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From:	"Gene Heskett (gheskett AT shentel DOT net) [via geda-help AT delorie DOT com]" <geda-help AT delorie DOT com>
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To:	geda-help AT delorie DOT com
Subject:	Re: [geda-help] adding missing footprints
Date:	Sat, 16 Jan 2016 00:48:13 -0500
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Reply-To:	geda-help AT delorie DOT com

On Friday 15 January 2016 19:06:12 Gene Heskett (gheskett AT shentel DOT net) 
[via geda-help AT delorie DOT com] wrote:

> On Friday 15 January 2016 07:58:57 gedah AT igor2 DOT repo DOT hu wrote:
> > On Fri, 15 Jan 2016, Gene Heskett (gheskett AT shentel DOT net) [via
>
> geda-help AT delorie DOT com] wrote:
> > > Greetings, new subscriber;
> > >
> > > Using gEDA as in the debian wheezy repo's, although I was able to
> > > get a newer pcb to build, so it is 1.99z.
> > >
> > > I have composed a little 6 part schematic in gschem, but when I do
> > > the translation gsch2pcb step, 4 of the 6 parts I chose schematic
> > > symbols for, have no "footprint" and are omitted from the pcb.
> > > Loaded into pcb, it obviously makes no sense to this beginner.
> > >
> > > Can this data be added to the library part description?
> > >
> > > If so how?  And if I do it, how can I submit back to gEDA?
> >
> > For the PCB workflow, you need to specify the "footprint" attribute
> > in gschem. It is not possible to ship a generic purpose lib with
> > footprints already set because most devices are available in
> > different footprints (e.g. lm358 in SO8 or DIP8, 2n3904 in to92 or
> > sot23 or even dual NPN in sot23 with 6 pins).
> >
> > HTH,
> >
> > Igor2
>
> Can this be done with a text editor, or must it refer to a known
> pattern from a library entry somehow?
>
> IOW, where does this "footprint" data come from?
>
> As a for instance the transistor is a 2SK3264 mosfet.
>
> The diodes are 1N5822's, and because they are bulky bodied, will
> likely be mounted standing up, and that may still require pads on >100
> mill centers.  That same pattern will serve for mounting everything
> but the transistor, which of course has 3 legs.
>
> FWIW, I drew up a perfectly servicable pcb pattern in pcb 2 days back,
> but when I exported it as gcode, what should have been about 100k of
> gcode, was 1500 bytes and didn't backplot anything but a small blob,
> so obviously it ignored what I drew and placed on the bottom of the
> pcb.
>
> I figured on reversing the drill file and using it to make clearance
> for short prevention on the top side as I only have double-sided
> board.  I have also made double-sided boards before with eagle, but I
> can't get the latest 7.5 to even unpack.
>
> If I could draw it in pcb, and export working gcode, that would be
> ideal.

And I have essentially done that although the used real estate on the 
board could be shrunk some. But for the I/O connection to the outside 
world, a via is about 10% of the solder area that I need, so I need to 
delete those 3, and convert them to something that gives a nominally 
1/8" diameter solder pad on the end of the trace.

Suggestions?

I wound up using the R025 footprint for the 5 passive two terminal parts.

But running the code in LCNC, I see it only makes a single isolation 
pass, and the etching tool I would normally use is a carbide 60 degree V 
bit with an effective radius of about 2 thou when I drive it 3 thou 
deep, which is deep enough to wear it out eventually digging that deep 
into the fiberglass board substrate.

FWIW, pcb-gcode, used with eagle, expects that sort of a cutting tool and   
does multiple passes, stepping over about a thou and a half per pass to 
get 15 thou of isolation, which makes it quite slow production wise.

So would I be better off using a .039" endmill for the isolation cut, 
which also makes a good drill for most lead holes?  Or is that so big it 
will chew up the adjacent solder pad under the TO220 transistor?

I also have some .03125" carbide end mills, but there's very fragile, and 
damned fragile as I found when making the ebony screw covering buttons 
for some Green & Green style blanket chests I have under construction.  
I had to use feedrates in the 2 ipm range, cut depths of 5 to 8 thou, 
and a vacuum to keep the cut clean to avoid a flute packing full of dust 
& breaking a $13 tool. One size of those I had to make 136 copies of.  
Fun or boring, depending on ones viewpoint.

One of these will be controlling that vacuum when these are done.

Yup, I occasionally call myself a JOAT.

And I just noted something else. It appears to assume I am using single 
sided pcb, and I have none, its all 2oz and double sided. I can drive 
the mill from the keyboard after turning the board over, in order to 
prevent lead shorts to the top side copper, but it would be nice to have 
a top drill.  If I can get the witness marks to work, I can cp and 
mirror the bot.drill, so thats not a huge problem, just a surprise.

Was there some option I should have enabled?

Thanks guys.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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