CHAPTER 1

POWER SUPPLY UNIT

1.1 Introduction:

Power supplies of electronics devices can be broadly divided into line-frequency

and switching power supplies. The line-frequency supply is usually a relatively simple

design, but it become increasingly bulky and heavy for high-current equipment due to

the need for large mains frequency transformers and head-slinked electronic regulator

circuitry.

Our project power supply unit is designed to provide 5V and 12V dc supply. The

power supply unit consists of step down transformer, bridge rectifier, filter and voltage

regulator.

1.2 Transformer:

In general, the AC line voltage presenting your house wiring is not suitable for

electronic circuits. Most circuit required a considerably lower voltage, while a few

require high voltages. The transformer serves to convert the AC line voltage to a

voltage level more appropriate to the need of the circuit to be powered. At the same

time, the transformer provides electrical isolation between the ac and the circuit being

powered, which is an important safety consideration.

Figure 1.1 Construction of Transformer

1.2.1 Step down transformer:

Step down transformer is a static machine and it transfer the electrical power

from one circuit to another circuit without changing the frequency. In our project we

have used step down transformer to reduce the voltage level from 230V to12V.

Fig .Step down transformer

Step down transformer are designed to reduce electrical voltage. Their primary

voltage is greater than their secondary voltage. They can include features for electrical

isolation, power distribution, and control and instrumentation applications.

Step down transformer are made from two or more coils of insulated wire wound

around a core made of iron. When voltage is applied to one coil (called the primary or

input) it magnetizes the iron core, which induces a voltage in the other coil, (called the

secondary or output). The turns ratio of the two sets of windings determines the of

voltage transformation.

1.3.1 Bridge rectifier:

The rectifier is an electronic device, which converts an alternating current wave

to a pulsating direct current wave form. The bridge rectifiers, developed about 100

years ago, are an essential part of powering our electronic appliances. They take

household current and change it to a more useful form.

1.3.2 Working principle:

Here we use bridge rectifier because it is more efficient when compared to half

wave rectifier. It is the most frequency-used circuit for electronic dc power supplies.

During the positive half cycle of the input, diodes D1 and D2 are forward biased

and we get output across RL. This was all about only positive cycle of AC input wave.

During the negative half cycle the diodes D3 and D4 of bridge rectifier are in

forward biased, and other two diodes are reverse biased. So, only D3 and D4 conducts

and we get output across the RL.

1.4 Filter:

The pulsating dc from the rectifier is generally still not suitable to power the

actual load circuit. The pulsations typically vary from 0 volts to the peak output voltage

of the transformer. Therefore, we insert a circuit to store energy during each voltage

drops. This circuit is called a filter, and its job is to reduce the pulse from the rectifier

to much smaller ripple voltage. No filter configuration can be absolutely perfect, but a

properly designed filter will provided a dc output voltage with only a small ac ripple.

1.4.1 Capacitor filter:

If we place a capacitor at the full-wave rectifier as shown to the left, the capacitor

will charge to the peak voltage each to the peak voltage each half cycle, and then will

discharge more slowly through the load while the rectifier voltage drops back to zero

before beginning the next half-cycle. Thus, the capacitor helps to fill in the gaps

between the packs, as shown in red in the first figure to the right.

Although we have used straight lines for simplicity, the decay is actually the normal

exponential decay of any capacitor discharging through a load resistor. The extent to

which the capacitor voltage drops depends on the capacitance on the capacitor and the

amount of current drawn by the load; these two factor effectively from the RC time

constant for voltage decay.

1.4.3 Voltage regulator:

The 78xx (sometimes L78xx, LM78xx, MC78xx...) is a family of self-contained

fixed linear voltage regulator integrated circuits. The 78xx family is commonly used

in electronic circuits requiring a regulated power supply due to their ease-of-use and

low cost. For ICs within the family, the xx is replaced with two digits, indicating the

output voltage (for example, the 7805 has a 5 volt output, while the 7812 produces

12 volts). The 78xx line are positive voltage regulators: they produce a voltage that is

positive relative to a common ground. There is a related line of 79xx devices which are

complementary negative voltage regulators. 78xx and 79xx ICs can be used in

combination to provide positive and negative supply voltages in the same circuit.

78xx ICs have three terminals and are commonly found in the TO220

form factor, although smaller surface-mount and larger TO3 packages are available.

These devices support an input voltage anywhere from a couple of volts over the

intended output voltage, up to a maximum of 35 to 40 volts depending on the make,

and typically provide 1 or 1.5 amperes of current (though smaller or larger packages

may have a lower or higher current rating). IC regulator is used to give 6 volt because

the 6 volt sensor is used in the circuit.

1.5. Discrete Components:

1.5.1 Resistance:

It may be defined as the property of a substance, due to which it opposes the

flow of electricity through it. Resistance is the opposition that a substance offers to the

flow of electric current. It is represented by the uppercase letter R. The standard unit

of resistance is the Ohm (). When an electric current of one ampere passes through a

component across which a potential difference (voltage) of one volt exists, then the

resistance of that component is one ohm. In general, when the applied voltage is held

constant, the current in a direct-current (DC) electrical circuit is inversely proportional

to the resistance. If the resistance is doubled, the current is cut in half; if the resistance

is halved, the current is doubled. This rule also holds true for most low frequency

alternating-current (AC) systems, such as house hold utility circuits.

1.6 Light Emitting Diodes:

LED is commonly called LEDs, are real unsung heroes in the electronics world.

They do dozens of different jobs and are found in all kinds of devices. Among other

things, they form numbers on digital clocks, transmit information from remote controls,

light up watches and tell you when your appliances are turned on. Collected together,

they can form images on a jumbo television screen or illuminate a traffic light.

CHAPTER 2

RELAY

2.1 Introduction:

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 application where it is necessary to control, a circuit by low power signal, of 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 indicator. Relays found extensive used in telephone exchange early

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

required to directly drive an electrical motor is called a conductor.

Solid state relays control power circuits with no moving parts, instead using

semiconductor device triggering by light to perform switching. Relays with calibrated

operating characteristics and something multiple operating coils are used to product

electrical circuits from overload or faults in modern electrical power system these

functions are performed by digital instructions still called Production Relay.

2.2 Construction:

A simple electromagnetic relay such as the one taken from a car in the first

picture is an adaptation of an electromagnet. It consist of a coil of wire surrounding

soft iron core, an iron yoke, which provides a low reluctant path for magnetic flux, a

movable iron armature, and a sets, of contact. The armature is hinged to the yoke and

mechanically linked to a moving contact or contacts. It is held in a place by a spring so

that when the relay is de-energized there is an air gap in the magnetic circuit. In this

condition, one of the two sets of contact in the relay pictured is closed, and together set

is open relays other relays may have more or fewer sets of contacts depending on their

function. The relay in the picture also has a wire connecting the armature of the yoke.

This ensures continuity of the circuit between the moving contacts on the armature,

and the circuit track on the PCB via the yoke which is soldered to the PCB.

2.3 Operation:

When a current flows through the coil, the resulting magnetic field attracts an

armature that is mechanically linked to a moving contact. The movement either makes

or breaks a connection with a fixed contact. When the current to the coil is switched

off, the armature is returned by a force approximately half as strong as the magnetic

force to its relaxed position. Usually this is a spring, but the gravity is also used

commonly in industrial motor starts. Most relays are manufactured to operate quickly.

In low voltage applications, this is to reduce noise. In a high voltage application. In a

high voltage or high current application, this is to reduce arcing.

If the coil is energized with DC, a diode is frequently installed across the coil, to

dissipate the energy from the collapsing magnetic field at deactivation, which would

otherwise generate a spike of voltage and might cause damage to circuit components.

Some automotive relays already include that diode inside the relay case. If the coil is

designed to be energized with AC, a small copper ring can be crimped to the end of the

solenoid. This shading ring creates a small out-of-phase current, which increases the

minimum pull on the armature during the AC cycle.

2.3.2 NO Contact:

Normally-open (NO) contacts connect the circuit when thee relay is activated;

the circuit is disconnected when the relay is inactive. It is also called a Form A contact

or make contact.

2.3.3 NC Contact:

Normally-closed (NC) contacts disconnect the circuit when the relay is

activated; the circuit is connected when the relay is inactive. It is also called a Form B

contact or break contact.

CHAPTER 3

IR SENSOR

3.1 Introduction:

Infrared (IR) light is electromagnetic radiation with longer wave lengths than

those of visible light, extending from the normal red edge of the visible spectrum at

0.74 micrometers (m) to 0.3mm. This range of wavelengths corresponds to a

frequency range of approximately 430 down to 1THz, and includes most of the thermal

radiation emitted by objects near room temperature. Infrared light is emitted by

absorbed by molecules when they change their rational-vibration movements. The

existence of infrared radiation was first discovered in 1800 by astronomer William

Herschel.

3.2 Infrared rays:

Infrared (IR) light is electromagnetic radiation with longer wavelengths than

those of visible light, extending from the nominal red edge of the visible spectrum at

0.74 micrometers (m) to 0.3 mm. This range of wavelengths corresponds to a

frequency range of approximately 430 down to 1THz, and includes most of the thermal

radiation emitted by objects near room temperature. Infrared light is emitted or

absorbed by molecules when they change their rotational-vibration movements. The

existence of infrared radiation was first discovered in 1800 by astronomer William

Herschel.

Much of the energy from the Sun arrives on Earth in the form of infrared

radiation. Sunlight at zenith provides an irradiance of just over q kilowatt per square

meter at sea level. Of this energy, 527 watts is infrared radiation, 445 watts is visible

light, and 32 watts is ultraviolet radiation. The balance between absorbed and emitted

infrared radiation has a critical effect on the Earths climate. Infrared light is used in

industrial, scientific, and medical applications. Night-vision devices using infrared

illumination allow people or animals to be observed without the observer being

detected. In astronomy, imaging at dust. Infrared imaging cameras are used to detect

heat loss in mechanical is insulated systems, to observe changing blood flow in the

skin, and to detect overheating of electrical apparatus.

CHAPTER 4

DC GEAR MOTOR

4.1 Introduction:

A gear is a simple device that can change the speed, directions or torque of a

motor. Visually, a typical gear looks like a wheel with teeth around its circumference.

A gear box usually refers to a cars transmission, which is full of gears. A gear motor

is a type of electrical motor. Like all electrical motors, it uses the magnetism induced

by an electric current to rotate a rotor that is connected to a shaft. The energy transferred

from the rotor to the shaft is the used to a power of a connected device. In a gear motor,

the energy output is used to return a series of gears in an integrated gear train. There

are a number of different types of gear motors, but the most common are AC

(alternating current) and DC (direct current). A geared DC Motor has a gear assembly

attached to the motor. The speed of motor is counted in terms of rotations of the shaft

per minute and is termed as RPM.

The gear assembly helps in increasing the torque and reducing the speed.

Using the correct combinations of gears in a gear motion, its speed can be reduced to

any desirable figure. This concept where gears reduce the speed of the vehicle but

increasing its torque is knows as gear reduction. This Insight will explore all the minor

and major details that make the gear head and hence the working of geared DC motor.

4.2.1 Construction:

The DC Gear motor, consisting of a DC electric motor and a gearbox, is at the

heart of several electrical and electronic applications. Precision Micro drives have been

designing and developing such high quality mini DC gear motor in an easy to mount

package for a range of products and equipment.

Our miniature gear motor work smoothly and efficiently, supporting these

electrical and electronic applications. These geared motors have reduction gear trains

capable of providing high torque at relatively low shaft speed or revolutions per minute

(RPM). Precision Micro drives DC geared motors reduce the complexity and cost of

designing and constructing applications such as industrial equipment, actuators,

machine tools, and robotics.

Precision Micro drives have engineered a range of planetary and spur gear

motors (also known as mini-geared motors and micro-geared motors) suitable for many

future and existing applications. The main characteristics of these gear motors are

miniature form factors, offering significant strength torque, and other technical

capabilities that these applications require. Their linear performance characteristics

make term suitable for many applications requiring a controlled performance.

Whether you are looking for automotive, medical, or domestic applications, DC

Gear motors from Precision Micro drives not only offer the variable speed and torque

control required in each of these applications. These also possess quality characteristics

of reliability, ruggedness, and compactness.

The operations performed by Precision Micro drives geared motors

appear simple and effortless. However, they are highly sophisticated devices, and some

units are encapsulated in housings to prevent exposure to moisture and dust. Precision

Micro drives are the leading supplier of sub 60 mm DC Gear motors in the industry.

4.3. Working:

The DC motor works over a fair range of voltage. The higher the input voltage

more is the RPM (rotations per minute) of the motor. For example, if the motor works

in the range of 6-12V, it will have the least RPM at 6V and maximum at 12V.

The working of the gears is very interesting to know. It can be explained by the

principle of conservation of angular momentum. The gear having smaller radius will

cover more RPM than the one with large radius. However, the larger gear will give

more torque to the smaller gear than vice versa. The comparison of angular velocity

between input gear (the one that transfers energy) to output gear gives the gear ratio.

When multiple gears are connected together, conversations of energy is also

followed. The directions in which the other gear rotates is always the opposite of the

gear adjacent to it. In any DC motor, RPM and torque are inversely proportional.

Hence the gear having more torque will provide a lesser RPM and conserves. In a

geared DC motor, the concept of pulse width modulation is applied. The equations

detailing the working and torque transfer of gears are shown below.

In a geared DC motor, the gear connecting the motor and the gear head is quite

small, hence it transfers more speed to the larger teeth part of the gear head and makes

it rotate. The larger part of the gear further turns the smaller duplex part receives the

torque but not the speed from its predecessor which it transfers to larger part of other

gear and so on. The third gears duplex part has more teeth than others and hence it

transfers more torque to the gear that is connected to the shaft.

In a gear motor, the magnetic current (which can be produced by either

permanent magnets or electromagnets) turns gears that the either in a gear reduction

unit or in an integrated gear box. A second shaft is connected to this gears. The result

is that the gears greatly increase the amount of torque the motor is capable of producing

while simultaneously slowing down the motors output speed. The motor will not need

to draw as much current to function and will more slowly, but will provide greater

torque.

4.3.1 Speed:

If a gear driven by a motor (the input gear) has more teeth than the gear it is

connected gear, or output gear, will move faster than the output gear. This increases

speed at the output. Reversing the gearing will reduce speed at the input.

4.3.2 Torque:

Basically, when gears reduce speed, they increase torque, or force that can be

used to turn wheels or other gears. In geared motor, the gear system consists a set of

gear small pulley.

In a gear motor, the magnetic current (which can be produced by either

permanent magnets or electromagnets) turns gears that the gear either in a gear

reduction unit or in an integrated gear box. A second shaft is connected to these gears.

The result is that the gears greatly increase the amount or torque the motor is capable

of producing while simultaneously slowing down the motors output speed.

The motor will not need to draw as much current to function and will move more

slowly, but will provide greater torque. Its having the function of torque reducing

characteristics. When the torque is provided the torque will be splitting (or) reduce by

gear pulleys.

In performance curve, the speed is initially increase from when power is get to

the device, then its reducing by a gear system.

In base curve,

The torque is directly proportional to the applying a current of the motor.

The torque is indirectly proportional to the speed of the motor.

T I

T P/V

T I/S

Where,

T-torque represents new

S-Speed in RPM

4.5. Specifications:

DC supply 4 to 12 V

RPM: 30 at 12 V

Total length: 46mm

Motor diameter: 36mm

Motor length: 25mm

Brush type: Precious metal

Gear head diameter: 37mm

Gear head length: 21mm

Output shaft: Centered

Shaft diameter: 6mm

Shaft length: 22mm

Gear assembly: Spur

Motor weight: 100gms

4.6. Applications:

Garage door openers, Stair lifts, Timer cycle knobs on washing machine, Power drills,

Cake mixers, Jacks, Cranes, Lifts, Clamping, Robotics, Conveyance and Mixing are

too numerous to count.

CHAPTER 5

STEPPER MOTOR

5.1 Introduction:

A stepper motor is an electro mechanical device, which converts electrical pulses

into discrete mechanical movements. The shaft or spindle of a stepper motor rotates in

discrete step increments when electrical command pulses are applied to it in the proper

sequence. The sequence of the applied pulses is directly related to the direction of

motor shafts rotation. The speed of the motor shafts rotation is directly related to the

frequency of the input pulses and the length of rotation of input pulses applied.

5.2 Advantages:

The rotation angle of the motor is proportional to the input pulse.

The motor has full torque at stand still (if the winding are energized)

Precise positioning and repeatability of movement since good stepper motors

have an accuracy of 3 5% of a step and this error is non-cumulative from one

step to the next.

Excellent response to starting stopping reversing.

Very reliable since there are no contact brushes in the motor. Therefore the

life to the motor is simply dependent on the life of the bearing.

The motors response to digital input pulses provides open-loop control, making

the motor simpler and less costly to control.

It is possible to achieve very low speed synchronous rotation with a load that is

directly coupled to the shaft.

A wide range of rotational speed is proportional to the frequency of the input

Pulses.

5.2.2 Disadvantages:

Resonance can occur if not properly controlled.

Not easy to operate at extremely high speeds.

5.3 Open Loop Operation:

One of the most significant advantages of a stepper motor is its ability to be

accurately controlled in an open loop system. Open loop control means no feedback

information about position is needed. This type of control eliminates the need for

expensive sensing and feedback devices such as optical encoders. Your position is

known simply by keeping track of the input step pulses.

5.4 Types:

Variable-reluctance

Permanent-magnet

Hybrid

5.4.1 Variable-reluctance (VR):

This type of stepper motor has been around for a long time. It is probably

the easiest to Understand from a structural point of view. Figure 1 shows a cross section

of a typical V.R. stepper motor. This type of motor consists of a soft iron multi-toothed

rotor and wound stator. When the stator windings are energized with DC current the

poles become magnetized. Rotation occurs when the rotor teeth are attracted to

energized stator poles.

Figure 1. Cross-section of a VR Motor

5.4.2 Permanent Magnet (PM):

Often referred as a tin can or can stack motor the permanent magnet step

motor is a low cost and low-resolution type motor with typical step angles of 7.50 to

150. PM motors as the name implies have permanent magnets added to the motor

structure. Then rotor no longer has teeth as with the VR motor. Instead the rotor is

magnetized with alternating north and south poles situated in a straight line parallel to

the rotor shaft. These magnetized motor poles provide increased magnetic flux

intensity and because of this the PM motor exhibits improved torque characteristics

when compared with the VR type.

5.4.3 Hybrid (HB):

The hybrid stepper motor is more expensive then the PM stepper motor but

provides better performance with respect to step resolution, torque and speed. Typical

step angles for the HB stepper motor range from 3.60 to 0.90. The hybrid stepper motor

combines the best features of both the PM and VR type stepper motor. The rotor is

multi-toothed like the VR motor and contains an axially magnetized concentric magnet

around its shaft. The teeth on the rotor provide and even magnetic flux to preferred

locations in the air gap. This further increases the detent, holding and dynamic torque

characteristics of the motor when compared with both the VR and PM types. The two

most commonly used types of stepper motors are the permanent magnet and the hybrid

types. If a designer is not sure which type will best fit his applications requirements he

should first evaluate the PM type as it normally several times less expensive. If not

then the hybrid motor may be the right choice. There also exist some special stepper

motor designs. One is the disc magnet motor. Here the motor is designed as a disc with

rare earth magnets. This motor type has some advantages such as low inertia and a

optimized magnetic flow path with no coupling between the two stator windings. These

qualities are essential in some applications.

Figure 3. Cross-section of a hybrid

Stepper motor

5.4.4 Size and Power:

In addition to being classified by their step angle stepper motors are also

classified according to frame sizes which corresponding to the diameter of the body of

the motor. For instance a size 11-stepper motor has a body diameter of approximately

1.1 inches. Likewise a size 23 stepper motor has a body diameter of 2.3 inches. The

body length may however, vary from motor to motor within the same frame size

classification. As a general rule the available torque output from a motor of particular

frame size will increase with increased body length.

Power levels for IC-driven stepper motors typically range from below a watt for

very small motors up to 10-20 watts for larger motors. The maximum power dissipation

level. Or thermal limits for the motor are seldom clearly stated in the motor

manufactures data. To determine this we must apply the relationship P = V X I. For

example, a size 23 step motor may be rated at 6V and 1A per phase.

Therefore, with two phases energized the motor has a rated power dissipation of

12 watts. It is normal practice to rate a stepper motor at the power dissipation level

where the motor case raises 650C above the ambient in still air. Therefore, if the motor

can be mounted to a heat sink it is often possible to increase the allowable power

dissipation level. This is important as the motor is designed to be and should be used

at this maximum power dissipation, to be efficient from a size/output power/cost point

of view.

5.7 The Rotating Magnetic Field:

When a phase winding of a stepper motor is energized with current a magnetic

flux is developed in the stator. The direction of this flux is determined by the Right

Hand Rule which states: If the coil is grasped in the right hand with the fingers

pointing in the direction of the current in the winding (the thumb is extended at a 900

angle to the fingers), then the thumb will point in the direction of the magnetic field.

The rotor then aligns itself so that the flux opposition is minimized. In this case

the motor would rotate clockwise so that its south pole aligns with the north pole of

stator B at position 2 and its north pole aligns with the south pole of stator B at position

6. To get the motor to rotate we can now see that we must provide a sequence of

energized the stator windings in such a fashion that provides a rotating magnetic flux

field with the rotor follows due to magnetic attraction.

5.10 Stepper motor driver circuit:

Stepper motor performance is strongly dependent on the driver circuit. Torque

curves may be extended to greater speeds if the stator poles can be reversed more

quickly, the limiting factor being the winding inductance. To overcome the inductance

and switch the windings quickly, one must increase the drive voltage. This leads further

to the necessity of limiting the current that these high voltages may otherwise induce.

5.10.1 L/R driver circuits:

L/R driver circuits are also referred to as constant voltage drives because a

constant positive or negative voltage is applied to each winding to set the step positions.

However, it is winding current, not voltage that applies torque to the stepper motor

shaft. The current I in each winding is related to the applied voltage V by the winding

inductance L and the winding resistance R. The resistance R determines the maximum

current according to Ohm's law I=V/R. The inductance L determines the maximum rate

of change of the current in the winding according to the formula for an inductor di/dt

= V/L. Thus when controlled by an L/R drive, the maximum speed of a stepper motor

is limited by its inductance since at some speed, the voltage U will be changing faster

than the current I can keep up. In simple terms the rate of change of current is L / R

(e.g. a 10 mH inductance with 2 ohms resistance will take 5 ms to reach approx. 2/3 of

maximum torque or around 24 ms to reach 99% of max torque). To obtain high torque

at high speeds requires a large drive voltage with a low resistance and low inductance.

With an L/R drive it is possible to control a low voltage resistive motor with a

higher voltage drive simply by adding an external resistor in series with each winding.

This will waste power in the resistors, and generate heat. It is therefore considered a

low performing option, albeit simple and cheap.

5.10.3 Full step drive (one phase on):

In this drive method only a single phase is activated at a time. It has the same

number of steps as the full step drive, but the motor will have significantly less than

rated torque. It is rarely used. The animated figure shown above is a wave drive motor.

In the animation, rotor has 25 teeth and it takes 4 steps to rotate by one teeth position.

So there will be 25*4 = 100 steps per full rotation and each step will be 360/100 = 3.6

degrees.

5.10.4 Full step drive (two phases on):

This is the usual method for full step driving the motor. Two phases are always

on so the motor will provide its maximum rated torque. As soon as one phase is turned

off, another one is turned on. Wave drive and single phase full step are both one and

the same, with same number of steps but difference in torque.

5.12 Half stepping:

Its angle per step is half of the full step.

5.12.1 Micro stepping:

What is commonly referred to as micro stepping is often "sine cosine micro

stepping" in which the winding current approximates a sinusoidal AC waveform. Sine

cosine micro stepping is the most common form, but other waveforms can be used.[4]

Regardless of the waveform used, as the micro steps become smaller, motor operation

becomes more smooth, thereby greatly reducing resonance in any parts the motor may

be connected to, as well as the motor itself. Resolution will be limited by the

mechanical station, backlash, and other sources of error between the motor and the end

device. Gear reducers may be used to increase resolution of positioning. Step size

repeatability is an important step motor feature and a fundamental reason for their use

in positioning.

Example: many modern hybrid step motors are rated such that the travel of

every full step (example 1.8 degrees per full step or 200 full steps per revolution) will

be within 3% or 5% of the travel of every other full step, as long as the motor is operated

within its specified operating ranges. Several manufacturers show that their motors can

easily maintain the 3% or 5% equality of step travel size as step size is reduced from

full stepping down to 1/10 stepping. Then, as the micro stepping divisor number grows,

step size repeatability degrades. At large step size reductions it is possible to issue

many micro step commands before any motion occurs at all and then the motion can

be a "jump" to a new position.

CHAPTER 6

STARTER MOTOR

6.1 Introduction:

The starter motor converts electrical energy to mechanical energy and is

mounted on the cylinder block in a position to engage a ring gear on the engine

flywheel. Starting is usually accomplished by the operator activating a starter switch

as part of ignition key operation. This allows a relatively small current to flow to a

starter solenoid relay and operate a plunger attached to a drive pinion engagement

lever. The plunger movement engages the drive pinion with the ring gear and closes a

set of heavy duty contacts, allowing a large current to flow from the battery to the

starter motor, rotating the armature and drive pinion, and causing the crankshaft to spin.

When the engine starts and is able to run on its own, the operator usually releases

the key and this withdraws the pinion from the ring gear and brings the armature to a

halt.

6.2 Starting Systems:

The electric starter motor or starting motor is the most common type used on

gasoline engines and small Diesel engines. The modern starter motor is either a

permanent-magnet or a series-parallel wound direct current electric motor with a starter

solenoid (similar to a relay) mounted on it. When current from the starting battery is

applied to the solenoid, usually through a key-operated switch, the solenoid engages a

lever that pushes out the drive pinion on the starter driveshaft and meshes the pinion

with the starter ring gear on the flywheel of the engine.

The solenoid also closes high-current contacts for the starter motor, which

begins to turn. Once the engine starts, the key-operated switch is opened, a spring in

the solenoid assembly pulls the pinion gear away from the ring gear, and the starter

motor stops.

6.3 Parts:

Armature

Commutator

Brushes

Pole Shoe

Field Coil

6.5 Application:

Industry

Automobile

HVAC Device

CHAPTER 7

STARTER SOLENOID SWITCH

7.1 Introduction:

The quality solenoid switches catered by us are at par with international

standards. Our solenoid switches are specially designed for high current applications.

7.2 Working of Solenoid Switch:

A solenoid switch works by having an electromagnet which is used to convert

electrical energy into mechanical energy. The magnetic field within the solenoid helps

create a linear motion.

The solenoid receives a large electric current from the car battery and a small

electric current from the ignition switch. As the ignition switch is turned, a small

electric current is sent to the starter solenoid. The pair of heavy contacts closes, relaying

the large electric current to the starter motor, which in turn sets the engine in motion.

Once the engine starts, the key-operated switch is turned, a spring in the solenoid

assembly pulls the pinion gear away from the mesh, and the starter motor stops. The

starter's pinion is clutched to its driveshaft through an over running sprog clutch which

allows the pinion to transmit drive in only single direction. In this manner, drive is

transmitted through the pinion to the flywheel ring gear.

7.4 Maintenance:

If the power supply to the solenoid is insufficient, it will fail to start the motor

and may produce a rapid clicking or clacking sound. The lack of the power may be

caused by a low or dead battery, by corroded or loose connections in the battery cable,

or by a damaged positive (red) cable from the battery. Any of such problem may create

resistance for the current resulting in proper transmission of the power. To reduce the

chances for such as failure, the battery connections should be cleaned and tightened at

every oil change. Starting fault of the solenoid can detected at service center by a test

of the car's starting, charging and battery systems.

7.5 Applications of Solenoid Switch:

Besides wide scale engine starting applications, solenoid switches are used to

switch on many other types of motors while mechanically engaging or disengaging

their shafts. This allows latching and opening mechanisms for windows, doors and

hatches to derive two functions from the same piece of coordinated equipment.

CHAPTER 8

PROGRAMMABLE LOGIC CONTROLLER

8.1 Introduction:

Its always good to get an over view of where designs have been and where they

are going. To do this its essential to get a birds eye view of the concepts and processes

that make the PLC so valuable in industrial control. Pitting PLCs against other control

types will also serve to show the pros and cons for different applications.

8.2 Construction:

A programmable logic controller is a specialized computer used to control

machines and processes. It therefore shares common terms with typical PCs like central

processing unit, memory, software and communications. Unlike a personal computer

through the PLC is designed to survive in a rugged industrial atmosphere and to be

very flexible in how it interfaces with inputs and outputs to the real world.

The components that make a PLC work can be divided in to three core areas.

The power supply and rack.

The central processing unit(CPU)

The input/output(I/O) section

PLCs come in many shapes and sizes. They can be so small as to fit in your shirt

pocket while more involved control systems and large PLC racks. Smaller PLCs (a.k.a.

Bricks) are typically designed with fixed (I/O) points. For our construction, well

look at the more modular rack based systems. Its called modular because the rack

can accept many different types of I/O modules that simply slide into the rack and plug

in.

The rack is the component that holds everything together. Depending on the

needs of the control system it can be ordered in different sizes to hold more modules.

Like a human spine the rack has a backplane at the rear which allows the cards to

communicate with the CPU. The power supply plugs into the rack as well and supplies

a regulated DC power to other modules that plug into the rack. The most popular power

supplies work with 120v DC sources.

The Central Processing Unit (CPU) Module is the brain of the PLC. The Primary

functions are to read inputs, execute the control program, and update outputs. CPU

architecture may differ from one manufacturer to another, but in general, most CPUs

follow this typical three-component organization.

The CPU consists of following three components:

i) Processor ii) Memory system iii) Power supply

i) Processor:

The processor executes the user program stored in the memory system in the

form of ladder diagrams. It makes all the decisions necessary to carry out the user

program based on the status of inputs and outputs for control of a machine or

process. It can also perform arithmetic functions, data manipulation and

communication between the local I/O, remotely located I/O and other networked

PLC.

ii) Memory system:

The memory system is the area in the CPU where all the programs, are stored

and executed by the processor to provide the desired control of field devices.

iii) Power supply:

Power supply is necessary to convert 120V or 240V a.c into the low voltage d.c

(+5V & -5V) required for processor and internal power required for the I/O

modules. This power supply unit does not supply power for the actual input or

output devices. This can be built into the PLC or be an external unit. Common

voltage levels required by the PLC are 24Vdc, 120Vac, 220Vac.

8.3 PLC Operation:

The CPU accepts input signal from sensors like push buttons, limit switches,

analog sensors, selector switches, and thumbwheel switches.

Stores the status of input in the memory area called input image table.

Execute the stored user program from memory and sends appropriate output

commands to control devices like motor starters, solenoid valves, pilot lights,

and position valves through output image table.

Update the content of output image table.

The system power supply provides all the voltages required for the proper

operation of the various central processing unit sections.

8.5. I/O Modules:

The input/output (I/O) system is the section of a PLC to which all of the field

devices are connected. If the CPU can be thought of as the brains of a PLC, then the

I/O system can be thought of as the arms and legs. It creates the physical connection

between the field equipment and the PLC. I/O modules are available as either input

only, output only or a combination of inputs and outputs.

8.5.2 Discrete Input Module :

A discrete input also referred to as a digital input. Discrete input module is the

most common input interface used with PLC. Discrete input signals from field devices

can be either AC or DC.

The discrete input module communicates the status of the various real world

input devices connected to the module to the CPU. Hence it provides the physical

connection between the CPU and field devices. Digital or discrete signals are non-

continuous signals that have only two statesON and OFF. In the ON condition a

discrete input may be referred to as logic 1 or logic high. In the OFF condition a discrete

input may be referred to as logic 0 or a logic low.

8.5.3 Typical INPUT Modules:

o DC voltage (110, 220, 14, 24, 48, 15-30V) or current (4-20 mA).

o AC voltage (110, 240, 24, 48V) or current (4-20 mA).

o TTL (transistor-transistor logic) input (3-15VDC).

o Analogue input (12-bit).

o Word input (16-bit/parallel).

o Thermocouple input.

o Resistance temperature detector.

o High current relay.

o Low current relay.

o Latching input (24VDC/110VAC.

o Isolated input (24VDC/85-132VAC).

o Intelligent input (contains a microprocessor).

o Positioning input.

o PID (proportional, integral, differentiation) input.

o High-speed pulse.

8.5.5 Typical Output Modules:

DC voltage (24, 48,110v) or current (4-20mA).

AC voltage (110,240v) or current (4-20mA).

Isolated (24VDC).

Analog output (12-bit).

Intelligent output.

ASCII output.

Dual communication port PLC.

8.6 Memory Section:

This section stores (electronically) retrievable digital information in three

dedicated locations of the memory. These memory locations are routinely scanned by

the processor. The memory will receive (write mode) digital information or have

digital information accessed (read mode) by the processor. This read/write (R/W)

capability provides an easy way to make program changes.

The memory contains data for several types of information. Usually, the data

tables, or image registers, and the software program RLL are in the CPU modules

memory. The program messages may or may not be resident with the other memory

data.

A battery backup is used by some manufacturers to protect the memory contents

from being lost should there be a power or memory module failure. Still other use

various integrated circuit (IC) memory technologies and design schemes that will

protect the memory contents without the use of a battery backup.

A typical memory section of the CPU module has a memory size of 98,304

(96K) bytes. This size tells us how many locations are available in the memory for

storage. Additional memory modules can be added to your PLC system as the need

arises for greater memory size. These expansion modules are added to the quantity of

I/O modules are added or the software program becomes larger. When this is done, the

memory size can be as high as, 1,048,576 (1024K) bytes.

Manufacturers will state memory size in either bytes or words. A byte is

eight bits, and a bit is the smallest digit in the binary code. Its either logic 1 or logic

0. A word is equal in length to two bytes or 16 bits. Not all manufacturers use 16-bit

words, so be aware of your PLC manufacturers has defined as its memory word bit

size.

8.4 Ladder Logic:

In these modern times a PC with especially dedicated software from the PLC

manufacturer is used to program a PLC. The most widely used from of programming

is called ladder logic. Ladder logic uses symbols, instead of words, to emulate the real

world relay logic control, which is a relic from the PLCs history. These symbol are

interconnected by lines to indicate the flow of current trough relay like contacts and

coils. Over the years the number of symbols has increased to provide a high level of

functionality.

The completed programmer looks like a ladder but in actuality I represents an

electrical circuit. The left and right rails indicate the positive and round of a power

supply. The rungs represent the wiring between the different so if you can understand

how basic electrical circuits work then you can understand ladder logic.

In this simplest of examples a digital input (like a button connected to the first

position on the card) when it is pressed turns on an output which energizes an indicator

light. The competed program is downloaded from the PC to the PLC using a special

cable thats connected to the front of the CPU. The CPU is then put into run mode so

that it can start scanning the logic and controlling the outputs.

In the world of automation these types of TRUE or FALSE conditions come

down to a device being ON or OFF, CLOSED or OPEN, PRESENT or ABSENT,

24nVOLTS or 0 VOLTS. In the PLC it all boils down to our now familiar binary

system of a 1 or 0. Typically having a bit ON presents a TRUE condition while OFF

in FALSE. This is arbitrary though as it may make more sense to use what is called

failsafe logic and have an ON bit an a FALSE condition.

CHAPTER 9

LIMIT SWITCH

9.1 Introduction:

In electrical engineering a limit switch is a switch operated by the motion of a

machine part or presence of an object. They are used for control of a machine, as safety

interlocks, or to count objects passing a point. A limit switch is an electromechanical

device that consists of an actuator mechanically linked to a set of contacts. When an

object comes into contact with the actuator, the device operates the contacts to make

or break an electrical connection. Limit switches are used in a variety of applications

and environments because of their ruggedness, ease of installation, and reliability of

operation. They can determine the presence or absence, passing, positioning, and end

of travel of an object. They were first used to define the limit of travel of an object;

hence the name Limit Switch.

A limit switch with a roller-lever operator; this is installed on a gate on a canal

lock, and indicates the position of a gate to a control system. Standardized limit

switches are industrial control components manufactured with a variety of operator

types, including lever, roller plunger, and whisker type. Limit switches may be directly

mechanically operated by the motion of the operating lever. A reed switch may be used

to indicate proximity of a magnet mounted on some moving part. Proximity switches

operate by the disturbance of an electromagnetic field, by capacitance, or by sensing a

magnetic field.

Rarely, a final operating device such as a lamp or solenoid valve will be directly

controlled by the contacts of an industrial limit switch, but more typically the limit

switch will be wired through a control relay, a motor contactor control circuit, or as an

input to a programmable logic controller.

Miniature snap-action switch may be used for example as components of such

devices as photocopiers or computer printers, to ensure internal components are in the

correct position for operation and to prevent operation when access doors are opened.

A set of adjustable limit switches are installed on a garage door opener to shut off the

motor when the door has reached the fully raised or fully lowered position. A numerical

control machine such as a lathe will have limit switches to identify maximum limits

for machine parts or to provide a known reference point for incremental motions

Function of limit switch:

Limit switches provide the function of making and breaking electrical contacts

and consequently electrical circuits.

A limit switch is configured to detect when a system's element has moved to a

certain position. A system operation is triggered when a limit switch is tripped.

Application of limit switch:

Limit switches are widely used in various industrial applications, and they can

detect a limit of movement of an article and passage of an article by displacement

of an actuating part such as a pivotally supported arm or a linear plunger.

The limit switches are designed to control the movement of a mechanical part.

Limit switches are typically utilized in industrial control applications to

automatically monitor and indicate whether the travel limits of a particular

device have been exceeded. Limit switches are used in a variety of applications

and environments because of their ruggedness, simple visible operation, ease of

installation and reliability of operation.

CHAPTER 11

BIBLIOGRAPHY

Reference Books:

[1]. Beginning Arduino Programming by Brian Evans - Technology in action.

[2]. Arduino Robotics by John-David Warren, Josh Adams Apree.

[3]. Practical Arduino Engineering by Harold Timmis - Technology in action.

URL Reference:

[1]. www.arduino.cc

[2]. www.efymag.com

[3]. www.simplelab.co.in