Building a Typical Electronic Project in Senior Design Peter Wihl (former Guest Lecturer) Scope • The purpose of this presentation is to introduce you to the process of implementing a circuit design into an actual working design solution. Process Overview • • • • • • • • • • Requirements* System Architecture* Component Selection Mechanical/Packaging Design Detailed Board Design Layout Fabrication Board Assembly Testing and Debugging Design Changes/Workarounds *Must be completed prior to this process. Lecture Example Building a distance measuring sensor device Requirements • Must be completed prior to board design and implementation • A detailed list of what the system must do • Not how it does it. • Should be well thought out and clear Requirements Example • Must be wireless • Must measure in the range from 0.30 to 2.5 meters • Must have a resolution of at least +/- 10 cm • Must interface with a microprocessor on both transmitter and receiver side using 5.0V CMOS Logic System Architecture • A detailed block diagram • Includes all significant signal paths • Include signal direction, width, and type System Architecture Example RF_Pulse Fc = 433 MHz RF Tx RF Rx RF_Detect US_Pulse Tone Decoder OpAmp OSC 40 KHz Voff = 2.5 V Vpp = 5 V Voff = 0 V Vpp = 2 mV Voff = 0 V Vpp = 2 V US_Detect Component Selection • Identify the best component solution for each design block in the system architecture • Identify all necessary support components for each major design block component • Explore different package options if available • Take any mechanical requirements into account Component Selection Example • • • • • • • • • Reynolds 433 MHz Tx/Rx Module (COTS) US Transducers Tx/Rx 40 kHz Crystal 74’Inverter 74’NAND LMV722 OpAmp from National LMC567 Tone Decoder from National Headers SM Resistors and Caps Mechanical/Packaging Design • Identify the mechanical or packaging requirements of your design • May possibly have to select components based on these requirements • Identify possible layout restrictions • Think about non-circuit requirements, i.e. mounting and packaging Mechanical Design Example Mechanical Design Example Mechanical Design Example Mechanical Design Example Mechanical Design Example Detailed Board Design • Build your schematics in a schematic capture program e.g. OrCAD • Once your schematic is complete run a design rule check (DRC) • When schematic is done convert to netlist for layout Detailed Design Example Detailed Design Example Layout • The process of designing the PCB • Requires a schematic netlist, the “Bill of Materials” or BOM and all package mechanical information Layout Example Fabrication • This is the process of placing the components on the PCB • Can be done by hand or machine Fabrication Example • See sample Board Assembly • The process of populating the PCB with all components • This includes ICs, Resistors, Caps Connectors and LEDs, etc. Board Assembly Example Testing and Debugging • You need to develop a thorough and complete test plan for your board. • Should include a check list of steps in a test procedure • Each step should include status of all board voltages • Use continuity, clock signals and/or signature analyzer to verify net connections Design Changes/Workarounds • White wire part of the board • Must create detailed step by step instructions on white wire corrections • Sometimes minor design changes are needed when an error is found in the board design • May have to be done in software Conclusion • This process consists of different types of engineers working together. • Depending on system complexity and level of design reuse this process can take from 1 to 18 mouths. • Any questions?