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Design Requirement/Constraints

Design Requirement/Constraints. Ref: Voland, G., Engineering by Design. Addison Wesley, 1999 & Larry Hand, Peavey Electronics, 2000. So you have figured out what you are going to do (Problem Statement), what next?. Create the technical formulation of the problem!.

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Design Requirement/Constraints

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  1. Design Requirement/Constraints Ref: Voland, G., Engineering by Design. Addison Wesley, 1999 & Larry Hand, Peavey Electronics, 2000

  2. So you have figured out what you are going to do (Problem Statement), what next? Create the technical formulation of the problem!

  3. A technical formulation takes an idea and translates it to an engineering context, complete with relevant objective technical and practical design constraints and appropriate theory and design methodologies needed to address the design.  It translates a design idea into a set of related, feasible engineering specific problems.

  4. Constraints are a “Good Thing” • Define the boundaries within which the search for solutions must be conducted • Enhance the effectiveness of the design • Avoid designs that are illegal or hazardous • Make designs economically viable

  5. Types of Constraints or Specifications • Can be broken down several ways Example: Bus specification Physical (dimensions, connectors, pins) Functional (arbitration protocol, read cycle) Electrical (impedance, max/min signal levels) • We will use • Technical Design Constraints • Practical Design Constraints

  6. Technical ConstraintsRequirements on which technical aspects of the design hinges • Signal tolerances (> 30% duty cycle clock at 1MHz +/-1%) • Supply current range (.5 mA min to 100 mA max) • Power efficiency (83% supply efficiency at rated load) • Speed (interrupt service latency < 1 S) • Conversion rate (12-bit conversion at 500Ksamples/sec) • Transmission distance (100 M with unobstructed view) • Quantization error (+,- 5mV) • Frequency response (20 Hz to 20 KHz, +/- 3 dB) • Signal-to-noise ratio (50 dB min)

  7. Practical Design ConstraintsBroader issues affecting design’s success • Economic • Environmental • Sustainability • Manufacturability • Ethical • Health and Safety • Social and Political

  8. Economic • Limits on Production Cost • Depreciation of Equipment • Operating Cost • Service or Maintenance Requirements • Existence of Competitive Solutions in the Marketplace

  9. How is Cost Determined(Note that cost is NOT price) • Material Cost • Labor Cost • Manufacturing Burden • Selling, General, and Administrative Expense (SG&A)

  10. Example Case:How Much does it Cost • Material Cost --- 52% of Total Cost • Unit Price * Quantity for all (Bill of Materials) BOM items • Labor Cost --- 8% of Total Cost • Direct labor or value added labor required to manufacture the product

  11. How Much Does it Cost • Manufacturing Burden --- 17% of Cost • Indirect Labor • Utilities • Facilities • Employee Benefits • Depreciation, rent, etc..

  12. How Much Does it Cost • Sales/General and Administrative -- 23% • Cost of Selling the Product • Sales commission • Advertising • Service and Warranty • Corporate Management • Research and Development • Bad Debt, etc..

  13. Environmental • Temperature Ranges • Moisture Limits • Dust Level • Intensity of Light • Noise Limits • Potential Effects Upon People or Other Systems

  14. Sustainability • If you birth it, It’s always your baby • Customer complaints • Obsolete & sole-source Parts • Warranty claims and field failures • Specification changes in standard components

  15. Manufacturability • Programs for Automated Assembly Equipment • Axial Sequencer and Insertion • Radial Insertion • DIP Socket and IC insertion • Surface Mount Chips, IC’s, Odd Shaped Components • Automated Test

  16. More things to consider • Mechanical Design and Packaging • Space Allocation or Dimensional Requirements • Weight • Material Characteristics • Power Requirements • Protect Unit During Shipment • Attractive at Point of Sale • Advertising • OEM or Consumer packaging

  17. Legal • Governmental Safety Requirements • Environmental or Pollution Control Codes • Production Standards

  18. Health and SafetyHuman Factors/Ergonomics • Users Characteristics • Strength • Intelligence • Anatomical Dimensions • Visual Acuity • Hearing Discrimination • Reaction Time • Reading Skills

  19. UL CSA FCC NOM CE NEMKO DEMKO VDE IRAM SASO SANZ SAA JIS and more..... Social and PoliticalAgency Approvals

  20. Sources of Engineering Standards • Companies • Engineering Societies • Governments (U. S., others) • Special Interest Groups • Federations of Private and Public Interests (American and International) • Independent Laboratories

  21. ACM (Association of Computing Machinery) AES (Audio Engineering Society) ANSI (American National Standards Institute) EIA (Electronic Industries Association) ESD (Electrostatic Discharge Association) IEEE (Institute of Electrical and Electronics Engineers) ISO (International Standards Organization) ITU (International Telecommunications Union) OSHA (Occupational Safety & Health Administration) PCI SIG (PCI Bus Special Interest Group) UL (Underwriters Laboratories) USB Developers (Universal Serial Bus Developers Forum) ExamplesSee http://www.dma.org/~rohrers/subject/standorg.htm for extensive list of links

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