9 Mar
2009
9 Mar
'09
12:14 a.m.
Hi Andrew,
That is a brilliant effort, and will be worthwhile once it is produced.
Just a couple of small things I noticed.
1) Is it possible to use a pad that has a little bit more copper area
than the thin pads I see on the diagram. My standard complaint with
modern PCB software is that the pads are too small, (or possibly I am
too old!) and I tend to have to make my own pads.
2) Where the tracks pass 'through' the connector, there is a fairly
long area where they are *very* close. If you alter the layout, you
could reduce that, and reduce the likelihood that constructors would
introduce a short when they are manufacturing the board (of course, that
probably isn't an issue when you use a commercial PCB facility and use
solder masks.) My experience is making PCBs at home, where there is no
concept of *very fine* spacings.
In any case, please mark me down for two when you do a PCB run. (seems
to me like you could link them using the headers!)
Doug
Andrew Lynch wrote:
S-100 backplane board spacing
Hi, here is a rough draft of the PCB layout for a low cost S-100 prototyping
PCB I am considering. The primary goal is to make this PCB affordable yet
still useful to S-100 hobbyists. It is not intended to be a full blown
S-100 system or a permanent backplane but rather a bench tool. Keeping the
costs low means a small number of connectors and avoiding features such as
termination, etc. Having a small number of connectors minimizes the bus
length and reduces the need for termination. A benefit of this backplane is
a hobbyist could use it to develop new boards and/or repair older ones
without risking damage to a costly or rare vintage S-100 chassis.
The builder would have to supply the necessary S-100 voltages from their own
power supply. The power supply interface is just PCB pads that could have a
connector or just direct wired to the supply. Possible power supply
solutions would be off the shelf SMPSUs to supply +15VDC, -15VDC, and 9VDC
to the rails or alternatively surplus laptop adapters could be modified to
supply the necessary power. A small number of boards reduces the need for
large power supply capacity.
The 13x2 dual row header connectors are optional for use as a stand alone
S-100 backplane. However, they are necessary for my own project which will
use this PCB. PCB construction will be the usual double thickness PCB for
rigidity and double weight traces for current capacity.
http://n8vem-sbc.pbwiki.com/f/Printing%20S100-Backplane-full-brd.pdf
If you would be interested in a PCB, please contact me off list. My intent
is to keep this consistent with the other N8VEM PCBs so the target price is
$20 each for the PCB only plus shipping. There is no estimate for arrival
for the PCB as of now. I am only trying to gauge what, if any, interest
there might be in the S-100 hobbyist community.
Constructive comments, suggestions, and questions appreciated. Thanks and
have a nice day!
Andrew Lynch