web based robotics

8/3/2019 Web Based Robotics

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WEB BASED TELEMATICS APPLICATION FOR

ROBOTICS

A P R O J E C T R E P O R T

S u b m i t t e d b y

P R A D E E S H . P . K

R A K E S H K R I S H A N . P

A N O J . R . S

S U J I T H M O H A N . M

i n p a r t i a l f u l f i l l m e n t f o r t h e a w a r d o f t h e d e g r e e

o f

B A C H E L O R O F E N G I N E E R I N G

i n

E L E C T R O N I C S A N D C O M M U N I C A T I O N

E N G I N E E R I G

U D A Y A S C H O O L O F E N G I N E E R I N G , V E L L A M O D I .

A N N A U N I V E R S I T Y : C H E N N A I 6 0 0 0 2 5

A P R I L 2 0 1 0

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ANNA UNIVERSITY: CHENNAI 600 025

BONAFIDE CERTIFICATE

This is to certify that the project report ” W E B B A S E D

T E LE M AT I CS A P PL I CA T IO N F O R R OB O TI C S” i s t h e

b o na f id e w or k o f “ ** * ** ” w h o c a rr i ed o ut t h e p r o j ec t

w o r k u n d e r m y s u p e r v i s i o n.

SIGNATURE SIGNATURE

MRS.N.VIDHYA LEKSHMI M.Tech MR.N.SATHEESH KUMAR M.E

HEAD OF THE DEPARTMENT, SUPERVISOR,

Electronics and Communication Electronics and Communication

Engineering, Engineering,

Udaya School Of Engineering, Udaya School Of Engineering,

Vellamodi-629 204. Vellamodi-629 204.

EXTERNAL EXAMINER INTERNAL EXAMINER

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TABLE OF CONTENTS

CHAPTER TITLE PAGE NO

ABSTRACT 5

1. INTRODUCTION 5

1.1 Block Diagram 61.2 Circuit Diagram 6

2. HARDWARE DESCRIPTION

2.1 Introduction 7

2.2 Description 7

2.2.1 Memory Unit 8

2.2.2 Central Processing Unit 9

2.2.3 Input Output Unit 10

2.2.4 Serial communication 11

2.2.5 Timer Unit 13

2.2.6 AT89C52 MICROCONTROLLER 14

2.2.7 Description 14

2.2.8 Special Function Registers 15

3. MICROCONTROLLER INTERFACING

3.1 DC Motor

3.1.1 Introduction 16

3.1.2 Theory of DC motor speed control 17

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3.1.3 Speed Sensing Mechanism 18

3.1.4 Speed Encoders 20

3.1.5 Working Theory of H-Bridge 22

3.1.6 L293D Dual H-Bridge Motor Driver 23

3.2 RS232 serial connector pin assignment 25

3.3 Ultrasonic Sensor

4. DESCRIPTION OF DEVELOPMENT SYSTEM

4.1 Cross Compilers 26

4.1.1 Introduction to Keil 26

4.1.2 Functioning of Keil 27

4.1.3 Development tools in keil 27

4.1.4 C51 Optimizing C Cross Compiler 28

4.1.5 A51 Macro Assembler 29

4.1.6 BL51 Code Banking Linker/Locator 30

4.1.7 OC51 banked object file converter 30

4.1.8 OH51 object hex converter 30

4.1.9 µVISION/51 FOR WINDOWS 31

4.2 TARGET PROCESSOR 32

5. APPLICATION SOFTWARE

5.1 Application software description 35

5.2 Screen Shots 36

6. CONCLUTIONS 37

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ABSTRACT

In this project an obstacle sensing and object guiding Robot is

designed. Major problem in robot design is to detect an obstacle in front of it

to avoid collision. In this project, an electronic solution is attempted for this

problem. We use a pair of ultrasonic sensor acting as an artificial eye for the

robot. The ultrasonic transmitter would transmit the ultrasonic wave from

the robot. Incase the robot meet an obstacle within the specific range from

the transmitter, the reflected waves are sensed by the ultrasonic receiver

which is placed at the close proximity of the transmitter. The system will

have an amplifier which would amplify this received signal and fire an

interrupt signal to the Embedded Microcontroller. The Embedded

microcontroller would then fire a warning alarm to the robot enabling the

user to take necessary diversion to avoid collision. This project is of

immense use in the autonomous robot designs to avoid collisions with the

obstacles. The obstacle information is transmitted to a client PC using serial

communication and full control of the Rot to the user in the server PC.

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LIST OF TABLES

TABLE TITLE PAGE

NO. NO.

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LIST OF FIGURES

FIGURE TITLE PAGE

NO. NO.

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1. INTRODUCTION

In this project an obstacle sensing and object guiding Robot is

designed. Major problem in robot design is to detect an obstacle in front of it

to avoid collision. In this project, an electronic solution is attempted for this problem. We use a pair of ultrasonic sensor acting as an artificial eye for the

robot. The ultrasonic transmitter would transmit the ultrasonic wave from

the robot. Incase the robot meet an obstacle within the specific range from

the transmitter, the reflected waves are sensed by the ultrasonic receiver

which is placed at the close proximity of the transmitter. The system will

have an amplifier which would amplify this received signal and fire an

interrupt signal to the Embedded Microcontroller.

The Embedded microcontroller would then fire a warning alarm to

the robot enabling the user to take necessary diversion to avoid collision.

This project is of immense use in the autonomous robot designs to avoid

collisions with the obstacles. The obstacle information is transmitted to a

client PC using serial communication and full control of the Robot to the

user in the server PC. A pair of dc servo motor drives the robot towards the

target.

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1.1 BLOCK DIAGRAM:

Embedded

Processor

Reset

Hardware

Oscillator

Hardware

Power

PC

Interface

RS232

Ultrasonic

Transducer

Motor

Driver

Motor

1

Motor

2

NIC

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1.2 CIRCUIT DIAGRAM:

Fig 1.1 PROJECT SCHEMATIC DIAGRAM

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1.2. ULTRASONIC SENSOR

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2. HARDWARE DESCRIPTION

2.1 INTRODUCTION TO TARGET PROCESSOR

Microcontroller differs from a microprocessor in many ways. First

and the most important is its functionality. In order for a microprocessor to be

used, other components such as memory, or components for receiving and

sending data must be added to it. In short that microprocessor is the very heart

of the computer. On the other hand, microcontroller is designed to be all of that in one. No other external components are needed for its application

because all necessary peripherals are already built into it. Thus , we save

the time and space needed to construct devices .this chapter deals

with the study of microcontrollers.

2.2 DESCRIPTION TO EMBEDDED CONTROLLERS

Microcontroller, as the name suggests, are small controllers. These arelike single chip computers that are often embedded into systems to function as

processing /controllers unit. For example, the remote control you are using

probably has microcontrollers inside that do decoding and other controlling

functions. They are also used in automobiles, washing machines, microwave

ovens, toys…etc, where automation is needed. The key features of

microcontrollers include:

• High integration of Functionality

Microcontrollers sometimes are called single chip computers because they have on-chip memory and I/O circuitry and other

circuitries that enable them to function as small standalone

computers without other supporting circuitry.

• Field Programmability, Flexibility

Microcontrollers often use EEPROM or EPROM as their storage

device to allow field programmability so they are flexible to use. Once the

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program is tested to be correct then large quantities of microcontrollers can

be programmed to be used in embedded systems.

• Easy to Use

Assembly language is often used in microcontroller and since they

usually follow RISC architecture, the instruction set is small. The

development package of microcontrollers often includes an assembler ,a

simulator ,a programmer to “ burn “ the chip and a demonstration board

.Some packages include a high level language compiler such as a C

compiler and more sophisticated libraries.

2.2.1MEMORY UNIT

Memory is part of the microcontrollers whose function is to store

data. The easiest way to explain it is to describe it as one big closet with lots of

drawers. If we suppose that we marked the drawers in such a way that they can

not be confused, any of their contents will then be easily accessible. It is enoughto know the designation of the drawer and so its contents will be know to us for

sure.

Fig 2.2.1 Memory Unit of Microcontroller

Memory components are exactly like that. For a certain input we get the

contents of a certain addressed memory location and that’s all. Two new concepts

are brought to us: addressing and memory location. Memory consists of all

memory locations, and addressing is nothing but selecting one of them. This

means that we need to select the desired memory location on one hand, and on

the other hand we need to wait for the contents of that location. Besides reading

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from a memory location, memory must also provide for writing onto it. This is

done by supplying an additional line called control line. We will designate this

line as R/W (read/write). Control line used in the following way: if r/w=1,

reading is done, and if opposite is true then writing is done on the memory

location. Memory is the first element, and we need a few operation of our

microcontroller.

2.2.2 CENTRAL PROCESSING UNIT

Let add three memory locations to a specific block that will have a built in

capability to multiply, divide, subtract, and move its contents from one memory

location onto another. The part we just in is called “Central Processing Unit”

(CPU). Its memory locations are called registers.

Fig 2.2.2 Central Processing Unit of Microcontroller

Registers are therefore memory locations whose role is to help with

performing various mathematical operations or any other operations with datawherever data can be found. Look at the current situation. We have two

independent entities (memory and CPU) which are interconnected, and thus any

exchange of data is hindered, as well as its functionality. If, for example, we wish

to add the contents of two memory locations and return the result again back to

memory, we would need a connection between memory and CPU. Simply stated,

we must have some “way” though data goes from one block to another.

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2.2.3 INPUT-OUTPUT UNIT

Those locations we’ve just added are called “ports”. There are severaltypes of ports: Input, output or bidirectional ports. When working with ports, first

of all it is necessary to choose which port we need to work with, and then to send

data to, or take it from the port.

Fig 2.2.3 Input-Output Unit of Microcontroller

When working with it the port acts like a memory location. Something is

simply being written into or read from it, and it could be noticed on the pins of

the microcontroller.

2.2.4 Serial Communication:

Beside stated above we’ve added to the already existing unit the possibility

of communication with an outside world. However, this way of communicating

has drawbacks. One of the basic drawbacks is the number of lines which need to be used in order to transfer data. What if it is being transferred to a distance of

several kilometers? The number of lines time’s numbers of kilometers doesn’t

promise the economy of the project. It leaves us having to reduce the number of

lines in such a way that we don’t lessen its functionality. Suppose we are working

with three lines only, and that one line is used for sending data ,other for

receiving, and the third one is used as a reference line for both the input and

output side. In order for this to work, we need to set the rules of exchange of data.

These rules are called protocol. Protocol is therefore defined in advance so there

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wouldn’t be any misunderstanding between the sides that are communicating

with each other. The logical unit “1” is set up on the transmitting line until

transfer begins. Once the transfer starts, we lower the transmission line to logical

‘0” for a period of time (which we will designate as T), so the receiving side will

know that it is receiving data, and so it will activate its mechanism for reception.

Let’s go back now to the transmission side and start putting logic zeros and ones

the transmitter line in the order from a bit of the lowest value to a bit of the

highest value. Let each bit stay on line for a time period which is equal to T, and

in the end, or after the 8th bit. Let us bring the logical unit “1” back on the line

which will mark the end of the transmission of one data. The protocol we’ve just

described is called in professional literature NRZ (Non-Return to Zero).

Fig 2.2.4 Serial Communication

As we have separate lines for receiving and sending, it is possible to

receiving and sends data at the same time. So called full-duplex mode block

which enables this way of communication is called a serial communication block.

Unlike the parallel transmission, data moves here bit by bit, or in a series of bits

what defines the term serial communication comes from. After the reception of

data we need to read it from the receiving location and store it in memory as

opposed to sending where the process is reversed. Data goes from memory

through the buys to the sending location, and then to the receiving unit according

unit according to the protocol.

2.2.5 TIMER UNIT

Since we have the serial communication explained, we can receive, send

and Process data.

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Fig 2.2.5 Timer

However, in order to utilize it in industry we need a few additionally

blocks. One of those is the timer block which is significant to us because it can

give us information about time, duration, protocol etc. The basic unit of the timer

is a free-run counter which is in fact a register whose numeric value increments by one in even intervals, so that by taking its value during periods T1 and T2 and

on the basis of their difference we can determine how much time has elapsed.

This is a very important part of the microcontroller whose understanding requires

most of our time.

2.2.6 FEATURES OF AT89C52 MICROCONTROLLER (TARGET

PROCESSOR)

AT89C52 is a slightly more powerful microcontroller which provides highly

flexible and cost effective solutions to many embedded control applications.

Following are the features.

1. It has 256 bytes of internal RAM compared to 128 in the standard

8051.

2. It is low power; high performance CMOS 8-bit microcomputers with

8K bytes of flash programmable and erasable read only memory

(PEROM).

3. Fully static operation: 0 Hz to 24 MHz.4. It has 32 programmable I/O lines i.e. it has 4 ports (port0 to port3)

with 8 lines each.

5. A third 16-bit Timer/counter is present inside this microcontroller to

strengthen its operation, compared to only 2 timers in standard 8051.

6. It has eight interrupt sources.

7. One more additional feature of AT89C52 is that it has 26 special

function registers, 5 more than the standard 8051.

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8. The device is manufactured using ATMEL’s high-density non volatile

memory technology and is compatible with the industry-standard

80C51 and 80C52 instruction set and pin out.

2.2.7 DESCRIPTION

The AT89C52 is a low-power, high-performance CMOS 8-bit

microcomputer with 8K bytes of Flash programmable and erasable

read only memory (PEROM). The device is manufactured using

Atmel’s high-density nonvolatile memory technology and is

compatible with the industry-standard 80C51 and 80C52 instruction

set and pin out. 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 flash on a

monolithic chip, the Atmel AT89C52 is a powerful microcomputer

which provides a highly-flexible and cost-effective solution to manyembedded control applications.

The AT89C52 provides the following standard features: 8K

bytes of flash, 256 bytes of RAM, 32 I/O lines three 16-bit

timer/counters, a six-vector two level interrupt architecture, a full

serial-duplex serial port, on-chip oscillator, and clock circuitry. In

addition, the AT89C52 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 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

hardware reset.

2.2.8 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 addressesmay 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.

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Timer 2 Registers : The individual interrupt enable bits are in the IE

register. Two priorities can be set for each of the six interrupt sources in the

IP register.

DATA MEMORY

The AT89C52 implements 256 bytes of on-chip RAM. The upper 128 bytes

occupy a parallel address space to the Special Function Registers. That

means the upper 128 bytes have the same addresses as the SFR space but are

physically separate from SFR space.

When an instruction accesses an internal location above address 7FH, the

address mode used in the instruction specifies whether the CPU accesses the

upper 128 bytes of RAM or the SFR space. Instructions that use direct

addressing access SFR space.

For example, the following direct addressing instruction accesses the SFR at

location 0A0H (which is P2).

Instructions that use indirect addressing access the upper 128 bytes of RAM.For example, the following indirect addressing instruction, where R0

contains 0A0H, accesses the data byte at address 0A0H, rather than P2

(whose address is 0A0H).

MOV @R0, #data

Note that stack operations are examples of indirect addressing, so the upper

128 bytes of data RAM are available as stack space.

TIMER 0 AND 1

Timer 0 and timer 1 in the AT89C52 operate the same way as timer 0 and

timer 1 in the AT89C51.

TIMER 2

Timer 2 is a 16-bit Timer/counter that can operate as either a timer or an

event counter. The type of operation is selected by bit C/T2 in the SFR

T2CON (shown in table 2).

Timer 2 has three operating modes: capture, auto-reload (up or down

counting), and baud rate generator. The modes are selected by bits in

T2CON, as shown in Table 3.

Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function,

the Tl2 register is incremented every later periods, the count rate is 1/12 of

the oscillator frequency.In the counter function, the register is incremented in response to a 1-to-0

transition at its corresponding external input pin, T2. In this function, the

external input is sampled during S5P2 of every machine cycle. When the

samples show a high in one cycle and a low in the next cycle, the count is

incremented. The new count value appears in the register during S3P1 of the

cycle following the one in which the transition was detected. Since two

machine cycles (24 oscillator periods) are required to recognize a 1-to-0

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transition, the maximum count rate is 1/24 of the oscillator frequency. To

ensure that a given level should be held for at least one full machine cycle.

CAPTURE MODE

In the capture mode, two options are selected by bit EXEN2 in T2CON. If

EXEN2 = 0, timer 2 is a 16 bit-timer or counter which upon overflow sets

bit TF2 in T2CON. This bit can then be used to generate an interrupt. If

EXEN2 = 1, timer 2 performs the same operation, but a 1-to-0 transition at

external input T2EX also causes the current value in TH2 and TL2 to be

captured into RCAP2H and RCAP2L, respectively. In addition, the

transition at T2EX causes bit EXF2 in T2CON to be set. The EXF2 bit, like

TF@, can generate an interrupt. The capture mode is illustrated in figure 1.

AUTO-RELOAD (UP OR DOWN COUNTER)

Timer 2 can be programmed to count up or down when configured in its 16- bit auto-reload mode. This feature is invoked by the DCEN (Down Counter

Enable) bit located in the SFR T2MOD (see table 4). Upon reset, the DCEN

bit is set to 0 so that timer 2 will default to count up. When DCEN is set,

timer 2 can count up or down, depending on the value of the T2EX pin.

Figure 2 shows timer 2 automatically counting up when DCEN = 0. In this

mode, two options are selected by bit EXEN2 in T2CON. If EXEN2 = 0,

timer 2 counts up to 0FFFFH and then sets the TF2 bit upon overflow. The

overflow also causes the timer registers to be reloaded with the 16-bit value

in RCAP2H and RCAP2L. The values in timer in capture Mode RCAP2H

and RCAP2L are preset by software. If EXEN2 = 1, a 16-bit reload can be

triggered either by an overflow or by a 1-to-0 transition at external input

T2EX. This transition also sets the EXF2 bit. Both the TF2 and EXF2 bits

can generate an interrupt if enabled.

Setting the DCEN bit enables timer 2 to count up or down, as shown in

Figure 3. In this mode, the T2EX pin controls the direction of the count.

Logic 1 at T2EX makes timer2 count up. The timer will overflow at

0FFFFH.

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3. MICROCONTROLLER INTERFACING

3.1 DC MOTOR

3.1.1Introduction

Whenever a robotics hobbyist talk about making a robot, the

first thing comes to his mind is making the robot move on the ground. And

there are always two options in front of the designer whether to use a DC

motor or a stepper motor. When it comes to speed, weight, size, cost... DC

motors are always preferred over stepper motors. There are many things

which you can do with your DC motor when interfaced with a

microcontroller. For example you can control the speed of motor, you can

control the direction of rotation, you can also do encoding of the rotation

made by DC motor i.e. keeping track of how many turns are made by your motors etc. So you can see DC motors are no less than a stepper motor.

In this part of tutorial we will learn to interfacing a DC motor

with a microcontroller. Usually H-bridge is preferred way of interfacing a

DC motor. These days many IC manufacturers have H-bridge motor drivers

available in the market like L293D is most used H-Bridge driver IC. H-

bridge can also be made with the help of transistors and MOSFETs etc.

rather of being cheap, they only increase the size of the design board, which

is sometimes not required so using a small 16 pin IC is preferred for this purpose.

3.1.2 Theory of DC motor speed control

The speed of a DC motor is directly proportional to the supply

voltage. If the voltage is brought lower than the lower limit, the motor will

not operate at all and the voltage should not be increased beyond the upper

limit for the safe operation of the motor. The lower limit is the minimum

voltage that the motor requires for its operation and the upper limit is the

maximum voltage (i.e.) the rated voltage of the motor.

The speed controller works by varying the average voltage sent to the

motor. It could do this by simply adjusting the voltage sent to the motor, but

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http://www.8051projects.net/dc-motor-interfacing/introduction.php








this is quite inefficient to do. A better way is to switch the motor's supply on

and off very quickly. If the switching is fast enough, the motor doesn't notice

it, it only notices the average effect.

Now imagine a light bulb with a switch. When the switch is closed,

the bulb goes on and is at full brightness, say 100 Watts. When the switch is

opened it goes off (0 Watts). Now the switch is closed for a fraction of a

second, then is opened for the same amount of time, the filament won't have

time to cool down and heat up, and you will just get an average glow of 50

Watts. This is how lamp dimmers work and the same principle is used by

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

24 Volts, and when it is open it sees 0 Volts. If the switch is open for the

same amount of time as it is closed, the motor will see an average of 12

Volts, and will run more slowly accordingly.

As the time for which the voltage is on increases compared to the time for

which it is off , the average speed of the motor increases.

This on-off switching is performed by a technique called PULSE WIDTH

MODULATION.

The time that it takes a motor to speed up and slow down under switching

conditions is dependant on the inertia of the rotor (basically how heavy it is),

and how much friction and load torque there is. The graph below shows the

speed of a motor that is being turned on and off fairly slowly:

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FIG.4.2 VARIATION OF MOTOR SPEED AND SUPPLY VOLTAGE

WITH TIME

It is seen that the average speed is around 150, although it varies quite

a bit. If the supply voltage is switched fast enough, it won’t have time to

change speed much, and the speed will be quite steady. This is the principleof switch mode speed control. Thus the speed is set by PWM – Pulse Width

Modulation.

3.1.3 SPEED SENSING MECHANISM

This motor uses an optointerrupter as a rotor position sensor. The

optointerrupter is an electronic device that consists of a light emitting diode

(LED) and a phototransistor with a slot between them.

When voltage is applied to the LED it emits light like an electric bulb.

However, the LED used in an optointerrupter emits an infrared light beam,

which is invisible. Light emitting diodes are very reliable and consume a

relatively small current. Big current may destroy them, therefore a resistor

23



must be added to limit the current. Optointerrupters supplied with the kit (or

sold as a separate part) come with a 270 Ohm resistor which is suitable for

voltages in the range from 3 to 6V.

Phototransistors are specially designed transistors with the base

region exposed. These transistors are light sensitive, especially when

infrared source of light is used. They have only two leads (collector and

emitter). When there is no light the phototransistor is closed and does not

allow a collector-emitter current to go through. The phototransistor opens

only with the presence of sufficient light.

The picture below shows an optointerrupter.

FIG.4.10 OPTOINTERRUPTER

The motor with optical control uses a flat opaque disk with

four blades attached to the rotor. When rotor spins the blades cross the slot

and interfere with the beam from the LED to the phototransistor. The width

of the blade greatly affects the efficiency of the motor as it determines how

long the electromagnet stays on. The disk is shown below. The blades are

quite narrow so it consumes less current. With this width the motor may notstart at 3V, but it works much longer in the range 4.5-6V.

24



FIG.4.11 FOUR TOOTH ENCODER

The output from the phototransistor is very small and needs to be amplified.

To make this motor as simple as possible and minimize the number of parts,

a Darlington transistor was used.

This is how this motor works:

1. In the starting position, the disk blade interferes with the channel

between the LED and the Phototransistor.

FIG.4.12 MOTOR DISC: POSITION1

2. The disk moves out of the slot between the LED and phototransistor.

The light signal to the phototransistor turns it on, and the

phototransistor current turns the transistor off.

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3. Due to inertia, the next blade of the disk moves back into the slot. The

phototransistor closes. This process continues until the power is

disconnected.


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3.1.4 SPEED ENCODERS

To start with, we need a device that will measure the speed of the

motor shaft. The best way to do this is to fit an optical encoder. This shines a

beam of light from a transmitter across a small space and detects it with a

receiver the other end. If a disc is placed in the space, which has slots cut

into it, then the signal will only be picked up when a slot is between the

transmitter and receiver. An example of a disc is shown below

FIG.4.15 SPEED ENCODER

The encoder transmitter must be supplied with a suitable current, and the

receiver biased as below:

FIG.4.16 OPTO INTERRUPTER CIRCUITRY

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This will have an output, which swings to +5v when the light is blocked, and

about 0.5 volts when light is allowed to pass through the slots in the disc.

These voltages are compatible with normal digital circuitry.

3.1.5 Working Theory of H-Bridge

The name "H-Bridge" is derived from the actual shape of

the switching circuit which controls the motion of the motor. It is also

known as "Full Bridge". Basically there are four switching elements in the

H-Bridge as shown in the figure below.

As you can see in the figure above there are four switching

elements named as "High side left", "High side right", "Low side right",

"Low side left". When these switches are turned on in pairs motor changesits direction accordingly. Like, if we switch on High side left and Low side

right then motor rotate in forward direction, as current flows from Power

supply through the motor coil goes to ground via switch low side right. This

is shown in the figure below.

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Similarly, when you switch on low side left and high side

right, the current flows in opposite direction and motor rotates in backward

direction. This is the basic working of H-Bridge. We can also make a small

truth table according to the switching of H-Bridge explained above.

Truth Table

High Left High Right Low Left Low Right Description

On Off Off On Motor runs clockwise

Off On On Off Motor runs anti-clockwise

On On Off Off Motor stops or decelerates

Off Off On On Motor stops or decelerates

As already said, H-bridge can be made with the help of

transistors as well as MOSFETs; the only thing is the power handling

capacity of the circuit. If motors are needed to run with high current then lot

of dissipation is there. So head sinks are needed to cool the circuit.

So we have seen that using simple switching elements we can

make our own H-Bridge, or other option we have is using an IC based H-

bridge driver. Both of them are discussed in the next section of the tutorial.

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3.1.6 L293D Dual H-Bridge Motor Driver

L293D is a dual H-Bridge motor driver , So with one IC we can

interface two DC motors which can be controlled in both clockwise and

counter clockwise direction and if you have motor with fix direction of

motion the you can make use of all the four I/Os to connect up to four DC

motors. L293D has output current of 600mA and peak output current of 1.2A per channel. Moreover for protection of circuit from back EMF ouput

diodes are included within the IC. The output supply (VCC2) has a wide

range from 4.5V to 36V, which has made L293D a best choice for DC motor

driver.A simple schematic for interfacing a DC motor using L293D is shown

below.

As you can see in the circuit, three pins are needed for interfacing a DC

motor (A, B, Enable). If you want the o/p to be enabled completely then you

can connect Enable to VCC and only 2 pins needed from controller to make

the motor work.

30

http://www.8051projects.net/dc-motor-interfacing/l293d-interfacing-with-microcontroller.php






3.2 RS232 SERIAL CONNECTOR PIN ASSIGNMENT:

The RS232 connector was originally developed to use 25 pins. In this DB25

connector pinout provisions were made for a secondary serial RS232

communication channel. In practice, only one serial communication channel

with accompanying handshaking is present. Only very few computers have

been manufactured where both serial RS232 channels are implemented. Also

on a number of Telebit modem models the secondary channel is present. It

can be used to query the modem status while the modem is on-line and busy

communicating. On personal computers, the smaller DB9 version is more

commonly used today. The diagrams show the signals common to both

connector types in black. The defined pins only present on the larger

connector are shown in red. Note, that the protective ground is assigned to a

pin at the large connector where the connector outside is used for that

purpose with the DB9 connector version.

RS232 DB9 pinout

The pinout is also shown for the DEC modified modular jack. This type of

connector has been used on systems built by Digital Equipment Corporation;

in the early day’s one of the leaders in the mainframe world. Although this

serial interface is differential (the receive and transmit have their own

floating ground level which is not the case with regular RS232) it is possible

to connect RS232 compatible devices with this interface because the voltage

31



levels of the bit streams are in the same range. Where the definition of

RS232 focused on the connection of DTE, data terminal equipment

(computers, printers, etc.) with DCE, data communication equipment

(modems), MMJ was primarily defined for the connection of two DTE's

directly.

32



Ultrasonic Distance Sensor

Its compact size, higher range and easy usability make it a

handy sensor for distance measurement and mapping. The robot requires

means of detecting an obstacle (or another robot) without making physical

contact. This allows the robot to decide whether to avoid or to confront and

investigate the obstacle depending on its programming. Ultrasonic

transducers were chosen for this because they are more reliable and have a

greater range than IR sensors (effectiveness of IR sensors varies with

ambient light level).

3.2.1 Features

• Minimum range 10 centimeters

• Maximum range 400 centimeters (4 Meters)

• Accuracy of +-1 cm

• Resolution 0.1 cm

• 5V DC Supply voltage

• Compact sized SMD design

• Modulated at 40 kHz

• Serial data of 9600 bps TTL level output for easy interface with any

microcontroller

Specification:

Description Signal9-pin

DTE

25-pin

DCESource DTE or DCE

Carrier Detect CD 1 8 from Modem

Receive Data RD 2 3 from Modem

Transmit Data TD 3 2 from Terminal/Computer Data Terminal

ReadyDTR 4 20 from Terminal/Computer

Signal Ground SG 5 7 from Modem

Data Set Ready DSR 6 6 from Modem

Request to Send RTS 7 4 from Terminal/Computer

Clear to Send CTS 8 5 from Modem

Ring Indicator RI 9 22 from Modem

33



Supply Voltage 5 V

Supply Current 15 mA

Output Data speed 9600 Bps

Output Data Format 8-N-1 8 data bytes, no parity, 1 stop bit

3.2.2 Pin Details:

1 – GND Supply Ground

2 - +5V Supply +5V

3 – Serial Out 9600 Serial output data (TTL 5V level) at 9600 baud rate

The IC U1 is a 555 timer in astable configuration to oscillate at 40 KHz.

Instead of using exact values for the two resistors that is placed between pin

6 and 7, a 10K ohm potentiometer (VR1) was used. This also allows for some fine tuning of the output frequency. The output (pin 3) is then attached

to a 40 KHz ultrasonic transmitter (UTR1).

The receiving circuit is a dual LM358N (U2) op-amp. A ultrasonic receiver

(UTR2) is connected to pin 3, the non-inverting input of U2a which is a non-

inverting amplifier with a gain of 220. The output of U2a is put through a

low pass filter via D1, C3 and R4 to produce a some what stable DC voltage.

This DC voltage is fed into the non-inverting input of U2b configured as a

non-inverting comparator. Sensitivity of U2b is controlled by VR2 to set the

threshold trigger value. The output of U2b is connected through R5 to the base of a bipolar 2N2222 transistor (Q1) acting as an inverter with a LED

(LED1) to indicate if an obstacle has been detected. Finally, the collector of

Q1 goes to the Handy Board's digital port (Handy Board uses inverted logic

levels, 0V is a logic 1 and +5V is a logic 0).

The following is the procedure to calibrate the circuit without the use of an

oscilloscope:

1) Adjust VR1 till the value between Vcc and pin 7 is approximately 1.2K

ohm.

2) Place UTR1 and UTR2 parallel to each other (about 1.5 inches apart) with

a solid object about 6 inches in front of them (similar to figures UTR1 and

UTR2 in the above schematic).

3) If LED1 is off, turn VR2 CW till LED1 is on and then back off a bit till it

is just off. If LED1 is on, turn VR2 CCW till LED1 is just off.

4) Adjust VR1 (should only be about 1/4 turn CW or CCW) till LED1 turns

34



on.

5) Repeat steps 3) and 4) as needed for optimal distance and sensitivities.

This circuit should be able to detect an object about the size of a text book at

a distance of almost 2 meters.

The above circuit board contains 4 obstacle detection circuits.One 555 timer was used to drive the 4 ultrasonic transmitters, and one

LM358N were used per ultrasonic receiver. Due to limited space on the

board, a transistor array containing four 2N2222 bipolar transistors were

used. The 4X3 female header are used to attache the ultrasonic Tx/Rx pair

and the 4X3 male header plugs directly into digital ports 12-15 on the Handy

Board.

Selection and use of Ultrasonic Ceramic Transducers:

The purpose of this application note is to aid the user in the

selection and application of the Ultrasonic ceramic transducers. The general

transducer design features a piezo ceramic disc bender that is resonant at a

nominal frequency of 20 – 60 KHz and radiates or receives ultrasonic

energy. They are distinguished from the piezo ceramic audio transducer in

that they produce sound waves above 20 KHz that are inaudible to humans

and the ultrasonic energy is radiated or received in a relatively narrow beam.The “open” type ultrasonic transducer design exposes the piezo bender

bonded with a metal conical cone behind a protective screen. The “enclosed”

type transducer design has the piezo bender mounted directly on the

underside of the top of the case which is then machined to resonant at the

desired frequency. The “PT and EP” type transducer has more internal

damper for minimizing “ringing”, which usually operates as a transceiver –

oscillating in a short period and then switching to receiving mode.

3.2.3 Comparative CharacteristicsWhen compared to the enclosed transducer, the open type receiver will

develop more electrical output at a given sound pressure level (high

sensitivity) and exhibit less reduction in output as the operating frequency

deviates from normal resonant frequency (greater bandwidth). The open type

transmitter will produce more output for a specific drive level (more

efficient). The enclosed type transducer is designed for very dusty or

outdoor applications. The face of the transducer must be kept clean and free

of damage to prevent losses. The transmitter is designed to have low

35



impedance at the resonant frequency to obtain high mechanical efficiency.

The receiver is constructed to maximize the impedance at the specified anti-

resonant frequency to provide high electrical efficiency.

3.2.4 Transmitter Drive Considerations

The ultrasonic transmitters can dissipate 200 mw rms continually.

Assuming a typical minimum series impedance of 500 ohms, the driver must

source 20 mA at 10 V rms.

A sine wave drive should be used to minimize harmonics that may

excite the transducer in an overtone mode (vibrate at a multiple of the

resonant frequency). For most models the maximum amplitude of the drive

waveform should be limited to 50 V pp. The transmitter dissipation must be

limited to an effective or average level of 200 mW by reducing the duty

cycle when the transmitter is dissipating more than 200 mW.

There are several oscillator circuits suitable for driving our ultrasonictransmitter, which have been widely used on security systems, remote

control and other applications. Please bear in mind that the circuits we

suggest sometimes need to be modified according to the different characters

of impedance, phase angle and resonant frequency while driving different

type of transmitters. Please refer to “Impedance Characteristics” carefully.

Suggestion Oscillating Circuits:

36



The ultrasonic transmitters may also be driven with a pulse waveform.

Application of a DC Pulse of 10 – 20 volts will cause the transducer to

“ring” at the selected resonant frequency. The ultrasonic output will be a

damped ringing waveform as illustrated in the figure as follow.

Impedance Characteristic

Ultrasonic transmitter impedance characteristics vary with operating

frequency and temperature in complex manner that is different for each

oconstruction.

In general, for frequencies approximately 0.1 octave on either side of the

resonant frequency, the transmitter looks like a capacitor. The current

37



through the transmitter will lead the voltage developed across the transmitter

by 90 degrees.

As the resonant frequency is approached, the voltage drop across the

transmitter will decrease to a minimum at the resonant frequency (minimum

series impedance) and the current will increase proportionally. The phase

lead to this current relative to the voltage will decrease to zero near the

resonant frequency and the transmitter will then appear to be a pure

resistance. As the frequency is increased above the resonant point, the

current may now lag the voltage by an increasing amount (maximum of 90

degrees) as the voltage across the transmitter climbs to a peak which is

defined as the anti-resonant frequency. During this transition, the transmitter

appears to have an inductive characteristic.Increasing temperature will lower

the resonant frequency and thus the point at which the phase changes will

occur.

The test circuit shown as below may be used to measure the resonant, anti-

resonant frequencies and impedance characteristics of our piezo ceramictype ultrasonic transducers.

Adjust input frequency to obtain maximum Vout, Switch in

variable resistor and adjust to obtain same voltage output. The value of

variable resistor now equals to the minimum series impedance. Adjust

frequency to obtain minimum Vout. Switch in variable resistor and adjust to

obtain same voltage output. The value of variable resistor now equals to the

maximum series impedance at the anti-resonant frequency. The resistor

values of voltage divider, 100 and 10 ohms, probably need to be modifiedfor better Vout resolution while measuring anti-resonant impedance.

3.2.5 Ultrasonic Echo Ranging

Ultrasonic ranging systems are used to determine the distance to an object

by measuring the time required for an ultrasonic wave to travel to the object

and return to the source. This technique is frequently referred to as “echo

ranging”. The distance to the object may be related to the time it will take

38



for an ultrasonic pulse to propagate the distance to the object and return to

the source by dividing the total distance by the speed of sound which is 344

meters/second or 13.54 inches/millisecond. Below is a block diagram that

illustrates the basic design concept and functional elements in a typical

ranging system.

The driving signal can be either a tone burst of suitable burst number, whichdepends on the rising time of transceiver, or a pulse that will result in the

transmission of a few cycles of ultrasonic energy. MCU starts a counter

when tone burst starting, which is stopped by the detected returning echo.

The count is thus directly proportional to the propagation time of the

ultrasonic wave.

The matching circuit tunes out the imaginary part of transceiver

and also plays as a impedance matching bridge for maximizing energy

transfer. The returning ultrasonic echo is usually very weak and the key to

designing a good ranging system is to utilize a high “Q” tuned frequencyamplifier stage that will significantly amplify any signal at the frequency of

the ultrasonic echo while rejecting all other higher or lower frequencies.

Another useful technique is to make the gain of the echo amplifier increase

with time such that the amplifier gain compensates for the proportional

decrease in the signal strength with distance or time. This amplifier is called

as TGC (Time Controlled Gain) Amplifier.

39



4. DESCRIPTION OF DEVELOPMENT SYSTEM

4.1 CROSS COMPILERS

First of all we begin this chapter by giving a brief introduction about

cross compilers in embedded programming and their applications. We know

that the execution of code in a microcontroller takes place as a hexadecimal

code. So we can program any microcontroller using an assembly language.

Also though the use of cross compilers we can program the microcontrollers

in any language like ‘C’ or ‘C++.

The cross compilers acts as a bridge between the programming

software and microcontrollers. Suppose we are programming the

microcontroller using ‘C’ the code written in ‘C’ language cannot be directly

executed by microcontroller. So this code written in ‘C’ is fed to a cross

compiler which converts into hexadecimal code which is understood and

executed by microcontroller. The advantages of using cross compilers is that

in case of some applications programming the microcontroller using

40



assembly language will become bulk and tedious. So when we use cross

compilers we can program the microcontroller in any other language which

is easy to program and debug also. The commonly used cross compilers are

SDCC (Small devices C compiler), Keil etc.

In this our project the use of Keil cross compiler is to program the

microcontroller. In this chapter we discuss the introduction to programming

in Keil features of Keil and finally advantages of using Keil when compared

to other cross compilers. When we are writing program for any

microcontroller using cross compiler we cannot directly write the converted

code on to the microcontroller. This means we need to use a special

technique to load the program into the microcontroller. One of the methods

is to use a microcontroller with a flash memory. Flash memory is similar to

erasable programmable read only memory. So once program is written and

debugged using cross compiler, we need to flash the program on to the flash

memory of the memory. Once program is flashed the microcontroller is

loaded with the hex code and it will be ready for execution.

4.1.1 INTRODUCTION TO KEIL:

Keil software provides the premier 8051 development tools to

industry .The keil software comprises of different tool kits. A tool kit consist

of several application program that we can use to create our 8051 application

.When we use keil software for our project the development cycle is some

what similar to a software development project .It consist of creating source

file in C or assembly language compiling or assembling the source files

debugging error in the source file, linking file from complier and assembler

and finally building a project linking all the files and testing the linked

application.

41



4.1.2 FUNCTIONING OF KEIL

All the files are created through the micro vision integrated

development environment are then passed to the C51 compiler or A51

assembler. The compiler and assembler process source files and create

relocatable object files. Object files created by the compiler or assembler

may be used by the library manager to create a library. A library is a

specially formatted, ordered program collection of object modules that linker

can process. When the linker processes a library, only the object modules in

the library necessary for program creation are used. Object files created by

the compiler and assembler and library files created by the library manager

are processed by the linker to create an absolute object module. An absolute

object file or module is an object file with no relocatable code. All the code

in an absolute object file resides at fixed locations.

The absolute object file created by the linker may be used to

program EPROM or other memory devices. The absolute object module may

also be used with the dScope-51 debugger / simulator or with an in-circuit

emulator. The dScope-51 source level debugger/simulator is ideally suited

for fast, reliable high-level-language program debugging. The debugger

contains a high-speed simulator and a target debugger that let you simulate

an entire 8051 system including on-chip peripherals. By loading specific I/O

drivers, we can simulate the attributes and peripherals of a variety of 8051

family. The RTX-51 real time operating system is a multitasking kernel for

the 8051 family. The RTX-51 real time kernel simplifies the system design,

programming, and debugging of complex applications where fast reaction to

time critical events is essential. The kernel is fully integrated into the

C51compiler and is easy to use. Task description tables and operating

42



system consistency are automatically controlled by the BL51 code banking

linker/locater.

4.1.3 DEVELOPMENT TOOLS IN KEIL

The Fig 4.1 shows the full extent of the Keil Software 8051

development tools. The tools listed in this diagram comprise the professional

developer’s kit. In addition to the professional kit, Keil Software provides a

number of other tool kits for the 8051 developer. The most capable kit is the

professional developer’s kit is described as follows:

The professional developer’s kit includes everything the professional

8051 developer needs to create sophisticated embedded applications. This

tool kit includes the following components:

• C51 Optimizing C compiler,

•

A51 Macro Assembler,• BL51 Code Banking Linker/Locator,

• OC51 Banked Object file converter,

• OH51 Object-Hex converter,

• LIB51 Library Manager,

• dScope-1 Simulator/debugger,

•tScope-51 Target Debugger,

• Monitor-51 ROM Monitor and Terminal Program,

• Integrated Development Environment,

• RTX-51 Tiny Real-Time Operating System.

43



In addition, the professional developer’s kit includes the following tools for

Windows users:

• dScope-51 Simulator/Debugger for windows,

• Micro Vision/51 Integrated Development Environment for

windows.

The professional developer’s kit can be configured for all 8051 derivatives.

The tools included in this kit can run any compatible computer.

4.1.4 C51 OPTIMIZING C CROSS COMPILER

The C programming language is a general-purpose programming

language that provides code efficiency, elements of structured programming,

and a rich set of operators. Its generality, combined with its absence of restrictions, make C a convenient and effective programming solution for a

wide variety of software tasks. Many applications can be solved more easily

and effectively with C than with other more specialized languages. The Keil

software C51 optimizing cross compiler for the MS-DOS operating system

is a complete implementation of the ANSI (American National Standards

Institute) standard for the C language. The C51 compiler generates code for

the 8051 microprocessor but is not a universal C compiler adapted for the

8051 target. It is a ground-up implementation dedicated to generating

extremely fast and compact code for the 8051 microprocessor. For most

8051 applications, the C51 compiler gives software developers the flexibility

of programming in /c while matching the code efficiency and speed of

44



assembly language. Using a high-level language like C has many advantages

over assembly language programming. For example:

Knowledge of the processor instruction set is not required. A

rudimentary knowledge of the 8051’s memory architecture is

desirable but not necessary.

Register allocation and addressing mode details are managed by the

compiler.

The ability to combine variable selection with specific operations

improves program readability.

Keywords and operational functions that more nearly resemble the

human thought process can be used.

Program development and debugging times are dramatically reduced

when compared to assembly language programming.

The library files that are supplied provide many standard routines

(such as formatted output, data conversions, and floating-point

arithmetic) that may be incorporated into our application.

Existing routine can be reused in new programs by utilizing modular

programming techniques available with C.

The C language is very portable and very popular. C compilers are

available for almost all target systems. Existing software investments

can be quickly and easily converted from or adapted to other

processors or environments.

4.1.5 A51 MACRO ASSEMBLER

The A51 assembler is a macro assembler for the 8051 microcontroller

family. It translates symbolic assembly language mnemonics into relocatable

45



object code where the utmost speed, small code size, and hardware control

are critical. The macro facility speeds development and conserves

maintenance time since common sequences need only be developed once.

The A51 assembler supports symbolic access to all features of the 8051

architecture and is configurable for the numerous 8051 derivatives. The A51

assembler translates an assembler source file into a relocatable object

module. If the DEBUG control is used, the object file contains full symbolic

information for debugging with dScope or an in-circuit emulator. In addition

to the object file, the A51 assembler generates a list file which may

optionally include symbol table and cross reference information. The A51

assembler is fully compatible with Intel ASM-51 source modules. The A51

assembler supports all members of the 8051 family. The special function

register (SFR) set of the 8051 is predefined. However, the NOMOD51

control lets you override these definitions with processor-specific include

files. The A51 assembler is shipped with include files for the 8051, 8051fx,

8051GB, 8052, 80152, 80451, 80452, 80515, 80C517, 80C517A, 8x552,

8xC592, 8xCL782, 8xCL410 and 80C320 microcontrollers. You can easily

create include files for other 8051 family members.

4.1.6 BL51 CODE BANKING LINKER/LOCATOR

The 51 code banking linker /locator combines one or more object

modules into a single executable 8051 program. The linker also resolves

external and public references, and assigns absolute addresses to relocatable

programs segments. The BL51 code banking linker/locator processes object

modules created by the keil C51 compiler and A51 assembler and the Intel

PL/M-51 compiler and ASM-51 assembler. The linker automatically selects

the appropriate run-time library and links only the library modules that are

46



required. Normally, you invoke the BL51 code banking linker/locator from

the command line specifying the names of the object modules to combine.

The default controls for the BL51 code banking linker/locator have been

carefully chosen to accommodate most applications without the need to

specify additional directives. However, it is easy for us to specify custom

settings for your applications.

4.1.7 OC51 BANKED OBJECT FILE CONVERTER

The OC51 banked object file converter creates absolute object

modules for each code bank in a banked object module. Banked object

modules are created by the BL51 code banking linker/locator when you

create a bank switching application. Symbolic debugging information is

copied to the absolute object files and can be used by dScope or an in-circuit

emulator. We may use the OC51 banked object file converter to create

absolute object modules for the command area and for each code bank in

your banked object module. You may then generate Intel HEX files for each

of the absolute object modules using the OH51 object-hex converter.

4.1.8 OH51 OBJECT-HEX CONVETER

The OH51 object-hex converter creates Intel hex files from absolute

object modules. Absolute object modules can be created by the BL51 code

baking linker or by the OC51 banked object file converter. Intel hex files are

ASCII files that contain a hexadecimal representation of your application.

They can be easily loaded into a device programmer for writing on Erasable

programmable read only memory.

47



LIB51 LIBRARY MANAGER

The LIB51 library manager lets you create and maintain library files.

A library file is a formatted collection of one or more object files. Library

files provide a convenient method of combining and referencing a large

number of object files. Libraries can be effectively used by the BL51 code

banking linker/locator. The LIB51 library manager lets you create a library

file, add object modules to a library file, remove object modules from may

be controlled interactively or from the command line.

DSCOPE-51 FOR WINDOWS

DScope-51 is a source level debugger and simulator for programs

created with the keil C51 compiler and A51 assembler and the Intel PL/M-

51 compiler and ASM-51 assembler. DScope-51 is a software-only product

that lets us simulate the features of an 8051 without actually having target

hardware. We may have used Scope-51 to test and debug our embedded

applications before actual 8051 hardware is ready. DScope-51 simulates a

wide variety of 8051 peripherals including the internal serial port, external

I/O, and timers.

4.1.9 µVISION/51 FOR WINDOWS

Microvision/51 is an integrated software development platform that

includes a full function editor, project manager, make facility, and

environment control for the keil 8051 tools. When we use µVision/51 speeds

our embedded applications development by providing the following:

48



Standard Windows user interface,

Dialog boxes for all environment and development tool

settings,

Multiple file editing capability,

Full function editor with user-definable key sequences,

Application manager for adding external programs into the

pull-down menu,

Project manager for creating and maintaining projects,

Integrated make facility for building target programs from your

projects,

On-line help system.

4.2 TARGET PROCESSOR

In our project microcontroller AT89C52 (Target processor) is used to

governs all the essential process which has to be executed during

acquisition.Microcontroller, as the name suggests, are small controllers. These are like single

chip computers that are often embedded into systems to function as processing

/controllers unit. For example, the remote control you are using probably has

microcontrollers inside that do decoding and other controlling functions. They are

also used in automobiles, washing machines, microwave ovens, toys…etc, where

automation is needed. The key features of microcontrollers include:

• High integration of Functionality

Microcontrollers sometimes are called single chip computers because they

have on-chip memory and I/O circuitry and other circuitries that enable

49



them to function as small standalone computers without other supporting

circuitry.

• Field Programmability, Flexibility

Microcontrollers often use EEPROM or EPROM as their storage device to

allow field programmability so they are flexible to use. Once the program

is tested to be correct then large quantities of microcontrollers can be

programmed to be used in embedded systems.

• Easy to Use

Assembly language is often used in microcontroller and since they usually

follow RISC architecture, the instruction set is small. The development

package of microcontrollers often includes an assembler ,a simulator ,a

programmer to “ burn “ the chip and a demonstration board .Some

packages include a high level language compiler such as a C compiler and

more sophisticated libraries.

5. APPLICATION SOFTWARE

5.1 APPLICATION SOFTWARE DISCRIPTION

The application software is a virtual representation of the actual

instrument and provides all facilities for the user to control the working of

the motor. This technique of operating the motor (the actual instrument) is

highly advantageous, as it does not permit the actual instrument to be

misused, for example, here, the minimum and maximum speed of the motor

is defined and hence prevents the user from exceeding the speed limits. Thus

the application software provides high security to the actual instrument.

Moreover certain graphical representation of the real time values with high

resolution can also be implemented.

This software facilitates the user to turn on/off the motor, speed

control and direction control of the motor. When the ON/OFF buttons are

50



pressed, two unique values corresponding to the on/off states are transmitted

serially, which is identified by the microcontroller. A slider allows the user

to set the speed of the motor. The actual speed of the motor is sensed by the

opto-interrupter and is transmitted serially to the application through suitable

signal conditioning circuitry. Thus the application software is continuously

updated with the current speed of the motor. Simultaneously a real time

graph of the actual speed of the motor is plotted. Also there is virtual

representation of the motor shaft, which rotates corresponding to the speed

of the motor..

Thus a real time control of the motor is obtained through the application

software

5.2. SCREEN SHOTS

51



6. CONCLUTION

In this project we designed an obstacle sensing robot. When ever the

robot finds any obstacle in front of it suddenly deviates its path in the

automatic mode. The user can also control the robot through the web and

monitoring is also possible in client as well as server side, in the manual

mode.

We used visual basic for the design of application software and

embedded ‘C’ to program the embedded microcontroller.

52

web based robotics

Documents