The History Of Tribology Engineering Essay

philosophical modify is in journey in manufacturing. Today, engineers contemplate for media of reducing environmental and zeal missinges in medias and in their attritional contents. As a emanation, outthought attritional estimatenesss accounts for 1.5 – 2% of germinativeity waste in a recent jet engine, 9% of germinativeity waste in a piston airplane engine, up to 40-45% in a new auto engine (from the cosmos-persons lending moldingrs), past than 50% in railroads trains, and past than 80% of the domiciled germinativeity at textile enterprises[3].

Therefore, in an industrial cosmos-people, attritional estimatements are an imported stuff. Since germinativeity could be hinderd by attrition contraction, it is capacityy to estimate the attrition of symbolicals used in the assiduity. Frictional estimatement ways in distinct medias contend from the impression of that unmistakable media. In a Tribology Media (Tribomachine) where attrition is sensed using a admonish cell it is discriminating to allure an considerate and efficient attritional coefficient esteem. Tribology is the truth and technology of interacting demeanors in referring-to tumult. It incorporates the consider and impression of the principles of attrition, nonadjunction and channel. Generally, a Tribomedia uses a thought or attritional indicator to expose attritional coefficient of the sample used in kilogram (kg)[4]-[8]

Nowadays, there are elevated demands for tribological medias. This is due to the destiny of tribological scrutiny for new symbolicals. As a emanation of the unreliability of unversified models to foretell the tribological characteristics of symbolicals, cupelal employment befits the key segregate in determining the tribological properties of symbolicals. There are contendent images of tribological medias (tribo-machines) such as

1)Pin-on-disc

2) Block-on-ring

3) wet sand rubber rock

4) dry sand rubber rock,

5) sand/steel rock, etc[9].

In this emblem, the cognizance of Tribology and Electronics is combined to

develop a new way to estimate attritional coefficient. A postulates wages regularity was assumed and conjoined to a Fill on Disc (BOD) Tribology Media to criterion and cupel delay contendent admonishs applied .Thus, the regularity was programmed and conjoined to an LCD to allure attritional coefficient esteems in mili-Volts (mV).

The succeedingcited chapters demonstrate the contents on the emblem movablesed.

Example of a pin-on-disc tribo-media is loving adown:

Fig. 1. Diagram of a pin-on-disc tribo-machine. [5]

AIMS/ OBJECTIVES

To machination an electric table combineing the admonish cell delay an LCD to warner the attritional estimateness(s) duaccentuation sliding tumult.

Able to depend the motor from 0 to 2000RPM

Study and canvass the movables of admonish on the attritional coefficient using the new postulates wages regularity.

Capture attritional coefficient via an LCD integration duaccentuation a

Tribological criterions.

REPORT ORGANIZATION

This fame contains sections of chapters. It is divided into five chapters. The chapters are as follows:

Introduction

Literature re-examination

Methodology

Results and discussions

Conclusions

INTRODUCTION: It explicitly specifys the scope of the emblem, capacityy setting and/or supposition, describes specialized equipment and justifies emblem’s concern.

LITERATURE REVIEW: It caters dissecretive and beaaccentuation setting, cognizance and fixing from preceding scrutinyes. It to-boot serves as a majestic intimation throoughout the emblem.

METHODOLOGY: The examine re-examination discusses in content the machination ordainment of the media, making-ready of the samples and acts of the cupels.

RESULTS AND DISCUSSIONS: The emanations allureed are ordainmented and proposeed delay charts, graphs, tables and explanations.

CONCLUSIONS: The misentry gives the compendium of the estimate emblem delay some recommendations suggested.

The course confabulation (layout) of this fame is loving adown.

CHAPTER 1

INTRODUCTION

CHAPTER 2

LITERATURE REVIEW

CHAPTER 3

METHODOLOGY

CHAPTER 4

DISCUSSIONS AND CONCLUSIONS

CHAPTER 5

CONCLUSIONS

Fig. fame layout

CHAPTER 2

LITERATURE REVIEW

TRIBOLOGY

Tribology is the truth and technology of two interacting demeanors in referring-to tumult and of akin subjects and practices. The promise tribology is coined from two greek promises tribos and -logy. Tribos simply media “rubbing” opportunity -logy media consider. Therefore, tribology can be literally settled as the consider of attrition[ ]. It comprises the perfect gcomplete of attrition and channel including noncontact. It grasps corresponding interfacial interactions among estimates as polite as among estimates and mellifluouss. It is a new interdisciplinary avenue to subjects precedingly treated individually (inferior distinct categories such as adhesion, noncontact, attrition and channel, deportments, exfoliation) by distinct disciplines e.g. physics, chemistry, applied mathematics, estimate mechanics, liquescent mechanics, thermodynamics, ardor give, symbolicals truth, rheology, noncontact, media machination, exploit and reliability., metallurgy and physics, chemistry ,estimate mechanics ,liquescent mechanics ,thermodynamics, ardor give ,symbolical truth, nonadjunction ,media machination , [ ]. In any media there are manifold content segregates that direct tribology. They effect by attrition or sliding despite each other. Examples of such content segregates grasp deportments, gears, cams and tappets, tires, brakes, and piston accentuations. All of these contents feel two demeanors which end into adjunction, backance a admonish, and stir delay deference to each other. Rarely it is partial to feel low attrition, to hinder zeal, or elevated attrition, as in the circumstance of brakes. In ordain to obstruct the contents to channel, a obstruction way is fast nonadjunction is constantly applied.

Tribology in itself propose at the negotiative, superfluous and ecological optimization of tumult regularitys. The implementation of tribological cognizance emanations in a fetching down of channel and an optimization of attrition regularitys.

The operational reliability of medias and installations is aggravated (increased), disjunction exacts are corrupt, media and zeal are hinderd and emissions are to-boot corrupt []. For the goal of attrition and channel, the deferenceive notorious economies of the industrialized computeries tolerate missinges complete-year quantitying to approx. 5 % of the coarse notorious emanation (GDP) which are, e.g., for Germanifold approx. 35 billion Euros per year. When conveying out the fond tribological cognizance, it would be practicable to hinder 5 billion Euros in a year of such missinges [ ]. It is to-boot glorious that missinges emanationing from inexperience of tribology quantity in the United States to encircling 6% of its

coarse notorious emanation (or encircling $200 billion dollars per year in 1966). To-boot closely one-third of the cosmos-people’s zeal media in propose used evene as attrition conbreeze and channel guide cannot be aggravateemphasized for economic reasons and long-term analogy [].The rich remuneration of tribological cognizance emanations in capacityy savings respecting zeal and symbolical waste, disjunction and defence. Zeal and raw symbolical media are hinderd, environmental missing is avoided and security of labour is correctd.

THE HISTORY OF TRIBOLOGY

Tribology has constantly been environing to back man end his technological triumphs, from the use of fleshly fats to gloze the axles of his chariots, the use of ‘squeeze films’ of sand and mortar to considerately comcomsituation the abundant fabric fills in the pyramids, the use of the bow-drill to succor in the molding of movables and equipment, to the use of estimate tribological principles for moveing the abundant representations (e.g in antique egypt).

Fig. Painting from el-bersheh, circa 1880 bc, showing conveyance of a hercules representation.

The diagram aloft shows a man in fron of the representation emission mellifluous from a jar. some historians suggested that the mellifluous served dischargeal scopes, inasmuch-as some engineers suggested that this is one of the primary recorded circumstances of noncontact.

There were very few gaits in tribology from antique opportunitys until the Renaissance, due forein-great-measure to the arrestation of culture duaccentuation the Dark Ages. Environing the move of the 15th date, Leonard0 da Vinci cupelally inferred the laws of attrition.

These laws remained unpublicized until Amontons rediscovered them in the 17th date. Asegregate from these two events the fact of tribology had to abide until the thread of oil polites in the 19th date, simultaneously delay the annotation of railways, anteriorly the proximate ‘big march forward’ could be recorded. This was the deviseulation, by Osborne Reynolds, of the basic principles of liquescent film nonadjunction inveterate on the

‘physical wedge’ circumstances. From the moveo f the date completething was usually fairly delectable from the tribological poinot f vision until the 1940s, when the war imposed violent circumstancess upon equipment involving rotating mediary. The outgrowth of the gas turbine introduced a estimate new enjoin of tribological gists, involving demeanors which feel to depend at elevated despatchs, at elevated tours and in greatly corrosive atmospheres. By 1964 the demands of recent inpolicy arson engines, nuclear reactors, interinterintervenience probes , true fix disconnection, etc, involved that not sufficient was unreserved encircling the limits of noncontact, in segregateicular encircling channel.

TYPES OF TRIBOLOGY MACHINES ( TRIBOMACHINES)

In ordain to convey out a tribology criterion, a tribology media is used. There are contendent images of tribology media. These grasps;

Block on accentuation media (BOR)

Pin on disc or Fill on disc media (BOD)

Block on lifehither media(BOF)

ASTM G99

ASTM G77

ASTM G105

ASTM G137-95

ASTM B611 (sand/ rock criterion inferior wet/dry circumstancess)

Dry sand rubber rock (DSRW)

Wet sand rubber rock (WSRW)

BLOCK ON RING MACHINE (BOR)

This criterion way covers a laboratory act for determining the channel of symbolicals duaccentuation sliding using a pin-on-disk furniture. Materials are criterioned in pairs inferior nominally non-abrasive circumstancess. A admonish is applied to the accentuation as depends. This pneumatically admonished adapter permits criterions to b movablesed using the severe pin on fill criterion geodesy and to-boot using tally fill on the geodesy, delay a criterion fill admonished on either policy of rotating accentuation. The fill sample used has a lifehither delineation or conforming delineation. The conforming delineationd sample allows narrative beaaccentuation image criterions to be effected. The foremost areas of cupelal notice in using this image of furniture to estimate channel are illustrative. The coefficient of attrition may to-boot be fast.

Figure: Fill on Ring.

PIN ON DISC/ BLOCK ON DISC (BOD)

The pin-on-disk tribology media is a unfirm laboratory furniture for measuaccentuation the attrition and channel properties of cabals of metals and lubricants inferior chosen circumstancess of admonish, despatch and tour. The criterioner remains of a quiescent “pin” inferior an applied admonish in adjunction delay a rotating disc. Either the pin or the disc can be channel- and attrition-tested using the pin on disc criterioner. The pin is usually a tour thus-far it may be any geodesy that simulates the explicit impression frequentlyst demeanor. The pin manner is electrically individual from the admonish shine and thus from the disc sample. This allows a diminutive germinative to be applied athwart the adjunction from a Lunn-Furey Adjunction Hindrance Circuit. The relevance to the disc spindle is via a slip-ring. .Variations in the voltage athwart the adjunction are symbolical of the quantity of adjunction among the pin and disc samples granted that twain are conductors of electricity. Utmost voltage (typically 40 mV) corresponds to no adjunction (dissecretive tour) opportunity cipher voltage corresponds to liberal adjunction (secretive tour). The voltage saline conquer naturally vary

instantly duaccentuation a criterion so an RMS saline is used for recording scopes. In other promises a admonish cell which applys a automatic estimateness to an electrical saline fast to the pin on disc criterioner is used to estimate the disjunction of the attrition coefficient delay sliding extension. Sliding channel of the disc can be estimated succeeding the pin on disc criterion using a individual duty of equipment fast a Calo criterioner.

Figure: Pin on Disc.

BLOCK OF FLAT MACHINE (BOF)

FRICTION

As rerunning prior, tribology is the consider of attrition, channel and noncontact. This media that attrition, channel and nonadjunction are the constituents of tribology. In this complete of this emblem, the attritional estimatement is the deep focal substance. Attrition is the estimateness that opposes the referring-to tumult of two goals in adjunction. Attrition may be partial enjoy the breeze needed to plod delayout slipping and to-boot disadvatageous begoal attrition produces ardor in distinct segregates of medias. In this way some beneficial zeal is holloweyed as ardor zeal. Due to attrition we feel to demand past germinativeity in medias, tumult is done in medias and engines of automobiles appropriate past fuel which is a specie missing.

The attritional estimateness can be adapted using the deviseula which was brought by Amonton who balmy to settle the unversified correspondence among the attritional estimateness and the ordinary admonish. The deviseula is loving adown:

………………………………………………………….. Equation ….

Where:

F_mathrm{f},is the estimateness demanded by attrition (in the circumstance of identity, the utmost practicable concretion of this estimateness).

mu,is the coefficient of attrition, which is an tentative attribute of the adjunctioning symbolicals,

F_mathrm{n}, is the ordinary estimateness demanded among the demeanors.

In most impressions the aim is to shorten attrition in ordain to narrow zeal waste and correct teachableness. Encircling 20 percent of the engine germinativeity of automobiles is appropriated in outthought attritional estimatenesss in the moveing segregates. Akin aspects are demeanor engineeaccentuation (the alteration of a content’s demeanor to gait its discharge, for outgrowth by directing a demeanor integument), demeanor bluntness, and rolling adjunction weary (where usual adjunctions goal weary to arise) [ ].

The rateality among attrition estimateness and ordinary admonish has led to the specification of “kinetic” and “static” coefficients of attrition. They are referred to as “properties” of unmistakable cabals of symbolicals. This avenue is greatly basic since the coefficients of attrition are contingent on parameters such as tour and sliding despatch and, in some circumstances there is no direct rateality among attrition estimateness and ordinary admonish. Recently, it has been fix that greatly of the characteristics of attrition are a emanation of the properties of severe demeanors in adjunction. Also, the defecate of attritional zeal (heat) aggravate diminutive localized areas has a telling govern on attrition and channels [ ].

FRICTION MEASUREMENT

STRAIN GAUGE

A defecate estimate is a emblem used to estimate the defecate of an goal. It was manufactured in 1938 by by Edward E. Simmons and Arthur C. Ruge. It is a primary sensing part for manifold images of sensors, including influence sensors, admonish cells, torque sensors, comcomsituation sensors, etc. It is a sensor whose hindrance varies delay applied estimateness. It applys estimateness, influence, stretch, capacity, etc., into a modify in electrical hindrance which can then be estimated. The bulk of defecate estimates are back images, fond in a expanded excellent of delineations and sizes to assist a abnormity of impressions. They remain of a plan of resistive back which is mounted on a supdeportment symbolical. The estimate is fast to the goal by a assiunwavering obstinate, such as cyanoacrylate. As the goal is blasted, the back is blasted, causing its electrical hindrance to modify.

Figure: Back Image of Defecate Gauge.

When a estimateness is applied to a organization, it emanations to importance and defecate that goals the exvigor of the organization modifys. Importance is a estimate of the average estimateness per part area of a demeanor delayin a deformable assemblage on which inpolicy estimatenesss act. In other promises, it is a estimate of the vigor of the inpolicy estimatenesss acting among segregateicles of a deformable assemblage athwart spurious inpolicy demeanors.

stress2

Fig: importance of a assemblage

While defecate is the quantity of deformation of a assemblage due to an applied estimateness. Past specifically, defecate (e) is settled as the interestal modify in exvigor of a assemblage when an exterior assemblage is applied.

Fig : defecate of a assemblage

Strain is adapted by dividing the sum deformation of the deviseer exvigor by the deviseer exvigor (L): …………………Eqn

Essentially, all defecate estimates are machinationed to apply automatic tumult into an electronic saline. A modify in capacitance, inductance, or hindrance is rateal to the defecate accustomed by the sensor. If a wire is held inferior stretch, it gets disregardly longer and its cross-sectional area is narrowd. This modifys its hindrance (R) in rate to the defecate sensitivity (S) of the wire’s hindrance. When a defecate is introduced, the defecate sensitivity, which is to-boot fast the estimate content (GF). The estimate content is the defecate estimate sensitivity to defecate. It is the reference of interestal modify in electrical hindrance to the interestal modify in exvigor (strain)

……………..Eqn

= …………………………Eqn

= ………………………….Eqn

Where ΔR is the modify in hindrance goald by defecate, R is the hindrance of the unreformed estimate, and ε is defecate.

The fictitious defecate estimate would modify hindrance barely due to the deformations of the demeanor to which the sensor is fast. However, in veritable impressions, tour, symbolical properties, the obstinate that bonds the estimate to the demeanor, and the inheritance of the metal all move the detected hindrance. Defecate estimates are constantly used in automatic engineeaccentuation scrutiny and outgrowth to estimate the importancees generated by mediary.

CIRCUIT MEASUREMENT

A illustrative defecate estimate hindrance is 120 Ohms (unstressed). This hindrance may modify barely a interest of a percent for the liberal estimateness enjoin of the estimate, which devises it very hard to use the defecate estimate unmatched as a estimatement regularity Thus. In ordain to devise it practicable to use the defecate estimate as a serviceable deed, greatly diminutive modifys in hindrance must be estimated delay elevated prevention. Hence, the defecate estimate is conjoined into a Wheatstone bridge tour delay a cabal of immodest locomotive estimates (liberal bridge), two estimates (half bridge), or, hither orderatically, a individual estimate (forbearance bridge). In the half and forbearance tours, the bridge is completed delay preciseness resistors.

THE WHEATSTONE BRIDGE

The Wheatstone bridge (delineation ) is one of the beneficial electrical bridge tours that may be used to estimate hindrance, capacitance or inductance[]. When the Wheatstone bridge is computeeractd, the resistors at the fit are particular to the resistors at the left (R1=R3 and R2=R4), this devises the voltage athwart the bridge to be similar to cipher. However, a disregard modify in hindrance on one of the resistors conquer goal the bridge to beend unbalanced thereby causing a voltage contendence appears.

In the tour shown adown it is obvious that the bridge can be imagined as two ballast tours (collected of R1, R2 and R3, R4) conjoined so that the judicious firm specify voltages are cancelled in the estimatement [ ]-[].

By employing voltage divider rule;

V1 = VEX ) ………………………………………….. Equation

V2 = VEX ( ………………………………………………..Equation

Vo = V1 – V2

Vo = VEX ( – VEX (

VO = VEX ( ……………………………………….Equation

Where VEX represents the stimulus or the input voltage to the admonish cell opportunity Vo represents the output voltage from the admonish cell which is to-boot fast the Signal.

Figure: Wheatstone bridge Tour Diagram.

LOAD CELL

HISTORY

Before the romance of the admonish cell, the automatic thought deed that was used is fast the lever. The lever effects in a devise of an similar arm computeeract that has a bar delay two pans clinging from each end and a fulcrum at the average of the bar upon which the bar can be in fashionweight (balance). It to-boot notably used by the antique Egyptians for measuaccentuation things enjoy persons and gold.

In 1843, an English physicist fast Sir Charles Wheatstone bequeathed a bridge

tour that could estimate electrical hindrances. The Wheatstone

bridge tour is fictitious for measuaccentuation the hindrance modifys that

arise in defecate estimates. Although the primary bonded hindrance wire defecate

estimate was open in the 1940s, it was not until recent electronics

caught up that the new technology became technically and superfluously

feasible. Since that opportunity, thus-far, defecate estimates feel proliferated twain

as automatic layer contents and in stand-unmatched admonish cells.

Today, exclude for unmistakable laboratories where preciseness automatic

balances are tranquil used, defecate estimate admonish cells manage the thought

industry. Pneumatic admonish cells are rarely used where immanent safety

and hygiene are desired, and hydraulic admonish cells are considered in

remote locations, as they do not demand a germinativeity minister. Defecate estimate

admonish cells propose accuracies from delayin 0.03% to 0.25% liberal layer and

are assiunwavering for closely all industrial impressions. [].

LOAD CELL FRICTION MEASUREMENT

A admonish cell (delineation ) is a transducer that applys a automatic estimateness into an electrical saline. This transmutation is disalike and arises in two phases. When intercourse delay a automatic ordainment, the estimateness or admonish substance sensed deforms a defecate estimate. The defecate estimate applys the defecate to electrical salines.

There are contendent configurations of a admonish cell. There are configurations of a individual defecate estimate, envelop defecate estimates and immodest defecate estimates. The electrical saline output is usually very diminutive. It is in-great-measure estimated in mill-volts and needs dilution by an deedation amplifier anteriorly it can be used.

CHAPTER 3

METHODOLOGY

The aim of this tour regularity machination is to baccentuation encircling a machination that captures attritional estimatenesss via LCD integration duaccentuation Tribological criterions and to increase

prevention and teachableness opportunity lection and recording the attrition estimatements from a Tribology media. The new regularity uses a PIC microcontroller to combine delay the Wheatstone bridge from defecate estimates (admonish cell) which acts as the input loving to the tour in attritional estimateness (R) devise and reads the output using an LCD that so-far reads estimatement emanations, as you can see in (Figure)

Figure 3.1 Regularity Layout Design.

Details on PIC Microcontroller

Peripheral Interface Controllers (PICs) are glorious delay developers due to their low exact, expanded accessibility, abundant user dishonorable, expanded-ranging assembly of impression notes, availability of low exact or uncounted outgrowth tools and serial programming (and re-programming delay flicker recollection) ability. All PICs mark Harvard structure, so the sequence interinterintervenience and the postulates interinterintervenience are disconnected. PIC sequence interinterintervenience is disclosedly implemented as EPROM, ROM, or flicker ROM []. In disclosed, exterior sequence recollection is not instantly addressable due to the failure of an exterior recollection interface. The excludeions are PIC17 and selecteded elevated pin compute PIC18 emblems [].

The PIC microcontroller used in this regularity is PIC16f877A (delineation ). The PIC16F877A marks 256 bytes of EEPROM postulates recollection, self-programming, an ICD, 2 Comparators, 8 channels of 10-bit Analog-to-Digital (A/D) applyer, 2 capture/compare/PWM discharges, the conpresent serial deportment can be configured as either 3-wire Serial Peripheral Interface (SPIâ„¢) or the 2-wire Inter-Integrated Tour (I²Câ„¢) bus and a Universal Aconpresent Receiver Transmitter (USART). All of these marks devise it fictitious for past gaitd roll A/D impressions in automotive, industrial, appliances and appropriater impressions.

Figure

In this emblem, the sequence used is in C programming. This microcontroller has 40 pins and the pin ordainments are as follows (Figure 3.2) [28]-[30];

– Pin 2 (RA0/AN0) is the input delay a voltage enjoin of 0 to 5V and utmost input voltage that can be fed is 5.5V.

– Pin 13 and 14 are conjoined to an oscillator. The discharge of an oscillator is to cater an considerate and unwavering intermittent clock saline to a microcontroller. The number of this clock saline is 20MH and determines how instantly the microcontroller executes it’s its advices. And two capacitors are needed to be conjoined to the oscillator for voltage direction.

– Pin 19, 20, 21, 22, 27, 28 29 and 30 are the postulates bus pins of the LCD (pin 7 to pin 14)

– Pin 11 and 32 discharge as germinativeity produce of 5V. It is to-boot conjoined to pin 2 and 15 of the LCD.

– Pin 12 and 30 discharge as germinativeity produce of 0V (Ground). And it is conjoined to pin 1 and 5 of the LCD.

– Pin 37(RB4) is conjoined to pin 4 of the LCD (RS) . This selecteds record, advice or postulates record.

– Pin 38 (RB5) is conjoined to pin 6 (E) of the LCD. The discharge of this LCD pin is to qualify lection or letter of postulates.

Diagram

CHAPTER 4

The tour was primary assumed on a breadtable at primary (figure). The breadtable is to-boot unreserved as the protoboard. The breadtable used is the solderhither breadboard. It does not demand soldering. It is reusable and thus can be used for present prototypes and cupeling delay tour machination past amply []. Succeeding it was grown that the schematic can be use, the erroneous was givered from the breadtable to the striptable (delineation ). The striptable has congruous strips of copper course on one policy. The courses are 2.54mm asegregate and there are holes complete 2.54mm. the striptable is used to devise a enduring soldered tour. However, it is very manageable to combine contents in the evil-doing settle since the holes are very diminutive and it is manageable to devise mistakes.

As there were some relevance fallacys on the tour table opportunity soldeaccentuation and the erroneous did not contemplate authoritative , as can be seen in (delineation ), the tour was assumed usually using a contendent breadtable (delineation ). However, a gist arisered opportunity reserved to combine the LCD to the tour. When the LCD was conjoined to the tour, the LCD cannot be exposeed. So the tour was cross-checked and fix no misdeed. It was then loving to the lab technicians to succor and troubleshoot but they fix no gist nor fallacy from the soldering. Two weeks were elapsed in reserved to delineation out the gist. So an “Enhanced 40 pins PIC initiate-up kit” (figure) to-boot unreserved as SK40C was bought to employment in settle of the failed assumed tour. The SK4OC has a configuration of 8.5cm x 5.5cm and is machinationed to propose an manageable to initiate table for PIC microcontroller user. The kit is machination to propose:

Industrial action PCB

Load program 

• completely fit for 40 pins 16F and PIC18F PIC

• With UIC00A (not graspd), program can be admonished in hither than 5 seconds

•   Past apt to use as it is diminutiveer than SK40B.

•   Utmost running is 1A.

2 x Programmable switch 

2 x LED indicator 

Finally, the tour employments and the LCD combines completely delay the tours.

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