Mail Archives: geda-user/2020/10/27/10:02:25
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| Tue, 27 Oct 2020 06:42:36 -0700 (PDT)
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| From: | "Chad Parker (parker DOT charles AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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| Date: | Tue, 27 Oct 2020 09:42:25 -0400
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| Message-ID: | <CAJZxidB9h416oC+9_WMhL7LrjDS-=qQnVg_Lw+FQEXnixAOsdQ@mail.gmail.com>
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| Subject: | Re: [geda-user] PCB, 2 parts physically in the same place
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| To: | geda-user AT delorie DOT com
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| Reply-To: | geda-user AT delorie DOT com
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I don't see any reason why pcb *shouldn't* allow overlapping parts, so long
as other design rules aren't violated. And anyway, it's somewhat difficult
to define what that actually means. Overlapping bounding boxes, for
example, is not necessarily an indicator of parts that might interfere with
each other.
The one thing that I would like to see at some point is the addition of
keepout zones. If you were to add a keepout zone to a part and then try to
put something else inside that zone, I would like that to generate a
warning.
At some point I would also like pcb to start throwing warnings about
overlapping holes, or holes too close together, or too close to the edge of
the board.
--Chad
On Tue, Oct 27, 2020 at 7:05 AM Richard Rasker (rasker AT linetec DOT nl) [via
geda-user AT delorie DOT com] <geda-user AT delorie DOT com> wrote:
> Op 26-10-20 om 16:55 schreef Peter Stuge (peter AT stuge DOT se) [via
> geda-user AT delorie DOT com]:
> > gene glick (geneglick AT optonline DOT net) [via geda-user AT delorie DOT com] wrote:
> >> I want to do this on purpose. One part, a 2X16 character display has 10
> >> connections to the PCB. Problem is, they are just holes. It is meant to
> >> have a 10 pin header on the PCB, and then the display gets positioned
> over
> >> the header and soldered in place.
> > Rather than having to deal with two footprints on top of each other I'd
> > recommend this:
> >
> > Create one 2X16LCD footprint which has no electrical connections but
> > only silk lines+text and any mounting holes (Pin with attribute "hole").
> > I'd recommend to draw silk lines around where the electrical connections
> > will go.
> >
> > Then place one 1x10 header footprint for the electrical connections.
> >
> > That way you can have both parts in schematic and BOM without having
> > redundant connections in the netlist and layout, and no problems with
> > two footprints with electrical connections on top of each other.
>
> This had occurred to me as well, but the major caveat here is alignment:
> even a minute unnoticed nudge of either part may spell very serious
> trouble.
>
> At the very least, I'd recommend combining the connector pins and
> mounting holes in the same footprint when adopting this approach. After
> all, a slightly shifted silk screen symbol isn't much of a problem, but
> mounting holes in the wrong place usually boil down to an unusable board.
>
> > In addition to local simplicity I can imagine that fabs might be unhappy
> > or at the very least confused with two drills on top of each other..
>
> Yes, that might indeed be an issue, depending on the fab house.
>
> My standard approach here is actually to NOT use a separate header
> symbol in the schematic, but simply put a warning in the display
> symbol's comment attribute to manually add the header to the bom
> afterwards.
>
> My final boms (LibreOffice spreadsheet files) contain lots of other
> parts that aren't entered in the schematic anyway, e.g. mounting studs,
> washers, screws, and nuts, bezels, brackets etcetera. So manually adding
> this header is a minor issue.
>
> But it is interesting to see that PCB allows these overlapping parts.
>
> Richard
>
>
--00000000000042c4b105b2a73864
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Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr"><div>I don't see any reason why pcb *shouldn't* al=
low overlapping parts, so long as other design rules aren't violated. A=
nd anyway, it's somewhat difficult to define what that actually means. =
Overlapping bounding boxes, for example, is not necessarily an indicator of=
parts that might interfere with each other.</div><div><br></div><div>The o=
ne thing that I would like to see at some point is the addition of keepout =
zones. If you were to add a keepout zone to a part and then try to put some=
thing else inside that zone, I would like that to generate a warning.<br></=
div><div><br></div><div>At some point I would also like pcb to start throwi=
ng warnings about overlapping holes, or holes too close together, or too cl=
ose to the edge of the board.</div><div><br></div><div>--Chad<br></div></di=
v><br><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On T=
ue, Oct 27, 2020 at 7:05 AM Richard Rasker (<a href=3D"mailto:rasker AT linete=
c.nl">rasker AT linetec DOT nl</a>) [via <a href=3D"mailto:geda-user AT delorie DOT com">=
geda-user AT delorie DOT com</a>] <<a href=3D"mailto:geda-user AT delorie DOT com">ged=
a-user AT delorie DOT com</a>> wrote:<br></div><blockquote class=3D"gmail_quote=
" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);=
padding-left:1ex">Op 26-10-20 om 16:55 schreef Peter Stuge (<a href=3D"mail=
to:peter AT stuge DOT se" target=3D"_blank">peter AT stuge DOT se</a>) [via <br>
<a href=3D"mailto:geda-user AT delorie DOT com" target=3D"_blank">geda-user AT delori=
e.com</a>]:<br>
> gene glick (<a href=3D"mailto:geneglick AT optonline DOT net" target=3D"_blan=
k">geneglick AT optonline DOT net</a>) [via <a href=3D"mailto:geda-user AT delorie DOT co=
m" target=3D"_blank">geda-user AT delorie DOT com</a>] wrote:<br>
>> I want to do this on purpose. One part, a 2X16 character display h=
as 10<br>
>> connections to the PCB. Problem is, they are just holes. It is mea=
nt to<br>
>> have a 10 pin header on the PCB, and then the display gets positio=
ned over<br>
>> the header and soldered in place.<br>
> Rather than having to deal with two footprints on top of each other I&=
#39;d<br>
> recommend this:<br>
><br>
> Create one 2X16LCD footprint which has no electrical connections but<b=
r>
> only silk lines+text and any mounting holes (Pin with attribute "=
hole").<br>
> I'd recommend to draw silk lines around where the electrical conne=
ctions<br>
> will go.<br>
><br>
> Then place one 1x10 header footprint for the electrical connections.<b=
r>
><br>
> That way you can have both parts in schematic and BOM without having<b=
r>
> redundant connections in the netlist and layout, and no problems with<=
br>
> two footprints with electrical connections on top of each other.<br>
<br>
This had occurred to me as well, but the major caveat here is alignment: <b=
r>
even a minute unnoticed nudge of either part may spell very serious trouble=
.<br>
<br>
At the very least, I'd recommend combining the connector pins and <br>
mounting holes in the same footprint when adopting this approach. After <br=
>
all, a slightly shifted silk screen symbol isn't much of a problem, but=
<br>
mounting holes in the wrong place usually boil down to an unusable board.<b=
r>
<br>
> In addition to local simplicity I can imagine that fabs might be unhap=
py<br>
> or at the very least confused with two drills on top of each other..<b=
r>
<br>
Yes, that might indeed be an issue, depending on the fab house.<br>
<br>
My standard approach here is actually to NOT use a separate header <br>
symbol in the schematic, but simply put a warning in the display <br>
symbol's comment attribute to manually add the header to the bom afterw=
ards.<br>
<br>
My final boms (LibreOffice spreadsheet files) contain lots of other <br>
parts that aren't entered in the schematic anyway, e.g. mounting studs,=
<br>
washers, screws, and nuts, bezels, brackets etcetera. So manually adding <b=
r>
this header is a minor issue.<br>
<br>
But it is interesting to see that PCB allows these overlapping parts.<br>
<br>
Richard<br>
<br>
</blockquote></div>
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