How are *official* schematics presented?

[Andrew]

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!

 

[Joel Kolstad]

I have a quick question. I'm curious how industry typically presents
their *official* schematics.

Who are you presenting to? Most schematics these days are never seen outside
of the engineers working on the product and some service personnel.

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?

Just a wire dangling out there in space does look a little odd, in my
opinion... this is why all the schematic capture packages have "off-page
connectors" so that it's clear you didn't just forget to hookup the wire in
question. (In fact, in many cases default design rule checking will flag a
"floating" wire like that as an error!)

Is the standard to connect all connections with
wires (sometimes creating a bit of a "noisy" looking schematic)?

It's a balance for most people. After all, almost no one actually shows wires
running around for VCC and Gnd, right? So it's perfectly reasonable to use
"hyperspace ports" (as a former co-worker of mine called them) to do likewise
with other common signals. (Actually, said co-worker disliked hyperspace
ports as well as multi-page designs, so he'd typically end up with some giant
D-sized sheet with a million wires running everywhere. Not my preference, but
for his own schematics I wasn't complaining.)

For logically related signals, busses are another good way to tidy up your
schematic. (Although ORCAD unfortunately has somewhat limited bussing
abilities compared to most products.)

Or is
net naming OK?

Net naming is generally a Good Thing in all cases. It helps people to not
"get lost" when they're looking at a stack of a dozen wires all right next to
each other, and it also helps the PCB layout guy know whether he's routing
something "important" or not (especially in the case where you aren't getting
fancy and assigning nets to classes -- e.g., power, signal, clock,
differential, etc. -- that are passed on electronically to the layout tool).

---Joel

 

[Eeyore]

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?

It's fine by me.

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?

Lots of wires and busses can actually make a schematic look very messy. Where
various signals do make a 'bus' though, it's good practice to show this.

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.

I do it like you it would seem.

Graham

 

[John Larkin]

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!

We use "offpage connectors" a lot, even on the same page, to avoid
long ugly wire runs. I dislike busses and overstrike/underscore/long
net names, but that's just me.

What I hate is a named net that exists on multiple pages with no
obvious offpage indication. Schematic entry programs simply shouldn't
allow that.

But there is really no "official" schematic format, just some acquired
lore and a heap of different styles. Some people even make up goofy
nonstandard reference designators, like TR5 (for a transistor) and
LED1 and IC4 and RV1.

I'll post something to s.e.d. if I get around to it.

John

 

[Bob]

Some people even make up goofy
nonstandard reference designators, like TR5 (for a transistor) and
LED1 and IC4 and RV1.

I'll post something to s.e.d. if I get around to it.

John

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

 

[Richard Henry]

On 24 Jan 2007 10:34:56 -0800, "Andrew" <[email protected]> wrote:

But there is really no "official" schematic format, just some acquired
lore and a heap of different styles. Some people even make up goofy
nonstandard reference designators, like TR5 (for a transistor) and
LED1 and IC4 and RV1.

Which reminds me - why "CR" for a diode?

 

[martin griffith]

Which reminds me - why "CR" for a diode?

Crystal Rectifier?


martin

 

[John Larkin]

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

Well, they look goofy to me because they do.

There are accepted MIL and industry standards for ref designators, in
the handbooks, and it looks amateurish when I see people making up
stuff like CHO2 because they think an inductor is acting like a
"choke" or ZEN5 because a diode is used as a zener. And it makes BOMs
ugly (variable length desigs mess up nice alignment of the refdes
fields) and can really wreck PCB silkscreens.

Does anybody out there use IEC logic symbols? That's *really* goofy!

John

 

[Tim Williams]

Crystal Rectifier?

Easy. More to the point, Q and U!

Tim

 

[Michael Black]

Which reminds me - why "CR" for a diode?

"Crystal rectifier", from the early days.

Michael

 

[John Larkin]

"Crystal rectifier", from the early days.

Michael

And D was "dynamotor", the original solid-state dc/dc converter.

John

 

[Eeyore]

Some people even make up goofy nonstandard reference designators, like TR5
(for a transistor) and LED1

What do you use for an LED ? CR ?

and IC4 and RV1.

Yes, that's exactly what I do . Things like D7 rather than CR7 too !

Do please explain the logic behind the usage of Q, U and CR

Graham

 

[Rich Grise]

I heard "contact", but whatever. ;-)

Easy. More to the point, Q and U!

They were the only letters left? ;-)

Thanks,
Rich

 

[Joerg]

John Larkin wrote:


....]

sorry, the key for the left bracket just croaked. Dang.

Does anybody out there use IEC logic symbols? That's *really* goofy!

I used to but only when clients insisted on that. Surprisingly it
happens less and less. Right now it's all US. Luckily my CAD has almost
all the parts in both versions but yes, the IEC symbols do look goofy.

 

[John Larkin]

What do you use for an LED ? CR ?

It's a diode. D. We don't use a lot of surface-mount dynamotors these
days.

Yes, that's exactly what I do . Things like D7 rather than CR7 too !

Do please explain the logic behind the usage of Q, U and CR

Graham

It's not logic, it's convention. You can make up your own symbols for
physical constants, and chemical elements, and decimal prefixes, if
you want to, but the average scientist would think you were a stark
amateur, or else a classic British eccentric.

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.

Since I'll probably never see your schematics, and absolutely not copy
them, call things anything you like, POT2 and CON5 or whatever
pleases. I occasionally share my schematics with serious scientific
and aerospace customers, and I don't want them to think I learned
electronics from Audio Amateur Magazine.

John

 

[Richard Henry]

physical constants, and chemical elements, and decimal prefixes, if
you want to, but the average scientist would think you were a stark
amateur, or else a classic British eccentric.

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.

Since I'll probably never see your schematics, and absolutely not copy
them, call things anything you like, POT2 and CON5 or whatever
pleases. I occasionally share my schematics with serious scientific
and aerospace customers, and I don't want them to think I learned
electronics from Audio Amateur Magazine.

Q because it has a faint resemblance with the schematic symbol?

 

[Marte Schwarz]

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

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

Marte

 

[Eeyore]

Hi Jörg,

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

It is ?

I've never used one even once.

Graham

 

[PeteS]

What do you use for an LED ? CR ?



Yes, that's exactly what I do . Things like D7 rather than CR7 too !

Do please explain the logic behind the usage of Q, U and CR

Graham

U is used because it's the shape traced if you follow pin numbers from
1 to n (where n is the last pin); at least that's the possibly urban
legend I heard, but given the methodologies I've seen for choosing
various symbols, it seems reasonable.

Cheers

PeteS

 

[Didi]

I've never used one even once.

Graham

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

Dimiter