spacelab-ufsc/eps-re

RELIABILITY ENHANCED ELECTRICAL POWER SYSTEM

Electrical power system module designed and developed by SpaceLab.

Overview • Repository Organizarion • License • Releases • Notes

Overview

The Reliability Enhanced EPS has been designed to harvest, store and distribute energy for a future SpaceLab's mission. The energy harvesting system is based on solar energy conversion through 10 solar panels attached to the structure. This EPS is designed to operate the solar panels at their maximum power point. The harvested solar energy is stored in 4 lithium-ion batteries connected in series/parallel. The energy distribution is done by several integrated DC-DC converters. The EPS designed is almost all analog, and therefore more reliable when considering the impact of radiation on the system.

Repository Organization

- doc: Technical documentation (including mechanical structure, hardware, user guide, and datasheet).
- hardware: Sun simulator's hardware project (sources and outputs).

License

This project is open-source under three different licenses: CERN Open Hardware License v2.0 for hardware, and CC BY-SA 4.0 for the documentation.

Releases

Notes

eps-re's Issues

Hardware: Check the test points added

It would be important to know what you think about the added test points:

• Are the models used suitable? Should we change them?
• Are there any other buses that we need to have access?
• Is there more room for new test points?

Hardware: Update components location

According to datasheet: "Filter the VIN input to the LTC3833 with a simple RC filter close to the pin. The RC filter should be referenced to signal ground".

In our layout, R31/C10, R32/C11, R96/C99 and R95/C99 are far from pin number 10 (their respective Vin). It would be better to put closer. Below are disposed referenced images:

- Original typical application:

- In our schematics:

- In layout:

Hardware: Check the blocking diodes

Check that the blocking diodes added are suitable for testing at the moment. They won't necessarily be the final models, but it would be important to consider whether they would be sufficient for a 2U/3U CubeSat.

Hardware: Wrong connection of U28's pin

In file MPPT_Battery_Charger.kicad_sch, TERM_EN of U28 should be connected to VREF, too:

Hardware: No connection between the inductors and BQ24650RVAT's pin (PH)

The nets PH1 and PH2 must be connected to the inductors:

Hardware: Rotate PicoBlade connectors so that the input faces outward

Hardware: Wrong CD4051BPWR's pins connections

S0 should receive AMUX_SEL0, S1 should receive AMUX_SEL1 and S2 should receive AMUX_SEL2

Hardware: update some components' proximity

You should try to:

• Move Q5 closer to the IC.
• Move C92 and C93 down, closer to the IC, without moving them away from the MOSFETs.
• Move C81 to the right, closer to the IC.
• Move C84 to the left, closer to the IC.
• Move C98 and C90 to the left and down, closer to the IC, without moving them away from the R_sense.

Hardware: Update the position of some components

From LTC3833

• Place the ceramic Cvcc capacitor (C110/C111/C22/C23 in circuit) as close as possible to INTVCC and PGND pins.

• The CB capacitor (C20/C21/C108/C109 in circuit) should be as close as possible to BOOST and SW pins.

• Place small-signal components as close to their respective pins as possible. Give priority to VOSNS+/VOSNS–, SENSE+/SENSE–, ITH, RT and VRNG pins.

• Use sufficient isolation when routing a clock signal into MODE/PLLIN pin so that the clock does not couple into sensitive small-signal pins.

• Filter the Vin input to the LTC3833 with a simple RC filter close to the pin. The RC filter should be referenced to signal ground.

Hardware: Add the thermistor to the schematic

The BQ24650RVAT needs a thermistor to properly adjust the V_MP of the solar panel when the temperature varies. It is necessary to calculate its value and define its position in the PCB.

Hardware: Divide the GND into signal and power GND's

Talking together with Victor Noster, we defined the signal GND as the one represented with a "triangle", while the power GND is represented with the "dashes" in the figure below.

Hardware: Check the mounting holes position in the PCB

Check if the mounting holes are positioned correctly in the board.

Hardware: Add Kelvin connection for shunt resistor and update some components' proximity

From LTC3833 Datasheet:

• Place de sense resistor (R78/R79/R48/R47 in circuit) close to the inductor (L1/L2/L4/L8 - in circuit) on the output side.

• Use a Kelvin (4-wire) connection across the sense resistor (R78/R79/R48/R47 in circuit) and route the traces together as a differential pair. RC filter the differential sense signal close to SENSE+/SENSE– pins, placing the filter capacitor (C18-R43-R44/C19-R45-R46/C106-R64-R65/C107-R62-R61 in circuit) as close as possible to the pins.

• Place the resistive feedback divider RFB1/2 (R53-R54/R55-R56/R49-R50/R51-R52/R80-R140/R81-R142) as close as possible to VOSNS+/VOSNS– pins and route the remote output and ground traces together as a differential pair and terminate as close to the regulation point as possible. (preferably Kelvin connect across the capacitor at the remote output point).

Hardware: Change solar panel PicoBlade connector for PicoLock

Hardware: Adjust the proximity of output and input capacitors, inductors and shunt resistors

Considering the demonstration circuit 1640A (https://www.analog.com/en/products/ltc3833.html#product-overview), try to keep power train components inside a 4,825 cm² area: C_in, C_out, inductor and MOSFETs.

Hardware: Arrange the AMUX_OUT[0..15] signals in sequence in the look-up table

To do this, some nets should be renamed, which is the easiest way.

Hardware: Move the content of the folder "eps-re_project" to the root of the folder "hardware"

There is no need to store the KiCAD project files inside a folder with the name of the project. All project files can be moved directly to the "hardware" folder.

Hardware: Wrong configuration for signals BC_A_EN and BC_B_EN

In file MPPT_Battery_Charger.kicad_sch, the signal BC_A_EN should be high as default (pull-down configuration) and BC_B_EN low as default (pull-up configuration):

Hardware: Wrong nets' names

In file MPPT_Battery_Charger.kicad_sch, the nets VBC_N and VBC_IN should be the same:

Workflow: Check KiBot related files

It seems that using multiple schematic files is becoming a problem for KiBot. It can't find all the schematic files and therefore doesn't execute the workflow correctly.