Approach

Design Definition with Synthesis and Analysis of Alternative Solutions Leading to

a Decision

General Engineering ProcessProblem or Expression of Need

Design Constraints

Evaluation and Synthesis of Alternative Solutions

Analysis (perhaps including experimentation)

Decision (justification of selected solution)

Solution

Adapted from Salt & Rothery, Design for Electrical and Computer Engineers

Elements of Approach

How Design Approach Relates to Design Description

Elements of Approach

Design Description

Design Tradeoffs

Background & Theory

FunctionalOverview

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)

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

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

Block Heater ExampleFirst Approach, First Attempt

Analysis reveals that LEDs must carry 4 amperes of forward current – not practical due to LED cost

1 ohm

Block Heater ExampleFirst Approach, Second Attempt

More analysis using flux equation reveals realistic solution

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)

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.

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

Summary of Approach Components

1. Functional Overview2. Theory & Background3. Synthesis of Design Options4. Analysis of Options5. Justification of Design Decision6. Detailed Design Description