Standardized power symbols?

[Otso]

What are the proper power symbols to use? There seems to be multiple variations, especially regarding the positive voltage. I'd like an academic answer, not "just use whatever you like as long as it is consistent", unless that is the academic answer and then I'd like to know where that is defined. Is there any standard? I have spent some time searching, but haven't find any definitive source. IEC 60617 seems to define a triangle for ground (I can't fully verify as I don't have the standard which you have to pay for). But what should be used for like +5V in a circuit? A bar or an arrow seems to be most common, or a circle (less common). Where are these defined? I'm surprised it's so difficult to find any references, as practically every other basic symbol is very well defined with no variations (except for Europe vs US symbols, but that is also very well defined).

[EPAIII]

An academic answer? ??

In physics, the letter P is perhaps the most frequently symbol used for power. But I am sure others have also been used.

In electronics the same letter is used in equations, but perhaps you are really referring to symbols used in drawings. That brings up the type of drawing you want. And exactly what you mean by "power". In electronics there are schematic drawings, wiring diagrams, pictorials, and then styles like "fritzing" and each of them can use different symbols.

A pictorial type drawing will often try to make the symbol for something look a lot like the actual item. So a battery would be drawn looking like a physical battery and different types of batteries would have different appearances. A plug for the power cord would be drawn to look like the plug found on a living room lamp of kitchen toaster. Etc. This is the type of drawing that is often used for beginners so they can relate to the item.

Wiring diagrams are more abstract. Often AC or DC power is brought into the diagram with simple rectangles or open arrow heads with text in them to show the type of power. They can even have just a line, which represents a wire, starting next to such text. The text may be very descriptive (230 VAC, three phase, 100 Amps) or very abbreviated (phase 1, phase 2, L1, L2, etc.)

Schematic diagrams are highly abstract but also highly organized (at least they should be) to allow the function of the circuit to be shown by that structure of the drawing. An important element of this is signal flow from left to right and top to bottom. So Power should be introduced into a schematic drawing at the left and/or top with standard symbols in those locations. Additional symbols can then be used to distribute those power sources around the drawing as needed. Different types of power will have different symbols. A circle with either plus and minus signs or a sine wave inside can be used for DC and AC power. A connector symbol - there are many types - can also be used. Like the wiring diagrams; boxes, open arrow heads, and even the end of a line with text can be used. And again, that text can be very descriptive or very abbreviated.

In schematics and wiring diagrams I have seen a large amount of different ways of showing almost every element that is included, including power symbols. My examples are by no means intended to be all inclusive.

"Fritzing" is a very stylized version of the pictorial style of drawing. It uses actual photos or very accurate drawings of the actual items. In this it is, perhaps, the easiest of all to define. Take a photo, reproduce it close to actual size and you have your symbol. I hate "fritzing" because it does nothing to make the circuit understandable. It only shows what it looks like and it only does that for one set of parts: if your part looks different, TOUGH.

You ask for standards. I am afraid there are many and there are none. Virtually any country, industry, company, group, or even individual is free to use whatever standard they wish. Pseudo standards have jelled around loosely defined groups for loosely defined time frames. Companies have published their own standards. Different industries may use different styles. Etc. So, NO there is no real, universal standard for power or any other of the symbols we use. I am afraid that is not very academic. Or, perhaps it is.

And I will give you one very big reason why there are no universal standards: $$$$ and exclusivity. The people who usually develop and try to propagate standards first, do not include the potential users in the considerations. And second, they always want large amounts of money for copies of those standards. None of them ever seems to understand that if they want people to adopt their standards, then those PEOPLE need to be a part of the development process and then actually know what the standards are. But they exclude most users and then assume that all users can afford their arbitrarily high prices. This is a double formulae for failure and it seems to be practiced by, guess who (hint, hint: a  c  a  d  e  m  i  c  s).

If you want "academic" standards, then, INCLUDE ALL users in their development and maintenance. And make them completely FREE to all who want them. Oh, and no copywrite: anyone can reproduce them. Then, and only then, will you ever have real and universal standards. But you and I both know that is not the academic way because it does not force the "superior" knowledge of the few on the masses.

Personally, I like it the way it is. And if the academics don't like it, then #### them if they can't take a joke.

[Otso]

Thank you for your long reply. As you guessed, I didn't mean Power (P), but power supply voltage, and the symbol used for that in electrical schematics (Although I used the wrong term , I think it was clear from the context of my question). Further I'm referring to voltage used in extra low voltage systems (< 120VDC, but practically I'm thinking of schematics for consumer devices that are typically < 30V), and especially DC voltage. I think everybody understands what I'm getting at.

I wonder how practically every other symbol in a schematic looks the same, regardless of who does the design, and those are more or less identical to those defined by IEC, like, for example, these https://en.wikipedia.org/wiki/Electronic_symbol.  The only exception seems to be symbols for DC power supply voltage and common ground (not earth), and these vary a lot (again, unlike every other symbol, or so it seems to me). Why is this?  Or is it just me? I'm just hobbyist with not much experience, but I'm sure I've looked at well over a hundred schematics, and there's a huge variation in the symbol used for power supply voltage (unlike other symbols, where the only difference is US vs european symbols).  And further, basically the symbol can indicate common ground in one schematic and positive power supply voltage in another (a bar).  I find it hard to believe that there is this much variation with any other symbol, at least for the devices/functions that you would typically see in a modern schematic. If there are variations, I claim that they are subtle compared to the power supply voltage symbols. (I'm sure you can find strange symbols, but I say you'd be pretty hard pressed.)

So I was wondering, is there any symbol that is standardized by any generally accepted standardization body? What does IEC define, if any? What do they teach you to use in university, and what literature do they refer to?

If there's no answer to this. Is there any symbol for extra low DC voltage that is dominant in the European industry?

[Benta]

There is no standard. Each company uses its own power symbols according to "Corporate Identity".
The only exception is "Protective Earth" or PE, which is recognized/mandated internationally.

[Otso]

It would be fun if every company started defining their own resistor, capacitor, transistor, diode, op-amp etc symbols as part of their “company identity”. /s

[Otso]

An academic answer? ??

Yes, that's what I said. To me an academic answer is objective, provides sources, is verifiable, theoretical and based on facts that there is a general consensus among the experts and professionals in the field. As opposed to the non-academical answers that you often get on the Internet, that are purely speculation, subjective and provide no sources to the information. I gave an example of such an answer "just use whatever you like as long as it is consistent".

In physics, the letter P is perhaps the most frequently symbol used for power. But I am sure others have also been used.

If you don't know what IEC 60617 is, that I referred to in my question, then please don't waste your time answering.

I feel the main purpose of your long reply was to mock my question. I hope I interpreted it wrong. Or maybe you stopped at "academic" and thought it was so funny that you spit the coffee on your shirt and then forgot to read the rest.

[temperance]

An engineer we just hired looked at my schematics and the 0 V symbol used by me is a small triangle. The engineer in question went on to report to management that I used the wrong symbol for GND (he called it GND and technically GND is not 0 V) and according to him the correct symbol to use is the one reserved for earth... That's when you know you're dealing with an idiot.

[abeyer]

To me an academic answer is objective, provides sources, is verifiable, theoretical and based on facts that there is a general consensus among the experts and professionals in the field.

That doesn't really mesh w/ my real world experience with academics in matters of notation and standards. They seem to love to make up their own notations, even if they don't align to industry standards. (The best are the ones who make them up on the spot in lectures and then forget what they meant half way through... I've seen a few of that type.  )

If you don't know what IEC 60617 is, that I referred to in my question, then please don't waste your time answering.

If you just wanted someone else to pay for the standard themselves and look it up for you, you should have said so. 

I feel the main purpose of your long reply was to mock my question. I hope I interpreted it wrong. Or maybe you stopped at "academic" and thought it was so funny that you spit the coffee on your shirt and then forgot to read the rest.

I don't think anyone's mocking you, but I think your question isn't well formed or well presented though, so isn't likely to get useful responses. (and I think what you really want is something to point to and say "this is the one true symbol, all the rest of you are WRONG!" and I don't think you're going to get that, and even if you did it wouldn't do you any good.)

[donlisms]

There will only be standardization within small circles of artists, I think partly because of you can read schematics, it should be fairly obvious what's what.  Clues abound, eg that this node seems to be floating in space, labeled with a voltage.

If you expand your domain to include older schematics, the farther back you go in time, the more variation you're going to see, not only in power supply indications, but ALL aspects of schematic conventions.  Symbols, nomenclature, the whole left-to-right top-to-bottom thing, dots or no dots at connections... you'll go bonkers unless you apply lots of intuition and other forms of brain power. 

When you're drawing a schematic, use the convention most like those you're presenting it to, statistically speaking, or just pick the approach you think is most clear. 

If you have the kind of personality or ideology that tends to seek a perfectly-ordered world - and I'm not judging or anything - I suspect the reality of this particular aspect of it might bug you.  Not everything is standardized, and that's not always a tragedy.  It keeps life interesting and perhaps even challenging.  Little remnants of personal choice, which seems to be diminishing every day.  So I like a line with a signed number on it. I don't care who else likes or uses such a convention.  I've gotta be me.