[sdiy] how to best learn the trade

[Peter Keller]

On Tue, Feb 19, 2008 at 04:37:55PM -0500, Robert Krueger wrote:
> Thanks for all the amazing advice. I honestly never even considered
> breadboards before. I've been reading up on them and that seems like
> the easiest/cheapest way to go to test out a design and experiement
> with tweaks.

By far that's true. However, breadboards can be noisy and do some
frequency attenuation at higher frequencies, like if signals are traveling
through the breadboard contacts at 4MHz or higher. I've personally never
had a problem with the digital signals I've shoved across a breadboard at
speeds of 2-4MHz so I wouldn't worry about it too much. Analog signals
would be at a much lower frequency, around 25KHz for audio frequencies,
so you don't have to worry about that.

> At what point do you decide you want to go with a PCB?  How does one
> go from a schematic to a making/having made a PCB. What PCB resources
> are out there?

>From my simple understanding, if you simply want the device as a standalone
piece of equipment, then you have to do some kind of soldering to make it
permanent.

The simplest way to make a low (or medium if you are very careful)
complexity circuit is a copper strip board, which is a breadboard layout
on a pre-made PCB.

http://www.radioshack.com/product/index.jsp?productId=2103800&cp=2032058.2032230.2032265&parentPage=family

Then, if you want to go beyond that and make your own PCBs, you need an
EDA (electronic design automation) package that you use on a computer.
There was some thread a bit ago that detailed a bunch. I happen to use
gEDA cause I use linux and it seems to work for my needs. Most of these
EDA tools go all the way from schematics specification to laying out the
PCB.

Since I've started using EDA, I can tell you that it is a real pain
in the ass to learn how to use it. There is so much jargon and overly
verbose documentation and bad user interfaces to initially learn that
ultimately you might think pencil and paper is faster. :) But, once you
get through this mess, the EDA tools allow you to produce a PCB layout
which allows you to design where the traces go on a PCB. You also have
things like a drill map, which obviously shows drill holes in the center
of the copper pads where the components attach, etc.

Once you get the schematic->PCB layout finished, you have two options,
if the PCB layout is only 2 layer (top and bottom) you can make your
PCB at home, and use a drill press to drill the holes. Time consuming,
possibly dangerous due to the etching chemicals, but rewarding in the end.

Or, you can take the finished PCB layout files (called gerber files,
I think) and give them to some gigantic fab in China and get 10 or 20
boards back. Of course, it'll cost like 300 bucks to do this or more, but
300 bucks isn't a lot of money for how much time you can spend doing this.
These companies can even place all of your parts on to the boards too.

I've only ever done the first strip board option since I don't currently
have the knowledge to go from schematic->PCB with gEDA yet. Once I do
though I'll probably send the files away to be produced into boards for
my needs and solder them myself.

Until then, I'll be using strip board PCB cause they are a good tradeoff
at this point. 

I wish I had a better selection of PCB strip boards that what my local
radio shack has. I'd love a strip board with an ISA connector on it or
something so I can make home brewed cards to shove into a home brewed
backplane...

Later,
-pete