[sdiy] Free CAD (was: Proteus software)

[Ian Fritz]

At 02:37 PM 2/20/2011, Tim Parkhurst wrote:
>On Sat, Feb 19, 2011 at 9:46 AM, Jay Schwichtenberg <jays at aracnet.com> wrote:
> > There are a couple more things out there for the PC. TinyCAD and FreePCB. I
> > played with them and they didn't seem all that bad and there are Yahoo
> > groups for support.
> >
> > One thing that bugs me about a number of the PCB programs out there is that
> > they work from schematics. If you want to just draw up a PCB they become a
> > real pain. They require you to manually build a 'node list' for the 
> board as
> > you go.
> >
> > Jay S.
> >
>
>Although it's a bit of a pain, that is how "real" PCB layout programs
>work. The advantage to this is that the layout portion of the program
>will compare the tracks you are laying out to the netlist, and will
>not allow you to make a bad connection (i.e., one that doesn't exist
>in the schematics). You can also run a check to make sure you haven't
>missed any connections. It's not 100% bulletproof, but if your
>schematic is correct, then your PCB layout should be too.
>
>If you're looking for a program where you can simply draw up a PCB
>without having to go through all this, you can get great results from
>AutoCAD or CorelDraw. The problem there is that you no longer have
>automatic checking of PCB tracks vs. schematic/netlist.

FreePCB allows you to do board layouts from scratch without schematics.  It 
automatically makes up the netlists and gerbers, allows DRCs, etc.  I do it 
all the time.  Am I missing something?

Ian