Homebrew PCBs

Hi,

I've been using Eagle for my PCBs, mainly on the strengths of its
above-average user interface, the good component libraries (made better
by user contributions), but especially its autorouter.

The autorouter is a pain, but gets the job done. Even if sometimes I
need to tweak some of the parameters, and manually move traces around a
bit after the job's done.

For me, the autorouter is a $deity$-send. I just don't have the patience
to lay out traces manually.

Some questions here:
 - do people here consider it lame to use autorouting?
 - are there any other free PCB design progs that have autorouting?
 - can eagle (or any other free progs) do auto-placement?
 - is Eagle the best of the free PCB design progs?

Cheers
David

On Fri, 12 Jan 2007 21:56:58 +0100, David McNab <rebirth@...>  
wrote:

> Some questions here:
>  - do people here consider it lame to use autorouting?

YES! YES! and YES!
It's almost as lame as thinking the component libraries that come with a  
software will be of much use.

>  - are there any other free PCB design progs that have autorouting?

Yes, but autorouting is lame in all of them.

>  - can eagle (or any other free progs) do auto-placement?

Some may do , but autoplacement is hundred times crappier than autorouting  
because placement is hundred times more important than routing.

My opinion is (i repeat - MY OPINION, as in "MY" and "OPINION", just to  
make that clear to those people not liking what i say)- my opinion is that  
if you use an autorouter you shouldn't even be making boards. If you don't  
have the patience to give the task the attention it deserves you are not  
worthy of doing it. In short, i consider you a lazy git if you use an  
autorouter, but at least i have the thought to console me that you will  
never ever have the satisfaction of producing a decent board this way.

I can't stand badly routed boards, and i have yet to see an autorouter  
that can do an acceptable job. 99% of layout is parts placement, once i'm  
finished placing parts it is no work at all to route a board, i have no  
need at all for an autorouter then which will at best make a mess of my  
hard-won parts placement. I consider layout an art (of the real kind, not  
modern art), and i won't have to say something good about autorouters  
unless i see one do a decent job, which so far i have not.

I can see some use for autorouters (very high quality ones), with heavy  
cleanup and constant human intervention and control, but even then the  
result will not be fantastic. When working on large circuits they may  
potentially be an aid to some. I won't go as far as calling them useful  
though.

So, that was _my_ opinion, and i can't put it into strong enough words.  
Other people have _other_ opinions.

ST

----- Original Message ----- 

From: David McNab
To: Homebrew_PCBs@yahoogroups.com
Sent: Friday, January 12, 2007 8:56 PM
Subject: [Homebrew_PCBs] Autorouting and auto-placement


Hi,

I've been using Eagle for my PCBs, mainly on the strengths of its
above-average user interface, the good component libraries (made better
by user contributions), but especially its autorouter.

The autorouter is a pain, but gets the job done. Even if sometimes I
need to tweak some of the parameters, and manually move traces around a
bit after the job's done.

For me, the autorouter is a $deity$-send. I just don't have the patience
to lay out traces manually.

Some questions here:
- do people here consider it lame to use autorouting?
- are there any other free PCB design progs that have autorouting?
- can eagle (or any other free progs) do auto-placement?
- is Eagle the best of the free PCB design progs?

--------------------------------------

I sometimes use the Pulsonix autorouter, it is one of the better ones. I 
always route ground, power and other critical nets manually, of course. I 
don't bother with auto-placement.

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND transceiver
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller

I am using autorouter for complex boards. It   would be nightmare to 
manually route something like high speed 32 bit databus and preserve 
signal integrity... I have another opinion: since 4 layer PCBs are 
almost as cheap as 2 layer few years ago, I am using 4 layers for higher 
densitiy PCBs. Just put power planes in the mid layers and let the 
autorouter do the boring job...

M.



David McNab pravi:

>
> Hi,
>
> I've been using Eagle for my PCBs, mainly on the strengths of its
> above-average user interface, the good component libraries (made better
> by user contributions) , but especially its autorouter.
>
> The autorouter is a pain, but gets the job done. Even if sometimes I
> need to tweak some of the parameters, and manually move traces around a
> bit after the job's done.
>
> For me, the autorouter is a $deity$-send. I just don't have the patience
> to lay out traces manually.
>
> Some questions here:
> - do people here consider it lame to use autorouting?
> - are there any other free PCB design progs that have autorouting?
> - can eagle (or any other free progs) do auto-placement?
> - is Eagle the best of the free PCB design progs?
>
> Cheers
> David
>
>

David McNab <rebirth@...> writes:
>  - do people here consider it lame to use autorouting?

No.  It's lame to *rely* on autorouting, because you (as the designer)
should know more about the signals than the autorouter.  Autorouting
is a tool, know when to use it and when to hand-route.

>  - are there any other free PCB design progs that have autorouting?

gEDA's PCB has autoplace and autoroute.  I rarely use them, relying on
my own placement and routing skills, although others think they're a
$deity-send.  PCB also has an optimizer to clean up after the
autorouter (it can clean up hand-routed traces too).  It also has auto
miter and I have an auto teardrop plugin.

>  - can eagle (or any other free progs) do auto-placement?

PCB can do autoplacement (two kinds, true autoplace and a dumb
"disperse elements" option for hand-placing).  I use the dumb one.

>  - is Eagle the best of the free PCB design progs?

Eagle isn't, technically, free.  The crippled "demo" version has
limitations, and the fully capable versions cost money.  No version of
Eagle is licensed with an open source license.

And "best" is VERY subjective.

> -----Original Message-----
> From: Stefan Trethan [mailto:stefan_trethan@...]
>
>
> I can't stand badly routed boards, and i have yet to see an autorouter
> that can do an acceptable job. 99% of layout is parts placement,
> once i'm
> finished placing parts it is no work at all to route a board, i have no
> need at all for an autorouter then which will at best make a mess of my
> hard-won parts placement. I consider layout an art (of the real
> kind, not
> modern art), and i won't have to say something good about autorouters
> unless i see one do a decent job, which so far i have not.
>

I have to say I agree with Stefan.

I like my boards to look neat. Because the majority of my boards are for
Audio and Video use, layout is VERY important and one board that I took a
long time designing was single sided with only 3 links.

When my PCB package (Proteus) was upgraded to the next level I decided to
see what the Autorouter would make of the board. I left all the components
in place but ripped up all the tracks. The Autorouter FAILED to route the
board even as double sided PTH despite me having boards already made that
were single sided with just 3 short (0.2in) links

I have tried various time to see what the autorouter would do on a board and
have yet to find any of its eforts to be acceptable. It usually does get
100% routing but with tracks going in and out of everywhere. I dread to
think what sort of crosstalk would result on the finished boards :(

AUTO PLACEMENT was even worse, it just seemed to cram as many components as
it could into the smallest possible space despite the board having quite a
lot of space.

Regards

Keith

On Fri, 2007-01-12 at 22:47 +0100, Stefan Trethan wrote:
> >  - do people here consider it lame to use autorouting?

> YES! YES! and YES!
> It's almost as lame as thinking the component libraries that come with a  
> software will be of much use.
...
> my opinion is that  
> if you use an autorouter you shouldn't even be making boards.

I got into programming in the mid 1970s. Back then, there were those who
screamed that anyone who uses a C compiler shouldn't be writing
software.

There were even those who considered assemblers to be lame, and that
anyone who couldn't/wouldn't memorise all the hex/binary opcodes,
addressing modes and argument fields, and calculate jump displacements
mentally, weren't good enough to program.

There'd be those of us making PCB boards for whom a depth of electronic
knowledge is just a means to an end (that of getting a piece of custom
hardware working to a level good enough for small volume sales, without
shelling out $thousands to a hardware dev), and there'd be those for
whom deep electronic knowledge is the end in itself. I belong to the
former group, and I by no means expect this position to command any
respect in this list.

It's all a matter of relativity. You could call it 'lame' to purchase
blank copper board from electronics stores instead of making one's own.
You could even call it lame to use bought copper, instead of
mining/smelting your own.

Back to the point - if I can get Eagle's autorouter to reach 100% on a
single-sided board without many convoluted trace routes, I'm happy. Time
saved. If/when my products go larger scale commercial, I can outsource
the one-time task of designing a better PCB, because at that stage I'll
be able to afford it. A specialised h/w dev will do it all in SMD, and
oversee the manufacturing.

Cheers
David

--- In Homebrew_PCBs@yahoogroups.com, David McNab <rebirth@...> wrote:
>
> Hi,
> 
> I've been using Eagle for my PCBs, mainly on the strengths of its
> above-average user interface, the good component libraries (made better
> by user contributions), but especially its autorouter.
> 
> The autorouter is a pain, but gets the job done. Even if sometimes I
> need to tweak some of the parameters, and manually move traces around a
> bit after the job's done.


I like the auto-router in WinQCAD.  I usually place chips,
auto-router, move things, re-router, move other things, and so on
until I get the board about where everything will fit.

then I go in an lay out the power lines, and any guard rings or any
other odd feature needed.

I place any important traces and at some point, I run the auto-router
to let it fill in the other stuff.

Then I go back and tweek it as needed.  usualy there is a lot needed.

But for the help of the autorouter in the early layout, it would be
much harder to find some very useful layouts.

Dave