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This is a question borne of sheer ignorance, but I'm not sure if it's a good or bad thing.

I'm designing a PCB (1) that will connect to another PCB (2). The latter has all of the power, ground, IO connections, etc. The one I'm designing is sort of a daughterboard that will offload some of the connections. Currently, I'm running 34 wires to the daughterboard, two of which are GND. Because I have a ground plane, if both of these GND wires are connected to ground pins on PCB(2), assuming a common ground plane there, are there any benefits? Are there downsides?

I did this for two reasons:

  1. Redundancy
  2. Ensure tolerance of all grounded devices

But thinking it through, I'm concerned about:

  1. Creating a ground loop
  2. Possibly different potentials due to trace length (minimal, the whole PCB(1) is roughly 4cm x 4cm)

So - should I change my design to not contain two ground wires back to PCB(2)? I won't be mad about freeing up another wire, for sure.

Update with additional information:

This is for a 3D printer, moving connections from the main boards to a daughterboard in the tool side.

The main electronics are a Duet Wifi board and a Duex 5 board. These boards are both wired to separate +24v connections from the PSU, but the ground is daisy chained (PSU -> Duex5 -> DuetWifi) to ensure a common ground and no variance in potential. Both boards have a variety of connectors (fans, sensors, etc) that include a ground pin. I don't want to carry a ground wire for each of them to the daughter board as it adds unnecessary weight and eats wires that could be used for other signals.

The plan is/was to use to ground wires (one from each of the two main boards) to wire a common ground plane on the daughterboard that anything which needs grounding wires into.

My thought was that there's both redundancy and that connecting to the ground plane on each of the two main boards, whose ground planes are directly connected as well, would help to ensure potential across all devices connected to any of the three boards.

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  • \$\begingroup\$ HOw is the ground plane connected to each board? show a photo or illustrate. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 21 at 1:52
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    \$\begingroup\$ when I connect a couple of boards, I might have up to 50% of the wires between them as ground, and it has even been more. \$\endgroup\$ – Neil_UK Jun 21 at 5:48
  • \$\begingroup\$ @Neil_UK - With a common ground? Interesting. Initially I didn't think it would be an issue, but I guess I got a bit paranoid. This is good to know - thank you. \$\endgroup\$ – Jesse Williams Jun 21 at 17:48
  • \$\begingroup\$ @SunnyskyguyEE75 I added some information, and links to wiring diagrams of the two main boards. \$\endgroup\$ – Jesse Williams Jun 21 at 17:55
  • \$\begingroup\$ That doesn’t show the ground plane you have for both. So use a wide flat braid or copper for joining all grounds for best performance . A ground plane is 1:1 and 8:1 is 0.5nH/mm length ok? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 21 at 20:03
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I don't think this will cause any issues. Although technically this is a loop, ground loops are usually a problem when some device has multiple "ground" connections which may differ slightly in potential. This won't occur here since there are no devices in the loop.

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