Automation 11

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ABSTRACT

When the concept of liberalization and globalization are introduced, the

through cutting competition is started. Each one is trying to fetch consumer by

offering quality service at low cost. A humanized effort seems inadequate in this era

making necessary the use of Electronics, Computer in the manufacturing processes

leading to the concept of Automated Manufacturing System (AMS).

The systems have been implemented in various companies and have seen

the positive results. The quality of the product mainly depends on the design of the

product, manufacturing system used and the continuous feedback which is used to

improve the quality. Automated Manufacturing system combines all these aspects to

change the raw material into a finished product. The result is that product quality

increases and decreases the overheads on the product thus the cost of product

decreases.

AMS combines the design aspect with manufacturing one to give a sound and

effective product. The efficiency of product depends on how it has been assembled.

Use of automated assembly system increases the scope of perfect fitting of the

product to greater extent. Also the paper contains Automated Material Handling andStorage devices. The automated QC process will increase the rate of inspection and

rate of passing defective parts decreases. It also facilitates inspection of number of

products with high rate and greater accuracy.

INTRODUCTION

1.1 INTRODUCTION TO PROJECT

This report describes the design, implementation, and evaluation of a wireless

controlled motor. The motivation behind this work is to build a PC based motor control

system that allows us to control the motor remotely using PC.

Many industries are moving towards automation. Skilled help is scarce and

expensive. Changes in todays manufacturing environment allow tedious, fatiguing,

and repetitive tasks to be mechanically performed by robots, as manually controlled

work is transitioned to auto-cycle control equipment.

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In this, motor can be operated remotely with the help of programming that is

done in C language. The flexibility is allowed in the motor controlled i.e. quick

reversal, speed control, precise rotation of the stepper motor through required step

angle. In this project wireless link between computer and motor is used. This system

provides movement in space for executing various tasks with proper interface to other

equipments machines and processes. It is having accuracy with which it can perform

its tasks

The project consists of wireless motor control using personal computer. As

project touches to three separate subjects i.e. Machine, Embedded system and

Wireless communication. To get an overview of project an introduction to each of

above mentioned subject is necessary. In next three chapter you will get an idea about

these subjects.

1.2 NEED OF THE AUTOMATION

In the early 70s due to liberalization and globalization no. of products

available in the market has revolutionary increased .Therefore, high competition in

the market so the manufactures have to reduce the market value of the product. A

single product of no. of qualities at different prices are available, this decreases the

individual sale of the companies, because every customer is to have best of the best

quality at the lowest price. But with the old technology it was not for manufactures to

satisfy such a need of the customer. That is there direct relation in quality of the

product and price of it.

In the 1970 Occupation Safety and Health Act (OSHA) protested the workers

from working under harmful conditions. Therefore employing workers for working in

hazardous conditions like heat treatment, spray painting is stopped. Also with the useof old technology during manufacturing the product there more scrap produced due to

trial and error method and product requires more time to get ready for delivering to

customers. i.e. more manufacturing lead time.

To solve the above problems in the manufacturing, engineers developed a

technology in which COMPUTERS are used to perform various functions in the

manufacturing and called this technology as AUTOMATION. In 1973 Later

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Harrington introduced the new term for automation called COMPUTER

INTEGRATED MANUFACTURING.

Automation is the integration of Total Quality Maintenance, Business Process

Reengineering, and Concurrent Engineering. Work Flow Automation, Flexible

Manufacturing Systems used to increase the production rate with low cost and to

protect workers from working under harmful conditions

1.3 DEFINITION AND TYPES OF AUTOMATION-

Automation is the technology concerned with the application

of mechanical, electronics and computer based systems to operate and control

production. The technology includes:

1. Automatic machine tools to process parts.

2. Automatic assembly machines.

3. Industrial robots.

4. Automatic material handling and storage systems.

5. Automatic inspection systems for quality control.

6. Feedback control and computer process control.

1.3.1 Types of Automation-

Automated production systems can be classified into basic

three types.

1) Fixed automation-

In this system the sequence of processing or assembly operation

is fixed by equipment configuration. The system may consist of co-ordination and

integration of many such operations which makes the system complex.

Features of fixed automation-

- High initial investment for custom engineered equipment.

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- High production rates.

- Relatively inflexible in accommodating product changes.

2) Programmable automation-

In this system the production equipment is designed with the capability to

change the sequence of operations to accommodate different product configuration.

The operation sequence is controlled by the program, which is set of instructions

coded so that system can read and interpret. New programs can be prepared and

entered into the equipment to produce the new product.

Features of programmable automation-

- High investment in general purpose equipment.

- Low production rates relative to fixed automation and suitable for

batch production.

- Flexibility to deal with changes in the product configuration.

3) Flexible automation-

A flexible automation system is one of that is capable of

producing variety of products (or parts) with virtually no loss of time for

changeover from one product to next. There is no production time lost while

reprogramming the system and altering the physical setup. Therefore, system

can produce various combinations and schedules of product instead of

requiring that they be made in separate batches.

1.4 BASIC PRINCIPLE OF AUTOMATION-

American production and inventory control has given

principle for automation which is as follows:

1) Understanding the existing process:

The purpose of this step is to comprehend the current

process in all of its details. What are inputs? What exactly happens to work unit

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between input and output? What is the function of the process? What are the up-

stream and down-stream operations in the production sequence and can them be

combined with the process under consideration.

2) Simplification of the process:

Once the existing process is understood the search will

begin for ways to simplify. This often involves a checklist of the existing process.

What is the use of this step? can this be eliminated? Can this be simplified or

combined to any other step. Etc.

3) Automate the process:

Once the processes have been reduced to its simplest form then automation

can be considered. The possible forms of automation i.e. use of computers and

electronics,

1.5 USE OF MOTORS IN MATERIAL HANDLING SYSTEM:

The purpose of material handling system in a factory is to move raw

materials, work- in- progress, finished parts, tools and supplies from one location to

another to facilitate the overall operations of manufacturing. It should be performed

safely, efficiently (at low cost), in a timely manner, accurately (the right material in

the right quantity to the right location), and without damage to material.

Types of material handling equipments

I. Hand truck

II. Powered truck

III. Crains, monorails and hoists

IV. Conveyors

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1.5.1 Conveyor System

This system is used when the materials are required to be

moved in relatively large quantities between specific locations over a fixed path. The

conveyor can be either gravity driven or powered. A common feature of powered

conveyor system is that the driving mechanism is built into the conveyor pathitself.

Types of conveyors

a) Rolled conveyors :

In this the pathway consists of a series of tubes (rollers) that are

perpendicular to the direction of travel. The rollers are contained in a fixedframe which elevates the pathway above the floor level from several inches.

Flat pallets or tote pans carrying unit loads are moved forward as rollers rotate.

Roller conveyors can be used for delivering load between manufacturing

operations, delivery to and from storage and distribution applications.

b) Skate wheel conveyor:

In this type of conveyors skate wheels are rotating on the shaftconnected to the frame are used to roll the pallet or tote pan or other container along

the pathway. It is used to transport lighter loads (due to continued contact).

c) Belt conveyors:

These types of conveyors are available in two types. FLAT

BELT for pallets parts or even certain types of bulk material and TROUGHED

BELTS for bulk materials. Material is placed on the surface and traveled along thepathway. The belt is made in a continuous loop and half of its length is used to

handle the material. At each end of the conveyor driver rolls are present to power the

belt.

c) Chain conveyors :

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Chain conveyors are made of loops of endless chain in an over-

and-under configuration around the powered sprockets at the end of the pathway.

There may be one or more chains working parallel. The chain slides along the channel

or they use rollers to slide the channel. The loads are generally ride along the top of

the chain.

d) Slat conveyor :

The slat conveyors uses individual platform, called slats that are

connected to a continuously moving chain. The drive mechanism is powered by chain

and the load is placed on the flat surface of the slat.

1.5.2 Automated Guided Vehicle System (AGVS) :

AGVS is a material handling system that uses independently

operated, self propelled vehicles that are guided along the defined pathways in the

floor. The vehicles are powered by means of on-board batteries that allow operation

for several hours between recharging. The definition of the pathway is generally

accomplished using wires embedded in floor or reflective paint on the floor surface.

Guidance is achieved by sensors on the vehicle that can follow the guide wires or

paint.

Types:

a) Driverless trains

It consists of towing vehicle that pulls one or more trailers to form

a train. It is useful in applications where heavy pay loads must be moved to a large

distance in factories with intermediate pick-up and drop-off.

b) AGVS pallets trucks

These are used to move palletized load along predetermined rout.

In the typical application the vehicle is backed into the loaded pallet by human worker

who steers the truck and uses its forks to elevate the load slightly. Then the worker

drives the pallet truck to the guide path, programs its destinations for unloading.. Its

capacity is 6000 lb. The more recent introduction related to the pallet

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truck is the forklift AGV. This vehicle can achieve significant vertical movement of

its fork to reach loads to shelves.

c) AGVS unit load carriers

This type is used to move unit load from one station to another

station. They are equipped with automatic loading and unloading by means of

powered rollers. They are of two types: Light load AGV and Assembly line AGV.

Assembly line AGV serves for heavy duty purposes.

Engineering Work Flow Automation, Flexible Manufacturing Systems used

to increase the production rate with low cost and to protect workers from working

under harmful conditions

1.6 WHY WIRELESS?

Wireless technologies and networks exist simply because people want

mobility. People want the ability to access information without being required to

plug in to a network.

Simply put, wireless is any communications method that does not depend on wires(metallic or fiber) for the transmission of communications signals. Wireless

communications provides connectivity between two or more devices (a transmitter

and a receiver) enabling them to exchange information. The fundamental difference

between wireless communication and other wired forms of communications is the

medium over which the encoded energy containing information is transferred between

the transmitter and receiver. In wireless systems energy transfer occurs through air or

through free space without a physical connection between the devices. The energy

transfer can be visible optical radiation, invisible infrared, ultraviolet or radio

frequency (RF) to name a few.

In general, people want instant access to resources wherever they are!

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2. LITERATURE SURVEY:

2.1 STEPPER MOTOR:

A stepper motor is a brushless, synchronous electrical motor that can divide a

full rotation into a large number of steps, for example, 200 steps. Thus the motor can

be turned to a precise angle.

2.1.1 Fundamentals of Operation:

Stepper motors operate differently from normal DC motors, which simply spin when

voltage is applied to their terminals. Stepper motors, on the other hand, effectively

have multiple "toothed" electromagnets arranged around a central metal gear, as

shown at right. To make the motor shaft turn, first one electromagnet is given power,

which makes the gear's teeth magnetically attracted to the electromagnet's teeth.

When the gear's teeth are thus aligned to the first electromagnet, they are slightly

offset from the next electromagnet. So when the next electromagnet is turned on and

the first is turned off, the gear rotates slightly to align with the next one, and from

there the process is repeated. Each of those slight rotations is called a "step." In that

way, the motor can be turned a

The top electromagnet (1) is turned off, The bottom electromagnet (3) is charged;

Thee right electromagnet (2) is charged, another 3.6 rotation occurs

pulling the nearest four teeth to the right.

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This results in a rotation of 3.6.

The left electromagnet (4) is enabled, rotating again by 3.6.

When the top electromagnet (1) is again charged,

the teeth in the sprocket will have rotated by one tooth position;

Since there are 25 teeth,

it will take 100 steps to make a full rotation.

Fig 2.1 Principle of Stepper Motor

Precise angle. There are two basic arrangements for the electromagnetic coils: bipolarand unipolar.

2.1.2 Unipolar motor

In a unipolar stepper motor, there are four separate electromagnets. To turn the motor,

first coil "1" is given current, then it's turned off and coil 2 is given current, then coil

3, then 4, and then 1 again in a repeating pattern. Current is only sent through the coils

in one direction; thus the name unipolar.

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A unipolar stepper motor will have 5 or 6 wires coming out of it. Four of those wires

are each connected to one end of one coil. The extra wire (or 2) is called "common."

To operate the motor, the "common" wire(s) is(are) connected to the supply voltage,

and the other four wires are connected to ground through transistors, so the transistors

control whether current flows or not. A microcontroller or stepper motor controller is

used to activate the transistors in the right order. This ease of operation makes

unipolar motors popular with hobbyists; they are probably the cheapest way to get

precise angular movements.

(For the experimenter, one way to distinguish common wire from a coil-end wire is

by measuring the resistance. Resistance between common wire and coil-end wire is

always half of what it is between coil-end and coil-end wires. This is due to the fact

that there is actually twice the length of coil between the ends and only half from

center (common wire) to the end.)

2.1.3 Bipolar motor

There are only two coils, and current must be sent through a coil first in one direction

and then in the other direction; thus the name bipolar. Bipolar motors need more than

4 transistors to operate them, but they are also more powerful than a unipolar motor of

the same weight. To be able to send current in both directions, engineers can use an

H-bridge to control each coil or a step motor driver chip.

Theory

A step motor can be viewed as a DC motor with the number of poles (on both rotor

and stator) increased, taking care that they have no common denominator.

Additionally, soft magnetic material with many teeth on the rotor and stator cheaply

multiplies the number of poles (reluctance motor). Like an AC synchronous motor, it

is ideally driven by sinusoidal current, allowing a step less operation, but this puts

some burden on the controller. When using an 8-bit digital controller, 256 micro steps

per step are possible. As a digital-to-analog converter produces unwanted ohmic heat

in the controller, pulse-width modulation is used instead to regulate the mean current.

Simpler models switch voltage only for doing a step, thus needing an extra current

limiter: for every step, they switch a single cable to the motor. Bipolar controllers can

switch between supply voltage, ground, and unconnected. Unipolar controllers can

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only connect or disconnect a cable, because the voltage is already hard wired.

Unipolar controllers need center-tapped windings.

It is possible to drive unipolar stepper motors with bipolar drivers. The idea is to

connect the output pins of the driver to 4 transistors. The transistor must be grounded

at the emitter and the driver pin must be connected to the base. Collector is connected

to the coil wire of the motor.

Stepper motors are rated by the torque they produce. Synchronous electric motors

using soft magnetic materials (having a core) have the ability to provide position

holding torque (called detent torque, and sometimes included in the specifications)

while not driven electrically. To achieve full rated torque, the coils in a stepper motor

must reach their full rated current during each step. The voltage rating (if there is one)

is almost meaningless. The motors also suffer from EMF, which means that once the

coil is turned off it starts to generate current because the motor is still rotating. There

needs to be an explicit way to handle this extra current in a circuit otherwise it can

cause damage and affect performance of the motor.

2.1.4 Applications

Computer-controlled stepper motors are one of the most versatile forms of positioning

systems, particularly when digitally controlled as part of a servo system. Stepper

motors are used in floppy disk drives, flatbed scanners, printers, plotters and many

more devices. Note that hard drives no longer use stepper motors to position the

read/write heads, instead utilizing a voice coil and servo feedback for head

positioning.

Stepper motors can also be used for positioning of valve pilot stages, for fluid control

systems.

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2.2 DC MOTOR CONTROL

2.2.1 Principle :

A simple DC electric 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 toward the

right, causing rotation.

The armature continues to

rotate.

Fig 2 DC Motor Principle

When the armature becomes

horizontally aligned, the

commutator reverses the

direction of current through the

coil, reversing the magnetic

field. The process then repeats.

If the shaft of a DC motor is turned by an external force, the motor will act like a

generator and produce an Electromotive force (EMF). During normal operation, the

spinning of the motor produces a voltage, known as the counter-EMF (CEMF) or

back EMF, because it opposes the applied voltage on the motor. This is the same

EMF that is produced when the motor is used as a generator (for example when an

electrical load (resistance) is placed across the terminals of the motor and the motor

shaft is driven with an external torque). Therefore, the voltage drop across a motor

consists of the voltage drop, due to this CEMF, and the parasitic voltage drop

resulting from the internal resistance of the armature's windings. The current through

a motor is given by the following equation:

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I= (Vapplied Vcemf) /Rarmature

The mechanical power produced by the motor is given by:

P=I* (Vapplied Vcemf)

2.2.2 Mechanism of the DC motors:

When current passes through the coil wound around a soft iron core the side of the

positive pole is acted upon by an upwards force, while the other side is acted upon by

a downward force. According to Fleming's left hand rule, the forces cause a turning

effect on the coil making it rotate; to make the motor rotate in a constant direction

"direct current" commutators make the current reverse in direction every half a cycle

thus causing the motor to rotate in the same direction. The problem facing the motor

is when the plane of the coil is parallel to the magnetic field; i.e. the turning effect is

ZERO-when coil is at 90 degree from its original position-yet, the coil continues to

rotate by inertia.

Since the CEMF is proportional to motor speed, when an electric motor is first started

or is completely stalled, there is zero CEMF. Therefore the current through the

armature is much higher. This high current will produce a strong magnetic field which

will start the motor spinning. As the motor spins, the CEMF increases until it is equal

to the applied voltage, minus the parasitic voltage drop. At this point, there will be a

smaller current flowing through the motor. Basically, the following three equations

can be used to find the speed, current, and back EMF of a motor under a load:

Load= Vcemf *I

Vapplied=I*Rarmature + Vcemf

Vcemf =speed*Fluxarmature

2.2.3 Speed control:

Generally, the rotational speed of a DC motor is proportional to the voltage applied to

it, and the torque is proportional to the current. Speed control can be achieved by

variable battery tapping, variable supply voltage, resistors or electronic controls. The

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direction of a wound field DC motor can be changed by reversing either the field or

armature connections but not both. This is commonly done with a special set of

contactors (direction contactors).

The effective voltage can be varied by inserting a series resistor or by an

electronically controlled switching device made of thyristors, transistors, or, formerly,

mercury arc rectifiers. In a circuit known as a chopper, the average voltage applied to

the motor is varied by switching the supply voltage very rapidly. As the "on" to "off"

ratio is varied to alter the average applied voltage, the speed of the motor varies. The

percentage "on" time multiplied by the supply voltage gives the average voltage

applied to the motor. Therefore, with a 100 V supply and a 25% "on" time, the

average voltage at the motor will be 25 V. During the "off" time, the armature's

inductance causes the current to continue flowing through a diode called a "flywheel

diode", in parallel with the motor. At this point in the cycle, the supply current will be

zero, and therefore the average motor current will always be higher than the supply

current unless the percentage "on" time is 100%. At 100% "on" time, the supply and

motor current are equal. The rapid switching wastes less energy than series resistors.

This method is also called pulse width modulation, or PWM, and is often controlled

by a microprocessor. An output filter is sometimes installed to smooth the average

voltage applied to the motor and reduce motor noise.

Since the series-wound DC motor develops its highest torque at low speed, it is often

used in traction applications such as electric locomotives, and trams. Another

application is starter motors for petrol and small diesel engines. Series motors must

never be used in applications where the drive can fail (such as belt drives). As the

motor accelerates, the armature (and hence field) current reduces. The reduction in

field causes the motor to speed up (see 'weak field' in the last section) until it destroys

itself. This can also be a problem with railway motors in the event of a loss of

adhesion since, unless quickly brought under control, the motors can reach speeds far

higher than they would do under normal circumstances. This can not only cause

problems for the motors themselves and the gears, but due to the differential speed

between the rails and the wheels it can also cause serious damage to the rails and

wheel treads as they heat and cool rapidly. Field weakening is used in some electronic

controls to increase the top speed of an electric vehicle. The simplest form uses a

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contactor and field weakening resistor, the electronic control monitors the motor

current and switches the field weakening resistor into circuit when the motor current

reduces below a preset value (this will be when the motor is at its full design speed).

Once the resistor is in circuit, the motor will increase speed above its normal speed at

its rated voltage. When motor current increases, the control will disconnect the

resistor and low speed torque is made available.

One interesting method of speed control of a DC motor is the Ward-Leonard control.

It is a method of controlling a DC motor (usually a shunt or compound wound) and

was developed as a method of providing a speed-controlled motor from an AC supply,

though it is not without its advantages in DC schemes. The AC supply is used to drive

an AC motor, usually an induction motor that drives a DC generator or dynamo. The

DC output from the armature is directly connected to the armature of the DC motor

(sometimes but not always of identical construction). The shunt field windings of both

DC machines are independently excited through variable resistors. Extremely good

speed control from standstill to full speed, and consistent torque, can be obtained by

varying the generator and/or motor field current. This method of control was the de

facto method from its development until it was superseded by solid state thyristor

systems. It found service in almost any environment where good speed control was

required, from passenger lifts through to large mine pit head winding gear and even

industrial process machinery and electric cranes. Its principal disadvantage was that

three machines were required to implement a scheme (five in very large installations,

as the DC machines were often duplicated and controlled by a tandem variable

resistor). In many applications, the motor-generator set was often left permanently

running, to avoid the delays that would otherwise be caused by starting it up as

required. Although electronic (thyristor) controllers have replaced most small tomedium Ward Leonard systems, some very large ones (thousands of horsepower)

remain in service. The field currents are much lower than the armature currents,

allowing a moderate sized thyristors unit to control a much larger motor than it could

control directly. For example, in one installation, a 300 amp thyristor unit controls the

field of the generator. The generator output current is in excess of 15,000 amps, which

would be prohibitively expensive (and inefficient) to control directly with thyristors.

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2.3 INDUCTION MOTOR :

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2.3.1Stator

The stator is the outer body of the motor which houses the driven

windings on an iron core. In a single speed three phase motor design, the

standard stator has three windings, while a single phase motor typically

has two windings.

The winding configuration, slot configuration and lamination steel all have an

effect on the performance of the motor. The voltage rating of the motor

is determined by the number of turns on the stator and the power rating

of the motor is determined by the losses which comprise copper loss and

iron loss, and the ability of the motor to dissipate the heat generated by

the losses. The stator design determines the rated speed of the motor and

most of the full load, full speed characteristics.

2.3.2 Rotor

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The Rotor comprises a cylinder made up of round laminations pressed onto the

motor shaft, and a number of short-circuited windings. The rotor

windings are made up of rotor bars passed through the rotor, from one

end to the other, around the surface of the rotor. The bars protrude

beyond the rotor and are connected together by a shorting ring at each

end. The bars are usually made of aluminium or copper, but sometimes

made of brass. The position relative to the surface of the rotor, shape,

cross sectional area and material of the bars determine the rotor

characteristics. Essentially, the rotor windings exhibit inductance and

resistance, and these characteristics can effectively be dependant on the

frequency of the current flowing in the rotor.

A bar with a large cross sectional area will exhibit a low resistance,

while a bar of a small cross sectional area will exhibit a high resistance.

Likewise a copper bar will have a low resistance compared to a brass

bar of equal proportions.

Positioning the bar deeper into the rotor, increases the amount of iron

around the bar, and consequently increases the inductance exhibited by

the rotor. The impedance of the bar is made up of both resistance and

inductance, and so two bars of equal dimensions will exhibit different

A.C. impedance depending on their position relative to the surface of the

rotor. A thin bar which is inserted radialy into the rotor, with one edge

near the surface of the rotor and the other edge towards the shaft, will

effectively change in resistance as the frequency of the current changes.

This is because the A.C. impedance of the outer portion of the bar is

lower than the inner impedance at high frequencies lifting the effective

impedance of the bar relative to the impedance of the bar at low

frequencies where the impedance of both edges of the bar will be lower

and almostequal.

The rotor design determines the starting characteristics.

2.3.3Equivalent Circuit

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The induction motor can be treated essentially as a transformer for analysis.

The induction motor has stator leakage reactance, stator copper loss

elements as series components, and iron loss and magnetizing

inductance as shunt elements. The rotor circuit likewise has rotor

leakage reactance, rotor copper (aluminium) loss and shaft

Fig .3 Equivalent Circuit Diagram of Induction Motor

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Power as series elements.

The transformer in the centre of the equivalent circuit can be eliminated

by adjusting the values of the rotor components in accordance with the

effective turns ratio of the transformer.

From the equivalent circuit and a basic knowledge of the operation of

the induction motor, it can be seen that the magnetizing current

component and the iron loss of the motor are voltage dependant, and not

load dependant. Additionally, the full voltage starting current of a

particular motor is voltage and speed dependant, but not load

dependant.

The magnetizing current varies depending on the design of the motor.

For small motors, the magnetizing current may be as high as 60%, but

for large two pole motors, the magnetizing current is more typically 20 -

25%. At the design voltage, the iron is typically near saturation, so the

iron loss and magnetizing current do not vary linearly with voltage with

small increases in voltage resulting in a high increase in magnetizing

current and iron loss.

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2.3.4 Starting Characteristics.

In order to perform useful work, the induction motor must be started

from rest and both the motor and load accelerated up to full speed.

Typically, this is done by relying on the high slip characteristics of the

motor and enabling it to provide the acceleration torque.

Induction motors at rest, appear just like a short circuited transformer,

and if connected to the full supply voltage, draw a very high current

known as the "Locked Rotor Current". They also produce torque which

is known as the "Locked Rotor Torque". The Locked Rotor Torque

(LRT) and the Locked Rotor Current (LRC) are a function of the

terminal voltage to the motor, and the motor design. As the motor

accelerates, both the torque and the current will tend to alter with rotor

speed if the voltage is maintained constant.

The starting current of a motor, with a fixed voltage, will drop very

slowly as the motor accelerates and will only begin to fall significantly

when the motor has reached at least 80% full speed. The actual curves

for induction motors can vary considerably between designs, but the

general trend is for a high current until the motor has almost reached

full speed. The LRC of a motor can range from 500% Full Load

Current (FLC) to as high as 1400% FLC. Typically, good motors fall in

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the range of 550% to 750% FLC.

Fig 4. Torque Speed Characteristic of Induction Motor

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The starting torque of an induction motor starting with a fixed voltage,

will drop a little to the minimum torque known as the pull up torque as

the motor accelerates, and then rise to a maximum torque known as the

breakdown orpull outtorque at almost full speed and then drop to zero

at synchronous speed. The curve of start torque against rotor speed is

dependant on the terminal voltage and the motor/rotor design.

The LRT of an induction motor can vary from as low as 60% Full Load

Torque (FLT) to as high as 350% FLT. The pull-up torque can be as low

as 40% FLT and the breakdown torque can be as high as 350% FLT.

Typical LRTs for medium to large motors are in the order of 120% FLT

to 280% FLT.

The power factor of the motor at start is typically 0.1 - 0.25, rising to a maximum as

the motor accelerates, and then falling again as the motor approaches full speed.

A motor which exhibits a high starting current, i.e. 850% will generally produce a low

starting torque, whereas a motor which exhibits a low starting current, will usually

produce a high starting torque. This is the reverse of what is generally expected.

The induction motor operates due to the torque developed by the interaction of the

stator field and the rotor field. Both of these fields are due to currents which have

resistive or in phase components and reactive or out of phase components. The torque

developed is dependant on the interaction of the in phase components and

consequently is related to the I2R of the rotor. A low rotor resistance will result in the

current being controlled by the inductive component of the circuit, yielding a high out

of phase current and a low torque.Figures for the locked rotor current and locked rotor torque are almost always quoted

in motor data, and certainly are readily available for induction motors. Some

manufactures have been known to include this information on the motor name plate.

One additional parameter which would be of tremendous use in data sheets for those

who are engineering motor starting applications, is the starting efficiency of the

motor. By the starting efficiency of the motor, I refer to the ability of the motor to

convert amps into newton meters. This is a concept not generally recognized within

the trade, but one which is extremely useful when comparing induction motors. The

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easiest means of developing a meaningful figure of merit, is to take the locked rotor

torque of the motor (as a percentage of the full load torque) and divide it by the

locked rotor current of the motor (as a percentage of the full load current).

If the terminal voltage to the motor is reduced while it is starting, the current

drawn by the motor will be reduced proportionally. The torque developed by the

motor is proportional to the current squared, and so a reduction in starting voltage will

result in a reduction in starting current and a greater reduction in starting torque. If the

start voltage applied to a motor is halved, the start torque will be a quarter; likewise a

start voltage of one third will result in a start torque of one ninth.

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2.3.5 Running Characteristics.

Once the motor is up to speed, it operates at low slip, at a speed

determined by the number of stator poles. The frequency of the current

flowing in the rotor is very low. Typically, the full load slip for a

standard cage induction motor is less than 5%. The actual full load slip

of a particular motor is dependant on the motor design with typical full

load speeds of four pole induction motor varying between 1420 and 1480

RPM at 50 Hz. The synchronous speed of a four pole machine at 50 Hz

is 1500 RPM and at 60 Hz a four pole machine has a synchronous speed

of 1800 RPM.

The induction motor draws a magnetizing current while it is operating.

The magnetizing current is independent of the load on the machine, but

is dependant on the design of the stator and the stator voltage. The

actual magnetizing current of an induction motor can vary from as low

as 20% FLC for large two pole machines to as high as 60% for small

eight pole machines. The tendency is for large machines and high speed

machines to exhibit a low magnetizing current, while low speed

machines and small machines exhibit a high magnetizing current. A

typical medium sized four pole machine has a magnetizing current of

about 33% FLC.

A low magnetizing current indicates a low iron loss, while a high

magnetizing current indicates an increase in iron loss and a resultant

reduction in operating efficiency.

The resistive component of the current drawn by the motor while

operating, changes with load, being primarily load current with a small

current for losses. If the motor is operated at minimum load, i.e. open

shaft, the current drawn by the motor is primarily magnetizing current

and is almost purely inductive. Being an inductive current, the power

factor is very low, typically as low as 0.1. As the shaft load on the motor

is increased, the resistive component of the current begins to rise. The

average current will noticeably begin to rise when the load current

approaches the magnetizing current in magnitude. As the load current

increases, the magnetizing current remains the same and so the power

factor of the motor will improve. The full load power factor of an

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induction motor can vary from 0.5 for a small low speed motor up to 0.9

for a large high speed machine.

The losses of an induction motor comprise: iron loss, copper loss,

windage loss and frictional loss. The iron loss, windage loss and

frictional losses are all essentially load independent, but the copper loss

is proportional to the square of the stator current. Typically the

efficiency of an induction motor is highest at 3/4 load and varies from

less than 60% for small low speed motors to greater than 92% for large

high speed motors. Operating power factor and efficiencies are generally

quoted on the motor data sheets.

2.3.6 Design Classification.

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There are a number of design/performance classifications which are somewhat

uniformly accepted by different standards organizations. These design

classifications apply particularly to the rotor design and hence affect the

starting characteristics of the motors. The two major classifications of

relevance here are design A, and design B.

Design A motors have a shallow bar rotor, and are characterised by a

very high starting current and a low starting torque. Typical values are

850% current and 120% torque. Shallow bar motors usually have a low

slip, i.e. 1480 RPM.

Design B motors have a deeper bar rotor and are characterised by

medium start current and medium starting torque. Typical design B

values are 650% current and 180% torque. The slip exhibited by design

B motors is usually greater than the equivalent design A motors. i.e.

1440 RPM.

Design F motors are often known as Fan motors having a high rotor

resistance and high slip characteristics. The high rotor resistance

enables the fan motor to be used in a variable speed application where

the speed is reduced by reducing the voltage. Design F motors are used

primarily in fan control applications with the motor mounted in the air

flow. These are often rated as AOM or Air Over Motor machines.

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2.3.7 Single phase motors.

In order for a motor to develop a rotating torque in one direction, it is

important that the magnetic field rotates in one direction only. In the

case of the three phase motor, there is no problem and the field follows

the phase sequence. If voltage is applied to a single winding, there are

still multiples of two poles which alternate between North and South at

the supply frequency, but there is no set rotation for the vectors. This

field can be correctly considered to be two vectors rotating in opposite

directions. To establish a direction of rotation for the vector, a second

phase must be added. The second phase is applied to a second winding

and is derived from the first phase by using the phase shift of a capacitor

in a capacitor start motor, or inductance and resistance in an induction

start motor. (sometimes known as a split phase motor.) Small motors use

techniques such as a shaded pole to set the direction of rotation of the

motor.

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2.3.7 Slip Ring Motors.

Slip ring motors or wound rotor motors are a variation on the standard

cage induction motors. The slip ring motor has a set of windings on the

rotor which are not short circuited, but are terminated to a set of slip

rings for connection to external resistors and contactors. The slip ring

motor enables the starting characteristics of the motor to be totally

controlled and modified to suit the load. A particular high resistance can

result in the pull out torque occurring at almost zero speed providing a

very high locked rotor torque at a low locked rotor current. As the

motor accelerates, the value of the resistance can be reduced altering the

start torque curve in a manner such that the maximum torque is

gradually moved towards synchronous speed. This results in a very high

starting torque from zero speed to full speed at a relatively low starting

current. This type of starting is ideal for very high inertia loads allowing

the machine to get to full speed in the minimum time with minimum

current draw.

The down side of the slip ring motor is that the slip rings and brush

assemblies need regular maintenance which is a cost not applicable to

the standard cage motor. If the rotor windings are shorted and a start is

attempted, i.e. the motor is converted to a standard induction motor, it

will exhibit an extremely high locked rotor current, typically as high as

1400% and a very low locked rotor torque, perhaps as low as 60%. In

most applications, this is not an option.

Another use of the slip ring motor is as a means of speed control. By

modifying the speed torque curve, by altering the rotor resistors, the

speed at which the motor will drive a particular load can be altered.

This has been used in winching type applications, but does result in a lot

of heat generated in the rotor resistors and consequential drop in overall

efficiency.

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2.4 JUSTIFICATION

In this project, we are trying to implement a motor control system which can

control the Induction motor , DC motor , stepper motor placed at the Remote location

In case of the stepper motor control we can control step angle with great degree of

accuracy. A D.C, motor speed can be controlled smoothly. A motor can be quickly

reversed in rotation, & stopped. . This project will certainly provide a window into the

fascinating world of Automation.

The objective is to control the all motors of the higher rating like the three

phase motor through a computer interfaced system. Considering to techno-economical

constraints the project will be a prototype having fewer features as compared to

commercially available one.

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3. DEVELOPMENT OF SYSTEM

3.1 BLOCK DIAGRAM

Fig 5 Block Diagram of PC Based Motor Control System

32

PersonalComputer

ParallelPort

Opto-coupler

Encoder

RFTransmitter

RFReceiver

Decoder Motor driver4:16

Converter

Motors

1. Stepper

2. D.C.

3.Induction


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This system is divided into three sections:

1. Remote Section

2. Local Control Section

3. Motor Section.

1. Remote Section:

It is nothing but remote PC interfaced encoder & RF transmitter set which is

present in the remote place. This may be your workspace (office / school). Signals

are sent through this computer.

2. Local Control Section:

This is a PC based control system through which you can control your system.

This contains RF receiver along with decoder motor control system. The motor can be

controlled with help of programming in C language.

3 . Motor Section:

The motor section consist of the three motors like DC, stepper ,Induction

& driver circuit which consists of the motor controlling circuit using ULN

2003.

Here after we will introduce you various hardware components required in the

project.

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3.2 PARALLEL PORT OF PC

3.2.1 Introduction to Parallel Ports

The Parallel Port is the most commonly used port for interfacing home made

projects. This port will allow the input of up to 9 bits or the output of 12 bits at any

one given time, thus requiring minimal external circuitry to implement many simpler

tasks. The port is composed of 4 control lines, 5 status lines and 8 data lines. It's

found commonly on the back of your PC as a D-Type 25 Pin female connector. There

may also be a D-Type 25 pin male connector. This will be a serial RS-232 port and

thus, is a totally incompatible port.

Newer Parallel Ports are standardized under the IEEE 1284 standard first released in

1994. This standard defines 5 modes of operation which are as follows,

1. Compatibility Mode.

2. Nibble Mode. (Protocol not Described in this Document)

3. Byte Mode. (Protocol not Described in this Document)

4. EPP Mode (Enhanced Parallel Port).

5. ECP Mode (Extended Capabilities Port).

The aim was to design new drivers and devices which were compatible with each

other and also backwards compatible with the Standard Parallel Port (SPP).

Compatibility, Nibble & Byte modes use just the standard hardware available on the

original Parallel Port cards while EPP & ECP modes require additional hardware

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which can run at faster speeds, while still being downwards compatible with the

Standard Parallel Port. Compatibility mode or "Centronics Mode" as it is commonly

known can only send data in the forward direction at a typical speed of 50 Kbytes per

second but can be as high as 150+ Kbytes a second. In order to receive data, you must

change the mode to either Nibble or Byte mode. Nibble mode can input a nibble (4

bits) in the reverse direction.

e.g. from device to computer.

Byte mode uses the Parallel's bi-directional feature (found only on some cards) to

input a byte (8 bits) of data in the reverse direction. Extended and Enhanced Parallel

Ports use additional hardware to generate and manage handshaking. To output a byte

to a printer (or anything in that matter) using compatibility mode, the software must:

Write the byte to the Data Port.

Check to see is the printer is busy. If the printer is busy, it will not accept any

data, thus any data which is written will be lost.

Take the Strobe (Pin 1) low. This tells the printer that there is the correct data on the

data lines. (Pins 2-9)

Put the strobe high again after waiting approximately 5 microseconds after putting

the strobe low. (Step 3)

This limits the speed at which the port can run at. The EPP & ECP ports get around

this by letting the hardware check to see if the printer is busy and generate a strobe

and /or appropriate handshaking. This means only one I/O instruction need to be

performed, thus increasing the speed. These ports can output at around 1-2 megabytes

per second. The ECP port also has the advantage of using DMA channels and FIFO

buffers, thus data can be shifted around without using I/O instructions.

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3.2.2 Hardware Properties

On the next page is a table of the "Pin Outs" of the D-Type 25 Pin connector and the

Centronics 34 Pin connector. The D-Type 25 pin connector is the most common

connector found on the Parallel Port of the computer, while the Centronics Connector

is commonly found on printers. The IEEE 1284 standard however specifies 3 different

connectors for use with the Parallel Port. The first one, 1284 Type A is the D-Type 25

connector found on the back of most computers. The 2nd is the 1284 Type B which is

the 36 pin Centronics Connector found on most printers. IEEE 1284 Type C however,

is a 36 conductor connector like the Centronics, but smaller. This connector is

claimed to have a better clip latch, better electrical properties and is easier to

assemble. It also contains two more pins for signals which can be used to see whether

the other device connected, has power. 1284 Type C connectors are recommended for

new designs, so we can look forward on seeing these new connectors in the near

future.

Fig 6 D-25 Male Connector

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Fig7 D-25 Female Connector

Fig 8 Parallel Port

Table 8 Pin Assignments of the D-Type 25 pin Parallel Port Connector.

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The above table uses "n" in front of the signal name to denote that the signal is

active low. e.g. nError. If the printer has occurred an error then this line is low. This

line normally is high, should the printer be functioning correctly. The "Hardware

Inverted" means the signal is inverted by the Parallel card's hardware. Such an

example is the Busy line. If +5v (Logic 1) was applied to this pin and the status

register read, it would return back a 0 in Bit 7 of the Status Register.

The output of the Parallel Port is normally TTL logic levels. The voltage

levels are the easy part. The current you can sink and source varies from port to port.

Most Parallel Ports implemented in ASIC, can sink and source around 12mA.

However these are just some of the figures taken from Data sheets, Sink/Source 6mA,

Source 12mA/Sink 20mA, Sink 16mA/Source 4mA, Sink/Source 12mA. As you can

see they vary quite a bit. The best bet is to use a buffer, so the least current is drawn

from the Parallel Port.

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3.2.3 Port addresses

The Parallel Port has three commonly used base addresses. These are listed in

table 2, below. The 3BCh base address was originally introduced used for Parallel

Ports on early Video Cards. This address then disappeared for a while, when Parallel

Ports were later removed from Video Cards. They has now reappeared as an option

for Parallel Ports integrated onto motherboards, upon which their configuration can be

changed using BIOS.

LPT1 is normally assigned base address 378h, while LPT2 is assigned 278h.

However this may not always be the case as explained later. 378h & 278h have

always been commonly used for Parallel Ports. The lower case h denotes that it is in

hexadecimal. These addresses may change from machine to machine.

Table 3.2: Port addresses

The following sample program in C, shows how you can read these locations

to obtain the addresses of your printer ports.

#include

#include

void main(void)

{

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unsigned int far *ptraddr; /* Pointer to location of Port Addresses */

unsigned int address; /* Address of Port */

int a;

ptraddr=(unsigned int far *)0x00000408;

for (a = 0; a < 3; a++)

{

address = *ptraddr;

if (address == 0)

printf("No port found for LPT%d \n",a+1);

else

printf("Address assigned to LPT%d is %Xh\n",a+1,address);

*ptraddr++;

}

}

The table below shows the register addresses of LPT1 & LPT2

Table 3.3: Register addresses of LPT1 & LPT2

Register LPT1 LPT2

Data register (Base address+0) 0x378 0x278

Status register (Base address+0) 0x379 0x279

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Control register (Base address+0) 0x37a 0x27a

The flowchart for program on PC using C language is as follows.

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Fig 9 Flowchart for program on PC

3.3 SCHMATIC FOR DC MOTOR CONTROL

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3.4 RF TRANSMITTER:

The 212 encoders are a series of CMOS LSIs for remote control system

applications. They are capable of encoding information which consists of N address

bits and 12_N data bits. Each address/ data input can be set to one of the two logic

states. The programmed addresses /data are transmitted together with the header bits

via an RF or an infrared transmission medium upon receipt of a trigger signal. The

capability to select a TE trigger on the HT12E or a DATA trigger on the HT12A

further enhances the application flexibility of the 212 series of encoders. The

HT12A additionally provides a 38 kHz carrier for infrared systems.

Fig 11. Schematic for RF Transmitter with Decoder

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Table 4 Pin Description of RF Transmitter

3.4.1 Operation

The 212 series of encoders begin a 4-word transmission cycle upon receipt of a

transmission enable (TE for the HT12E or D8~D11 for the HT12A, active low). This

cycle will repeat itself as long as the transmission enable (TE or D8~D11) is held low.

Once the transmissions enable returns high the encoder output completes its final

cycle and then stops as shown below.

Fig 12 Transmission Timing for the HT12E

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3.4.2 Information word

If L/MB=1 the device is in the latch mode (for use with the latch type of data

decoders). When the transmission enable is removed during a transmission, the

DOUT pin outputs a complete word and then stops. On the other hand, if L/MB=0 the

device is in the momentary mode (for use with the momentary type of data decoders).

When the transmission enable is removed during a transmission, the DOUT outputs a

complete word and then adds 7 words all with the_1_data code.

An information word consists of 4 periods as illustrated below.

3.4.5 Address/data waveform

Each programmable address/data pin can be externally set to one of the

following two logic states as shown below.

Fig.13 Address /Data bit waveform for the HT12E

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The address/data bits of the HT12A are transmitted with a 38kHz carrier for infrared

remote controller flexibility.

3.4.6 Address/data programming (preset)

The status of each address/data pin can be individually pre-set to logic _high_

or _low_. If a transmission- enable signal is applied, the encoder scans and transmits

the status of the 12 bits of address/ data serially in the order A0 to AD11 for the

HT12E encoder. During information transmission these bits are transmitted with apreceding synchronization bit. If the trigger signal is not applied, the chip enters the

standby mode and consumes a reduced current of less than 1_A for a supply voltage

of 5V.

Usual applications preset the address pins with individual security codes using DIP

switches or PCB wiring, while the data is selected by push buttons or electronic

switches.

3.4.6 Address/Data sequence

The following provides the address/data sequence table for various models of

the 212 series of encoders. The correct device should be selected according to the

individual address and data requirements.

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3.5 RF RECEIVER:

The 2 ^12 decoders are a series of CMOS LSIs for remote control

system applications. They are paired with Holtek_s 2 ^12 series of encoders for

proper operation, a pair of encoder/decoder with the same number of addresses and

data format should be chosen. The decoders receive serial addresses and data from a

programmed 2 ^12 series of encoders that are transmitted by a carrier using an RF or

an IR transmission medium. They compare the serial input data three times

continuously 2^12 with their local addresses. If no error or unmatched codes are

found, the input data codes are decoded and then transferred to the output pins.

The VT pin also goes high to indicate a valid transmission. The 2 12 series of

decoders are capable of decoding information that consist of N bits of address and

12_N bits of data. Of this series, the HT12D is arranged to provide 8 address bits and

4 data bits, and HT12F is used to decode 12 bits of address information.

Fig.14 RF Receiver

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3.5.1 Operation

The 212 series of decoders provides various combinations of addresses and data pins

in different packages so as to pair with the 2 12 series of encoders. The decoders

receive data that are transmitted by an encoder and interpret the first N bits of code

period as addresses and the last 12_N bits as data, where N is the address code

number. A signal on the DIN pin activates the oscillator which in turn decodes the

incoming address and data. The decoders will then check the received address three

times continuously. If the

received address codes all match the contents of the decoder_s local address, the

12_N bits of data are decoded to activate the output pins and the VT pin is set high to

indicate a valid transmission. This will last unless the address code is incorrect or no

signal is received. The output of the VT pin is high only when the transmission is

valid. Otherwise it is always low.

3.5.2 Output type

Of the 2 12 series of decoders, the HT12F has no data output pin but its VT pin can

be used as a omentary data output. The HT12D, on the other hand, provides 4 latch

type data pins whose data remain unchanged until new data are received.

3.5.3 Flowchart

The oscillator is disabled in the standby state and activated when a logic _high_ signalapplies to the DIN pin. That is to say, the DIN should be kept low if there is no signal

input.

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3.6 4:16 DECODER

IC 74154 is a 4-16 line decoder, it takes the 4 line BCD input and selectsrespective output one among the 16 output lines. It is active low output IC so when

any output line is selected it is indicated by active low signal, rest of the output lineswill remain active high. This 4-line-to-16-line decoder utilizes TTL circuitry to

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decode four binary-coded inputs into one of sixteen mutually exclusive outputs when

both the strobe

Fig:15 IC 74154 Line decoder pin configuration

inputs, G1 and G2, are low. The demultiplexing function is performed by using the 4

input lines to address the output line, passing data from one of the strobe inputs with

the other strobe input low. When either strobe input is high, all outputs are high. This

demultiplexer is ideally suited for implementing high-performance memory decoders.

Table 3.5: Truth table of IC 74154

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3.7 Power Supply:

Fig .16 Block Diagram of Power Supply Design

For providing the operating voltage of various ICs that is used in various circuit a

power supply which gives the voltage 5 V, 9V, 12V & variable power supply is

54

Step-down

Transformer

Three

terminals

Voltage

Filter

Circuit

Rectifier


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designed. For that purpose we use the step down transformer 230/12V, 1A rating. A

rectifier is used for the converting a.c. supply into d.c. A bridge IC is used for that

purpose.

Fig 17 Schematic of power supply

4. MOTOR CONTROL :

4.1 STEPPER MOTOR:

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A stepper motor is a brushless, synchronous electrical motor that can divide a full

rotation into a large number of steps, for example, 200 steps. Thus the motor can be

turned to a precise angle.

a. Single-Coil Excitation - Each successive coil is energized in turn.

Step Coil 4 Coil 3 Coil 2 Coil 1

a.1 on off off off

a.2 off on off off

a.3 off off on off

a.4 off off off on

Table 6 Single Coil Excitation

b. Two-Coil Excitation - Each successive pair of adjacent coils is energized in turn.

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Step Coil 4 Coil 3 Coil 2 Coil 1

b.1 on on off off

b.2 off on on off

b.3 off off on on

b.4 on off off on

Table 7 Two Coil Excitation

4.1.1 Programme for Stepper motor control:

When (1)D is send to the output port ,then at the input of the driver IC ULN 2003 a

data bit [ 0 0 0 1]B .similarly a required data bit obtained at the input of ULN by

sending [1,2,4,8] to the out port.& for anticlockwise rotation above data send in

reverse order.

(Sample programme for clockwise rotation)

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#include

#include

#include

void main()

{

int b, c;

int a[4]={1,2,4,8}

while(!kbhit())

{

for(b=0;b


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4.2 DC MOTOR CONTROL :

4.1 PC interfacing of DC motor :

By using the SPDT relay we can control the direction of the rotation of the DC motor.The triggering of relay controlled by the C programming through ULN2003.The

motor is connected to the common terminal of the relay. A diode is used for the

protection of the relay coil. The positive terminal of the supply is connected to the NO

of the relay.

When the [ 0 ,1]b send to the input of the ULN 2003 at the pin 1,2 resp. then

the relay 1 is getting triggered ,therefore the motor is rotating in the clockwise

direction . If the [ 1, 0] b send at input the motor is rotating in the anticlockwise

direction.

Fig 18 DC motor control

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4.2 Sample programme for clockwise & anticlockwise rotation ( When parallel

port directly connected to the ULN 2003.)

#include

#include

#include

void main()

{

int a;

printf( \n Enter your choice \n 1 . Clockwise \n 2. Anticlockwise );

scanf(%d,&a);

if (a=1)

{

outport(0x378,0);

Printf ("\nMotor is rotating clockwise);

} .else

{

Outport (0x379,1);

Printf ("\nMotor is rotating clockwise);

}

getch();

}

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5.CONCLUSION

The field of industrial automation is expanding rapidly as electronic

technologies converge. The industrial environment now encompasses

communications, security, convenience and information systems. Wireless

communication is expected to be a key technology for the industrial automation

market, since it significantly reduces system installation cost. In several cases, the use

of RF-signals is highly desirable or necessary due to the ability to penetrate walls and

ceilings.

Automation lowers production cost by reducing the labor requirement,

decreasing wastage, and permitting faster, more efficient volume production. It also

generally reduces the number of machines in a plant, this will provide saving in labor

and maintenance costs. The automation system shows none of the human

characteristics of fatigue, mood changes, or inconsistent judgment. So, this provides

accurate and repeatable batches. Therefore, automation can create higher efficiency

and reduce overall cost in addition to increase in productivity.

5.1 PC CONTROLLED MOTOR APPLICATION:

Computer-controlled stepper motors are one of the most versatile forms of positioning

systems, particularly when digitally controlled as part of a servo system. Stepper

motors are used in floppy disk drives, flatbed scanners, printers, plotters and many

more devices. Note that hard drives no longer use stepper motors to position the

read/write heads, instead utilizing a voice coil and servo feedback for head

positioning.

Stepper motors can also be used for positioning of valve pilot stages, for fluid control

systems.

Computer-controlled motor are used in robots are programmed to perform

many operations in manufacturing. Modern robot has an ability of special gripping

capabilities, sensors, vision, and sophisticated information management systems. It

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can pick, place, transport, and orient similar to a human arm, but with greater power,

precision, and repeatability.

Motor are employed in a wide assortment of applications in industry. Today

most of the applications are in manufacturing to move materials and tools of various

types..

The wireless control of motor is required when the motor is placed at the remote

locations, where it is very difficult to access the motor. By using this system we can

control the motor up to 3 h.p. When the precise rotation of stepper motor is required

then we can use stepper motor controlled through PC.

5.2 FUTURE SCOPE

The project has its own limitations that it cannot be operated out of the range

of RF communication. This limitation can be overcome by controlling the same motor

using telephone lines. It means it can be used from any distance from meters to

thousand kilometers using a simple telephone line or mobile phone.Using a telephone

as a media, which serves main part of this system, by using home phone as a local

phone and another phone, either landline or mobile phone as a remote phone. The

same project can be extended to interface with telephone line.

Using feedback the environment of the actual work station can be observed

over remote control section. For this purpose interfacing of digital camera with robot

is required.

Documents

Automation 11