Magnetic Stirrer Beta Release V01
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Transcript of Magnetic Stirrer Beta Release V01
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
1
Product Overview
Uses:Magneticstirrers(alsoknownasmagneticstirplates)areverycommoninexperimentalchemistryandbiology.
Theyareusedtomixcomponents(solidsandliquids)togethomogeneousliquidmixtures.Commonexamplesinclude
bacterialgrowthmediaandbuffersolutions.
HowTheyWork:Magneticstirrersmixsolutionsusinganexternalmagneticfieldthatrotatesasmallmagneticbarthat
hasbeenplacedinthemixtureofinterest.
Advantages:Magneticstirrersminimizetherisksofcontaminationsinceonlyaninertmagnetbar,whichcaneasilybe
cleaned,isputinsidethesample/fluid.Inaddition,usingamagneticstirrerratherthanmanualstirringiscriticalfor
consistent,reproduciblemixingormixingoverlongtimescales.Proteindialysis,forexample,requiresmulti-houror
overnightsamplemixingandissensitivetobacterialcontamination.
ThisMagneticStirrer:Canrotateaninternalmagnetatvariablespeeds,mixingvolumesuptooneliter.Glasswarewith
astirbarisplaceddirectlyontopofthestirrerunit.Thedeviceisbattery-operatedandlargelyisolatedfromspillsbyits
plasticcaseandgasket.
Figure1.TeklaLabsmagneticstirrerwith500mLsample
Figure2.Internalviewofdesign
Acknowledgements and Creative Commons LicensingDesignedbyM.J.Watts(formerlyofMasseyUniversity).
Designopen-sourcecourtesyofMasseyUniversityNewZealand.
ThisblueprintismadeavailableunderaCreativeCommonsAttribution-NonCommercial-ShareAlike3.0Unported
licence.http://creativecommons.org/licenses/by-nc-sa/3.0/
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
2
Navigating the Blueprint Document
ProductOverview .................................................................................................................................................................. 1
AcknowledgementsandCreativeCommonsLicensing ......................................................................................................... 1
WhatSkillsandToolsDoINeed? .......................................................................................................................................... 2
Specifications:Whatcanthismagneticstirrerdo? ............................................................................................................... 3
WhatMaterialsAreNeeded? ................................................................................................................................................ 3
DetailsofMaterials................................................................................................................................................................ 5
Module1:MotorAssembly ................................................................................................................................................... Module2:MotorController(SpeedAdjustment) ............................................................................................................... 10
FinalAssembly..................................................................................................................................................................... 12
HowdoIknowitisworkingcorrectly?................................................................................................................................ 13
NowhowdoIusethis,troubleshootandperformmaintenance? ..................................................................................... 14
Feedback.............................................................................................................................................................................. 14
What Skills and Tools Do I Need?
Safetyconsiderationsduringconstruction
Thesolderingironbecomesextremelyhot.Hotsolderandfluxcangiveoffharmfulfumes.Conductsolderingin
awellventilatedenvironmentandtakestandardprecautionstosecurethehotiron.
Themotorcanbecomehotimmediatelyafteroperation.
Thesesafetyconsiderationsare,ofcourse,inadditiontonormalprecautionsnecessarywhenusingthevarious
toolsneededforthisproject.
Requiredskills
Skill Module(s)
Solderingtoprintedcircuitboard 2Press-fittingshaft 1
Drillingholesinsheetmetal 1
Requiredtools
Tool Module(s)
Screwdriver 1,2,3
Drill(handdrillordrillpress) 1
Solderingiron 2
Methodofcuttingandbendingsheetmetal 1
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
3
Specifications: What can this magnetic stirrer do?
Listofspecifications
1. Magneticstirbarrotatesatanadjustablespeed.Maximumrotationratedependsonthecomponentsused,
includingmotor,magnets,andstirbar.Rotationwillbeoptimalinlowfrictioncontainerssuchasglass
containers.
2. Createsstablevortexinbeakersupto1000mL.Optimizedforusewith250mLbeakers.
3. Stirreroperatesonbatterypower,notplug-inwallpower.
4. Interiorofdeviceisasisolatedfromoutsideenvironmentaspossiblesothatdeviceisresistanttospills.
What Materials Are Needed?
Figure3.Overviewofmaterialsused
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
4
ListofMaterials.Notethatinmanycases,alternatematerialscanbeused,aslongaschangesinpropertiessuchas
dimensionsareaccountedforinthebuildingprocess.Pleaseaddyoucommentstotheonlinedocumentifyoufind
alternativematerialsorsolutions.
Part PartDescription Module PartID Quantity Cost(USD)
Rotorbody Usedtoholdmagnets,cutfromlightwood
orhardboard(fiberboard)5mmthick.
1 M001 40mmdiameter $0.25
Rotormagnets Magnetsthatspinonrotorbody.Circular
orbarmagnetsmaybeused.Seetext,
1 M002 2 $2.60
DCmotor BrushorbrushlessDCmotor,body30-35
mmlong,withmountingscrews
1 M003 1 $2.99
Sheetmetal 16gaugeorsimilar,formotormount.Also
formetalstripconnectingmagnets
1 M004 30x70mm $0.25
Printedcircuit
board(PCB)
Connectselectronics;canalsowirebyhand 2 M005 1 Spare,or
handwire
Plasticcasing Enclosesunit,seeMaterialHints 2 M006 1 $14.90
Batteryclip Holdsandconnectsthebattery 3 M007 1 $0.89
Knob Tosetvariousspeedsettings 2 M008 1 $5.30
Potentiometer Speedregulation,canbeboughtwithknob 2 M009 1
M2.5screws M2.5x10mmmachinescrew 1 M010 2 $0.20
M2.5screws M2.5x20mmmachinescrew 3 M011 4 $0.40
M2.5nut M2.5hexnut 1 M012 2 $0.20
Stirbar Magneticstirbar Final M013 1 $2.00
LEDlight Optional.Lightsupwhenmotorisgetting
power
3 M014 1 $0.40
Battery Dsize Final M015 1 $2.00
Transistors,
capacitors
TeklaLabsisworkingonadetailedlistof
theseparts
2 M017+ $4.00
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
5
Details of Materials
Thisisamoredetailedexplanationofthekeymaterialsusedinthedesign.Ingeneral,equivalentoptionscanbebought
frommanyothersuppliersanddimensionsandotherparameterscanbereadjustedasneeded.
M001Rotorbody
Cutfrombulkmaterial,canusescissorsorhobbyknife.
M002Rotormagnets
Smallrare-earthmagnetsarenecessarytocoupletherotorandstirbarinthiscompactdesign.Theauthorsuggests
removingthemagnetsfrommagneticbatteryconnectors.Magnetscanbecircularorbarmagnets.Theseareavailable
fromScienceLabSupplies,sciencelabsupplies.com,#1921-29($1.30each).Individualmagnetsarealsoavailabledirectly
fromothersuppliers,e.g.http://applied-magnets.amazonwebstore.com/M003DCmotor
AuthorsinitialdesignusedagenerictoymotoravailablefromJayCar(jaycar.com.au),YM2706orYM2707($3.25or
$4.25),1.54.5VDCoperatingvoltage
PrototypecontainsHTIModel32DCmotormarkedHTBRR032021903F-0002
RadioShack273-2331.5to3VDCHobbyMotor($2.99)maybeasuitablereplacement
Motorcaseshouldhavethreadedmountingholesontheshaftside.Thiswillallowittobeattachedtothesheetmetal
mount.
M005Circuitboard
Ifaprintedcircuitboardcannotbeobtained,hand-wiringelectroniccomponentsisstraigthforward.TeklaLabswill
providewiringinstructionsinthefuture.
M006Plasticbox
BudIndustriesPN-1324-DG(DigiKey377-1124-ND)$14.90
TeklaLabsunitisa12cmwidex17cmlongby5.5cmtallcasemadeofABSplastic.Thesedimensionsarenotcritical
butthesurfaceareahastobelargeenoughtoholdthesizeglassbeakeryouwanttouse.
M007Batteryholder
MemoryProtectionDevicesBHDL(DigikeyBHDL-ND)$0.89
M009Potentiometer
TeklaLabswillconfirmresistancerangeanddimensionsofpotentiometer.
M010M2.5ScrewsDCmotorscrewsneedtobeflatheads,otherwiseyouwillhaveexcessiverubbingbetweenthemountingscrewsandtherotating
hardboard.
M013StirbarScienceKitandBorealLaboratories(sciencekit.com)WW46316M14SpinBarMagneticStirBar$2.00
M014LEDlight
PanasonicLN21RPH(DigiKeyP374-ND)$0.40
M016Knob
Optional.StandardknobsareavailablefromDigiKeyforafewdollars.Acylindricalrubberstopperorcorkisacheap
substitute,andcanbepresseddirectlyontothepotentiometer.
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
6
Module 1: Motor Assembly
Approximatetime=1hour
Step-by-stepinstructions
Figure4.Close-upofmotorsetup.
1. Cutsheetmetalintotwopieces:asmallmetalstripforuseontopoftherotorbodyandalargerpiecefor
mountingthemotor.
2. Cutholesinthesmallmetalstripforthe
motorshaftandforthescrewstoholdthe
motor.
Thesmallmetalstripisimportantasit
createsalow-profilehorseshoemagnet,
whichgreatlyenhancesthepullofthe
magnetsascomparedtothecasewhere
nometalstripisused.Ifthemagnetsareputdirectlyontothehardboardwithouta
metalstrip,onehastobecarefulnotto
changethepowersettingtooquicklyon
thefinishedunitorelsethemagneticstir
barwilljumpofftarget.
.
Figure5.Topandsideviewofsmallmetalstrip,magnetsandhardboard
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
7
3. Drillholesformotorscrewsandshaftinthemotor
mountsheet
CAUTION:clampsheetmetaltoworksurfacewhile
drilling.Keephandsfreeofsheetmetalincaseitcomes
freeandrotateswiththedrill.
Positionsofholesformotorscrewsandshaftare
critical.Thesedependontheexactmodelofmotor
thatisused.Formostpreciseplacement,firstmark
holepositioninpencil.Thenindentthesheetmetal
surfacewithanawlornail.Finally,positiontipofdrill
bitintheindentation.
Figure6.Topviewschematicofflatmetalmountsheet,indicatinglocationsofdrillholesandmetalbending.
4. Bendthemotormountsheettoformthemetalmotormountshapedescribedbelow.Themountheight(30
mminthiscase)shouldbehighenoughtofitthemotorwithoutcompressingitssolderleads.Theangleyou
bendthesheetisnotcritical.
Figure7.Sideviewschematicofbend-linesofmetalmountsheet.
5. Attachmotortothemotormountsheetwithscrews.Screwswithshortheadsshouldbeusedsothatthereis
enoughclearancetotherotorbody.
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
8
Figure8.Finalsideviewschematicofmotorandsheetmount.
6. Cutthehardboardtoformtherotorbody
Therotorbodysdiameterisdependentonthesizeofthestirbaryouwillbeusing.Themagnetsontherotorbodyshouldbespacedapproximately80%ofthestirbarlength.Usinglongerbarmagnetsontherotorbody
allowsforawiderrangeofmagneticstirbarsizes.Ourrotoris38mmindiameterand5mmthicktofita
magnetcenter-to-centerdistanceof24mm.
7. Drilltwoscrews(orholes,ifyoureusingmachinescrews)throughthebottombaseofthehardboard.
8. Installthemagneticstriprotoratopthedrilledhardboardusingthecorrespondingnuts
9. Press-fittherotorbodyontothemotorshaft.
Thisisafrictionfit.Themotorshaftcanbecoveredbyapieceofheatshrinkplastictoprovideafirmfittothe
holeinthecenterofthehardboardrotorbody.
10.Solderthetwomotorwirestocontactsontheprintedcircuitboard(onetogroundandonesothatitcanbe
electricallyconnectedtothepotentiometer).
11.Attachthemotormountsheet(withattachedmotor)totheprintedcircuitboardwithscrews.
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
9
12.Gluemagnetsontothemetalstriponthehardboardrotor.Magnetdistanceshouldbeabout80%ofthelength
ofthestirbar.
Figure9.ExplodedviewofModule1components.1)metalsheetformountingmotor2)motor3)hardboard4)smallmetalstrip5)
magnets6)screws,6total
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
10
Module 2: Motor Controller (Speed Adjustment)
Approximatetime=1hour
Step-by-stepinstructions
1. ConstructaPCBaccordingtothecircuitshownbelow.Alternately,ahand-wiredcircuitmaybesimplerto
constructwithavailableparts.(TeklaLabsisworkingonconvertingthiscircuitdiagramintoamoreaccessible
formandphotographingthehand-wiringstep-by-step.)
2. Drillaholethroughtheplasticcasingtoconnectthespeedcontrolknobtothepotentiometer.
3. Attachknobtopotentiometershaftoutsideofcase
Figure10.Schematiccircuitdiatramof
components.
.
Figure11.Wiringdiagramforhardwiringin
theabsenceofaccesstoaprintedcircuit
board
Figure11
npn transistors
pnp transistor
ground
battery
potentiometer
motor
LED light
capacitor
resistor
transistors
KEY
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
11
Module3:BatteryPowerandPowerIndicatorLight
Approximatetime=1hourStep-by-stepinstructions
Batterypower
1. Solderthetwobatterycasingwirestocontactsontheprintedcircuitboard.Onewiremustbeconnectedtogroundandonemustbeconnectedtoacontactsothatthewirecanbeelectricallyconnectedtothe
potentiometer.
2. GluethebatterycasingtothePCB.Hotmelt,ahotglueguncanbeusedforthisstep.
LEDlight(optional)
3. DrillaholeonthesideoftheplasticcasingtofittheLEDlighttoprovideatightfit.
4. SolderthetwoLEDlightwirestocontactsontheprintedcircuitboard(onetogroundandonesothatitcanbe
electricallyconnectedbetweenthepotentiometerandthemotor.
5. CarefullypresstheLEDlightintotheholeusingpliers.
Figure11.Close-upoffinishedbatteryclip. Figure12.Close-upoffinishedLEDlightconnection
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
12
Final Assembly
Approximatetime=30minutes
Step-by-stepinstructions
1. Screwcircuitboardintobottomofplasticcase
2. PlaceD-batteryintobatteryclips
3. Screwtopontoplasticcasebody
a. Donotover-tightenasthiscouldcausetheunevenpressureloadalongtheperimeterandthusbowing
(outwardbending)ofthetopthataffectsthedistancebetweentheglassbeakerandthemagneticrotor.
Figure13.Finished,closedmagneticstirrerwithmagneticstirbarontop.
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
13
How do I know it is working correctly?
Inspection
1. Theunitshouldbecompletelysealed,butwithoutover-tighteningofthescrewsusedtoattachthetopsurface.
Thereshouldbenoentrypointsintotheunitotherthantheholescutfortheindicatorlight(ifused)andforthe
speedcontrolknob.
2. Whenturningtheuniton,withaworkingbatteryinplace,theLEDindicatorlightshouldturnon.
Testing
1. Insertstirbarintooneliterbeakerwithoneliterwater.
2. Stirrodshouldnotrotatewhenknobisturnedtozero.
3. Graduallyturnknobtohighersetting.Stirbarshouldrotatefasterasmotorisoperatedatahigherspeed.
4. Atmaximumspeedsetting,themagneticstirrershouldbeabletoformalargevortexwithinaonelitervolume
beaker(seepicture).
Figure14.Testingthefinishedmagneticstirrer:atfullspeed,alargevortexshouldformin1Lofwater
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Product Magnetic Stirrer
DocID D0001 Version 0.1
Author Malcolm Watts Status Pre-release
Editor Tekla Labs Date 7/11/2011
14
Now how do I use this, troubleshoot and perform maintenance?
Operatorsafety
1. Whenworkingwithhazardouschemicals,glasswareshouldbecovered.Stirrershouldbekeptinasecondary
containertocatchanyspills
2. Retrievestirbarwitharetriever,notbyhand.Thiscanbemadebytapingamagnettotheendofaplasticrod
orpen.
Maintenance
1. Changebatterywhennecessary(indicatedbyLEDlight).
2. Whenchangingbattery,alsoconfirmthatmagnetrotorstillmakestightfitwithshaft.
Troubleshooting1. Problem
Stirbardoesnotmoveatallwhenknobisturnedup.
Solution
Removecoverandcheckthatmotorandrotorbodyarespinning.Ifnot,checkbatteryandmotorconnections.
Iftheyare,checkthatmagnetsusedarecapableofmovingstirbarandarecloseenoughtotopofplasticcasing.
Ifcurrentisdeliveredtothemotorbutitdoesnotspin,themotormayneedtobereplaced.Ifrotorspinsbut
doesnotcatchstirbar,trymovingrotorfurtherupalongmotorshaft.
2. ProblemStirbarmoveswhenknobisturnedup,butdoesnotrotatefully.
Solution
Double-checkthatthebeakerandstirbararebothcenteredoverthemotorshaft.Graduallyturnuprotation
speeduntilrotorcatchesstirbar.
Feedback
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ifyou:
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- hadanyotherproblemsorsolutionstoshare
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