Transcript P12441: Thermoelectric Power Pack

Lead Software Engineer: Colin McCune
Lead Hardware Engineer: Andrew Phillips
Test Engineer: Lauren Cummings
Cost Engineer: Xiaolong Zhang
Goals of this System Design Review
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.
Customer Needs
Needs Importance
Description
Comments/Status
Component cost including PCB if applicable
1
3
Cheap cost of system
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)
Importance Scale: 1 - Low Importance, 2 - Moderate Importance, 3 - High Importance
Engineering Specifications 1-10
Spec Customer
Need
Description
Importance
Units
Marginal Target
Component Cost
3
$
15
10
Comments/Status
1
1
Including any PCB, for quantities of 110K.
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 to
maintain 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.
Importance Scale: 1 - Low Importance, 2 - Moderate Importance, 3 - High Importance
Engineering Specifications 10-22
Spec
Customer
Need
11
4, 7, 11
12
Description
Importance
Units
Marginal
Target
Comments/Status
Survive a humidity
test
2
hours
1
5
Place the unit in an above 90%
enclosed area.
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
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
19
10
System Weight
1
lbs
2
20
10
Enclosure Volume
1
In
5x5x5
21
3
User actions during
operation cycle
1
#
2
0
22
3
Fuse high cost
components
1
Dollars
1
3
Margin derived from specs 15,
and 16
11,000 Assume 3 hours/use, 2 uses/day,
for 5 years
3
Include battery packs
3x3x1.5 Include battery packs
Put fuses on lines that supply
high cost components.
Functional Decomposition: Maximum Power Point
Tracker (MPPT)
Function Decomposition: Enclosure System
Circuit Design
Pros
Cons
Pros and Cons of the Circuit Architecture
Microcontroller
Lower power consumption
Simple to upgrade
Smart Circuitry possible
Easier to implement an MPPT
Higher Cost vs. Analog Circuit
More complex
Software failure is possible
Difficult to repair in the field
Result
Pros
Cons
Result
Analog Circuit
Lower cost
Easy to repair
More robust
Pre-made schematics available
Difficult to design
High power consumption
Difficult to upgrade
Points
2
1
2
3
-2
-2
-1
-1
2
Points
2
1
2
2
-2
-2
-1
2
Pros and Cons of the MPPT Algorithms
Perturb and Observe
Very effective
Pros
Easy to implement
Cons Can oscillate under rapid state changes
Result
Incremental Conductance
Pros Most accurate
Can oscillate
Cons
Difficult to implement
Result
Constant Voltage
Very easy to implement
Easily adjustable
Pros
Simple operation
Good performance under rapid changes
Uses an estimate for MPPT tracking
Cons
Not most efficient
Result
Points
2
3
-3
-1
Points
2
-3
-3
-4
Points
3
1
2
3
-1
-2
6
MPPT Design
Pros and Cons of the Charging Circuits
Smart Charger
Rapid charging(85% in 60 min)
Pros Adaptable to different chemistries
Lengthens battery life
Voltage, temperature, and current monitors
needed
Cons
Difficult to implement
Needs a microcontroller
Result
Points
3
1
2
-3
-2
-0/-3*
1/-2
Trickle Charger
Lengthens battery life
Minimizes damage to batteries
Long time to charge
Designed to high capacity batteries
Cons
Microcontroller needed for NiMH
Risk of overcharging
Pros
Result
Points
2
2
-2
-1
-0/-3*
-2
-1/-4
*Dependent on design decisions
Batteries
Pros and Cons of the Batteries
Point
Nickel Cadmium (NiCd)
Nickel Metal Hydride (NiMH)
s
Cheap
3
Cheap cost
Capable of high rate of discharge
Pros Simple to charge
Robust
2
2
Pros
2
Memory Issues
Lower capacity
Cons
Toxic
Heavy
-3
-3
-1
-2
Result
0
Higher capacity than NiMH
50% lighter than NiCd
Pros No memory
Cons
Point
s
3
2
Robust
Useful in high current drain
operation
2
Non-toxic
Fewer life cycles
Cons Very difficult to charge
Shorter shelf life
Result
1
2
Relatively simple to charge
2
Long lifetime
2
Expensive
-3
Not robust
Poor performance in high current situations
-2
-2
Pros
2
1
-3
-3
-2
4
Points
Long service life
2
High discharge current possible
2
High Capacity
Heavy
Longer to charge compared to
Cons
batteries
Low power to weight ratio
Result
3
Low memory
Lead Acid
Lithium (Li+)
Points
2
-1
-3
-1
1
Block Diagram 1
Block Diagram 2
Power from TEG with a 75 Degree
Temperature Difference
5.0%
1.6
4.5%
4.0%
1.4
3.5%
Power (W)
1.2
Current (A) Voltage(V) Power(W)
0.8
2
1.6
Efficiency
1.8
3.0%
1.0
2.5%
Power
0.8
2.0%
Module
Q
1.5%
Efficien
cy
0.6
0.4
1.0%
0.2
0.5%
0.0
0.0%
0
0.5
1
Current (A)
1.5
Power from TEG with a 175 Degree
Temperature Difference
4.0
5.0%
Current (A) Voltage(V) Power(W)
1.186
3.209
3.807
4.5%
3.5
4.0%
3.0
2.5
3.0%
2.0
2.5%
2.0%
1.5
1.5%
1.0
1.0%
0.5
0.5%
0.0
0.0%
0
0.5
1
Current (A)
1.5
2
2.5
Efficiency
Power (W)
3.5%
Power from TEG with a 225 Degree
Temperature Difference
6.0
5.0%
Current(A) Voltage(V) Power(W)
1.360
3.769
5.124
4.5%
5.0
4.0%
3.0%
3.0
2.5%
2.0%
2.0
1.5%
1.0%
1.0
0.5%
0.0
0.0%
0
0.5
1
Current (A)
1.5
2
2.5
Efficiency
Power (W)
3.5%
4.0
TEG Voltage and Current Model
ID
Risk Item
Effect
Cause
Not enough
power, features
2
must be
sacrificed, poor
functionality
The MPPT will
not be able to
Unable to
provide
3
program
maximum power
microcontroller and the batteries
will not charge
properly.
Unit will not
have full
Device requires
functionality.
4
too much
Unstable
power.
behavior when
operated.
Action to Minimize Risk
Owner
Xiaolong
3
3
9
Minimize the amount of
components.
Increase the functionality of
existing components (ex: have
more tasks run within the uC).
Insufficient
communication
between teams
3
3
9
Effectively communicate with
P12442 over generated
temperature difference.
Colin
Inexperience,
difficulty,
hardware
complications.
2
3
6
Community support, professor
and professional assistance
Lauren and
Colin
6
Design to be as power efficient as
possible.
Utilize MPPT functions.
Using the uC as much as possible.
Andrew
Other features of
Component cost.
Exceeding
the end product
1
Manufacturing
target cost per
may be not
cost.
unit.
included.
P12442 does
not provide
sufficient
temperature
difference
Likelihood Severity Importance
Poor design and
component
selection.
2
3
Importance Scale: 1 - Low, 2 - Moderate, 3 - High
Device fails to The project will
5
operate.
not be completed.
6
Poor design
Poor project
planning,
Poor planning,
Prototype
Less time for decomplex
construction bugging, failure to
2
system. Unforeseen
time
deliver on time
circumstances
Stove will take
System
longer to heat up Component failure.
cannot power
7
and longer for the
Bug in the uC
fan during
TEG to provide full code. Poor design.
"warm up"
power.
8
2
Going over Difficult to be able
development to fund further
budget.
development.
Poor planning
2
1
Have at least weekly design meetings to look over
designs. Choose high quality parts that can handle
and supply the required power with minimal losses.
3
6
3
Strict scheduling milestones, effective and reachable
6 deadlines, component delivery time, ordering parts
early enough
3
6
Design the unit to operate on battery power. Ensure
the uC operates correctly
Andrew
3
Track spending
Ordering correct parts
Proper testing.
Xiaolong
3
Lauren
Colin
Battery
charging
difficulties
Decreased
battery lifetime,
system does not
operate
properly
Inexperience in
the area, poor
design
2
3
6
Professor and professional assistance
Xiaolong
and
Andrew
Complexity
10
of
operation
Sell less units
Improper use
Reduce system
lifetime
Poor Design
1
3
3
Minimize user interaction.
Make simple to operate.
Colin
9
11
12
Decreased
reliability
Fewer sales.
Unit will get
damaged more
often.
Poor part selection.
Poor fabrication.
Poor design.
Power
storage
capacity
System start-up
failure.
Cannot charge
devices without
a fire.
Poor system design.
Poor system storage 1 2 2
capacity.
1 3 3
Design the unit to be as robust as possible.
Choose high-lifetime components.
Lauren
Use high-capacity storage to meet
customer specs.
Andrew
Project Schedule
Project Schedule (Continued)