Cable and Connector specs for CanBus PCB's

[majic79]

I'm really interested in going down the CanBus route for my Voron's, but I worry that there's a really key piece of information missing. Electrical and Electronic design is one of my hobbies and semi-professional life (I'm usually more on the IT side of cabinet building, but I work with my colleagues to produce electrical specifications). We typically work with 4-20mA devices (fieldbus wiring) and termination is usually ferruled end into spring terminals. All the boards specify the electrical side (Can_L, Can_H, PWR, GND) but don't have any indication of load (current or power), nor do they specify the terminal (some look like Molex MicroFit 3.0mm pitch, but there seems to be at least two other terminal types being used now).

Where can I find the power specs for the designs (e.g. max 5A load) so I can get the right size cables? where do I even find the spec for the connector? I've got my RS and Digikey accounts, but there's no way I can identify the right spec from vague pictures. It would really help if those products (I'm looking at you EBB 36) came with the right connectors, or at least told us what connector they used, so I could order them in.

Is the EBB 36/Klipper U2C open source? or is it a closed design somehow? Googling around and I don't find much more than a few manuals and some instructions about what needs connecting to what - doesn't tell me what's in the box, or what connectors I need in order to use the damn things, or the kind of cabling to order to meet the power needs and have a safe umbilical that isn't going to melt/catch fire on me

 

[Spice_King]

They come with the connectors and pins for the board. MicroFit 3.0 for CAN on the EBB boards, the EBB SB boards use XT-30+2 for CAN instead and include a cable for themselves. Other connections use JST variants.

The U2C has a MicroFit and I think it's a MiniFit in a 2x2 setup, comes with connectors/pins for both of those. Others are JST connections, but I don't recall if it came with, I have a kit so I probably mentally blanked out of it came or not.

Cables wise, IGUS's Chainflex Control Cable is often used (does 20awg all around), but 3DO has been making their own CAN Bus cable and uses 20awg for power and 26awg for signal for a more flexible cable. The EBB boards don't have an input fuse (an odd oversight), but the EBB SB ones do, 24v/4A. EEB schematic notes 5A on the connector, but the EBB SB does not have a note on it, though it's based on the XT-30 connector, 15A continuous and 30A burst is what I'm hearing from the drone communities, so way over speced. 20awg does 5A continuous with insulation rated for 60℃, (and more with higher rated insulation, 3DO's is rated to 200℃) so I'd call that fine as you are not driving everything 100% all the time anyway. On the CAN Bus data side, most seem to suggest 18-24awg, but we are also running far shorter distances than typical CAN networks which span hundreds of meters of cabling or more. Rather than raw gauge, being robust matters more.

The EBB and U2C boards do have some sources posted, enough for most end users, but not really enough for one to directly fab boards with. You do get schematics, so that's a plus, like other BTT products.

GitHub - bigtreetech/EBB

Contribute to bigtreetech/EBB development by creating an account on GitHub.

github.com

GitHub - bigtreetech/U2C

Contribute to bigtreetech/U2C development by creating an account on GitHub.

github.com

Hope that help.

 

[majic79]

Thanks for taking the time - I did find that a number of connectors came with the EBB36 and U2C. So it's covered well enough to make a cable up, but if one of these connectors gets wrecked, it would be tricky to source a replacement - 99.99% of the time it'll be fine!, it's the tiny percentage that I worry about

 

[ChrisA]

... All the boards specify the electrical side (Can_L, Can_H, PWR, GND) but don't have any indication of load (current or power), nor do they specify the terminal (some look like Molex MicroFit 3.0mm pitch, but there seems to be at least two other terminal types being used now).

The power spec for a CAN setup is determined by the heater in the hot end. The PCB uses some milliwatts while the heater uses a few amps. The extruder motor uses power too. You can't expect the PCB makers to know the power used by your heater or motor.

 

[majic79]

They'll need to make a reasonable assumption for the copper traces on the PCB though