Ground symbols, what is what

[Efcis]

@Seth_h

PS: @Seth — are you the same Seth that recently posted the reply to my “grounds” question on electronics.stackexchange?

Yup. I get around

Your reply should be added to the FAQ of this forum

[Rene_Poschl]

The reply is very well thought out and very nicely formatted.

I have however a few comments about some details

In KiCad, all ground symbols are designated as “Power Output” terminals.

The power symbols are invisible power input pins! This makes them a global label. In addition to this ERC will then check if another pin on the same net is a power output. (If no power output is on the same net you get the error “pin connected but no pin to drive it”)

They also have a special power flag (note the reference “#PWR” in each of them). This creates a global label for your circuit with the name of the ground.

This is also not quite right. The # at the beginning of the reference ensures that this symbol is not added to the bom or connected with a footprint.

I am not sure if the reference must be PWR. My guess is it can be anything really.

There is however a “this is a power symbol” flag in the symbol definition. If i remember correctly then this flag is used to identify libraries that should appear in the “add power symbol” dialog.

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Sadly i can not add a comment to this answer on stackexchange as i do not have enough reputation. @Seth_h could you look into these comments and fix your post over at stackexchange? (I will then happily link it from the FAQ index thread)

[Seth_h]

@Rene_Poschl

Sadly i can not add a comment to this answer on stackexchange as i do not have enough reputation. @Seth_h could you look into these comments and fix your post over at stackexchange? (I will then happily link it from the FAQ index thread)

Thanks Rene! Good catches, all.

[pedro]

@Rene_Poschl

There is however a “this is a power symbol” flag in the symbol definition.

Exactly. The “P” of the last item stands for Power

DEF 5V #PWR 0 0 Y Y 1 F P -> Power symbol

DEF R R 0 0 N Y 1 F N -> Other than power

@Rene_Poschl

If i remember correctly then this flag is used to identify libraries that should appear in the “add power symbol” dialog

Nearly. It is not to identify libraries but symbols. If the library has mixed power and “normal” symbols, the add power symbol dialog will show only the power symbols no matter which library they belong to.

[Rene_Poschl]

Something else: The ? is not part of the reference. It is only rendered by the symbol editor (If you edit the field you will not see the “?”)

[Seth_h]

@Rene_Poschl

The ? is not part of the reference. It is only rendered by the symbol editor (If you edit the field you will not see the “?”)

That should just be replaced by the numerical value when annotating.

[Rene_Poschl]

The way you write it might be interpreted that one needs to enter a ? at the end of the reference when creating a power symbol. This is not the case. (There was recently a post over on reddit where a user was confused with this.)

[Seth_h]

@Rene_Poschl

The way you write it might be interpreted that one needs to enter a ? at the end of the reference when creating a power symbol.

Ah, fair. Edited. Holler if there’s anything else you catch.

[Rene_Poschl]

Linked your stackexchange answer in all respective FAQ articles that are related.