Wire Wrapping Pain
I’m beginning to really hate wire-wrapping. Sure, it’s easy to make modifications to the wiring, and the finished result will be nice and sturdy, but it’s SO SLOW to build! Now that my board is getting pretty full, it’s hard to even see the pin numbers, and I have to hunt around to find the endpoints of each wire. And especially when I need a length of wire that I don’t already have pre-cut, I have to spend more time measuring, cutting, and stripping. All told, I’m averaging a couple of minutes per wire. After about an hour of wire-wrapping, my brain overdoses on connections from AG32 to BB08, I begin to feel dizzy, and I have to stop. This has been my first wire-wrapping project, and I think it will be my last.
What then, if not wire-wrapping? A solderless protoboard is nice for prototyping, but doesn’t work well for large designs. It’s also not very permanent, since it’s easy to accidentally knock a wire loose. I could hand-solder point-to-point wires on a breadboard, but I think that would be like wire-wrapping, only worse. For medium-large designs like BMOW, I think the only real alternative is custom printed circuit boards. Unfortunately custom manufactured PCBs are expensive, at $50 to $100 depending on the size and quality. They’re also difficult to modify if you discover an error, so you’ll probably need to go through several versions of the PCB before you get something that works. Some people have had good success making their own PCBs at home, but it involves some nasty chemicals and drilling lots of holes and other headaches I’d rather avoid.
I did some comparison shopping for a hypothetical 4×6 inch 2-layer custom PCB:
Futurlec: $41 for a single plain board. $77 with soldermask and silkscreen.
BatchPCB: $70, including soldermask and silkscreen. Long lead times.
ExpressPCB: about $70, no soldermask or silkscreen.
Most places have a fairly high setup cost, but low cost for bigger boards, or higher quantities of boards. For example, Golden Phoenix will make a 100 square inch board with soldermask and silkscren for $89, and a 155 square inch board for $99.
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Have you considered something like http://www.rrunner.co.uk/kits/wiring_kits.htm? I’m sure you could find something similar in the US. I’ve not used it myself, but have seen some very neat boards using the system and hear good reports.
Merlin
I think Andrew Holme used a Road Runner wiring kit for his Mark 1 Forth Computer. As I understand it, it’s basically point-to-point hand-soldered wiring, except you wire an entire net at once instead of just a single pair of pins? That might not be so bad: half the number of solder connections, and less importance on measuring the wire. And no wire stripping? On the downside, if you need to remove a wire, you need to remove the whole net.
I don’t recall ever seeing the same thing advertised elsewhere, but I could always order it direct from the UK. I’ll give it a closer look next time I start a new project.
I’ve used the Road Runner type wiring pen before, and it works well for everything apart from power wiring. The wire is too thin to carry any significant current. It smells a bit when soldered, too, so you may need to keep a window open. It’s just as difficult to modify as wire-wrap, though, if you need to change a wire in the middle of a run.