There’s a ton of power symbols available, just the ones with “+12” are:
+12C
+12L
+12LF
+12P
+12V
+12VA
but I can find no explanation for what all these names mean other than the I assume obvious +12V. Indeed I haven’t found them used anywhere. Do these have standard and well known meanings in electronics design, and if so, what are they?
Power symbols are still a bit of a kludge in KiCad.
The underlying problem is that KiCad derives a global label from the pin name of the power symbol, and that is not editable in Eeschema itself. The text of the pin name is also hidden, and the text you see of the power symbol is the “value” field, and this has been made read-only. This is a kludge on a kludge.
As a result, a long time ago a bunch of these power symbols ended up in the symbol libraries, and usually you find something there that is “mostly adequate” for your project and use it without giving it much thought.
The current situation is “workable”, and most people who have used KiCad for a longer time have probably gotten used to it, and I’m guessing that it therefore it has a low priority.
A real solution is to make the text itself editable… I think this is already planned for the next KiCad version.
I know that, but that wasn’t my question. What I want to know is, what do those names mean? Or do they have no meaning to anyone but some person back in 1997 who created “+12LF” because their girlfriend’s name was Lola Fran?
On this forum I see a lot of questions about symbols in the standard libraries. I include your question in this category. My take is that the standard library is only a suggested starting point and should not be taken too seriously. There is a good chance that those names were ones which sounded good at the time to the person who defined them. Most of us will not know what somebody had in mind when they established some of these net names. Heck, when I look back at something I did months ago, even if it works nicely, I scratch my head and wonder what the heck I was thinking. I have been engineering since 1975 and one takeaway is that for every useful standard that has succeeded there are ten which have fizzled and resulted in a confusing mess. Look at various types of BAT54 diodes in different packages from different manufacturers as one example, or variations of surface mount IC packages and their names as another bigger minefield. So if you like a given power symbol naming convention and can defend it to any people who will need to accept it, I think that you are ready to use it.
+12V - Digital 12v positive rail
+12VA - Analogue 12v positive rail
(In some circuits, there may be a mix of Digital and Analogue, and these may use different power rails, thus 12V vs 12VA)
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