1
\$\begingroup\$

What's the protocol for updating a schematic? I have 4 diodes creating a bridge rectifier on an existing schematic that I was going to replace with a single part.

For example, if those diodes were named D1, D2, D3, and D4, should I annotate that new, single part as D1, or leave those values blank, and pick up at D5?

I know I can do whatever I want, but I'm curious if a protocol is generally followed here.

\$\endgroup\$

3 Answers 3

Reset to default
3
\$\begingroup\$

From an professional engineering and manufacturing perspective, it depends on whether the previous schematic's board was manufactured.

If it was manufactured, don't re-use reference designators. Delete D1..D4 and don't use them again, use a new refdes. That prevents confusion for any staff in development, component procurement, stock control, production line, test and field service, who were using the old version and must work with the new one.

For example, service manuals that said 'check the voltage across D1' could now find a different part doing a different job. I've worked with a good number of production test staff assembling boards into the equipment, service engineers out there fixing this stuff against the clock, in many companies over a long time. They get to know certain parts for test to diagnose common failures etc. Changing that in the next board revision disrupts that knowledge, very pointlessly as there's no benefit: there's no shortage of new refdes numbers to use. Why not choose the the path that eliminates any chance of that confusion.

If it's not been manufactured, drawing released or left your PC before, you can re-use the refdes.

Regarding the refdes to use, it's not a single diode so not 'D'. People used to use 'BR' and many still do. (I don't see 'U' normally used but that's my subjective experience.)

\$\endgroup\$
5
  • \$\begingroup\$ If you had documents referring to D1-D4, then the board rolled to use a bridge, the docs would need updating regardless of whatever you called the bridge. In the old days of paper docs this was painful; these days it’s not so difficult. \$\endgroup\$
    – hacktastical
    Commented Jun 24 at 19:45
  • \$\begingroup\$ @hacktastical, ease of updating the paper is irrelevant. For example, production/service people will learn certain tests across certain parts for fault-finding, they won't keep referring every single time to the latest docs. It's adding unnecessary and pointless confusion to change those parts' function on up-rev'd boards by reusing the refdes. Reusing's not saving anything, there's no shortage of refdes. The system used should work for the entire crew right across the organisation, it's not just a whim of the board designer, whose work is only a small part of it all. \$\endgroup\$
    – TonyM
    Commented Jun 24 at 22:00
  • \$\begingroup\$ In the big picture, changing from 4 discrete diodes to a bridge as the only change, without, say, reducing the form factor, is kind of pointless. It would not pass muster with a change committee due to back end costs, especially if there is an inventory write-down on the discrete diodes the bridge is to be replacing. That aside, what about the refdes question? In my experience with contract manufacturers, no one cares about refdes changes, so long as accurate docs (BOM, schematic, etc.) are electronically provided with the change package. \$\endgroup\$
    – hacktastical
    Commented Jun 25 at 0:08
  • \$\begingroup\$ @hacktastical, (don't shout in bold, it reads worse) You're off-topic, your example is about a much smaller group than I've repeatedly described. Mine's from long and listening experience working co-operatively with production assy/test staff, service engineers in many companies; it's not my opinion. Anyway, my experience/observations won't change, and you'll not, so let's leave it there. \$\endgroup\$
    – TonyM
    Commented Jun 25 at 16:38
  • \$\begingroup\$ You labeled my counterpoint about paper "irrelevant", then double down about how downstream stakeholders "won't keep referring [] to the latest docs". That argument would be supportable if the docs were paper, like they were in, say, 1985 (so it's very relevant.) That's not the connected world we live in now. As to my point you labeled "off-topic", I'm actually agreeing with you that changes shouldn't be at the whim of the engineer: other stakeholders weigh in on change approval. Would they reject an ECO because of a reused refdes? They could reject for other reasons, but not for that. \$\endgroup\$
    – hacktastical
    Commented Jun 25 at 19:54
1
\$\begingroup\$

I have seen several abbreviations of the words "diode bridge" used for the reference designation for a diode bridge as a single element.

I have also seen U being used as it is a collection of elements within a package, like an integrated circuit.

KiCad uses D as the designation, so this is my preference.

\$\endgroup\$
1
\$\begingroup\$

Probably best to just call the new bridge part D1, and remove designators D2-D4 on the revised schematic.

Your other option is to find your highest diode reference, and make the new bridge one higher than that. If for example your present highest is D7, then your new part would be D8.

Either way you avoid a reference clash with your other diodes when you make your new bill of materials. That’s the only thing that matters, really.

\$\endgroup\$

Not the answer you're looking for? Browse other questions tagged or ask your own question.