Physical design of backplane

[Mark T]

Some time ago I thought about redesigning my own modular backplane. I originally used 0.7 inch spacing but wanted to change to a more standard 0.6 inch spacing. Also as with Steve's designs maintaining modules on a multiple of 0.6 inch spacing.

I was trying to include dimensions that would allow front, back and side panels to be constructed with pcbs. Plan to have 0.6 inch side panel strips separated by v-score now seems to be out of the question due to jlcpcb charging extra for v-score.

Space between front panel pcb and front panel is based on the size of toggle switches and would still allow leds soldered on the pcb to be mounted on the front panel.

The last connector on the module could be a right angle female header to another backplane module, or a vertical module with the space to the back panel to suit pcb mount dsub connectors. Also usefull for horizontal mounting of modules during debug.

Front panel pcb would have vertical female header on the inside surface to mate with right angled male header on the modular backplane, allowing the front panel to extend down to the top of the base of the enclosure, while the actual front panel would extend to the bottom of the base to cover the front surface of the enclosure.

Top and bottom panels would probably be in laser cut acrylic, but still undecided as t-slots and nuts doesn't seem a very good method of assembly. I don't think I could drill and tap the edges to get a good finish.

Mark

[Steve Cousins]

On the subject of making cases out of PCB material, you could just solder them together. 

I've done a bit of stained glass work and feel confident that acceptable results could be achieved by having an exposed 'track' along the edge of the PCB (inside surfaces of the case) and soldering the panels together.

Somewhat off topic and a terrible picture, but this is something I made:

I have considered making a glass case for one of my systems. I can drill holes in glass for mounting switches and LEDs, but I doubt I could cut small slots.

Steve

[Alan Cox]

Somewhat off topic and a terrible picture, but this is something I made:

Nice..

For general cases I've mostly given up bothering because I can get good quality metal cases from China for under a tenner so it gets almost pointless. The SC111 is in a little wooden chest but even those are so cheap it's not worth making one by hand and I bought the basic chest.

My experiences of drilled/tapped acrylic have not been good after a relatively small number of open/closes.

Alan

[Karl Albert Brokstad]

Hi Steve 

Nice decoration!

I was about to contact you about this topic. What is the dimension of the PCB for Z180 motherboard and the Z80 motherboard?

I have made enclosed two systems into the blue-box which is available on ebay and is very inexpensive. 

If the motherboards fit, maybe these blue boxes could be the recommended enclosures?

Karl

[Bill Shen]

This is the Pactec enclosure I used many years ago.  It is for PC board with 4"x4.75 max dimension, so should fit a 102mmX102mm board just fine.  The thickness of the front and back panels are 62mil (1.6mm), so perfect for PC board-based front and back panels.  https://www.ebay.com/itm/Lot-of-42-NEW-Pac-Tec-CM5-125-5-2-x5-1-x1-5-Black-Plastic-Electronic-Enclosure/352623311182?hash=item5219fcb94e
  Bill

[Mark T]

Soldering the side panels might be a bit permanent for something I want to keep modular.

I had thought about using pin headers to hold it all together. Through hole types might be a bit ugly having soldered connections on the outside surface. I also considered smt pin headers, but not convinced of the mechanical strength of the copper to fr4. Also the alignment of plugs to sockets would be tricky with smt handsoldered.

For a single board computer its probably best to pick a case that is easily available and design the board to suit the case, but most examples I've seen don't seem to have considered a case.

Mark

[Steve Cousins]

Karl

SC126 (Z180 motherboard) is 6.3" x 4.0" (160.02mm x 101.6mm)

SC114 (Z80 mothernoard) is 4.0" x 4.0" (101.6mm x 101.6mm)

Both designs have a horizontal bus socket which overhangs the edge of the PCB although you might not fit these if you intend to box the finished item.

SC126 has barrel power socket and on/off switch which overhang the edge of the PCB. Depending on your choice of header pins (straight or angled) for some of the connectors you may also need to allow room these.

If you want hole positions etc the designs are on EasyEDA.

Steve

[Steve Cousins]

Hi Mark

"Soldering the side panels might be a bit permanent for something I want to keep modular."

I was thinking of a two-part case: Top and sides as one assembly and bottom/front/back as another, so the top would lift off. But I see your point.

I'd have thought surface mount headers would be strong enough unless you mistreat your computer :) Perhaps a few via holes around the connector would held strengthen the copper.

I think a case made from PCB material would be nice. Karl's Black Adder set looks great, so perhaps black would be worth a try.

Steve