Wireless Digital Voltmeter. (How to Build, Electronic Project) A Major Qualifying Project Report. Worcester Polytechnic Institute

1 | P a g e TABLE OF CONTENTS Abstract.........................................................................................................6 Executive Summary........................................7 Acknowledgements............................................................10 Introduction.............................................................11 1. Background . 13 1.1 Defining Project Goals .. 13 1.2 Background Research . 14 1.2.1 Digital Voltmeters .. 15 1.2.2 Wireless Communication . 28 1.2.3 Microcontroller .. 35 1.2.4 System Power (Battery) . 37 2. Design Details . 41 2.1 Overall Design .. 42 2.1.1 DVM Block (Analog Front-End) . 43 2.1.2 Wireless Communication . 44 2.1.3 Microprocessor (ADUC845) . 47 2.1.4 System Power. 49 2.2 System Block Digram . 55 3. Functionality Testing and Results . 56 3.1 The AD7799 (Voltmeter Front-End) .. 56 3.2 The AduC845 (Mircoprocessor) . 61 3.3 RN-41 (Bluetooth Module) . 65 3.4 C# Application (Windows Application) . 68 4. Final Product . 70 4.1 Complete Schematic . 70 4.1.1 Analog Front-End (AD7799) and Microprocessor Circuit..........71 2 | P a g e 4.1.2 Bluetooth RN-41 Circuit........73 4.1.3 Battery Charging Circuit (using MAX1811)..............................................74 4.1.4 Voltage Regulation (for AVDD and VREF)...................................................75 4.2 Final PCB Layout . 77 4.3 Product Testing . 80 5. Future Improvements and Recommendations .. 83 6. Conclusion . 84 Appendix A - Battery Research......................86 Appendix B -Detailed Final Schematic.......91 Appendix C - PCB Layout..................................................................................92 Appendix D - Part List...................94 Appendix E - ADuC845(C code in IAR KickStart)........95 Appendix F - C# Code (Microsoft Visual Studio)....................................................108