[sdiy] PC board from artwork?

Thu Oct 20 05:40:53 CEST 2016

Hi Quincas,

I have made a bunch of little graphics in Excel, using just rectangles,
lines of various colours, etc, which represent chips, resistors, caps,
diodes, etc, with their leads and pins.  The first thing I do is set the
grid to 16 x 16 pixels so that the spreadsheet cells are all little squares.
Each square represents 0.1".  Then I select "Snap to Grid" in the Drawing
menu so that when I move the parts around they snap to the 0.1" grid.  Then
I just do the layout by pure blunt force by carefully working through the
schematic.

The layouts are facilitated by sticking to a certain basic plan.  The power
rails go down the middle of the board from left to right, and all the chips
straddle these rails.  Hence, the first row of pads next to the rails
accommodate the chip pins.  The next rows of pads are for things that
connect between adjacent chip pins, like small stability caps in opamp
feedback loops.  The next pads are for components connecting out from the
chips, such as resistors and diodes.  These are all 0.4" long, and thereby
straddle three potential rows of traces and/or pads.  I call this three-lane
conduit the "boulevard" and it is through here that I route signals around
the board.  Beyond that is a row of pads for the other end of all the
resistors and diodes, and then a row of pads for off-board connectors, and
finally a ground trace which typically encircles the entire board.  The
boards are arranged symmetrically around the rails.  This means that all of
my analog boards are either 2.1" wide, or 4.0" wide for "double-wide" boards
(which share a ground trace down the middle between the two halves).

Once I've got the layout done, connecting all the parts with different
coloured traces (lines with ball ends in Excel), and the layout is reviewed
and error-free, then I copy this layout to make several different graphics.
One is "parts-only", one is "traces-only", and one is "pads only".  The
"traces-only" graphic is made up of all the traces in the layout, and is
made up of several layers of lines.  All traces are made up of three layers
of lines, with ball ends of various sizes to make up pads, and smaller lines
with small ball-ends on every line to give rounded corners.  Finally, all
power and ground traces are copied and made wider than other traces.  These
are all consolidated into a single graphic.  The "pads-only" graphic is made
up of small circles combined with larger invisible squares to force them to
align on the grid.  These small circles sit over the ball ends of the
traces, and exist to provide small drill-guide holes for the pads for easy
drilling.

Finally, the pads and traces are turned black and combined to make the
transfer graphic.  This is what is printed and transferred onto the PCB.
Finally finally, the transfer graphic is covered with a semi-transparent
white rectangle, and then the "parts-only" graphic is superimposed on this,
and that makes the "build pic" which is actually what the completed board
will look like.  I use this graphic when I'm stuffing the board.

Sorry, that was long, and probably hard to follow.  I'll just email you an
example so you can see for yourself.

Dave

  _____  

From: Quincas Moreira [mailto:quincas at gmail.com] 
Sent: Wednesday, October 19, 2016 7:45 PM
To: David G Dixon
Cc: KA4HJH; sdiy
Subject: Re: [sdiy] PC board from artwork?

David, could you describe how you lay out PCBs in Excel? very curious :)

On Wed, Oct 19, 2016 at 7:36 PM, David G Dixon <dixon at mail.ubc.ca> wrote:

Hi Terry,

I can rework the layout to accommodate more typical quad opamps such as
TL074.  This is actually very easy for me to do.  I do it in Excel.  With
the graphic and the schematic from the article, I can reproduce the layout
in Excel very quickly and then manipulate the layout to change the opamp
pinouts.  No problem.

I could also add some sine shapers if required.  I have a nice design for
sine shapers which I could basically drop onto the board.  It would get a
tiny bit bigger, though.

> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces@
<mailto:synth-diy-bounces at dropmix.xs4all.nl> dropmix.xs4all.nl]
> On Behalf Of KA4HJH
> Sent: Wednesday, October 19, 2016 4:44 PM
> To: sdiy
> Subject: Re: [sdiy] PC board from artwork?
>
>

> > On Oct 19, 2016, at 5:57 PM, Byron G. Jacquot
> <thescum at surfree.com> wrote:
> >
> > I'd be happy to redraw it in Eagle, and generate Gerbers,
> if it comes to that.  It'd be a quick hour or so.  You'd
> still have to find somewhere to fab 'em - I typically use
> OSHPark or Advanced Circuits.
> >
> > It's worth noting that the original design uses 4136's, but
> might be more useful if they were swapped to the more common
> quad op-amp package.
>
> That was one of the main changes I would make if, in my dream
> world, I could actually redo the whole thing. Fortunately I
> have lots of 4136s.
>
> The other thing is that it might be interesting to put sine
> shapers on the oscillators that form the Lissajous baseline.
> I don't know how it would look with an ellipse instead of a rhomboid.
>
>
> > On Oct 19, 2016, at 5:40 PM, David G Dixon
> <dixon at mail.ubc.ca> wrote:
> >
> > I would be happy to make one for you, Terry.  I make my own
> boards all
> > the time, and sell quite a few of them to other hobbyists.
> >
> > I have one or two questions about the layout graphic, but
> we can deal
> > with that if you decide you want me to do it.
>
> This list is getting more helpful all the time. I need to get
> past Halloween before doing anything but after that...
>
>
> > On Oct 19, 2016, at 5:54 PM, Dave Manley <dlmanley at sonic.net> wrote:
> >
> > Egads, I remember reading that article in my high school
> library when it was first published.
> >
> > ObSdiyContent:  it must have been about the same time
> PAiA's 2700 was in Radio-Electronics...
>
> Yep, I was a subscriber when I was in high school. I really
> wanted to build one. It only took me a couple of decades to
> get around to it.
>
> The dog-eared magazine is in the next room right now. The pdf
> article on my blog is a recreation of the original, OCRed and
> reset in the original typeface.
>
>
> Terry Bowman, KA4HJH
> "The Mac Doctor"
>
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-- 

Quincas Moreira
Test Pilot at VBrazil Modular

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