Re: S-100 prototype boards
- From: Herbert Johnson <herbrjohnson@xxxxxxxxx>
- Date: Sun, 17 May 2009 18:27:57 -0700 (PDT)
On May 16, 8:40 pm, lynchaj wrote:
As for the points Herb mentioned, I am fine with constructive criticism.
Good, thanks for your considerations and positive reactions.
Still, I enjoy making home brew computers, what ever the
definition actually is, so I do enjoy making these units. It's
constructive and a positive hobby.
My strategy with these units is to address some, IMO, long standing
barriers to hobbyists interested in S-100 home brew computing. That
is making your own computers from scratch with the possible inclusion
of a pre-made PCB. I've found a major barrier to S-100 home brew
computing is the lack of infrastructure pieces; specifically
backplanes, power supplies, prototyping boards, and design libraries
for EDA tools. ...maybe a chassis.... Something that's repeatable and can be
consistently and reliably done so not everyone has to start at square
one.
Well, I see your point now. You're providing boards, or board layouts,
in a consistant and available fashion. For *anyone* who wants to use
them to create what you reasonably call "infrastructure S-100" -
backplane and prototype card. I guess, it's an alternative to trying
to find old boards - although I was surprised myself to find Vector
still offers their protoboards.
In the old days, making your own PC boards was really tough and
expensive. I guess it's easy enough now and cheap enough that some
would rather make a few and order them, then hunt around for them. A
matter of taste and expectations, maybe of patience too.
Now, building a physical chassis...that's a different set of tools and
skills, it's about metalwork and some odd components like plastic PC
board "slides". Buying that stuff new is not cheap, and weight adds to
shipping costs for "offshore" providers - not like PC boards. If it
were me, I'd go with just laying down general principles and critical
measurements and parts lists. Chances are, someone would want to adapt
a design to some physical layout of their choosing. Where to put the
bus, where to put the power supply, will vary. Some would build a
chassis, some might buy a "box". Bending metal into boxes is not that
tough. A good resource for this, are old ARRL Amateur Radio
"Handbooks", from the days of radio building and chassis-making. They
have transistor-power supplies also, and much of their work was with
TTL - same voltages we use!
Buying an old S-100 chassis is really a bargain, in my opinion,
compared to making one "from scratch"; unless, like Andrew, one really
likes to do chassis work.
I won't design a S-100 SMPSU as it is beyond my skill set....
The main issue with S-100 power
supplies, IMO, is they are typically custom solutions. I do not know
of an off the shelf solution with S-100 compatible voltages short of
buying an old one from eBay or buying two or three SMPSUs.
I had to look that up. "Switch Mode Power Supply Unit". Switchers are
so cheap now, even new, I don't see the point of designing one AND
it's beyond my skill set too. Companies like MPJA (http://
www.mpja.com/powersupply.asp) sell both "surplus" and new switching
supplies. A beefy plus-several volt supply, and a +15/-15 volt supply,
should not be that hard to find...?
What I've done, is to take old "open frame" +/- 12V and +5 V power
supplies - linear regulated supplies - and simply turn up the
regulators to get a few more volts, for the on-board regulators to
chew on. They need about a 2-volt drop. Or, one can run a "regulated
power" S-100 system, and simply short out or remove the board
regulators, so the boards run "straight" +5, +12, -12 - dirt common
power supply levels.
Building a NON regulated supply is not tough, that's stone-age design
- transformers, rectifiers, and caps, an inductor if you are fancy
about it. Few enough components, that a PC circuit board isn't needed
- not for me, anyway. Look at some old S-100 chassis/mainframe
manuals, to see how simple some of those DC supplies were. The power
supplies in the Compupros are really nice - ferro-resonant regulating
transformers, monster caps. Other than weight, nothing wrong with many
of the old S-100 power supplies. But add some DC-side fuses, to avoid
turning your backplane into one big FUSE, if you short out +8 Volts!
I'm glad my point of view was seen as mostly a matter of style and
preference. I should look at making PC boards myself. Thanks, Andrew!
Herb Johnson
retrotechnology.com
.
- References:
- S-100 prototype boards
- From: lynchaj
- Re: S-100 prototype boards
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- Re: S-100 prototype boards
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- Re: S-100 prototype boards
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- Re: S-100 prototype boards
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