The design of the EPS has been created to be easily understandable, to serve as a basis for future developments that can meet the expectations of the new conquerors of outer space. On this PCB you will find the elements commonly used in this type of system accessible for OBC program using the Arduino IDE.

This EPS unit supports the input of two solar panel arrays with a voltage between 4.5V and 6V. It allows charging by DC input of the Lithium Polymer Battery located at the bottom of the PCB.

The charging process is monitored by the CN3063 integrated circuit in charge of delivering a DC voltage of 4.2V to the battery. The battery's charge, as well as its energy supply or acquisition to/from the rest of the system, is constantly sensed by the INA226 circuit that sends data to the OBC over the I2C bus.

Finally, a DC-DC converter FP6291 circuit transforms the 3.7V voltage from the lithium polymer battery to 5V, which is fed to the BUS for use by the other subsystems.

Attached to the back of the PCB is the 500mA, 3.7V LiPo battery. Its location allows taking advantage of the temperature generated by the OBC microcontroller, and can be measured by the temperature sensor located on this PCB.

The NessieSAT EPS includes control signals, inputs and outputs that allow it to control external devices and new PCBs. In this BUS called PQ20N you can find the following lines.

• UART RX (high speed serial data input connection)

• UART TX (high speed output data input connection)

• D5 Programmable digital input / output

• D7 Programmable Digital Input / Output (for use in EPS in Alert Power Detection)

• D6 Programmable digital input / output

• +3V3 Rail voltage from EPS

• AD3 Analogue input 12 bit resolution

• AD2 Analogue input 12 bit resolution

• AD1 Analogue input 12 bit resolution

• AD0 Analogue input 12 bit resolution

• DONE Interrupt input for indicating full battery charge

• IMU Interrupt input for IMU

• MISO High speed SPI BUS input

• CHG Input to indicate that the batteries are receiving power from the solar panels

• MOSI High speed SPI BUS output

• SCK SPI bus clock signal

• SDA I2C bus data signal

• SCL I2C bus clock signal

• GND Ground plane

• +5V Rail voltage