Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "ghidera2000" 
<ghidera2000@y...> wrote:
> --- In Homebrew_PCBs@yahoogroups.com, "Dave Mucha" 
<dave_mucha@y...> 
> wrote:
> > Hi all,
> > 
> > I was wondering it there is an introduction to basics of 
> schematics 
> > and board design?
> 
> Me Three :D
> 
>  
> > Things like what polarity is the square pad on an LED ?

OK, My friend has been around a long time and has pretty much done it 
all.  Says the square pad on a 2 pin is ground.  That's where it all 
started.

that go me thinking about when I was doing instrumentation schematics 
(as opposed to pcb schematincs)  there is a complete written 
stanadard that details everything.   It would make electronics a 
little easier if were adopted some of those practices, or if they 
existed.




> > 
> > are there 'standard' drill sizes that are common for all board 
> > houses ?
> 
> IFAIK no, just 1/32, 1/16. whatever is the smallest size your parts 
> will easily fit into. Probably 1/16th would be the best general 
> purpose - though them big diode leads generally won't fit. Need 
3/32 
> I think.



YIKES !    I use a #78 for resistors (0.015")   0.9mm for thru chips 
and 1/16 for screw terminals.   I just figured that there is 
something more 'standard' than using one of each lot. 



> > and it seems a 90 degree corner on a 15 mil trace, when etched 
can 
> be 
> > undercut to less than 10 mil.
> 
> So put a couple 45's in there instead. Check out a trace width 
> calculator like 
> http://www.geocities.com/CapeCanaveral/Lab/9643/TraceWidth.htm. You 
> might be suprised at how much current a tiny bit of copper can 
> carry. e.g. a 15 mil trace can carry 1 full amp and only raise five 
> degrees C.


Thans for the link.   (btw, the period on the end makes it a pita to 
use.)


 
> Hey, who was your homeroom teacher? I might have had the same one!


Nellie Prymaite.  

She taught us by sitting beside Nellie in the moring and in the 
afternoons, she would have us do what she did.

It sound like we went to different high shcools together.

Dave