[Coco] WAS new mylars, NOW PCB Design

[Zippster]

Hi Salvador (and all),

I certainly understand just wanting to use the autorouter when you’re starting out,
there’s just so much to learn, it’s too much to tackle everything at once.  A few things I’ve 
learned (and I’m still learning every day, there’s an endless amount to learn in electronics design).

Once you get familiar with your CAD software, I think a good way of starting in on manual
routing is to concentrate on the power distribution at first.  

Run power supplies to all ICs and circuits first, don’t worry about ground lines during this first step, 
use a ground plane and ground should be available almost everywhere on your board.  I wouldn't worry
about a power plane on 2-layer boards, there won’t be any room for one, and the ground plane is
more important.

Then decouple all IC’s properly.  One lead from the decoupling cap as close to the positive power 
supply pin on the IC as is reasonable, the other lead into ground plane on the bottom of the board
(where the ground pin on the IC will also go).

Try to keep all traces on the top layer, going to the bottom copper layer only when necessary, to 
preserve your ground plane.  When running traces on the bottom layer be sure to leave pathways through
the ground plane as open as possible, to avoid breaking it up.  Try to keep in mind where the ground
connection to your board is and leave direct paths (straight-line more or less) to it when you have a choice.

The part about keeping traces on the top layer as much as possible becomes even more important when you
move to SMT devices later, where you can’t naturally switch layers at any connection.  Your via count goes 
through the roof if you don’t learn to keep most of your traces on the top layer.  Part placement is critical to this.

One good way to start working on efficient part placement is to begin while drawing your schematic.  Lay out
your schematic with the final board in mind, keeping connections as direct as possible with minimal crossings
(this is layer switching when you get to board layout).


One other important CAD tip.  Get proficient in drawing up parts from data sheet specs early, and don’t hesitate
to draw up a part rather than search for one that’s already done.  You’ll get a better part for your purposes,
and begin to build up a library of parts that you’ll use many times in your designs.  You can optimize them for
assembly of the final boards as well.


This is all just my opinion of course, everyone has their own way of working.

I think it’s great that we use the resource of this group to learn from each other and make our hobby even better.
I’m happy to discuss this stuff anytime on the list or in off-list email.

It’s a lot of fun building things, isn’t it?  :)

- Ed
 


> On Aug 11, 2015, at 11:14 AM, Salvador Garcia <ssalvadorgarcia at netscape.net> wrote:
> 
> 
> 
> Anyway, nearly irrelevant side-track over… 
> :)
> 
> - Ed
> 
> 
> Actually this deserves its own thread. I think it is important to discuss these topics as this might spur interest in developing more hardware for the CoCo and other vintage systems. I am getting started on PCB design. At this time I am in the "I don't care" stage and let the autorouter do the work for me. I tweaked the ground trace to create a plane, but definitely know the value of doing the routing by hand. 
> 
> 
> I would have been happy to offer Kip my help with his 3 or 4 projects, taking the schematic and managing the PCB design and logistics, but I do not have the skill as of yet. A transfer of knowledge within our community means that we could further organize ourselves to motivate and support further innovations based on vintage technology.
> 
> 
> Salvador
> 
> 




> 
> From: Zippster <zippster278 at gmail.com>
> Subject: Re: [Coco] new mylars
> Date: August 11, 2015 at 10:44:27 AM CDT
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> 
> A side note to laying out circuits with Eagle or similar and using the autorouter.
> If there was one piece of advice I’d give on autorouters, it would be to pretend they
> don’t exist.
> 
> It does take a long time to lay things out manually, but it’s well worth it.
> Even a well-designed circuit with good component placement on the board gets
> very meh when the autorouter is applied to it.
> 
> Are autorouted boards functional?  Yes, usually.  They are also terribly inefficient in terms of
> vias and proper power distribution (proper ground plane especially).  Also, they destroy layout
> aesthetics, which might not matter to some, but I think is important.
> 
> Anyway, nearly irrelevant side-track over…  :)
> 
> - Ed
>