Re: modifiable backplane with sockets?

On 5/29/2025 10:07 AM, Christopher Howard wrote:

Don Y <blockedofcourse@foo.invalid> writes:
 

If you are using perfboard, you will be constrained as to the locations
and placements of devices (based on the "holes").  If you can stick
with DIP packages, this could be OK.  SMT might be a stretch to fabricate
like this (esp if you didn't want to be forever "patching" it)

 The first analog computer used just DIP and through-hole components. I'm
open-minded at this point on DIP vs SMT — but I don't really know how to
prototype with SMT components and the stuff I've read
scratching/drilling divides into copper boards doesn't sound very
practical. But maybe I should try something new. Copper-clad perfboard
sounds like it might be a practical, inexpensive approach.

You're "building" at two different levels.
You are creating these "modules".  Then, interconnecting them (via your
"backplane")
Can I step back and ask what roles each of these activities will play?
E.g., when I was in high school, I built a football (american) game
out of "analog computers" and "logic boxes" (we didn't have "real"
computers at that point).  It was ferried to school on a 4x8 sheet
of plywood, largely because the analog computers and logic boxes were
physically large -- like briefcases that (open) exposed their functions
for use.
The individual modules (sum/gain/integrate/etc.) were hidden "inside"
the OPENED briefcases.  They were interconnected using discrete wires
with tapered pins that could be wedged into holes in the briefcases.
(so, they were somewhat permanent but could be dislodged with deliberate
effort)
I'm likening your project to the modules being the sum/gain/integrate/etc
functions implemented in your "modules" with the "tapered pin interconnects"
being your "backplane".  Is this approximately true?  I.e., once you've
designed the individual modules, they'll be static (likely replicated)
with the real changes happening in the backplane wiring?
If so, how persistent (permanent) do you need this to be?  I'm sure
a 4'x8' board is impractical (I had to build it in the basement) but
could some other form of interconnect be MORE appealing?
I'm thinking back to the days when Radio Shack sold kits of components
mounted on a piece of cardboard in a "board game sized" box with
"springs" used to connect wires to each endpoint of each component.
(bend spring to open a gap in the coils, insert wire, release -- spring
holds wire captive).
How much of your goal is flexibility in reuse vs. size vs. cosmetics?

The real downside risk would be if *a* post snapped while the others
were intact.  You'd have to remove the entire connector just to
restore that post's functionality.
>
[If the entire "site" was unused when the break happened, you just
replace the whole connector.]

 So, on the "postage stamp" board, how do you think I should do the
interconnections? Wire wrap between posts? Or just do a solder bridge
over to the next perfboard hole and connect a wire to that?

Dead bug or some variation thereof.  If you use leaded components,
you have the length of the leads to determine how far apart
components can be.
If (as I've assumed), you want the modules to be durable and reusable,
you could pot them when completed; all you need is access to the
pins of the *module*, not their internals.
(With DIP carriers, you could glue a cover onto the base to protect the
components and interconnects hidden inside)