Homebrew PCBs

On Sat, 18 Mar 2006 19:41:25 +0100, Alan Marconett <KM6VV@...> wrote:

> Hi Ted,
>
>
> I saw parts with hidden supply pins get connected, but trouble is, there
>
> are many ways to call pins, VDD, VCC,  GND, VSS.  And Eagle doesn't seem
>
> to have a way to "alias" them together when they should be.
>
>
> Did you notice the GND@1 and GND@2 convention?  you might try the @
>
> convention to tie your pins together.
>

Hidden pins can be very annoying, i know the problem from orcad times. You  
can use a "supply block" for components that use hidden supply (imagine a  
quad opamp, i will havbe 4 opamp symbols inside and a supply block  
symbol). The supply blocks can be put together in one area of the  
schematic and connected in parallel to the supply and capacitors as  
required. This is not so clean looking as totally hidden supply, but IMO  
in a schematic that is used to create a PCB and does _not_ show each and  
every pin is worthless. Leaving out pins may be nice for some earlier  
design stage, but the PCB really needs a full schematic. I would expect  
eagle will allow to use supply blocks (every software that allows multiple  
symbols inside one component can do that, eagle is one of them i think).

If you use reference symbols instead of wires having all supply pins on  
the component symbol does not add much "clutter", and i actually prefer  
that over supply blocks. When i read the schematic thinking "which pin was  
supply again" i don't need to look at the component, see that it is say  
IC4, search IC4 amongst the supply blocks, and read the numbers, it will  
all be there in one place like a real-life component.


>
> Time for my question,  I  just finished routing my board (by hand!), and
>
> I see that I  have vias that somehow have the wrong hole size?  They
>
> show up on the design rules check.  I have 12 mil signals and 24 mil
>
> power traces.  They need changed, but what's the spec?
>

Depends on the drill sizes you can have. People seem to prefer several  
vias over one larger one for high current traces.

ST