Design RequirementConstraints

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Design Requirement/Constraints

• Ref Voland, G., Engineering by Design. Addison
  Wesley, 1999
• Larry Hand, Peavey Electronics, 2000

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Proof of Concept?
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After Proof of Concept, What Next?

• Vacation
• Big Bonus
• Two Attaboys
• Another Project
• Technical Formulation, Physical Design, and
  Transition to Manufacturing

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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.
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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

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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

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Technical ConstraintsRequirements on which
technical aspects of the design hinges

• Signal tolerances (gt 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 lt 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)

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Practical Design ConstraintsBroader issues
affecting designs success

• Economic
• Environmental
• Sustainability
• Manufacturability
• Ethical
• Health and Safety
• Social and Political

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Economic

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

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How is Cost Determined(Note that cost is NOT
price)

• Material Cost
• Labor Cost
• Manufacturing Burden
• Selling, General, and Administrative Expense
  (SGA)

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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

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How Much Does it Cost

• Manufacturing Burden --- 17 of Cost
• Indirect Labor
• Utilities
• Facilities
• Employee Benefits
• Depreciation, rent, etc..

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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..

14
Environmental

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

15
Sustainability

• If you birth it, Its always your baby
• Customer complaints
• Obsolete Parts
• Unique Parts
• Warranty claims and Field Failures
• Specification changes in standard components

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Manufacturability

• Programs for Automated Assembly Equipment
• Axial Sequencer and Insertion
• Radial Insertion
• DIP Socket and IC insertion
• Surface Mount Chips, ICs, Odd Shaped Components
• Automated Test

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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

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Manufacturing Deliverables

• PCB Assembly Drawings
• Gerber Files
• Mechanical Fabrication Drawings
• Functional Test Procedure
• Technical Specifications
• Trouble Shooting procedures
• Your Experience and Knowledge

20
Printed Circuit Board Design

• Component Placement
• Input/Output locations
• Mounting Considerations
• Technology Selection
• Restricted areas
• Minimize crossing count
• Thermal Management

21
Printed Circuit Board Design

• Electrical Considerations
• High Impedance Nodes
• Differential signal pairing
• Shielding for Magnetic and Capacitive Coupling
• Transmission Line Effects- OverShoot and Ringing
• EMI/EMC
• Ground is NOT Ground......

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Printed Circuit Board Design

• Manufacturing Considerations
• Component Spacing
• Orientations
• Hole Sizes
• Insertion Tooling Restrictions
• Tooling Holes
• Panelization

23
PCB Manufacturing Flow

• Top Side SMT
• DIP ICs and Sockets
• Axial leaded components
• Bottom side SMT
• Radial leaded components

• Hand Assembly
• Wave Solder
• Touchup and Inspect
• Precheck

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Parts Approval and Procurement

• Custom Parts
• Product Differentiation
• Protect Trade Secrets and Intellectual Property
• Extensive Specifications/Documentation
• If you change your mind, Theyre still yours
• Requires Accurate Forecasting

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Parts Approval and Procurement

• Approved Vendor List (AVL)
• Lead Times
• Minimum Quantities
• Packaging/Delivery Options
• Bulk
• Tape and Reel
• Tape and Ammo
• Trays or Tubes

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Parts Approval and Procurement

• Standard Parts
• Multiple Sourced
• Cost Effective
• Minimal Specifications required
• Improved response to demand changes
• Note Not all parts are created equal....
• Single Sourced
• Unique or Patented Technical Advantage
• An Act of Nature could shut you down!
• Know Who Youre Dealing With

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Legal

• Governmental Safety Requirements
• Environmental or Pollution Control Codes
• Production Standards

30
Health and SafetyHuman Factors/Ergonomics

• Users Characteristics
• Strength
• Intelligence
• Anatomical Dimensions
• Visual Acuity
• Hearing Discrimination
• Reaction Time
• Reading Skills

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Social and PoliticalAgency Approvals

• UL
• CSA
• FCC
• NOM
• CE
• NEMKO
• DEMKO

• VDE
• IRAM
• SASO
• SANZ
• SAA
• JIS
• and more.....

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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

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ExamplesSee http//www.dma.org/rohrers/subject/s
tandorg.htm for extensive list of links

• 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)

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Documentation (Safety and Ethical Issues)

• User Manual
• Technical Specifications
• Service Manual
• Assembly Directions
• Marketing Support
• Advertising Copy

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Oops....

• Tolerances
• Incomplete Beta Testing
• Parts Availability
• Poor Manufacturing Yield
• Poor Reliability
• Marketing Redirection/Feature Addition
• Murphys Law- ECNs and rework
• Its Always yours..

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Engineering Change Orders

• ECOs document a change that manufacturing will
  implement
• Disposition of existing inventory
• Disposition of Work In Process
• Reason for Change
• Cost/Performance/Schedule Impacts

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Engineering Change Orders

• Safety - Liability
• Recall, Disposition of units already sold
• Obsolete inventory