Yes, mounting holes do vary, and I’ve seen three variations (some annoyingly close!) for the size that I am interested in. I am not saying there Can Be Only One footprint, but currently there’s just mismatched guff.
Of course you need to make custom footprints with respect to mech details - because DIN didn’t standardise those in this case - but IMHO it should not be too much to ask to have a standardised pin numbering for each of the windings for example, because that means you can use a single symbol for all the different mech and layout variations.
The relay libraries in KiCad are mostly good this way - huge variation in footprints of course, but there are a few Forms that are standardised and it seems to be possible to match up a symbol with a number of different footprints in the same Form because there is common pin numbering.
Anyway, this is not a whinge, I just thought there was some feature of kicad I might be missing and which was expected to be used to map between symbol and footprint pin numberings.
Having correct pin numbers in the schematics would be an advantage, I agree with that.
However, as I wrote before, that series of transormers has variants with 10, 12 and 14 pins. Combine that with single and dual secondary windings already makes 6 variants, which is doubled to 12 if you also include options for a single or dual (2x110V) primary windings, and with 2 or 3 variants of the secondary windings easily doubles that again.
With KiCad-nightly V5.99 schematic symbols are saved in the schematic itself. That means that changing pin numbering of a transformer is as easy as depressing [Ctrl + e] while hovering over the transformer, selecting the pins of interest and changing the numbers. Would having 20+ different schematic symbols for these transformers really be beneficial? In either case you have to verify what you put in the schematic with the actual hardware or datasheet, and the verification probably takes more time then either the selection from one out of 20 or the pin number change. Both methods are pretty trivial.
It’s also a good example of wanting to have personal libraries. Once you’ve either selected (or changed pin numbers) of a transformer you use often, you can put it in a personal library (with the right footprint already linked) and after that you do not have to verify it anymore.
And that is where the time saving can be. With good verified personal libraries. Not with 20 very similar library symbols.
When you sit down and wind a transformer it is very instructive. (seriously). You often find that what you thought was a logical way to wind it is not what works best in practice. And there can be a lot of nitpicky details (such as which windings are more closely coupled to which) that might vary between one transformer and the other. This all works against standardization.
I have never thought of using 3D models until I started to use KiCad which in the package gives you 3D models. I use them only to add semi-photo of my PCB to documentation pdf.
- but IMHO it should not be too much to ask to have a standardised pin numbering for each of the windings for example, because that means you can use a single symbol for all the different mech and layout variations.