Eagle library editor

1234567AB,

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board. If

We don't do that. We only change the schematic when we rev the PC board. An ECO tells manufacturing (or test, or a customer) to change the resistor, but we don't issue a new schematic. If it's a permanent change, the BOM is updated and "ECOxx incorporated" noted.

Every schematic says "Engineering Change Orders May Apply."

John

1234567AB,

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board. If

Even in the days of the paper computer this worked very well. As I said, the document number and rev level of the underlying schematic is written _into_ the very file that releases the bare board. So all I ever had to do in older organizations is go to the doc center, ask for the 1045-7853 Rev A file, look up the underlying schematic, ask them whetehr they could please pull that for me as well, and whether I could have one of those mint cookies from the bowl.

In more modern organizations this can all be done from the screen with programs such as Agile. That method has less calories but also less exercise.

Ok, >50% of my jobs are in highly regulated industries where what I described is pretty much mandatory. But sheltered I am not, due to being a consultant I get around a lot. Start-ups often need some help in that domain so I give them hints how to build up their doc system.

So let me repeat the question. Say one of your guys finds out that 12.1k is too low and R92 needs to be 14.3k. What happens next? Do you not change the schematic to reflect that change?

That's a bit surprising. Normally they control all the document numbers and such.

Ok, just don't build any med gear that way because that won't fly there.

But above you wrote "They wouldn't even document this on drawings". To me that sounds like the respective ECO wasn't written, because there is no reference on the drawings.

--
Regards, Joerg

http://www.analogconsultants.com/

1234567AB,

everything in

just be

versus

board. If

Do you not update the schematic?

--
Regards, Joerg

http://www.analogconsultants.com/

1234567AB,

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requirement.

Not in a controlled document. No. The BOM is the controlling document for an assembly.

worth writing home

Most chip design is

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A dash-number or different number are pretty much the same thing.

I can imagine. I have enough trouble keeping my documentation straight, before release. I have working drawings and spreadsheets that I *know* are out-of-date. I hate to purge them, though.

Disaster recover must have been an interesting topic.

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Then I would not want to be a service guy in your company. Or working in final testing. Not having a schematic with the correct part values in there is IMHO quite horrid.

--
Regards, Joerg

http://www.analogconsultants.com/

(the

1234567AB,

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#1234567A.

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board. If

not

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There may be reference drawings (there are assembly drawings) with the latest values but none under ECO control. It's done to protect the integrity of the ECO system. Only one document is the source for any data. If two are allowed, they won't agree. ;-)

1234567AB,

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I remember the doc center, waiting at the Dutch door. We'd sing "Some Dayyyy my Printsss will Come..."

But they had a drop acoustic ceiling, as did the stock room, so we'd sneak in at night.

But nowadays the schematic creates the PCB, so they have to be tightly coupled. A schematic used to be a "reference drawing" but now it's a controlling drawing.

And we don't have a doc center, or anybody full-time dedicated to document control. No more typists, either.

No. A released drawing rev is never changed. We'd write an ECO to the assembly, and usually direct that the BOM be updated to reflect the change for future production. If it's a one-time thing, we wouldn't change the BOM, but just indicate which serial number to apply the fix to.

We do what we like. If people don't want to buy it, they can go somewhere else.

I hired one guy, once, from a big-name medical supplier. Some tech had new boards and RMA boards on the same workbench when the inspectors showed up. They shut down the facility. My guy had been working on upgrading procedures for almost a year, to get recertified, no new design, and couldn't stand it any more.

The mirror image thing? Everybody just knew that.

A drawing defines the -1 assembly unless stated otherwise. And the -2 mirror image, too! Except we don't build airplanes, so we use dash numbers sequentially.

John

1234567AB,

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will just be

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requirement.

I wouldn't allow an auditor in the front door.

Actually, a few big companies have asked us for our documant and quality procedures, but nobody has objected to anything so far.

I explained our PCB rev system to the gigabuck OEM customer, the ones who use Agile. They were impressed by its clarity and simplicity.

John

worth writing home

Most chip design is

shapes are defined by

Ok, with the

mere

potato chips

the schematic he

unravel at

Fremont, to

G. The PCB

nothing matches

one. Rev

should not be

schematic wasn't ECOed

in and a separate

were done in BOMs,

products were

denote the

the parts

assy? That

good bare

number. There

each using the

(which calls

there are

instructions in the

obviously

...a

schematic?

linked.

bare

to

board

controls

products

forever

components

bother. The

1234567AB,

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I draw my schematics on D-size vellum, bacause there's no way to lose a piece of paper that big.

When a board is in engineering, destined to become, say, rev B, we call the schematic file 22S123_B1.SCH, and the PCB is 22D123_B1.PCB.

If we change something we rename the schematic 22S123_B2.SCH. PADS creates a forward ECO file, comparing schematic _B2 to _B1. We name that 22S123_B2.ECO, and apply it to the PCB to get 22D123_B2.PCB, and so on. Our record is about 50 such revs, but 10 or so is more normal. We do reverse ECOS that way, too, like for pin swapping or resequencing.

Ownership often changes hands during the process, like if I take a board home for the weekend to tweak it.

It's finally released as rev B, no numbers after the letter. BOM file

22A123.1B creates assembly 22A123-1B.

John

1234567AB,

everything in

will just be

versus

board. If

requirement.

At one company it was a pretty princess. But I was already engaged so ...

That's usually the moment where two snarling Dobermans show up.

Well, as I said your company and it seems Keith's are the only ones I've so far heard to have a lock-step rev level requirement. Which makes no sense to me. But you da boss :-)

Yikes, scary. So I guess if a guy grabs a schematic to diagnose a problem there is a little imprint saying "Values in mirror might appear smaller than they are on the BOM" :-)

[...]

It's the same in aerospace. Procedure writing is really big there. And woe to those who don't stick to those procedures. Sometimes it might seem silly. But, for example, if some navigation stuff errors because the BOM value of a part was different than in the schematic, someone tripped up on it and something happened, then there will be a whole bus load of inspectors swooping in.

Some people get used to all this overhead, some don't. I did :-)

I actually found it not that foreign because it is very similar to how things worked in the military when I served.

Well, you da boss :-)

--
Regards, Joerg

http://www.analogconsultants.com/

...still with you.

Right. There is no control if a drawing can be changed.

to reflect the

The ECO gets written assembly *TO* change the BOM. The BOM is the controlling document for the assembly.

For a one-time thing, use a deviation. ;-)

(the

second 1234567AB,

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not

CAD

a

requirement.

design.

BOM

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Schematics as uncontrolled documents? Now it gets really scary. IMHO that is a recipe for some major boo-boo in the future. I have seen those happen because of uncontrolled schematics.

--
Regards, Joerg

http://www.analogconsultants.com/

(the

1234567AB,

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will just be

#1234567A.

versus

board. If

not

requirement.

BOM

They are free to keep a private redline copy around. They usually do, with notes and such. If there's any doubt about a value, the defining ECOs and BOMs are online.

John

(the

1234567AB,

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not

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In med electronics that would be the end of your company. They'd go away alright but later come back with cruisers, chains and pad locks.

Hasn't happened with my little office in a long time. But it did many years ago. My impression was always the same: They were obligated to ask because it was procedure, filed my response and nobody ever really read it. Just like the Health Care bill.

Going by what's you've said about these guys that isn't exactly a very good endorsement. More like Barney Fife saying "Oh yeah, this is a really good gun!" :-)

--
Regards, Joerg

http://www.analogconsultants.com/

(the

second 1234567AB,

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may not

CAD

have a

requirement.

design.

and

a BOM

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How so? The schematic is the input to the layouter and the BOM. It

*controls* the process. The problem us *uncontrolled* schematics. The first step in a board ECO process is to fetch the schematics from the documentation system. The ones in engineering can't be trusted.

(the

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#1234567A.

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not

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Under what legal authority?

But the point is, we don't design electronics to meet anybody's standards but our own. If anybody doesn't want to buy it, let them find something better.

John

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second 1234567AB,

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may not

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for an

Ok, so to repeat my question: What happens in your company when R92 changes from 12.1k ro 14.3k? What is the process from A to Z? Above you said the controlled schematic does not get updated. Which one does? Or none does and everyone involved has to "kind of know" that it may not be current?

--
Regards, Joerg

http://www.analogconsultants.com/

(the

second 1234567AB,

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will just be

#1234567A.

versus

board. If

not

CAD

a

requirement.

design.

BOM

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Very scary. I would have never allowed that at our company. But I couldn't have anyhow because we were a med devices biz. If the Federales would find one such hand-redlined copy anywhere outside of engineering ... slam-bam ... padlock ... everything stops.

--
Regards, Joerg

http://www.analogconsultants.com/