Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Christopher Howard <christopher@librehacker.com>
Newsgroups: sci.electronics.design
Subject: Re: modifiable backplane with sockets?
Date: Wed, 28 May 2025 13:55:32 -0800
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> How are you planning on supporting these cards? What sort of masses
> involved? Any connections to the opposite end of the card (that would
> add to the stress on such a "socket")?

I was imagining that they would be fairly small cards, something like
5mm wide by 6 or 7 mm long, with lightweight components only on the card
— small ICs, resistors, and such like. Certainly much smaller and
lighter than something like a graphics card. Nothing on the opposite end
of the card.

My original thought was to have the cables to the patch panel(s) hook
directly into a socket as well, but maybe I could have a shorter cable
going from that to some kind of plug in port on the chassis.

> Are you certain that (analog!) signal integrity won't be an issue with
> this approach? The frequencies and signal levels involved (as you
> likely will be severely constrained as to HOW a signal can be routed
> from "socket A" to "socket F")

I'm working always at low frequencies, like 100 Hz or less. The
simulations usually display on an oscilloscope at around 1 second per
scan, or slower.

> Are your modules going to use printed wiring? I.e., does the "plug"
> that mates to these sockets mount *onto* the card? Can you use
> fingers, instead (more costly to manufacture; why pay a PCB house to
> plate them when you can purchase a "plug/socket" that is already
> plated)
>

The plug would mount onto the card, unless I was using just contacts
that slide in. I am open minded to ideas.

I don't really want to use printed wiring, preferring to
experiment/design/build as I go. But I'm not really sure a practical way
to do that outside of a breadboard. Maybe I can come up with some kind
of generic printed board that gives me some flexibility on how I solder
on ICs and wires.

> How durable do you want the finished assembly to be? I.e., are you
> just trying to use it to mock-up designs? Or, are you intending to
> *deploy* a system thusly assembled? How fussy can you be in assembling
> (and disassembling) such a configuration -- how durable do the
> connectors need to be?

It would just sit on my desk. I'd need to be able to slide in/out or
(dis)connect the module cards without anything breaking. After assembly,
I would mostly be interacting with just the patch panel, not the cards,
but I'd want to be able to take cards out to tweak them, or replace
them.

> wouldn't need to be part of a "backplane PCB" but could just be
> fastened to a support member spaced appropriately from its neighbor(s)
>

Ah, okay, so I could just screw that onto some support structure, then
wire wrap to those long posts. Assuming the posts are strong enough to
endure wire wrapping.

-- 
Christopher Howard