μ3D: RatRig V-Core 3 EVA 2 wiring over RJ45

A daughter board that mounts on a 3D printer hotend assembly to enable all wiring over RJ45

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Rather than wiring all devices directly from the 3D printer electronics panel to the hotend assembly, this board allows you to connect two simple RJ45 wires between the boards, and then wire the devices directly using the JST-XH connectors. One board mounts to the hotend, the other mounts on the electronics panel.

It then makes it simple to swap out a hotend without rewiring everything. It significantly cleans up the wiring and reduces maintenance and upgrading headache.

Note: this board was originally designed to lay flat with 40x40mm dimensions, but a similar project by "Minty Trebor" on The RatRig Discord chat inspired me to alter the design.

This board is designed specifically as an addon for the EVA 2 3D project which enables modular 3D printer hotend assemblies using standard adapters and 3D printed parts.

The board is not designed to route wiring for the hotend heater cartridge or the hotend thermistor. It is only for low current electronics such as fans, accelerometer, e-step motor, etc.

Board design notes

  • PCB traces are 0.500mm and should handle 1A of current each
  • PIN 1 on every connector except the e-motor is the GND pin
  • JST-XH connectors are recommended, but other connectors/pin headers may be used
  • RJ45 connectors are shielded but don't contain LEDs, so the board draws 0mA current.
  • The board is mounted using 2 screws and sits between the universal_cable_mount  and cable_holder -- it doesn't require 3D printing additional parts.

This project is certified open hardware:

  • Available for purchase on Tindie!

    Alexander Williams08/15/2021 at 14:20 0 comments

    I put the modules up for sale on Tindie!

    Get it here!

    I've also published the design files, pinout, and other info on GitHub.

  • Soldered components and 3D printed parts

    Alexander Williams08/09/2021 at 06:35 0 comments

    This weekend I soldered the RJ45 and JST-XH connectors. I did some electrical tests and so far everything seems to work perfectly.

    I also printed the "cable holder" and "universal cable mount" from the EVA 2 GitHub repo (printed really quickly with super low quality on my poor CR-10). Everything fits perfectly.

    The module can also be mounted "upside-down" for those who prefer.

  • Received the PCBs today!

    Alexander Williams08/07/2021 at 07:34 0 comments

    The PCBs arrived quicker than expected: less than 2 weeks.

    I ordered a whole bunch and I'm happy to send them to whoever wants to help with initial testing and validation.

    I will solder two boards with RJ45 and JST-XH connectors this weekend, and run a few tests on my own.

    If all is good then I'll create a special product listing on Tindie for those who want to try out some boards free of charge (you pay shipping).

  • Mount ADXL to PCB: v.3

    Alexander Williams07/31/2021 at 03:58 0 comments

    In v.2 I added M3 mounting holes to screw the ADXL directly to the PCB.

    In v.3 I replaced those mounting holes with 8-pin 2.54mm header holes at the top of the PCB.

    This would make it possible to either:

    1. solder the ADXL with 8-pin headers directly to the PCB, or
    2. solder an 8-pin socket and then simply slide the ADXL (with pin headers) into the socket

    The pin assignments on the 8-pin headers is identical to the ADXL board, and would use the twisted pairs 1-2 for GND/SCL, 3-6 for SDA/VCC, 4-5 for SDO/CS. The INT1 and INT2 would remain unconnected in this case.

    Personally I don't really like v.3 because it's not flexible and forces you to use specific twisted pairs for the pins. In v.1 and v.2, you can choose which pairs to use and easily add your own decoupling capacitors if needed.

    I guess I can leave it to the community for suggestions on which board is better.

  • Added mounting holes for ADXL: v.2

    Alexander Williams07/30/2021 at 09:50 0 comments

    I really wish I thought of this before ordering the first batch of PCBs. Well this is going to be part of the v.2 boards: Mounting holes for an ADXL.

    Probably not everyone wants to mount a PCB on another PCB, but at least this would avoid the need to 3D print an ADXL adapter, since you can just use some M3 screws to attach the ADXL at the top of the PCB (the holes flanking the logo). It can be mounted on either side of the PCB and cleanly wire to the JST-XH connector.

    This design is by far not final, as I'm also considering just adding 8 pins to solder the ADXL directly to the PCB.. we'll see.

  • Ordered PCBs for v.1

    Alexander Williams07/25/2021 at 16:01 0 comments

    I'm not sure if this will be the final design, but I ordered a set of PCBs for prototyping and testing.

    I'll update the project in ~2 weeks once I receive them.

    Note: I plan on selling the first few batches of these boards on Tindie (populated/unpopulated) as well, before publishing the design files on GitHub.

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