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Table of Contents · Page i Table of Contents Preface.........................................................................................................................v Audience and Teacher’s Guide......................................................................................v Conditions of Duplication...............................................................................................vi Foreign Translations......................................................................................................vi Special Contributors......................................................................................................vi Chapter #1: Analog Voltage and Binary States.......................................................1 Introduction to Analog and Digital...................................................................................1 Parts Required...........................................................................................................2 Building the Analog and Digital Comparator..............................................................7 Programming the Project...........................................................................................9 What have I learned?...............................................................................................15 Questions.................................................................................................................16 Challenge!................................................................................................................16 Why did I learn it?....................................................................................................17 How can I apply this?...............................................................................................17 Chapter #2: Introduction to Bit Crunching............................................................19 Basic Comunication......................................................................................................19 Parts Required.........................................................................................................19 Building the Circuit...................................................................................................20 Programming the Project.........................................................................................22 Parallel and Serial Transmission..............................................................................30 Reprogramming to Receive Serial Data...................................................................31 What have I learned?...............................................................................................37 Questions.................................................................................................................38 Challenge!................................................................................................................38 Why did I learn it?....................................................................................................39 How can I apply this?...............................................................................................39 Chapter #3: Basic Analog to Digital Conversion...................................................41 Build Your Own Digital DC Voltmeter...........................................................................41 Parts Required.........................................................................................................42 The Potentiometer - A Source of Variable Voltage..................................................42 The ADC0831 Integrated Circuit - An 8-bit Analog to Digital Converter..................43 Build It......................................................................................................................45 Program It................................................................................................................45 Binary to Decimal Conversion Revisited..................................................................52 Calculate Voltage.....................................................................................................54 Resolution................................................................................................................61 Calibration................................................................................................................62 Page ii · Basic Analog and Digital What have I learned?...............................................................................................63 Questions.................................................................................................................64 Challenge!................................................................................................................64 Why did I learn it?....................................................................................................65 How can I apply this?...............................................................................................65 Chapter #4: Basic Digital to Analog Conversion..................................................67 Build a Resistive Ladder Network.................................................................................67 Parts Required.........................................................................................................68 Build It......................................................................................................................69 Program It................................................................................................................70 Addressing...............................................................................................................76 The Voltage Follower...............................................................................................81 What have I learned?...............................................................................................85 Questions.................................................................................................................86 Challenge!................................................................................................................86 Why did I learn it?....................................................................................................87 How can I apply this?...............................................................................................87 Chapter #5: Time Varying Signals..........................................................................89 Parts Required.........................................................................................................90 Program It................................................................................................................91 The Pulse Train........................................................................................................97 The Sine Wave and Pulse Width Modulation (PWM)............................................100 Reprogram the Circuit for Musical Notes...............................................................102 What have I learned?.............................................................................................104 Questions...............................................................................................................105 Challenge!..............................................................................................................105 Why did I learn it?..................................................................................................106 How can I apply this?.............................................................................................106 Chapter #6: Recording Frequency Data..............................................................107 Parts Required.......................................................................................................107 Build It....................................................................................................................108 The Output.............................................................................................................111 Program It..............................................................................................................114 What have I learned?.............................................................................................119 Questions...............................................................................................................120 Challenge!..............................................................................................................120 Why did I learn it?..................................................................................................121 How can I apply this?.............................................................................................121 Chapter #7: Digital to Analog the Easy Way using PWM...................................123 Parts Required.......................................................................................................126 Table of Contents · Page iii Build It....................................................................................................................127 Program It..............................................................................................................129 What have I learned?.............................................................................................137 Questions...............................................................................................................138 Challenge!..............................................................................................................138 Why did I learn it?..................................................................................................139 How can I apply this?.............................................................................................139 Chapter #8: Light Meter Gizmo with R/C Time Constants..................................141 Parts Required.......................................................................................................144 Build It....................................................................................................................144 Program It..............................................................................................................146 Do the Math............................................................................................................150 What have I learned?.............................................................................................152 Questions...............................................................................................................153 Challenge!..............................................................................................................153 Why did I learn it?..................................................................................................154 How can I apply this?.............................................................................................154 Appendix A: Parts Listing and Sources...............................................................157 Appendix B: Resistor Color Code.........................................................................159 Index........................................................................................................................161 Page iv · Basic Analog and Digital Preface · Page v Preface The personal computer brought in a whole new era of electronic sophistication. With it, we have immense amounts of digital computing power located right at our desk. Computers work well when they are connected to each other, and digital data can be transferred quite reliably from machine to machine. However, the minute you wish to connect a digital computer to some “real world” device (such as a wind speed indicator or fuel level sensor) you need to design a circuit that interfaces an analog device to the digital computer. In many cases, this involves the conversion from an analog voltage to a digital representation of that voltage. This set of Stamps in Class experiments will explore many of the basic principles of interfacing analog devices to digital microcontrollers. Many times this involves the use of easy-to-use commands built right into the BASIC Stamp, and at other times requires the use of a an “analog to digital converter”. Why should we be interested in converting from analog to digital? Many different aspects of our lives are dependent upon this conversion process. Some are not too critical to our survival like compact disc players, telephone systems, and music. Others, however, might be critical. Medical equipment and sensors often require analog to digital and digital to analog conversion. The Basic Analog and Digital text will be revised and updated continually based on feedback from students and educators. Version 1.4 was edited to change from a 100 kΩ to a 10 kΩ potentiometer due to supply issues. Additionally, program listings PL3_1R0.bs2 and PL4_1R0.bs2 were updated to accommodate modification for several ADC0831 chips connected to the same CLK (clock) and D0 (data) lines. Pagination remains similar if not identical to Version 1.3. AUDIENCE AND TEACHERS GUIDE The audience for this text is ages 17 and above. This guide can be used as a complete book to introduce analog and digital concepts in a class, or as a reference to obtain detailed explanations about hardware and techniques used in other Stamps in Class Student Guides. Page vi · Basic Analog and Digital The answers to these experiments present no impossible or very difficult technical hurdles, and could be solved with a bit of patience. Instructors could participate in an Educator’s Forum to obtain support or Teacher’s Guides if they are available. CONDITIONS OF DUPLICATION Parallax grants the user a conditional right to download, duplicate, and distribute this text without Parallax's permission. This right is based on the following conditions: the text, or any portion thereof, may not be duplicated for commercial use; it may be duplicated only for educational purposes when used solely in conjunction with Parallax products, and the user may recover from the student only the cost of duplication. This text is available in printed format from Parallax, Inc. Because we print the text in volume, the consumer price is often less than typical retail duplication charges. FOREIGN TRANSLATIONS Parallax educational texts may be translated to other languages with our permission (e- mail [email protected]). If you plan on doing any translations please contact us so we can provide the correctly-formatted MS Word documents, images, etc. We also maintain a discussion group for Parallax translators which you may join. This will ensure that you are kept current on our frequent text revisions. SPECIAL CONTRIBUTORS Version 1.0 of this text was written mostly by Andy Lindsay based on a manuscript submitted by Matt Gilliland, original author of What's a Microcontroller? and the ever- popular Microcontroller Application Cookbooks. Andy wrote this text during his senior year at California State University, Sacramento, where he studied Electrical and Electronic Engineering. This was his first of many Stamps in Class texts that he has revised and/or authored. Andy is also is a contributing author of several papers that address the topic of microcontrollers in pre-engineering curricula. When he’s not writing educational material, Andy does product engineering for Parallax.