Re: [MBZ] OT: the analog thing

[Buggered Benzmail via Mercedes]

Lo these many years ago I did a summer internship at NASA Langley in the 
real-time simulation group where we had this 737 cockpit simulator. There was a 
big room full of CDC top-end computers, 7600s, STAR 100s, a coupla Crays and 
such that drove that thing and did other stuff. 

There was another room that had this big analog computer in it. The thing was 
like 10ft tall and 15ft wide. There were only 3 guys left who knew how to 
program the thing. I visited and watched them one day do some kind of 
simulation. They were totally manic running patch cords and twisting knobs and 
whatever else. The guys were kinda crazy looking too, total old school 
engineers. There were lots of dials showing voltage or whatever. Paper rolls 
with pens marking out whatever outputs and inputs. It was all pretty crazy but 
that stuff got men to the moon and helped build some wild aircraft so I guess 
it worked. 

When those guys were gone that was probably the end of that technology too. 

--FT
Sent from iFōn

> On Sep 24, 2021, at 11:47 AM, Jim Cathey via Mercedes  
> wrote:
> 
> Ah, that takes me back.  I used an analog computer once, in college.
> Probably the last days for those, there.  The EE dept. also had a hybrid
> computer.  Huge analog patch panel, and a digital computer around
> the edges.  It also didn't stick around too much longer, either.
> 
> Once the speed of digital computers had picked up a bit, you could do
> all the equivalent work digitally, sufficiently fast and without all the patch
> panel wiring.  That takes some time to get right.  You also can't save 
> programs,
> unless you have a spare removable patch panel that you can set aside.  (The
> hybrid offered that.  Besides saving programs, which really wasn't done, it 
> let
> one operator build up his program while someone else was actually using the
> computer.)
> 
> With analog, you have to map/scale all quantities and times into the circuit.
> Additional work.  Analog also offers, at best, slide-rule precision.  Digital
> simulation kicks ass in all those areas.
> 
> What analog DOES have, is operating speed.  Unmatched.  Oscilloscopes
> were used very often to show the solutions 'live', with the simulation running
> over and over again refreshing the solution on the 'scope(s).  Also, if an 
> analog
> voltage was what you needed, for an actuator or something, analog computing
> allowed you to work directly in that space, with no D/A conversion required.
> 
> Consider one 'practical' use for an analog computer: driving servomotors,
> the kind that move to a position specified by an analog voltage.  These
> ball-on-plate digital sims: https://www.youtube.com/watch?v=sFtfWoAzHwg 
> 
> could be done very well entirely in the analog domain.  (You just need a 
> feedback
> system that gives you two voltages proportional to the ball's position on the 
> plate.
> I'm not sure what those resistive touchscreen panels provide.)
> 
> -- Jim
> 
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Re: [MBZ] OT: the analog thing

[Jim Cathey via Mercedes]

Ah, that takes me back.  I used an analog computer once, in college.
Probably the last days for those, there.  The EE dept. also had a hybrid
computer.  Huge analog patch panel, and a digital computer around
the edges.  It also didn't stick around too much longer, either.

Once the speed of digital computers had picked up a bit, you could do
all the equivalent work digitally, sufficiently fast and without all the patch
panel wiring.  That takes some time to get right.  You also can't save programs,
unless you have a spare removable patch panel that you can set aside.  (The
hybrid offered that.  Besides saving programs, which really wasn't done, it let
one operator build up his program while someone else was actually using the
computer.)

With analog, you have to map/scale all quantities and times into the circuit.
Additional work.  Analog also offers, at best, slide-rule precision.  Digital
simulation kicks ass in all those areas.

What analog DOES have, is operating speed.  Unmatched.  Oscilloscopes
were used very often to show the solutions 'live', with the simulation running
over and over again refreshing the solution on the 'scope(s).  Also, if an 
analog
voltage was what you needed, for an actuator or something, analog computing
allowed you to work directly in that space, with no D/A conversion required.

Consider one 'practical' use for an analog computer: driving servomotors,
the kind that move to a position specified by an analog voltage.  These
ball-on-plate digital sims: https://www.youtube.com/watch?v=sFtfWoAzHwg 

could be done very well entirely in the analog domain.  (You just need a 
feedback
system that gives you two voltages proportional to the ball's position on the 
plate.
I'm not sure what those resistive touchscreen panels provide.)

-- Jim

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[MBZ] OT: the analog thing

[Allan Streib via Mercedes]

Find myself strangely interested in getting one of these. Not sure what I'd do 
with it. Was wondering if it might be good for "prototyping" various types of 
control circuits, but guessing an Arduino is likely a better choice.

https://the-analog-thing.org/
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