Lead Software Engineer: Colin McCune

Lead Hardware Engineer: Andrew Phillips

Test Engineer: Lauren Cummings

Cost Engineer: Xiaolong Zhang

1.Establish customer needs and engineering specifications.

2.Communicate project risks and mitigation plans.

3.Display and defend design decisions made.

4.Receive feedback on design decisions made.

5.Effectively communicate design decisions made to P12442.

Goals of this System Design Review

Needs

Importance

Description Comments/Status

1 3 Cheap cost of system Component cost including PCB if applicable

2 3 Plan to couple to team 12442’s stove.

 

3 3 User-friendly operation Minimal user interaction

4 2 Rugged design Survive crush and drop test

5 3 Safe to operate  

6 3 Fan runs the entire duration of cooking

 

7 2 Operational in Harsh Environments Exposure to Rain, Moisture, Heat and Salinity

8 2 Fan runs at start-up Multiple start/restart cycles

9 2 Ability to charge USB device  

11 1 System must be transportable  

12 1 5 year life span (2x use per day)  

Customer Needs

Importance Scale: 1 - Low Importance, 2 - Moderate Importance, 3 - High Importance

Spec

Customer

Need

Description Importance

Units Marginal

Target

Comments/Status

1 1 Component Cost 3 $ 15 10 Including any PCB, for quantities of 1-10K.

2 2, 6, 8 Power supplied to fan

3 W 1.2 1.0  

3 2, 6, 8 Voltage supplied to the fan

3 V 12 4 Converter needs to be adjustable.

4 8 Amount of startups that can be performed on battery power.

3 Start up 1 3 A system startup is the 20 minute period in which the fan is powered by the battery only.

5 3 User interaction tomaintain proper system operation

3 Actions 1 0 The user shouldn’t need to perform adjustments to properly operate electronics.

6 2 Electrical connections provided to the stove.

3 Connections

6 4 2 input wires, 2 output wires

7 4, 7, 11 Survive drop test 2 Drops 20 20 Survive 20, 2 meter drops.

8 4, 7, 11 Survive crush test 2 PSI 3 5 Enclosure must survive being stepped on by Hanzlik

10 4, 7, 11 Survive a rain test 2 Hours .5 2 Put it in the shower.

Engineering Specifications 1-10

Importance Scale: 1 - Low Importance, 2 - Moderate Importance, 3 - High Importance

Spec Customer Need

Description Importance Units Marginal Target Comments/Status

11 4, 7, 11 Survive a humidity test

2 hours 1 5 Place the unit in an above 90% enclosed area.

12 5, 10 Enclosure surface temperature

2 °C 70 55 Surface of enclosure should not exceed 55 °C during operation.

13 3, 5 User interaction to protect system

2 Actions 1 0 The user should not need to perform an action to protect the system

14 9 USB output power 2 W 2.5 +/- 5%

2.5 Margin derived from specs 15, and 16

15 9 USB output voltage

2 V 5 +/- 5% 5 From USB spec

16 9 USB output current

2 A .45 +/- .05

.45 From USB spec

17 9 Number of charges from battery

2 Charges 1 2  

18 11 Product Life Span 2 Hours 1500 11,000

Assume 3 hours/use, 2 uses/day, for 5 years

19 10 System Weight 1 lbs 2 3 Include battery packs

20 10 Enclosure Volume 1 In 5x5x5 3x3x1.5

Include battery packs

Engineering Specifications 10-22

21 3 User actions duringoperation cycle

1 # 2 0

22  3 Fuse high cost components

1 Dollars 1 3 Put fuses on lines that supply high cost components.

Functional Decomposition: Maximum Power Point Tracker (MPPT)

Function Decomposition: Enclosure System

Circuit DesignPros and Cons of the Circuit Architecture

Microcontroller Points

Pros 

Lower power consumption 2Simple to upgrade 1

Smart Circuitry possible 2Easier to implement an MPPT 3

ConsHigher Cost vs. Analog Circuit -2

More complex -2Software failure is possible -1Difficult to repair in the field -1

Result 2Analog Circuit Points

Pros  

Lower cost 2Easy to repair 1More robust 2

Pre-made schematics available 2

ConsDifficult to design -2

High power consumption -2Difficult to upgrade -1

Result 2

Pros and Cons of the MPPT AlgorithmsPerturb and Observe Points

ProsVery effective 2Easy to implement 3

Cons Can oscillate under rapid state changes -3Result -1

Incremental Conductance PointsPros Most accurate 2

ConsCan oscillate -3Difficult to implement -3

Result -4Constant Voltage Points

Pros

Very easy to implement 3Easily adjustable 1Simple operation 2Good performance under rapid changes 3

ConsUses an estimate for MPPT tracking -1Not most efficient -2

Result 6

MPPT DesignPros and Cons of the Charging Circuits

Smart Charger Points

ProsRapid charging(85% in 60 min) 3Adaptable to different chemistries 1Lengthens battery life 2

Cons

Voltage, temperature, and current monitors needed -3Difficult to implement -2Needs a microcontroller -0/-3*

Result 1/-2Trickle Charger Points

Pros Lengthens battery life 2Minimizes damage to batteries 2

Cons

Long time to charge -2Designed to high capacity batteries -1Microcontroller needed for NiMH -0/-3*Risk of overcharging -2

Result -1/-4

*Dependent on design decisions

BatteriesPros and Cons of the Batteries

Nickel Cadmium (NiCd)Poin

tsNickel Metal Hydride (NiMH)

Points

Pros

Cheap 3

Pros

Cheap cost 3Capable of high rate of discharge 2 Low memory 2Simple to charge 2 Robust 2

Robust 2Useful in high current drain operation

2

Cons

Memory Issues -3 Non-toxic 1Lower capacity -3

ConsFewer life cycles -3

Toxic -1 Very difficult to charge -3Heavy -2 Shorter shelf life -2

Result

  0Resul

t  4

  Lead AcidPoint

s

Lithium (Li+)Poin

tsPros

Long service life 2

Pros

Higher capacity than NiMH 3High discharge current possible

2

50% lighter than NiCd 1 High Capacity 2No memory 2

Cons

Heavy -1

Relatively simple to charge 2Longer to charge compared to batteries

-3

Long lifetime 2 Low power to weight ratio -1

Cons

Expensive -3Resul

t  1

Not robust -2      Poor performance in high current situations

-2      

Toxic -1      Resul

t  2

Block Diagram 1

Block Diagram 2

Power from TEG with a 75 Degree Temperature Difference

Current (A)

Voltage(V)

Power(W)

0.8 2 1.6

Power from TEG with a 175 Degree Temperature Difference

Current (A)

Voltage(V)

Power(W)

1.186 3.209 3.807

Power from TEG with a 225 Degree Temperature Difference

Current(A)

Voltage(V)

Power(W)

1.360 3.769 5.124

TEG Voltage and Current Model

Importance Scale: 1 - Low, 2 - Moderate, 3 - High

ID Risk Item Effect Cause Likelihood Severity Importance Action to Minimize Risk Owner

1 Exceeding target cost per 

unit.

Other features of the end product may be not included.

Component cost.Manufacturing 

cost.3 3 9

Minimize the amount of components.

Increase the functionality of existing components (ex: have more tasks run within the uC).

Xiaolong

2

P12442 does not provide sufficient 

temperature difference

Not enough power, features 

must be sacrificed, poor functionality

Insufficient communication between teams

3 3 9Effectively communicate with 

P12442 over generated temperature difference.

Colin

3Unable to program 

microcontroller

The MPPT will not be able to 

provide maximum power and the batteries will not charge 

properly.

Inexperience, difficulty, hardware 

complications.

2 3 6 Community support, professor and professional assistance

Lauren and Colin

4Device requires 

too much power.

Unit will not have full 

functionality.Unstable 

behavior when operated.

Poor design and component selection.

2 3 6

Design to be as power efficient as possible.

Utilize MPPT functions.Using the uC as much as possible.

Andrew

5 Device fails to operate.

The project will not be completed.

Poor designPoor project planning,

2 3 6Have at least weekly design meetings to look over designs.  Choose high quality parts that can handle and supply the required power with minimal losses.

Lauren

6Prototype construction 

time

Less time for de-bugging, failure to deliver on time

Poor planning, complex system.  Unforeseen circumstances

2 3 6Strict scheduling milestones, effective and 

reachable deadlines, component delivery time, ordering parts early enough

Colin

7

System cannot power fan during "warm up"

Stove will take longer to heat up and longer for the TEG to provide full 

power.

Component failure. Bug in the uC code. 

 Poor design.2 3 6 Design the unit to operate on battery power. 

 Ensure the uC operates correctly Andrew

8Going over development 

budget.

Difficult to be able to fund further development.

Poor planning 1 3 3Track spending

Ordering correct partsProper testing.

Xiaolong

9Battery charging difficulties

Decreased battery lifetime, system does not 

operate properly

Inexperience in the area, poor 

design2 3 6 Professor and professional assistance

Xiaolong and 

Andrew

10Complexity 

of operation

Sell less unitsImproper useReduce system 

lifetime

Poor Design 1 3 3 Minimize user interaction.Make simple to operate. Colin

11 Decreased reliability

Fewer sales.Unit will get 

damaged more often.

Poor part selection.Poor fabrication.Poor design.

1 3 3 Design the unit to be as robust as possible.Choose high-lifetime components. Lauren

12Power storage capacity

System start-up failure.

Cannot charge devices without 

a fire.

Poor system design.Poor system storage 

capacity.1 2 2 Use high-capacity storage to meet 

customer specs. Andrew

Project Schedule

Project Schedule (Continued)