bac-hardware/eps/main-board/minimal

EPS Main Board – Minimal

Subsystem: EPS
Status: ✅ Released

Latest Release:

• Version: v1r1
• Date: 2025-04-03
• KiCad: v9

Overview

The EPS main board is the central component of the Build a CubeSat electrical power system. This minimal version offers some telemetry but is much easier to assemble than the fully instrumented variant, which is currently deprecated and in need of redesign.

After adding two solar charging modules and two DC-DC converter modules, it serves as the hub for regulated power distribution to all connected subsystems—integrating charging control, bus protection, and routing of solar and battery power. The PCB sits atop the EPS bay and connects to the battery pack through a set of contact-dome PCBs, supporting modular configurations. Currently, only 2s2p is supported, but 4s and 4p configurations are feasible.

Redundant connections are available to the side panels and magnetorquers via 16-pin receptacle arrays. bacBus interconnect boards link the system, with the Zm side requiring a 32 mm interconnect to reach through the EPS bay.

Since RBF and deployment switch features are not yet present in the current prototype, this board exposes the related lines via pins for manual pull-up/down during development.

Specifications

• Dimensions: 91.5 mm × 91.5 mm
• Layer Count: 4
• Panelization: No
• Mounting: Top of EPS bay with standoffs
• Stacking: bacBus connection on Zm and Zp sides using pinout v3r3

Connectors & Interfaces

• Power Input: Solar charging panels on four sides, battery pack via contact domes
• Communication: I2C telemetry lines via bacBus
• Special Functions:
  • RBF and deployment switch signal pins
  • Power routing, switching, protection

Test Points & Indicators

• Battery voltage test point
• Jumpers for debugging (no LEDs or DIP switches)

Files

• Design files: Located in the kicad9/ folder
• Schematics: PDF
• 3D Render:
  

Manufacturing

• Release: eps-main-board-minimal-v1r1
• BOM: Included
• Instruction:
  • Ordering: Included (PCBWay)
  • Sourcing: Not Included
  • Assembly: Not Included

Notes

Designed for development and suborbital test environments. Not flight-qualified. Fully instrumented variant is deprecated.

License

CC BY-SA 4.0

Contributing

Contributions to the Build a CubeSat hardware ecosystem are highly appreciated! To keep things structured, here’s how you can contribute:

Fixes & Improvements to Existing Designs

1. Create a new feature branch (git checkout -b feature/your-feature-name)
2. Commit your changes (git commit -m 'Brief description of change')
3. Push to the branch (git push origin feature/your-feature-name)
4. Submit a Pull Request (PR) with a clear description of the changes

New Designs & Community Contributions

• Create your own repository
• Share a link in community discussions or open an issue
• If relevant, it will be referenced in the docs 🙌

Supporting This Project

If you’d like to support the Build a CubeSat project further, consider these options:

• Patreon
• KoFi
• PayPal