lead software engineer: colin mccune lead hardware engineer: andrew phillips test engineer: lauren...
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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)
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