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

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

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

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?