Transcript Kumu a`o Cubesat

KUMU A’O CUBESAT
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Amy Blas
March 7, 2008
WHAT IS CUBESAT?
 10x10x10
centimeter cube
 Launched in lower earth orbit (LEO)
 Started last semester
 13 members
 Objective is to be the first CubeSat
in space from Hawaii
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THE DIFFERENT SUBSYSTEMS
 Tele-Communication
 Command
and Data Handling
(C&DH)
 Thermal
 Structural
 Electrical Power (EPS)
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BLOCK DIAGRAM OF EPS
Solar Cells
Step Up
Converter
Battery
Charger
DC-DC
Converter
Battery
Gauge
Electronic
Components
Battery Pack
C&DH
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BLOCK DIAGRAM OF EPS
Solar Cells
Step Up
Converter
Battery
Charger
DC-DC
Converter
Battery
Gauge
Electronic
Components
Battery Pack
C&DH
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SOLAR CELLS
Spectro Lab’s Improved Triple Junction (ITJ)
 26.8%
efficiency Solar
Cells
 Integral bypass diode
protection
 Transparent insertion
into existing systems
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SOLAR CELLS
1 Set = 2 Series
Cells
 12 cell configuration

Current
Sensor
10 cm
10 cm
10 cm

Each cell is 4 x 7 cm
 2.32 V per cell
 4.64 V and 450.8
mA per side
Blocking
Diode
(prevent power
drain)
Bypass
Diode
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CURRENT SENSORS
Texas Instruments INA138-Q1: High-Side Measurement Current
Shunt Monitor
1 placed at each
side
 Used to see
orientation of
Cube

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BLOCK DIAGRAM OF EPS
Solar Cells
Step Up
Converter
Battery
Charger
DC-DC
Converter
Battery
Gauge
Electronic
Components
Battery Pack
C&DH
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STEP-UP CONVERTER – MAX1771
2 to 16.5V Input Voltage
Range
 90% Efficient for low load
currents
 Output current range of
30mA to 2A
 Preset 12 V or adjustable
output voltage
 Set by input voltage of
charger
 5V

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BLOCK DIAGRAM OF EPS
Solar Cells
Step Up
Converter
Battery
Charger
DC-DC
Converter
Battery
Gauge
Electronic
Components
Battery Pack
C&DH
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BATTERY CHARGER – MAX1898





Simple circuit design
4.5 to 12V input
range
Programmable
charge current
Output voltage of
4.1V
Internal current
sense resistor
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BLOCK DIAGRAM OF EPS
Solar Cells
Step Up
Converter
Battery
Charger
DC-DC
Converter
Battery
Gauge
Electronic
Components
Battery Pack
C&DH
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LITHIUM ION CELLS
Saft MP 176065 Lithium Ion cell
Nominal Voltage: 3.7 V
 Cycle Life: > 600 cycles @ C/2 to
100% DoD
 Capacity of 7 Ah
 Discharge cut off voltage : 2.5 V
 End charge voltage of 4.2+/-0.05V

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BLOCK DIAGRAM OF EPS
Solar Cells
Step Up
Converter
Battery
Charger
DC-DC
Converter
Battery
Gauge
Electronic
Components
Battery Pack
C&DH
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FUEL GAUGE
Texas Instruments bq2060A: Compliant Gas Gauge IC


External EEPROM stores configuration
information
 Battery’s chemistry
 Self-discharge rate
 Rate compensation factors
 Measurement calibration
 Design voltage and capacity
Accurately adjusts remaining capacity for use and
standby conditions based on
 Time
 Rate
 Temperature
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BLOCK DIAGRAM OF EPS
Solar Cells
Step Up
Converter
Battery
Charger
DC-DC
Converter
Battery
Gauge
Electronic
Components
Battery Pack
C&DH
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DC-DC CONVERTER

MAX1703(step-up)
 Fixed 5V output voltage
 Up to 95% efficiency
 0.7 to 5.5V input Range
 Up to 1.5A output
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MAX1703- PCB ARTIST SCHEMATIC
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DC-DC CONVERTER
o MAX 1771 : 6V step-up
o 2 to 16.5V Input Voltage Range
o 90% Efficient for low load
currents
o Output current range of 30mA to
2A
o Preset 12 V or adjustable output
voltage
o Set by input voltage of
charger
o External resistors can be used to
set the output voltage
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MAX1771- PCB ARTIST SCHEMATIC
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DC-DC CONVERTER

MAX1921(step-down)
 Up to 90% efficiency
 2 to 5.5V input range
 Fixed 3.3V output voltage
 Guaranteed 400 mA
output current
 Up to 1.2MHz switching
frequency
 Operating temperature
range of -40 to +85°C
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MAX1921- PCB ARTIST SCHEMATIC
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EPS PCB ARTIST SCHEMATIC
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EPS PCB ARTIST- PCB DESIGN
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PROBLEMS

Complications with PCB artist
Not enough room on PCB
 Wrong values for resistors, capacitors, etc.
 Connection errors


Running out of Time
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EPS Schedule
(Gantt Chart)
Week
1
2
3
January
14 21 28
Date
Presentations
Design
Orientation
Proposal
Preliminary Design
Critical Design
Final
EPS
PCB artist
Ina 138
Max 1771
Max 1898
Max 1771
Max 1703
BQ 2060A
Prototyping
Breadboard
Ina 138
Max 1771
Max 1898
Max 1703
Max 1771
BQ2060A
Test
Receive Parts
Test PCB layout
Combine
subsystems
Reports
Draft
Final
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4
5
6
February
11 18
7
8
25
3
9
10 11
March
10 17 24
12
13
31
7
14 15
April
14 21
16
17
May
28 5
Any Questions?
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