Thanks, to everyone who replied so far, for the good suggestions and information!
This re-design is still in the very early stages. I don't know if this is too off-topic. But I'll post a sort of summary of the different board/connector options I'm considering (mostly copied from an email that I sent to a friend, recently, about this stuff). Maybe some of you can set me straight, or offer some practical tips, or some ideas.
I am re-designing an instrument that I produce (both in kit form and pre-assembled), mainly to change the (printed circuit) board-to-board and board-to-front-panel wiring schemes. The instrument in question is a "Curve Tracer" (a type of test equipment). See it at
http://www.fullnet.com/u/tomg/gooteect.htm . Previously, the three circuit boards in the unit were all single-sided, with all through-hole components. And all connections to and from all front panel controls and i/o connectors, and other boards, were implemented as soldered-in discrete wires.
In order to make the instrument much easier to produce, easier to maintain, easier to upgrade, and maybe even more reliable, I am replacing ALL discrete wiring (if possible) with ∗socketed∗ connectors (and multi-wire cabling) and/or printed circuit board traces. The front panel controls and i/o connectors are all being changed from solder-lug types to pcb-mount types. And a new printed circuit board is being added, for them, behind, and parallel to, the front panel.
All connections from front panel controls and i/o connectors, as well as all board-to-board connections, will now (probably) be routed through pcb traces on the new front panel pcb, to socketed connectors' sockets' pins. Each board will have at least one socketed (or other mass-) connection to the front panel's new pcb.
This re-design project is still in the VERY early design phase. And I am still trying to finalize the basic interconnect method(s) that will be used. I'm pretty sure that all of the boards will have to change from single-sided to double-sided, just to be able to have room to run the new traces to the connectors. The main board has at least 50 connections that need to go to the front panel (mostly), or to the other two boards. The other two have fewer than 15 connections each that need to go to the front panel or to the other boards. The three original boards are all mounted horizontally, next to each other, on small "risers"/spacers that are part of the bottom of the enclosure. All three have one edge that is very close to (but perpendicular to) the front panel.
There are several possibilities that I have considered:
1) pin headers on each pcb, with ribbon cables running to similar headers on the front panel's new pcb, or
2) card-edge connectors on the front panel pcb, along the bottom, that each of the three pcboards' edges could plug into, or
3) right-angle headers or sockets on each pcb, that would plug directly into straight headers or sockets on the front panel pcb (pin headers and sockets, or DIN, or even D-Sub), with NO CABLING necessary, or
4) another new board, a "motherboard", in the bottom of the enclosure, with card-edge sockets, along with a total redesign of the current boards' layouts, so they could be mounted vertically, in the MB's sockets, and a new front panel pcb that would also plug into a card-edge socket on the new motherboard, or
5) card-edge sockets on all the pcbs, with small pcbs that plug into them, with discrete wires or ribbon cables soldered to the small pcbs (i.e. hand-made custom card-edge-connector cabling, hehehe...),
6) pcb-mount terminal blocks with discrete wires, or
7) something similar to #1, but with some as-yet-unknown (to me) connector and/or cabling types (I even considered pcb-mountable modular phone jacks and cabling).
Which of those (probably out of #1 through #4) sound "good"?
One immediate "problem" I can foresee, with just adding a second side to each pcb and then running traces (on the "new" side of each board) to pin headers: Our pcb-making process is rudimentary and does NOT include the ability to make plated-through holes. SO, to have headers that are connected to the new top side traces, while the connectors are also sitting on the top sides of the boards, I wouldn't be able to solder the top side's trace directly to the headers' pins, since the headers sit right on the boards. So I'd have to make an extra row of holes next to each header row, that could have pins inserted that could be soldered on both sides. (I was thinking I might just use a single-row header, upside down with the longer pins halfway into the holes. It might be "ugly". But it would also provide handy test-points...).
Many of the switches in the unit just happen to use groups of six connections. So, for many on-board and board-to-board "jumpers", short lengths (six or eight inches max, probably) of 6-conductor ribbon cables might be handy, although, changing to double-sided boards might ("should") eliminate that need.
The primary GOAL is still to make the unit easier, faster, and cheaper to assemble. SO, I really don't want to use cabling schemes that require a lot of time or expensive equipment, to assemble (IDC?). Socketed connections are preferred, so that units can be easily disassembled for repairs or board-level upgrades. If ribbon cables are used, I would prefer having pre-assembled cables available.
I did buy a couple-hundred new IDE 40-pin cables (with three 2x20 sockets each), for $5! And I got several hundred 40-pin breakable gold-plated single-row pin headers for about $10. And I got 300 2.5-inch-long 36-wire ribbon cables that have 36-pin single-row sockets on both ends, for $30 including shipping, and 200 36-pin single-row gold-plated headers for about $5 or $10. (Actually, I got the ∗300∗ of the new IDE cables, for $5.99 plus $21.42 s/h.)
SO, I may end up cutting the IDE cables so they have just two sockets with about 8 inches of cable between them, and using those. Or I may use the short 36-pin cables and single-row headers.
However, I am ALREADY running into the problem of ∗possibly∗ not having enough ROOM on the new front-panel PCB, for that many large connectors. SO I ∗STILL∗ probably need to find something smaller (fewer conductors), for the two smaller boards to use, to connect to the front panel PCB, and/or to the other boards.
ANOTHER IDEA: If I could find a very large (and very cheap) surplus stockpile of ISA "RISER BOARDS" (or even 8-bit passive backplane boards, or somesuch) that have 5 or more slots, those could make PERFECT ready-made
motherboards, to mount in the bottom of the case, with the slots parallel to the front panel. Then ALL of my boards could plug into the slots and all be connected together, including the front panel. Of course, I could make my own similar motherboard-type boards, fairly easily, with available card-edge connectors. (But the large, new card-edge-connectors are usually quite expensive. Maybe I can find a large surplus lot of them...) But MAYBE there's a really low-cost stockpile of something similar, somewhere, which would certainly make things MUCH easier and faster and cheaper.
There are also several connections to the rear panel, usually with only one or two wires, that I need to worry about. I am thinking of using either one- and two-wire pin headers and sockets, for those, or small terminal blocks of some type. However, I still would LIKE to have all pre-assembled cables (i.e. sockets already on both ends of appropriate-length cabling.
Peak currents in some of the signal conductors could reach 1.5 Amps. However, most of those waveforms are triangular or sawtooth, making the average (DC-equivalent) current only HALF of the peak value. But the main DC power supply rails MAY have to be connected from the separate power supply board to the other boards using discrete wiring that's screwed into terminal blocks, for that reason (max current-carrying capability).
Sorry to have blathered-on for so long, here! If there's anything you can offer, I'm all ears!
Thanks again!
Regards,
Tom
Tom Gootee
tomg@...http://www.fullnet.com/u/tomg[Non-text portions of this message have been removed]