Download - Obstacle Avoidance Robot Project Report Final

Mini Project Report 2012 OBSTACLE AVOIDANCE ROBOT

1. INTRODUCTION

An embedded system is a system which is going to do a predefined specified task is

the embedded system and is even defined as combination of both software and hardware.

A general-purpose definition of embedded systems is that they are devices used to

control, monitor or assist the operation of equipment, machinery or plant. "Embedded"

reflects the fact that they are an integral part of the system. In many cases their

‘embeddedness’ may be such that their presence is far from obvious to the casual observer

and even the more technically skilled might need to examine the operation of a piece of

equipment for some time before being able to conclude that an embedded control system

was involved in its functioning. At the other extreme a general-purpose computer may be

used to control the operation of a large complex processing plant, and its presence will be

obvious.

All embedded systems are including computers or microprocessors. Some of these

computers are however very simple systems as compared with a personal computer. The

very simplest embedded systems are capable of performing only a single function or set of

functions to meet a single predetermined purpose. In more complex systems an application

program that enables the embedded system to be used for a particular purpose in a specific

application determines the functioning of the embedded system. The ability to have

programs means that the same embedded system can be used for a variety of different

purposes. In some cases a microprocessor may be designed in such a way that application

software for a particular purpose can be added to the basic software in a second process,

after which it is not possible to make further changes. The applications software on such

processors is sometimes referred to as firmware.

The simplest devices consist of a single microprocessor (often called a "chip”),

which may itself be packaged with other chips in a hybrid system or Application Specific

Integrated Circuit (ASIC). Its input comes from a detector or sensor and its output goes to a

Dept. of ECE 1 ICET, Muvattupuzha


switch or activator which (for example) may start or stop the operation of a machine or, by

operating a valve, may control the flow of fuel to an engine.

As the embedded system is the combination of both software and hardware

Fig1.0.1: Block diagram of Embedded System

Software deals with the languages like ALP, C, and VB etc., and Hardware deals with

Processors, Peripherals, and Memory.

o Memory: It is used to store data or address.

o Peripherals: These are the external devices connected

o Processor: It is an IC which is used to perform some task

Processors are classified into four types like:

1. Micro Processor (µp)

2. Micro controller (µc)

3. Digital Signal Processor (DSP)

4. Application Specific Integrated Circuits (ASIC)

Micro Processor (µp):

It is an electronic chip which performs arithmetic and logical operations with assistance of

internal memory.


EEPROM, ADC, DAC, Timers, USART,

OscillatorsEtc.,

ALU

CU

Memory


ALU

CONTROL UNIT

MEMORY

Fig1.0.2: Block Diagram of Micro Processor (µp)

Micro Controller (µc):

It is a highly integrated micro processor designed for specific use in embedded systems.

Fig1.0.3 Block Diagram of Micro Controller (µc)

1.1. Introduction to applications of embedded system:

Embedded controllers may be found in many different kinds of system and are used

for many different applications. The list, which follows, is indicative rather than exhaustive.

An item in the list may be relevant to a particular company because either (a) it is or

involves a core process or product, (b) it is or involves an ancillary function or service

performed by the company or (c) it refers to a product or service provided by a contractor

under some form of agreement and the vulnerability of the supplier may need to be

considered.

Some applications of embedded systems:

Manufacturing and process control



Construction industry

Transport

Buildings and premises

Domestic service

Communications

Office systems and mobile equipment

Banking, finance and commercial

Medical diagnostics, monitoring and life support

Testing, monitoring and diagnostic systems

Industrial functions of embedded systems:

A manufacturing company has provided the following list of embedded systems:

Multi-loop control and monitoring - DCS, SCADA, telemetry Panel mounted devices -

Control, display, recording and operations.

Safety and security - Alarm and trip systems, fire and gas systems, buildings and facilities

security.

Field devices-measurement, actuation.

Analytical systems -Laboratory systems; on-line/ plant systems.

Electrical supply - supply, measurement, control, protection.

Tools - for design, documentation, testing, maintenance.

Embedded systems compared with commercial systems:

The Year 2000 problem in embedded systems differs from the problem in

commercial / database / transaction processing systems (often referred to as IT systems) in a

number of ways. Firstly the user's problem may much lie much deeper than packages or

applications software. It may lie in and be inseparable from systems and operating software

and from hardware, i.e. in the platform on which the application software is based. When

users of IT systems have hardware or operating software problems they can and should be

made the concern of the computer supplier: typically, this is not the case with

microprocessors and devices based on them.



Secondly in embedded systems the concern is often with intervals rather than with

specific dates: the need may be for an event to occur at 100-day intervals rather than on the

5th day of each month. This has the implication that Year 2000 problems may reveal

themselves both before and for some time after 1 January 2000 and not at all on the date

itself.

The lifetime of embedded systems tends to be greater than that of commercial data

processing systems: they remain in use for longer without alteration to their software.

Because their software may therefore be older they are rendered more liable to Year 2000

problems.

1.2. An introduction to the project (OBSTACLE AVOIDING ROBOT):

A robot obstacle detection system comprising: a robot housing which navigates with

respect to a surface; a sensor subsystem having a defined relationship with respect to the

housing and aimed at the surface for detecting the surface, the sensor subsystem including:

an optical emitter which emits a directed beam having a defined field of emission, and a

photon detector having a defined field of view which intersects the field of emission of the

emitter at a finite region; and a circuit in communication with the detector for redirecting the

robot when the surface does not occupy the region to avoid obstacles.

Fig 1.2.1: Obstacle detection using sensor

Obstacle sensors are nothing but the IR pair. As the transmitter part travel IR rays

from to receiver here also transmitter send the data receiver but these IR pair are places



beside each other. So whenever the a obstacle senor got a obstacle in between its way the IR

rays reflects in a certain angle. As they are placed side by each.



2. BLOCK DIAGRAM

2.1. BLOCK DIAGRAM

Fig 2.1: Block Diagram

2.2. BLOCK DIAGRAM DESCRIPTION

MICRO CONTROLLER:

Here we are using AT89S52 controller. This is used to control all the operations of a

circuit to get the accurate result. The micro controller we use is of the 40 pins and of 4 ports.

Each port consists of the 8 pins. Generally the controller works on the transistor transistor

logic.

H BRIDGE:

H-Bridge is used as a driver circuit for motors. To move the robot in four different

directions we definitely need H-bridge as a interfacing circuit between controller and

motors.

DC MOTOR:

Motor are used for the movement of the robot. Here we use the dc motor as it has the

principle of the speed controlling.


MICRO-CONTROLLER

MOTOR DRIVER

RIGHT MOTOR

LEFT MOTOR


OBSTACLE SENSOR:

The obstacle senor is used avoiding the robot from the clash to any external devices (or) that

is like walls, any obstacle which comes in its way. Here we are using the IR

communications .the transmitter and the receiver parts. The transmitter produces the IR rays

and they are received by the receiver section.



3. HARDWARE DESCRIPTION

Hardware Modules:

The Hardware modules of this project are:

Microcontroller

H – Bridge

Motors

3.1 MICROCONTROLLER (AT89S52):

The AT89S52 is a low-power, high-performance CMOS 8-bit micro controller with

8Kbytes of in-system programmable flash memory. The device is manufactured Atmel’s

high-density nonvolatile memory technology and is compatible with the industry-standard

80C51 micro controller. The on-chip Flash allows the program memory to be reprogrammed

in-system or by a conventional nonvolatile memory programmer. By combining a versatile

8-bit CPU with in-system programmable flash one monolithic http; the Atmel AT89S52 is a

powerful micro controller, which provides a highly flexible and cost effective solution to

any cost effective solution to any embedded control applications to any embedded control

applications.

Features:

Compatible with MCS-51 Products

8K Bytes of In-System Programmable (ISP) Flash Memory Endurance: 1000

Write/Erase Cycles

4.0V to 5.5V Operating Range

Fully Static Operation: 0 Hz to 33 MHz

Three-level Program Memory Lock

256K Internal RAM

32 Programmable I/O Lines

16-bit Timer/Counters



Eight Interrupt Sources

Full Duplex UART Serial Channel

Low-power Idle and Power-down Modes

Interrupt Recovery from Power-down Mode

Watchdog Timer

Dual Data Pointer

Power-off Flag

Pin Diagram:

Fig 3.1.1: Pin diagram



Table 3.1: Pin Description of 89S52:

Pin No Function Name

1 External count input to Timer/Counter 2, clock-out T2 P1.0

2 Timer/Counter 2 capture/reload trigger and direction control T2 EX P1·1

3

8 bit input/output port (P1) pins

P1.2

4 P1.3

5 P1.4

6 P1.5

7 P1.6

8 P1.7

9 Reset pin; Active high Reset

10 Input (receiver) for serial

communication RxD

8 bit

input/output

port (P3)

pins

P3.0

11 Output (transmitter) for serial communication TxD P3.1

12 External interrupt 1 Into P3.2

13 External interrupt 2 Int1 P3·3

14 limer1 external input TO P3.4

15 limer2 external input T1 P3.5

16 Write to external data memory Write P3.6

17 Read from external data memory Read P3.7

18 Quartz crystal oscillator (up to 24 MHz)

Crystal 2

19 Crystal 1

20 Ground (OV) Ground

21

8 bit input/output port (P2) pins /

High-order address bits when interfacing with

external memory

P2·0/ A8

22 P2·1/ A9

23 P2·2/ A10

24 P2.3/ A11

25 P2.4/ A12

26 P2.5/ A13

27 P2.6/ A14

28 P2.7/ A15



29 Program store enable; Read from external program memory PSEN

30 Address Latch Enable ALE

Program pulse input during Flash programming Prog

31 External Access Enable; Vcc for internal program executions EA

Programming enable wltage; 12V (during Flash programming) Vpp

32

8 bit input/output port (PO) pins Low-order address bits when

interfacing with external memory

PO·7/ AD7

33 PO.6/ AD6

34 PO.5/ AD5

35 POA/ AD4

36 PO.3/ AD3

37 PO.2I AD2

38 PO.1/ AD1

39 PO.O/ ADO

40 Suoplv voltaqe: 5V (up to 6.6V) Vcc

Oscillator Characteristics:

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier

that can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz

crystal or ceramic resonator may be used. To drive the device from an External clock source,

XTAL2 should be left unconnected while XTAL1 is driven.

Fig 3.1.2: Oscillator connections



Special Function Register (SFR) Memory: Special Function Registers (SFR s) are areas

of memory that control specific functionality of the 8051 processor. For example, four SFRs

permit access to the 8051’s 32 input/output lines. Another SFR allows the user to set the

serial baud rate, control and access timers, and configure the 8051’s interrupt system.

Accumulator: The Accumulator, as its name suggests is used as a general register to

accumulate the results of a large number of instructions. It can hold 8-bit (1-byte) value and

is the most versatile register.

The “R” registers: The “R” registers are a set of eight registers that are named R0, R1. Etc.

up to R7. These registers are used as auxiliary registers in many operations.

The “B” registers: The “B” register is very similar to the accumulator in the sense that it

may hold an 8-bit (1-byte) value. Two only uses the “B” register 8051 instructions: MUL

AB and DIV AB.

Data Pointer: The Data pointer (DPTR) is the 8051’s only user accessible 16-bit (2Bytes)

register. The accumulator, “R” registers are all 1-Byte values. DPTR, as the name suggests,

is used to point to data. It is used by a number of commands, which allow the 8051 to access

external memory.

Program counter & Stack pointer: The program counter (PC) is a 2-byte address, which

tells the 8051 where the next instruction to execute is found in memory. The stack pointer

like all registers except DPTR and PC may hold an 8-bit (1-Byte) value.

Memory:

Special Function Registers (SFRs) are areas of memory that control specific functionality of

the 8051 processor. For example, four SFRs permit access to the 8051’s 32 input/output

lines. Another SFR allows the user to set the serial baud rate, control and access timers, and

configure the 8051’s interrupt system

.



Timer 2 Registers: Control and status bits are contained in registers T2CON and

T2MOD for Timer 2 . The register pair (RCAP2H , RCAP2L) are the Capture /

Reload registers for Timer 2 in 16-bit capture mode or 16-bit auto-reload mode .

Interrupt 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.

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. 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. Timer2 consists of two 8-bit

registers, TH2 and TL2. In the Timer function, the TL2 register is incremented every

machine cycle. Since a machine cycle consists of 12 oscillator 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 .When

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

incremented . Since two machine cycles (24 Oscillator periods ) are required to

recognize 1-to-0 transition , the maximum count rate is 1 / 24 of the oscillator

frequency . To ensure that a given level is sampled at least once before it changes

, the level should be held for at least one full machine cycle.

3.2. MOTORS

Motor is a device that creates motion, not an engine; it usually refers to either an

electrical motor or an internal combustion engine. It may also refer to a machine that

converts electricity into a mechanical motion

AC motor, an electric motor that is driven by alternating current

Synchronous motor, an alternating current motor distinguished by a rotor spinning

with coils passing magnets at the same rate as the alternating current and resulting

magnetic field which drives it



Induction motor, also called a squirrel-cage motor, a type of asynchronous

alternating current motor where power is supplied to the rotating device by means of

electromagnetic induction

DC motor, an electric motor that runs on direct current electricity

Brushed DC electric motor, an internally commutated electric motor designed to be

run from a direct current power source

Brushless DC motor, a synchronous electric motor which is powered by direct

current electricity and has an electronically controlled commutation system, instead

of a mechanical commutation system based on brushes

Electrostatic motor, a type of electric motor based on the attraction and repulsion of

electric charge

Servo motor, an electric motor that operates a servo, commonly used in robotics

Internal fan-cooled electric motor, an electric motor that is self-cooled by a fan,

typically used for motors with a high energy density

DC Motors

The brushed DC motor is one of the earliest motor designs. Today, it is the motor of

choice in the majority of variable speed and torque control applications.

Advantages

Easy to understand design

Easy to control speed

Easy to control torque

Simple, cheap drive design ,

Easy to understand design

The design of the brushed DC motor is quite simple. A permanent magnetic field is

created in the stator by either of two means: Permanent magnets or Electro-magnetic

windings



If the field is created by permanent magnets, the motor is said to be a "permanent

magnet DC motor" (PMDC). If created by electromagnetic windings, the motor is often said

to be a "shunt wound DC motor" (SWDC). Today, because of cost-effectiveness and

reliability, the PMDC motor is the motor of choice for applications involving fractional

horsepower DC motors, as well as most applications up to about three horsepower.

At five horsepower and greater, various forms of the shunt wound DC motor are most

commonly used. This is because the electromagnetic windings are more cost effective than

permanent magnets in this power range.

Caution: If a DC motor suffers a loss of field (if for example, the field power

connections are broken), the DC motor will immediately begin to accelerate to the top speed

which the loading will allow. This can result in the motor flying apart if the motor is lightly

loaded. The possible loss of field must be accounted for, particularly with shunt wound DC

motors.

Opposing the stator field is the armature field, which is generated by a changing

electromagnetic flux coming from windings located on the rotor. The magnetic poles of the

armature field will attempt to line up with the opposite magnetic poles generated by the

stator field. If we stopped the design at this point, the motor would spin until the poles were

opposite one another, settle into place, and then stop -- which would make a pretty useless

motor! However, we are smarter than that. The section of the rotor where the electricity

enters the rotor windings is called the commutator. The electricity is carried between the

rotor and the stator by conductive graphite-copper brushes (mounted on the rotor) which

contact rings on stator.

Imagine power is supplied: The motor rotates toward the pole alignment point. Just

as the motor would get to this point, the brushes jump across a gap in the stator rings.

Momentum carries the motor forward over this gap. When the brushes get to the other side

of the gap, they contact the stator rings again and -- the polarity of the voltage is reversed in

this set of rings! The motor begins accelerating again, this time trying to get to the opposite

set of poles. (The momentum has carried the motor past the original pole alignment point.)



This continues as the motor rotates. In most DC motors, several sets of windings or

permanent magnets are present to smooth out the motion.

Easy to control speed

Controlling the speed of a brushed DC motor is simple. The higher the armature

voltage, the faster the rotation. This relationship is linear to the motor's maximum speed.

The maximum armature voltage which corresponds to a motor's rated speed (these motors

are usually given a rated speed and a maximum speed, such as 1750/2000 rpm) are available

in certain standard voltages, which roughly increase in conjuntion with horsepower. Thus,

the smallest industrial motors are rated 90 VDC and 180 VDC. Larger units are rated at 250

VDC and sometimes higher.

Specialty motors for use in mobile applications are rated 12, 24, or 48 VDC. Other

tiny motors may be rated 5 VDC. Most industrial DC motors will operate reliably over a

speed range of about 20:1 -- down to about 5-7% of base speed. This is much better

performance than the comparible AC motor. This is partly due to the simplicity of control,

but is also partly due to the fact that most industrial DC motors are designed with variable

speed operation in mind, and have added heat dissipation features which allow lower

operating speeds.

Easy to control torque

In a brushed DC motor, torque control is also simple, since output torque is

proportional to current. If you limit the current, you have just limited the torque which the

motor can achieve. This makes this motor ideal for delicate applications such as textile

manufacturing.

Simple, cheap drive design

The result of this design is that variable speed or variable torque electronics are easy

to design and manufacture. Varying the speed of a brushed DC motor requires little more

than a large enough potentiometer. In practice, these have been replaced for all but sub-

fractional horsepower applications by the SCR and PWM drives, which offer relatively



precisely control voltage and current. Common DC drives are available at the low end (up to

2 horsepower) for under US$100 -- and sometimes under US$50 if precision is not

important.

Large DC drives are available up to hundreds of horsepower. However, over about

10 horsepower careful consideration should be given to the price/performance tradeoffs with

AC inverter systems, since the AC systems show a price advantage in the larger systems.

(But they may not be capable of the application's performance requirments).

Disadvantages

Expensive to produce

Can't reliably control at lowest speeds

Physically larger

High maintenance

Dust

WORKING OF DC MOTOR

In any electric motor, operation is based on simple electromagnetism. A current-

carrying conductor generates a magnetic field; when this is then placed in an external

magnetic field, it will experience a force proportional to the current in the conductor, and to

the strength of the external magnetic field. As you are well aware of from playing with

magnets as a kid, opposite (North and South) polarities attract, while like polarities (North

and North, South and South) repel. The internal configuration of a DC motor is designed to

harness the magnetic interaction between a current-carrying conductor and an

externalmagnetic field to generate rotational motion.


http://encyclobeamia.solarbotics.net/articles/current.html

http://encyclobeamia.solarbotics.net/articles/dc.html




Fig 3.2.1: Construction & Working

Principle

When a rectangular coil carrying current is placed in a magnetic field, a torque acts

on the coil which rotates it continuously. When the coil rotates, the shaft attached to it also

rotates and thus it is able to do mechanical work. Every DC motor has six basic parts -- axle,

rotor (a.k.a., armature), stator, commutator, field magnet(s), and brushes. In most common

DC motors (and all that BEAMers will see), the external magnetic field is produced by high-

strength permanent magnets1. The stator is the stationary part of the motor -- this includes

the motor casing, as well as two or more permanent magnet pole pieces. The rotor (together

with the axle and attached commutator) rotates with respect to the stator. The rotor consists

of windings (generally on a core), the windings being electrically connected to the

commutator. The above diagram shows a common motor layout -- with the rotor inside the

stator (field) magnets.

The geometry of the brushes, commentator contacts, and rotor windings are such that

when power is applied, the polarities of the energized winding and the stator magnet(s) are

misaligned, and the rotor will rotate until it is almost aligned with the stator's field magnets.

As the rotor reaches alignment, the brushes move to the next commentator contacts, and

energize the next winding. Given our example two-pole motor, the rotation reverses the

direction of current through the rotor winding, leading to a "flip" of the rotor's magnetic

field, driving it to continue rotating.



In real life, though, DC motors will always have more than two poles (three is a very

common number). In particular, this avoids "dead spots" in the commutator. You can

imagine how with our example two-pole motor, if the rotor is exactly at the middle of its

rotation (perfectly aligned with the field magnets), it will get "stuck" there. Meanwhile, with

a two-pole motor, there is a moment where the commutator shorts out the power supply (i.e.,

both brushes touch both commutator contacts simultaneously). This would be bad for the

power supply, waste energy, and damage motor components as well. Yet another

disadvantage of such a simple motor is that it would exhibit a high amount of torque "ripple"

(the amount of torque it could produce is cyclic with the position of the rotor).

Fig 3.2.2: Construction and Working

Parts of a DC Motor

Fig 3.2.3: Parts of a dc motor



Armature

A D.C. motor consists of a rectangular coil made of insulated copper wire wound on a soft

iron core. This coil wound on the soft iron core forms the armature. The coil is mounted on

an axle and is placed between the cylindrical concave poles of a magnet.

Commutator

A commutator is used to reverse the direction of flow of current. Commutator is a copper

ring split into two parts C1 and C2. The split rings are insulated form each other and mounted

on the axle of the motor. The two ends of the coil are soldered to these rings. They rotate

along with the coil. Commutator rings are connected to a battery. The wires from the battery

are not connected to the rings but to the brushes which are in contact with the rings.

Fig 3.2.4: Parts of dc motor II

Brushes

Two small strips of carbon, known as brushes press slightly against the two split rings, and

the split rings rotate between the brushes. The carbon brushes are connected to a D.C.

source.

Working of a DC Motor

When the coil is powered, a magnetic field is generated around the armature. The left

side of the armature is pushed away from the left magnet and drawn towards the right,

causing rotation.



Fig 3.2.5: Working of dc motor

When the coil turns through 900, the brushes lose contact with the commutator and

the current stops flowing through the coil.However the coil keeps turning because of its own

momentum. Now when the coil turns through 1800, the sides get interchanged. As a result

the commutator ring C1 is now in contact with brush B2 and commutator ring C2 is in contact

with brush B1. Therefore, the current continues to flow in the same direction.

Direction of Rotation

A DC Motor has two wires. We can call them the positive terminal and the negative

terminal, although these are pretty much arbitrary names (unlike a battery where these

polarities are vital and not to be mixed!). On a motor, we say that when the + wire is

connected to + terminal on a power source, and the - wire is connected to the - terminal

source on the same power source, the motor rotates clockwise (if you are looking towards

the motor shaft). If you reverse the wire polarities so that each wire is connected to the

opposing power supply terminal, then the motor rotates counter clockwise. Notice this is just

an arbitrary selection and that some motor manufacturers could easily choose the opposing

convention. As long as you know what rotation you get with one polarity, you can always

connect in such a fashion that you get the direction that you want on a per polarity basis.



Fig 3.2.6: Direction of rotation of dc motor

Motor Start and Stop

You are already well versed on how to control the motor speed, the motor torque and

the motor direction of rotation. But this is all fine and dandy as long as the motor is actually

moving. Starting a motor is a very hazardous moment for the system. Since you have an

inductance whose energy storage capacity is basically empty, the motor will first act as an

inductor. In a sense, it should not worry us too much because current can not change

abruptly in an inductor, but the truth of the matter is that this is one of the instances in which

you will see the highest currents flowing into the motor. The start is not necessarily bad for

the motor itself as in fact the motor can easily take this Inrush Current. The power stage, on

the other hand and if not properly designed for, may take a beating.

Once the motor has started, the motor current will go down from inrush levels to

whatever load the motor is at. Per example, if the motor is moving a few gears, current will

be proportional to that load and according to torque/current curves.

Stopping the motor is not as harsh as starting. In fact, stopping is pretty much a

breeze. What we do need to concern ourselves is with how we want the motor to stop. Do

we want it to coast down as energy is spent in the loop, or do we want the rotor to stop as

fast as possible? If the later is the option, then we need braking. Braking is easily



accomplished by shorting the motor outputs. The reason why the motor stops so fast is

because as a short is applied to the motor terminals, the Back EMF is shorted. Because Back

EMF is directly proportional to speed, making Back EMF = 0, also means making speed =0.

3.3 MOTORDRIVER CIRCUIT (h bridge)

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

control the motoion 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.

Fig 3.3.1: H-bridge basic circuit diagram

As we 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 changes its 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.

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.

Fig 3.3.2: H-Bridge working

Table 3.3: Direction of motor rotation

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

Here in this project we are using L293D Quadruple Half-H-Driver IC. The L293D is

a quadruple high-current half-H driver designed to provide bidirectional drive currents of up

to 600-mA at voltages from 4.5 V to 36 V. It is designed to drive inductive loads such as

relays, solenoids, dc and bipolar stepping motors, as well as other high-current/high-voltage

loads in positive-supply applications.

All inputs are TTL-compatible. Each output is a complete totem-pole drive circuit with a

Darlington transistor sink and a pseudo-Darlington source. Drivers are enabled in pairs with

drivers 1 and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN. When an enable

input is high, the associated drivers are enabled, and their outputs are active and in phase



with their inputs. External high-speed output clamp diodes should be used for inductive

transient suppression. When the enable input is low, those drivers are disabled, and their

outputs are off and in a high-impedance state. With the proper data inputs, each pair of

drivers form a full-H (or bridge) reversible drive suitable for solenoid or motor applications.

A VCC1 terminal, separate from VCC2, is provided for the logic inputs to minimize device

power dissipation. The L293D is designed for operation from 0°C to 70°C.

Fig 3.3.3: L293D H-driver (Pin out and Logic symbol)

Features

600-mA Output Current Capability Per Driver

Pulsed Current 1.2-A Per Driver

Output Clamp Diodes for Inductive Transient Suppression

Wide Supply Voltage Range 4.5 V to 36 V and Separate Input-Logic Supply

Thermal Shutdown

High-Noise-Immunity Inputs

3.4 IR SENSOR



Fig 3.4.1: IR Sensor pair

This sensor is a short range obstacle detector with no dead zone. It has a reasonably

narrow detection area which can be increased using the dual version. Range can also be

increased by increasing the power to the IR LEDs or adding more IR LEDs. The photo

shows my test setup with some IR LED's (dark blue) as a light source and two

phototransistors in parallel for the receiver. You could use one of each but I wanted to

spread them out to cover a wider area. This setup works like a Frits LDR but with IR. It has

a range of about 10-15cm (4-6 inches) with my hand as the object being detected.

Features Modulated IR transmitter

Ambient light protected IR receiver

pin easy interface connectors

Bus powered module

Indicator LED

Up to 12 inch range for white object

Can differentiate between dark and light colors.

Applications

Proximity Sensor

Obstacle Detector Sensor

Line Follower Sensor

Wall Follower Sensor



4. CIRCU IT

4.1. CIRCUIT DIAGRAM

Fig 4.1.1: Circuit Diagram



4.1. CIRCUIT LEVEL DESCRIPTION:

Basically the circuit consists of the following blocks:

Power Supply

Sensors

Microcontroller 89S52

Driver

Motors

Let us take the overview of each block one by one.

.

IR Transmitter & Receiver

The IR Transmitter block mainly used to generate IR signal. It uses simple program

to generate square wave which have continuous pulses of 50% duty cycle of frequency 38

KHz. This transmitter is so arranged that the IR rays are focused on the sensor.IR sensor

(TSOP 1738) which gives normally 5v at output of it. After receiving infrared light at output

of sensor we get 0v.

Microcontroller

This is the most important block of the system. Microcontroller is the decision

making logical device which has its own memory, I/O ports, CPU and Clock circuit

embedded on a single chip.

Driver

L293D is used as driver IC. Motors are connected to this IC. According to program

in µc it drives the left and right motor.

Power Supply Circuit

Here in this project we are using a D.C. Poweer supply. The power supply for

microcontroller and H-Driver ICs are regulated using regulator ICs.



Voltage Regulator:

A voltage regulator is an electrical regulator designed to automatically maintain a

constant voltage level. It may use an electromechanical mechanism, or passive or active

electronic components. Depending on the design, it may be used to regulate one or more AC

or DC voltages. There are two types of regulator are

Positive Voltage Series (78XX) and

Negative Voltage Series (79XX)

78XX: ’78’ indicate the positive series and ‘XX’ indicates the voltage rating.

Suppose 7805 produces the maximum 5V.’05’indicates the regulator output is 5V.

79XX:’78’ indicate the negative series and ‘XX’ indicates the voltage rating. Suppose 7905

produces the maximum -5V.’05’indicates the regulator output is -5V.These regulators

consists the three pins they are

Pin1: It is used for input pin.

Pin2: This is ground pin for regulator

Pin3: It is used for output pin. Through this pin we get the output.

Fig 4.1.2: Regulator circuit

Sensor Circuit

The sensors used in this project are three IR Receiver Transmitter LEDs. The

connections are shown as follows. As the receiver a photo diode is used, produce a zero

voltage level when it receives the signal.


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

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

http://en.wikipedia.org/wiki/Mechanism_(technology)

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

http://en.wikipedia.org/wiki/Regulator_(automatic_control)

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


Fig4.1.3: Sensor circuit

Microcontroller Circuit

Fig4.1.4: Microcontroller circuit

The Fig 4.1.4 shows all connection to AT89S52 Microcontroller. The Pins 7,8,12 are

connected to the receivers and the pins 32,33,38,39 are connected to motor driver input pins.

Also the pins 34 and 37 are connected to the motor driver enable pins. The crystal oscillator

circuit is connected to the pins 19 and 18 of microcontroller. The reset circuit is connected to

the microcontroller as shown in figure.


FROM MICROCONTROLLER


Motor Driver Circuit

The motor driver circuit consists of a driver IC L293D and two motors. The

connections are shown as in figure 4.1.5. One of the two supplies is for IC and other is to

provide sufficient current for motor rotation. The pins 2, 7 and 10,15 are the inputs of motor

from the microcontroller. The outputs of the IC are taken from pins 3, 6, 11, 14. These pins

are used to control the rotation of the motors according to the commands from

microcontroller.

Fig4.1.5: Motor driver circuits

The enable pins, the pins 1 and 9 are also connected to the microcontroller 89s52. This enables and disables the driver IC according to the commands from the microcontroller.



5. PCB DESIGN AND FABRICATION

5.1. PCB DESIGN

Designing of PCB is a major step in the production of PCB is a major. It forms a

distinct factor in electronic performance and reliability. The productivity of a PCB, its

assembly and service ability also depends on the design.

The designing of a PCB consists of designing of the layout followed by the

preparation of the artwork. The layout should include all the relevant aspects in details of the

PCB design while the art work preparation brings it to the form required for the production

process. The layout can be designed with the help of anyone of the standard layout edition

software’s such as Eagle, Orcad or Edwin XP. Hence a concept, clearly defining all the

details of the circuits and partly of the equipment, is a prerequisite and the actual layout can

start. Depending on the accuracy required, the artwork might be produced a 1:1 or 2:1 even

4:1 scale. It is best prepared on a 1:1 scale.

5.2. PCB FABRICATION

PCB fabrication involves the following steps:-

1) First the layout of the PCB is generated using the software ORCAD. First step involves

drawing the circuit CIS which is a section of ORCAD. Then the layout is obtained using

layout plus. This layout is printed on a paper.

2) This printed layout is transferred to a Mylar sheet and touched with black ink.

3) The solder side of the Myler sheet is placed on the shining side of the copper board and is

placed in a frame. It is than exposed to sunlight, with the Mylar sheet facing the sunlight.



4) The exposed copper board is put in hydrogen peroxide solution. It is then put in hot

water; shook till unexposed region becomes transparent.

5) This is put in cold water and then the rough side is struck in to the skill screen. This is

then pressed and dried well.

6) The plastic sheet of the five - star is removed leaving the pattern on the screen.

7) A copper clad sheet is cut to the size and cleaned. This is then placed under the screen.

8) Acid resist ink is spread on the screen, So that the pattern of the tracks and pad is

obtained on the copper clad sheet. It is dried.

9) The dried sheet is then etched using ferric chloride solution till all the unwanted copper is

etched away.

10) The unwanted resist ink is removed using sodium hydroxide solution, holes are then

drilled.

11) The components are soldered neatly on the board without dry soldering



5.3. COMPONENT LAYOUT

Fig 5.1: Component layout



5.4. PCB LAYOUT

Fig 5.2: PCB Layout



6. KEY FEATURES OF OBSTACLE AVOIDANCE ROBOT

6.1. ADVANTAGES

Collision control.

It Provides Safe Navigation.

This is the basic of all robot and has a Wide scope of extensions

6.2. LIMITATIONS

The performance of this robot mainly depends on the sensors and number of sensors.

The IR sensor used here is of commercial application so it may easily undergo

interference.

6.3. PROBLEMS FACED

Although the concept & design of the project seemed perfect, there were some

problems faced while actual implementation:

The arrangement of sensor: The arrangement of sensor should be in such a way that

the receiver detects the reflected signal from obstacle and it should not pick the transmitted

signal.

6.4. FUTURE ENHANCEMENTS

1. Adding a Camera: If the current project is interfaced with a camera (e.g. a Webcam) robot

can be driven beyond line-of-sight & range becomes practically unlimited as networks have

a very large range.

2. Use as a fire fighting robot: By adding temperature sensor, water tank and making some

changes in programming we can use this robot as fire fighting robot.



3. We can extend this project with wireless technology by IR (or) RF (or) ZIGBEE.

4. We can use the DTMF receiver by using the mobile phone.

5. This robot can be used for pick and place the required object by giving directions to the

robot but IR pair should be replaced depending upon the application.



7. CONCLUSION

The project is “obstacle detection and the avoidance robot” is practically proved by

using the IR pairs for sensing the robot, h bridge for the driving the dc motor, dc motor is

used for the movement of the robot with the help of the micro controller.



8. BIBILIOGRAPHY

TEXT BOOKS

“Micro Processor Architecture, Programming & Applications with the 8085 ”-

Ramesh S. Gaonkar,-Fifth Edition

“The 8051 Micro Controller”-Third Edition– Kenneth J. Ayala

WEB SITES

Wikipedia - The free encyclopedia

http://www.8051projects.info/

http://www.alldatasheet.com/

http://www.datasheet4u.com/

http://www.datasheetcatalog.com


http://www.datasheetcatalog.com/

http://www.datasheet4u.com/

http://www.alldatasheet.com/

http://www.8051projects.info/

Download - Obstacle Avoidance Robot Project Report Final

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