September 2003 Chuck DiMarzio, Northeastern University 10379-2-1

The Design Process: Needs Assessment

Charles A. DiMarzio

GEU110

Northeastern University

September 2003 Chuck DiMarzio, Northeastern University 10379-2-2

The Design Process

NeedsAssessment

ProblemFormulation

Abstractionand Synthesis

Analysis

Implementation Ch. 2

3, 4, 5

6,7

8,9,10

11

• First Step: Needs• What Does This

Mean?• It’s Not So Easy!• Examples:

– Urban Transportation

– Power Grid

September 2003 Chuck DiMarzio, Northeastern University 10379-2-3

Different Perspectives on Needs

• The Best Solution

• The Best from Where We Are

• The Best We Can Afford

• Good Enough

• Short- vs. Long- Term Planning– eg. Buried Waste Disposal

September 2003 Chuck DiMarzio, Northeastern University 10379-2-4

Some Examples (1)

• Phone Numbers– “Sally, get me Mary,” 1507M, SU7-7777– 7, 10 and 11 digit dialing– Why the area codes

• 212 = NYC, 213 = LA• 312 = Chicago, 617 = BOS

– What Next?– Just for Fun for Boston People

• What Were Exchange Names of 536, 262, 268?

September 2003 Chuck DiMarzio, Northeastern University 10379-2-5

Some Examples (2)

• FM Radio, FM Stereo Radio

• MOKE Current Sensor, Magnetometer

• IVHS

• Wake Vortex Avoidance

• Glucose Monitor

• The Video Store vs. The Net

September 2003 Chuck DiMarzio, Northeastern University 10379-2-6

FM Stereo Radio

Transmitter 1

Transmitter 2

Receiver 1

Receiver 2

Leftsignal

Rightsignal

Leftspeaker

Rightspeaker

Why Not?

September 2003 Chuck DiMarzio, Northeastern University 10379-2-7

FM Stereo Radio

Transmitter 1

Transmitter 2

Receiver 1

Receiver 2

Leftsignal

Rightsignal

Leftspeaker

Rightspeaker

How it really works:4-Way Compatible

L+R

L-R

(L+R)+(L-R)

(L+R)-(L-R)Why?

(Carrier)

(Sidebands)

September 2003 Chuck DiMarzio, Northeastern University 10379-2-8

Mono Transmitter

Transmitter Receiver 1

Receiver 2

Leftspeaker

Rightspeaker

The Signal

(L+0)+(0)

(L+0)-(0)

(Carrier)

September 2003 Chuck DiMarzio, Northeastern University 10379-2-9

Mono Receiver

Transmitter 1

Transmitter 2

Receiver 1

Leftsignal

Rightsignal

ThespeakerL+R

L-R

(Carrier)

(Sidebands) Mono Transmitter and Receiver: An Exercise for the Interested Student

September 2003 Chuck DiMarzio, Northeastern University 10379-2-10

Other Perspectives

• Market Pull vs. Technology Push– A Key Question in the Research World

• Political Perspectives– Policy vs. Market

• Economic Perspectives– “Don’t Make it Too Cheap”

• Random Events

September 2003 Chuck DiMarzio, Northeastern University 10379-2-11

Brunelleschi’s Ox-Hoist

• Firenze, Summer 1420• What were the Needs?• How does it work?• Reference:

– King, Ross, Brunelleschi’s Dome, Penguin, New York, 2001. Pg. 59.

September 2003 Chuck DiMarzio, Northeastern University 10379-2-12

Other Examples

• Color TV from Black and White– 4-Way Compatibility and Bandwidth

• LED’s for Efficient Illumination– The Next New Thing???– The Color Problem?– Low Voltage DC vs. Higher Voltage AC– See Next Page

September 2003 Chuck DiMarzio, Northeastern University 10379-2-13

Lighting Efficiency

100

1000

10000

100000

1000000

1 10 100 1000 10000

Lig

ht

Ou

tpu

t, L

um

ens

Fluorescent

Hi PressureNaMetal Halide

Lo PressureNaIncandescent

94 Lumens/Watt at 7000K(Highest Efficiency)

20.7 Lumens/Watt at 3000K

Thanks to John Hilliar (NU MS ECE 1999) for finding lighting data from Joseph F. Hetherington at www.hetherington.com. 10 June 1998

683 Lumens/Watt for Green Light

Power Input, Watts