Homebrew PCBs

> Being green about electronics, most of my designs do not work first 
> time out.  Most of the stuff I have been designing does not lend 
> itself well to breadboarding or even perf boards.  So, I do the best 
> I can in the design, layout the circuit, and make the PCBs myself. 
> If things go as usual, I may make the same board 3 or 4 times in one 
> day and that is very key for me.  I don't like waiting 1 week, 2 
> weeks, 3 weeks, etc. for something I can do right now.
> 
> So, really, there are two primary advantages to making PCBs at home; 
> Economics and Instant gratification :-)
> 
> Chris
> 

A couple of pointers.  (getting back close to the list topic) when you
lay out your boards, put in some extra pads on both the Vcc and Vss
lines.  plop them around both sides of chips.

add a set of 6 pads like a dice #6, connect one to Vcc and one to Vss.
 that allows you to put in more stuff.  

and then in areas that have nothing, put in a row of 10 pads in line
for 0.025 sq posts.  you can make a small card with a header and add a
whole different circuit that way.

Also, if you have a chip you are not really sure about, and it has
Vcc, Vss, in and out, you can put in 4 pins, again 0.025, so you can
lay on a whole different board.

I had made a large relay board, 32 relays I think.  Very large board.

It was controlled by I2C bus and a pair of port expanders.

I laid them out with the port expanders on cards so I could swap them
out for SPI bus if that was the better way to go.

http://www.flickr.com/photos/33033234@N00/

buy using the daughter cards, the logic could have been swapped around
if needed.

This is the largest board I have made on my T-Tech machine, and as I
said yestarday, if I were to do it again, it would have been 2 boards.

BTW, anyone wanna guess how much a one-off board would have been at a
board house ?

I think it was $5.00 for the board and an hour in the machine.

Dave