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From: "Erich Heinzle (a1039181 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Date: Wed, 28 Oct 2020 03:37:41 +1030
Message-ID: <CAHUm0tMcSaUh4tE2KFaZbKW0PN6uToZPqRJLeg8UspzE8QvP+w@mail.gmail.com>
Subject: Re: [geda-user] PCB, 2 parts physically in the same place
To: geda-user <geda-user AT delorie DOT com>
Reply-To: geda-user AT delorie DOT com

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On a related note, there is a huge number of LCD footprints on
gedasymbols.org that I ported to gEDA .fp format, which might save
reinventing the wheel a bit.

Regards,

Erich

On Wed, 28 Oct 2020 00:52 Chad Parker (parker DOT charles AT gmail DOT com) [via
geda-user AT delorie DOT com], <geda-user AT delorie DOT com> wrote:

> 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
>>
>>

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<div dir=3D"auto">On a related=C2=A0note, there is a huge number of LCD foo=
tprints on <a href=3D"http://gedasymbols.org">gedasymbols.org</a> that I po=
rted to gEDA .fp format, which might save reinventing the wheel a bit.<div =
dir=3D"auto"><br></div><div dir=3D"auto">Regards,</div><div dir=3D"auto"><b=
r></div><div dir=3D"auto">Erich</div></div><br><div class=3D"gmail_quote"><=
div dir=3D"ltr" class=3D"gmail_attr">On Wed, 28 Oct 2020 00:52 Chad Parker =
(<a href=3D"mailto:parker DOT charles AT gmail DOT com">parker DOT charles AT gmail DOT com</a>) =
[via <a href=3D"mailto:geda-user AT delorie DOT com">geda-user AT delorie DOT com</a>], &=
lt;<a href=3D"mailto:geda-user AT delorie DOT com">geda-user AT delorie DOT com</a>&gt; w=
rote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex=
;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div>I don&#=
39;t see any reason why pcb *shouldn&#39;t* allow overlapping parts, so lon=
g as other design rules aren&#39;t violated. And anyway, it&#39;s somewhat =
difficult to define what that actually means. Overlapping bounding boxes, f=
or example, is not necessarily an indicator of parts that might interfere w=
ith each other.</div><div><br></div><div>The one thing that I would like to=
 see at some point is the addition of keepout zones. If you were to add a k=
eepout zone to a part and then try to put something else inside that zone, =
I would like that to generate a warning.<br></div><div><br></div><div>At so=
me 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.=
</div><div><br></div><div>--Chad<br></div></div><br><div class=3D"gmail_quo=
te"><div dir=3D"ltr" class=3D"gmail_attr">On Tue, Oct 27, 2020 at 7:05 AM R=
ichard Rasker (<a href=3D"mailto:rasker AT linetec DOT nl" target=3D"_blank" rel=
=3D"noreferrer">rasker AT linetec DOT nl</a>) [via <a href=3D"mailto:geda-user AT del=
orie.com" target=3D"_blank" rel=3D"noreferrer">geda-user AT delorie DOT com</a>] &=
lt;<a href=3D"mailto:geda-user AT delorie DOT com" target=3D"_blank" rel=3D"norefe=
rrer">geda-user AT delorie DOT com</a>&gt; wrote:<br></div><blockquote class=3D"gm=
ail_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 hre=
f=3D"mailto:peter AT stuge DOT se" target=3D"_blank" rel=3D"noreferrer">peter AT stug=
e.se</a>) [via <br>
<a href=3D"mailto:geda-user AT delorie DOT com" target=3D"_blank" rel=3D"noreferre=
r">geda-user AT delorie DOT com</a>]:<br>
&gt; gene glick (<a href=3D"mailto:geneglick AT optonline DOT net" target=3D"_blan=
k" rel=3D"noreferrer">geneglick AT optonline DOT net</a>) [via <a href=3D"mailto:g=
eda-user AT delorie DOT com" target=3D"_blank" rel=3D"noreferrer">geda-user AT delori=
e.com</a>] wrote:<br>
&gt;&gt; I want to do this on purpose. One part, a 2X16 character display h=
as 10<br>
&gt;&gt; connections to the PCB. Problem is, they are just holes. It is mea=
nt to<br>
&gt;&gt; have a 10 pin header on the PCB, and then the display gets positio=
ned over<br>
&gt;&gt; the header and soldered in place.<br>
&gt; Rather than having to deal with two footprints on top of each other I&=
#39;d<br>
&gt; recommend this:<br>
&gt;<br>
&gt; Create one 2X16LCD footprint which has no electrical connections but<b=
r>
&gt; only silk lines+text and any mounting holes (Pin with attribute &quot;=
hole&quot;).<br>
&gt; I&#39;d recommend to draw silk lines around where the electrical conne=
ctions<br>
&gt; will go.<br>
&gt;<br>
&gt; Then place one 1x10 header footprint for the electrical connections.<b=
r>
&gt;<br>
&gt; That way you can have both parts in schematic and BOM without having<b=
r>
&gt; redundant connections in the netlist and layout, and no problems with<=
br>
&gt; 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&#39;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&#39;t much of a problem, but=
 <br>
mounting holes in the wrong place usually boil down to an unusable board.<b=
r>
<br>
&gt; In addition to local simplicity I can imagine that fabs might be unhap=
py<br>
&gt; 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&#39;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&#39;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>
</blockquote></div>

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