This note is to write about how I am modifying the Calibration Cubesat for the Education Cubesat. The main features in the Edusat are:
- Charging circuit for 18650
- Direct transfer mode
The sources of the Edusat EPS is found here: Git repository Edusat Branch
Guides
20240320 - EPS - Workshop 1 - Overview of the system
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Solar panels
I have to change the solar panels. On the Calibration Cubesat we will use high effiency solar cells. But on this cubesat, a standar solar panel is great.
The perfect size is 100mm x 80mm. This solar panel from digikey is perfect. But there are cheaper on aliexpress, like this one.
The Edusat will have two solar panels of 5V.
Charging circuit
We will use other type of bateries. Due to lack of space I would use Lipo batteries.
The circuit must allow to charge the batteries with solar cells and with usb cable. When is connected to usb cable, the circuit must power on.
The component MCP73831 fit perfect for this task, or even the LTC4066. But if I use LiPo battery I need this circuit.
So the main modification from the original schematic is to put the batteries and the charging circuit after the buck converter of 5V.
The best way to protect the batteries while charging them is to but a charging circuit for each of them.
This post is interesting for doing the connection between the batteries
This document from digikey explains a lot of circuits for power charing.
Buck converters
The 3.3V Voltage regulator could be the LTC3130, or LT8610.
The 5.0V Voltage regulator could ve the Mp3414A.
Then I need a step up to 12V for the motors. The LT1301 could work, or the LMR62014.
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In order to addapt the schematics these are the tasks:
- Put a charging circuit
- Checkout the inductor in the 3.3 buck converter
- Put sensors for the charging circuit
- Put only one PC104
- Put the correct buck converters
- Put a switch for power on-off the system.
- Update power switching
- Put the DET activation circuit.
- Led indicator status
- Reset button
- Measure Vbat
- VIN_LEFT y VIN_RIGHT no están bien puestas
- Button for powering on?