How are *official* schematics presented?

[Rich Grise]

Really... I would have thought the techs would have preferred it to, in that
it's more common to look at a schematic, get suspicious about, e.g., R9 and
need to find it on the board than spy a random component on the board and need
to find it on the schematic?

These days you're generally next to a compute that has both the schematic and
layout loaded and can immediately find R9 for you on both anyway, at least.

Yeah, but they didn't do it that way in 1976. ;-)

Cheers!
Rich

 

[Rich Grise]

Y is often seen for oscillators; that's what I use.

I've seen 'X' used as "the generic black box".

Cheers!
Rich

 

[Rich Grise]

Q because T (Transistor) was taken by Transformer WAY before the crystal
triode was invented, U because I (Integrated circuit) was preempted by
(Incandescent) Lamp, and A (according to my reference texts) is Antenna.
s/incandescent/indicator/;

Cheers!
Rich

 

[Joerg]

I think your method is perfectly acceptable for digital schematics and
wires that traverse major distance. With many FPGAs having I/O pin
counts of a few hundred pins, it makes sense to do it the way you
describe. It makes the schematic easier to read. For analog stuff,
that usually hooks up with wires fairly nicely.

For technicians and test folks, I like to provide the schematic in PDF
format so they can search for net names and components. Orcad Capture
and SDT does this nicely.

I also furnish TIFF files along with it. In case service has to email it
to someone out in the boonies at the end of one of those long singing
wires, or dial-up in web speak.

 

[Joerg]

We use P for male connector, which is the mil/aerospace convention. We
also use M for mechanical part, which is not.

They use M for mechanical parts. For tanks

[...]

The A380 wire harness fiasco, gigabucks of blunder, was partly caused
by incompatible drawing conventions across several countries.

Might also be partly due to language barriers. I wish they'd agree on
one language for technical stuff.

 

[Paul Burke]

Units are used as is customary, whatever the client wants. For me right
now that's mostly inches and 1/1000th. After all, chip pins are still
separated by fractions of an inch.

Yes, fractions like 5/254ths for 0.5mm QFPs.

 

[John Fields]

s/incandescent/indicator/;

 

[JeffM]

And, what's a "Pascal"? (well, I know it's a unit of pressure
[...]but how many PSI or atmospheres is it?)

Or a "Torr"? Or etc., etc., etc....

A tasy little Windoze app:
http://joshmadison.net/software/convert/
Let us know if it has problems under WINE.

 

[Jan Panteltje]

And, what's a "Pascal"? (well, I know it's a unit of pressure
[...]but how many PSI or atmospheres is it?)

Or a "Torr"? Or etc., etc., etc....

A tasy little Windoze app:
http://joshmadison.net/software/convert/
Let us know if it has problems under WINE.

It runs OK in wine.
I installed via the install shield.

 

[JeffM]

I'm not sure about the origin of Q,

It seems to be the last letter remaining.
after all the logical choices were used.

"U" derives from Unit, and A is Amplifier or Assembly.

....with the distinction that any U is *unrepairable*
(way back when, there were potted subassemblies and such)
and an "A" is can be disassembled and repaired.

Fields and Grise were debating "I" (indicator/incandescent)
and went on to "DS", which I understand
comes from Device, Signaling (audible or visual).

 

[qrk]

I also furnish TIFF files along with it. In case service has to email it
to someone out in the boonies at the end of one of those long singing
wires, or dial-up in web speak.

Do you use TIFF for file size? PDF should be on par with TIFF with LZW
or CCITT compression. Plus, PDF always looks pretty no matter how much
you zoom in. If you really want small, try JBIG2 Lossy or JPEG2000.
Here's my file size test results for a moderately full D-size
schematic. All, except for the PDF, are bit-mapped images.

PDF/JBIG2: 42.8kB (using JBIG2 Lossy)
PNG: 97.2kB
TIFF/CCITT4: 110kB (Zips down to 87kB)
PDF/CCITT4: 111kB (Zips down to 89kB)
PDF: 119.2kB (vector graphics, not bit-mapped)
TIFF/LZW: 126.4k

 

[Joerg]

Do you use TIFF for file size? PDF should be on par with TIFF with LZW
or CCITT compression. Plus, PDF always looks pretty no matter how much
you zoom in. If you really want small, try JBIG2 Lossy or JPEG2000.
Here's my file size test results for a moderately full D-size
schematic. All, except for the PDF, are bit-mapped images.

PDF/JBIG2: 42.8kB (using JBIG2 Lossy)
PNG: 97.2kB
TIFF/CCITT4: 110kB (Zips down to 87kB)
PDF/CCITT4: 111kB (Zips down to 89kB)
PDF: 119.2kB (vector graphics, not bit-mapped)
TIFF/LZW: 126.4k

I just use the PDF converter in OpenOffice and on a typical schematic it
comes out much larger than TIFF. But my designs are mostly analog so the
graphics are a bit "weirder" than the usual logic blocks. So mostly I
come close to 1MB in PDF. Doing another one right now and I'll try
different PDF structures on this one. Let's see.

 

[redbelly]

And, what's a "Pascal"? (well, I know it's a unit of pressure and a really
gay programming language, but how many PSI or atmospheres is it?)

It's probably one of the few SI units that does NOT get used in
practice (to my knowledge). To answer your first question, it's a
Newton per square meter. I've seen it used in some school textbooks,
but not elsewhere.

Or a "Torr"? Or etc., etc., etc....

Uh, those are pretty commonly used in high vacuum work. 760 Torr is 1
atm.
And meterologists seem to like millibars, at least in the U.S. A bar
is within 1 or 2% of 1 atm.
Oddly, I'm giving you all this from memory ... didn't look up or use
Google for any of it ...

Thanks!
Rich

You're welcome,

Mark

 

[Joerg]

Yes, fractions like 5/254ths for 0.5mm QFPs.

Or 125/200th of a millimeter for a TSSOP

 

[Ray]

It's probably one of the few SI units that does NOT get used in
practice (to my knowledge). To answer your first question, it's a
Newton per square meter. I've seen it used in some school textbooks,
but not elsewhere.

Sorry, but in Australia:

hectoPASCALS have been used for pressure charts, for many many years
now. (apparently the same as millibars)
Therein lies a hint that Pascals are a direct unit of measure against
bar ! ie 1000 * 100 = 100,000 Pa = 1 bar

You can pump your tyres up to a specified kPa value - lets just say
240kPa is commonly used. (~35 PSI)

A truly metricated world WE live in and DO use in practice.

 

[Rich Grise]

s/incandescent/indicator/;

[/QUOTE]

In this context, 's' means "substitute". (it's a programming thing.) The
way I heard it was that the 'I' was for "indicator", is all.

Thanks,
Rich

 

[Robert Latest]

On Fri, 26 Jan 2007 12:42:50 -0800,

I just use the PDF converter in OpenOffice and on a typical schematic it
comes out much larger than TIFF. But my designs are mostly analog so the
graphics are a bit "weirder" than the usual logic blocks. So mostly I
come close to 1MB in PDF. Doing another one right now and I'll try
different PDF structures on this one. Let's see.

You should stay with vector graphics all the way for PDF. You can export
your schematic as PS and convert that to PDF.

Although Eagle seems to have truly weird PS output. I just tried it --
exported an A4 schematic as 300dpi PNG -> 80K. The same schematic as
PS came out closer to 1MB.

I'll have to investigate that because it doesn't make any sense at all.

robert

 

[Tero Kapanen]

And, what's a "Pascal"? (well, I know it's a unit of pressure
[...]but how many PSI or atmospheres is it?)

Or a "Torr"? Or etc., etc., etc....

A tasy little Windoze app:
http://joshmadison.net/software/convert/
Let us know if it has problems under WINE.

Check this out:
http://www.google.com/search?hl=en&q=10+torr+in+atmospheres&btnG=Google+Search
http://www.google.com/search?hl=en&q=mass+of+earth+*speed+of+light/5s&btnG=Search

I have converter on every machine without installing anything.

- tero

 

[redbelly]

hectoPASCALS have been used for pressure charts, for many many years
now. (apparently the same as millibars)
Therein lies a hint that Pascals are a direct unit of measure against
bar ! ie 1000 * 100 = 100,000 Pa = 1 bar

You can pump your tyres up to a specified kPa value - lets just say
240kPa is commonly used. (~35 PSI)

A truly metricated world WE live in and DO use in practice.

Well I'll be a ...
That's what I get for not looking it up

Mark

 

[Robert Latest]

On Fri, 26 Jan 2007 19:52:34 GMT,

It runs OK in wine.
I installed via the install shield.

Have you tried the native Unix app, "units"? It converts everything into
everything, even doing some basic arithmetics if necessary.
Gas mileage example (my 1995 Golf):

~$ units
2438 units, 71 prefixes, 32 nonlinear units

You have: 6.7 l/100km
You want: mpg
reciprocal conversion
* 35.106654
/ 0.028484628
You have:

robert