How are *official* schematics presented?

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

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!)

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.)

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

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

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

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

Crystal Rectifier?

martin

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

Easy. More to the point, Q and U!

Tim

-- Deep Fryer: a very philosophical monk. Website:

"Crystal rectifier", from the early days.

Michael

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

John

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

They were the only letters left? ;-)

Thanks, Rich

...]

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

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.

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

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

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.

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.

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'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

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

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.

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

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.