Please help with PCB layout

[Owen Lawrence]

Hi. I'm trying to design a circuit using a PIC and some home-grown
H-bridges (i.e. 4 transistors each) to drive a bipolar stepper motor. There
are few other things on the board, but my question is about how I should
position the components. I'm using Eagle, and when I autoroute, it finds
most paths it needs to, but the result is ugly. There are lines going under
components all over the place, lines inbetween the pins of the IC, etc.
Since I want to etch this board myself I'm not confident of the results if
so many lines have to be close to each other.

Do you have any advice about how I should do the layout? I started with
the ratsnest view, and positioned components roughly where I thought they'd
cause the least amount of positional interference. But now I've been
fiddling with it for a couple of evenings, and while I'm making progress,
I'm not sure this is the best way. I honestly thought I'd have it finished
long ago.

How much time does one usually spend working on the board layout, after
the schematic is designed? I'm still adding things to the design. Also,
what do you usually do with V+ and V-? I think these are the sources of
many of the strange routes I'm getting, since so many components have to
attach to them. Is there a layout technique you use?

Thanks for your help.

- Owen -

--
mailto: owen@nospam.iosphere.net
//http:www.iosphere.net/~owen




-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 80,000 Newsgroups - 16 Different Servers! =-----

 

[Eugene Rosenzweig]

I find that routing a design takes the longest unless you autoroute and
trust the results. However I practically always ended up doing the routing
manually since the autorouting results are quite often poor or/and
inefficient (like using two layers when one suffices). I think practice
makes it perfect, the more you do the layout and routing the more you get
the feel for placement of the components, etc... What could work also is
autoroute then ripup and manual route of the really bad/silly tracks.

Eugene.

 

[Owen Lawrence]

trust the results. However I practically always ended up doing the routing
manually since the autorouting results are quite often poor or/and
inefficient (like using two layers when one suffices). I think practice

I have forced it to do only one layer.

makes it perfect, the more you do the layout and routing the more you get
the feel for placement of the components, etc... What could work also is
autoroute then ripup and manual route of the really bad/silly tracks.

That's the direction I'm leaning to. I've already done a bit of manual
rerouting after the autoroute, and now believe I'm quite capable of making
it look much better. As long as I don't have to redo most of the board, I
can live with this.

It seems that my own experience is consistent with others', and there is
no free lunch. Therefore, my new intention is to practice, so I can get
enjoyably good at this.

I also intend to finish my design. I wanted to do some routing at an
intermediate stage before things got too complicated to handle, and I'm glad
I did.

Thanks for your advice.

- Owen -




-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 80,000 Newsgroups - 16 Different Servers! =-----

 

[Rich Grise]

"Owen Lawrence" <owen@nospam.iosphere.net> wrote in message news:<3f1fd3f1_3@corp.newsgroups.com>...

trust the results. However I practically always ended up doing the routing
manually since the autorouting results are quite often poor or/and
inefficient (like using two layers when one suffices). I think practice

I have forced it to do only one layer.

makes it perfect, the more you do the layout and routing the more you get
the feel for placement of the components, etc... What could work also is
autoroute then ripup and manual route of the really bad/silly tracks.

That's the direction I'm leaning to. I've already done a bit of manual
rerouting after the autoroute, and now believe I'm quite capable of making
it look much better. As long as I don't have to redo most of the board, I
can live with this.

It seems that my own experience is consistent with others', and there is
no free lunch. Therefore, my new intention is to practice, so I can get
enjoyably good at this.

I also intend to finish my design. I wanted to do some routing at an
intermediate stage before things got too complicated to handle, and I'm glad
I did.

Thanks for your advice.

- Owen -


You didn't say if you're doing one layer or two, but I've done manual

layouts, 2-sided, and even making boards by hand at home, it's not that
much worse than single-sided. I took the tape-up to the photo guy, and
it was no problem shooting it 6-up, registered. Then I just scotch(r)
taped them together and slid the board between them. As far as style,
I usually start with ground and power on the component side, and do
as much of the signal stuff as I can on the other side. You don't need
to make plated-thru holes, since you can use a component lead for a
via, and you can make stand-alone vias with a tiny piece of wire.

Have Fun!
Rich