Noobish question - how do I exclude components from a PCB?

D

DmitryB

Guest
So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.
 
On Jun 8, 1:37 am, DmitryB <combust...@gmail.com> wrote:
So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.
Click to expand...
Don't put them there.
 
On Jun 8, 1:39 am, Richard Henry <pomer...@hotmail.com> wrote:
On Jun 8, 1:37 am, DmitryB <combust...@gmail.com> wrote:

So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.

Don't put them there.
Click to expand...
That's an obvious workaround. What if I do want to put them there.
They contain valuable information after all - grounding, rating of the
fuse, DPDT-ness of the switch, wire colors of the transformer's
windings. Can't I use the same schematic for PCB and assembly?
 
On Jun 8, 1:37 am, DmitryB <combust...@gmail.com> wrote:
So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.
Click to expand...
It just occured to me that I probably wasn't clear enough on what I
want to accomplish. I don't want to exclude them from the schematic
per se. Just from the PCB. In other words, I'm trying to find a way to
mark some of the components as "don't even bother placing pads for
these".
 
On 8 Jun, 10:33, DmitryB <combust...@gmail.com> wrote:
On Jun 8, 1:37 am, DmitryB <combust...@gmail.com> wrote:

So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.

It just occured to me that I probably wasn't clear enough on what I
want to accomplish. I don't want to exclude them from the schematic
per se. Just from the PCB. In other words, I'm trying to find a way to
mark some of the components as "don't even bother placing pads for
these".
Click to expand...

Put them in a separate schematic?

Leon
 
The question is, how do I exclude the plug, switch and the fuse from
the schematic.


It just occured to me that I probably wasn't clear enough on what I
want to accomplish. I don't want to exclude them from the schematic
per se. Just from the PCB. In other words, I'm trying to find a way to
mark some of the components as "don't even bother placing pads for
these".
Click to expand...
Create new PCB componment shapes that will appear as patterns of holes
on your PCB. Link these shapes to the schematic symbols.

You will need to place through-hole pads for these, as otherwise it will
not be easy to run the wires from those parts to the PCB.
 
On Jun 8, 4:33 am, DmitryB <combust...@gmail.com> wrote:
On Jun 8, 1:37 am, DmitryB <combust...@gmail.com> wrote:

So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.

It just occured to me that I probably wasn't clear enough on what I
want to accomplish. I don't want to exclude them from the schematic
per se. Just from the PCB. In other words, I'm trying to find a way to
mark some of the components as "don't even bother placing pads for
these".
Click to expand...
This problem occurs all the time with any CAD tool. You need to create
your symbol in such a way that it is only a schematic symbol and it
doesn't "forward" to the PCB, but still shows up on the BOM.
I don't know how to do this in OrCAD. The problem in reverse is test
pads, they show up on the schematic, thus are a "part", but are not
purchased, they are pads on the PCB, so they aren't on the BOM.
Maybe if you look around the documentation for test points, it will
show you the properties you need to play with.
 
On Sun, 8 Jun 2008 01:37:24 -0700 (PDT), DmitryB
<combustion@gmail.com> wrote:

So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.
Click to expand...
A CAD system I used long ago allowed you to put a "no-op" parameter on
a schematic part that you didn't want on the board.

Failing that option, a couple of solutions come to mind:

1. Draw two schematics - one with the switch, fuse, and transformer
and any other off-board parts, and a box to represent the board. The
second schematic would show only the parts on the board.

2. Draw the whole thing as one schematic, and just ignore the
off-board components when laying out the board - you will get DRC
errors, but they can be ignored. You might want to initially place
the off-board components on the PCB layout (but outside the board
boundary) so that the "update PCB from schematic" function won't keep
placing them on the board as you work. You can delete the off-board
parts before creating the Gerbers.


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca
 
On 8 Jun, 09:37, DmitryB <combust...@gmail.com> wrote:
So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.
Click to expand...
I'd forgotten this, but the Pulsonix software I use lets me create
schematic only parts. These may be added to a schematic and won't
appear on the PCB. They actually appear on the parts list, which is
useful.

You might be able to do something similar.

Leon
 
On Sun, 8 Jun 2008 07:53:17 -0700 (PDT), a7yvm109gf5d1@netzero.com wrote:

On Jun 8, 4:33 am, DmitryB <combust...@gmail.com> wrote:
On Jun 8, 1:37 am, DmitryB <combust...@gmail.com> wrote:

So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.

It just occured to me that I probably wasn't clear enough on what I
want to accomplish. I don't want to exclude them from the schematic
per se. Just from the PCB. In other words, I'm trying to find a way to
mark some of the components as "don't even bother placing pads for
these".

This problem occurs all the time with any CAD tool. You need to create
your symbol in such a way that it is only a schematic symbol and it
doesn't "forward" to the PCB, but still shows up on the BOM.
I don't know how to do this in OrCAD. The problem in reverse is test
pads, they show up on the schematic, thus are a "part", but are not
purchased, they are pads on the PCB, so they aren't on the BOM.
Maybe if you look around the documentation for test points, it will
show you the properties you need to play with.
Click to expand...

Just use Tango to make the PCB layout, and you can place things however
you like... ALL by hand. A power supply isn't so complicated that you
would even need checking routines at all.
 
Peter Bennett wrote:
On Sun, 8 Jun 2008 01:37:24 -0700 (PDT), DmitryB
combustion@gmail.com> wrote:

So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.

A CAD system I used long ago allowed you to put a "no-op" parameter on
a schematic part that you didn't want on the board.

Failing that option, a couple of solutions come to mind:

1. Draw two schematics - one with the switch, fuse, and transformer
and any other off-board parts, and a box to represent the board. The
second schematic would show only the parts on the board.

2. Draw the whole thing as one schematic, and just ignore the
off-board components when laying out the board - you will get DRC
errors, but they can be ignored. You might want to initially place
the off-board components on the PCB layout (but outside the board
boundary) so that the "update PCB from schematic" function won't keep
placing them on the board as you work. You can delete the off-board
parts before creating the Gerbers.


I have always done choice (1). It makes it much easier to separate the
Click to expand...
board assembly task from the system assembly task, as you can make each
of these tasks boil down to "make these here electronics match that
there schematic".

Service personnel may not see the 'system view' as easily, but at least
they won't be wondering what's on the board and what isn't.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
 
DmitryB wrote:
On Jun 8, 1:37 am, DmitryB <combust...@gmail.com> wrote:
So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.

It just occured to me that I probably wasn't clear enough on what I
want to accomplish. I don't want to exclude them from the schematic
per se. Just from the PCB. In other words, I'm trying to find a way to
mark some of the components as "don't even bother placing pads for
these".
Click to expand...
Are you using a particular CAD or board layout program? That will drive
the details on how to do what you want.

If its a human being interpreting the schematic, all you need to do is
to enclose the parts of the schematic that will be mounted on the board
with a decent looking border. In addition, you should use appropriate
symbols for the connections to the board. People are pretty good at
figuring these things out (unless you get a moron to build your boards).

--
Paul Hovnanian paul@hovnanian.com
-----------------------------------------------------------------------
Have gnu, will travel.
 
DmitryB wrote:

So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.
Click to expand...
You mean from the PCB ?

Delete them and generate a wiring loom schematic with only those parts
(and connectors).

Graham
 
DmitryB wrote:

What if I do want to put them there.
Click to expand...
Don't.

They contain valuable information after all - grounding, rating of the
fuse, DPDT-ness of the switch, wire colors of the transformer's
windings. Can't I use the same schematic for PCB and assembly?
Click to expand...
Use a separate schematic for the wiring harness.

Graham
 
mw wrote:

The question is, how do I exclude the plug, switch and the fuse from
the schematic.

It just occured to me that I probably wasn't clear enough on what I
want to accomplish. I don't want to exclude them from the schematic
per se. Just from the PCB. In other words, I'm trying to find a way to
mark some of the components as "don't even bother placing pads for
these".

Create new PCB componment shapes that will appear as patterns of holes
on your PCB. Link these shapes to the schematic symbols.

You will need to place through-hole pads for these, as otherwise it will
not be easy to run the wires from those parts to the PCB.
Click to expand...
You're quite MAD.

Graham
 
Peter Bennett wrote:

2. Draw the whole thing as one schematic
Click to expand...
NOOOOOOO !

Draw as it as several schematics that actually physically represent the way
you build the product.

Jeez !

Graham
 
On Jun 8, 4:37 am, DmitryB <combust...@gmail.com> wrote:
So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.
Click to expand...
I don't understand. Why not create a schematic without the parts you
don't want.
Then create the PCB from that schematic.. and if all goes well add to
the original schematic
the parts that are not going to go on the pcb.

shortT
 
shortT wrote:
On Jun 8, 4:37 am, DmitryB <combust...@gmail.com> wrote:
So here's the problem. I have a power supply schematic I need to
create a PCB for. My CAD is ye olde OrCAD 9.2. The power supply
includes a rather substantial transformer, and the primary of that
transformer is connected to the mains through a fuse and a switch,
both of which are in the schematic. None of this stuff will be mounted
on the PCB.

The question is, how do I exclude the plug, switch and the fuse from
the schematic.

I don't understand. Why not create a schematic without the parts you
don't want.
Then create the PCB from that schematic.. and if all goes well add to
the original schematic
the parts that are not going to go on the pcb.

shortT
Click to expand...
Optimally, one would have a tool (CAD) that would allow the creation and
maintenance of a single system schematic which has an assembly or board
view. One attribute of each component would be the assembly,
subassembly, or board to which it belongs.

For manufacturing purposes, assembly views could be generated tailored
to the task at hand. For design, simulation, and maintenance,
system-wide schematics, netlists, etc. can be generated.

Back in my days at the lazy B, one of the primary contributors to wiring
configuration errors was the practice of maintaining multiple views of
each system in separate CAD systems. Even with "perfect" import/export
functions (and none were really perfect), the time delay involved in
propagating a design change through the system would almost guarantee
that aircraft were being built to multiple versions of the engineering
data.

--
Paul Hovnanian paul@hovnanian.com
-----------------------------------------------------------------------
Have gnu, will travel.
 
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