بسم الله الرحمن الرحيم

AlMughtaribeen University

College of Engineering

Biomedical Engineering Department

Design of Film Rotary Evaporator

A dissertation submitted in partial fulfillment of the requirements for the

B.Sc. (Honors) Degree in Biomedical Engineering

By:

Arafa Moatasim Abass Ahmed & Alyaa Obeid Osman Obeid

Supervisor: Dr. Zeinab Adam Mustafa

January 2017

Dedication:

We dedicate our dissertation work to our families, teachers, college and our friends.

A special feeling of gratitude to our loving parents, for their words of

encouragement. Our teachers, have never left our side and are very special. We will

always appreciate all they have done, for helping us to develop our knowledge, skills

and to start our career life.

Our families

Our teachers

Our friends

Our College

Our Fathers

Our Mothers

Acknowledgment:

The success and final outcome of this project required a lot of guidance and

assistance from many people and we are extremely privileged to have got this all

along the completion of our project. All that we have done is only due to such

supervision and assistance and we would not forget to thank them.

We respect, owe my deep gratitude to our project supervisor, Dr. Zinab Adam, the

head of Biomedical Engineering department for providing us an opportunity to do

this project and giving us all support and guidance which made us complete the

project successfully. We are extremely thankful to her for providing such a nice

support and guidance, although she had busy schedule managing the head

department duties.

We are thankful to and fortunate enough to get constant encouragement, support

and guidance from all Teaching staffs of Biomedical Engineering Department which

helped us in successfully completing our project work.

TABLE OF CONTENTS

Table of Contents ................................................................................................... 1.4

1. Introduction ...............................................................................................1.10

1.1 GENERAL IDEA: ..............................................................................................1.12

1.2 ENERGETIC ....................................................................................................1.12

1.3 HOW AN EVAPORATOR WORKS ...........................................................................1.13

1.4 TYPES OF EVAPORATORS USED TODAY ..................................................................1.13

1.4.1 NATURAL FORCED CIRCULATION EVAPORATOR ..................................................1.13

1.4.2 FALLING FILM EVAPORATOR .........................................................................1.14

1.4.3 PLATE EVAPORATOR ...................................................................................1.14

1.5 MAIN ARTICLE: MULTIPLE-EFFECT EVAPORATOR .....................................................1.15

1.6 PROBLEM STATEMENT ......................................................................................1.16

1.7 OBJECTIVES ...................................................................................................1.16

2. Literature Review.......................................................................................2.18

2.1 HOW EVAPORATOR WORKS ...............................................................................2.19

2.2 MOTOR CONTROLLER.......................................................................................2.19

2.3 APPLICATIONS ................................................................................................2.19

2.3.1 TYPES OF MOTOR CONTROLLERS ...................................................................2.20

2.3.2 MOTOR STARTERS .....................................................................................2.20

2.3.3 REDUCED VOLTAGE STARTERS .......................................................................2.21

2.3.4 MAIN ARTICLE: ADJUSTABLE-SPEED DRIVE .......................................................2.21

2.3.5 INTELLIGENT CONTROLLERS ..........................................................................2.21

2.3.6 OVERLOAD RELAYS ....................................................................................2.22

2.3.7 LOSS OF VOLTAGE PROTECTION .....................................................................2.22

2.3.8 SERVO CONTROLLERS .................................................................................2.23

2.3.9 STEPPER MOTOR CONTROLLERS ....................................................................2.24

3. Theoretical Background .............................................................................3.26

3.1 DISTILLATION .................................................................................................3.26

3.1.1 SIMPLE DISTILLATIONS ................................................................................3.27

3.1.2 FRACTIONAL DISTILLATION ...........................................................................3.27

3.2 VAPOR-LIQUID EQUILIBRIA ................................................................................3.28

3.2.1 TYPES OF BINARY VAPOR-LIQUID EQUILIBRIUM ..................................................3.28

3.3 HISTORY .......................................................................................................3.28

3.4 APPLICATIONS OF DISTILLATION ..........................................................................3.30

3.5 GENERAL IMPROVEMENTS .................................................................................3.31

3.6 LABORATORY SCALE DISTILLATION .......................................................................3.31

3.7 STEAM DISTILLATION .......................................................................................3.31

3.8 PERKIN TRIANGLE DISTILLATION SETUP ..................................................................3.32

3.9 VACUUM DISTILLATION.....................................................................................3.33

4. Materials and Methodology .......................................................................4.35

4.1 BLOCK DIAGRAM.............................................................................................4.35

4.2 CIRCUIT DIAGRAM ...........................................................................................4.36

4.3 CIRCUIT DIAGRAM ...........................................................................................4.37

4.4 SOFTWARE OF CONTROL SYSTEM ........................................................................4.38

4.5 BILL OF QUANTITIES .........................................................................................4.42

5. Discussions and Results .............................................................................5.44

5.1 DISCUSSION ..................................................................................................5.44

5.2 RESULTS .......................................................................................................5.45

6. CONCLUSIONS AND RECOMMENDATIONS .................................................6.47

6.1 CONCLUSION .................................................................................................6.47

6.2 RECOMMENDATIONS .......................................................................................6.47

8. References .................................................................................................8.48

9. Appendix ...................................................................................................9.50

List of Figures

Figure ‎3-1 Distillate ......................................................................................................... 3.26

Figure ‎3-2 Evaporation in the past ..................................................................................... 3.28

Figure ‎3-3 Evaporation in the past ..................................................................................... 3.29

Figure ‎3-4 Distillation ...................................................................................................... 3.29

Figure ‎3-5 Old Ukrainian vodka still ................................................................................... 3.29

Figure ‎3-6 Dimethyl sulfoxide ........................................................................................... 3.32

Figure ‎3-7 Perkin triangle distillation setup ......................................................................... 3.32

Figure ‎4-1 Block Diagram ................................................................................................. 4.35

Figure ‎4-2 power supply .................................................................................................. 4.36

Figure ‎4-3 control system ................................................................................................. 4.37

Figure ‎5-1 the control system under the test ....................................................................... 5.44

Figure ‎5-2 the system in operating state ............................................................................. 5.45

Figure ‎5-3 the system after finishing the setting time ........................................................... 5.45

Figure ‎8-1 ATmega16 ...................................................................................................... 9.50

Figure ‎8-2 Pin Diagram .................................................................................................... 9.51

Figure ‎8-3 Electric motor .................................................................................................. 9.54

Figure ‎8-4 Faraday's electromagnetic experiment, 1821........................................................ 9.55

Figure ‎8-5 Jedlik's "electromagnetic self-rotor" ................................................................... 9.55

Figure ‎8-6 LCD ................................................................................................................ 9.56

Figure ‎8-7 Pin Diagram .................................................................................................... 9.57

Figure ‎8-8 LM35 Temperature Sensor Image ....................................................................... 9.59

Figure ‎8-9 Pin Diagram .................................................................................................... 9.60

Figure ‎8-10 Diode bridge .................................................................................................. 9.61

Figure ‎8-11 bridge rectifiers ............................................................................................. 9.61

Figure ‎8-12 Detail of a diode bridge, rated at 1000 Volts x 4 Amperes ..................................... 9.62

Figure ‎8-13 A handmade diode bridge................................................................................ 9.62

Figure ‎8-14 A handmade diode bridge Diagram ................................................................... 9.63

Figure ‎8-15 A handmade diode bridge Diagram ................................................................... 9.64

Figure ‎8-16 AC, half-wave and full wave rectified signals ...................................................... 9.64

Figure ‎8-17 pulsed DC Output ........................................................................................... 9.65

Figure ‎8-18 Foxtech mini 5V 1A switch regulator 7805 .......................................................... 9.67

Figure ‎8-19 Automotive-style miniature relay (dust cover is taken off) .................................... 9.68

Figure ‎8-20 Simple electromechanical relay ........................................................................ 9.69

Figure ‎8-21 Small "cradle" relay ........................................................................................ 9.69

List of Tables

Table ‎4-1 Bill of Quantities .............................................................................................. 4.42

Table ‎5-1 Results Summary .............................................................................................. 5.45

Table ‎8-1 Pin Description ................................................................................................. 9.52

Table ‎8-2 Pin Description ................................................................................................. 9.58

Table ‎8-3 Pin Description ................................................................................................. 9.60

Abstract

One of the biggest concerns for our field of Biomedical Engineering is to provide the

alternatives of different equipment considering the high efficiency and low cost of

development.

The objective of this project is to sort out the idea to design and develop of Film

Rotary Evaporator considering the conceptual approach of this valuable equipment

in our laboratories.

This project focused on the needs of the local market to avail such types of

equipment since the current practice is to use the technique of center fugal to

separate the solvents from samples rather than evaporation.

We did the conceptual design using a simple circuit to show the main three

components of the rotary evaporator which are: micro controller, heater and motor

in addition to the other electronic components.

The control system of film rotary evaporator was designed and tested. using the at

mega 16, LCD 16*2,LM35 Temperature sensor, pushbutton, variable resisters, ULN

2003 deriver, relay module and LED indicators are used in the project. The results of

the project was registered and presented on the result of the project.

The limitations of this project that there is no body availed to this device, we

provided the main components and been linked to a simulation model to run the

circuit and make it functioning well and this was successfully done.

The recommendation of this project is to provide the necessary needs to develop

such equipment considering the low cost parameter and avail it in the local market

since this device is very high cost in the international market, and this project shows

the ability of developing this device with low cost.

CHAPTER ONE

INTRODUCTION

1. INTRODUCTION

A rotary evaporator is a device used in chemical laboratories for the efficient and

gentle removal of solvents from samples by evaporation. When referenced in the

chemistry research literature, description of the use of this technique and equipment

may include the phrase "rotary evaporator", though use is often rather signalled by

other language ("the sample was evaporated under reduced pressure").Rotary

evaporators are also used in molecular cooking for the preparation of distillates and

extracts.

Rotation driving apparatus usable with a rotary evaporator for holding a sample vessel

in a water bath. The driving apparatus includes a stator supported by an elevating

member mounted alongside the water bath, and a rotor mounted on the inside of the

stator. A hollow support shaft is mounted within the rotor, and the sample vessel is

detachably connected to one end of the support shaft. A concentrator can be

connected to the other end of the support shaft, for fluid communication with the

sample vessel through the hollow support shaft. The support shaft is affixed to the

rotor, so that the sample vessel and concentrator are rotated as the rotor turns. A

slitted disk is supported by the rotor, and a photo-sensor produces signals in response

to relative movement of the slits. These signals are used for controlling the rotation of

the driving apparatus.

An evaporator system for supporting a flask and rotating the flask for concentrating a

specimen solution contained in the flask, while simultaneously heating the specimen

by means of an isothermal heating source, comprising:

a lift means operatively supporting the flask for selective vertical movement of the

flask relative to the isothermal heating source;

a lift motor operatively associated with the lift means to move the flask up and down

relative to the isothermal heating source; a motor selectively operative to rotate the

flask supported by the lift a three-way solenoid valve connected to the vacuum source

and to atmospheric air pressure, and connected in communication with the interior of

the flask for selectively communicating the vacuum source or atmospheric air pressure

into the flask porter in which a sample a controlling apparatus operatively associated

with the motor rotating said flask said lift motor being operatively controlled by said

controlling apparatus to raise the flask upwardly above the isothermal heating source

for achieving a non-heating condition in response to passage of a predetermined

concentrating time period; said flask-rotating motor being operatively associated with

said controlling apparatus to automatically stop after operation of the solenoid valve,

thereby automating procedures at the end of the concentrating process; and said

controlling apparatus including means selectively operating the three-way valve to

subject the interior of the flask to the vacuum source during rotation of the flask and

to introduce atmospheric air pressure into the flask at a predetermined end of the

concentrating process. Description the present device relates to an rotary evaporator,

and more particularly to an rotary evaporator which rotates an eggplant-shaped flask

directly by a rotation driving apparatus without a reduction device.

In a conventional rotary evaporator, a worm gears mechanism rotates a sample vessel

such as an eggplant-shaped flask and the like in cooperation with a motor. Therefore

this conventional evaporator has shortcomings such that the construction in all

become large size and in engagement of gears yields noise and wear of the gears

A object of the invention is to provide a small and light-weight rotary evaporator

which can be realized due to omission of reduction system.

Another object of the invention is to provide a rotary evaporator in which an

unbalanced load which will act on an elevating member will be reduced.

Briefly described these and other objects of the invention are accomplished by

provision of a rotary evavessel applies to a rotary shaft which is hollow.

is a vertical cross sectional view of the preferred embodiment of the present invention

is a cross sectional view of a rotation driving apparatus.

is a view of one embodiment of a controlling system.

Referring to and FIG. the rotary evaporator according to this embodiment is

constituted in such a manner that an elevating member is vertically and elevationally

supported to a pole vertically mounted on a base A sample vessel

such as an eggplant-like flask of the like is removably attached to one end of a hollow

rotary shaft of a rotation driving apparatus supported to this elevating member A

concentrator is removably attached to the other end of the rotary shaft

A water bath is provided to heat the sample vessel.

Next, each part will be described in detail; however, since the sample vessel and the

concentrator are similar to those which will be generally 0used, their detailed

explanation are omitted. Although the water bath is not shown in detail

in FIGS. it is equipped with a heater to heat water and a temperature sensor to detect

a water temperature. This heater is ON/OFF controlled by a control unit such as a

microcomputer to always keep the water temperature in the water bath to be a pre-

determined temperature.

A guide hole is formed in the base portion of the elevating member so that the

elevating member is vertically and slid ably attached to the pole mounted vertically

on the base The rotation driving apparatus is supported to the end

portion of the elevating member sitting hole is further formed horizontally in the

elevating member The rotation driving apparatus is rotatable or fixedly supported to

a transverse shaft which is inserted and fixed into the fitting hole

Hence, the rotation driving apparatus can be revolved (inclined) around the

transverse shaft by loosening a lever provided for the rotation driving apparatus. The

rotation driving apparatus can be integrally fixed to the transverse shaft

by fastening the lever. Therefore, an angle of inclination of the sample vessel or the

like can be adjusted by appropriately revolving and fixing the rotation driving

apparatus.

1.1 GENERAL IDEA: own evaporator is used in an air conditioning system to allow the compressed cooling

chemical, Freon, to evaporate from liquid to gas while absorbing heat in the process. It

can also be used to remove water or other liquids from mixtures. The process of

evaporation is widely used to concentrate foods and chemicals as well as salvage

solvents. In the concentration process, the goal of evaporation is to vaporize most of

the water from a solution containing the desired product. In the case of desalination

of sea water, the reverse purpose applied evaporation removes the desirable drinking

water from the undesired product, salt.

One of the most important applications of evaporation is in the food and beverage

industry. Foods or beverages that need to last for a considerable amount of time or

need to have certain consistency, like coffee, go through an evaporation step during

processing

In the pharmaceutical industry, the evaporation process is used to eliminate excess

moisture, providing an easily-handled product and improves product stability.

Preservation of long-term activity or stabilization of enzymes in laboratories are

greatly assisted by the evaporation process.

Another example of evaporation is in the recovery of sodium hydroxide in

kraftpulpings. Cutting down waste handling cost is another major application of

evaporation for large companies. Legally, all producers of waste must dispose of the

waste in a method that abides by environmental guidelines; these methods are costly.

By removing moisture through vaporization, industry can greatly reduce the amount

of wasted product that must be processes.

1.2 ENERGETIC

Water can be removed from solutions in ways other than evaporation, including

membrane processes, liquid-liquid extractions, crystallization, and precipitation.

Evaporation can be distinguished from some other drying methods in that the final

product of evaporation is a concentrated liquid, not a solid. It is also relatively simple

to use and understand since it has been widely used on a large scale. In order to

concentrate a product by water removal, an auxiliary phase is used which allows for

easy transport of the solvent (water) rather than the solute. Water vapor is used as

the auxiliary phase when concentrating non-volatile components, such as proteins and

sugars. Heat is added to the solution and part of the solvent is converted into vapor.

Heat is the main tool in evaporation, and the process occurs more readily at high

temperature and low pressures.

Heat is needed to provide enough energy for the molecules of the solvent to leave the

solution and move into the air surrounding the solution. The energy needed can be

expressed as an excess thermodynamic potential of the water in the solution. Leading

to one of the biggest problems in industrial evaporation, the process requires enough

energy to remove the water from the solution and to supply the heat of evaporation.

When removing the water, more than 99% of the energy needed goes towards

supplying the heat of evaporation. The need to overcome the surface tension of the

solution also requires energy. The energy requirement of this process is very high

because a phase transition must be caused; the water must go from a liquid to a

vapor.

When designing evaporators, engineers must quantify the amount of steam needed

for every mass unit of water removed when a concentration is given. An energy

balance must be used based on an assumption that a negligible amount of heat is lost

to the system’s surroundings. The heat that needs to be supplied by the condensing

steam will approximately equal the heat needed to heat and vaporize the water.

Another consideration is the size of the heat exchanger which affects the heat transfer

rate. A = heat transfer area, q = overall heat transfer rate

1.3 HOW AN EVAPORATOR WORKS

The solution containing the desired product is fed into the evaporator and passes a

heat source. The applied heat converts the water in the solution into vapor. The vapor

is removed from the rest of the solution and is condensed while the now concentrated

solution is either fed into a second evaporator or is removed. The evaporator as a

machine generally consists of four sections. The heating section contains the heating

medium, which can vary. Steam is fed into this section. The most common medium

consists of parallel tubes but others have plates or coils. The concentrating and

separating section removes the vapor being produced from the solution. The

condenser condenses the separated vapor, then the vacuum or pump provides

pressure to increase circulation.

1.4 TYPES OF EVAPORATORS USED TODAY

1.4.1 NATURAL FORCED CIRCULATION EVAPORATOR

Natural circulation evaporators are based on the natural circulation of the product

caused by the density differences that arise from heating. In an evaporator using

tubing, after the water begins to boil, bubbles will rise and cause circulation,

facilitating the separation of the liquid and the vapor at the top of the heating tubes.

The amount of evaporation that takes place depends on the temperature difference

between the steam and the solution. Problems can arise if the tubes are not well-

immersed in the solution. If this occurs, the system will be dried out and circulation

compromised. In order to avoid this, forced circulation can be used by inserting a

pump to increase pressure and circulation. Forced circulation occurs when hydrostatic

head prevents boiling at the heating surface. A pump can also be used to avoid fouling

that is caused by the boiling of liquid on the tubes; the pump suppresses bubble

formation. Other problems are that the residing time is undefined and the

consumption of steam is very high, but at high temperatures, good circulation is easily

achieved.

1.4.2 FALLING FILM EVAPORATOR Main article: Falling film evaporator

This type of evaporator is generally made of long tubes meters in length which are

surrounded by steam jackets. The uniform distribution of the solution is important

when using this type of evaporator. The solution enters and gains velocity as it flows

downward. This gain in velocity is attributed to the vapor being evolved against the

heating medium, which flows downward as well. This evaporator is usually applied to

highly viscous solutions so it is frequently used in the chemical, food, and

fermentation industry is Rising film (Long Tube Vertical) evaporator

A rising film evaporator to In this type of evaporator, boiling takes place inside the

tubes, due to heating made (usually by steam) outside the same. Submergence is

therefore not desired; the creation of water vapor bubbles inside the tube creates an

accessional flow enhancing the heat transfer coefficient. This type of evaporator is

therefore quite efficient, the disadvantage being be prone to quick scaling of the

internal surface of the tubes. This design is then usually applied to clear, non-salting

solutions. Tubes are usually quite longsome times a small recycle is provided. Sizing

this type of evaporator is usually a delicate task, since it requires a precise evaluation

of the actual level of the process liquor inside the tubes. Recent applications tend to

favor the falling film pattern rather than this one.

1.4.3 PLATE EVAPORATOR

Plate evaporators have a relatively large surface area. The plates are usually

corrugated and are supported by frame. During evaporation, steam flows through the

channels formed by the free spaces between the plates. The steam alternately climbs

and falls parallel to the concentrated liquid. The steam follows a co-current, counter-

current path in relation to the liquid. The concentrate and the vapor are both fed into

the separation stage where the vapor is sent to a condenser. Plate evaporators are

frequently applied in the dairy and fermentation industry rise since they have spatial

flexibility. A negative point of this type of evaporator is that it is limited in its ability to

treat viscous or solid-containing products.

1.5 MAIN ARTICLE: MULTIPLE-EFFECT EVAPORATOR

Unlike single-stage evaporators, these evaporators can be made of up to seven

evaporator stages or effects. The energy consumption for single-effect evaporators is

very high and makes up most of the cost for an evaporation system. Putting together

evaporators saves heat and thus requires less energy. Adding one evaporator to the

original decreases the energy consumption to 50% of the original amount. Adding

another effect reduces it to 33% and so on. A heat saving equation can be used to

estimate how much one will save by adding a certain amount of effects.

The number of effects in a multiple-effect evaporator is usually restricted to seven

because after that, the equipment cost starts catching up to the money saved from

the energy requirement drop.

There are two types of feeding that can be used when dealing with multiple-effect

evaporators. Forward feeding takes place when the product enters the system

through the first effect, which is at the highest temperature. The product is then

partially concentrated as some of the water is transformed into vapor and carried

away. It is then fed into the second effect which is a little lower in temperature. The

second effect uses the heated vapor created in the first stage as its heating source

(hence the saving in energy expenditure). The combination of lower temperatures and

higher viscosities in subsequent effects provides good conditions for treating heat-

sensitive products like enzymes and proteins. In using this system, an increase in the

heating surface area of subsequent effects is required. Another way to proceed is by

using backward feeding. In this process, the dilute products is fed into the last effect

with has the lowest temperature and is transferred from effect to effect with the

temperature increasing. The final concentrate is collected in the hottest effect which

provides an advantage in that the product is highly viscous in the last stages so the

heat transfer is considerably better.

Technical problems can arise during evaporations, especially when the process is

applied to the food industry. Some evaporators are sensitive to differences in viscosity

and consistency of the dilute solution. These evaporators could work inefficiently

because of a loss of circulation. The pump of an evaporator may need to be changed if

the evaporator needs to be used to concentrate a highly viscous solution. Fouling also

occurs when hard deposits form on the surfaces of the heating mediums in the

evaporators. In foods, proteins and polysaccharides can create such deposits that

reduce the efficiency of heat transfer. Foaming can also create a problem since dealing

with the excess foam can be costly in time and efficiency. Antifoam agents are to be

used, but only a few can be used when food is being processed. Corrosion can also

occur when acidic solutions such as citrus juices are concentrated. The surface

damage caused can shorten the long-life of evaporators. Quality and flavor of food can

also suffer during evaporation. Overall, when choosing an evaporator, the qualities of

the product solution need to be taken into heavy consideration.

For more details on this topic, see Evaporator marine large ships usually carry

evaporating plants to produce fresh water, thus reducing their reliance on shore-

based supplies. Steam ships must be able to produce high quality distillate in order to

maintain boiler-water levels. Diesel engine ships often utilize waste heat as an energy

source for producing fresh water. In this system, the engine cooling water is passed

through a heat exchanger, where it is cooled by concentrated sea water brine.

Because the cooling water which is chemically treated fresh waterish at a temperature

of degrees it would not be possible to flash off any water vapors unless the pressure in

the heat exchanger vessel was dropped. To alleviate this problem, a brine-air ejector

venture is used to create a vacuum inside the vessel. Partial evaporation is achieved

and the vapor passes through a demister before reaching the condenser section. Sea

water is pumped through the condenser section to cool the vapor sufficiently to

precipitate it. The distillate gathers in a tray, from where it is pumped to the storage

tanks. A salino-meter monitors salt content and diverts the flow of distillate from the

storage tanks if the salt content exceeds the alarm limit. Sterilization is carried out

after the evaporator. Evaporators are usually of the shell-and-tube type known as an

Atlas Plant or of the Plate Type such as the type designed by Alfa Laval Temperature,

production and vacuum are controlled by regulating the system valves. Sea water

temperature can interfere with production, as can fluctuations in engine load. For this

reason, the evaporator is adjusted as seawater temperature changes, and shut down

altogether when the ship is manoeuvring. An alternative in some vessels, such as naval

ships and passenger ships, is the use of the Reverse Osmosis principle for fresh water

production instead of evaporators.

1.6 PROBLEM STATEMENT Currently all laboratories devices have the disadvantage of high cost the film rotary

evaporator device is designed to minimize the cost and separate solvent from

chemical liquid but it is not available in Sudan

1.7 OBJECTIVES 1- To design temperature control for film rotary evaporator.

2- To design speed temperature control for film rotary evaporator.

3- Application of electronic in B.M.E.

4- Collection of different subject of B.M.E.

5- Do ministration of acknowledge skills.

6- Testifying of practice.

7- Justification software. 8- Minimize the cost

CHAPTER TWO

LITERATURE REVIEW

2. LITERATURE REVIEW

The rotary evaporator is a device for gently and efficiently evaporating solvents from a mixture. It consists of a heated rotating vessel (usually a large flask) which is maintained under a vacuum though a tube connecting it to a condenser. The rotating flask is heated by partial emersion in a hot water bath. The flask's rotation provides improved heat transfer to the contained liquid; the rotation also strongly reduces the occupancy of 'bumps' caused by superheating of the liquid. The solvent vapor leave the flask by the connecting tube and are condensed in the condenser section. The condenser section is arranged so that the condensed vapor drain into another flask where they are collected. It is a very efficient way of rapidly removing large quantities of solvent. The major use in chromatography is the recovery of non- volatile solutes in preparative chromatography and the recovery of solvents for recycling. The device is also used for preparing coated supports for gas chromatography. For this application a weighed amount of support is placed in the flask, the required amount of stationary phase dissolved in excess of solvent is added to the solid and mixture tumble dried. This procedure has two advantages; as well as drying the support it ensures a very even distribution of the stationary phase throughout the support.

Product recovery when using normal phase solvents is best carried out by bulking the fractions and removing the solvent in a rotary evaporator under reduced pressure. For reverse phase solvents that have a high water content, recovery can be best achieved by passing the fraction through a reverse phase, C18, column of high capacity. The solute and solvent is adsorbed, and the solute and solvent content of the fraction can be recovered by displacement with another solvent, and the solute, now concentrated is recovered by evaporation. Solvent Hazard Unless solvent recycling can be employed, which is not always in the slurry method of coating, a weighed amount of the support is placed in the flask of a rotary evaporator and the required mass of stationary phase added. An appropriate volatile solvent is then added in sufficient quantity to produce a free-flowing slurry. The flask is then rotated at room temperature for ten minutes to ensure complete mixing. The rotating flask is then heated and the solvent removed by evaporation. When the packing appears dry, the material is then heated to about 150˚C in and oven to remove the final traces of solvent. This method of coating gives an, taken from the Raunds Area site in the Nene Valley North hamptonshire UK. Samples, about 2 g in weight, were scraped free from soil and ground to a fine powder in a carefully degreased pestle and mortar. A know mass of n-heptadecane was added as a standard, and the powder extracted twice with 10 ml of a mixture of chloroform and methanol (2+1) with supersonic agitation. After each extraction the mixture was centrifuged to remove the suspended solid. The extract was concentrated in a rotary evaporator and finally dried in a gentle stream of nitrogen. Trimethylester and other derivatives were prepared by heating aliquots with excess N, O-bis(trimethylsilyl) tri fluoroacetamide GC separations followed by negative ion chemical ionization mass spectrometry has been shown to be a very sensitive method for monitoring pesticide contamination of vegetable foodstuff (28). The procedure used was as follows. 15 g

of the material was extracted with 60 ml of ethyl acetate and 13 g of anhydrous sodium sulphate and separated. The residue was then extracted with a further 30 ml of ethyl acetate and the two extracts combined. A 30 ml aliquot was evaporated to dryness in a rotary evaporator at 60 C. The residue was then dissolved in 5 ml of ethyl acetate and was used directly for analysis. The technique was tested using pepper extracts spiked with chlorothalonil and procymidone. 2 ml samples were injected onto a capillary column 30 m long, 0.25 mm I.D. carrying a film 0,25 mm thick of crosslinked 5% diphenyl-95% dimethyl siloxane Initially the column was held at 70 C for 1 minute and then programmed to 180 C at 35 C per minute, then to 240 C at 10 C per minute

2.1 HOW EVAPORATOR WORKS An evaporator in a refrigeration system works by passing warm air over its coils. The warmth of the air heats the liquid refrigerant inside, causing it to boil into gas. At the same time, the air loses its heat and turns cold. It is heated by the surrounding and is passed through again and again until the surrounding is the same temperature as the liquid refrigerant. Then, the system shuts off, or cycles back, depending on the metering device.

2.2 MOTOR CONTROLLER

predetermined manner the performance of an electric motor A motor controller might include a motor controller is a device or group of devices that serves to govern in some manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and faults.

2.3 APPLICATIONS

Every electric motor has to have some sort of controller. The motor controller will have differing features and complexity depending on the task that the motor will be performing.

The simplest case is a switch to connect a motor to a power source, such as in small appliances or power tools. The switch may be manually operated or may be a relay or contactor connected to some form of sensor to automatically start and stop the motor. The switch may have several positions to select different connections of the motor. This may allow reduced-voltage starting of the motor, reversing control or selection of multiple speeds. Overload and overcurrent protection may be omitted in very small motor controllers, which rely on the supplying circuit to have overcurrent protection. Small motors may have built-in overload devices to automatically open the circuit on overload. Larger motors have a protective overload relay or temperature sensing relay included in the controller and fuses or circuit breakers for

overcurrent protection. An automatic motor controller may also include limit switches or other devices to protect the driven machinery.

More complex motor controllers may be used to accurately control the speed and torque of the connected motor (or motors) and may be part of closed loop control systems for precise positioning of a driven machine. For example, a numerically controlled lathe will accurately position the cutting tool according to a preprogramed profile and compensate for varying load conditions and perturbing forces to maintain tool position.

2.3.1 TYPES OF MOTOR CONTROLLERS

Motor controllers can be manually, remotely or automatically operated. They may include only the means for starting and stopping the motor or they may include other functions.

An electric motor controller can be classified by the type of motor it is to drive such as permanent magnet, servo, series, separately excited, and alternating current.

A motor controller is connected to a power source such as a battery pack or power supply, and control circuitry in the form of analogue or digital input signals.

2.3.2 MOTOR STARTERS Motor soft starter

A small motor can be started by simply plugging it into an electrical receptacle or by using a switch or circuit breaker. A larger motor requires a specialized switching unit called a motor starter or motor contactor. When energized, a direct on line (DOL) starter immediately connects the motor terminals directly to the power supply. Reduced-voltage, star-delta or soft starters connects the motor to the power supply through a voltage reduction device and increases the applied voltage gradually or in steps.[2][3][4] In smaller sizes a motor starter is a manually-operated switch; larger motors, or those requiring remote or automatic control, use magnetic contactors. Very large motors running on medium voltage power supplies (thousands of volts) may use power circuit breakers as switching elements.

A direct on line (DOL) or across the line starter applies the full line voltage to the motor terminals. This is the simplest type of motor starter. A DOL motor starter also contain protection devices, and in some cases, condition monitoring. Smaller sizes of direct on-line starters are manually operated; larger sizes use an electromechanical contactor (relay) to switch the motor circuit. Solid-state direct on line starters also exist.

A direct on line starter can be used if the high inrush current of the motor does not cause excessive voltage drop in the supply circuit. The maximum size of a motor allowed on a direct on line starter may be limited by the supply utility for this reason.

For example, a utility may require rural customers to use reduced-voltage starters for motors larger than 10 kW.[6]

DOL starting is sometimes used to start small water pumps, compressors, fans and conveyor belts. In the case of an asynchronous motor, such as the 3-phase squirrel-cage motor, the motor will draw a high starting current until it has run up to full speed. This starting current is typically 6-7 times greater than the full load current. To reduce the inrush current, larger motors will have reduced-voltage starters or variable speed drives in order to minimise voltage dips to the power supply.

A reversing starter can connect the motor for rotation in either direction. Such a starter contains two DOL circuits—one for clockwise operation and the other for counter-clockwise operation, with mechanical and electrical interlocks to prevent simultaneous closure.[6] For three phase motors, this is achieved by transposing any two phases. Single phase AC motors and direct-current motors require additional devices for reversing rotation.

2.3.3 REDUCED VOLTAGE STARTERS

Two or more contactors may be used to provide reduced voltage starting of a motor. By using an autotransformer or a series inductance, a lower voltage is present at the motor terminals, reducing starting torque and inrush current. Once the motor has come up to some fraction of its full-load speed, the starter switches to full voltage at the motor terminals. Since the autotransformer or series reactor only carries the heavy motor starting current for a few seconds, the devices can be much smaller compared to continuously-rated equipment. The transition between reduced and full voltage may be based on elapsed time, or triggered when a current sensor shows the motor current Adjustable-speed drives

2.3.4 MAIN ARTICLE: ADJUSTABLE-SPEED DRIVE

An adjustable-speed drive (ASD) or variable-speed drive (VSD) is an interconnected combination of equipment that provides a means of driving and adjusting the operating speed of a mechanical load. An electrical adjustable-speed drive consists of an electric motor and a speed controller or power converter plus auxiliary devices and equipment. In common usage, the term “drive” is often applied to just the controller.

2.3.5 INTELLIGENT CONTROLLERS

An Intelligent Motor Controls (IMC) uses a microprocessor to control power electronic devices used for motor control. IMCs monitor the load on a motor and accordingly match motor torque to motor load. This is accomplished by reducing the voltage to the AC terminals and at the same time lowering current and kvar. This can provide a measure of energy efficiency improvement for motors that run under light

load for a large part of the time, resulting in less heat, noise, and vibrations generated by the motor.

2.3.6 OVERLOAD RELAYS

A starter will contain protective devices for the motor. At a minimum this would include a thermal overload relay. The thermal overload is designed to open the starting circuit and thus cut the power to the motor in the event of the motor drawing too much current from the supply for an extended time. The overload relay has a normally closed contact which opens due to heat generated by excessive current flowing through the circuit. Thermal overloads have a small heating device that increases in temperature as the motor running current increases.

There are two types of thermal overload relay. In one type, a bi-metallic strip located close to a heater deflects as the heater temperature rises until it mechanically causes the device to trip and open the circuit, cutting power to the motor should it become overloaded. A thermal overload will accommodate the brief high starting current of a motor while accurately protecting it from a running current overload. The heater coil and the action of the bi-metallic strip introduce a time delay that affords the motor time to start and settle into normal running current without the thermal overload tripping. Thermal overloads can be manually or automatically resettable depending on their application and have an adjuster that allows them to be accurately set to the motor run current.

A second type of thermal overload relay uses a eutectic alloy, like a solder, to retain a spring-loaded contact. When too much current passes through the heating element for too long a time, the alloy melts and the spring releases the contact, opening the control circuit and shutting down the motor. Since eutectic alloy elements are not adjustable, they are resistant to casual tampering but require changing the heater coil element to match the motor rated current.[6]

Electronic digital overload relays containing a microprocessor may also be used, especially for high-value motors. These devices model the heating of the motor windings by monitoring the motor current. They can also include metering and communication functions.

2.3.7 LOSS OF VOLTAGE PROTECTION

Starters using magnetic contactors usually derive the power supply for the contactor coil from the same source as the motor supply. An auxiliary contact from the contactor is used to maintain the contactor coil energized after the start command for the motor has been released. If a momentary loss of supply voltage occurs, the contactor will open and not close again until a new start command is given. this prevents restarting of the motor after a power failure. This connection also provides a small degree of protection against low power supply voltage and loss of a phase. However since contactor coils will hold the circuit closed with as little as 80% of

normal voltage applied to the coil, this is not a primary means of protecting motors from low voltage operation.[6]

A motor control center (MCC) is an assembly of one or more enclosed sections having a common power bus and principally containing motor control units. Motor control centers are in modern practice a factory assembly of several motor starters. A motor control center can include variable frequency drives, programmable controllers, and metering and may also be the electrical service entrance for the building. Motor control centers are usually used for low voltage three-phase alternating current motors from 208 V to 600 V. Medium-voltage motor control centers are made for large motors running at 2300 V to around 15000 V, using vacuum contactors for switching and with separate compartments for power switching and control.

Motor control centers have been used since 1950 by the automobile manufacturing industry which used large numbers of electric motors. Today they are used in many industrial and commercial applications. Where very dusty or corrosive processes are used, the motor control center may be installed in a separate air-conditioned room, but often an MCC will be on the factory floor adjacent to the machinery controlled.

A motor control center consists of one or more vertical metal cabinet sections with power bus and provision for plug-in mounting of individual motor controllers. Very large controllers may be bolted in place but smaller controllers can be unplugged from the cabinet for testing or maintenance. Each motor controller contains a contactor or a solid-state motor controller, overload relays to protect the motor, fuses or a circuit breaker to provide short-circuit protection, and a disconnecting switch to isolate the motor circuit. Three-phase power enters each controller through separable connectors. The motor is wired to terminals in the controller. Motor control centers provide wire ways for field control and power cables.

Each motor controller in an MCC can be specified with a range of options such as separate control transformers, pilot lamps, control switches, extra control terminal blocks, various types of bi-metal and solid-state overload protection relays, or various classes of power fuses or types of circuit breakers. A motor control center can either be supplied ready for the customer to connect all field wiring, or can be an engineered assembly with internal control and interlocking wiring to a central control terminal panel board or programmable controller.

Motor control centers (MCC) usually sit on floors, which are often required to have a fire-resistance rating. Firestops may be required for cables that penetrate fire-rated floors and walls.

2.3.8 SERVO CONTROLLERS There are many types of servo controllers

2.3.8.1 Type of Servo controllers

Main article: Servo drive

Main article: Servomechanism

2.3.8.2 Servo controllers is a wide category of motor control. Common features are:

Precise closed loop position control

Fast acceleration rates

Precise speed control

2.3.8.3 Servo motors may be made from several motor types, the most common being

brushed DC motor

brushless DC motors

AC servo motors

Servo controllers use position feedback to close the control loop. This is commonly implemented with encoders, resolvers, and Hall effect sensors to directly measure the rotor's position.

A servo may be controlled using pulse-width modulation (PWM). How long the pulse remains high (typically between 1 and 2 milliseconds) determines where the motor will try to position itself. Another control method is pulse and direction.

Other position feedback methods measure the back EMF in the undriven coils to infer the rotor position, or detect the Kick-Back voltage transient (spike) that is generated whenever the power to a coil is instantaneously switched off. These are therefore often called "sensor less" control methods.

2.3.9 STEPPER MOTOR CONTROLLERS

2.3.9.1 Main article: stepping motor

A stepper, or stepping, motor is a synchronous, brushless, high pole count, polyphase motor. Control is usually, but not exclusively, done open loop, i.e. the rotor position is assumed to follow a controlled rotating field. Because of this, precise positioning with steppers is simpler and cheaper than closed loop controls.

Modern stepper controllers drive the motor with much higher voltages than the motor nameplate rated voltage, and limit current through chopping. The usual setup is to have a positioning controller, known as an indexer, sending step and direction pulses to a separate higher voltage drive circuit which is responsible for commutation and current limiting.

CHAPTER THREE

THEORETICAL BACKGROUND

3. THEORETICAL BACKGROUND

3.1 DISTILLATION

The evaporation and subsequent collection of a liquid by condensation as a

means of purification: the distillation of water.

The extraction of the volatile components of a mixture by the condensation

and collection of the vapors that are produced as the mixture is heated:

petroleum distillation.

A distillate.

Vaporization of a liquid and subsequent condensation of the resultant gas back to liquid form. It is used to separate liquids from nonvolatile solids or solutes (e.g., water from salt and other components of seawater) or to separate two or more liquids with different boiling points (e.g., alcohol from fermented beers and wines). Many variations have been devised for industrial applications. An important one is fractional distillation, in which vapour from a heated liquid mixture is contacted by a series of trays and condensed liquid as it rises through a vertical column. The most volatile fraction of the mixture emerges from the top of the column, while less volatile fractions are withdrawn at lower points. In petroleum refining, this method is very efficient for removing naphtha, kerosene, and gas oils from crude oil. A method for separating homogeneous mixtures based upon equilibration of liquid and vapor phases. Substances that differ in volatility appear in different proportions in vapor and liquid phases at equilibrium with one another. Thus, vaporizing part of a volatile liquid produces vapor and liquid products that differ in composition. This outcome constitutes a separation among the components in the original liquid. Through appropriate configurations of repeated vapor-liquid contacting’s, the degree of separation among components differing in volatility can be increased many fold.

Figure ‎3-1 Distillate

Distillation is by far the most common method of separation in the petroleum, natural gas, and petrochemical industries. Its many applications in other industries include air fractionation, solvent recovery and recycling, separation of light isotopes such as hydrogen and deuterium, and production of alcoholic beverages, flavors, fatty acids, and food oils.

3.1.1 SIMPLE DISTILLATIONS

The two most elementary forms of distillation are a continuous equilibrium distillation and a simple batch distillation.

In a continuous equilibrium distillation, a continuously flowing liquid feed is heated or reduced in pressure (flashed) so as to cause partial vaporization. The vapor and liquid disengage while flowing through an open drum, and the products emerge as vapor and liquid streams. The vapor product can be condensed to form a liquid distillate. It is also possible to use a vapor feed, subjected to cooling and thereby partial condensation, again followed by disengagement of the resultant vapor and liquid in an open drum.

In a simple batch distillation, an entire batch of liquid is initially charged to a vessel and is then heated, typically by condensation of steam inside a metal coil within the vessel. Vapor is thereby continuously generated, and may be condensed to form a liquid distillate, which is collected. In the batch distillation, increments of vapor are formed in equilibrium with all liquid compositions ranging from the original to the final, whereas the continuous equilibrium distillation gives vapor in equilibrium with only the final liquid composition. Since the distillate consists primarily of the more volatile components and the feed liquid contains more of these substances than does the final liquid, the simple batch distillation gives a more enriched distillate than does the continuous equilibrium distillation.

3.1.2 FRACTIONAL DISTILLATION

Unless the vapor pressures of the species being separated are very dissimilar, a simple distillation does not produce highly purified products. Product purities can be increased by repeated partial vaporizations and condensations. The liquid from an initial continuous equilibrium distillation can be partially vaporized by additional heating. The remaining liquid can again be heated and partially vaporized, forming another liquid and so forth. Each liquid is progressively enriched in the less volatile substances. Similarly, successive partial condensations of the vapor fraction from the initial continuous equilibrium distillation produce vapor products successively enriched in the more volatile components. See also Vapor pressure.

The process involved in successive partial vaporizations and condensations would lead to only very small amounts of the most enriched products, along with numerous streams having intermediate compositions. A logical step is to recycle each of these intermediate streams to the prior vessel in the sequence of contactors. Recycling of

the intermediate vapors and liquids has another highly beneficial effect in that it negates the need for intermediate heaters and coolers. The resultant process is known as continuous fractional distillation. It is usually carried out in a distillation column, which is a simpler, more compact form of equipment than the cascade of vessels used in the process of recycling intermediate vapors and liquids. See also Distillation column.

3.2 VAPOR-LIQUID EQUILIBRIA

The separation accomplished in a distillation relates to the difference in composition of vapor and liquid phases at equilibrium. These relationships are the subject matter of phase-equilibrium thermodynamics. See also Chemical thermodynamics; Gas; Liquid.

The dependence of liquid-phase activity coefficients upon liquid composition is complex; consequently vapor-liquid equilibrium relationships can have quite different characteristics. For example, the two-component benzene-toluene system (curve A in the illustration) is a relatively ideal system, for which the activity coefficients are close to 1.0 over the liquid composition range. The mole fraction of benzene in the vapor is therefore always greater than that in the liquid, and the relative volatility has a nearly constant value of 2.4. Such a system can be separated readily into products of high purity by continuous fractional distillation.

3.2.1 TYPES OF BINARY VAPOR-LIQUID EQUILIBRIUM

Relationship; equilibrium vapor mole fraction of the more volatile (first named) component as a function of the liquid mole fraction of the more volatile component. The pressure is constant at 1 atm (101 kilopascals) for all systems. Curve A, benzene-toluene; B, acetone-carbon disulfide; C, acetone-chloroform; D, isobutyl alcohol-water.

3.3 HISTORY

Figure ‎3-2 Evaporation in the past

The first clear evidence of distillation comes from Greek alchemists working in Alexandria in the first century AD. Distilled water has been known since at least ca. 200 AD, when Alexander of Aphrodisias described the process. Arabs learned the process from the Egyptians and used it extensively in their chemical experiments

Clear evidence of the distillation of alcohol comes from the School of Salerno in the 12th century. Fractional distillation was developed by Tadeo Alderotti in the 13th century.

In 1500, German alchemist Hieronymus Braunschweig published Liber de arte destillandi (The Book of the Art of Distillation) the first book solely dedicated to the subject of distillation, followed in 1512 by a much expanded version. In 1651, John French published The Art of Distillation the first major English compendium of practice, though it has been claimed that much of it derives from Braunschweig's work. This includes diagrams with people in them showing the industrial rather than bench scale of the operation.

Figure ‎3-3 Evaporation in the past

Figure ‎3-4 Distillation

Figure ‎3-5 Old Ukrainian vodka still

As alchemy evolved into the science of chemistry, vessels called retorts became used for distillations. Both alembics and retorts are forms of glassware with long necks pointing to the side at a downward angle which acted as air-cooled condensers to condense the distillate and let it drip downward for collection. Later, copper alembics were invented. Riveted joints were often kept tight by using various mixtures, for instance a dough made of rye flour.[8] These alembics often featured a cooling system around the beak, using cold water for instance, which made the condensation of alcohol more efficient. These were called pot stills. Today, the retorts and pot stills have been largely supplanted by more efficient distillation methods in most industrial processes. However, the pot still is still widely used for the elaboration of some fine alcohols such as cognac, Scotch whisky, tequila and some vodkas. Pot stills made of various materials (wood, clay, stainless steel) are also used by bootleggers in various countries. Small pot stills are also sold for the domestic production of flower water or essential oils.

Early forms of distillation were batch processes using one vaporization and one condensation. Purity was improved by further distillation of the condensate. Greater volumes were processed by simply repeating the distillation. Chemists were reported to carry out as many as 500 to 600 distillations in order to obtain a pure compound.[10]

In the early 19th century the basics of modern techniques including pre-heating and reflux were developed, particularly by the French, then in 1830 a British Patent was issued to Aeneas Coffey for a whiskey distillation column, which worked continuously and may be regarded as the archetype of modern petrochemical units. In 1877, Ernest Solvay was granted a U.S. Patent for a tray column for ammonia distillation and the same and subsequent years saw developments of this theme for oil and spirits.

3.4 APPLICATIONS OF DISTILLATION

The application of distillation can roughly be divided in four groups: laboratory scale, industrial distillation, distillation of herbs for perfumery and medicinals (herbal distillate), and food processing. The latter two are distinctively different from the former two in that in the processing of beverages, the distillation is not used as a true purification method but more to transfer all volatiles from the source materials to the distillate.

The main difference between laboratory scale distillation and industrial distillation is that laboratory scale distillation is often performed batch-wise, whereas industrial distillation often occurs continuously. In batch distillation, the composition of the source material, the vapors of the distilling compounds and the distillate change during the distillation. In batch distillation, a still is charged (supplied) with a batch of feed mixture, which is then separated into its component fractions which are collected sequentially from most volatile to less volatile, with the bottoms (remaining least or non-volatile fraction) removed at the end. The still can then be recharged and the process repeated.

In continuous distillation, the source materials, vapors, and distillate are kept at a constant composition by carefully replenishing the source material and removing fractions from both vapor and liquid in the system. This results in a better control of the separation process.

3.5 GENERAL IMPROVEMENTS

Both batch and continuous distillations can be improved by making use of a fractionating column on top of the distillation flask. The column improves separation by providing a larger surface area for the vapor and condensate to come into contact. This helps it remain at equilibrium for as long as possible. The column can even consist of small subsystems ('trays' or 'dishes') which all contain an enriched, boiling liquid mixture, all with their own vapor-liquid equilibrium.

There are differences between laboratory-scale and industrial-scale fractionating columns, but the principles are the same. Examples of laboratory-scale fractionating columns (in increasing efficiency) include:

3.6 LABORATORY SCALE DISTILLATION

Laboratory scale distillations are almost exclusively run as batch distillations. The device used in distillation, sometimes referred to as a still, consists at a minimum of a reboiler or pot in which the source material is heated, a condenser in which the heated vapour is cooled back to the liquid state, and a receiver in which the concentrated or purified liquid, called the distillate, is collected. Several laboratory scale techniques for distillation exist (see also distillation types).

3.7 STEAM DISTILLATION

Like vacuum distillation, steam distillation is a method for distilling compounds which are heat-sensitive.[17] The temperature of the steam is easier to control than the surface of a heating element, and allows a high rate of heat transfer without heating at a very high temperature. This process involves bubbling steam through a heated mixture of the raw material. By Raoult's law, some of the target compound will vaporize (in accordance with its partial pressure). The vapor mixture is cooled and condensed, usually yielding a layer of oil and a layer of water.

Steam distillation of various aromatic herbs and flowers can result in two products; an essential oil as well as a watery herbal distillate. The essential oils are often used in perfumery and aromatherapy while the watery distillates have many applications in aromatherapy, food processing and skin care.

Figure ‎3-6 Dimethyl sulfoxide

Dimethyl sulfoxide usually boils at 189 °C. Under a vacuum, it distils off into the receiver at only 70 °C.

3.8 PERKIN TRIANGLE DISTILLATION SETUP 1 Stirrer bar/anti-bumping granules 2 Still pot 3 Fractionating column 4 Thermometer/Boiling point temperature 5 Teflon tap 1 6 Cold finger 7 Cooling water out 8 Cooling water in 9 Teflon tap 2 10 Vacuum/gas inlet 11 Teflon tap 3 12 Still receiver

Figure ‎3-7 Perkin triangle distillation setup

3.9 VACUUM DISTILLATION

Some compounds have very high boiling points. To boil such compounds, it is often better to lower the pressure at which such compounds are boiled instead of increasing the temperature. Once the pressure is lowered to the vapor pressure of the compound (at the given temperature), boiling and the rest of the distillation process can commence. This technique is referred to as vacuum distillation and it is commonly found in the laboratory in the form of the rotary evaporator.

This technique is also very useful for compounds which boil beyond their decomposition temperature at atmospheric pressure and which would therefore be decomposed by any attempt to boil them under atmospheric pressure.

CHAPTER FOUR

MATERIALS AND METHODOLOGY

4. MATERIALS AND METHODOLOGY

4.1 BLOCK DIAGRAM

The block diagram consists of three main component which is microcontroller,

Heater, Motor and other electronic devices lm 35 sensor. knobe, switchs, lcd to

display the parameters, led as indicators and power supply.

Main

SUPPLY

PWOR

SUPPLY

MIC

RO

CO

NTR

OLLER

DRIVER

MOTOR

TEMP

SENSOR

KNobe

SWITCHS

DRIVER

DRIE

INDICATOR

LCD

DISPLAY

HEATER

Figure ‎4-1 Block Diagram

4.2 CIRCUIT DIAGRAM

Figure ‎4-2 power supply

4.3 CIRCUIT DIAGRAM

Figure ‎4-3 control system

4.4 SOFTWARE OF CONTROL SYSTEM Bascom AVR was used to program the circuit. The code bellow shows the flow of the

program and the control of the system.

$regfile = "m16adef.dat"

$crystal = 1000000

Config Kbd = Portb , Debounce = 500 , Delay = 500

Config Portc.4 = Output

Config Portc.5 = Output

Config Portc.6 = Output

Config Portc.7 = Output

Config Portc.0 = Input

Config Portc.1 = Input

Config Portc.2 = Input

Config Portc.3 = Input

Config Timer1 = Timer , Prescale = 1024

Config Adc = Single , Prescaler = Auto , Reference = Avcc

Start Adc

Dim Channel1 As Byte , Channel0 As Byte , Q As Single , N As Byte , M As Single , L As Integer , P As

Integer

Channel1 = 1

Channel0 = 0

Config Lcdpin = Pin , Db4 = Portd.4 , Db5 = Portd.5 , Db6 = Portd.6 , Db7 = Portd.7 , E = Portd.3 , Rs =

Portd.2

Config Lcd = 16 * 2

Dim W As Word , V As Single , T As Single , Tmax As Single

Dim J As Single

Dim H1 As Integer , H2 As Integer , X As Integer , Y As Integer , Tempset As Single , K As Single , Timeset

As Single

Dim S As Single

Dim Ts As Single

Dim D As Word ,

Stop Timer1

Locate 1 , 1

Lcd "Mogtarbeen University"

Waitms 2000

Cls

Locate 1 , 1

Lcd "Rotary"

Waitms 2000

Cls

Locate 1 , 1

Lcd "Starting"

Waitms 1000

Tmax = 100

Q = 0

J = 50

Cls

Main:

Cls

Do

Portc.4 = 0

Portc.5 = 1

Portc.6 = 1

Portc.7 = 1

W = Getadc(0)

V = W * 5

V = V / 1024

T = V * 25

T = Int(t)

Locate 1 , 1

Lcd "TEMP=" ; T

Waitms 200

If Pinc.0 = 1 Then Gosub Tempseted

Loop

End

' end program

Tempseted:

Cls

Locate 1 , 1

Lcd "Please set temp"

Waitms 2000

While Pinc.0 = 0

W = Getadc(1)

V = W * 5

V = V / 1024

V = Int(v)

Tempset = V * 25

Waitms 200

Cls

Lcd "Set temp=" ; Tempset

Cls

Lcd "Seted temp=" ; Tempset

Waitms 250

If Pinc.1 = 1 Then Gosub Timeseted

Wend

Timeseted:

Cls

Locate 1 , 1

Lcd "Please set time"

Waitms 2000

While Pinc.1 = 0

D = Getadc(2)

Waitms 200

Cls

Timeset = D * 5

Timeset = Timeset / 1024

Timeset = Timeset * 12

Ts = Int(timeset)

Lcd "Time Set=" ; Ts

Wend

Cls

Lcd "Seted Time=" ; Ts

Waitms 2000

Gosub Operation

Operation:

Cls

While T <= Tempset

Start Timer1

K = Timer1

If K > 58593.75 Then Gosub Coun

Waitms 200

W = Getadc(0)

V = W * 5

V = V / 1024

T = V * 100

T = Int(t)

Locate 1 , 1

Lcd "TEMP=" ; T

Locate 2 , 1

Lcd "TIME=" ; Q

If T > Tmax Then Gosub Stopping

'Debounce Pinc.2 , 1 , Stopping , Sub

If Q = Ts Then Gosub Stopping

Waitms W

Portc.4 = 1

Portc.5 = 1

Portc.6 = 1

Portc.7 = 0

Wend

Waitms 200

Coun:

Q = Q + 1

Waitms 2000

Gosub Operation

Stopping:

While Pinc.1 = 0

Cls

Locate 1 , 1

Lcd "syetem stoped"

Locate 2 , 1

Lcd "Please Restart"

Waitms 200

Portc.4 = 0

Portc.5 = 1

Portc.6 = 1

Portc.7 = 1

Wend

Gosub Main

4.5 BILL OF QUANTITIES

Table ‎4-1 Bill of Quantities

Price Number Code Items

40 2 Board

15 1 DC. 12V Motor

15 1 LM35 Temprature sensor

2 1 Dry heater Heater

75 1 At mega 16 Microcontroller

15 1 Volt-1Amper15

Transformer

4 1 Bridge

75 1 2*16 LCD

5 1 Uln2003 Buffer

1 1 Photon diode Indicator Green

1 1 Photon diode Indicator Red

3 1 7812 Regulator

3 1 7805 Regulator

4 2 Capacitors

4 2 Capacitors

2 1 Capacitor

12 1 Relay

3 3 Resistors

3 3 Resistors

3 3 Push button Switches

CHAPTER FIVE

RESULTS AND DISCUSSIONS

5. DISCUSSIONS AND RESULTS

5.1 DISCUSSION The hardware of rotary film evaporator; control system designed and implemented.

The design consists of microcontroller, heater, motor and other electronic devices.

The Error! Reference source not found.shows the control system under test. Error!

ference source not found. shows the system in operating state. Error! Reference

source not found. the system after finishing the setting time.

Figure ‎5-1 the control system under the test

Figure ‎5-2 the system in operating state

Figure ‎5-3 the system after finishing the setting time

5.2 RESULTS Table ‎5-1 Results Summary

Item International Price (US$)

US Price (US$) Project estimate Price (US$)

Rotary film evaporator 960 – 1.130 1000-2000 50

The outcome of the project using the circuit has reduces the cost of the rotary film

evaporator to 50 US$.

CHAPTER SIX

CONCLUSIONS AND

RECOMMENDATIONS

6. CONCLUSIONS AND RECOMMENDATIONS

6.1 CONCLUSION We are looking forward to trusty and realize this project in two different methods

that is hardware and software to applied our ideal mentioned before and enjoying

our objectives. The control system designed and tested, the results are presented,

and we make our recommendation for future work.

6.2 RECOMMENDATIONS • For future work we recommend testing the control system in real time

application and make enhance for the system and we will to make the body

of the device in order to test many samples.

8. REFERENCES

(NFPA), T. N. F. P. A., 2017. National Electrical Code. s.l.:NFPA.

Anon., 2008. Article 430: Motors, Motor Circuits Controllers. In: National Electrical

Codes. Quincy: NFPA, p. 298.

Anon., n.d. Hei-VAP Rotary Evaporators. [Online]

Available at: http://www.heidolph-instruments.com/products/rotary-

evaporators/tabnavi/hei-vap-rotary-evaporators/

Anon., n.d. LabTech - Rotary Evaporator System. [Online]

Available at: https://www.environmental-expert.com/products/labtech-rotary-

evaporator-system-528362

Anon., n.d. Powerful Rotary Evaporators. [Online]

Available at: http://www.rotationsverdampfer.com/

Bradford, A. R., 1993. Crossword Solver's Dictionary. s.l.:Collins.

Siskind, C. S., 2006. Electrical Control Systems in Industry. s.l.:Glencoe/McGraw-Hill

School.

Sylvester, C. J., 1987. Solid-State AC Motor Controls: Selection and Application.

Newyork: Marcel Dekker.

APPENDIX

9. APPENDIX

Figure ‎9-1 ATmega16

ATmega16 is an 8-bit high performance microcontroller of Atmel’s Mega AVR family with low power consumption. Atmega16 is based on enhanced RISC (Reduced Instruction Set Computing) architecture with 131 powerful instructions. Most of the instructions execute in one machine cycle. Atmega16 can work on a maximum frequency of 16MHz. ATmega16 has 16 KB programmable flash memory, static RAM of 1 KB and EEPROM of 512 Bytes. The endurance cycle of flash memory and EEPROM is 10,000 and 100,000, respectively. ATmega16 is a 40 pin microcontroller. There are 32 I/O (input/output) lines which are divided into four 8-bit ports designated as PORTA, PORTB, PORTC and PORTD. ATmega16 has various in-built peripherals like USART, ADC, Analog Comparator, SPI, JTAG etc. Each I/O pin has an alternative task related to in-built peripherals. The following table shows the pin description of ATmega16.

Figure ‎9-2 Pin Diagram

Table ‎9-1 Pin Description

Pin No. Pin name Description Alternate Function

1 (XCK/T0) PB0 I/O PORTB, Pin 0 T0: Timer0 External Counter Input. XCK : USART External Clock I/O

2 (T1) PB1 I/O PORTB, Pin 1 T1:Timer1 External Counter Input

3 (INT2/AIN0) PB2 I/O PORTB, Pin 2 AIN0: Analog Comparator Positive I/P INT2: External Interrupt 2 Input

4 (OC0/AIN1) PB3 I/O PORTB, Pin 3 AIN1: Analog Comparator Negative I/P OC0 : Timer0 Output Compare Match Output

5 (SS) PB4 I/O PORTB, Pin 4

In System Programmer (ISP) Serial Peripheral Interface (SPI)

6 (MOSI) PB5 I/O PORTB, Pin 5

7 (MISO) PB6 I/O PORTB, Pin 6

8 (SCK) PB7 I/O PORTB, Pin 7

9 RESET Reset Pin, Active Low Reset

10 Vcc Vcc = +5V

11 GND GROUND

12 XTAL2 Output to Inverting Oscillator Amplifier

13 XTAL1 Input to Inverting Oscillator Amplifier

14 (RXD) PD0 I/O PORTD, Pin 0 USART Serial Communication Interface

15 (TXD) PD1 I/O PORTD, Pin 1

16 (INT0) PD2 I/O PORTD, Pin 2 External Interrupt INT0

17 (INT1) PD3 I/O PORTD, Pin 3 External Interrupt INT1

18 (OC1B) PD4 I/O PORTD, Pin 4 PWM Channel Outputs

19 (OC1A) PD5 I/O PORTD, Pin 5

20 (ICP) PD6 I/O PORTD, Pin 6 Timer/Counter1 Input Capture Pin

21 PD7 (OC2) I/O PORTD, Pin 7 Timer/Counter2 Output Compare Match Output

22 PC0 (SCL) I/O PORTC, Pin 0 TWI Interface

23 PC1 (SDA) I/O PORTC, Pin 1

24 PC2 (TCK) I/O PORTC, Pin 2

JTAG Interface 25 PC3 (TMS) I/O PORTC, Pin 3

26 PC4 (TDO) I/O PORTC, Pin 4

Pin No. Pin name Description Alternate Function

27 PC5 (TDI) I/O PORTC, Pin 5

28 PC6 (TOSC1) I/O PORTC, Pin 6 Timer Oscillator Pin 1

29 PC7 (TOSC2) I/O PORTC, Pin 7 Timer Oscillator Pin 2

30 AVcc Voltage Supply = Vcc for ADC

31 GND GROUND

32 AREF Analog Reference Pin for ADC

33 PA7 (ADC7) I/O PORTA, Pin 7 ADC Channel 7

34 PA6 (ADC6) I/O PORTA, Pin 6 ADC Channel 6

35 PA5 (ADC5) I/O PORTA, Pin 5 ADC Channel 5

36 PA4 (ADC4) I/O PORTA, Pin 4 ADC Channel 4

37 PA3 (ADC3) I/O PORTA, Pin 3 ADC Channel 3

38 PA2 (ADC2) I/O PORTA, Pin 2 ADC Channel 2

39 PA1 (ADC1) I/O PORTA, Pin 1 ADC Channel 1

40 PA0 (ADC0) I/O PORTA, Pin 0 ADC Channel 0

Figure ‎9-3 Electric motor

Various electric motors. A 9-volt PP3 transistor battery is in the center foreground for size comparison.

An electric motor is an electromechanical device that converts electrical energy into mechanical energy.

Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force. The reverse process, producing electrical energy from mechanical energy, is done by generators such as an alternator or a dynamo; some electric motors can also be used as generators, for example, a traction motor on a vehicle may perform both tasks. Electric motors and generators are commonly referred to as electric machines.

Electric motors are found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives. They may be powered by direct current, e.g., a battery powered portable device or motor vehicle, or by alternating current from a central electrical distribution grid or inverter. The smallest motors may be found in electric wristwatches. Medium-size motors of highly standardized dimensions and characteristics provide convenient mechanical power for industrial uses. The very largest electric motors are used for propulsion of ships, pipeline compressors, and water pumps with ratings in the millions of watts. Electric motors may be classified by the source of electric power, by their internal construction, by their application, or by the type of motion they give.

The physical principle behind production of mechanical force by the interactions of an electric current and a magnetic field, Faraday's law of induction, was discovered by Michael Faraday in 1831. Electric motors of increasing efficiency were constructed from 1821 through the end of the 19th century, but commercial exploitation of electric motors on a large scale required efficient electrical generators and electrical distribution networks. The first commercially successful motors were made around 1873.

Some devices convert electricity into motion but do not generate usable mechanical power as a primary objective and so are not generally referred to as electric motors. For example, magnetic solenoids and loudspeakers are usually described as actuators and transducers, respectively, instead of motors. Some electric motors are used to produce torque or force.

History and development

Figure ‎9-4 Faraday's electromagnetic experiment, 1821

The conversion of electrical energy into mechanical energy by electromagnetic means was demonstrated by the British scientist Michael Faraday in 1821. A free-hanging wire was dipped into a pool of mercury, on which a permanent magnet was placed. When a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a close circular magnetic field around the wire. This motor is often demonstrated in school physics classes, but brine (salt water) is sometimes used in place of the toxic mercury. This is the simplest form of a class of devices called homopolar motors. A later refinement is the Barlow's wheel. These were demonstration devices only, unsuited to practical applications due to their primitive construction.[citation needed]

Figure ‎9-5 Jedlik's "electromagnetic self-rotor"

Jedlik's "electromagnetic self-rotor", 1827 (Museum of Applied Arts, Budapest. The historic motor still works perfectly today.

In 1827, Hungarian physicist Ányos Jedlik started experimenting with devices he called "electromagnetic self-rotors". Although they were used only for instructional

purposes, in 1828 Jedlik demonstrated the first device to contain the three main components of practical direct current motors: the stator, rotor and commutator. The device employed no permanent magnets, as the magnetic fields of both the stationary and revolving components were produced solely by the currents flowing through their windings.

The first electric motors

The first commentator-type direct current electric motor capable of turning machinery was invented by the British scientist William Sturgeon in 1832 Following Sturgeon's work, a commutator-type direct-current electric motor made with the intention of commercial use was built by Americans Emily and Thomas Davenport and patented in 1837. Their motors ran at up to 600 revolutions per minute, and powered machine tools and a printing press. Due to the high cost of the zinc electrodes required by primary battery power, the motors were commercially unsuccessful and the Davenports went bankrupt. Several inventors followed Sturgeon in the development of DC motors but all encountered the same cost issues with primary battery power. No electricity distribution had been developed at the time. Like Sturgeon's motor, there was no practical commercial market for these motors should work for any number of terms.

Figure ‎9-6 LCD

LCD 16x2. Data Sheet: LCD (Liquid Crystal Display) screen is an electronic display module and find a wide range of applications. A 16x2 LCD display is very basic module and is very commonly used in various devices and circuits. These modules are preferred over seven segments and other multi segment LEDs. The reasons being: LCDs are economical; easily programmable; have no limitation of displaying special & even custom characters (unlike in seven segments), animations and so on. A 16x2 LCD means it can display 16 characters per line and there are 2 such lines. In this LCD each character is displayed in 5x7 pixel matrix. This LCD has two registers, namely, Command and Data. The command register stores the command instructions given to the LCD. A command is an instruction given to LCD to do a predefined task like initializing it, clearing its screen, setting the cursor position, controlling display etc. The data register stores the data to be displayed on the LCD. The data is the ASCII value of the character to be displayed on the LCD.

Figure ‎9-7 Pin Diagram

Table ‎9-2 Pin Description

Pin No

Function Name

1 Ground (0V) Ground

2 Supply voltage; 5V (4.7V – 5.3V) Vcc

3 Contrast adjustment; through a variable resistor VEE

4 Selects command register when low; and data register when high

Register Select

5 Low to write to the register; High to read from the register Read/write

6 Sends data to data pins when a high to low pulse is given Enable

7

8-bit data pins

DB0

8 DB1

9 DB2

10 DB3

11 DB4

12 DB5

13 DB6

14 DB7

15 Backlight VCC (5V) Led+

16 Backlight Ground (0V) Led-

LM35.PDF Datasheet:

LM35 is a precision IC temperature sensor with its output proportional to the temperature (in oC). The sensor circuitry is sealed and therefore it is not subjected to oxidation and other processes. With LM35, temperature can be measured more accurately than with a thermistor. It also possess low self-heating and does not cause more than 0.1 oC temperature rise in still air.

The operating temperature range is from -55°C to 150°C. The output voltage varies by 10mV in response to every oC rise/fall in ambient temperature, i.e., its scale factor is 0.01V/ oC.

Figure ‎9-8 LM35 Temperature Sensor Image

Figure ‎9-9 Pin Diagram

Table ‎9-3 Pin Description

Pin No

Function Name

1 Supply voltage; 5V (+35V to -2V) Vcc

2 Output voltage (+6V to -1V) Output

3 Ground (0V) Ground

Figure ‎9-10 Diode bridge

Three bridge rectifiers. The size is generally related to the current handling capability.

Figure ‎9-11 bridge rectifiers

Diodes. The one on the bottom is a diode bridge.

Figure ‎9-12 Detail of a diode bridge, rated at 1000 Volts x 4 Amperes

Figure ‎9-13 A handmade diode bridge

A handmade diode bridge. The thick silver bar on the diodes indicates the cathode side of the diode.

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. When used in its most common application, for conversion of an alternating current (AC) input into direct current a (DC) output, it is known as a bridge rectifier. A bridge rectifier provides full-wave rectification from a two-wire AC input, resulting in lower cost and weight as compared to a rectifier with a 3-wire input from a transformer with a center-tapped secondary winding.[1]

The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input. The diode bridge circuit is also known as the Graetz circuit after its inventor, physicist Leo Graetz.

Basic operation

According to the conventional model of current flow originally established by Benjamin Franklin and still followed by most engineers today, current is assumed to flow through electrical conductors from the positive to the negative pole.[2] In actuality, free electrons in a conductor nearly always flow from the negative to the positive pole. In the vast majority of applications, however, the actual direction of current flow is irrelevant. Therefore, in the discussion below the conventional model is retained.

In the diagrams below, when the input connected to the left corner of the diamond is positive, and the input connected to the right corner is negative, current flows from the upper supply terminal to the right along the red (positive) path to the output, and returns to the lower supply terminal via the blue (negative) path.

Figure ‎9-14 A handmade diode bridge Diagram

When the input connected to the left corner is negative, and the input connected to the right corner is positive, current flows from the lower supply terminal to the right along the red (positive) path to the output, and returns to the upper supply terminal via the blue (negative) path.

Figure ‎9-15 A handmade diode bridge Diagram

In each case, the upper right output remains positive and lower right output negative. Since this is true whether the input is AC or DC, this circuit not only produces a DC output from an AC input, it can also provide what is sometimes called "reverse polarity protection". That is, it permits normal functioning of DC-powered equipment when batteries have been installed backwards, or when the leads (wires) from a DC power source have been reversed, and protects the equipment from potential damage caused by reverse polarity.

Figure ‎9-16 AC, half-wave and full wave rectified signals

Prior to the availability of integrated circuits, a bridge rectifier was constructed from "discrete components", i.e., separate diodes. Since about 1950, a single four-terminal component containing the four diodes connected in a bridge configuration became a standard commercial component and is now available with various voltage and current ratings.

Output smoothing

For many applications, especially with single phase AC where the full-wave bridge serves to convert an AC input into a DC output, the addition of a capacitor may be desired because the bridge alone supplies an output of pulsed DC (see diagram below).

Figure ‎9-17 pulsed DC Output

The function of this capacitor, known as a reservoir capacitor (or smoothing capacitor) is to lessen the variation in (or 'smooth') the rectified AC output voltage waveform from the bridge. There is still some variation, known as "ripple". One explanation of 'smoothing' is that the capacitor provides a low impedance path to the AC component of the output, reducing the AC voltage across, and AC current through, the resistive load. In less technical terms, any drop in the output voltage and current of the bridge tends to be canceled by loss of charge in the capacitor. This charge flows out as additional current through the load. Thus the change of load current and voltage is reduced relative to what would occur without the capacitor. Increases of voltage correspondingly store excess charge in the capacitor, thus moderating the change in output voltage / current.

The simplified circuit shown has a well-deserved reputation for being dangerous, because, in some applications, the capacitor can retain a lethal charge after the AC power source is removed. If supplying a dangerous voltage, a practical circuit should include a reliable way to discharge the capacitor safely. If the normal load cannot be guaranteed to perform this function, perhaps because it can be disconnected, the circuit should include a bleeder resistor connected as close as practical across the capacitor. This resistor should consume a current large enough to discharge the capacitor in a reasonable time, but small enough to minimize unnecessary power waste.

The capacitor and the load resistance have a typical time constant τ = RC where C and R are the capacitance and load resistance respectively. As long as the load resistor is large enough so that this time constant is much longer than the time of

one ripple cycle, the above configuration will produce a smoothed DC voltage across the load.

When the capacitor is connected directly to the bridge, as shown, current flows in only a small portion of each cycle, which may be undesirable. The transformer and bridge diodes must be sized to withstand the current surge that occurs when the power is turned on at the peak of the AC voltage and the capacitor is fully discharged. Sometimes a small series resistor is included before the capacitor to limit this current, though in most applications the power supply transformer's resistance is already sufficient. Adding a resistor, or better yet, an inductor, between the bridge and capacitor can ensure that current is drawn over a large portion of each cycle and a large current surge does not occur.

In older times, this crude power supply was often followed by passive filters (capacitors plus resistors and inductors) to reduce the ripple further. When an inductor is used this way it is often called a choke. The choke tends to keep the current (rather than the voltage) more constant. Although the inductor gives the best performance, usually the resistor is chosen for cost reasons.

Nowadays with the wide availability of voltage-regulator chips, passive filters are less commonly used. The chips can compensate for changes in input voltage and load current, which the passive filter does not, and pretty much eliminate ripple. Some of these chips have fairly impressive power handling; in case this is not sufficient, they can be combined with a power transistor.

The idealized waveforms shown above are seen for both voltage and current when the load on the bridge is resistive. When the load includes a smoothing capacitor, both the voltage and the current waveforms will be greatly changed. While the voltage is smoothed, as described above, current will flow through the bridge only during the time when the input voltage is greater than the capacitor voltage. For example, if the load draws an average current of n Amps, and the diodes conduct for 10% of the time, the average diode current during conduction must be 10n Amps. This non-sinusoidal current leads to harmonic distortion and a poor power factor in the AC supply.

Some early console radios created the speaker's constant field with the current from the high voltage ("B +") power supply, which was then routed to the consuming circuits, (permanent magnets were then too weak for good performance) to create the speaker's constant magnetic field. The speaker field coil thus performed 2 jobs in one: it acted as a choke, filtering the power supply, and it produced the magnetic field to operate the speaker.

Figure ‎9-18 Foxtech mini 5V 1A switch regulator 7805

The mini switch regulator has similar size to a 7805 linear regulator but much bigger load capacity and much lower heat generation. You can use it to directly replace the linear regulator 7805 on your equipment, but notice you must at least at a 22 uf or bigger capacitor at the output.

Dimension: 11.6*10*5.8 mm

Module parameters

Module Properties: non-isolated step-down module (buck) Rectifier: synchronous rectification Input Voltage :6.5-20V (greater than 15V, output current 0.8A) Output voltage: 5V (accuracy plus or minus 1%) Output power: 5W Recommended input and output capacitors: input capacitance 10UF (ceramic), the output capacitor 22UF (ceramic) Maximum capacitive load: 1000UF Output Current: 1A Conversion efficiency: input voltage 6.5V 94% (maximum), input voltage 20V 85% (minimum) Operating temperature: Industrial grade (-40 ℃ to +85 ℃) (at 85 ℃ output current 0.5A) Maximum case working temperature: 100 ℃ Full load temperature rise: 50 ℃ Load regulation: ± 0.5% Voltage regulation rate: ± 0.5% Output ripple: load current 1A (typical application circuit, input ceramic capacitors

10UF, the output ceramic capacitors 22UF) If you need a lower ripple please add LC filter at the output Dynamic response speed: 5% 200uS Short circuit protection: current limiting (3A), since the resumption of Overheat protection: 150 ℃ reverse protection: Non Connection mode: soldered, SIP-3 package, compatible with LM7805.

A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), 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 were used extensively in telephone exchanges and early computers to perform logical operations.

A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called "protective relays".

Figure ‎9-19 Automotive-style miniature relay (dust cover is taken off)

Basic design and operation

Figure ‎9-20 Simple electromechanical relay

Figure ‎9-21 Small "cradle" relay

Small "cradle" relay often used in electronics. The "cradle" term refers to the shape of the relay's armature.

A simple electromagnetic relay consists of a coil of wire wrapped around a soft iron core, an iron yoke which provides a low reluctance path for magnetic flux, a movable iron armature, and one or more sets of contacts (there are two in the relay pictured). The armature is hinged to the yoke and mechanically linked to one or more sets of moving contacts. It is held in 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 contacts in the relay pictured is closed, and the other set is open. 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 to the yoke. This ensures continuity of the circuit between the moving contacts on the armature, and the circuit track on the printed circuit board (PCB) via the yoke, which is soldered to the PCB.

When an electric current is passed through the coil it generates a magnetic field that activates the armature, and the consequent movement of the movable contact(s) either makes or breaks (depending upon construction) a connection with a fixed contact. If the set of contacts was closed when the relay was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. 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 force is provided by a spring, but gravity is also used

commonly in industrial motor starters. Most relays are manufactured to operate quickly. In a low-voltage application this reduces noise; in a high voltage or current application it reduces arcing.

When the coil is energized with direct current, a diode is often placed across the coil to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a voltage spike dangerous to semiconductor circuit components. Some automotive relays include a diode inside the relay case. Alternatively, a contact protection network consisting of a capacitor and resistor in series (snubber circuit) may absorb the surge. If the coil is designed to be energized with alternating current (AC), a small copper "shading ring" can be crimped to the end of the solenoid, creating a small out-of-phase current which increases the minimum pull on the armature during the AC cycle.[1]

A solid-state relay uses a thyristor or other solid-state switching device, activated by the control signal, to switch the controlled load, instead of a solenoid. An optocoupler (a light-emitting diode (LED) coupled with a photo transistor) can be used to isolate control and controlled circuits.