takex america inc training manualtakex america inc training manual 5 | page 2. photoelectric sensors...

TakexAmericaIncTrainingManual

IndustrialAutomationGroup

Rayman

Rev1.0


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Tableofcontents1) SensingTechnology...............................................................................................................................3

2) PhotoelectricSensor..............................................................................................................................5

a) Basiccomponentsofphotosensor

b) Photoelectricsensormodesofdetection.......................................................................................6

c) Photoelectricselectionsensorquestion........................................................................................6

d) PhotoelectricsensorTypes.............................................................................................................7

i) ThrubeamSensors...................................................................................................................7

ii) Diffuse.......................................................................................................................................9

iii) BackgroundSuppression........................................................................................................10

iv) Convergent.............................................................................................................................11

v) Reflex......................................................................................................................................12

vi) PolarizedReflex......................................................................................................................14

vii) Fiberoptics............................................................................................................................15

viii) Laser........................................................................................................................................16

ix) Color.......................................................................................................................................18

x) Mark........................................................................................................................................19

xi) ChemicalandOilresistant......................................................................................................21

3) UltrasonicSensor.................................................................................................................................22

4) LightCurtains…………………………………………………………………………………………………………………………………..23

5) HotandColdMetalSensor..................................................................................................................24

6) Terminology.........................................................................................................................................26

7) ApplicationTable.................................................................................................................................31


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1.SensingTechnologyinIndustrialAutomationAsensorcanbethoughtofasanautomaticswitch.Sensorshavecontributedsignificantlytorecentadvancesinmanufacturingtechnology.Usingasensormakesaprocessorsystemmoreautomatedandremovestheneedforahumanoperatorinterventiontomonitorandcontrolthesituation.Inallthemajorindustrialdetectionapplications,sensorsareusedfordetectingpresence,absenceordistanceofpartsfromoratareferencepoint.Theobjecttobedetectedisreferredtoasatarget.Whenatargetisdetectedthefunctionofthesensoristochangeoutputwhichinturnwillturnaloadorturnofftheload.Applicationsofdetectionsensorareasfollows:

1. Verifyingtheparthavereachedacertainposition2. Countingparts3. Verifyingproperplacementofpartsinthesystem4. Makingsureedgeofpartiswithinthespecifiedposition5. Determiningthesizeoftheproduct6. Verifyinglevelofliquidormaterial

Thethreemaincategoriesofsensorsusedinindustrialautomationarelimitswitches,proximityswitches(Inductive,Capacitive,photoelectric)sensors,longdistancesensing(Photoelectric,ultrasonic)sensors.Limitswitchesuseamechanicalactuatorrequiringthesensortochangeitsoutputwhenobjectisphysicallytouchingtheswitch.Sensors,suchasphotoelectric,inductive,capacitive,andultrasonic,changetheoutputwhenobjectispresent,butnottouchingthesensor.Inadditiontotheadvantagesanddisadvantagesofeach,sensortechnologyhasbeenwellsuitedforcertainapplications.Thetableonnextpageelaboratesthedifferenceofthesensortechnology.


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Sensor Advantages Disadvantages ApplicationLimitSwitches

• Highcurrentcapacity

• Lowcost• Lowtech

• Requiresphysicalcontact

• Veryslowresponse• Contactbounce• Wearandtear

• Interlocking• Basicendof

travel

Inductive

• Resistancetoharshenvironments

• Verypredictable• Longlife• Easytoinstall

• Shortdistanceupto50mm

• Machinetoolindustry

• Sensingmetalobjects

Capacitive

• Detectsobjectsinsidecontainer

• Candetectno-metallictargets

• Verysensitivetoextremeenvironmentalchanges

• Levelsensing

Photoelectric

• Sensesallkindsofmaterials

• Longlife• Longestsensingrange

• Veryfastresponsetime

• Lenssubjecttocontamination

• Sensingrangeaffectedbycolorandreflectivityoftargetobject

• Packaging• Material

handling• Partsdetection

Ultrasonic

• Sensesallmaterials • Resolution• Repeatability• Sensitivetotemperaturechanges

• Anti-collision• Doors• Web• Level


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2.PhotoelectricSensorsPhotoelectricSensors(PS)uselighttodetectthepresenceorabsenceofanobject.AllPhoto-sensorsconsistofthesensor,controlunit,andoutput.Thesourceisalightemittingdiodethatemitsapowerfulbeamofinfraredorvisiblelight.Thedetectoristypicallyaphotodiodethatsensesthepresenceorabsenceoflight.2a.BasiccomponentsofPhotoSensor: SourceLED Photodetector Lens(forsourceanddetector) PowerCircuit(modulatoranddemodulator) Amplifier OutputCircuit

Amplifier

Power Supply

Modulator

Source LED

Photodetector

Lens

Target or Reflector

Demodulator

OutputDetector Amplifier


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2b.PhotoSensormodesofdetection:

Thru-beam(Throughbeam)Reflex(Retro-reflective/Polarizedretro-reflective)Diffuse(Diffusereflective)

KEYPOINT CONSIDERATION

Range Howfaristheobjecttobedetected?Environment Howdirtyordarkistheenvironment?Accessibility Whataccessibilityistheretobothsidesoftheobjecttobe

detected?Wiring Iswiringpossibletooneorbothsidesoftheobject.Sizeandcolor Whatisthesizeandthecoloroftheobject?Consistency Istheobjectconsistentinsize,shape,andreflectivity?Requirements Whatarethemechanicalandelectricalrequirements?Outputsignal WhatkindofoutputisneededLogicfunction Arelogicfunctionsneededatthesensingpoint?Integration Isthesystemrequiredtobeintegrated?

2c.PhotoelectricSelectionquestions Thru-beam,Reflex DiffuseSensingObject 1. Sizeandshape

2. Transparency(opaque,translucent,ortransparent)

3. Speedinft/sorm/s(V)

1. Sizeandshape2. Color3. Material4. Surface(texturedorglossy)5. Speedinft/sorm/s(V)

Sensor 1. Sensingdistance(L)2. Restrictionofshapeorsize

a. Sensorb. Retro-reflector

3. Mountinga. Numberofsensorsb. mountingpitch

4. Limitationofinstallation

1. Sensingdistance(L)2. Restrictionofshapeandsize3. Mounting

a. Numberofsensorsb. Pitch

4. Limitationofinstallation

Background 1. Color2. Material3. Surface

Environment 1. Ambienttemperature2. Water,oilorchemicals

presence3. Other

1. Ambienttemperature2. Water,oilorchemicals

presence3. Other


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2d.PhotoelectricSensorTypes Thru-beamSensing

Thethru-beammethodrequiresthatthesourceanddetectorarepositionedoppositeeachotherandthelightbeamissentdirectlyfromsourcetodetector.Whenobjectpassesbetweentheemitterandreceiver,thebeamisbroken,signalingdetectionofobject.Thru-beamdetectiongenerallyprovidesthelongestrangeofthethreemodesandprovideshigherpoweratshorterrangetopenetratesteam,dirtorothercontaminantsbetweensourceanddetector.Alignmentofthesourceanddetectormustbeaccurate.Theeffectivebeamareaisthatofthecolumnoflightthattravelsstraightbetweenthelenses.Becausethelightfromsourcesistransmitteddirectlytophotodetector,thethru-beamsensingoffersthefollowingbenefit.

1. Longestrangeforsensing2. Highestpossiblesignalstrength3. Greatestlight/darkcontrastratio4. Besttrippointrepeatability

Limitation

1. Theyrequirewiringofthetwocomponentsacrossdetectionzone2. Itmaybedifficulttoalignsourceanddetector3. Iftheobjectdetectedissmallerthantheeffectivebeamdiameter,anapertureoverthelensmayberequired

Source DetectorObject

Effective beam

Thru-beamSensor


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Applicationexamples:


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DiffuseSensingThediffusemethodrequiresthatthesourceanddetectorareinstalledonthesamesideoftheobjecttobedetectedandaimedatapointinfrontofthesensor.Whenanobjectpassesinfrontofthesourceanddetector,lightfromthesourceisreflectedfromtheobjectsurfacebacktothedetector,andobjectisdetected.Ingeneral,throughbeamsensoroffersthegreatestranges,followedbyreflex,thendiffusesensors.Theoptimumrangeforthediffuseandreflexsensorismoresignificantthanthemaximumrange.Theoptimumrangeisbestshownbyanexcessgainchart.Thedetectingzoneiscontrolledbythetype,texture,andcompositionoftheobject.Advantagesofdiffusesensing:

1. Installationandalignmentaresimpleandinvolveswiringononeside.2. Itcandetectdifferenceinsurfacereflectivity

Limitation:

1. Ithaslimitedsensingrange2. Thelight/darkcontrastsensingrangedependsonthetargetobject’ssurfacereflectivity.

Applicationexample

Led

Photo-diode

detectionzone

Obj

ect

Diffuse Reflective type sensor


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BackgroundSuppressionBackgroundsuppressionenablesdiffusesensortohaveexcessgaintoapredeterminedlimitandinsufficientexcessgainbeyondthatrangewhereitmightpickupobjectsinmotionandyieldfalsedetection.Byusingtriangularranging,sensordevelopershavecreatedasensorthatemitslightthatreflectsbackonthedetectorfromtwodifferenttargetpositions.Thesignalreceivedfromthedistanttargetissubtractedfromtheclosertarget,providinghighexcessgainfortheclosertarget.

Lens

phot

o d

iode

Led

Background Suppression type sensor

obje

ct

back

grou

nd

Characteristicsofbackgroundsuppressionsensor:NotaffectedbyBackground Resistancetosoilingoflens Lessinfluencetocolor,shapeandmaterialofobjects



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ConvergentSensingThisisaspecialvariationofdiffusesensing,whichusesadditionalopticstocreatesmall,intenseandwelldefinedimageatafixeddistanceinfrontofthesensorlens.Backgroundobjectswillnotfalsetriggeraconvergentreflectivesensorsincetheyarecross-eyedandcannotseepastacertainpoint.Convergentsensingisthefirstchoiceforsensingtransparentmaterialsthatremainwithinsensor’sdepthoffield.

LED

PHOTO DIODEDETECTION ZONE

Obj

ect

Obj

ect

obje

ct d

etec

ted

obje

ct n

ot d

etec

tedConvergent Reflective type sensor

ApplicationExample


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ReflexSensingThereflexmethodrequiresthatsourceanddetectorareinstalledatthesamesideoftheobjecttobedetected.Thelightbeamistransmittedfromthesourcetoaretro-reflectorthatreturnsthelighttodetector.Whenanobjectbreaksareflectedbeam,theobjectisdetected.Thereflexmethodiswidelyusedbecauseitisflexibleandeasytoinstallandprovidesbestcost-performanceratioofthreemethods.Theobjecttobedetectedmustbelessreflectivethanretroreflector.Sincethelighttravelsintwodirections(hencetwicethedistance),reflexsensorswillnotsenseasfarasthru-beamsensors.Howeverreflexsensorsofferapowerfulsensingsystemthatiseasytomountanddoesnotrequirethatelectricalwirebeingrunonbothsidesofthesensingarea.Themainlimitationofthesesensorsisthatashinysurfaceonthetargetobjectcantriggerfalsedetection.

Regular reflection (mirror)

Corner cube reflector reflectionRetroreflection

Diffuse reflection

Led

Photo-diode

Obj

ect

Retro-reflective Reflective type sensorRe

tro-re

flect

or


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Retro-reflectiveApplicationExample:


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PolarizedreflexPolarizedreflexsensorsuseapolarizingfilteroverthesourceanddetectorthatconditionsthelightsuchthatthephotoelectriccontrolseesonlylightreturnedfromthereflector.Apolarizedreflexsensorisusedinapplicationwhereshinysurfacessuchmetalorshrinkwrappedboxesmayfalsetriggerthecontrol.Polarizereflexsensingisachievedbycombiningsomeuniquepropertiesofpolarizerandretro-reflectors.Thepropertiesare,

1. Polarizerpasslightthatisalignedalongonlyoneplane2. Corner–cubereflectorsdepolarizelightasittravelsthroughthefaceoftheretro-reflector

Polarizedreflexsensorwillnotworkwithreflectivetapecontainingglassbeads.Also,shinyobjectwrappedwithclearplasticshrink-wrapwillpotentiallyfalsetriggerapolarizedreflexcontrol,sinceundercertainconditionstheseactascornercubereflector.Thepolarizedreflexsensorhasthefollowingadvantages:

1. Itisnotconfusedbythefirstsurfacereflectionsfromtargetobjects2. Ithasahighdark/lightcontrastratio3. Itiseasilyinstalledandaligned.Onesideofthesensingonlyneededbewired

Limitation:

1. Operatingrangeishalfthatofanon-polarizedsensorsincemuchofthesignalislostinthepolarizingfilters.2. Thesensorcanbefooledbyshinyobjectswrappedwithshrink-wrapmaterial.

Unpolarized light

Polarizing filter

Polarized light

Vertically polarized light

Horizontal polarizing filter

cannot pass vertical polarized light

Polarizing filterVertcally polarized light

Passess verticallypolarized light


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FiberOpticsSensingFiberopticssensorshavelargelybeenappliedtoapplicationinwhichtheirsmallsizehasmadethemconvenientreplacementforconventionalphotoelectricsensors.TheIndustryhassincediscoveredthattheprincipleoftotalinternalreflectionalsoappliestosmall-diameterglassandplasticfibersandthisleadtorapidgrowth.Becauseopticalfibersaresmallindiameterandflexible,theycanbendandtwistintoconfinedspaces.Alsobecausetheycontainnoelectronics,theycanoperateinmuchhighertemperatures-ashighas400˚Fandareasofhighvibration.Theyarelimitedbysensingdistances,whichtypicallyare80mmdiffusemodeandupto2000mminthru-beammode.Fiberopticscanleadtofalsedetectionbysmalldropofwaterordirt.Therearetwobasicsstylefiberopticassemblies,individualfiberopticsusedbyThru-beamsensorandbifurcatedfiberusedfordiffusedsensing.

Fiber optics sensor

Fiber optics cable

ApplicationExamples


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LaserSensorsLaserSensorsareespeciallysuitedforapplicationsthatrequirehighprecision.LaserSensorscombinethealignmentadvantagesofavisiblesensingbeamwiththeincreasedsensingrangeofalaser.TheyoperateClass1andClass2.ThesesensorsaccuratelydetectssmalltargetsandhavemuchlongersensingrangecomparedtostandardvisibleRedandinfraredsensors.Whenthelasersystemsareinstalled,itmustbeconsidered,e.g.bycorrectheightofinstallation,thatintentionaloraccidentallookingintothelaserbeamisprevented.Attheplaceofinstallationclearwarninglabelaretobeapplied.Additionalprotectivemeasuresanddetailedpersonnelinstructionsarenecessary.Theuseoftheunitsattheheightoftheheadorradiationindirectionswherepersonscanstayshouldbeavoided.Itisobviousthattheminimumdiameterofthelightspotisreachedatadefineddistance,thisdistanceisgiveninthedatasheetoftherespectiveunit.Thisdistanceisdeterminedbytheselectionoftheopticalelements.Itwouldbetoocomplicatedtomakethisdistancevariable.Letustakeananalogueexampleoutofthefieldofphotography.Ahighqualityzoomlensismuchmorecomplicatedandexpensivethanalenswith fixed focus.


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ColorSensors Colorsensordetectsthecolorofobjectswithoutmakingcontactbyhue,saturationandbrightness.Generally,itjudgeswhetherthecolorofanobjectisthesamewithregisteredcolor.Thesensorsemitlightandanalyzereflectionintothreecomponents(RED,GREENandBLUE)andidentifythecoloraccordingtotheproportionofthecomponents.TakexofferstwostyleofcolorsensorLEDandPassivecolorsensor.Typicalsensingdistance--13mm~33mm


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MarkSensorsAmarksensordetectsthebrightnessandsaturationofcolorprintorpaintonobjectswithoutmakingcontactwiththeobject.Itismainlyusedonbagmakingmachines,automaticwrappingmachines,printingpresses,etc.forvarioustypesofcontrolsuchasdetectionofregistermarksinred,blue,yellow,etc.topositionforwrappingandcutting.Thereisabroadrangeofmarksensorswithdifferentapplicationsthatalsoincludedifferentiationbetweencolorswhereincorrectcolorsmaycausequalitycontrolproblemsandthedetectionofdifferentlevelsofreflectancebetweenpaintcolorsonthefrontandbacksidesofobjects(parts)inaproductionlinecheckingfortheincorrectsidefacingup.MarksensorshavecolorvariationoflightsourceLEDandU-shapedsensor.


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Applicationexamples


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OilandChemicalresistantsensors/SensorsforharshenvironmentPFseriessensorshaveaprotectivefluoro-plastic(PFA)coveringforenhancedresistancetooilsandchemicals.Thesearecapableforimmersedapplications.

ApplicationExample


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Someofthemodelshaveglasslenswhichcanwithstandharshenvironmentcomparedtooneswithaplasticlens.Thesesensorshaveahighpoweredlightbeamtosecurereliablelongrangedetectioneveninharshenvironments.


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3.UltrasonicSensorsUltrasonicsensorsdetectobjectsmadeofvariousmaterialsregardlessofshape,size,color,orsurfacecontours.Theyoperateusinghigh-frequency(100~500kHz)soundwavesthatareinaudibletohumanear.Thesesensorsworkwellinenvironmentscontainingdirt,mist,orvaporsthatcausedifficultyforphotoelectricsensors.Typicalsensingdistance--60mm~6m

ApplicationExamples


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4.LightCurtainsLightcurtainsreliablyandcost-effectivelyprotectagainstaccessintohazardouspointsandareas.Lightcurtainsarealsousedinapplicationtodetectfallingobjectfromaconveyor.TakexLightcurtainsaregoodforvariousapplicationsbutarenotsafetyrated.

Applicationexamples


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5.HotandColdMetalSensors TheHMD(HotMetalDetector)isusedforthedetectionofhotobjects.Todothis,thesensorusestheinfraredradiationthatisemittedbyhotmaterialswhichisreceivedbyanopticalsysteminthesensor.Ifthisradiationexceedsathresholdsetinthedevice(responsetemperature),thedeviceswitches.Thishappensextremelyfastandallowsthesafemonitoringofrapidprocesses.Responsetimesofupto5mscanbeachieved.Theprincipleoftheinfraredsensorallowsthedetectionofhotobjectsevenatagreatdistance.Infraredsensorsareusedwhereverinductivesensorscannotbemountedduetothehightemperature.TheCMD(ColdMetalDetector)iscomposedofthetransmitterandreceiverandhashighdetectionaccuracy.Itisusedeveniftheobjecttemperatureishighandunderstrongexternallight.Thepunchhalldetectionsensor(weldpointdetector)detectsthepunchhallinstalledintheweldingpartofthecoil(steelboard)thatrunscontinuouslybetweenthetransmitterandthereceiver.Typicalsensingdistance--250mm~1m


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ApplicationExamplesforHMD

ApplicationExampleforCMD


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6.TerminologyExcessGain:ExcessGainisameasureofsensingpoweravailableinexcessofthatrequiredtodetectanobject.Anexcessgainof1meansthereisjustenoughpowertodetectanobject,underbestconditionswithoutobstaclesplacedinthelightbeam.Thedistanceatwhichexcessgainequals1isthemaximumrange.Anexcessgainof100meansthereis100timesthepowerrequiredtodetectanobject.Generallymoreexcessgainavailableattherequiredrange,themoreconsistentlythecontrolwilloperate.Foreachdistancewithinrange,thereisspecificexcessgain.Throughbeamcontrolsgenerallyprovidethemostexcessgain,followedbyreflexanddiffuse.

TypicalExcessGainforThruBeamSensor


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TypicalExcessGainLongRangeDiffuse

TypicalExcessGainRetro-reflective


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TypicalExcessGainforBackgroundSuppression


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TypicalExcessGainforConvergentDiffuseSensor

BeamPatternA beam pattern is plotted on a 2-dimensional graph to illustrate how the photoelectric receiver is designed to respond to its emitter. Maximum light energy occurs along the sensor’s optical axis. The light energy decreases towards the beam pattern boundaries. The horizontal axis usually shows the range of the sensor.

Typical Beam Pattern for Thru-Beam sensor


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TypicalBeamPatternforDiffuseReflectivesensor

TypicalBeamPatternforRetroReflectivesensor

Contrastratio:Contrastmeasurestheabilityofphotoelectriccontroltodetectanobject,itisaratioofasignalstrengthwhendetectinganobject(light)toasignalstrengthwhenthere’snoobject(dark).Allotherbeingequal,thesensorthatprovidesthegreatestcontrastratioshouldbeselected.Forreliableoperationaratioof10:1isrecommended.


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7.ApplicationTable Selectionaccordingtoindustry

Sensor

Delivery/Logistics

Food

/packaging

/drug

Automated

machine

s

Robo

t

Semicon

ductor

Electron

icassem

bly

Stee

l/heavyIn

dustry

Textile

Chem

ical/oils

Pape

r/rubb

er/plastic

Glass/ceramic

Banking/service

Automob

ile

Fiberoptics

● ● ● ● ●

● ●

●

Embeddedamplifiersensor

● ● ● ● ● ●

● ● ● ● ● ●Lightcurtains ● ●

● ● ● ●

● ●

●

Backgroundsuppression ● ● ● ● ● ● ● ● ● ● ● ●UltrasonicSensors ● ● ● ● ● ● ● ● ●AC/DCPowersupplysensor

● ● ● ● ●MarkSensors ● ● ● ● ● ColorSensors ● ● ● ● ● ● ●ImageSensors ● ●

●

●

●

Photosensorforsteelandheavyindustries

●

●

Productspecific

● ●

● ●


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SelectionaccordingtopurposeofdetectionSensor

Turbidity

Distan

ce

Dimen

sion

Num

bero

frotations

Infrared

/tem

perature

Liqu

idlevel

Wafer

Glasss

ubstrate

Illum

inationche

ck

Ignitio

ncheck

Safety

Fiberoptics● ● ● ● ● ● ●

Embeddedamplifiersensor ● ● ● ● ● ● Lightcurtains

●

●Backgroundsuppression ● ● ● ● ● UltrasonicSensors

● ● ● AC/DCPowersupplysensor MarkSensors

● ● ● ColorSensors

ImageSensors

● ●


●

Productspecific

● ●

● ● ● ● ●


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Selectionaccordingenvironment

Sensor

Restric

tedspace

High

/lowte

mpe

rature

Dusty

Subjecttowatersp

lash

Vacuum

Chem

ical

Explosiveen

vironm

ent

Fiberoptics● ● ● ● ●

Embeddedamplifiersensor ● ● ● ● Lightcurtains

Backgroundsuppression ● ● ● UltrasonicSensors

● ● AC/DCPowersupplysensor MarkSensors

ColorSensors

ImageSensors


● ● ● Productspecific

● ● ●


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References:SensorHandbookbyDr.SabrineSolomanPhotoelectricSensors&Controls,selection&applicationMr.ScottJudsTakex2013Catalog

takex america inc training manualtakex america inc training manual 5 | page 2. photoelectric sensors...

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