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 5 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

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 C&DH Battery Gauge and Sensors Battery Pack DC-DC Converter and Switching Mechanisms Electronic Components

Block Diagram of EPS 9 Solar Cells Step Up Converter Battery Charger C&DH Battery Gauge and Sensors Battery Pack DC-DC Converter and Switching Mechanisms Electronic Components

Solar Cells 10  High efficiency n/p design (28°C, AM0) -BOL: 26.8% min. average maximum power load voltage) -EOL: 22.5% min. average maximum power load voltage),  Integral bypass diode protection  Transparent insertion into existing systems Spectro Lab’s Improved Triple Junction (ITJ) 26.8% efficiency Solar Cells

11 Solar Cells 1 Set = 2 Series Cells Six Sets in parallel 12 cell configuration Each cell is 4 x 7 cm 2.32 V per cell J load min avg = mA/cm² 4.64 V and mA per cell (After adjustments) Bypass Diode Blocking Diode (prevent power drain) 10 cm Current Sensor 10 cm

Step-up Converter – MAX 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

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 InputTheoreticalChip1Chip 2Chip 3PlacementNotes 3 V6 V6.254 V6.306 V2.844 VB4 diode1 3 V6 V6.741 V6.504 V3.271 VAft Diode V6 V6.254 V6.316 V3.013 VB4 Diode V6 V6.67 V6.467 V2.994 VAft Diode 3.00 V6 V7.00 V 3.30V6 V7.13 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 C&DH Battery Gauge and Sensors Battery Pack 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 InputTheorized Voltage Theorized Current Output Voltage Shunted Voltage 6.4 Ω Output Current 5 V4.1 V1.4A4.12 V3.714 V624mA 6.5 V4.1 V1.4 A4.123 V3.717 V650 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 C&DH Battery Gauge and Sensors Battery Pack DC-DC Converter and Switching Mechanisms Electronic Components

DC-DC converters 22 Input from Battery Step down 3.3V Step up +6 V Step up +5V Load

DC-DC converters 23 Input from Battery Step down 3.3V Step up +6 V 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 InputTheoreticalOutput Shunt 6.4 Ω Output Current 4.0 V 3.3 V 3.28 V3.001 V469mA 4.70 V3.338 V2.83 V442mA 5.0 V3.337 V V (10 Ω) 327mA InputResistor Values Output 5.0 V 200 K2.6 V 300 K3.04 V 400 K3.480 V 360 K3.337 V

DC-DC converters 27 Input from Battery Step down 3.3V Step up +6 V Step up +5V Load

Step-up Converter – MAX 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 = - 40 o C to +85 o C

DC-DC converters 29 Input from Battery Step down 3.3V Step up +6 V 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????!!!!!