Approach

1
Approach

• Design Definition with Synthesis and Analysis of
  Alternative Solutions Leading to a Decision

2
General Engineering Process
Problem or Expression of Need
Design Constraints
Evaluation and Synthesis of Alternative Solutions
Elements of Approach
Analysis (perhaps including experimentation)
Decision (justification of selected solution)
Solution
Adapted from Salt Rothery, Design for
Electrical and Computer Engineers
3
How Design Approach Relates to Design Description
Elements of Approach
Functional Overview
Design Description
Background Theory
Design Tradeoffs
4
Block Heater ExampleGeneral Problem Constraints

• Sometimes automobile block heater power sources
  are dead (unpowered)
• Sometimes heaters burn out (open)
• Heaters use120-Volt Power at 300 to 400 Watts
• Want indicator in extension cord to warn users of
  potential problems (then could reset breaker or
  run car during day)

5
Block Heater ExampleEngineering Problem

• Design detection device integrated into extension
  cord
• Detect difference between 0.5 and 3.0 amperes
• Present binary conclusion to user
• Consume less than 5W
• Integrated manufacturing cost less than 6

6
Block Heater ExampleApproach

• Functional Overview
• Diagram of System
• Broad description of needed functionality
• Background and/or Theory
• Types of binary indicators
• Implications of including in extension cord
• Possible Designs Evaluation of Alternatives
• Series indicator design
• Transformer coupled design
• Switch activated design
• Detail Design Description

7
Block Heater ExampleFirst Approach, First Attempt
1 ohm
Analysis reveals that LEDs must carry 4 amperes
of forward current not practical due to LED cost
8
Block Heater ExampleFirst Approach, Second
Attempt
More analysis using flux equation reveals
realistic solution
9
Block Heater ExampleSecond Approach, First
Attempt
Alternate working solution found. Even though it
cost less, it is rejected because the switch
would have to be depressed (not hands-free
operation)
10
Evaluation of Alternatives

• Design Constraints are the yardstick against
  which alternatives are evaluated
• Cost and performance usually the main factors
• Solution will be near optimal (never perfect)
• Other issues are reliability, maintainability,
  sustainability, manufacturability, time to
  market, etc.

11
Design Methodologies Used in Approach

• Choice of methodology will depend on project
  specifics
• Objective is to identify the best solution with
  minimum engineering cost
• Usually involves triangulation to develop
  confidence in design
• Analysis
• Simulation
• Experimentation

12
Summary of Approach Components

• Functional Overview
• Theory Background
• Synthesis of Design Options
• Analysis of Options
• Justification of Design Decision
• Detailed Design Description