ABSTACT

The main aim of Minor project is to expose the student to the industrial technical problems to which he is to be exposed in the future life. In an organization where Making Things Right in the first instance is the driving motto, perfection and accuracy are inevitable.

I have worked for six months on the topic entitled “MATERIAL SEPRATION”. I have the honor to work as a student of DEV POLYTECHNIC to the extent of my technical capabilities. Doing this tenure, I have acquired a sufficient knowledge on construction and assembly of conveyor system for material sepration.

I remained actively associated with one of the most demanding field of mechanical. The time spent on the aforesaid topic has really proved to be very useful and will remain enduring throughout my professional career. Brief outline of the work is covered under the following heads.We would like to express our gratitude to Mr. Ashish Goyal (H.O.D. ME Deptt), who motivated us and helped us in every step of our project workWe would also like to thanks all the faculty of Mechanical Department who contributed directly or indirectly towards the completion of the project.

OVERVIEW OF CONVEYOR SYSTEM

DC GEARED MOTORS

BASICS OF SENSORS

ABOUT METAL DETECTOR

RESULT & MODIFICATIONS

SUGGESTION FOR FUTURE MODIFICATION AND FUTURE SCOPE OF PROJECT

In conclusion, I must say that the Minor project has helped me to enhance my working

skills & stamina and to further enlighten me to enter a new phase of life after completion

of the degree program.

TABLE OF CONTENTS

  Content Chapter No. Name

1 Introduction1.1 Walking kinematic project1.2 Overview of design

2 Designing of machine2.1 Designing 2.2 Feature

2.3 Mechanical designing

2.4 Prototype development

2.5 Material selection

2.6 Manufacturing

2.7 Future scope

2.8 General Dimension

2.9 Mechnical part specification

3. DC motor and their drive

4. Switches

  4 Reference  5 Appendix- Data Sheets

CHAPTER 1

1. INTRODUCTION

CHAPTER-2: Linear Actuator

INTRODUCTION:

A linear actuator is a device that applies force in a linear manner, as opposed to rotationally like an electric motor. There are various methods of achieving this linear motion. Some actually convert rotational motion into linear motion.

FIG : Conceptual design of a basic linear actuator

The linear actuator used in our project is completely mechanical design with ball screw arrangement.

BASIC WORKING OF OUR LINEAR ACTUATOR:

There is a motor mount at the beginning of the linear actuator. It is this motor that is used to slide the moving block up and down in the linear actuator. The design of the actuator is so made that when the motor moves in clockwise direction with one polarity at the ends, it turns the moving block slide that is mounted on the rotating screw . This gives forward motion to the actuator. Again, reversing the polarity on the motor would reverse the direction of rotation of motor tht is turns it to rotate in anticlockwise direction so that the screw also revolves in anticlockwise direction ,this

makes the sliding block move back on the same rotaing screw. Thus, with the help of rotatory motion, we are getting vertical up and down motion.

TYPES OF LINEAR ACTUATORS:

1. Mechanical actuators

FIG. A mechanical linear actuator with digital readout.

Mechanical actuators typically convert rotary motion of a control knob or handle into linear displacement via screws and/or gears to which the knob or handle is attached. A jackscrew or car jack is a familiar mechanical actuator. Another family of actuators are based on the segmented spindle. Rotation of the jack handle is converted mechanically into the linear motion of the jack head. Mechanical actuators are also frequently used in the field of lasers and optics to manipulate the position of linear stages, rotary stages, mirror mounts, goniometers and other positioning instruments. For accurate and repeatable positioning, index marks may be used on control knobs. Some actuators even include an encoder and digital position readout.  These are similar to the adjustment knobs used on micrometers except that their purpose is position adjustment rather than position measurement.

2. Hydraulic actuators

Hydraulic actuators or hydraulic cylinders typically involve a hollow cylinder having a piston inserted in it. The two sides of the piston are alternately pressurized/de-pressurized to achieve controlled precise linear displacement of the piston and in turn the entity connected to the piston. The physical linear displacement is only along the axis of the piston/cylinder.

This design is based on the principles of hydraulics. A familiar example of a manually operated hydraulic actuator is a hydraulic car jack. Typically though, the term "hydraulic actuator" refers to a device controlled by a hydraulic pump.

3. Piezoelectric actuators

The piezoelectric effect is a property of certain materials in which application of a voltage to the material causes it to expand. Very high voltages correspond to only tiny expansions. As a result, piezoelectric actuators can achieve extremely fine positioning resolution, but also have a very short range of motion. In addition, piezoelectric materials exhibit hysteresis which makes it difficult to control their expansion in a repeatable manner.

4. Electro-mechanical actuators

A miniature electro-mechanical linear actuator where the lead nut is part of the motor. The lead screw does not rotate, so as the lead nut is rotated by the motor, the lead screw is extended or retracted.

Typical compact cylindrical linear electric actuator

Typical linear or rotary + linear electric actuator

Moving coil linear, rotary and linear + rotary actuators at work in various applications

Electro-mechanical actuators are similar to mechanical actuators except that the control knob or handle is replaced with an electric motor. Rotary motion of the motor is converted to linear displacement of the actuator. There are many designs of modern linear actuators and every company that manufactures them tends to have their own proprietary method. The following is a generalized description of a very simple electro-mechanical linear actuator.

Simplified design

Typically, a rotary driver (e.g. electric motor) is mechanically connected to a lead screw so that the rotation of the electric motor will make the lead screw rotate. A lead screw has a continuous helical thread machined on its circumference running along the length (similar to the thread on a bolt). Threaded onto the lead screw is a lead nut with corresponding helical threads. The nut is prevented from rotating with the lead screw (typically the

nut interlocks with a non-rotating part of the actuator body). Therefore, when the lead screw is rotated, the nut will be driven along the threads. The direction of motion of the nut will depend on the direction of rotation of the lead screw. By connecting linkages to the nut, the motion can be converted to usable linear displacement. Most current actuators are built either for high speed, high force, or a compromise between the two. When considering an actuator for a particular application, the most important specifications are typically travel, speed, force, accuracy, and lifetime.

There are many types of motors that can be used in a linear actuator system. These include dc brush, dc brushless, stepper, or in some cases, even induction motors. It all depends on the application requirements and the loads the actuator is designed to move. For example, a linear actuator using an integral horsepower AC induction motor driving a lead screw can be used to actuate a large valve in a refinery. In this case, accuracy and move resolution down to a thousanth isn't needed, but high force and speed is. For electromechanical linear actuators used in laboratory instrumentation robotics, optical and laser equipment, or X-Y tables, fine resolution into the micron region and high accuracy may require the use of a fractional horsepower stepper motor linear actuator with a fine pitch lead screw. There are many variations in the electromechanical linear actuator system. It's critical to understand the design requirements and application constraints to know which one would be best.

Principles

In the majority of linear actuator designs, the basic principle of operation is that of an inclined plane. The threads of a lead screw act as a continuous ramp that allows a small rotational force to be used over a long distance to accomplish movement of a large load over a short distance.

Variations

Many variations on the basic design have been created. Most focus on providing general improvements such as a higher mechanical efficiency, speed, or load capacity. There is also a large engineering movement towards actuator miniaturization.

Most electro-mechanical designs incorporate a lead screw and lead nut. Some use a ball screw and ball nut. In either case the screw may be connected to a motor or manual control knob either directly or through a series of gears. Gears are typically used to allow a smaller (and weaker) motor spinning at a higher rpm to be geared down to provide the torque necessary to spin the screw under a heavier load than the motor would otherwise be capable of driving directly. Effectively this sacrifices actuator speed in favor of increased actuator thrust. In some applications the use of worm gear is common as this allow a smaller built in dimension still allowing great travel length.

Some lead screws have multiple "starts". This means that they have multiple threads alternating on the same shaft. One way of visualizing this is in comparison to the multiple color stripes on a candy cane. This allows for more adjustment between thread pitch and nut/screw thread contact area, which determines the extension speed and load carrying capacity (of the threads), respectively.

Linear motors

A linear motor is essentially a rotary electric motor laid down on flat surface. Since the motor moves in a linear fashion to begin with, no lead screw is needed to convert rotary motion to linear. While high capacity is possible, the material and/or motor limitations on most designs are surpassed relatively quickly. Most linear motors have a low load capacity compared to other types of linear actuators.

Wax motors

A wax motor typically uses an electric current to heat a block of wax causing it to expand. A plunger that bears on the wax is thus forced to move in a linear fashion.

Segmented spindles

Segmented actuators consist of discrete chain elements which are interlinked to form a rod (the technology is known as the segmented spindle) thus making the actuator extremely compact.

Advantages and disadvantages of different types of linear actuators:

Actuator Type Advantages Disadvantages

MechanicalCheap. Repeatable. No power source required. Self contained. Identical behaviour extending or retracting.

Manual operation only. No automation.

Electro-mechanical

Cheap. Repeatable. Operation can be automated. Self contained. Identical behaviour extending or retracting. DC or Stepping motors. Position feedback possible.

Many moving parts prone to wear.

Linear motorSimple design. Minimum of moving parts. High speeds possible. Self contained. Identical behaviour extending or retracting.

Low force.

Piezoelectric Very small motions possible.

Requires position feedback to be repeatable. Short travel. Low speed. High voltages required. Expensive. Good in compression only. Not good in tension.

Hydraulic Very high forces possible.Can leak. Requires position feedback for repeatability. External hydraulics pump required. Some designs good in compression only.

Wax motor Smooth operation. Not as reliable as other methods.

Segmented spindleVery compact. Range of motion greater than length of actuator.

Both linear and rotary motion.

Moving coil

Force, position and speed are controllable and repeatable. Capable of high speeds and precise positioning. Linear, rotary, and linear + rotary actions possible.

Requires position feedback to be repeatable.

MICA (moving iron controllable actuator)

High force and controllable. Higher force and less losses than moving coils [2]. Losses easy to dissipate. Electronic driver easy to design and set up.

Stroke limited to several millimeters, less linearity than moving coils

LINEAR ACTUATOR WITH BALL SCREW ARRANGEMENT IN EDM:

It works on the principle of conversion of rotator motion into linear motion.

The rotatory motion is achieved through the motor and linear motion through a

ball-screw arrangement.

It is supported by a base plate of alluminium and is provided with a moving plate o

which the robotic gripper is mounted in order to pick the objects from a lower

position and place it in higher position.

Linear actuator applications

Linear motion is much in demand in all sectors of industry and the linear actuator is one of the responses. The linear actuator is generally less cumbersome than a cogged belt, simpler than a rack and pinion and more economical. It has a number of major advantages for the user: * Smaller size* Reliability* Longer life* Performance (power + speed)* Cost Below are some applications into which our linear actuators have been applied:

Linear actuator with integrated electronics New developments launched in recent years have led to many improvements in terms of power, speed and reliability. But without doubt what has contributed most to improved operation is integration of the control electronics into the design of the linear actuator. The unit in this picture is the 8623-R002. The datasheet for this linear actuator can be seen on the right hand side of this web page.

Medical application This actuator is based on a stepping motor with a pernament magnet and fits perfectly into the customer's assembly. it has a leakproof housing and is non-sensitive to outside conditions.

Laboratory application Automated dosage in laboratories is developing as the instruments achieve greater accuracy and efficiency. The optimized resolution of the 7214 actuator provides constant and precise movement, even at high speed.

Heating, ventilation and air conditioning This actuator is the drive system for a 3-way valve for a gas boiler. The actuator moves a valve which switches the hot water circuit to the water or heating position.

Automotive application The environment in a car engine places severe demands on the components - vibration, temperature variations, thermal shock and an aggresive chemical atmosphere - and yet the job of the linear actuator that regulates the by-pass deceleration requires high precision. It is clipped directly onto the butterfly valve to avoid using fixing screws.

CHAPTER-3

METAL DETECTOR

A metal detector is a device which responds to metal that may not be readily apparent.

Metal detectors have been a part of every country’s defence, security and military

operations for a long time. Along with its wide applications in industrial entry doors, it

could be used even in mines to detect the presence of metals. In defence, detection of any

pistol / bomb, electronic survelliance equipment hidden in a person’s body could be

detected with its help.

There are many types of configurations in which a metal detector could be designed and

installed. Most widely used are: Walk through Metal Detectors installed in company’s

entry doors to scan the incoming person for any unidentified hidden metal objects and

second category is Hand Held Metal Detector that is mostly used in external metal

identification and detection purposes such as in military and defense or to personally

check a person or his bag / luggage to detect for hidden metals.

The basic designing of a Metal Detector is based upon the principle that inductance of a

coil is changed when metal comes close to the coil. This is basically a type of an open

transformer. As a transformer has an enamled insulated copper metallic wire coil inside

it, similarly we would work on creating a copper thick wire (enameled) or PVC Copper

Wire and make an insulated coil out of it.

There would be an air core in the center of the coil. When a metal would pass out of this

coil, inductance of the coil would change and hence coil impedence would change. And

as the voltage and frequency of the coil would be maintained constant from external

triggering circuit, impedence is inversely proportional to change in current and hence this

change is detected and analog to digital converted circuitry and fed to a microcontroller

8051. So, whenever a person crosses the door, this system would detect the person for

any hidden metal, this walk through metal detector would show it on an LCD along with

an alarming buzzer.

A portable and handy design would be made containing copper coil and an air core to

demonstrate the working of the complete project.

LIST OF COMPONENTS TO BE USED

S.NO Name Quantity Colour Pins

1 Copper Wires 8 meters long

Black Single

core wire

2 Insulating Telescopic Pipes (optional)

2 Black -

3 Op-amp LM358 (IC) 2 Black 8

4 NE555 TIMER IC 3 Black 8

5 Microcontroller 8051 1 Black 40

6 IR sensor (Transmitter) 1 Light blue 2

7 IR sensor (Receiver) 2 Transparent 2

8 Resistance 330 ohm 3 Orange-orange-brown 2

9 Resistance 1 mega ohm 2 Green-brown 2

10 Not gate ( 7404) 1 Black 14

11 Designed PCB 4 -

12 Transistors PNP BC547 9 Black 3

13 2 x 16 LCD Module 1 - 16

14 Nut-Bolt Pair 1 -

15 Jumper Wire ( Single Stand Wire)

-

16. IC Base ( 8,14,16,40 pin) 3 Black -

17. Battery ( 9v) + Connector 1 -

18. Step down transformer ( 9-0-9) 1 -

19. Bridge diode ( 1 amp ) 1 Black 4

20. Voltage regulator 7805 1 Black 3

21. Led + 100 ohm ( indicator) 1 -

22. 10k ohm resistance 1 -

23. 10 microfarad capacitor 1 -

24. 33 picofarad capacitor 1 2

25. Crystal 11.0592 Mhz 1 2

26. Sip resistance ( 10 k ohm) 1 Black 9

27. Ribbon wires

28. General purpose PCB 1

29. Buzzer 1 Black 2

30. Potentiometer 10K 2 Blue 3

BLOCK DIAGRAM

Copper Coil(For metal detection)

220 volt ACUse of 220v AC is optional if we are using Battery operated device

Anatomy of a Metal Detector

A typical metal detector is light-weight and consists of just a few parts:

1. Stabilizer (optional) - used to keep the unit steady as you sweep it back and

forth

5 volt regulated power supply Using

Voltage regulatorFilter capacitor Or Battery

Main processing unitMicrocontroller 8-bit

AT89c52

LCD FOR DISPLAY of

metal detection

ULN 2003 Amplifier

LED for INDICATION

Opamp LM358

Reference Potentiometer

Transistor as an Amplifier

Alarming Buzzer (on remote location

on identifying Hidden Metal)

2. Control box - contains the circuitry, controls, speaker, batteries and

the microcontroller

3. Shaft - connects the control box and the coil; often adjustable so you can set it

at a comfortable level for your height

4. Search coil - the part that actually senses the metal; also known as the "search

head," "loop" or "antenna"

Most systems also have a jack for connecting headphones, and some have the control

box below the shaft and a small display unit above.

Operating a metal detector is simple. Once you turn the unit on, you move slowly over

the area you wish to search. In most cases, you sweep the coil (search head) back and

forth over the ground in front of you. When you pass it over a target object, an audible

signal occurs. More advanced metal detectors provide displays that pinpoint the type of

metal it has detected and how deep in the ground the target object is located.

Metal detectors use one of three technologies:

Very low frequency (VLF)

Pulse induction (PI)

Beat-frequency oscillation (BFO)

VLF Technology

Very low frequency (VLF), also known as induction balance, is probably the most

popular detector technology in use today. In a VLF metal detector, there are two distinct

coils:

Transmitter coil - This is the outer coil loop. Within it is a coil of wire.

Electricity is sent along this wire, first in one direction and then in the other,

thousands of times each second. The number of times that the current's

direction switches each second establishes the frequency of the unit.

Receiver coil - This inner coil loop contains another coil of wire. This wire

acts as an antenna to pick up and amplify frequencies coming from target

objects in the ground.

This LandRanger metal detector from Bounty Hunter uses

VLF

The current moving through the transmitter coil creates an electromagnetic field, which is

like what happens in an electric motor. The polarity of the magnetic field is perpendicular

to the coil of wire. Each time the current changes direction, the polarity of the magnetic

field changes. This means that if the coil of wire is parallel to the ground, the magnetic

field is constantly pushing down into the ground and then pulling back out of it.

As the magnetic field pulses back and forth into the ground, it interacts with any

conductive objects it encounters, causing them to generate weak magnetic fields of their

own. The polarity of the object's magnetic field is directly opposite the transmitter coil's

magnetic field. If the transmitter coil's field is pulsing downward, the object's field is

pulsing upward.

The receiver coil is completely shielded from the magnetic field generated by the transmitter coil.

However, it is not shielded from magnetic fields coming from objects in the ground. Therefore, when

the receiver coil passes over an object giving off a magnetic field, a small electric current travels

through the coil. This current oscillates at the same frequency as the object's magnetic field. The coil

amplifies the frequency and sends it to the control box of the metal detector, where sensors analyze the

signal.

The metal detector can determine approximately how deep the object is buried based on the strength of

the magnetic field it generates. The closer to the surface an object is, the stronger the magnetic field

picked up by the receiver coil and the stronger the electric current generated. The farther below the

surface, the weaker the field. Beyond a certain depth, the object's field is so weak at the surface that it

is undetectable by the receiver coil.

VLF Phase Shifting

How does a VLF metal detector distinguish between different metals? It relies on a

phenomenon known as phase shifting. Phase shift is the difference in timing between the

transmitter coil's frequency and the frequency of the target object. This discrepancy can

result from a couple of things:

Inductance - An object that conducts electricity easily (is inductive) is slow

to react to changes in the current. You can think of inductance as a deep

river: Change the amount of water flowing into the river and it takes some

time before you see a difference.

Resistance - An object that does not conduct electricity easily (is resistive) is

quick to react to changes in the current. Using our water analogy, resistance

would be a small, shallow stream: Change the amount of water flowing into

the stream and you notice a drop in the water level very quickly.

Basically, this means that an object with high inductance is going to have a larger phase

shift, because it takes longer to alter its magnetic field. An object with high resistance is

going to have a smaller phase shift.

Phase shift provides VLF-based metal detectors with a capability called discrimination.

Since most metals vary in both inductance and resistance, a VLF metal detector examines

the amount of phase shift, using a pair of electronic circuits called phase demodulators,

and compares it with the average for a particular type of metal. The detector then notifies

you with an audible tone or visual indicator as to what range of metals the object is likely

to be in.

Many metal detectors even allow you to filter out (discriminate) objects above a certain

phase-shift level. Usually, you can set the level of phase shift that is filtered, generally by

adjusting a knob that increases or decreases the threshold. Another discrimination feature

of VLF detectors is called notching. Essentially, a notch is a discrimination filter for a

particular segment of phase shift. The detector will not only alert you to objects above

this segment, as normal discrimination would, but also to objects below it.

Advanced detectors even allow you to program multiple notches. For example, you could

set the detector to disregard objects that have a phase shift comparable to a soda-can tab

or a small nail. The disadvantage of discrimination and notching is that many valuable

items might be filtered out because their phase shift is similar to that of "junk." But, if

you know that you are looking for a specific type of object, these features can be

extremely useful.

PI Technology

A less common form of metal detector is based on pulse induction (PI). Unlike VLF, PI

systems may use a single coil as both transmitter and receiver, or they may have two or

even three coils working together. This technology sends powerful, short bursts (pulses)

of current through a coil of wire. Each pulse generates a brief magnetic field. When the

pulse ends, the magnetic field reverses polarity and collapses very suddenly, resulting in

a sharp electrical spike. This spike lasts a few microseconds (millionths of a second) and

causes another current to run through the coil. This current is called the reflected

pulse and is extremely short, lasting only about 30 microseconds. Another pulse is then

sent and the process repeats. A typical PI-based metal detector sends about 100 pulses per

second, but the number can vary greatly based on the manufacturer and model, ranging

from a couple of dozen pulses per second to over a thousand.

This Garrett metal detector uses pulse induction.

If the metal detector is over a metal object, the pulse creates an opposite magnetic field in

the object. When the pulse's magnetic field collapses, causing the reflected pulse, the

magnetic field of the object makes it take longer for the reflected pulse to completely

disappear. This process works something like echoes: If you yell in a room with only a

few hard surfaces, you probably hear only a very brief echo, or you may not hear one at

all; but if you yell in a room with a lot of hard surfaces, the echo lasts longer. In a PI

metal detector, the magnetic fields from target objects add their "echo" to the reflected

pulse, making it last a fraction longer than it would without them.

A sampling circuit in the metal detector is set to monitor the length of the reflected

pulse. By comparing it to the expected length, the circuit can determine if another

magnetic field has caused the reflected pulse to take longer to decay. If the decay of the

reflected pulse takes more than a few microseconds longer than normal, there is probably

a metal object interfering with it.

The sampling circuit sends the tiny, weak signals that it monitors to a device call an integrator. The

integrator reads the signals from the sampling circuit, amplifying and converting them to direct current

(DC). The direct current's voltage is connected to an audio circuit, where it is changed into a tone that

the metal detector uses to indicate that a target object has been found.

PI-based detectors are not very good at discrimination because the reflected pulse lengths of various

metals are not easily separated. However, they are useful in many situations in which VLF-based metal

detectors would have difficulty, such as in areas that have highly conductive material in the soil or

general environment. A good example of such a situation is salt-water exploration. Also, PI-based

systems can often detect metal much deeper in the ground than other systems.

BFO Technology

The most basic way to detect metal uses a technology called beat-frequency

oscillator (BFO). In a BFO system, there are two coils of wire. One large coil is in the

search head, and a smaller coil is located inside the control box. Each coil is connected to

an oscillator that generates thousands of pulses of current per second. The frequency of

these pulses is slightly offset between the two coils.

As the pulses travel through each coil, the coil generates radio waves. A tiny receiver

within the control box picks up the radio waves and creates an audible series of tones

(beats) based on the difference between the frequencies.

If the coil in the search head passes over a metal object, the magnetic field caused by the

current flowing through the coil creates a magnetic field around the object. The object's

magnetic field interferes with the frequency of the radio waves generated by the search-

head coil. As the frequency deviates from the frequency of the coil in the control box, the

audible beats change in duration and tone. The simplicity of BFO-based systems allows

them to be manufactured and sold for a very low cost.  But these detectors do not provide

the level of control and accuracy provided by VLF or PI systems.

CHAPTER-4

DC Motor , actuator & Their Drives

DC MOTORS

DC motor has two leads. If we apply +ve to one lead and ground

to another motor will rotate in one direction, if we reverse the

connection the motor will rotate in opposite direction. If we keep both

leads open or both leads ground it will not rotate (but some inertia will

be there). If we apply +ve voltage to both leads then braking will

occurs. The main things about a DC motor are Voltage rating, current

rating, Torque, Speed. Torque is inversely proportional to speed. So

we had to get a good torque rather than speed. So, to get maximum

torque we should use gear motors or gearbox.

Normally available DC motors (without gears) have 12V,

250mA, 2400rpm (may change) ratings. But it is better to have a

geared motor, because you should make gears to get a good torque to

drive robot. As a beginner we mostly use DC motors, stepper motor

and servo motor will come later. You can test this, first without

applying any voltage you rotate the shaft of the motor, then apply

ground on both lead and try to rotate the shaft. Both will almost

remain same, but if we apply both lead +ve voltage (+12V) and try to

rotate the shaft, you can feel the difference between the previous one.

You have to apply more force to rotate the same rotation in previous

connection. So we take this condition as braking, because if we want

to stop the motor suddenly then this is the better way which is easily

possible. There are methods to brake motor fastly, like shorting two

leads, applying negative polarity exists, but we won't use this in

robotics.

Normally we get Speed/9 reduction gears to reduce speed and

get a good torque. Put three gears to reduce speed to 2400/27

(calculation is taken avoiding gear loss). So we get a speed of 80 rpm.

I used DC geared motor of 12V, 250mA, 60-80rpm, 2kgcms Torque.

So as a beginner it is better to have a geared motor than a normal

motor because you have to make gears.

Ultra flat dimensions.

Extremely low current consumption.

Low starting voltage.

Low rotor inertia for extremely fast acceleration and braking.

Extremely light and compact.

Very cost effective.

Precision gearboxes available in all sizes.

A DC motor is designed to run on DC electric power. Two examples of

pure DC designs are Michael Faraday's homopolar motor (which is

uncommon), and the ball bearing motor, which is (so far) a novelty. By far

the most common DC motor types are the brushed and brushless types,

which use internal and external commutation respectively to reverse the

current in the windings in synchronism with rotation.

Permanent-magnet motors

permanent-magnet motor does not have a field winding on the stator

frame, instead relying on permanent magnets to provide the magnetic field

against which the rotor field interacts to produce torque. Compensating

windings in series with the armature may be used on large motors to

improve commutation under load. Because this field is fixed, it cannot be

adjusted for speed control. Permanent-magnet fields (stators) are

convenient in miniature motors to eliminate the power consumption of the

field winding. Most larger DC motors are of the "dynamo" type, which

have stator windings. Historically, permanent magnets could not be made

to retain high flux if they were disassembled; field windings were more

practical to obtain the needed amount of flux. However, large permanent

magnets are costly, as well as dangerous and difficult to assemble; this

favors wound fields for large machines.

To minimize overall weight and size, miniature permanent-magnet motors

may use high energy magnets made with neodymium or other strategic

elements; most such are neodymium-iron-boron alloy. With their higher

flux density, electric machines with high energy permanent magnets are at

least competitive with all optimally designed singly

fed synchronous andinduction electric machines. Miniature motors

resemble the structure in the illustration, except that they have at least three

rotor poles (to ensure starting, regardless of rotor position) and their outer

housing is a steel tube that magnetically links the exteriors of the curved

field magnets.

Brushed DC motors

Workings of a brushed electric motor with a two-pole rotor and permanent-

magnet stator. ("N" and "S" designate polarities on the inside faces of the

magnets; the outside faces have opposite polarities.)

DC motors have AC in a wound rotor also called an armature, with a split

ring commutator, and either a wound or permanent magnet stator. The

commutator and brushes are a long-life rotary switch. The rotor consists of

one or more coils of wire wound around a laminated "soft" ferromagnetic

core on a shaft; an electrical power source feeds the rotor windings through

the commutator and its brushes, temporarily magnetizing the rotor core in a

specific direction. The commutator switches power to the coils as the rotor

turns, keeping the magnetic poles of the rotor from ever fully aligning with

the magnetic poles of the stator field, so that the rotor never stops (like a

compass needle does), but rather keeps rotating as long as power is applied.

Many of the limitations of the classic commutator DC motor are due to the

need for brushes to press against the commutator. This createsfriction.

Sparks are created by the brushes making and breaking circuits through the

rotor coils as the brushes cross the insulating gaps between commutator

sections. Depending on the commutator design, this may include the

brushes shorting together adjacent sections – and hence coil ends –

momentarily while crossing the gaps. Furthermore, the inductance of the

rotor coils causes the voltage across each to rise when its circuit is opened,

increasing the sparking of the brushes. This sparking limits the maximum

speed of the machine, as too-rapid sparking will overheat, erode, or even

melt the commutator. The current density per unit area of the brushes, in

combination with their resistivity, limits the output of the motor. The

making and breaking of electric contact also generates electrical noise;

sparking generates RFI. Brushes eventually wear out and require

replacement, and the commutator itself is subject to wear and maintenance

(on larger motors) or replacement (on small motors). The commutator

assembly on a large motor is a costly element, requiring precision assembly

of many parts. On small motors, the commutator is usually permanently

integrated into the rotor, so replacing it usually requires replacing the whole

rotor.

DC MOTORReduction Gears used: 4Material = MSReduction Gear Ratio = 1: 100

Electrical Specification of Motor

• operating Voltage – 12V Max • No load current - 5 amperes • Load current - 12 amperes• Starting Current –8 amperes• Flux – 2.5 Weber • Coil resistance- 150 ohm • Power = 580 watts •

Mechanical Specification of Motor

• Shaft Diameter = 8 mm• Gears Type = worm wheel gears • Material of Gears = Brass • Mounting Bolt = 13mm• Gear Mounting case = Nylon• Torque - 9 kg/cm

CHAPTER 4RELAY

A relay is an electrically operated switch. Many relays use an electromagnet to operate a

switching mechanism, but other operating principles are also used. Relays find

applications where it is necessary to control a circuit by a low-power signal, or where

several circuits must be controlled by one signal. The first relays were used in long

distance telegraph circuits, repeating the signal coming in from one circuit and re-

transmitting it to another. Relays found extensive use in telephone exchanges and early

computers to perform logical operations. A type of relay that can handle the high power

required to directly drive an electric motor is called a contactor. Solid-state relays control

power circuits with no moving parts, instead using a semiconductor device triggered by

light to perform switching. Relays with calibrated operating characteristics and

sometimes multiple operating coils are used to protect electrical circuits from overload or

You have seen controlling home equipments such as light, fans andEquipments that run on 230V using parallel port of computer or a microcontroller or any other digital IC’s. This is possible through relays. Relay is an electromagnetic device which works on magnetic field. The only difference between a switch and a relay is that switch operates when given a manual input whereas relay on the other hand triggers when given an input electrical signal on its 2 input terminals. Relay is also called an electromagnetic switch. If you apply proper low voltage on one side the metal will get contacted. Following figure shows an SPDT Relay and its terminals.

The voltage is applied on its input terminals V1 and V2 that internally acts as two ends of an inductor coil. ‘C’ is the common terminal and is permanently connected to a contact that is magnetic in nature. When there is no input applied to the input terminals, contact is established between terminals ‘C’ and ‘A’ as shown in the figure above. ‘A’ is normally closed terminal. But when a suitable amount of voltage signal is applied to its input, contact breaks up from ‘A’ and gets attached with ‘B’ that is normally open terminal.Note that either of the input terminals of relay could be taken as a positive or negative terminal as an inductor coil has no polarity. Relays also come in different packages such as SPDT, SPST, SPCO, DPST, DPDT, DPCO with same symbols and connections as shown in the table of “types of switches” in the previous chapter.A simple circuit showing the triggering of relay through a low voltage via transistor is shown below.

Note that it is not necessary to use a transistor to drive a relay, it is used only to detect minute signals and passes ground to the terminal of relay when triggered by input signal. It is used in the configuration of “Transistor as a Switch”. We could also apply direct input to the terminals of relay if it is sufficiently large enough to drive a relay. Other components that could be used to drive a relay are amplifier circuits such as Op-amps as amplifiers (LM741) or current amplifier ULN2003, etc. We would discuss transistors and amplifier IC’s in next coming chapters. The relays mostly available are of 12V,196 ohm relays, if you use D880 transistor for driving it then remember the resistance at the base of the transistor should be around 1Kohm. I will explain this in Transistor section briefly You can hear a sound when the relay got activated.

Checking a relay circuit:

1. First check the relay is good and test whether your relay work with the Vcc you use. So first you connect Vcc and gnd between two ends of the relay. If it is activated you can hear sound. If not see the voltage rating of the relay and increase voltage. This is the most problem occurring with relays. For a 6V, 100ohm relay it required 6.86V to make it work. If Vcc=5v then u can hear a small sound that means that magnetization is not enough.2. See the connections properly because on the other side of the relay you might be using 230V, so be careful when you touching the relay.3. See the voltage of the other circuits and sensors when you connect relay (whether they are getting proper voltages).4. Remember to put the protection diode5. Touch the heat sink of the transistor to see if the transistor is getting heated or any faults.6. See the value of the resistor connected in the base of the transistor. I will explain about it in Transistor section.

Here it is a small relay representation (a diagram of relay i have). The other side of the relay can be 230V or even 5V (no restriction), but we normally get 230V relay, means voltage<=230 (on the 230V side). You can use this in the last stage of a line follower(assume that line follower has more than 2 LDR's), when last sensor go out of the line, you can use relay mechanism to provide Vcc to the other lead of the motor so that motor start to rotate backward.

APPLICATIONS OF RELAYApplication of relays is basically to switch a high voltage or AC voltage device from low voltage. The simplest example of relay in day-to-day life is indicators in your cars. When you press the indicator switch to turn on the lights you can hear the triggering sound of the relay. In robotics, most of the application of relay is in the remote controls for driving the robots or we could say driving a motor through relay that operates on high voltage with small voltage given by switch/ sensor as an input. We would study its detail in the chapter of Motors and Remote in next sections.

CHAPTER 5

BATTERY

Battery is an essential part of robotics, because it is the part that define the

working, power, efficiency of robot.

Using Light weight , more power batteries make robot perform better, but

also increases the cost of battery

An electrical battery is one or more electrochemical cells that convert stored

chemical energy into electrical energy. Since the invention of the first

battery (or "voltaic pile") in 1800 by Alessandro Volta, batteries have

become a common power source for many household and industrial

applications. According to a 2005 estimate, the worldwide battery industry

generates US$48 billion in sales each year,[2] with 6% annual growth.[3]

There are two types of batteries: primary batteries (disposable batteries),

which are designed to be used once and discarded, and secondary

batteries (rechargeable batteries), which are designed to be recharged and

used multiple times. Batteries come in many sizes, from miniature cells used

to power hearing aids and wristwatches to battery banks the size of rooms

that provide standby power for telephone exchanges and computer data

centers.

FUTURE SCOPE

Till now, all hardware integration and control circuit has been developed.

The new system has been tested and it’s working as per designed. The future

is to achieve a special type of gate called “alternating tripod” for its

locomotion [3]. The RecurDyn modeling for this particular type of gate has

been simulated and all results are attached to this report. The new type of

gate further minimizes jerks and gives better control for its locomotion

(because of static stability). The new type of gate can be achieved by

designing an improved control circuit.

REFERENCES

CHAPTER 6

REFERENCES

REFERENCES

1. www.panorma.com

2. www.wikipedia.org

3. www.sciencedirect.org

4. www.tri.com

5. www.datasheets4u.com