Product Manual1134 - Switchable Voltage Divider

Phidgets 1134 - Product Manual

For Board Revision 0

© Phidgets Inc. 2010

Contents

4 Product Features

4 Applications

4 Connections

4 Type of Measurement

5 Getting Started

5 Checking the Contents

5 Connecting all the pieces

5 Testing Using Windows 2000/XP/Vista

7 Testing Using Mac OS X

7 Programming a Phidget

7 Code Samples

7 Coding for your Sensor

8 Technical Information

8 Formulas

8 ConfiguringtheVoltageDivider

9 Variable resistance sensors

9 OtherInterfacingAlternatives

9 Analog Input Cable Connectors

10 MechanicalDrawing

10 DeviceSpecifications

10 Product History

10 Support

41134_0_Product_Manual - March 29, 2010

Designedtoconnecttoa:

1018 - PhidgetInterfaceKit 8/8/8•

1019 - PhidgetInterfaceKit 8/8/8 w/6 Port Hub•

1070 - PhidgetSBC•

1202-PhidgetTextLCD•

Product FeaturesApplications

Providesaninterfacetonon-Phidgetsvariableresistancesensorssuchas:ForceSensingResistors(FSR),light•sensors,thermistors(heatsensors),andbendsensors.

Precisionresistorsonthe1134allowstheapplicationtopreciselycalculatetheresistanceoftheattachedsensor.•

Possibletousemultipleresistorstoselectanequivalentresistanceforthe‘fixed’resistor•

Theinterfacetothevariableresistancesensorisaconvenientterminalblock.•

Connections

Type of MeasurementThesensorusesratiometricmeasurement.

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ConnecttheSwitchableVoltageDividertoanAnalogInput1.on the PhidgetInterfaceKit 8/8/8 board using the sensor cable.

Connectthevariableresistancesensortotheterminal2.blockontheVoltageDivider.

Select an appropriate measurement range for your 3.applicationbytogglingthedesiredDIPswitch.Wearetogglingthe27.4Kswitch.Whentheswitchisdown,theassociatedmeasuringresistorisselected.Itispossibletohavemorethanoneswitchtoggledandhavetheresistorsinparallel.Forourpurposeonlytoggleoneswitch.

Connect the InterfaceKit board to your PC using the USB 4.cable.

Getting StartedChecking the Contents

In order to test your new Phidget you will also need:

A PhidgetInterfaceKit 8/8/8•

A USB Cable•

Avariableresistancesensororanyresistor(weareusinga27K•resistor)

You should have received:

ASwitchableVoltageDividerboard•

A Sensor Cable•

Connecting all the pieces

Testing Using Windows 2000/XP/VistaDownloading the Phidgets driversMakesurethatyouhavethecurrentversionofthePhidgetlibraryinstalledonyourPC.Ifyoudon’t,dothefollowing:

Gotowww.phidgets.com>>Drivers

DownloadandrunPhidget21Installer(32-bit,or64-bit,dependingonyourPC)

You should see the iconontherighthandcorneroftheTaskBar.

Running Phidgets Sample Program

Doubleclickingonthe icon loads the Phidget Control Panel; we will use this program to make sure that your newPhidgetworksproperly.Sincethesensorisconnectedtoa1018,thecomputerwillseeonlythe1018.ThesensorisprovidingdatathroughtheAnaloginputitisconnectedto.

The source code for the InterfaceKit-full sample program can be found under C# by clicking on www.phidgets.com >>Programming.

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DoubleClickonthe icontoactivatethePhidget Control Panel and make sure that the Phidget InterfaceKit 8/8/8 is properly attachedtoyourPC.

DoubleClickonPhidgetInterfaceKit1.8/8/8 in the Phidget Control Panel to bring up InterfaceKit-full and check that the box labelled Attached containsthewordTrue.

MakesurethattheRatiometricbox2.isTicked.

The Analog In box displays a number 3.correspondingtotheresistorvalue.

Youcanadjusttheinputsensitivity4.bymovingthesliderpointer.

Click on the Sensors button to bring 5.uptheAdvancedSensorForm.

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IntheAdvancedSensorForm,selectthe1.1134-SwitchableVoltageDividerfromthedropdownmenu.

Select the appropriate resistor from the 2.drop-down menu that has been selected withtheDIPswitchontheboard.

The resistance measured by the sensor is 3.shownhere.

Formulausedtoconverttheanaloginput4.SensorValueintoresistance.

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71134_0_Product_Manual - March 29, 2010

Testing Using Mac OS XClickonSystemPreferences>>Phidgets(underOther)toactivatethePreferencePane•

MakesurethatthePhidgetInterfaceKit8/8/8isproperlyattached.•

DoubleClickonPhidgetInterfaceKit8/8/8inthePhidgetPreferencePanetobringuptheInterfaceKit-Full•example.ThisexamplewillfunctioninasimilarwayastheWindowsversion,butnotethatitdoesnotincludeanAdvancedSensorDisplay.

Programming a Phidget

Phidgets’philosophyisthatyoudonothavetobeanelectricalengineerinordertodoprojectsthatusedeviceslikesensors,motors,motorcontrollers,andinterfaceboards.Allyouneedtoknowishowtoprogram.WehavedevelopedacompletesetofApplicationProgrammingInterfaces(API)thataresupportedforWindows,MacOSX,andLinux.Whenitcomestolanguages,wesupportVB6,VB.NET,C#.NET,C,C++,Flash9,Flex,Java,LabVIEW,Python,Max/MSP,andCocoa.

Code SamplesWehavewrittensampleprogramstoillustratehowtheAPIsareused.

Duetothelargenumberoflanguagesanddeviceswesupport,wecannotprovideexamplesineverylanguageforeveryPhidget.Someoftheexamplesareveryminimal,andotherexampleswillhaveafull-featuredGUIallowingallthefunctionalityofthedevicetobeexplored.Mostdevelopersstartbymodifyingexistingexamplesuntiltheyhaveanunderstandingofthearchitecture.

Go to www.phidgets.com>>Programming toseeiftherearecodesampleswrittenforyourdevice.Findthelanguageyouwanttouseandclickonthemagnifyingglassbesides“CodeSample”.Youwillgetalistofallthedevicesforwhichwewrotecodesamplesinthatlanguage.

IfthisisyourfirsttimewritingaprogramtocontrolaPhidget,youshouldreadtheGettingStartedGuideforthelanguageyouareplanningtouse.

Coding for your SensorPhidgetanalogsensorsdonothavetheirownAPI,butinsteadtheiroutputisavoltagethatisconvertedtoadigitalvalueandaccessedthroughtheSensorValuepropertiesandeventsonaPhidgetInterfaceKit.ItisnotpossibletoprogrammaticallyidentifywhichsensorisattachedtotheAnalogInput.YourapplicationwillneedtoapplyanyformulasfromthismanualtotheSensorValuetotranslateitintousabledata.

SeethePhidgetInterfaceKitproductmanualforanoverviewofitsAPIandadescriptionofourarchitecture.

81134_0_Product_Manual - March 29, 2010

Technical InformationThe1134SwitchableVoltageDividerisavoltagedividerwithswitches.Theswitchescanbeusedtocontrolwhichresistorsareusedinthevoltagedivider.Fromlefttoright,theresistancevalues(inOhms)are249,820,2.61K,8.45K,27.4K,91K,300Kand1M.Itispossibletohavemultipleswitchesflipped,puttingthecorrespondingresistorsinparallel.

FormulasTheFormulatotranslateSensorValueintoresistanceis:

Resistance(Ohms)=Req*(1000/SensorValue-1)

WhereReqistheequivalentresistanceoftheswitchesthatareflippedoninOhms.

TheSwitchableVoltageDividerhasaninternalbufferontheoutput.Thisallowstheoutputtobereadwithoutdistortioncausedbythedevicereadingthemeasurement,suchasthePhidgetInterfaceKit.

Configuring the Voltage DividerTooptimizethevoltagedividertomeetyourneeds,youhavetoadjusttheswitchable resistance to match the characteristicsofyourchosenvariableresistor.First,adjusttheresistancefornostimulionyoursensor,thenapplymaximum stimuli and make sure that the Sensor Value stays within a range that givesyouanacceptableresolution.Theformula is most accurate at a SensorValue of500,withanerrorof0.4%.At100and900,theerrorincreasestoapproximately1.1%andat50and950,itincreasesto2.1%.

Asageneralrule,iftheSensorValueisover900,alowerresistanceshouldbeswitchedin.IftheSensorValueisbelow100,ahigherswitchshouldbetoggled.Continue adjusting the switches until you findanacceptablerange.

Warning:Itispossibleforthe1134toapplyupto5Vtothevariableresistor.Iftheresistorcannothandlethisvoltage,itcanbedamaged.

The1134isaverysimplewayofmeasureresistance.Wheninterfacingtosensorswithsmallresistances(like100ohmRTDs,forinstance),largecurrentscanflow-upto30mA.Thislevelofcurrentmaycausesubstantialheatinginthevariableresistor,distortingthemeasurementorevenpossiblypermanentlydamagingit.

OUTPUT+5V

249

820

2.41

K

8.45

K

27.4K

91K

300K

1M

91134_0_Product_Manual - March 29, 2010

Variable resistance sensorsHerearesomeinterestingvariableresistancesensorsthatcouldbeusedwiththeVoltageDivider.

Sensor Type Manufacturer Example Digikey searchLight Sensors AdvancedPhotonics PDV-P9003-1 photocell

Force Sensors CUIInc. IESP-12 force sensor

Thermistors US Sensor 615-1037-ND thermistor radial

Bend Sensors imagesco.com FLX-01 n/a

Other Interfacing AlternativesIfyouwantmaximumaccuracy,youcanusetheRawSensorValueproperty.Tomodifytheformula,substitute(SensorValue)with(RawSensorValue/4.095)

IfthesensorisbeinginterfacedtoyourownAnalogtoDigitalConverter(notaPhidgetdevice),ourformulascanbemodifiedbyreplacing(SensorValue)with(Vin*200).ItisimportanttoconsiderthevoltagereferenceandinputvoltagerangeofyourADCforfullaccuracyandrange.

Analog Input Cable Connectors

EachAnalogInputusesa3-pin,0.100inchpitchlockingconnector.Picturedhereisaplugwiththeconnectionslabeled.Theconnectorsarecommonlyavailable-refertotheTablebelowformanufacturerpartnumbers.

Cable ConnectorsManufacturer Part Number Description

Molex 50-57-9403 3 Position Cable Connector

Molex 16-02-0102 Wire Crimp Insert for Cable Connector

Molex 70543-0002 3 Position Vertical PCB Connector

Molex 70553-0002 3PositionRight-AnglePCBConnector(Gold)

Molex 70553-0037 3PositionRight-AnglePCBConnector(Tin)

Molex 15-91-2035 3PositionRight-AnglePCBConnector-SurfaceMount

Note:Mostoftheabovecomponentscanbeboughtatwww.digikey.com

101134_0_Product_Manual - March 29, 2010

Mechanical Drawing

Device SpecificationsCharacteristic ValueMaximum Current Consumption 30 mA

Supply Voltage 3.0to5.25VDC

MaxSwitchableResistance 1M Ohms

MinSwitchableResistance 172 Ohms

VariableResistorRange Up to 50 MegaOhms

ResolutionbetweenSensorValue100-900 Less than ±1%ofvariableresistorperSensorValue

1:1scale

Product History

SupportCallthesupportdeskat1.403.282.73358:00AMto5:00PMMountainTime(US&Canada)-GMT-07:00

or

E-mailusat:support@phidgets.com

Date Board Revision CommentMarch 2010 0 ProductRelease