In a message dated 2004-10-26 07:49:22 AM Eastern Daylight Time, 
[EMAIL PROTECTED] writes:


> I have three small PCB and I want to merge them to one PCB in order to 
> decrease the cost. I am thinking about two method as following but either 
> has demerit. Could you please give me some advice?
> 
> (1) Design the three PCB in one project. But the designator name cannot 
> repeat so I must name the parts of the1st PCB from "U1" to "U5" then the 2nd 
> 
> PCB from U6 to U10 (for example) and so on.

At a minimum, keep some separation between the projects. That is, use a 
separate schematic page for each project, and number all of page 1 "U101, 
U102,....", page 2 "U201, U202..." etc. There's no penalty I've ever found for 
skipping 
numbers, and you can then insert parts without renumbering everything; 
indeed, I have long used a system where particular sections of a project get 
specific hundreds, and subsections get a whole decade. Many of my clients prefer that 
the hundreds digit match the page number, just for ease in finding a 
reference later. This automatically avoids any conflicts.

You'll also need to watch out for common net names, such as gnd and vcc. 
Prefix or suffix those with a page number as well. If you use a suffix, it's easy 
to look at the netlist file and see that you got things sorted out correctly.

> 
> (2) Design the three PCB in three projects. But when I output the three 
> gerber data files I cannot merge them into one gerber data file.
> 

I believe Camtastic has the capability to merge gerbers. Alternatively, you 
can bet that your PCB house can do so, because they do that routinely to get 
the best yield from the raw materials. But they probably change extra for that 
merge, which defeats your purpose in doing so. You might want to ask them if 
you can get a discount by running all three boards together; it might still be 
the cheapest way to get the job done in the long run, and you don't end up with 
artifacts that don't belong in your designs.

Steve Hendrix
 
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