Kumu a`o Cubesat

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First found May 22, 2018

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KUMU A’O CUBESAT
Amy Blas
Background
2
What is CubeSat?
10x10x10 centimeter cube
 Launched in lower earth orbit (LEO)




The project started last semester.
13 members
Objective is to be the first CubeSat in space from
Hawaii
Proposed Mission
4

To be Hawaii’s first developed, tested, launched,
and operated CubeSat successfully placed into
orbit
CubeSatellite System
•Brain
•Digestive
•Ears and Mouth
•Bones
•Skin and Blood
•Eyes and appendages
•Command and Data Handling
•Electrical Power
•Telecommunications
•Structure
•Thermal
•Attitude Control and Determination
5
Recap of CDR



Was working on PCB
Realized that Proto-typing is more important
Started Prototyping
What have we been working on now?

We have been prototyping all of our chips
 Finding
values of circuit parts
 Putting the circuit together
 Getting Results
Block Diagram of EPS
8
Solar Cells
Step Up
Converter
Battery Charger
Battery Gauge
and Sensors
Battery Pack
C&DH
DC-DC
Converter and
Switching
Mechanisms
Electronic
Components
Block Diagram of EPS
9
Solar Cells
Step Up
Converter
Battery Charger
Battery Gauge
and Sensors
Battery Pack
C&DH
DC-DC
Converter and
Switching
Mechanisms
Electronic
Components
Solar Cells
10
Spectro Lab’s Improved Triple Junction (ITJ)
26.8% efficiency Solar Cells

High efficiency n/p design (28°C, AM0)
-BOL: 26.8% min. average efficiency @
maximum power
(26.5% @ load voltage)
-EOL: 22.5% min. average efficiency @
maximum power
(22.3% @ load voltage),

Integral bypass diode protection

Transparent insertion into existing systems
Solar Cells
11
Current Sensor
•1 Set = 2 Series Cells
•Six Sets in parallel
•12 cell configuration
10 cm
10 cm
10 cm
•Each cell is 4 x 7 cm
•2.32 V per cell
•Jload min avg= 16.10 mA/cm²
•4.64 V and 450.8 mA per cell
(After adjustments)
Blocking
Diode (prevent
power drain)
Bypass Diode
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
12
Solar cell design

Used 3 MAX 1771 Chips
 Simulate
solar cell input
 6 V output

Component Value
 R1
= 10 K Ω
 R2 = 30 kΩ
3.3 V DC Input
6 V output
Schottky
Diodes
6 V DC Output
Data Values
Input
Theoretical Chip1
Chip 2
Chip 3
Placement
Notes
3V
6V
6.254 V
6.306 V
2.844 V
B4 diode
1
3V
6V
6.741 V
6.504 V
3.271 V
Aft Diode
2
3.30 V
6V
6.254 V
6.316 V
3.013 V
B4 Diode
3
3.30 V
6V
6.67 V
6.467 V
2.994 V
Aft Diode
3.00 V
6V
7.00 V
3.30V
6V
7.13 V
Note 1 : All values of our resistor parts were the same
Note 2 : Realized something was wrong in Chip 1 and 3; no diode voltage diode.
Note 3: Debugging and changed out capacitors.
Problems – MAX 1771

Part Values
 Mosfet
 Rsense

Same value, Different Brand
 Capacitors
 Inductors

Exact circuit – incorrect values
Block Diagram of EPS
17
Solar Cells
Step Up
Converter
Battery Charger
Battery Gauge
and Sensors
Battery Pack
C&DH
DC-DC
Converter and
Switching
Mechanisms
Electronic
Components
Battery Charger – MAX1898

Simple circuit design

4.5 to 12V input range




Programmable charge
current
Output voltage of 4.1V
Internal current sense
resistor
Programmable safety timer
Proto-typing

Using equation
and looking at the
battery specifications for 1.4Amps charging rate
 Rset

= 1K
Used a different battery to test
 Old
PDA Lithium Ion Battery
Input
Theorized
Voltage
Theorized Output
Current
Voltage
Shunted
Voltage
6.4Ω
Output
Current
5V
4.1 V
1.4A
4.12 V
3.714 V
624mA
6.5 V
4.1 V
1.4 A
4.123 V
3.717 V
650 mA
What we learned

Battery Reset
 Need
to hook up pin to micro controller
 Hard reset

The charger works!!!!
Block Diagram of EPS
Solar Cells
Step Up
Converter
Battery Charger
Battery Gauge
and Sensors
Battery Pack
C&DH
DC-DC
Converter and
Switching
Mechanisms
Electronic
Components
DC-DC converters
22
Input from
Battery
Step down
3.3V
Step up
+6 V
Load
Load
Step up
+5V
Load
DC-DC converters
23
Input from
Battery
Step down
3.3V
Step up
+6 V
Load
Load
Step up
+5V
Load
DC-DC step-down converter
24

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
Problems and Solutions

Data sheet mix ups
 Schematic
and given values
 Equations

Components
 Electrolytic,
ceramic, or tantalum
 Resistor Values

Guess and check
 R1=
360K
Data
Input
Resistor
Values
Output
5.0 V
200 K
2.6 V
300 K
3.04 V
400 K
3.480 V
360 K
3.337 V
Input
Theoretical
Output
Shunt 6.4Ω
Output Current
4.0 V
3.3 V
3.28 V
3.001 V
469mA
3.338 V
2.83 V
442mA
3.337 V
3.269 V (10Ω)
327mA
4.70 V
5.0 V
DC-DC converters
27
Input from
Battery
Step down
3.3V
Step up
+6 V
Load
Load
Step up
+5V
Load
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
o Set by input voltage of charger
External resistors can be used to set
the output voltage
Operating Temperatures
= - 40oC to +85oC
28
DC-DC converters
29
Input from
Battery
Step down
3.3V
Step up
+6 V
Load
Load
Step up
+5V
Load
DC-DC Step-up converters

MAX1703(step-up)
 Fixed 5V output voltage
 Up to 95% efficiency
 0.7 to 5.5V input Range
 Up to 1.5A output
 Operating temperature range
of -40 to +85°C
Problems

Incorrect parts
 Similar

but not exact
Soldering
Detailed Schematic
32
Actual Circuit
Overall

Problems
 Components
 Soldering

Solutions
 Order
exact parts
 PCB for certain chips
QUESTIONS????!!!!!
×

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