notes: add README with solar cell comparison

README.md

@@ -1 +1,64 @@
 # BUTCube
+
+# Solar cells
+
+Digi-key filter: https://www.digikey.nl/products/en?FV=-5|23585
+
+Calculations for space are calculated with 1 mm space between panels
+In center of panel there should be attitude determination module with minimal size od 25mm x 25mm
+All calculation are only for one side of satelite
+
+#### SM141K04L
+- Link: https://www.digikey.nl/short/fvpwbf4h
+- Panel count: 10 (2S 5P)
+- Maximal power: 1.23 W
+- Voltage: 4.46 V
+- Dimensions: 29 x 23 mm (89 x 95 mm)
+- Weight: 3g (30g)
+- Configuration: 4 x 3 
+- Price (for 1 side): 28 € (750 CZK)
+
+#### KXOB25-05X3F
+- Link: https://www.digikey.nl/short/hdrrmtq3
+- Panel count: 32 (4S 8P)
+- Maximal power: 0.98 W
+- Voltage: 6.68 V
+- Dimensions: 23 x 8 mm (95 x 89 mm)
+- Weight: 0.5g (17g)
+- Configuration: 10 x 4
+- Price (for 1 side): 47 € (1229 CZK)
+- + Reflow solderable
+
+#### SM141K06LV
+- Link: https://www.digikey.nl/short/d80rrj7t
+- Panel count: 6 (2S 3P)
+- Maximal power: 1.10 W
+- Voltage: 6.7 V
+- Dimensions: 45 x 22 mm (91 x 91 mm)
+- Weight: 3g (18g)
+- Configuration: 2V 2H 2V
+- Price (for 1 side): 27 € (720 CZK)
+
+#### SM141K04LV
+- Link: https://www.digikey.cz/short/r589mmbj
+- Panel count: 8 (2S 4P)
+- Maximal power: 0.98 W
+- Voltage: 5.52 V
+- Dimensions: 45 x 15 mm (81 x 95 mm)
+- Weight: 2.5g (20g)
+- Configuration: 2V 4H 2V
+- Price (for 1 side): 28 € (750 CZK)
+
+
+## Solar module 
+- PCB with size cca 96x96 mm
+- In center of module is hole for another module (40x40 mm without corners)
+- Integrated components: Optodiode, temperature measuring IC
+
+# Other parts:
+- LTC4415 - Dual ideal diode with ORing
+- 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
+
+- jaká kamera?
+- proč gyroskopy?