Connection Error

I’m completely new to this, first of all, so can someone explain what is going on with these errors they won’t seem to go away no matter what.

Short: Add PWR_FLAGs to powered nets (both sides of the switch in this case)

Long: Electrical type of schematic symbol pins (KiCad 4 and KiCad 5)

I would argue for a better placement of the PWR_FLAG symbols, and he needs 3 of them, not two.

I put PWR_FLAG symbols at the source of power nets. Here are my 3(+1) suggested locations, and why.

  1. The source of the power to U1-7 is the “output” of the switch so put a PWR_FLAG on the wire by SW1-2.
  2. It looks like J1 is (or can be) the source of the +12V rail. If +12V isn’t generated elsewhere I would put a PWR_FLAG on the wire by J1-1.
  3. It also looks like J1 is (or can be) the source of ground. If GND isn’t “generated” (main source) elsewhere I would put a PWR_FLAG on the wire by J1-2.
  4. (Optional) U1 appears to be the source of a +5V supply. Since we are already using PWR_FLAG symbols to indicate the source of power rails, I would make sure the output pin of U1 isn’t a PowerOutput type (make it a PowerInput type) and put a PWR_FLAG on the wire by U1-8. This way the use of the PWR_FLAG symbol is consistent, but with the risk that now the ERC can’t warn you if you accidentally connect two power regulators directly to each other (which would push power into the one that outputs in the lower range of the tolerance).

The OP doesn’t have to follow my suggestions as the PWR_FLAG symbols will work anywhere on the affected nets. I just figure for my own schematics that if I’m going to have the visual “clutter” of the PWR_FLAG symbol to make the ERC happy then I may as well use the symbols to actually mean something. Then use them consistently throughout my designs.

Possibly better explanation ErrType(3): Pin connected to some others pins but no pin to drive it


Ah, yes, missed GND.
I didn’t mean to suggest the OP place the flags directly adjacent to the switch, BTW.

You lost me on 3 and 4.
3. by POWER_FLAG you mean the GND symbol right?
4. U1-8 is the output. I’m taking +12V in the converting it to +5V output

Read the linked FAQ article(s) :wink:

The power flag is a special symbol different from power symbols. See FAQ

@Rene_Poschl you have a link to the exact thread

See the FAQ that Rene linked to, above. Also, I specifically used “PWR_FLAG” instead of “POWER_FLAG” because the symbol in the power library is called “PWR_FLAG”. :wink:

The FAQ he is referring to is the one he already gave you here: Connection Error

but that’s not a link to the FAQ

It’s a link to a faq, look at the post tag

here for all you people that think that you’re God’s gift to creation, I still practically get the same error

You wouldn’t if you had listened to all those people.

Below the relevant section from the FAQ article already posted above: ErrType(3): Pin connected to some others pins but no pin to drive it

it wasn’t helpful the first 2 times I read it either.

How do I delete my account?

Ok lets put it differently:

KiCads ERC is kind of basic. It checks pins on any given net against each other. One of these checks is to see if everything is powered. That check works by testing if every net that has a power input on it also has a power output on it.

Normal power symbols (like GND) are power inputs. So are all power supply pins of ICs (if they follow the library convention). This means any net with something like this on it needs a power output.

For this reason there is a special symbol called the PWR_FLAG. This symbol is simply a symbol with a single power output pin. It has little in common with normal power symbols other than being in the same library and looking kind of similar (it does not create connections). To see how that symbol looks like check the screenshots in the FAQ article. For examples of how to use it again see the article.

Also remember ERC is just a tool that should point you to possible errors. It is totally ok for you to decide not to use it or to ignore certain error messages. (However, sadly there is no option to tell kicad not to show a certain error again, at least not in v5)

It is often unwise to be hasty about such decisions :wink:


Aside from the ERC, SW1 doesn’t make sense to me, it bridges +12V and +12V, unless it’s being used for just the LED.

1 Like

Your patience is amazing.

Now I remember why I used to avoid forums. Just puts me in a bad mood.

Maybe there is a lack of knowledge about power symbols in general.

@bckelley TlDr: power symbols are there to make connections without drawing a wire. I explain their use in this tutorial (second part of it) Tutorial: Introduction to PCB design with KiCad version 5.1 (Getting Started)