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  • Members: 380
  • Category: Computers
  • Founded: Jan 17, 2005
  • Language: English
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#27370 From: joshbensadon
Date: Fri Sep 7, 2012 11:50 pm
Subject: Analog Computers - General description
joshbensadon
 
I'm trying to learn something about these old computers.  First of all, do they
actually follow program steps? I always equated the term computers with
something that can follow directions, calculate numbers, make decisions based on
the results. How were these old computers used? Who used them? etc.





#27372 From: David Gesswein <djg@...>
Date: Sat Sep 8, 2012 12:23 am
Subject: Re: Analog Computers - General description
dgesswein
Send Email Send Email
 
On Fri, Sep 07, 2012 at 11:50:32PM -0000, joshbensadon wrote:
> Are you saying the transistors in the old analog computers are robust?
> I haven't looked at part numbers yet, but they look like the old
> germanium TO-05 case style.
>
It wasn't intended to be that strong a statement. I don't have an analog
computer so don't have direct knowledge. From other electronics the lower
speed stuff tended to use transistors with breakdown voltages higher than
the supply. Also that a quick look assuming the parts are easily visible
will give you an idea of if overvoltage is likely to damage the unit. if
the breakdown voltage is somewhat higher than the preregulated voltage
then your unlikely to fry all the transistors if the supply looses
regulation.

> I'm trying to learn something about these old computers. First of all,
> do they actually follow program steps? I always equated the term
> computers with something that can follow directions, calculate numbers,
> make decisions based on the results. How were these old computers used?
> Who used them? etc.
>
I'm not that familiar with them.

They aren't computers in the modern sense. They simulate linear and
some nonlinear continuous time systems. They don't do steps and programming
is patch cables to wire the analog components in the correct configuration
for your problem and setting pots to set your coefficients. I think they
also had parts such as capacitors on plug in units to set the right values.
I think we have people on the list who have more knowledge than me who
hopefully will chime in.

Some promising links for info.
http://en.wikipedia.org/wiki/Analog_computer
http://ericarcher.net/devices/analog-computer-bouncing-ball/
http://courses.engr.illinois.edu/ece486/labs/lab1/analog_computer_manual.pdf




#27374 From: "Dave" <dave.g4ugm@...>
Date: Sat Sep 8, 2012 8:40 am
Subject: RE: Analog Computers - General description (long)
g4ugm
Send Email Send Email
 
> -----Original Message-----
> From: midatlanticretro@yahoogroups.com
> [mailto:midatlanticretro@yahoogroups.com] On Behalf Of David Gesswein
> Sent: 08 September 2012 01:23
> To: midatlanticretro@yahoogroups.com
> Subject: Re: [midatlanticretro] Analog Computers - General description
>
>
> On Fri, Sep 07, 2012 at 11:50:32PM -0000, joshbensadon wrote:
> > Are you saying the transistors in the old analog computers
> are robust?
> > I haven't looked at part numbers yet, but they look like the old
> > germanium TO-05 case style.
> >
> It wasn't intended to be that strong a statement. I don't
> have an analog computer so don't have direct knowledge. From
> other electronics the lower speed stuff tended to use
> transistors with breakdown voltages higher than the supply.
> Also that a quick look assuming the parts are easily visible
> will give you an idea of if overvoltage is likely to damage
> the unit. if
> the breakdown voltage is somewhat higher than the
> preregulated voltage
> then your unlikely to fry all the transistors if the supply looses
> regulation.
>
> > I'm trying to learn something about these old computers. First of
> > all,
> > do they actually follow program steps? I always equated the term
> > computers with something that can follow directions,
> calculate numbers,
> > make decisions based on the results. How were these old
> computers used?
> > Who used them? etc.
> >

I have never used an analog computer in anger but I was taught to use them
as part of my Mathematics degree in 1972/3 and latterly I am part of the
team that maintains and demonstrates the Hartree Differential Analyzer at
the Museum of Science and Industry, Manchester England. If you have browser
other than IE you can see a flash video of the Hartree here:-

http://www.cs.man.ac.uk/~chl/hartree.html

I include this as the Hartree is a mechanical analog (analogue in the UK)
computer and a direct parent of the Electronic Analogue Computer. On the
Hartree we use the number degrees a shaft has turned to represent a variable
in our "program" , in an Analog Computer we use a voltage to represent a
variable.

The feature of what are vernally termed "analogue computers" (or
"differential analysers" in early references) is being able to "calculate"
the area under a curve, which mathematicians call "integration". This might
not seem a very useful thing to do, but in fact this ability will be needed
to solve a wide range mathematical problems involving "time".

At a simple level if we have a graph of say the speed of a car, and plot
this, then the area under the curve will give the distance travelled. If we
have a graph of acceleration then the area under that is speed. So if we
have two "integrators" then from acceleration we can calculate speed and
distance. This becomes interesting when we have equations that connects
these together. So if you fire a projectile (much nicer word than shell)
from a gun and you know the angle of the gun, the initial velocity of the
shell, the mass of the shell and its coefficient of drag then using Newton's
Laws of motion we can develop equations that link these together. These are
called differential equations. We can then set up a "program" on our analog
computer than shows where the shell is at any point in time. Of course
usually we are only interested in where it actually lands, but if we include
air resistance in the equations we typically need to do the whole
calculation to figure this out. Historically this calculation is what drove
analogue computer design and development.

So as part of its commissioning testing the Hartree was used to simulate
coal consumption in Railway Engines (I am told Hartree was a bit of a Steam
nut), calculate cooling rates in steel ingots, simulate noise in
transmission lines and model the stability of aircraft. Of course the
driving force behind the initial development of all this stuff is gunnery
calculations.

The plug in capacitors mentioned below are what perform the integration, the
amount of charge stored in these capacitors represents the area. For a low
voltage it will charge slowly, for a higher voltage more quickly. There are
high gain circuits (operational amplifiers) around the capacitor so its
charge doesn't dissipate. They are often on plug ins and switchable as
changing the values of the cap allows the program to run at different
speeds. For a problem such as the cooling of an ingot, we probably don't
want to wait several hours for our program to run, so we speed it up by
using smaller capacitors which charge more slowly. For problems like noise
in transmission lines where we are dealing in pulses travelling at close to
the speed of light then we will have to slow things down a bit. If we are
using one as part of an aircraft simulator for training pilots then
essentially we want real time.

They were widely used as they were much cheaper to make than a digital
computer and they could solve the problems in real time. In 1972 at college
we had three commercial analogue computers and I think 12 or 14 constructed
by the lab technicians.


> I'm not that familiar with them.
>
> They aren't computers in the modern sense. They simulate
> linear and some nonlinear continuous time systems. They don't
> do steps and programming is patch cables to wire the analog
> components in the correct configuration for your problem and
> setting pots to set your coefficients. I think they also had
> parts such as capacitors on plug in units to set the right
> values. I think we have people on the list who have more
> knowledge than me who
> hopefully will chime in.
>
> Some promising links for info.
> http://en.wikipedia.org/wiki/Analog_computer
> http://ericarcher.net/devices/analog-computer-bouncing-ball/
> http://courses.engr.illinois.edu/ece486/labs/lab1/analog_compu
ter_manual.pdf


Dave Wade G4UGM
Illegitimi Non Carborundum







#27380 From: "s100doctor" <hjohnson@...>
Date: Sat Sep 8, 2012 6:38 pm
Subject: Re: Analog Computers - General description (long)
s100doctor
Send Email Send Email
 


--- In midatlanticretro@yahoogroups.com, "Dave" <dave.g4ugm@...> wrote:
>
> I have never used an analog computer in anger but I was taught to use them
> as part of my Mathematics degree in 1972/3 and latterly I am part of the
> team that maintains and demonstrates the Hartree Differential Analyzer at
> the Museum of Science and Industry, Manchester England. If you have browser
> other than IE you can see a flash video of the Hartree here:-
>
> http://www.cs.man.ac.uk/~chl/hartree.html
>

I'm really pleased, as an engineers of the 1970's, to see a brief presentation
of mechanical analog (differential) computers in the MARCH discussion. This is
truly "lost technology" by my standards and I'm glad it's getting support in the
UK.

To answer the original question, about the nature and use of electronic analog
computing. If you are interested enough, obtain some books on the subject from
the era. Many engineering books about analog computing are available cheaply
from Amazon - cheaper than those books on eBay that aren't listed by title, in
order to sell them at higher prices. In addition, you can get many of those same
books by loan through your local library, from university collections. That
service is called "interlibrary loan" and you can talk to your local library
about that service.

While it's fun to talk about these things and discuss questions and answers thru
email - it's more PRODUCTIVE to do the homework of reading the available
literature, and that means paper books. They won't be available for many years
longer; that's another discussion. They were designed to explain the use of
these analog computers, to people would use them "in anger" as the poster
described. You will need to understand differential equations, just as any
binary programmer of microcomputers needs to understand Boolean logic and binary
arithmetic.

But differential equations STILL describe processes and model systems, from
chemical to economic, that are still modeled today. These machines can STILL do
some "work" that means something. They won't play Adventure, but you can have an
adventure in learning about and using them.

Herb Johnson
retrotechnology.com







#27384 From: Mike Loewen <mloewen@...>
Date: Sat Sep 8, 2012 7:47 pm
Subject: Re: Re: Analog Computers - General description (long)
mloewen16823
Send Email Send Email
 
On Sat, 8 Sep 2012, s100doctor wrote:

> To answer the original question, about the nature and use of electronic
> analog computing. If you are interested enough, obtain some books on the
> subject from the era. Many engineering books about analog computing are
> available cheaply from Amazon - cheaper than those books on eBay that
> aren't listed by title, in order to sell them at higher prices. In
> addition, you can get many of those same books by loan through your
> local library, from university collections. That service is called
> "interlibrary loan" and you can talk to your local library about that
> service.

You might start with "The Handbook of Analog Computation":

http://www.analogmuseum.org/library/eai_handbook.pdf

Also on that page are dozens of manuals, handbooks, tutorials and
lectures about analog computing:

http://www.analogmuseum.org/english/library.html


Mike Loewen mloewen@...
Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/



#27386 From: joshbensadon
Date: Sun Sep 9, 2012 12:58 am
Subject: Re: Analog Computers - General description (long)
joshbensadon
 
--- In midatlanticretro@yahoogroups.com, Mike Loewen <mloewen@...> wrote:
>
> You might start with "The Handbook of Analog Computation":
>
> http://www.analogmuseum.org/library/eai_handbook.pdf
>
> Also on that page are dozens of manuals, handbooks, tutorials and
> lectures about analog computing:
>
> http://www.analogmuseum.org/english/library.html
>
>
> Mike Loewen mloewen@...


Mike, Thanks! That's a great place to start. As usual, I have much homework to
do... so I'll be here in the corner, quietly reading if anyone wants me.

I'm going to search around that site to see if they might even have schematics
for this EAI computer.

Cheers!
Josh





#27385 From: joshbensadon
Date: Sun Sep 9, 2012 12:53 am
Subject: Re: Analog Computers - General description (long)
joshbensadon
 
--- In midatlanticretro@yahoogroups.com, "s100doctor" <hjohnson@...> wrote:
> To answer the original question, about the nature and use of electronic analog
computing. If you are interested enough, obtain some books on the subject from
the era. Many engineering books about analog computing are available cheaply
from Amazon - cheaper than

Thanks Herb,

Your good words are always a welcomed sight.
Yes, I have much reading to do. The online book referenced by Mike appears to
be a real gem, especially since this Analog Computer is an EAI model. I did a
search for "Analog Computer" on Amazon and got 3,000+ hits. Can you help me out
with a known title?

Further, would you know if schematics can be found for these old computers,
sorry I don't have the exact model number. If you do have these schematics in
your collection, please name your price.

Cheers,
Josh






#27460 From: "s100doctor" <hjohnson@...>
Date: Mon Sep 24, 2012 5:02 pm
Subject: Re: Analog Computers - General description (long)
s100doctor
Send Email Send Email
 


--- In midatlanticretro@yahoogroups.com, joshbensadon wrote:
>

> Thanks Herb,
>
> Your good words are always a welcomed sight.
> Yes, I have much reading to do. The online book referenced by Mike appears to
be a real gem, especially since this Analog Computer is an EAI model. I did a
search for "Analog Computer" on Amazon and got 3,000+ hits. Can you help me out
with a known title?
>
> Further, would you know if schematics can be found for these old computers,
sorry I don't have the exact model number. If you do have these schematics in
your collection, please name your price.
>
> Cheers,
> Josh

I just saw your message, about two weeks after you posted it.

Contact me privately, if you want specific things from me, Josh. I don't read
this MARCH list on any regular basis, or engage in long discussions on it in
general. That's simply not what I do, why that may be is not particularly
relevant except to say it's nothing to do with you.

Also, I can't follow exactly what schematics you are looking for, and how on the
one hand you have some kind of EAI computer, but on the other hand don't know
what model it is.

I'm sorry you find the learning situation about them, to be complicated and with
an unclear path. That's the nature of technology which is obsolete, generally
used only by scientists and specialists, and largely documented only in books
from the period. And from a period before personal computers and digital
networking of any kind - not that most of that would help.

Since I'm of that obsolete and ancient time, and I was an engineer, I know
something about it. But not something I can point to easily, that's in one book,
or that can be learned by reading one or two books.

Sorry, but that's not my fault. It's old, it's complicated, it involves
knowledge about things. Without that knowledge, operating an analog computer
will make no sense at all, and seeing it run will be incomprehensible. It was
difficult at the time, that knowledge is still difficult today. I can't
reasonably think of an easy way to get around those circumstances - either about
the background knowledge needed, or the operational knowledge to use such
things, as they are almost IDENTICAL - and entirely unlike personal computing
today.

herb




#27470 From: joshbensadon
Date: Mon Sep 24, 2012 10:13 pm
Subject: Re: Analog Computers - General description (long)
joshbensadon
 
--- In midatlanticretro@yahoogroups.com, "s100doctor" <hjohnson@...> wrote:
>
> Also, I can't follow exactly what schematics you are looking for, and how on
the one hand you have some kind of EAI computer, but on the other hand don't
know what model it is.
>

Please let me explain. It's not my computer, but it belongs to the York
Univeristy Museum operated by Zbigniew Stachniak. I only get to work on this
machine once a week or every two weeks, and I didn't get to see the exact model
of it. Zbigniew told me the model number last week, but my lack of short term
memory strikes again.

I'm not in any rush to learn all about it, I'll just take my time and enjoy the
ride. I've already found some information online (thanks to the posts in this
group).

PS. My contact with Zbigniew should also be credited to Bill and Evan's Hope
presentation. I live 10 minutes from York and have been visiting the campus for
years but have never known about their Vintage Computer Museum until now.

Cheers,
Josh





#27472 From: "Evan Koblentz" <evan@...>
Date: Mon Sep 24, 2012 10:37 pm
Subject: Re: Re: Analog Computers - General description (long)
ekoblentz
Send Email Send Email
 
>>> My contact with Zbigniew should also be credited to Bill and Evan's Hope
presentation. I live 10 minutes from York and have been visiting the campus for
years but have never known about their Vintage Computer Museum until now.

Awesome. Tell Zig I said hello.




#27473 From: "B. Degnan" <billdeg@...>
Date: Tue Sep 25, 2012 1:51 am
Subject: re: Re: Analog Computers - General description (long)
billdeg
Send Email Send Email
 

> >
>
> Please let me explain. It's not my computer, but it belongs to the York
Univeristy Museum operated by Zbigniew Stachniak. I


York, PA?

>
> PS. My contact with Zbigniew should also be credited to Bill and Evan's
Hope presentation. I live 10 minutes from York and have been visiting the
campus for years but have never known about their Vintage Computer Museum
until now.
>

I live kind of close and would be interested to drive out some time to
check it out.

http://www.cse.yorku.ca/museum/

What's actually on display there?

Bill




#27475 From: joshbensadon
Date: Tue Sep 25, 2012 2:42 am
Subject: Re: Analog Computers - General description (long)
joshbensadon
 
--- In midatlanticretro@yahoogroups.com, "B. Degnan" <billdeg@...> wrote:
> York Univeristy Museum operated by Zbigniew Stachniak. I
>
>
> York, PA?
>

No, York University in Toronto, Ontario.

> What's actually on display there?
>


I'm a newbie at old computers, so I'll probably miss a few key systems.
I think Zbigniew's favorite is the MCM 70 computer, he wrote a whole book on it.
There are lots of other systems as you saw in the web link you provided, but I'm
not sure what's worth mentioning? Dynalogic systems? There's some of the the
more familiar common systems, but several word processors and obsure ones I
don't remember the names of. But there is a whole line of MCM computers. These
were based on the 8008 and when that processor became too slow, they went the
way of emulating the processor with faster logic chips so they wouldn't have to
re-write software.

Anytime you're in Toronto, I'd be happy to show you around.

Cheers,
Josh





#27474 From: "Evan Koblentz" <evan@...>
Date: Tue Sep 25, 2012 2:01 am
Subject: Re: Re: Analog Computers - General description (long)
ekoblentz
Send Email Send Email
 
>> York, PA?

Toronto, Canada.






#28512 From: Jim Scheef <scheefj@...>
Date: Sat Dec 8, 2012 2:44 pm
Subject: Re: Analog Computers - General description
jscheef
Send Email Send Email
 
Josh,

Did you ever get any response to your question?

I think of an analog computer as a device that models a problem and thus 'calculates' the answer by varying inputs to the model and then measuring an output. Accuracy depended on the accuracy of the model which could be rods and gears or electric circuits or both. Analog computers that are used today include tide clocks or the more common clocks what show the phase of the moon (location is one of the inputs). Big analog computers in the 30's were used to 'solve' multiple differential equations. Artillery tables are the most common example from WWII.

The Wikipedia article is http://en.wikipedia.org/wiki/Analog_computer

Jim

On 9/7/2012 7:50 PM, joshbensadon wrote:
 

I'm trying to learn something about these old computers. First of all, do they actually follow program steps? I always equated the term computers with something that can follow directions, calculate numbers, make decisions based on the results. How were these old computers used? Who used them? etc.



#28513 From: Bob Schwier <schwepes2002@...>
Date: Sat Dec 8, 2012 3:17 pm
Subject: Re: Analog Computers - General description
schwepes2002
Send Email Send Email
 



From: Jim Scheef <scheefj@...>
To: midatlanticretro@yahoogroups.com
Sent: Saturday, December 8, 2012 9:44 AM
Subject: Re: [midatlanticretro] Analog Computers - General description

 
Josh,

Did you ever get any response to your question?

I think of an analog computer as a device that models a problem and thus 'calculates' the answer by varying inputs to the model and then measuring an output. Accuracy depended on the accuracy of the model which could be rods and gears or electric circuits or both. Analog computers that are used today include tide clocks or the more common clocks what show the phase of the moon (location is one of the inputs). Big analog computers in the 30's were used to 'solve' multiple differential equations. Artillery tables are the most common example from WWII.

The Wikipedia article is http://en.wikipedia.org/wiki/Analog_computer

Jim

On 9/7/2012 7:50 PM, joshbensadon wrote:
 
I'm trying to learn something about these old computers. First of all, do they actually follow program steps? I always equated the term computers with something that can follow directions, calculate numbers, make decisions based on the results. How were these old computers used? Who used them? etc.
We still used analogue computing systems in the Navy in the 1970's.  Each synchro could be adjusted with a pot which
one tweaked in with a small screwdriver.  When one got the last pot tweaked in one went back and started over to
make sure that the whole system was still in alignment.  The system was hard wired with no significantly changeable
components.
bs



#28523 From: Ken <kenzolist@...>
Date: Sat Dec 8, 2012 7:09 pm
Subject: Re: Analog Computers - General description
kenzolist@...
Send Email Send Email
 
On 9/7/2012 7:50 PM, joshbensadon wrote:
>I'm trying to learn something about these old computers. First of all, do they
actually follow program steps? I always equated the term computers with
something that can follow directions, calculate numbers, make decisions based on
the results. How were these old computers used? Who used them? etc.

I just happened to have discovered this great video a couple of days ago. It's
a 50's US Navy instructional film about the mechanical computers they used.
It's really eye-opening and very high quality. (It gets to the meat about two
minutes in.) For me, it demonstrated the analog/mathematical approach, in
contrast to the digital/logical approach I grew up learning.
http://www.youtube.com/watch?v=s1i-dnAH9Y4

- Ken




#28564 From: "s100doctor" <hjohnson@...>
Date: Tue Dec 11, 2012 3:07 am
Subject: Re: Analog Computers - General description
s100doctor
Send Email Send Email
 


--- In midatlanticretro@yahoogroups.com, Ken <kenzolist@...> wrote:

> I just happened to have discovered this great video a couple of days ago.
It's a 50's US Navy instructional film about the mechanical computers they used.
It's really eye-opening and very high quality. (It gets to the meat about two
minutes in.) For me, it demonstrated the analog/mathematical approach, in
contrast to the digital/logical approach I grew up learning.
> http://www.youtube.com/watch?v=s1i-dnAH9Y4
>
> - Ken
>
http://www.eugeneleeslover.com/VIDEOS/fire_control_computer_1.html

It looks like the site linked above is a primary Web source for WWII and later
Naval fire control computer documents. It may be the original source for the
video referenced above, or certainly an earlier one.

These control computers used rotational position (radius vs angle) as means of
expressing an analog function. One input variable was a cam on a shaft; two
input variables was a surface on a cylinder. By cascading, you could have
several variables per output. The video series shows this, and the Navy
textbooks on the site above explain further.

Mechanical computers like this were "programmed" by manufacture; one design
equals one program. Electronic analog computers were programmed by wiring panels
and adjusting components, as well as by design or by hard-wire. Hybrid analog
computers, made the connections and adjustments digitally.

I knew nothing about the above, until I did some Web searching based on the
reference first given. It's good to see more ancient technology on the Web. In
this case, advanced WW II technology, digitized from books and films.

Herb Johnson





#28566 From: William Donzelli <wdonzelli@...>
Date: Tue Dec 11, 2012 3:41 am
Subject: Re: Re: Analog Computers - General description
toober00
Send Email Send Email
 
> http://www.eugeneleeslover.com/VIDEOS/fire_control_computer_1.html
>
> It looks like the site linked above is a primary Web source for WWII and
> later Naval fire control computer documents. It may be the original source
> for the video referenced above, or certainly an earlier one.

I think some of these are originally from the Historic Naval Ships
Association. There is a group of us ship geeks that are also trying to
save and archive the technology, bitsavers style.

> These control computers used rotational position (radius vs angle) as
> means of expressing an analog function. One input variable was a cam on a
> shaft; two input variables was a surface on a cylinder. By cascading, you
> could have several variables per output.

There is also a class of fire control computers that used linear
displacement of levers and linkages, rather than rotation. These
machines were much cheaper to make, but not quite as accurate. And of
course, there were hybrids of all sorts. I had a small collecton of
small machines and assemblies at VFC East number 2.

Trivia - there are two Mk 4 Torpedo Data Computers still in active
service, in the Taiwan Navy. They have been in near continuous service
since 1946.

--
Will



 
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