How are *official* schematics presented?

[Didi]

I'm not sure about the origin of Q, but it is a military and

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

I have adopted what I saw in some Tektronix service manuals (for the
465
and/or 466 IIRC) in my late 20s (> 20 years ago by now... moan). I
guess
I have just made up some which I did not see.
CR - diode, VR - Zener diode, Q - transistor, U - any IC, etc.
It is curious how little it takes to transfer conventions, languages
etc.
(just a few books in this case .

Dimiter

 

[John Devereux]

I have adopted what I saw in some Tektronix service manuals (for the
465
and/or 466 IIRC) in my late 20s (> 20 years ago by now... moan). I
guess
I have just made up some which I did not see.
CR - diode, VR - Zener diode, Q - transistor, U - any IC, etc.
It is curious how little it takes to transfer conventions, languages
etc.
(just a few books in this case .

I always use the single letter variants - it's difficult enough
already to fit a readable component legend with surface mount parts.

D,R,C,L,Q

B (battery)
J (connectors)
X (crystals)
U (anything else)

 

[John Larkin]

I always use the single letter variants - it's difficult enough
already to fit a readable component legend with surface mount parts.

D,R,C,L,Q

B (battery)
J (connectors)
X (crystals)
U (anything else)

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

There is a great deal of convention and lore about how one constructs
top and subassembly drawings; now flags, notes, and find numbers are
shown; dimensioning and tolerances; product structure; assembly and
wiring; parts lists (BOMs); fabrication and test procedures and ECOs;
drawing numbers, resulting part numbers, and dash number variants;
part procurement specs. It's quite uniform in most industries, so an
engineer from one company can look at a product top assembly drawing
set from another company, for a complex item, and understand the
entire drawing tree structure. And build one and have it come out the
same.

We've sent a CD to a big contract assembler and had them procure
parts, build complex gadgets, and test them, without hassle and with
hardly any questions.

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

John

 

[Didi]

I always use the single letter variants - it's difficult enough

already to fit a readable component legend with surface mount parts.

D,R,C,L,Q

B (battery)
J (connectors)
X (crystals)
U (anything else)

Well may be more practical, but I guess I'll stick to my current style
as long as I don't have to change it... I gave up silk screening 15
years
ago, my board densities simply make it impractical (the area goes on
pads etc.). And while I do have an issue with the text on the control
plots (the "colourful picture" , it takes a lot of scaling up to
have
the text on the BGA pads and 0603 (not to speak 0402) parts readable,
I still manage it somehow - I retired the HP7475 plotter some time
ago, I now print on several sheets the "picture" then cut and
scotch-tape it together - or simply view it on the screen.
BTW having at least 3-digit numbers (sheet/part#) makes
the one more letter less of an issue for me...

Dimiter

 

[jure]

as long as I don't have to change it... I gave up silk screening 15
years
ago, my board densities simply make it impractical (the area goes on
pads etc.). And while I do have an issue with the text on the control
plots (the "colourful picture" , it takes a lot of scaling up to
have
the text on the BGA pads and 0603 (not to speak 0402) parts readable,
I still manage it somehow - I retired the HP7475 plotter some time
ago, I now print on several sheets the "picture" then cut and
scotch-tape it together - or simply view it on the screen.
BTW having at least 3-digit numbers (sheet/part#) makes
the one more letter less of an issue for me...

Dimiter

we, as a rule, define the reference designator numbers following the
layout placement,
not the logical flow in the schematic.

The first input connector on the first page may get the ref des J9 !

Jure

 

[Rich Grise]

I'm not sure about the origin of Q, but it is a military and
commercial standard.

"Quality factor".

Cheers!
Rich

 

[Rich Grise]

I'm not sure about the origin of Q, but it is a military and
commercial standard.

I answered "Quality factor", and an ohnosecond later I realized
you're talking about transistors. I hope I cancelled the stupid
one in time.

As far as 'Q' for xsistors, I have no idea other than what I said
before - it was about the only letter left.

Cheers!
Rich

 

[Joel Kolstad]

D,R,C,L,Q
B (battery)
J (connectors)
X (crystals)
U (anything else)

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

 

[RST Engineering \(jw\)]

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.

Jim

 

[Joerg]

Neither have I (I believe this is about these squarish nonsense, I am
not sure I can even read that thing .

Indeed. When sitting in a design review it's hard to make out those
little & signs in the square boxes. I guess that's what they invented
binoculars for ;-)

 

[RST Engineering \(jw\)]

I learned it J (female connector, jack) and P (male connector, plug). Y is
crystal. X is tie point on a board. U is integrated circuit.

Ji

 

[Rich Grise]

we, as a rule, define the reference designator numbers following the
layout placement,
not the logical flow in the schematic.

The first input connector on the first page may get the ref des J9 !

They did this at my first job out of the Air Force. It's nice for
assemblers, but it drives techs nuts!

Thanks,
Rich

 

[Joerg]

Hi Jörg,



I agree, but in europe it's standard to use them.

Oops, didn't use them much over there either. Does that put me on the
wanted list now?

I prefer the good old too. But on the other hand what's about SI in
international use? This is the same here...

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.

But it can be mixed. When I inflate the tires of one of our cars I have
to re-calculate because the vehicle data specs PSI and the pump reads
atmospheres.

 

[Joel Kolstad]

They did this at my first job out of the Air Force. It's nice for
assemblers, but it drives techs nuts!

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.

 

[qrk]

Hmmm. I've just started doing this on a trial basis and I think it can
make schematics and BOMs more readable - as opposed to U1 - Uxxx. I'm
curious as to why you think it 'goofy'.

Bob

Because of industry accepted practices. When a competent technician
looks at your schematic, they'll figure you for some loonie toon. If
you do reviews with other engineers, they'll figure for a loonie toon
and figure you're a newbie.

In reality, if you want your schematic and BOM to be easily readable
by people in this field, it is best to stick with standard practice.
If your designs are assembled, tested, and maintained by others; new
nomenclature will confuse people. Believe me, when your on a ship in a
dim oily hold trying to fix some POS equipment, the last thing you
want to deal with is garbage documentation with non-standard symbols
and nomenclature!

However, if your documetation is only used by yourself, then it
doesn't make much difference.

 

[qrk]

Hello,

I have a quick question. I'm curious how industry typically presents
their *official* schematics. I've only really dealt with the design
end, and I use Orcad. I prefer to use net names on short wires on the
end of most of my components so that there is not a rats nest of wiring
on the schematic. I like my method for design, however, I don't think
net names on these short wires are acceptable for an industry standard
schematic, are they? Is the standard to connect all connections with
wires (sometimes creating a bit of a "noisy" looking schematic)? Or is
net naming OK? Or is there another type of connector ending that is
more acceptable?

What do you all that work in industry do for your "official"
schematics? Any examples would be great, or if there is a website or
somewhere to get more info, that would be awesome.

Thanks for your input!

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.

 

[Joel Kolstad]

Because of industry accepted practices. When a competent technician
looks at your schematic, they'll figure you for some loonie toon.

I'm not the OP, and I tend to agree that not using industry standard reference
designators does tend to look a little odd, but I realize it is just because
I'm used to the standard which is *largely arbitrary*. If I saw a schematic
using something "obvious" like LED1, I wouldn't assume the author necessary
was "looney," and I sure wouldn't hire a technician who would make a similar
assupmption either.

Back in college different professors had different symbol for the "excess gate
voltage," Vgs-Vt. In one graduate class, one kid asked about this, and the
professor (who had previously worked at Analog Devices) said that in his
experience, "every company has a different symbol for it anyway" (he preferred
"V\delta") so the kid had better get used to seeing it in different forms and
figure it out from the context.

I agree with the rest of your post -- if your schematic is being widely
disseminated, it's certainly best to try to be as standard as possible, but
within your own group, it doesn't matter and a case can be made for what the
group thinks is best.

---Joel

 

[Joerg]

Easy. More to the point, Q and U!

Quansistor and uintegrated circuit ;-)

Probably for no reason at all, like X-rated for movies. Whatever that
means, I don't what such movies anyhow. It's just a custom. Why change
it for no reason?

 

[Rich Grise]

But it can be mixed. When I inflate the tires of one of our cars I have
to re-calculate because the vehicle data specs PSI and the pump reads
atmospheres.

Well, multiplying by 15 should be easy, assuming your atmosphere gauge
gives you two or three digits of precision. At least be greatful it's not
in kg/m^2 or something! ;-)

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?)

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

Thanks!
Rich

 

[Rich Grise]

I'm not the OP, and I tend to agree that not using industry standard reference
designators does tend to look a little odd, but I realize it is just because
I'm used to the standard which is *largely arbitrary*. If I saw a schematic
using something "obvious" like LED1, I wouldn't assume the author necessary
was "looney," and I sure wouldn't hire a technician who would make a similar
assupmption either.

If a suitable BOM is included, it should be self-explanatory, albeit you
don't want to waste the tech's time making him/her look stuff up.

Back in college different professors had different symbol for the
"excess gate voltage," Vgs-Vt. In one graduate class, one kid asked
about this, and the professor (who had previously worked at Analog
Devices) said that in his experience, "every company has a different
symbol for it anyway" (he preferred "V\delta") so the kid had better get
used to seeing it in different forms and figure it out from the context.

I agree with the rest of your post -- if your schematic is being widely
disseminated, it's certainly best to try to be as standard as possible,
but within your own group, it doesn't matter and a case can be made for
what the group thinks is best.

I've always liked the style in Popular Electronics, which I don't even
know if there still is such a thing; and there's some engineer-level
trade pub that publishes schematics in a different style, but still
readable.

I think the main consideration is, be consistent throughout.

Cheers!
Rich