K UMU A ’ O C UBESAT Amy Blas March 7,

W HAT IS C UBE S AT ? 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 2

3

T HE D IFFERENT S UBSYSTEMS Tele-Communication Command and Data Handling (C&DH) Thermal Structural Electrical Power (EPS) 4

B LOCK D IAGRAM OF EPS 5 Solar Cells Step Up Converter Battery Charger C&DH Battery Gauge Battery Pack DC-DC Converter Electronic Components

B LOCK D IAGRAM OF EPS 6 Solar Cells Step Up Converter Battery Charger C&DH Battery Gauge Battery Pack DC-DC Converter Electronic Components

S OLAR C ELLS 26.8% efficiency Solar Cells Integral bypass diode protection Transparent insertion into existing systems 7 Spectro Lab’s Improved Triple Junction (ITJ)

8 S OLAR C ELLS 1 Set = 2 Series Cells 12 cell configuration Each cell is 4 x 7 cm 2.32 V per cell 4.64 V and mA per side Bypass Diode Blocking Diode (prevent power drain) 10 cm Current Sensor 10 cm 8

C URRENT S ENSORS 1 placed at each side Used to see orientation of Cube Texas Instruments INA138-Q1: High-Side Measurement Current Shunt Monitor 9

B LOCK D IAGRAM OF EPS 10 Solar Cells Step Up Converter Battery Charger C&DH Battery Gauge Battery Pack DC-DC Converter Electronic Components

S TEP - UP C ONVERTER – 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 5V

B LOCK D IAGRAM OF EPS 12 Solar Cells Step Up Converter Battery Charger C&DH Battery Gauge Battery Pack DC-DC Converter Electronic Components

B ATTERY C HARGER – MAX1898 Simple circuit design 4.5 to 12V input range Programmable charge current Output voltage of 4.1V Internal current sense resistor 13

B LOCK D IAGRAM OF EPS 14 Solar Cells Step Up Converter Battery Charger C&DH Battery Gauge Battery Pack DC-DC Converter Electronic Components

L ITHIUM I ON C ELLS Nominal Voltage: 3.7 V Cycle Life: > 600 C/2 to 100% DoD Capacity of 7 Ah Discharge cut off voltage : 2.5 V End charge voltage of 4.2+/-0.05V Saft MP Lithium Ion cell 15

B LOCK D IAGRAM OF EPS 16 Solar Cells Step Up Converter Battery Charger C&DH Battery Gauge Battery Pack DC-DC Converter Electronic Components

F UEL G AUGE 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 Texas Instruments bq2060A: Compliant Gas Gauge IC 17

B LOCK D IAGRAM OF EPS 18 Solar Cells Step Up Converter Battery Charger C&DH Battery Gauge Battery Pack DC-DC Converter Electronic Components

DC-DC C ONVERTER MAX1703(step-up) Fixed 5V output voltage Up to 95% efficiency 0.7 to 5.5V input Range Up to 1.5A output 19

MAX1703- PCB ARTIST SCHEMATIC 20

DC-DC C ONVERTER 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 21

MAX1771- PCB ARTIST SCHEMATIC 22

DC-DC C ONVERTER 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 23

MAX1921- PCB ARTIST SCHEMATIC 24

EPS PCB A RTIST S CHEMATIC 25

EPS PCB A RTIST - PCB D ESIGN 26

P ROBLEMS Complications with PCB artist Not enough room on PCB Wrong values for resistors, capacitors, etc. Connection errors Running out of Time 27

EPS Schedule (Gantt Chart) Week JanuaryFebruaryMarchAprilMay Date Presentations Orientation Proposal Preliminary Design Critical Design Final DesignEPS 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

Any Questions? 29