Today's Message Index:
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1. 08:34 AM - Becoming CAD-proficient to a practical level of usefulness (Robert L. Nuckolls, III)
2. 03:53 PM - Solid State Relay Alert (Robert L. Nuckolls, III)
Message 1
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| Subject: | Becoming CAD-proficient to a practical level of usefulness |
At 11:04 PM 10/20/2007 -0700, you wrote:
>
>Bob and all,
>
>Thanks for all the help here. I worked on it until 3:30 this AM and again
>today after a long nap. I'm doing much better now. The plan at the moment
>is to begin with existing drawings and moving, copying symbols to get it to
>be what it needs to be. So far so good. A few more hours and I'll be on my
>way. Thanks again for all the input received. This list is a great
>resource.
>
>Bevan
>Wires are beginning to know where they are supposed to go.
Pleased that you're making progress!
When you're ready to print any one of those views to
your printer or .pdf generator, know that each view's
upper left and lower right corners are marked with a
tiny, .001" radius circle. When you're ready to print one
page of your drawing, you can say "print to window" and
use the "snap-to-circle-center" command to find those
circles and define the print window. Alternatively, you
can print a particular view number. If you leave the
big master drawing's borders and views unmodified, then
each border becomes a box wherein you can edit contents
to match your needs and take advantage of the organization
for storing, editing, and printing your wirebook.
This is how I do drawings for many of my customers. ALL
drawings are crafted on the views/sheets of a single
AutoCAD file. Any change to any sheet advances the revision
level of the entire package. It's easy to keep my customer
apprised of progress . . I have only one file to forward.
When I'm finished with my work, the customer takes data
from the individual views and pastes it to their particular
organization for files, drawing organization, drawing
numbering, etc.
To all the other AEList readers - Acquiring a functional
familiarity with a CAD program can seem daunting. Virtually
any CAD program worth loading on your computer is capable of
understanding a 1000+ commands . . .
About 1985, I was where you are today. I had a PC-XT, 20Mb
hard drive, yellow screen computer with the grand total of
640K of ram. I think the thing ran at the blazing speed
of 4MHz.
I was offered a copy of AutoCAD v1.17 as I recall. It would
load and run in the XT environment. The very first images
published in the 'Connection were produced on this computer
running AutoCAD and printed on a pen-plotter.
I don't recall when I discovered the .pgp file . . . it
probably wasn't while running v1.17. The folks at AutoDesk
correctly deduced that if they were going to woo users of
other CAD systems to AutoCAD, the transition need to be
as seamless as possible. A really nice thing about
ACAD was that it understood plain english. If you wanted to
draw a line you typed "line <enter>". This capability was
consistent with the majority of commonly used draw, edit
and housekeeping commands. I think other CAD programs were
similarly endowed.
AutoDesk provided an ASCII text file lookup table that
would convert any string of characters into an AutoCAD
command. The file was called ACAD.PGP.
That was the list I published yesterday . . .
AR, *ARRAY
B, *BLOCK
WB, *WRITEBLOCK
BR, *BREAK
CI, *CIRCLE
C, *CHANGE
CH, *CHAMFER
CO, *COPY
D, *DIMSTYLE
DI, *DIST
DO, *DONUT
DT, *DTEXT
E, *ERASE
ED, *DDEDIT
EL, *ELLIPSE
XT, *EXTEND
EXIT, *QUIT
F, *FILLET
H, *HATCH
I, *INSERT
IP, *ISOPLANE
L, *LINE
LA, *LAYER
LI, *LIST
LT, *LINETYPE
M, *MOVE
MI, *MIRROR
OF, *OFFSET
OS, *OSNAP
P, *PAN
PE, *PEDIT
PL, *PLINE
PG, *POLYGON
P, *PAN
R, *REDRAW
RG, *REGEN
RT, *RECTANGLE
REN *RENAME
RO, *ROTATE
S, *STRETCH
SC, *SCALE
SCR, *SCRIPT
T, *TRIM
V, *VIEW
It was the intent of the programers to provide
users with (1) a way to shorten commonly used
commands to one or two letter strings and (2)
translate your commonly used commands for another
CAD application in to AutoCAD english.
I wasn't migrating from another cad system but
I was interested in speed. I discovered that if
I drove the mouse left-handed and typed right-
handed, I could move through the AutoCAD environment
much faster than by hitting pull-downs or typing
the full command line.
After a few years, it occurred to me that my .pgp
list was a good study guide. 99% of all the things
I asked AutoCAD to do in support of my tasks were
listed in the .pgp file.
When giving AutoCAD tutorials I can sit
across the table from a student and we both
have screens, keyboards, and monitors driving
of the same computer. I can do things that the
student sees, duplicates and then expands
upon. I use the .pgp file as a teaching list for
the commands for which first-competency is needed.
We can go through the list of 44 commands in
one day with sufficient frequency to offer good
retention. I teach these functions by MODIFYING
existing drawings. The CAD system is a tool for
describing your creations. It's important to be
proficient in the language of illustration first so
that the creative process doesn't get bogged down
in the mechanics of the language. In fact, we'll
usually start perhaps one or two new drawings . . .
the rest of the class concentrates on mechanics.
I'll suggest that this same list is useful
to all of you who are desirous of adding some CAD
skills to your bag of tricks. The commands may
be different but I would encourage you to become
proficient at getting your CAD system of choice
to do the functions cited in the list. I've not
modified the list in years. Out of the full
constellation of commands your CAD system responds
to, this list of 44 commands will trim your initial
learning task down to a very manageable size.
Bob . . .
Message 2
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| Subject: | Solid State Relay Alert |
Solid state "relays" for AC have been around for decades.
They generally use Triacs as the control device, are designed
for use at 120VAC and above and drop about 1.5 to 2 volts in
the "turned on" mode . . . not a big deal in a 120VAC circuit.
I've been watching a number of new solid state relay products
popping up for the DC world. They have the general appearance
of the photo posted here:
http://www.aeroelectric.com/Pictures/Relays/Solid_State_Relay.jpg
I've purchased a couple of exemplar products and was disappointed
to find that while they were "rated" for service in systems down
to 12VDC, their turned-on voltage drop was about 1.5 volts at
full load. The critter shown above was rated at 40A . . . but
would need a healthy heat-sink to get rid of the wasted energy.
These are not suited for use at 14V and only marginally suited
for 28V. I'll keep watching . . .
Bob . . .
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( "Problems are the price of progress. )
( Don't bring me anything but trouble. )
( Good news weakens me." )
( -Charles F. Kettering- )
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