BUTCube

Modules:

• Solar panels (XY, Z) (not in stack)
• EPS
• Flight Computer
• Mission computer
• Communication
• Sun sensor module (not in stack)
• ? Attitude control
• Access port module (not in stack)

Solar panels

Solar cells

SM141K04L

• Link: https://www.digikey.nl/short/fvpwbf4h
• Panel count: 8 (2S 4P)
• Maximal power: 0.98 W
• Voltage: 4.46 V (MPPT)
• Dimensions: 29 x 23 mm
• Weight: 3g (24g)
• Price (for 1 side): 28 € (750 CZK)

SM141K04LV

• Link: https://www.digikey.cz/short/r589mmbj
• Panel count: 8 (2S 4P)
• Maximal power: 0.98 W
• Voltage: 4.46 V (MPPT)
• Dimensions: 45 x 15 mm
• Weight: 2.5g (20g)
• Price (for 1 side): 28 € (750 CZK)

Solar module

• Two sizes of solar panel PCBs
  • Z - 100x100 mm with cutouts in corners for rails
  • X,Y - 100x83
• In center of module is hole for another module
  • Approximate size of module is 46x30 mm
  • Mounting to frame is via 4 bolts in corners of board
• Integrated components: Optodiode, temperature measuring IC

Sensors

• Temperature sensor: AT30TS74
• Photo diode:
  • VEMD5510C - 550nm (450-750) - visible
  • VEMD5060X - 800nm (500-1000) - visible + IR
  • VEMD5160X - 850nm (750-950) - IR (used)
• ADC for photodiode: ADS7142

Cables

• https://www.digikey.cz/product-detail/en/adafruit-industries-llc/3165/1528-1733-ND/6193585

• https://www.digikey.cz/product-detail/en/adafruit-industries-llc/3167/1528-1735-ND/6193587

• https://www.digikey.cz/product-detail/en/adafruit-industries-llc/3168/1528-1736-ND/6193588

• https://www.digikey.cz/product-detail/en/adafruit-industries-llc/3164/1528-1732-ND/6193584

• 30AWG resistance 0.3R per meter

• Length in CubeSat cca 10-15 cm

• Power loss in cables is 0.5mW in peek (0.05% per solar module)

• Similar power loss will be at cable connectors

Stack connector

• [https://cz.mouser.com/ProductDetail/200-SSQ12002TD]
• 2x20 pins
• Limits board to thickness of 1mm or less
• Board spacing: 8.51 mm

EPS

• Two identical modules on one board
• Both connected to stack connector
• Other board could be connected to both or one of then
  • Power oring must be solved
• Connected to main CAN

Power output

• 3 regulated and monitored power rails - 1V8, 3V3, 5V
  • Output regulator - TPS63002DRCR
  • 0.8A (boost) up to 1.2A (buck) output
  • 2.2 uH coil
• 1 unregulated output of battery, monitored
• Monitoring via current sensors (INA??)

Battery

• Limit for CubeSat is 50Wh
• Suggested battery has form factor 21700
• One battery per EPS
• Battery is mounted in battery holder
  • Keystone 1122 - 1122
  • Probably additional fixation is requested
• Selected battery - https://www.conrad.cz/p/samsung-inr21700-50e-specialni-akumulator-21700-flat-top-li-ion-akumulator-36-v-4900-mah-2114678
  • 3.6V, 4900mAh, 17.64Wh
  • EPS module has around 35Wh (well in limit)

Battery heating

• https://www.ges.cz/cz/odl-20r81-GES06914579.html

• https://www.ges.cz/cz/odl-53r1-GES06914581.html

• https://www.gme.cz/odporovy-drat-odp-kan02-3m

• https://www.gme.cz/odporovy-drat-odp-kon03-3m

• Heating should be designed for power around 1-4W

• With 5.4R/m and battery input source (3.7V) length of wire for 2W heating should be around 1.2m (current 0.5A)

  • 0.5A is probably to much, values around 0.2A are better -> 1W heating

• For regulation could be used power switch with constant current regulation

Access port module

Connectors:

• USB-C

  • data connected to mission computer or flight computer
  • power connected to EPS for battery charging

• 2x SWD port for programing and debugging of Flight and Mission computer

• main CAN bus connector

• UART debug port

• Realized as stack of two PCB boards

  • Front acts only as cover for connectors
  • Connectors are mounted on rear board
  • Connectors are accessible via cutouts in frontz board
  • Rear board is mounted to front via column spacers

Other parts:

• LTC4415 - Dual ideal diode with ORing
• MAX16171 - Ideal Diode Controller with Reverse-Current Protection
• BQ25798 - solar battery charger with dual-input selector and MPPT, I2C, https://www.ti.com/product/BQ25798
• BAT54W-G - Low drop shottky diode, solar blocking diode
• BQ27421YZFT-G1A - Fuel gauge

Digikey orders

https://www.digikey.cz/short/8nmn4tr3 https://www.digikey.cz/short/d4n94tbz