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From: Don Y <blockedofcourse@foo.invalid>
Newsgroups: sci.electronics.design
Subject: Re: mountable power ports
Date: Wed, 26 Mar 2025 09:40:51 -0700
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On 3/26/2025 8:56 AM, Christopher Howard wrote:
> Hi, my project box is a large tin cookie box. I need to bring in +15V,
> -15V, and GND lines from my external bipolar power supply. (I was
> thinking I would have a separate bolt for the chassis ground, which
> would go off to a big ground bus bar near my workbench.) For the three
> lines from the power supply, I am wondering what would be the best (but
> economical) choice for a power connector to mount into the side of the
> project box. Something that sounded appealing was the spring speaker
> terminal clips I see on Amazon, but the downside there is they only come
> in pairs of two or four, rather than three, and they are color coded
> red/black which does not quite make sense here. I am inclined to leave
> the wires on the power supply itself bare on the end, rather than
> attaching some specialty connector to those.

There's always the old benchtop standard of binding posts.
This provides the most flexibility in connection -- by providing
the least convenience!  :<  (you can buy dual banana plugs
to mate with a pair of appropriately spaced binding posts;
but, there is nothing to prevent you from plugging them
"upside down")

What sort of current carrying capacity do you require?
There are lots of three-pin connectors available -- especially
as your current handling requirements go down.

Note that you will likely want to require the connector to
be mated/unmated with power *off* if you have any concern
over power sequencing (as many connectors won't guarantee
which conductors(s) make/break first/last).

Round will be preferable as you can just use a drill to make
a clean hole (instead of needing a punch or resorting to a nibbler).

If other similar connectors might be prevalent "nearby", you
may want to avoid them (e.g., the ubiquitous barrel connectors)
to avoid the possibility of confusion between which cable end
mates with which device.

And, should consider how much mechanical security you want (need);
is there a risk that the connection may open if you are inclined to
move the box to some other location while powered?

I have been using a sturdy circular connector family for user-maintained
connections around the house, similar to this:
<https://www.theindustrymart.com/Upload/images/product/4-pin-metal-aviation-connectors-plugs-gx25-male-female-docking-cable-straight-circular-aviation-connector.jpg>
They are available with a variety of pincounts in the same basic
size.  The threaded collar ensures they can remain mated regardless
of orientation and (minor) tugs on the cables.

They are also large enough to make assembling/repairing a cable assembly
easy to do without special tools (as they have to be assembled and
repaired in the field).