtained. Here we

need a fixed voltage, that’s for we are using IC regulators (7805 & 7812).”Voltage

regulation is a circuit that supplies a constant voltage regardless of changes in

load current.” This IC’s are designed as fixed voltage regulators and with

adequate heat sinking can deliver output current in excess of 1A. The o/p of the

bridge rectifier is given as input to the IC regulator through capacitor with respect



to GND and thus a fixed o/p is obtained. The o/p of the IC regulator (7805 &

7812) is given to the LED for indication purpose through resistor. Due to the

forward bias of the LED, the LED glows ON state, and the o/p are obtained from

the pin no-3.



T 11 5

4 8

7 8 1 2

1 K

I N 4 0 0 7 * 4

V o u

L E D

P O W E R S U P P L Y ( + V E )

7 8 0 5

L E D

V o u

9 - 0 - 9 V2 . 2 K

- +

1

2

3

4

2 3 0 V 5 0 H Z

1 0 0 0 M F / 3 5 V



B. MOTHER BOARD:

The motherboard of this project is designed with a MSC –51 core compatible

micro controller. The motherboard is designed on a printed circuit board,

compatible for the micro controller. This board is consisting of a socket for micro

controller, input /output pull-up registers; oscillator section and auto reset circuit.

Microcontroller core processor:

Introduction

Despite it’s relatively old age, the 89C51 is one of the most popular Micro controller in

use today. Many derivatives Micro controllers have since been developed that are based

on--and compatible with--the 8051. Thus, the ability to program an 89C51 is an

important skill for anyone who plans to develop products that will take advantage of

Micro controller.

Many web pages, books, and tools are available for the 89C51 developer.

The 89C51 has three very general types of memory. To effectively program the

8051 it is necessary to have a basic understanding of these memory types.

The memory types are illustrated in the following graphic. They are: On-Chip

Memory, External Code Memory, and External RAM.



On-Chip Memory refers to any memory (Code, RAM, or other) that physically

exists on the Microcontroller itself. On-chip memory can be of several types, but

we'll get into that shortly.

External Code Memory is code (or program) memory that resides off-chip. This

is often in the form of an external EPROM.

External RAM is RAM memory that resides off-chip. This is often in the form of

standard static RAM or flash RAM.

Code Memory

Code memory is the memory that holds the actual 8051 program that is to be

run. This memory is limited to 64K and comes in many shapes and sizes: Code

memory may be found on-chip, either burned into the Microcontroller as ROM or

EPROM. Code may also be stored completely off-chip in an external ROM or,

more commonly, an external EPROM. Flash RAM is also another popular

method of storing a program. Various combinations of these memory types may



also be used--that is to say, it is possible to have 4K of code memory on-chip and

64k of code memory off-chip in an EPROM.

When the program is stored on-chip the 64K maximum is often reduced to 4k, 8k,

or 16k. This varies depending on the version of the chip that is being used. Each

version offers specific capabilities and one of the distinguishing factors from chip

to chip is how much ROM/EPROM space the chip has.

However, code memory is most commonly implemented as off-chip EPROM.

This is especially true in low-cost development systems and in systems

developed by students.

Programming Tip: Since code memory is restricted to 64K, 89C51 programs

are limited to 64K. Some assemblers and compilers offer ways to get around this

limit when used with specially wired hardware. However, without such special

compilers and hardware, programs are limited to 64K.

External RAM

As an obvious opposite of Internal RAM , the 89C51 also supports what is called

External RAM .

As the name suggests, External RAM is any random access memory which is

found off-chip. Since the memory is off-chip it is not as flexible in terms of



accessing, and is also slower. For example, to increment an Internal RAM

location by 1 requires only 1 instruction and 1 instruction cycle. To increment a 1-

byte value stored in External RAM requires 4 instructions and 7 instruction

cycles. In this case, external memory is 7 times slower!

What External RAM loses in speed and flexibility it gains in quantity. While

Internal RAM is limited to 128 bytes (256 bytes with an 8052), the 8051 supports

External RAM up to 64K.

Programming Tip: The 8051 may only address 64k of RAM. To expand RAM

beyond this limit requires programming and hardware tricks. You may have to do

this "by hand" since many compilers and assemblers, while providing support for

programs in excess of 64k, do not support more than 64k of RAM. This is rather

strange since it has been my experience that programs can usually fit in 64k but

often RAM is what is lacking. Thus if you need more than 64k of RAM, check to

see if your compiler supports it-- but if it doesn't, be prepared to do it by hand.

On-Chip Memory

As mentioned at the beginning of this chapter, the 89C51 includes a certain

amount of on-chip memory. On-chip memory is really one of two types: Internal

RAM and Special Function Register (SFR) memory. The layout of the 89C51's

internal memory is presented in the following memory map:



As is illustrated in this map, the 8051 has a bank of 128 bytes of Internal RAM .

This Internal RAM is found on-chip on the 8051 so it is the fastest RAM available,

and it is also the most flexible in terms of reading, writing, and modifying it’s

contents. Internal RAM is volatile, so when the 8051 is reset this memory is

cleared.

The 128 bytes of internal ram is subdivided as shown on the memory map. The

first 8 bytes (00h - 07h) are "register bank 0". By manipulating certain SFRs, a

program may choose to use register banks 1, 2, or 3. These alternative register

banks are located in internal RAM in addresses 08h through 1Fh. We'll discuss

"register banks" more in a later chapter. For now it is sufficient to know that they

"live" and are part of internal RAM.



Bit Memory also lives and is part of internal RAM. We'll talk more about bit

memory very shortly, but for now just keep in mind that bit memory actually

resides in internal RAM, from addresses 20h through 2Fh.

The 80 bytes remaining of Internal RAM, from addresses 30h through 7Fh, may

be used by user variables that need to be accessed frequently or at high-speed.

This area is also utilized by the Microcontroller as a storage area for the

operating stack . This fact severely limits the 8051’s stack since, as illustrated in

the memory map, the area reserved for the stack is only 80 bytes--and usually it

is less since this 80 bytes has to be shared between the stack and user

variables.

SFR Descriptions

There are different special function registers (SFR) designed in side the 89C51

micro controller. In this micro controller all the input , output ports, timers

interrupts are controlled by the SFRs. The SFR functionalities are as follows.

This section will endeavor to quickly overview each of the standard SFRs found

in the above SFR chart map. It is not the intention of this section to fully explain

the functionality of each SFR--this information will be covered in separate



chapters of the tutorial. This section is to just give you a general idea of what

each SFR does.

P0 (Port 0, Address 80h, Bit-Addressable): This is input/output port 0. Each bit

of this SFR corresponds to one of the pins on the Microcontroller. For example,

bit 0 of port 0 is pin P0.0, bit 7 is pin P0.7. Writing a value of 1 to a bit of this SFR

will send a high level on the corresponding I/O pin whereas a value of 0 will bring

it to a low level.

Programming Tip: While the 8051 has four I/O port (P0, P1, P2, and P3), if your

hardware uses external RAM or external code memory (i.e., your program is stored in an

external ROM or EPROM chip or if you are using external RAM chips) you may not use

P0 or P2. This is because the 8051 uses ports P0 and P2 to address the external memory.

Thus if you are using external RAM or code memory you may only use ports P1 and P3

for your own use.

SP (Stack Pointer, Address 81h): This is the stack pointer of the Microcontroller. This

SFR indicates where the next value to be taken from the stack will be read from in

Internal RAM. If you push a value onto the stack, the value will be written to the address

of SP + 1. That is to say, if SP holds the value 07h, a PUSH instruction will push the

value onto the stack at address 08h. This SFR is modified by all instructions which

modify the stack, such as PUSH, POP, LCALL, RET, RETI, and whenever interrupts are

provoked by the Microcontroller.



Programming Tip: The SP SFR, on startup, is initialized to 07h. This means the stack

will start at 08h and start expanding upward in internal RAM. Since alternate register

banks 1, 2, and 3 as well as the user bit variables occupy internal RAM from addresses

08h through 2Fh, it is necessary to initialize SP in your program to some other value if

you will be using the alternate register banks and/or bit memory. It's not a bad idea to

initialize SP to 2Fh as the first instruction of every one of your programs unless you are

100% sure you will not be using the register banks and bit variables.

DPL/DPH (Data Pointer Low/High, Addresses 82h/83h): The SFRs DPL and DPH

work together to represent a 16-bit value called the Data Pointer . The data pointer is used

in operations regarding external RAM and some instructions involving code memory.

Since it is an unsigned two-byte integer value, it can represent values from 0000h to

FFFFh (0 through 65,535 decimal).

Programming Tip: DPTR is really DPH and DPL taken together as a 16-bit value. In

reality, you almost always have to deal with DPTR one byte at a time. For example, to

push DPTR onto the stack you must first push DPL and then DPH. You can't simply

plush DPTR onto the stack. Additionally, there is an instruction to "increment DPTR."

When you execute this instruction, the two bytes are operated upon as a 16-bit value.

However, there is no instruction that decrements DPTR. If you wish to decrement the

value of DPTR, you must write your own code to do so.

PCON (Power Control, Addresses 87h): The Power Control SFR is used to control the

8051's power control modes. Certain operation modes of the 8051 allow the 8051 to go



into a type of "sleep" mode, which requires much, less power. These modes of operation

are controlled through PCON. Additionally, one of the bits in PCON is used to double the

effective baud rate of the 8051's serial port.

TCON (Timer Control, Addresses 88h, Bit-Addressable): The Timer Control

SFR is used to configure and modify the way in which the 8051's two timers

operate. This SFR controls whether each of the two timers is running or stopped

and contains a flag to indicate that each timer has overflowed. Additionally, some

non-timer related bits are located in the TCON SFR. These bits are used to

configure the way in which the external interrupts are activated and also contain

the external interrupt flags which are set when an external interrupt has occurred.

TMOD (Timer Mode, Addresses 89h): The Timer Mode SFR is used to

configure the mode of operation of each of the two timers. Using this SFR your

program may configure each timer to be a 16-bit timer, an 8-bit auto reload timer,

a 13-bit timer, or two separate timers. Additionally, you may configure the timers

to only count when an external pin is activated or to count "events" that are

indicated on an external pin.

TL0/TH0 (Timer 0 Low/High, Addresses 8Ah/8Ch): These two SFRs, taken

together, represent timer 0. Their exact behavior depends on how the timer is

configured in the TMOD SFR; however, these timers always count up. What is

configurable is how and when they increment in value.



TL1/TH1 (Timer 1 Low/High, Addresses 8Bh/8Dh): These two SFRs, taken

together, represent timer 1. Their exact behavior depends on how the timer is

configured in the TMOD SFR; however, these timers always count up. What is

configurable is how and when they increment in value.

P1 (Port 1, Address 90h, Bit-Addressable): This is input/output port 1. Each bit




it to a low level.

SCON (Serial Control, Addresses 98h, Bit-Addressable): The Serial Control

SFR is used to configure the behavior of the 8051's on-board serial port. This

SFR controls the baud rate of the serial port, whether the serial port is activated

to receive data, and also contains flags that are set when a byte is successfully

sent or received.

Programming Tip: To use the 8051's on-board serial port, it is generally necessary to

initialize the following SFRs: SCON, TCON, and TMOD. This is because SCON

controls the serial port. However, in most cases the program will wish to use one of the

timers to establish the serial port's baud rate. In this case, it is necessary to configure

timer 1 by initializing TCON and TMOD.

SBUF (Serial Control, Addresses 99h): The Serial Buffer SFR is used to send and

receive data via the on-board serial port. Any value written to SBUF will be sent out the



serial port's TXD pin. Likewise, any value which the 8051 receives via the serial port's

RXD pin will be delivered to the user program via SBUF. In other words, SBUF serves

as the output port when written to and as an input port when read from.

P2 (Port 2, Address A0h, Bit-Addressable): This is input/output port 2. Each bit




it to a low level.

Programming Tip: While the 8051 has four I/O port (P0, P1, P2, and P3), if your

hardware uses external RAM or external code memory (i.e., your program is stored in an

external ROM or EPROM chip or if you are using external RAM chips) you may not use

P0 or P2. This is because the 8051 uses ports P0 and P2 to address the external memory.

Thus if you are using external RAM or code memory you may only use ports P1 and P3

for your own use.

IE (Interrupt Enable, Addresses A8h): The Interrupt Enable SFR is used to enable and

disable specific interrupts. The low 7 bits of the SFR are used to enable/disable the

specific interrupts, where as the highest bit is used to enable or disable ALL interrupts.

Thus, if the high bit of IE is 0 all interrupts are disabled regardless of whether an

individual interrupt is enabled by setting a lower bit.

P3 (Port 3, Address B0h, Bit-Addressable): This is input/output port 3. Each bit

of this SFR corresponds to one of the pins on the Micro controller. For example,





it to a low level.



Auto reset Circuit:

R S T1 0 u F

2 2 p F

2 2 p F

8 . 2 k

4 - 1 2 M h z

V C C = + 5 v d c A T 8 9 C 5 1

9

1 8

1 9

2 9

3 0

3 1

1

2

3

4

5

6

7

8

2 1

2 2

2 3

2 4

2 52 6

2 7

2 8

1 0

1 1

1 2

1 3

1 4

1 5

1 6

1 7

3 9

3 8

3 7

3 6

3 53 4

3 3

3 2

R S T

X T A L 2

X T A L 1

P S E N

A L E / P R O G

E A / V P P

P 1 . 0

P 1 . 1

P 1 . 2

P 1 . 3

P 1 . 4

P 1 . 5

P 1 . 6

P 1 . 7

P 2 . 0 / A 8

P 2 . 1 / A 9

P 2 . 2 / A 1 0

P 2 . 3 / A 1 1

P 2 . 4 / A 1 2

P 2 . 5 / A 1 3

P 2 . 6 / A 1 4

P 2 . 7 / A 1 5

P 3 . 0 / R X D

P 3 . 1 / T X D

P 3 . 2 / I N T 0

P 3 . 3 / I N T 1

P 3 . 4 / T 0

P 3 . 5 / T 1

P 3 . 6 / W R

P 3 . 7 / R D

P 0 . 0 / A D 0

P 0 . 1 / A D 1

P 0 . 2 / A D 2

P 0 . 3 / A D 3

P 0 . 4 / A D 4

P 0 . 5 / A D 5

P 0 . 6 / A D 6

P 0 . 7 / A D 7

M I C R O C O N T R O L L E R

The auto reset circuit is a RC network as shown in the mother board circuit

diagram. A capacitor of 1-10mfd is connected in series with a 8k2 resister the R-

C junction is connected to the micro controller pin –9 which is reset pin. The reset

pin is one when ever kept high( logic 1) the programme counter (PC) content



resets to 0000h so the processor starts executing the programme. from that

location. When ever the system is switched ON the mother board gets power and

the capacitor acts as short circuit and the entire voltage appears across the

resistor, so the reset pin get a logic 1 and the system get reset, whenever it is

being switched ON.

Pull-UP Resisters:

A T 8 9 C 5 1

9

1 8

1 9

2 9

3 0

3 1

1

2

3

4

5

6

7

8

2 1

2 2

2 3

2 4

2 5

2 6

2 7

2 8

1 0

1 1

1 2

1 3

1 4

1 5

1 6

1 7

3 9

3 8

3 7

3 6

3 5

3 4

3 3

3 2

R S T

X T A L 2

X T A L 1

P S E N

A L E / P R O G

E A / V P P

P 1 . 0

P 1 . 1

P 1 . 2

P 1 . 3

P 1 . 4

P 1 . 5

P 1 . 6

P 1 . 7

P 2 . 0 / A 8

P 2 . 1 / A 9

P 2 . 2 / A 1 0

P 2 . 3 / A 1 1

P 2 . 4 / A 1 2

P 2 . 5 / A 1 3

P 2 . 6 / A 1 4

P 2 . 7 / A 1 5

P 3 . 0 / R X D

P 3 . 1 / T X D

P 3 . 2 / I N T 0

P 3 . 3 / I N T 1

P 3 . 4 / T 0

P 3 . 5 / T 1

P 3 . 6 / W R

P 3 . 7 / R D

P 0 . 0 / A D 0

P 0 . 1 / A D 1

P 0 . 2 / A D 2

P 0 . 3 / A D 3

P 0 . 4 / A D 4

P 0 . 5 / A D 5

P 0 . 6 / A D 6

P 0 . 7 / A D 7

1 0 k

P O R T - 0

V C C = + 5 V



The PORT0 and PORT2 of the MCS-51 architecture is of open collector type so

on writing logic 0 the pins are providing a perfect ground potential. Where as on

writing logic 1 the port pins behaves as high impedance condition so putting a

pull-up resister enables the port to provide a +5volt( logic 1). Port1 and Port3

are provided with internal pull-ups. A pull-up resister is normally a 10K resistance

connected from the port pin to the Vcc (+5) volt.

Crystal Oscillator

The 8051 family microcontroller contains an inbuilt crystal oscillator, but the

crystal has to be connected externally. This family of microcontroller can support

0 to 24MHz crystal and two numbers of decoupling capacitors are connected as

shown in the figure. These capacitors are decouples the charges developed on

the crystal surface due to piezoelectric effect. These decoupling capacitors are

normally between 20pf to 30pf. The clock generator section is designed as

follows,



The Microcontroller design consist of two parts

1) Hardware.

2) Software.

HARDWARE: The controller operates on +5 V dc, so the regulated + 5v is

supplied to pin no. 40 and ground at pin no. 20. The controller is used here need

not required to handle high frequency signals, so as 4 MHz crystal is used for

operating the processor. The pin no. 9 is supplied with a +5V dc through a push

switch to reset the processor .As prepare codes are store in the internal flash

memory the pin no. 31 is connected to + Vcc

Port assignment: -

P2.0, p2.1, are given to the bidirectional motor driver.



Port-1is used as input port to the motherboard.

P1.0 is used for right move.

P1. 1 is used for middle move.

P1.2 is used for left move.

Software:

Algorithm:

1. The controller check for the signal from the three receivers connected at

center, left and right of the antenna.

2. As long as the receivers did not get signal the motor continue rotating the

antenna.

3. Whenever the signals received by the center receiver then it stops the motor

movement.

4. Then The controller scans all the three sensors and take action as per the table

given bellow.

Receiver Position Motor movement

Left Rx Center Rx Right Rx Left mov. Right mov Stop

0 0 0 0 1 0

x 1 X 0 0 1

0 1 1 0 1 0

1 1 0 1 0 0

5. The motor again starts moving in the same direction as the target moves in the

same plane. The movement of motor decided as per the table given above.



The direction of search and movement remains continuous even if the all the

sensors are not receiving the required signal. The motor again stops when ever

the center receiver again receive the required signal.

i.



2 2 P F

C R Y S T A L2 2 P F

C 1

C

R S T

F R O M

S I G N A L

C O N D .

2 0

T O D C

M O T O R

D R I V E R

V C C

A T 8 9 C 5 1

9

1 8

1 9

2 9

3 0

3

1

1

2

3

4

5

6

7

8

2 1

2 2

2 3

2 4

2 5

2 6

2 7

2 8

1 0

1 1

1 2

1 3

1 4

1 5

1 6

1 7

3 9

3 8

3 7

3 6

3 5

3 4

3 3

3 2

R

S

T

X T A L 2

X T A L 1

P S E N

A L E / P R O G

E

A

/ V

P

P

P 1 . 0

P 1 . 1

P 1 . 2

P 1 . 3

P 1 . 4

P 1 . 5

P 1 . 6

P 1 . 7

P 2 . 0 / A 8

P 2 . 1 / A 9

P 2 . 2 / A 1 0

P 2 . 3 / A 1 1

P 2 . 4 / A 1 2

P 2 . 5 / A 1 3

P 2 . 6 / A 1 4

P 2 . 7 / A 1 5

P 3 . 0 / R X D

P 3 . 1 / T X D

P 3 . 2 / I N T 0

P 3 . 3 / I N T 1

P 3 . 4 / T 0

P 3 . 5 / T 1

P 3 . 6 / W R

P 3 . 7 / R D

P 0 . 0 / A D 0

P 0 . 1 / A D 1

P 0 . 2 / A D 2

P 0 . 3 / A D 3

P 0 . 4 / A D 4

P 0 . 5 / A D 5

P 0 . 6 / A D 6

P 0 . 7 / A D 7

4 0

M O T H E R B O

8 . 2 K



C. IR TRANSMITTER

The IR LED is also light emitting diode but the junction is made out of such

material that the transition of electron between the bands emits quanta of energy(

E=h ν ) having a particular frequency which is having a particular characteristic.

When a diode emits a particular characteristic signal having frequency in the

range of infrared then, that diode is called a infrared emitting diode. The IR data

transmitter is a high intensity IR signal transmitter.

In this section our aim is to transmit a continous. For that we have taken

elements as IR LED as a source and photo diode as a destination. Generally, we

have taken IR because IR is invisible to the eye, where as in case of LASER,

which is easily visible to the human eye by which will, alert the unauthorized

person. That is why we have taken IR as a transmitter which will transmit a

continuously IR signal. At the receiver end the photodiode will receive the IR

signal. if somebody tries to interrupt the IR signal at the transmitter end, the

receiver will decide the absence of the IR signal at the receiver end.

Operation:

Whenever the base voltage (12v) is high which is connected through a base

resistance Rb (1k-10k), the transistor (BC547/BC548) comes to saturation

condition (ON state) thus emitter current starts flowing towards the collector



junction which is connected through a collector resistance Rc (150E/2) and

connected to Vcc. Which makes an IR LED as a forward biased thus transmit a

continuous IR signal.

D. IR RECEIVER: Introduction:

A PHOTO DIODE is light sensitive device the junction of the photo diode is such

that it generates carriers when the light falls on it. There are different type of

diodes, which generates carriers in different magnitudes at different frequency

this depends on the nature and doping of the junction. The liberation of carriers

are very small in magnitude which is very much dependant on the frequency and

intensity of the light signal falling on the junction. In the forward biased condition

the majority carrier current is so high that the current generated due to fall of light

signal is very negligible. The photon bombardment cause the avalanche break

down of the junction and generate current which is in the order of 100s micro

ampere to few 10s of mA, due to the above mentioned causes the photo diodes

to connected in the reverse biased condition. In the reverse biased condition the

normal current is always in the order of few microamperes, the current generated

due to fall of light signal on the junction is also in the order of microampere so the

net current through the diode is appreciably increased. The same current pass

through the resistance connected in series and drop across the resistance is

increased. There are two types of arrangements very much widely used in the

circuits, as shown in the Fig.1 and Fig.2.



R

VCC

D 1 Vout

D 1

Vout

Fig.1

R

VCC

Fig.2

If the diode junction is exposed with visible light or invisible light like Infrared /

Laser in the circuit shown in fig.2, the diode current will rise, possibly to as high

as 1mA,producing a significant output across R. In use, the photodiode is

reversed biased and the output voltage is taken from across a series-connected

load resistor.

Operation:

In this project in the data/signal receiving section, the photodiode is used as

signal (data) detector purpose to detect the IR signal (data) from the IR

transmitter LED section. Whenever the signal is transmitted from the IR

transmitter LED, the signal is received at the photodiode receiving section. The

receiving signal is very weak in strength, for that we used an amplifier. The

output of the photodiode is given as input to the amplifier (Op-amp LM393) which

is configured as an Voltage Comparator and the reference voltage is set at non-

inverting terminal of the operational amplifier. There is a 10K variable resistor

which is connected between +12 Volt and Ground and the variable terminal is

connected to the OP-AMP (Inverting terminal) for providing the threshold value.



The output of the LM393 swings in between +Vsat and –Vsat, even for a small

variation of signal across the threshold value. That output signal is not

compatible with the Microcontroller because of the high current; that output from

the Op-amp is given to the signal conditioning i.e. the signal is given to the base

of the transistor through a base resistance between 1K –43K and the collector is

connected to Vcc = +5Volt in series with a 10K resistance and the output is taken

from the collector. The emitter is grounded. Thus the output signal is compatible

with the Microcontroller and that signal is connected to the RxD pin of the

Microcontroller. Thus the transmitted data is received at the receiving section.

The transmitted signal must fall pin pointed to the photodiode junction in order to

receive the correct data at the receiver end without any interference or

malflactuation.

Introduction

The relays used here having following specifications.

Operating voltage = 12V DC

Coil resistance = 400Ω

Capacity of contact point = 7A, 230V

Type = single contact

NO/NC



The relay requires 12 volts and current= 12 volt/400Ω = 30mA. The driver now

require for driving this relay must be designed for translating the TTL logic value

into 12 volts and 100mA current.

The TTL / CMOS IC cannot provide this much of current. In normal practice, it

desirable to draw 60 to 70µ A current from the TTL / CMOS IC, as the output to

load current requirement is very high a transistor driver is required. This driver

circuit is configured with discrete elements. BC547. The common emitter

amplification factor is approximately 200 for BC547.If the load current is

considered about 40mA then, the base current will be around = 40/200= 40x10-

3/200 = 0.2mA.

In this arrangement the base current is design for 80mA current.



I R R e c e i v e r

V C C

O / P

1 0 0 k

-

+

L M 3 9 3

3

2

1

8

4

P H O T O D I O D E

1 5 0 E / 2 W

1 5 k

B C 5

I R T r a n s m i t t e r

V C C

I R L E D

V C C

1 0 K

I R T r a n s m i t t e r a n d R e c

6 8 K

3 3 0 E

1 0 K

I R L

E. Bi- directional motor driver:

Here, in this section the Bi-directional DC motor driver is designed by using a

relay driver to drive the DC motor in both directions.

INTRODUCTION TO ELECTRO MAGNETIC RELAY

These are very much reliable devices and widely used on field. The operating

frequency of these devices are minimum 10-20ms.That is 50Hz – 100Hz.The

relay which is used here can care 7Amp currents continuously. The

electromagnetic relay operates on the principle magnetism. When the base



voltage appears at the relay driver section, the driver transistor will be driver

transistor will be driven into saturation and allow to flow current in the coil of the

relay, Which in turn create a magnetic field and the magnetic force produced due

to that will act against the spring tension and close the contact coil. Whenever

the base voltage is withdrawn the transistor goes to cutoff .So no current flow in

the coil of the relay. Hence the magnetic field disappears so the contact point

breaks automatically due to spring tension. Those contact points are isolated

from the low voltage supply, so a high voltage switching is possible by the help of

electromagnetic relays.

The electromagnetic relays normally having 2 contact points. Named as normally

closes (NC) NO normally open (NO). Normally closed points will so a short CKT

path when the relay is off. Normally open points will so a short CKT path when

the relay is energized.



V c c = + 1 2 v

B C 5 4 7

B C 5 4 7

1 . 5 k

V c c = + 1 2 v

1

0

u

F

R

E

L

A

Y

+

-

1

N

4

0

0

7

R

E

L

A

Y

1 . 5 k

D C M O T O R D R I

M

V c c = + 1 2 v

1

0

u

F

1

N

4

0

0

7



F.PMDC Motor Driver

The D.C. Motor used in this project operates at 12 volt and carries approximately

400mA of current. The motor driver is designed to inter face the motor with micro

controller. The micro controller out put is +5volt and can maximum give a current

of 5mA. The driver stage changes the current and voltage level suitably to drive

the motor. The driver stage not only drives the motor but also helps to control

the direction of rotation. As the output current (Ic) is large the driver section

requires a Darlington pair to switch the load. The Darlington pair I.C. TIP 122 is

used here for designing. There are four ICs used here but two of those switched

for one direction and other two will be switched for opposite direction rotation of

the D.C. motor. The design principle of the driver section is as follows.

The motor takes approximately 400mA at 12 volt D.C., The power transistors can

have amplification factor maximum 60 to 70 as per this assumption the base

current required to switch on the transistor is approximately

Ib= (Ic/beta) =400mA/60 =6.7 mA

This current is too high to supply as a base current, more over the Microcontroller can not

supply that much current to drive the transistor so, a darling ton pair is required to limit

the base current with in 100 micro amp. To 2 mA.



R

O

M

P

W

M

F

I

L

T

E

R

1 . 5 k

T I P 1

M

V c c = +

C M O T O R D R

m



G. RELAY DRIVER:

The relay driver is design by using a BC547 transistor .The relay used here

having the specification as follows:

Coil resistance = 400ohm

Coil voltage= 12Vdc

Contact capacity= 230V, 7A

The above specification indicates that the coil requires 12V dc and 200mA

current dc. The TTL/CMOS can’t supply more then 50µ A current. So driver

section is very much required. BC547 has a typical current gain of 200 and

maximum current capacity of 1A. So a typical base current of 200 µ A can trigger

to on the relay.

This application is in some ways a continuation of he discussion introduced for diodes

how the effects of inductive kick can be minimized through proper design. In the below

figure (a), a transistor is used to established the current necessary to energize the relay in

the collector circuit. With no input at the base of the transistor, the base current, collector

current, and the coil current are essentially 0A, and the relay sits in the un-energized state

(normally open, NO).



However when a positive pulse is applied to the base, the transistor turns ON,

establishing sufficient current through the coil of the electromagnet to close the relay.

Problem can be now develop when the signal is removed from the base to turn OFF the

transistor and de-energized the relay. Ideally, the current through he coil and the

transistor will quickly drop to zero, the arm of the relay will be released, and the relay

will simply remain dormant until the next “ON” signal.

However we know from our basic circuit courses that the current through the coil cannot

change instantaneously, and in fact the more quickly changes, greater the induced voltage

across the coil as defined by,

V L = L (di L / dt).

In this case, the rapid changing current through the coil will develop a large voltage

across the coil with the polarity shown in figure (a), which will appear directly across the

output of the transistor. The chances are likely that its magnitude will exceeds the

maximum ratings of the transistor, and the semiconductor device will be permanently

damaged. The voltage across the coil will not remain at its highest switching level but

will oscillate as shown until its level drops to zero as the system settles down.



The destructive action can be subdued by placing a diode across the coil as shown in

below figure (b). During the “ON” state of the transistor, the diode is back biased: it sits

like an open circuit and does not affect the thing. However, when the transistor turns

“OFF”, the voltage across the coil will reverse and will forward biased the diode, placing

the diode in its “ON” state. The current through the inductor established during “ON”

state of the transistor can then continue to flow through the diode, eliminating the severe

change in current level. Because the inductive current is switched to diode almost

instantaneously after the “OFF” state is established, the diode must have a current rating

to match the current through the inductor and the transistor when is in “ON” state.

Eventually, because of the resistive elements in the loop, including the resistance of the

coil windings and the diode, the high frequency (quickly oscillating) variation in voltage

level across the coil will decay to zero and the system will settle down.

R b

V i Q 1

N C

-

C O M V L

N O

V c c

+

At turn-off

VCE

≈ VL

+

-

(a)

Vi

t

VON

VOFF

Trouble!

VL

t

High voltage spike

At turn OFF

(b)

When transistor

turned “OFF”

V L

R b

+

V i Q 1

N C

C O M

N O-

V c c

D 1



H. SIGNAL CONDITIONING

The output form the input signal i.e. comparator or any other external circuit must be

compatible with the µ -controller, because the µ -controller can takes 5V as input

voltage and gives a 5V as output voltage. That for we need a signal conditioning circuit

as given in the below figure.

B C 5 4 71 .5 k

1 0 k

( 1 : 0 )

V C C = + 5 vV C C = + 5 v

( 1 : 1 )

I N P U T

1 . 5 k

S I G N A L C O N D I T I O N I N G

O U T P U T

1 0 k

O U T P U T

B C 5 4 7

I N P U T

fig..1:1

In the fig1: 1, whenever the base voltage is HIGH the transistor comes to

saturation condition i.e. the collector current flows to the emitter which gives a high

voltage at the output corresponding to Vcc given at the collector. The output is taken

from the emitter junction through a current limiting resistance and the output signal is

given to the µ - controller or any other circuit which needs a compatible (5V) voltage.

Similarly, whenever the base voltage is LOW the emitter current flows from the emitter

junction of the transistor, which gives a low voltage at the output corresponding to GND.



The output is taken from the emitter junction through a current limiting resistance and the

output signal is given to the µ - controller or any other circuit which needs a compatible

(5V) voltage.

fig..1:0

In the fig1: 0, whenever the base voltage is HIGH the transistor

comes to saturation condition i.e. the emitter current flows to the collector which

gives a low voltage at the output corresponding to GND. The output is taken from

the collector junction through a current limiting resistance and the output signal is

given to the µ - controller or any other circuit which needs a compatible (5V/0V)

voltage. Similarly, whenever the base voltage is LOW the collector current flows

from the collector junction of the transistor, which gives a high voltage at the

output corresponding to Vcc. The output is taken from the emitter junction

through a current limiting resistance and the output signal is given to the µ -

controller or any other circuit which needs a compatible (5V/0V) voltage.



1 0 K

S I G N A L C O N D I T I O N I N

1 . 5 K

B C 5 4 7

D A T A I N P U T

V C C



I. COMPUTER INTERFACING (SIU)

The link

The physical link between computers consists of the wires or other medium that carries

information from one computer to another, and the interface that connects the medium to

the computers.

The requirements of a link help to determine which interface to use and what

medium to use to connect the nodes. In the types of systems described in this

book, the distance between computers may range from a few feet to a few

thousand feet. The time between communications may be shorter than a second,

or longer than a week. The number of nodes may range4 from two to over two

hundred.

Most links use copper wire to connect computers, often inexpensive twisted-pair

cable. The path may be a single data wire and a ground return, or a pair of wires

that carry differential signals. Other options include fiber-optic cable, which

encodes data as the presence of absence of light, and wireless links, which send

data as electromagnetic (radio) or infrared signals in the air.

For most projects, there is a standard interface that can do the job. Most of the

links described in this book use one of two popular interfaces: RS-232 for

shorter, slower links between two computers, or RS-485 for longer or faster links

with two or more computers.

An interface may use existing ports on the computers, or it may



require added ports or adapters. Most PCs have at least one RS-232 interface,

and an RS-232 or RS-485 interface is easily added to a PC or microcontroller.

Table 1-1 compares RS-232 and RS-485 to other interfaces that a monitoring or

control system might use.

RS-232 is popular because it’s widely available, inexpensive, and can use longer cables

than many other options. RS-485 is also inexpensive, easy to add to a system, and support

even longer distances, higher speeds, and more nodes than RS-23

Interface Format Number of Devices

(maximum)

Length(maximum,

feet)

Speed(maximum,

bits/sec.)RS-232(EIA/TIA-232)

Asynchronousserial

2 50-100 20k (115kwith somedrivers)

RS-485(TAI/EIA-485)

Asynchronousserial infrared

32 unit loads 4000 10M

IrDA Synchronousserial

2 6 115k

Microwire Synchronousserial

8 10 2M

SPI Synchronousserial 8 10 2.1M

I2C Synchronousserial

40 18 400K

USB Synchronousserial

127 16 12M

Fire wire Serial 64 15

IEEE-488(GPIB)

Parallel 15 60

Ethernet Serial 1024 1600

MIDI Serial current

loop

2 15

ParallelPrinter Port

Parallel 2,or 8 withdaisy-chainsupport

10-30



USB (Universal Serial Bus) and Fire wire (IEEE-1384) are new, high-

speed, intelligent interfaces for connecting PCs and other computers to various

peripherals. USB is intended to replace the standard RS-232 and Centronics

printer ports as the interface of choice for modems and other standard

peripherals. Fire wire is faster and designed for quick transferring of video, audio,

and other large blocks of data.

Ethernet is the familiar network interface used in many PC networks. Its fast and

capable, but the hardware and software required are complex and expensive

compared to other interfaces.

The alternative to serial interfaces is parallel interfaces, which have multiple data

lines. Because parallel interfaces transfer multiple bits at once, they can be fast.

Usually there is just one set of data lines, so data travels in one direction at a

time.

Over long distances of with more than two computers in a link, the cabling for

parallel interfaces becomes too expensive to be practical.

The Centronics parallel printer interface predates the PC and just about every PC

has included a Centro-compatible interface. The IEEE-1284 standard defines

new connectors, cables, and high-speed protocols for ports 17 lines. Because

the interface has been standard on all PCs, its been pressed into service as an

interface for scanners, external disk driver, data-acquisition devices, and many

other special-purpose peripherals.



IEEE-488, which began life as Hewlett-Packards GPIB (General-purpose

Interface Bus) is another parallel interface popular in instrumentation and control

applications.

2 Formats and Protocols

3 The computers in a serial link may be of different types, but all must

agree on conventions and rules for the data they exchange. This

agreement helps to ensure that every transmission reaches its

destination and that each computer can understand the messages sent

to it.

4 Sending Serial Data

In a serial link, the transmitter, or driver, sends bits one at a time, in sequence. A

link with just two devices may have a dedicated path for each direction or it may

have a single path shared by both, with the transmitters taking turns. When there

are three or more devices, all usually share a path, and a network protocol

determines when each can transmit.

One signal required by all serial links is a clock, or timing reference, to control the

flow of data. The transmitter and receiver use a clock to decide when to send and

read each bit. Two types of serial-data formats are synchronous and

asynchronous, and each uses clocks in different ways.

Synchronous Format

In a synchronous transmission, all devices use a common clock generated by

one of the devices or an external source. Figure 2-1A illustrates. The clock may

have a fixed frequency or it may toggle at irregular intervals. All transmitted bits



are synchronized to the clock. In other words, each transmitted bit is valid at a

defined time after a clock transition (rising or falling edge). The receiver uses the

clock transitions to decide when to read each incoming bit. The exact details of

the protocol con vary. For example, a receiver may latch incoming data on the

rising or falling clock edge, or on detecting a logic high or low level. Synchronous

formats use a variety of ways to signal the start and end of a transmission,

including Start and Stop bits and dedicated chip-select signals.

Synchronous interfaces are useful for short links, with cables of 15 feet or less or

even between components on a single circuit board. For longer links,

synchronous formats are less practical because of the need to transmit the clock

signal, which requires an extra line and is subject to noise.

Asynchronous Format

In asynchronous (also called asynchronous and non-synchronous)

transmissions. The link doesn’t include a clock line, because each end of the link

provides its own clock. Each end must agree on the clock’s frequency, and all of

the clocks must match within a few percent. Each transmitted byte includes a

Start bit to synchronize the clocks, and one or more Stop bits to signal the end of

a transmitted word.

The RS-232 port on PCs uses asynchronous formats to communicate with

modems and other devices. Although an RS-232 interface can also transfer

synchronous data, asynchronous links are much lore common. Most RS-485

links also use asynchronous communications.



An asynchronous transmission may use any of several common formats.

Probably the most popular is 8-N-1, where the transmitter sends each data byte

as 1 Start bit, followed by 8 data bits, beginning with bit 0 (the LSB, or least

significant bit), and ending with 1 Stop bit. Figure 2-1B illustrates.

The N in 8-n-1, indicates that the transmissions don’t use a parity bit. Other

formats include a parity bit as a simple form of error checking. Parity can be

Even, Odd, Mark, or Space. Table 2-1 illustrates Even and Odd parity. With Even

parity, the parity bit is set or cleared so that the data bits plus the parity bit

contain an even number of 1s. With Odd parity, the bit is set or cleared so that

these bits contain an odd number of 1s. An example format using parity is 7-E-1.

The transmitter sends 1 Start bit, 7 data bits, 1 parity bit, and 1 Stop bit. Here

again both ends of the link must agree on the format. Mark and space parity are

forms of Stick parity: with Mark parity, the parity bit is always 1, and with Space

parity it’s always 0. These are less useful as error indicators but one use for them

is in

the 9-bit networks described in chapter 11. These networks use a parity bit to

indicate whether a byte contains an address of data.

Other, less common format use different numbers of data bits. Many serial ports

support anywhere from 5 to 8 data bits, plus a parity bit.



Table 2-1: With Even parity the data bits plus the parity bit contain an even

number of 0s. With Odd parity the data bits plus the parity bit contain an odd

number of 0s.

A link’s bit rate is the number of bits per second transmitted or received per unit

of tome, usually expressed as bits per second (bph). Baud rate is the number of

possible events, or data transistors per second. The two values are often

identical because in many links, including those described in this book, each

transition period represents a new bit. Over phone lines, high-speed modems

use phase shifts and other tricks to encode multiple bits in each data period, so

the baud rate is actually much lower than the bit rate.

All of the bits required transmitting a value from Start to stop bit form a word . The

data bits in a word form a character . In some links, the characters actually do

represent text characters (letters or numbers), while in others the characters are

binary values that have nothing to do with text. The number of characters

transmitted per second equals the bit rate times the number of bits in a word.

Adding one SATART AND ONE stop bit to a byte increases the transmission

time of each byte by 25 percent (because there are 10 bits per byte instead of

Data Bits Even Parity Bits Odd Parity Bits0000000 0 1

0000001 1 0

0000010 1 0

0000011 0 1

0000100 1 0

1111110 0 1

1111111 1 0



just 8). With 8-N-1 formats a byte transmits at 1/10 the bit rate: a 9600 bits-per-

second link transmits 96o bytes per second.

If the receiver requires a little extra time to accept received data, the transmitter

may stretch the Stop bit to the width of 1.5 or 2 bits. The original purpose of the

longer stop bit was to allow tome for mechanical Teletype machines to settle to

an idles state.

There are other ways to generate Start and Stop bits without using a full bit

width. The USB interface uses varying voltages to indicate start and stop. Of

course this requires hardware that supports these definitions.

System Support

Fortunately, the programming required to send and receive data in asynchronous

formats is simpler than you might expect. PCs and many micro controllers have a

component called a UART (universal asynchronous receiver/transmitter) that

handles mast of the details of sending and receiving serial data.

In PCs, the operating system and programming languages include support for

programming serial links without having to understand ever detail of the UART’s

architecture. To open a link the application selects a data rate and other settings

and enables communications at the desired port. To send a byte the application

writes the byte to the transmit buffer of the selected port and the RART sends the

data, bit by bit in the requested format adding the Stop, Start, and parity bits as

needed. In a similar way, received bytes are automatically stored in a buffer. The

UART can trigger an interrupt to notify the CPU, and thus the application of

incoming data and other events.



Some micro controllers don’t include a UART and sometimes you need more

UARTs than the microcontroller has. In this case there are two options: add an

external UART, or simulate a UART in program code. Parallax’s Basic Stamp is

an example of a chip with a UART implemented in code.

Transmitting a Byte

Understanding the details of how a byte transmits isn’t strictly necessary in order

to design, program, and use a serial link, but the knowledge can be useful in

troubleshooting and selecting a protocol and interface for a project.

The Bit Format

Figure 2-1B showed how a byte transmits in 8-N-1 format. When idle the

transmitter’s output is login 1. To signal the beginning of a transmission, the

output sends a logic 0 for the length of one bit. This is the Start bit. At 300 bps a

bit is 3.3 milliseconds, while at 9600 bps, it’s 0.1 millisecond.

After the Start bit the transmitter sends the 8 data bits in sequence beginning

with bit0, the least-significant bit (LSB). The transmitter then sends a logic 1,

which functions as the Stop bit. The output remains at logic 1 for at least the

width of one .

Each end of the link uses a clock of 16 times the bit rate to determine when to

send and read each bit.

bit. Immediately following this, or at any time after the transmitter may send a new Start

bit to announce the beginning of a new byte.



At the receiving end the transition from logic 1 to the Start bit’s logic 0 signals

that a byte is arriving and determines the timing for detection the following bits.

The receiver measures the logic state of each bit near the middle of the bit. This

helps ensure that the receiver reads the bits correctly even if the transmitting and

receiving clocks don’t match exactly.

Some interface, such as RS-232, use inverted voltages from those shown: the

Stop bit is a negative voltage and the Start bit is positive.

The UART typically uses a receive clock that is 16 times the bit frequency: if the

data rate is 300 bits per second, the receive clock must be 4800 bits per second.

As Figure 2-2 shows, after detecting the transition that signals a start bit, the

UART waits 16 clock cycles for the start bit to end, then waits 8 more cycles to

read bit 0in the middle of the bit. It then reads each of the following bits 16 clock

cycles after the previous one.

If the transmitting and receiving clocks don’t match exactly, the receiver will read

each successive bit closer and closer to an edge of the bit. To read all of the bits

in a 10-bit word correctly, the transmit and receive clocks should vary no more

than about three percent. Any more than this and by the time the receiver tries to

read the final bits, the timing may be off by so much that it will read the bits either

before they’ve begun or after they’ve finished. However the clocks only need to

stay in sync for the length of a word, because each word begging with a new

Start bit that resynchronizes the clocks.

Because of the need for accurate timing, asynchronous interfaces require a

stable timing reference. Most are controlled by a crystal or ceramic resonator.



For best results, the frequency of the reference should allow even division by the

frequencies the receive clonks use for standard bit rates. In PCs, the standard

UART clock frequency is 1.8432 Mhz. Division by 16 gives 115,200, which is the

top bit rate the UART supports.

In a microcontroller, the chip’s main timing crystal usually serves as a reference

for hardware timing that controls the UART’s clock. In the 8051 family, the hard

timers run at 1/12 the crystal frequency. With a crystal of 11.0592 Mhz the fastest

UART is 921,600Hz,which allows a bit rate of 57,600 bps.

As a way of eliminating errors due to noise, some UART’s like the 8051

microcontroller’s, take three samples on the middle of each bit, and use the logic

level that matches two or more of the samples.

Auto detecting the Bit Rate

The ultimate in user convenience is a link with auto baud ability, where the two

ends automatically configure themselves to the same bit rate. There are two

ways to do this. In each, one node (I’ll call it the adjustable node) detects the bit

rate of the other (the fixed node) and adjusts its bit rate to match.

The first method requires no special hardware or hardware-level programming.

When the node wants to establish communications, it repeatedly sends a

character, with a pause between each. The character may be a null (Chr (0)), or

any ASII character (through Chr (127), as long as the most significant data bit,

which is the last one to transmit, is 0.



The adjustable node begins at its highest bit rate. When it detects that a byte has arrived,

it waits long enough for a bytes to transmit at the lowest expected bit rate (33

milliseconds at 300 bps), then reads the received byte or bytes.

If the receiver detects more than one character, its bit rate doesn’t match the

transmitter’s, so it tries again, using the next lower bit rate. When it detects one

and only one character, it has the corrects bit rate. As an extra check, it can

verify that the received character matches an expected value. The adjustable

node then sends an acknowledgment to the fixed node, which stops sending he

characters, and communications can begin.

Why does this routine work? When the receiver’s bit rate is faster than the

transmitter’s, the receiver finishes reading the character while the final bits are

still arriving. (The character will cause a framing error if the receiver doesn’t see

a logic 1 where it expects to find the Stop bit, but this is unimportant here.) After

the receiver thinks the character has finished transmitting, any received 0 looks

like a

Data formats

The data bits in a serial transmission may represent anything at all, including

commands, sensor readings, status information, error codes, or text messages.

The information may be encoded as binary or text data.

Binary Data

With binary data, the receiver interprets a received byte as a binary number with

a value from 0to 255. The bits are conventionally numbered 0 through 7, with

each bit representation the bit’s value (0 or 1) multiplied by a power of 2. For

example, in Visual-Basic syntax:



Bit 0 = Bit Value * (2^0)



A byte of 1111 1111 translates to 255, or FFh, and 0001 0001 translates to 17, or

11h. In asynchronous links, bit 0, the least-significant bit (LSB), arrives first, so if

you’re looking at the data on an oscilloscope or logic analyzer, remember to

reverse the order when translation to conventional notation of most-significant-bit

(MSB) first.

Text Data

Binary data works fine for many links. But some links need to send messages or

files containing text. And for various reasons, a link may also send binary data

encoded as text.

To send text, the program uses a code that assigns a numeric value to each text

character. There are several coding conventions. One of the most common is

ASCII (American Standard Code for Information Exchange), which consists of

128 codes and requires only seven data bits. An eight bit, if used, may be 0 or a

parity bit. ANSI (American National Standards Institute) text uses 256 codes, with

the higher codes representing special and accented characters. In the IBM ASCII

text used on the original IBM PC, many of the higher codes represented line-and

box-drawing characters used by many DOS programs used to add simple

graphics to text screens and printouts.

Other formats use 16 bits per character, which allows 65.536 different

characters. The Unicode standard supports hundreds of additional alphabets.



While DBCS (double-byte character set) is an earlier standard that supports

many Asian languages.

The examples in this book use ANSI/ASCII text, which is the format used by

Visual Basic’s MSComm control.

ASCII Hex

Text mode is the obvious choice for transferring string variables of files that

contain text. But you can also use text to transfer binary data, by expression the

data in ASCII Hex format. Each byte is represented by a pair of ASCII codes that

represent the byte’s two hexadecimal characters. (Appendix Chas mare on

hexadecimal and other number systems.) This format can represent any value

using only the ASCII codes 30h through 39h (for 0throuth 9) and 41h to 46h (for

A through F).

Instead of sending one byte to represent a value from 0 to 255, the sending

device sends two, one for each character in the hex number that represents the

byte. The receiving computer treats the values like ordinary text. After a

computer receives the values, it can process or use the data any way it wants,

including converting it back to binary data.

For example, consider the decimal number 163

Express as a binary number, it’s

1010 0011

In hexadecimal, it’s A3h (or & hA3 in Visual-Basin syntax)

The ASCII codes for “A” and “3” are 41h, 33h



So the binary representation of this value in ASCII hex consists of these tow

bytes:

01000001 00110011

A serial link using ASCII Hex format would send the value A3h by transmitting

these two bytes.

A downside of using ASCII Hex is that each data byte requires tow characters, so

data takes twice as long to transfer. Also, in most cases the application at each

end will at some point have to convert between ASCII hex and binary.

Still, ASCII Hex has its uses. One reason to use it is that it frees all of the other

codes for other uses, such as handshaking codes or an end-of-file indicator. It

also allows protocols that only support 7 data bits to transmit any numeric value.

Other potions are to send values as ASCII decimal, using only the codes for 0

through 9, or ASCII binary, using just 0 and 1. The basic Stamp has built-in

support for these as will as for ASCII Hex.



5

T O S E R I

1 0 u F

M A X 2 3 2

7

5

M O T H E R B O A R D

1

0

u

F

2

2

1

1 0 u F

1 0

V c c = + 5 v

1 0 u F

3

P 3 . 1 ( T x D )

1 6

3

8

C O N N E

46

0

. 1

u

F

S E R I A L P O R T I

1 5

0-12Vac/1Amp



J. BUZZER DRIVER

This section interfaces one audible piezo electric buzzer with the controller. The

controller activates the buzzer whenever there is any fault appears in any of the channel.

PIEZO ELECRTIC BUZZER:

It is a device that converts electrical signal to an audible signal (sound signal).The

Microcontroller cannot drive directly to the buzzer, because the Microcontroller cannot

give sufficient current to drive the buzzer for that we need a driver transistor (BC547),

which will give sufficient current to the buzzer.Whenever a signal received to the base of

the transistor through a base resistance (1.5k) is high, the transistor comes to saturation

condition i.e. ON condition thus the buzzer comes to on condition with a audible sound.

Similarly, whenever the signal is not received to the base of the transistor, thus the

transistor is in cut-off state i.e. is in OFF state thus the buzzer does not gets activated.



BUZZER DRIVER

1 . 5 K

B C 5 4 7

DATA

INPUT

BUZZER

V C C

K. LED INDICATOR

The indicator section consists of a light emitting diode and its driver circuit is

designed on the basis of current required to glow the light emitting diode. Here

the driver circuit is required for the following functionality.

1) The Microcontroller cannot provide adequate current for glowing the LED.

The LEDs requires a current between 10mA to 20mA of current to glow.

2) The driver circuit provides current to the load from a separate source, so

the load current used not pass through the Microcontroller.

3) The driver circuit activates the load on receipt of a logic signal from the

Microcontroller and of the load in the absence of the signal as he current



requirement Is very less to glow a LED a single stage driver is sufficient to

drive the load. The driver circuit is nothing other than a perfect a transistor

switch. The driver transistor goes in to saturation on receipt of base signal

and drives into cut-off region, in absence of base signal.

The driver designs around a BC548/BC547 transistor and designed for a

working voltage of +5 V dc and 10mA current.

Rc= Vcc-VCEsat = 12-0.2V

IC 10mA

= 1.18KΩ

Ib=Ic/β =10mA/200=5x10-5 A=50x10-6A

=50µ A

As per the design a 50µ A current is sufficient to trigger the driver circuit. As

this current is very small and to avoid mistriggering a base current of 100µ A

is assumed

VB-IBRB-VBE=0

⇒ IBRB = 5-0.7

RB = 5-0.7V/100µ A = 4.3/100 MΩ

= 0.043x10-6Ω

= 43KΩ

On approximation 68K is connected by calculating back

IB = 4.3/68K = 60≅ 70µ A



Which is adequate to avoid mis-triggering level also this amount of current

can be drawn from the Microcontroller without any problem.

The indicator section consists of 8 no of driver with 8 no of LED as indicator

load. The circuit diagram is enclosed.

3 3 0 E

L E D I N D I C A T O R

6 8 k

B C 5 4 7

D A T A I N P U T

V C C

L E D



FUTURE EXPANSION

This project is limited to its scope due to the constraint of time and cost. This project can

be developed with more sophistication and advanced facilities as follows,

1. The present algorithm is developed on scanning method there is no

procedure to optimize the antenna position for receiving maximum

signal. A fuzzy logic algorithm can be implemented for precession

control of antenna position.

2. The antenna designed in this project moves in one plane and don’t give

any information regarding the axial movement of the target and also

the distance of the target. A work on that regard can be carried out.

3. The target search and follow up is carried out in one plane but that can

be extended in multiple planes.

Computer interface also can be implemented to see the position of the target in

the computer screen.

CONCLUSION

This project worked satisfactorily in the laboratory condition.The antenna detects an

object from a distance of 10 ft. adjusting the transmitter and receiver power can increase

range of detection.

pc interfacednmissile firing system

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