Layout Symbol - move Polarity indicators in PCB  - Page 1
Forum section: electronics / general

author: Andree Henkel
author_rank: Regular Contributor
timestamp: August 02, 2022, 10:12:14 am
content: Hallo, is there a trick, that you can design a layout symbol in eagle such that you can move its polarity indicator (of a electrolytic cap) or pin 1 indicator for IC in layout?Like you can move the designator and value?

author: jpanhalt
author_rank: Super Contributor
timestamp: August 02, 2022, 10:58:34 am
content: QuoteTypically, those identifiers are in the "device" and are part of the design of the package or symbol. You can move them in the appropriate editors, but not when working on the schematic or board, so far as I know. See attached example (symbol). In other words, the device is "fixed."Edit: On further thought. You could omit the polarity from the symbol and include it with name or value, but that may look odd.Edit2: If you delete it from symbol or package and add as text to the PCB, it might accomplish what you want. I would be sure it didn't mess up ERC.

author: Feynman
author_rank: Regular Contributor
timestamp: August 02, 2022, 09:35:07 pm
content: Changing polarity indicators in the design seems like a very error prone activity. I don't know how your library is organized or who is assembling your board. But polarity indicators are already a popular source for trouble. Even without such hacks you need to be extra careful with these.I'm suspecting there is a better solution for whatever problem you actually want to solve. It's called "library" for a reason

author: jpanhalt
author_rank: Super Contributor
timestamp: August 02, 2022, 10:07:41 pm
content: Since the OP has not responded, I assumed the reason was to put the polarity sign in a more convenient place on the PCB, just as one rearranges names/labels to be readable. I concur that one needs to be careful. Eagle only allows limited choices for pins (attached). For polarized caps, the choice is passive, which means Eagle ignores the "+" sign. It is just like any other text. I suggested ERC, but I suspect that would not catch a cap labeled backward.In any event, if it is just for convenience, I can see occasionally wanting to do that, but I would make it an alternative device of the same name. Nevertheless, there apparently is a way to do it.Eagle may be woefully dated by current standards, but I have rarely if ever wanted to do something that I could not do with it. My version are 7.x.

author: Andree Henkel
author_rank: Regular Contributor
timestamp: August 09, 2022, 08:08:47 am
content: Yes, making an individual layout symbol for this instances works.But that is actually what I wanted to avoid.I have been tasked to create guidelines for our internal eagle library, so I wanted to find a way to do it.Thanks anyone.

author: jpanhalt
author_rank: Super Contributor
timestamp: August 09, 2022, 09:09:26 am
content: Any you seem to have ignored my other suggestions, which also work.Good luck.

author: Feynman
author_rank: Regular Contributor
timestamp: August 09, 2022, 06:00:45 pm
content: Having 100% distinctive polarity indicators is the job of an assembly drawing, where only component outlines, polarity indicators and reference designators are plotted (plus some optional features, e. g. PCB outline, drills, solder pads, ...). There is a special layer dedicated to the assembly drawing in many libraries. But this depends on the CAD tool, of course. When I worked with EAGLE a while ago, I used the tDocu-Layer for assembly drawing features.Making individual layout symbols appears like a maintenance nightmare to me.Leave it at one footprint, place the polarity indicators where obfuscation is unlikely and add features that allow you to produce a decent assembly drawing.