[sdiy] Free CAD (was: Proteus software)

[David G. Dixon]

> Sorry to harp on the same theme, but this is another reason not to use
> awful software, not a reason to continue drawing PCBs in Excel!

My comments about Eagle were meant in the context of doing proper CAD layout
for production PCBs.  It has nothing to do with my use of Excel, and I'm
certainly not advocating the use of Excel for this purpose.

However, from the perspective of a hobbiest, I find Excel really useful, for
the following reasons:

- I actually enjoy doing it that way (it's fun for me)
- It forces me to think very hard about the circuit I'm building
- It's fast (again, for me)
- It's free
- The square-grid layouts are perfectly suited to homebrew PCBs
- I can use the same technique to make panel wiring guides
- I can make graphical BOMs which facilititate the organization of parts
- I don't want to take the time to learn proper layout software

I developed my tool to make breadboarding easier, and it was only natural to
extend it to PCB layout.  I think of it as breadboarding with solder.

I'll admit that it's not too great for digital circuits, but it's actually
pretty painless for analog circuits (which are my main focus).