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'[EE] Circuit design & drawing way back when'
2006\02\22@204200 by Russell McMahon

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Copied (as allowed) from Jack Ganssle's latest 'Embedded Muse"
newsletter. All engineers should get this. Even if usually only
skimmed his newsletters are invariably insightful, amusing and, as a
bonus, useful. (Subscribe information at end)

_______


An insight into the terrible days of how it used to be. Some of us
remember them :-)


       RM

______________


Pre-CAD
-------
A number of people have been inquiring about an article I wrote long
ago about the pre-CAD days. Here it is:

Long ago, back in the 70s, there were no personal computers or
similar tools we take for granted. The life of a digital designer was
very different indeed.

Computer folks used the same tools as civil engineers. Offices were
dominated by the drawing board, a 6 by 3 foot flat panel propped at a
"comfortable" angle. Engineers lived in high chairs strangely
reminiscent of Dicken's Bob Crachet, hunched over the drawing board
with mechanical pencil in hand, creating wonderful silicon inventions
using the same paper and lead that writers and philosophers relied on
for centuries.

Drafting was a skill all mechanical engineers mastered in college,
but for some reason, at the University of Maryland, it was not
considered important for electronics guys (guys - all guys. There
were virtually no women in the field then). Some engineers were
nothing short of gifted artists, creating schematics that filled the
paper in a visually pleasing way. Others, myself included, could
hardly draw a straight line even with the aid of a drafting machine.

Lettering was a fine art. It's hard to imagine this now, when we
select from a thousand fonts with a few mouse clicks, but neat signal
names were essential. Some designers used lettering templates. I
always found these too cumbersome, and so subjected all readers of my
drawings to the same illegible scrawl that the nuns weekly punished
me for in grade school.

Every branch of engineering had its unique set of templates. Digital
designers used a handful of plastic stencils that contained the
entire stock of resources we worked with: AND and OR gates, inverters
and "not" circles, and, of course, various sized squares and
rectangles for microprocessors, memories, and everything else. Large
chips were rare then; the largest might have a whopping 64 pins,
which wasn't too hard to draw.

We drew resistors, capacitors, and other components using similar
stencils. With a little practice you could whip the pencil through
the zigzag of a resistor template in no time, though a
not-perfectly-sharp pencil always resulted in only a hazy image of the
part.

Though Luddites scoff that computers let us make mistakes at new,
unprecedented rates, in fact even with these crude tools we were
quite competently creating errors faster than decent designs. In lieu
of a "delete" key we used erasers. Erasers in every form imaginable.
In fact, most of us made so many mistakes we used electric erasers, a
motorized drill-like device that spun a cylinder of gum-like
material. Though these quite effectively removed vast areas of pencil
lead, careless use always produced a hole in the vellum. Then what? I
suppose mil spec folks started over, recopying the entire drawing
onto a fresh sheet of paper. Where I worked we glanced furtively over
the shoulder, and rerouted signals around the hole.

Drawings produced by hand - by sloppy electronic folks - had much
wider line widths and larger lettering than that we make on computer
screens today. As a result the drawings were big. Though some folks
used "C" size paper (17 by 22 inches) generally "D" (22 by 34) was
the norm. Engineers, production people, and technicians all looked
like quintessential architects, with stacks of these monsters on
every flat surface. When troubleshooting a new design the first step
was to position a big table next to the lab bench - just to hold the
drawings.

We drew on vellum, a gauzy semi-transparent material that was pretty
tough. It took repeated erasures well, though somehow I always
managed to drill a couple of erasing holes through each drawing.

Today we use mostly "A" and "B" sized paper, as that's all
laserprinters handle. You can fax or Xerox these drawings without
trouble. An ordinary filing cabinet is the perfect storage place.
Back then, every business had a "drawing room", dedicated to nothing
more than storing (in cabinets called "flat files") and reproducing
these huge representations of our tiny circuits. Most companies had
people whose entire role was to file and copy these.

No copier then or now could handle a sheet of D sized paper. One
reason we used vellum was its transparency. An engineer duplicating a
drawing first put it on top of an equal-size piece of paper coated
with a light-sensitive chemical, and ran it through the Ozalid
machine. This beast beamed a very intense light through the vellum,
exposing areas with no pencil marks. It then treated the paper with
ammonia, which turned the unexposed areas blue. The ever-present
smell of ammonia (and second hand cigarette smoke!) was simply a part
of the engineering environment.

Once the ammonia line broke in the middle of the night. In the
morning the entire building was uninhabitable. Fire department fans
eventually sucked the fumes out, but we found strange chemical
changes in our environment. One secretary's fake flowers changed to a
wonderful purple shade. Many pictures hanging on walls now looked
like 19th century daguerreotypes. And, of course, several thousand
dollars of unused Ozalid paper were completely developed, bright blue
reminders of the incident.

Now drawings have no value. Did you spill coffee on a schematic? Just
print out a new copy. The information itself if immensely valuable,
but its paper incarnation is sacrificial.

Before CAD systems the paper was the only representation of a
drawing. The labor required to recreate one was so immense that it
was simply inconceivable to lose or mar a schematic. It's funny to
realize that one promise of computerization was the paperless office,
yet what has happened is paper is now so prevalent that it's
worthless. By contrast, in the olden days an original drawing was a
holy relic. Copies were scarce because of the cost of duplication and
the nuisance of storing the bulky papers.

The regulations said no drawing left the files unless it was being
duplicated or was on an engineer's drafting board. Most of us
flaunted these rules when the Ozalid machine (which required an hour
to warm up) was off at night and we were engaged in a furious
troubleshooting war. Living dangerously, with the original by the
bench, we'd hope to be done by morning when the drawing police came
in. More than one drawing went back in the files with food stains in
the corners.

I suppose it goes without saying that there were no PCB software
packages. Either our engineers or outside contractors, leaning over a
light table for weeks on end, routed tracks by placing black tape on
sheets of mylar. It was a game of chess: the best board designers
developed a mental plan of attack which (they hoped) would let them
get all of the tracks down without running into dead ends. How things
have changed! Now it's great fun to watch the routing program
automatically plopping traces down onto the virtual board, at a speed
that takes my breath away. In the 70s a big board took weeks, even
months, to design.

They routed on mylar, as paper isn't dimensionally stable when
subjected to humidity variations, and the PCB was made via a
photographic reduction of the drawing. My dad, a mechanical engineer
from way back, tells me that in the 50s they had the same problem
with paper when designing airplanes. Since this predated even mylar,
they drew on starched linen in ink. Apparently the linen was stable,
but it couldn't tolerate water. One drop of sweat dissolved the
starch, ruining the drawing. And this was before Grumman, his
employer, had air conditioning.

Me, I'm thankful for modern CAD. I'd never go back to those tedious
days of yore.

=======================================


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2006\02\22@220924 by Chen Xiao Fan

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> From: .....piclist-bouncesKILLspamspam.....MIT.EDU
> [EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTMIT.EDU] On Behalf Of Russell McMahon
> Sent: Thursday, February 23, 2006 9:40 AM
>
> Copied (as allowed) from Jack Ganssle's latest 'Embedded Muse"
> newsletter. All engineers should get this. Even if usually only
> skimmed his newsletters are invariably insightful, amusing and, as a
> bonus, useful. (Subscribe information at end)
>
> An insight into the terrible days of how it used to be. Some of us
> remember them :-)
>         RM
>

Thanks for the newsletter. I do not think it is really "way back
then". I used the A1/A0 drawing board and T-square for my
engineering graphics course quite sometime ago. And people
tell me that they are still using this kind of setup today,
at least in part of the world. I think it is beneficial.

I got the only 'D' in this engineering graphics course. ;-(
I think this is the only 'D' I got in any science/engineering
courses throughout my many years as students. I really lack
the patience of drawing an A0 drawing. It took us more
than 10 hours to finish one drawing. Throughout the semester,
we needed to finish about 8 drawings. "Lettering was a fine
art" and that was very true. We need to use a special font
(in Chinese) for the drawings and it was really difficult
for me.

Drawing electronics schematics are much easier since it
is 2D. Layout drawings are more difficult. Still I will
say big CAD programs like Pro-Engineer are still much more
difficult to use than electronics CAD programs.

Regards,
Xiaofan

2006\02\22@234002 by Neil Cherry

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Chen Xiao Fan wrote:
{Quote hidden}

Uhm, I still draw some of my designs on weird plastic
paper (I don't know what it is). I used to draw schematics
that would cover the entire table. I preferred just a ruler
and I was pretty neat (I did well in that course). I
remember using another sheet of paper to protect the drawing
while I lettered in the info. I remember the electric
erasure. :-) I still have a fondness for 0.5 lead and
preferred hard to soft lead. Alway remember to have clean
hands and arms. I still remember the stink of the
special copier machine for schematics (yuck!). What I need
now is a good tablet to copy my drawings (networks). The
one thing that EE drawing did for me is to permit me to
quickly draw complex diagrams with lots of info in my note
books (neatly of course).

--
Linux Home Automation         Neil Cherry       KILLspamncherryKILLspamspamlinuxha.com
http://www.linuxha.com/                         Main site
http://linuxha.blogspot.com/                    My HA Blog
http://home.comcast.net/~ncherry/               Backup site

2006\02\23@094857 by John Ferrell

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You may be an old time techie (OTT) if you have any or all of the following:
   T-Square
   Drafting instruments
   Slide rule
   Drafting machine
   VTVM
   RCA Receiving Tube Manual
   More than 5 Heathkits
   Simpson 260 Multimeter
   Any equipment with the Olson, Lafayette or Knight brand name.

When I finally got around to upgrading my Ham license to Extra Class a few
years ago, I noticed an collective gasp in the class room when I sat down
and placed my Dietzgen Log-Log-Decitrig slide rule on the desk in front of
me. It doesn't matter what everyone else was thinking, this old man felt
like a Jedi Knight...
BTW, I never needed the slide rule!


John Ferrell
http://DixieNC.US

{Original Message removed}

2006\02\23@102125 by alan smith

picon face
And...don't forget....Bishop Graphics.....
               
---------------------------------
Yahoo! Autos. Looking for a sweet ride? Get pricing, reviews, & more on new and used cars.

2006\02\23@103126 by Ling SM

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I am glad I only have to use these drawing gears in school.

My sweating palm often caused my grade to suffer by 1 band, and time and
effort to draw at least 50% more than average.  Then again, the sweaty
feature was useful for testing transistor, until they become smaller
than a grain of rice now.

All those "Just In Case" learning and accumulation of expensive tools
have progress to "Just In Time" of resources collection and relationship
building.  Am I a librarian now?

Ling SM

2006\02\23@105939 by Harold Hallikainen

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Though I don't still have my T-Square or schematic templates, I still have
lots of drawings done in the 1970s, hand taped PC board layouts (remember
Bishop Graphics?), my slide rule, my HP 35, my father's slide rule, the
RCA Receiving Tube Manual (for a small version, see
http://sujan.hallikainen.org/BroadcastHistory/index.php/RCA), Heathkit
audio voltemeter, distortion analyzer, and audio generator. I had a
Simpson 260, but I dropped it out of a tree and broke it. In high school
we ran telephone and teletype lines all over the neighborhood (built a
small step switch in my garage). When looking for a broken line, I'd climb
the tree with my Simpson 260 and check it out. I dropped it. I had the
Knight Kit Radio Broadcaster (http://www.knightkit.com/). Built it in
fourth grade and used it for years.

Harold


{Quote hidden}

> {Original Message removed}

2006\02\23@154353 by David VanHorn

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On 2/23/06, alan smith <RemoveMEmicro_eng2TakeThisOuTspamyahoo.com> wrote:
>
> And...don't forget....Bishop Graphics.....


And ChartPak!

2006\02\23@163323 by Peter Todd

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On Thu, Feb 23, 2006 at 09:49:06AM -0500, John Ferrell wrote:
> You may be an old time techie (OTT) if you have any or all of the following:
>     T-Square
>     Drafting instruments
>     Slide rule
>     Drafting machine
>     VTVM
>     RCA Receiving Tube Manual
>     More than 5 Heathkits
>     Simpson 260 Multimeter
>     Any equipment with the Olson, Lafayette or Knight brand name.
>
> When I finally got around to upgrading my Ham license to Extra Class a few
> years ago, I noticed an collective gasp in the class room when I sat down
> and placed my Dietzgen Log-Log-Decitrig slide rule on the desk in front of
> me. It doesn't matter what everyone else was thinking, this old man felt
> like a Jedi Knight...
> BTW, I never needed the slide rule!

There is hope... At my school, my friend Adam makes all his circuit
boards by hand, with a dremel, his circuit designs are all on paper and
he transfers them over to the board with a pen and a good sense of
layout. He also tends to draw stuff in the empty spaces... Great looking
boards, but I've still gotta get him a slide rule...

I made a bamboo slide rule for my dad last christmas, figured it was
fair as I have his one at my apartment. Still gotta learn how to use it
though.

--
spamBeGonepetespamBeGonespampetertodd.ca http://www.petertodd.ca

2006\02\23@170119 by Paul Hutchinson

picon face
> -----Original Message-----
> From: TakeThisOuTpiclist-bouncesEraseMEspamspam_OUTmit.edu On Behalf Of David VanHorn
> Sent: Thursday, February 23, 2006 3:44 PM
>
> On 2/23/06, alan smith <RemoveMEmicro_eng2spamTakeThisOuTyahoo.com> wrote:
> >
> > And...don't forget....Bishop Graphics.....
>
> And ChartPak!

And Datak! (JotDraft brand)

2006\02\24@070030 by Russell McMahon

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> And...don't forget....Bishop Graphics.....

Just been clearing out the basement.
Found a box with lots of Bishop Graphics stuff therein. All 2X scale.
Pads, edge connectors, ICs, tape etc.
I may put it in my museum bin. Or the 9 cubic metre jumbo-bin that's
sitting in the driveway - almost full. It's going to need another of
the same sometime soon.

Also shovelling 386 laptops, 486 DX... , mono screen. The Mac SE30 can
go in the museum. Also the original IBM PC and the ugly IBM L40SX
laptop. The 4 x communicators with 1 whole MB of static RAM in 128 x
(8kx8) may have to have one sample kept. The admiralty issue Geiger
Counter is museum fodder. I think. VT61 terminals? Hmmm. Why did I
keep those? Or acquire them in the first place? :-)



       RM

2006\02\24@070243 by Russell McMahon

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> I made a bamboo slide rule for my dad last christmas, figured it was
> fair as I have his one at my apartment. Still gotta learn how to use
> it
> though.

Do it. takes about zero time to get the basics. Some advanced stuff
takes more effort or is easily forgotten. Being able to do simple
multiplication and division with pieces of wood or plastic gives
increased appreciation of the shoulders we are standing on.

The slide rule works by adding lengths of rule which are proportional
to the logarithms of the numbers being multiplied and reading off the
number whose logarithm is proportional to the resultant length. Far
easier to do than to explain.

Once you master that you can progress to measuring the heights of
doorways by dropping a coin and timing how long it takes to fall :-).
(Averaging 10 attempts produces almost usable accuracy).


       RM

2006\02\24@105144 by Josh Koffman

face picon face
On 2/24/06, Russell McMahon <apptechEraseMEspam.....paradise.net.nz> wrote:
> Just been clearing out the basement.
> Found a box with lots of Bishop Graphics stuff therein. All 2X scale.
> Pads, edge connectors, ICs, tape etc.
> I may put it in my museum bin. Or the 9 cubic metre jumbo-bin that's
> sitting in the driveway - almost full. It's going to need another of
> the same sometime soon.

Nooooooooo.....

One of my lifetime goals is to come to NZ and visit you and Joe.
Assuming I make it there someday, I expect a spectacle! I'd imagine
I'll just be walking around with a big grin the entire time.

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

2006\02\24@151034 by Gerhard Fiedler

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Russell McMahon wrote:

>> I made a bamboo slide rule for my dad last christmas, figured it was
>> fair as I have his one at my apartment. Still gotta learn how to use it
>> though.
>
> Do it. takes about zero time to get the basics. Some advanced stuff
> [...]
>
> Once you master that you can progress to measuring the heights of
> doorways by dropping a coin and timing how long it takes to fall

The one thing I have never been able to figure out of the "advanced stuff"
is how you measure the time a coin takes to fall down from the height of a
doorway with a slide rule. The manuals of all rules I've seen only refer to
this as one of the "advanced techniques" ...

Gerhard

2006\02\24@160731 by Harold Hallikainen

face picon face

{Quote hidden}

Drop the sliderule from the same heighth, and time it. They should be
close to the same amount of time!

Harold


--
FCC Rules Updated Daily at http://www.hallikainen.com

2006\02\24@163502 by Lindy Mayfield

flavicon
face
Olet suomalainen, vai?

-----Original Message-----
From: EraseMEpiclist-bouncesspammit.edu [RemoveMEpiclist-bouncesEraseMEspamEraseMEmit.edu] On Behalf Of Harold Hallikainen
Sent: Friday, February 24, 2006 11:07 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Circuit design & drawing way back when

Drop the sliderule from the same heighth, and time it. They should be
close to the same amount of time!

Harold



2006\02\25@140936 by Peter

picon face

On Fri, 24 Feb 2006, Gerhard Fiedler wrote:

> The one thing I have never been able to figure out of the "advanced stuff"
> is how you measure the time a coin takes to fall down from the height of a
> doorway with a slide rule. The manuals of all rules I've seen only refer to
> this as one of the "advanced techniques" ...

You drop the coin, bend down to pick it up, and as you straighten up
measure the door height using the slide rule. Then you can express the
door length in sliderules.

Peter

2006\02\25@193139 by Peter Todd

picon face
On Sat, Feb 25, 2006 at 01:02:39AM +1300, Russell McMahon wrote:
> > I made a bamboo slide rule for my dad last christmas, figured it was
> > fair as I have his one at my apartment. Still gotta learn how to use
> > it
> > though.
>
> Do it. takes about zero time to get the basics. Some advanced stuff
> takes more effort or is easily forgotten. Being able to do simple
> multiplication and division with pieces of wood or plastic gives
> increased appreciation of the shoulders we are standing on.

Also been told some people like sliderules because it shows you the
relative magnitudes of the numbers you are working on at all times.

My dad once told me one of the earliest screw-ups he ever heard of with
an electronic calculator happened at the forestry department he was in.
Back in the mid 70's someone was off doing the calculations to see how
many trees they could sustainably cut in the university forest lot.
Aparently the calculations were done on an electronic calculator, and he
person doing them made a small error with the decimil points... A few
years later, in the early 80's, someone else noticed that they'd been
cutting ten times more trees than was sustainable. Ooops.

No word on whether the person who found the mistake was using a slide
rule though. :)

> The slide rule works by adding lengths of rule which are proportional
> to the logarithms of the numbers being multiplied and reading off the
> number whose logarithm is proportional to the resultant length. Far
> easier to do than to explain.

Ahh, yeah, I remember the concept from highschool math, where even in my
time the teacher mentioned slide rules while teaching logorithms. I've
yet to actually get the details correct.

> Once you master that you can progress to measuring the heights of
> doorways by dropping a coin and timing how long it takes to fall :-).
> (Averaging 10 attempts produces almost usable accuracy).

Haha, yeah, gotta have a good stop watch though. I perfer Feynman's
(think this is where the story is from) methods, such as attaching a
long enough string and lowering the slide rule from the top of the
doorway... Or measuring the difference in period with a string and
sliderule pendulum and using the difference in gravitational field...

--
RemoveMEpetespam_OUTspamKILLspampetertodd.ca http://www.petertodd.ca

2006\02\26@090651 by Gerhard Fiedler

picon face
Peter Todd wrote:

>>> I made a bamboo slide rule for my dad last christmas, figured it was
>>> fair as I have his one at my apartment. Still gotta learn how to use
>>> it though.
>>
>> Do it. takes about zero time to get the basics. Some advanced stuff
>> takes more effort or is easily forgotten. Being able to do simple
>> multiplication and division with pieces of wood or plastic gives
>> increased appreciation of the shoulders we are standing on.
>
> Also been told some people like sliderules because it shows you the
> relative magnitudes of the numbers you are working on at all times.

This is not quite correct. The slide rule does /not/ show you the magnitude
of the numbers, it only shows you the number itself; no decimal point, so
to speak. (Or better said, while working on the slide rule, the decimal
point is in an arbitrary position. Arbitrary WRT the actual calculation,
that is.)

But the crucial thing is that when working with a slide rule, /you/ have to
do the magnitude calculation and put the decimal point in the right place.
For example, you estimate the result to be something between 200 and 500.
The slide rule may give you the number 3.87, and by combining your estimate
of the magnitude with the numeric sequence from the slide rule you know the
result is 387.

And this is the part that sadly got largely lost with electronic
calculators. Some people who have that inclination very strongly still know
it anyway. For some this is so strange that they wouldn't learn it even
when working with slide rules. But for the many in between, not inclined
enough to know it anyway and not too estranged to it so that they never
would have learned it, they miss out on something that is IMO a valuable
skill: knowing how to estimate the magnitude of a numeric result just by
looking at the numbers.

> Aparently the calculations were done on an electronic calculator, and he
> person doing them made a small error with the decimil points...

That's exactly the thing I was writing about.

> Ahh, yeah, I remember the concept from highschool math, where even in my
> time the teacher mentioned slide rules while teaching logorithms. I've
> yet to actually get the details correct.

y = a * b;
log y = log a + log b;

That's basically it. On a slide rule, you have the numbers placed on
locations that correspond to the logarithm of the number. Say you have a 10
cm slide rule. log 1 = 0, so 1 is at the start of the scale. log 10 = 1, so
10 is at the end of the scale. log 2 = 0.30, so 2 is at 3 cm. log 3 = 0.48,
so 3 is at 4.8 cm.

Adding 3 cm (2) to 4.8 cm (3) gives 7.8 cm. This is exactly where the 6 is,
because log 6 = 0.78, so the 6 is at 7.8 cm.

The only additional step is that when adding 7.8 cm (6) to 3 cm (2), this
results in 10.8 cm, which is beyond the 10 cm we had said our slide rule
has. But since we disregard decimal point positions anyway, this just wraps
over to 0.8 cm, by subtracting 10 cm (which is a factor of 10, or in other
words just a matter of the irrelevant position of the decimal point). And
0.8 cm is where 1.2 is on the rule, because log 1.2 = 0.08, or 0.8 cm with
a 10 cm scale.

Gerhard

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