Table Of Content

Analog Interfacing to Embedded Microprocessor Systems Analog Interfacing to Embedded Microprocessor Systems Stuart R. Ball AMSTERDAM (cid:127) BOSTON (cid:127) HEIDELBERG (cid:127) LONDON NEW YORK (cid:127) OXFORD (cid:127) PARIS (cid:127) SAN DIEGO SAN FRANCISCO (cid:127) SINGAPORE (cid:127) SYDNEY (cid:127) TOKYO Newnes is an imprint of Elsevier NewnesisanimprintofElsevier. Copyright#2004,byElsevier.Allrightsreserved. Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,or transmittedinanyformorbyanymeans,electronic,mechanical,photocopying, recording,orotherwise,withoutthepriorwrittenpermissionofthepublisher. Recognizingtheimportanceofpreservingwhathasbeenwritten,Elsevier printsitsbooksonacid-freepaperwheneverpossible. LibraryofCongressCataloging-in-PublicationData Ball,StuartR.,1956– Analoginterfacingtoembeddedmicroprocessorsystems/StuartR.Ball.—2nded. p. cm.—(Embeddedtechnologyseries) Rev.ed.of:Analoginter-facingtoembeddedmicroprocessors.2001. Includesindex. ISBN0-7506-7723-6 1. Embeddedcomputersystems—Designandconstruction. I.Ball,StuartR.,1956- Analoginter-facingtoembeddedmicroprocessors.II.Title.III.Series. TK7895.E42B332003 004.16—dc21 2003044211 BritishLibraryCataloguing-in-PublicationData AcataloguerecordforthisbookisavailablefromtheBritishLibrary. Thepublisheroffersspecialdiscountsonbulkordersofthisbook. Forinformation,pleasecontact: ManagerofSpecialSales Elsevier 200WheelerRoad,SixthFloor Burlington,MA01803 Tel:781-313-4700 Fax:781-313-4882 ForinformationonallNewnespublicationsavailable,contactourWorldWideWeb homepageat:http://www.newnespress.com 10 9 8 7 6 5 4 3 2 1 PrintedintheUnitedStatesofAmerica Contents 1 System Design 1 Dynamic Range 1 Calibration 2 Bandwidth 5 ProcessorThroughput 6 Avoiding Excess Speed 7 Other System Considerations 8 Sample Rate and Aliasing 11 2 Analog-to-Digital Converters 13 ADCs 15 Types of ADCs 17 ADC Comparison 25 Sample and Hold 26 Real Parts 29 MicroprocessorInterfacing 30 Clocked Interfaces 35 Serial Interfaces 36 MultichannelADCs 41 Internal Microcontroller ADCs 42 Codecs 43 Interrupt Rates 44 Dual-Function Pins on Microcontrollers 44 Design Checklist 46 v 3 Sensors 47 TemperatureSensors 47 Optical Sensors 59 CCDs 71 MagneticSensors 82 Motion/Acceleration Sensors 86 Strain Gauges 89 4 Time-Based Measurements 91 MeasuringPeriodversus Frequency 94 Mixing 96 Voltage-to-Frequency Converters 98 Clock Resolution and Range 100 Extending Accuracy with Limited Resolution 102 5 OutputControl Methods 107 Open-Loop Control 107 Negative Feedback and Control 107 Microprocessor-Based Systems 108 On-Off Control 109 Overshoot 112 Proportional Control 112 Proportional, Integral, Derivative Control 116 Motor Control 127 Predictive Control 133 Measuringand Analyzing Control Loops 134 PID Software Examples 138 Things toRemember in Control Design 143 6 Solenoids, Relays, and OtherAnalog Outputs 145 Solenoids 145 Heaters 149 Coolers 155 LEDs 157 DACs 162 Digital Potentiometers 163 Analog Switches 166 vi Contents 7 Motors 171 Stepper Motors 171 DC Motors 190 Tradeoffs between Motors 206 Power-Up Issues 207 Motor Torque 208 A Real-World StepperApplication 209 8 Electromagnetic Interference 215 Ground Loops 215 Electrostatic Discharge 220 9 High-Precision Applications 225 Input Offset Voltage 227 Input Resistance 228 FrequencyCharacteristics 229 Temperature Effects in Resistors 230 Voltage References 231 Temperature Effects in General 233 Noise and Grounding 234 Printed CircuitBoard Layout 236 Statistical Tolerancing 239 Supply-Based References 240 Summary 241 10 StandardInterfaces 243 IEEE 1451.2 243 4–20 ma Current Loop 244 Fieldbus 245 11 Analog Toolbox 247 Microcontroller Supply and Reference 247 ResistorNetworks 249 Multiple Input Control 250 ACControl 252 Voltage Monitorsand Supervisory Circuits 254 Contents vii Driving Bipolar Transistors 254 Driving MOSFETs 257 ReadingNegative Voltages 261 Example Control System 262 Appendix AOpamp Basics 275 Opamp Configurations 275 GeneralOpamp Design Equations 279 Nonresistive Elements 280 Reversing the Inputs 281 Comparators 281 Hysteresis 283 Instrumentation Amplifiers 285 Appendix BPulse Width Modulation 287 WhyPWM? 287 Real Parts 292 FrequencyLimitations 292 Resolution Limitations 293 Power-Supply Considerations 294 PWM and EMI 294 Audio Applications 295 PWM Hardware 296 PWM Software 297 Appendix CUsefulURLs 299 Semiconductors 299 Motors 299 Other 300 Appendix DPython Code for Chapter 11; 301 Excel Data for Chapter4 Glossary 307 Index 311 viii Contents Preface Thereoftenseemstobeadivisionbetweentheanaloganddigitalworlds.Digital designers usually do not like to delve into analog, and analog designers tend to avoid the digital realm. The two groups often do not even use the same buzz- words. Even though microprocessors have become increasingly faster and more cap- able,therealworldremainsanaloginnature.Thedigitaldesignerswhoattempt tocontrolormeasuretherealworldmustsomehowconnectthisanalogenviron- ment to their digital machines. There are books about analog design and books about microprocessor design. This book attempts to get at the issues involvedin connecting the two together. Someone said about my firstbook, Embedded Microprocessor Systems: Real World Design,thatitneededmoreanaloginterfacinginformation.Ifeltthataddingthis material to that book would cause the book to lose focus. However, the more I thought about it, the more I thought that a book aimed at interfacing the real world tomicroprocessors could provevaluable.Thisbookistheresult.Ihopeit provesuseful. ix

Description:

Analog Interfacing to Embedded Microprocessors addresses the technologies and methods used in interfacing analog devices to microprocessors, providing in-depth coverage of practical control applications, op amp examples, and much more. A companion to the author's popular Embedded Microprocessor Syst