4 Nov
2002
4 Nov
'02
8:05 a.m.
From: "Patrick Finnegan"
<pat(a)purdueriots.com>
On Sat, 2 Nov 2002, Patrick Finnegan wrote:
Hi
The absolute voltages read are not an issue because you are looking
for relative changes. Still, the resistors and capacitors on the
patch field need to have tight tolerences to get accurate results.
I managed to pick up a COMDYNA GP-6 analog
computer a couple days ago out
at University Salvage. I initially bought it for its nixie tubes, not
knowing what it was, and then was a bit dissatisfied with the fact that
they were not in great shape.
After taking a few seconds to look at it and try to determine what is was
with all the banana jacks on the front, I thought "Hmm, it adds and
multiplies... google says 'Analog computer'... Wahooo!!"
More info about the one I have - looks to be an early model - with nixie
tubes intead of the modern LED voltmeter. Also, the problem with the
display tubes went away when I reseated the display cards in their
sockets.
After playing with this little guy, I'm suprised at how stable the
components are - when I'm not touching anything, there's basicall NO
jitter on the display. It looks like some component values have
deteoriated or drifted a bit, but seems in nearly excellent shape. I'm
about to go out to RatShack so I can get some more banana plugs and
create some more patch cables (assuming that they still sell those...)
One last thing - does anyone have an idea of what the "SW" and "OP"
jacks
at the bottom of the front panel are, and how to use the multipliers? I
can't quite seem to get them to 'multiply'...
The multipliers may be over ranging. These usually only work over
a small range of inputs. It might also be that your unit doesn't
include the multipliers. Most analog computing functions don't
require the nonlinear operation of multipliers and use mostly
integrators and adders.
Did you look at the page: http://www.comdyna.com/gp6panb.htm#MULT ??
It describes the use of the multiplier. It needs to be used in
conjunction with an amplifier and feedback resistor.
You might look at the bouncing ball routines for the EC-1.
It looks like you should have 8 amplifiers. I think this is
enough to do this routine with. I'm not sure if the info for
this is on a web page someplace.
Dwight
Thanks for any info
Pat
--
Purdue Universtiy ITAP/RCS
Information Technology at Purdue
Research Computing and Storage
http://www-rcd.cc.purdue.edu
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