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Power and Ground signals and Routing

Power and Ground signals and Routing

2006-03-11 by kilocycles

At some point in our discusssions on Eagle this week, and this
probably applies to other CAD programs as well, not routing power and
grounds was mentioned. On several boards, I've not used the supply
device/symbol to tie the power connections together, as it adds
considerably to the complexity of routing. I've just added solder pad
components to power connection points, and I've run multiple power
wires to the board, using the supply signal/device only once, with
solpads added as needed at both the supply and supplied component
networks.

I could obviously do the same thing with signal grounds, but there
would be several orders of magnitude more complexity in wiring by
doing that.

I've done some boards where the last step was adding the grounds to
the schematic, after all components were added, making it easier to
route the board manually as I added components, not having to deal
with gnd in the ratsnest until the end.

Unless I missed something, I think I read in one of the recent posts
that grounds don't have to be routed??? They do have to be connected
on the schematic to, say, a resistor, capacitor, etc. otherwise there
will be an electrical rules check error for an unconnected pin.

Can someone clarify this?

Thanks,
Ted

Re: [Homebrew_PCBs] Power and Ground signals and Routing

2006-03-11 by Leon Heller

----- Original Message -----
From: "kilocycles" <kilocycles@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Saturday, March 11, 2006 2:19 AM
Subject: [Homebrew_PCBs] Power and Ground signals and Routing


> At some point in our discusssions on Eagle this week, and this
> probably applies to other CAD programs as well, not routing power and
> grounds was mentioned. On several boards, I've not used the supply
> device/symbol to tie the power connections together, as it adds
> considerably to the complexity of routing. I've just added solder pad
> components to power connection points, and I've run multiple power
> wires to the board, using the supply signal/device only once, with
> solpads added as needed at both the supply and supplied component
> networks.
>
> I could obviously do the same thing with signal grounds, but there
> would be several orders of magnitude more complexity in wiring by
> doing that.
>
> I've done some boards where the last step was adding the grounds to
> the schematic, after all components were added, making it easier to
> route the board manually as I added components, not having to deal
> with gnd in the ratsnest until the end.
>
> Unless I missed something, I think I read in one of the recent posts
> that grounds don't have to be routed??? They do have to be connected
> on the schematic to, say, a resistor, capacitor, etc. otherwise there
> will be an electrical rules check error for an unconnected pin.
>
> Can someone clarify this?

I always route the power and ground tracks first, as they are the most
critical ones.

Leon

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Re: [Homebrew_PCBs] Power and Ground signals and Routing

2006-03-11 by Stefan Trethan

No you still need to route ground.
You probably read it in conjunction with ground planes. If you have a
multilayer board and one layer is left a solid area as ground plane you
don't need to route much, since all ground pins simply tie into that
ground plane with no traces needed.

But when you don't have a dedicated ground plane you must of course route
it. I tend to route them early because ground path is important in many
circuits.


About not seeing them in the ratsnest, i understand what you mean. Having
the supply links makes it harder to see signal paths and identify which
components must be close at the positioning stage (because power chains
can often be random order).
In my software i can switch signals on and off for ratsnest display, maybe
eagle has a similar option. Some layout tools allow colored ratsnests,
which is a huge plus.

ST


On Sat, 11 Mar 2006 03:19:38 +0100, kilocycles <kilocycles@...>
wrote:

> At some point in our discusssions on Eagle this week, and this
>
> probably applies to other CAD programs as well, not routing power and
>
> grounds was mentioned. On several boards, I've not used the supply
>
> device/symbol to tie the power connections together, as it adds
>
> considerably to the complexity of routing. I've just added solder pad
>
> components to power connection points, and I've run multiple power
>
> wires to the board, using the supply signal/device only once, with
>
> solpads added as needed at both the supply and supplied component
>
> networks.
>
>
> I could obviously do the same thing with signal grounds, but there
>
> would be several orders of magnitude more complexity in wiring by
>
> doing that.
>
>
> I've done some boards where the last step was adding the grounds to
>
> the schematic, after all components were added, making it easier to
>
> route the board manually as I added components, not having to deal
>
> with gnd in the ratsnest until the end.
>
>
> Unless I missed something, I think I read in one of the recent posts
>
> that grounds don't have to be routed??? They do have to be connected
>
> on the schematic to, say, a resistor, capacitor, etc. otherwise there
>
> will be an electrical rules check error for an unconnected pin.
>
>
> Can someone clarify this?
>
>
> Thanks,
>
> Ted

Re: Power and Ground signals and Routing

2006-03-11 by Richard

""I always route the power and ground tracks first, as they are
the most critical ones.

Leon """
------------------

took the words right out of my mouth... <g>

Richard

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Re: Power and Ground signals and Routing

2006-03-12 by kilocycles

I disagree. For RF analog circuits, which is 90% of the stuff that I
do, I approach it as if I were building "ugly" style, where I know
that most of the board is going to be ground plane anyway. For the
supplies, a few leads (2 or 3) going directly to the connection points
in the circuit from the power jack, or in many cases, the 78L08 as
well, in my opinion is preferable to having a torturous route for the
RF traces.

Once I have everything routed and poured, I evaluate the board to see
if it looks like there might be potential issues with unwanted coupling.

Ted

--- In Homebrew_PCBs@yahoogroups.com, Richard <metal@...> wrote:
>
>
> ""I always route the power and ground tracks first, as they are
> the most critical ones.
>
> Leon """
> ------------------
>
> took the words right out of my mouth... <g>
>
> Richard
>
> --
> ============================
> Please do NOT add or "subscribe" my name to ANY lists/databases.
>

Scaling problems using laser printer

2006-03-12 by Jose Fuentes

I'm experiencing scaling problems with my laser
printer. I've confirmed that this is a printer
problem and is not software related. When I try to
print a board of 285mm what is printed is a 286.5mm
board. Does any of you experienced a similar problem?

Regards

Jose





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Re: [Homebrew_PCBs] Scaling problems using laser printer

2006-03-12 by Leon Heller

----- Original Message -----
From: "Jose Fuentes" <josecarlosfuentes@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, March 12, 2006 5:28 AM
Subject: [Homebrew_PCBs] Scaling problems using laser printer


> I'm experiencing scaling problems with my laser
> printer. I've confirmed that this is a printer
> problem and is not software related. When I try to
> print a board of 285mm what is printed is a 286.5mm
> board. Does any of you experienced a similar problem?

That usually happens with laser printers, the printout is stretched in the
direction of the paper path. The EasyPC software I used to use had a
correction factor for printing which got over the problem. With smaller
boards it usually doesn't matter, anyway.

Leon

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Re: Scaling problems using laser printer

2006-03-12 by lcdpublishing

Yup, Laser printers do scale output slightly - copy machines do
this as well. Generally it does not make much difference with PCBs
(at least the ones I have made so far).

chris



--- In Homebrew_PCBs@yahoogroups.com, Jose Fuentes
<josecarlosfuentes@...> wrote:
>
> I'm experiencing scaling problems with my laser
> printer. I've confirmed that this is a printer
> problem and is not software related. When I try to
> print a board of 285mm what is printed is a 286.5mm
> board. Does any of you experienced a similar problem?
>
> Regards
>
> Jose
>
>
>
>
>
> ___________________________________________________________
> 1GB gratis, Antivirus y Antispam
> Correo Yahoo!, el mejor correo web del mundo
> http://correo.yahoo.com.ar
>

Re: Scaling problems using laser printer

2006-03-12 by derekhawkins

>Does any of you experienced a similar problem?

Had to switch from laser to inkjet artwork when I went to CNC
drilling. Still have to compensate for dimensional errors in the
Excellon files but they are less and more linear with the inkjet.

--- In Homebrew_PCBs@yahoogroups.com, Jose Fuentes
<josecarlosfuentes@...> wrote:
>
> I'm experiencing scaling problems with my laser
> printer. I've confirmed that this is a printer
> problem and is not software related. When I try to
> print a board of 285mm what is printed is a 286.5mm
> board. Does any of you experienced a similar problem?
>
> Regards
>
> Jose
>
>
>
>
>
> ___________________________________________________________
> 1GB gratis, Antivirus y Antispam
> Correo Yahoo!, el mejor correo web del mundo
> http://correo.yahoo.com.ar
>

Re: [Homebrew_PCBs] Re: Scaling problems using laser printer

2006-03-12 by Stefan Trethan

On Sun, 12 Mar 2006 13:44:03 +0100, lcdpublishing
<lcdpublishing@...> wrote:

> Yup, Laser printers do scale output slightly - copy machines do
>
> this as well. Generally it does not make much difference with PCBs
>
> (at least the ones I have made so far).
>
>
> chris
>


If your software does not support correction factors you can use irfanview
(freeware) to resize a image of the layout and print it then.
Remember to align your printer beforehand according to the service manual
if you notice skew of any sort.

ST

Re: Scaling problems using laser printer

2006-03-12 by Len Warner

On Sun, 12 Mar 2006 02:28:01 -0300 (ART), Jose Fuentes wrote:

>I'm experiencing scaling problems with my laser printer.<snip>
>Does any of you experienced a similar problem?

As others have commented, this is a common problem.
If your artwork is in a .pdf (Adobe Acrobat) file, I believe
it is possible to edit in a scaling factor - and in PostScript
it is possible to do almost anything one could wish.

Otherwise, I would second the recommendation of IrfanView
if necessary** - a wonderful little tool.

** Your error is 1.5mm in 285, about 0.53%. I would have thought
that only just enough to be annoying for mounting holes and
panel alignment, though it would mean double-sided artwork
would need the same orientation of stretch.


Regards, LenW
--
Please trim quotes to minimum for context, then
reply below, or interleave point-by-point replies.

Re: Scaling problems using laser printer

2006-03-12 by derekhawkins

>** Your error is 1.5mm in 285, about 0.53%. I would have thought
>that only just enough to be annoying for mounting holes and
>panel alignment

It really depends on what he's doing. For CNC drilling a 60 thou error
would be intolerable. Not only would his holes be way off but he would
miss via pads completely. While linear compensation can be helpful for
dimensional errors that aren't entirely linear, laser artwork is a
real PIA when it comes to CNC work. You're better off using an inkjet.


--- In Homebrew_PCBs@yahoogroups.com, Len Warner <yahoo@...> wrote:
>