What am I doing wrong in Eeschema?


#1

Hi community!

I’m using KiCad 5 for the first time on Windows. I’ve used KiCad 4 in the past and am getting to know the new functions. Only two questions at this stage. What’s wrong with the attached? The standard schematic for the LM556 has been defined with Vcc as being Power Input and GND as Power Output. However as I’ve attached both Grounds to the same Network, there’s a clash. And changing the GND to a Power Input results in them not being “driven”. HELP!

Secondly, in Windows, normally when I click on the up and down arrows on the scroll bar, the window moves accordingly. But not in KiCad 5 PcbNew. As this is a standard Windows function, why does PcbNew prevent it from happening? Clicking on the scroll-bar, incidentally, works as it should. This is true for both vertical and horizontal scroll bars. Eeschema behaves as it should.

Thanks!

Goz


#2

I think you have a misunderstanding about pin types. Power output is to be used at the source of power. The supply pins of a normal IC are both to be set as power input (the ground and plus supply pins)

More info on electrical types: Electrical type of schematic symbol pins


#3

Hi Rene, that’s how it was set up in the data base. I had already corrected the GND PIN definition to Power Input (see original post) but then got the error, that the GND pin wasn’t being driven. How about that?

Cheers,

Goz


#4

#5

Hi Rene,

Thanks. But as you’ll see.from the schematic, the GND pin is attached to, well…ground. So I can’t add a power flag. What’s also strange ist that as the two modules of the 556 both have the Vcc and GND pins they have to be connected together as they are the same. But this is what Kicad is complaining about!?*

HELP

Thanks.

Martin

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#6

the power flag is different to the power symbols like ground. Read the FAQ post i linked above for more details but the short version is:

power symbols are global labels (hidden power input pins)
power flags are power output pins intended to mark the place where power comes from


#7

So here’s the resulting error when specifying the GND pin as Power Input:

Why is the first module’s GND pin driven yet the second isn’t? They’re a common pin between modules and both are connected to the GND net.

Martin


#8

U1 seems to be a multi part symbol. You have pins 7 and 14 on both units. Do not connect both of them!

I would suggest not to have the power pins on both units. Put them on a separate power only unit. More details on that see my tutorial for creating symbols: Tutorial: How to make a symbol (one of the tutorials shows how to make a proper multi unit symbol with power pins on a separate unit)


#9

This should probably be a bug report against the standard libraries if the repository hasn’t been fixed since the release of 5.0.2.

I just checked my 5.0.2 install (using the libraries that were in the installer package) and in the timer library is the LM556 (with several aliases) and it is comprised of only 2 units, both have both pins 7 and 14. Both pins are power inputs, so I don’t know how the OP got them as power outputs unless he made that change to try to fix the not driven error. (The OP did state in the original post that he was using the standard symbol libraries.)


#10

I hope this is not a golden rule. There are a benefits having power input pins on every units of a symbols.

  1. When changing part that having 2 units to part that have only 1 unit, or 3 units in one package, and symbol drawing are all identical.
  2. It ensure you got power. Reduce error of forgetting the power input unit.
  3. Make schematic can be review easier without question where is the power input.

I do connect all of them. It actually easily detected if 2 defined net short by this way in ERC too (if it implemented).


#11

Had you try add PWR_FLAG for the GND net? It may just because the ERC stop there since Pin 7 are actually the identical event it draw on two location.


#12

Hi!

As the OP I can confirm that I used the standard library. I can also confirm that in desperation, I tried the pin definitions in all flavours (power input and output) to try to find a solution (and in fact ended up defining the pins as “passive” to prevent the error - I know, not the intention, but it was a clunky solution to an annoying problem). I also changed the layout of the pins to be (for me) schematic friendly).

Goz


#13

Also, I never/rare use Power Output pin for symbol, event with regulator output IC. ERC will not understand the circuitry that well. So any 2 or more power output pins get on same net it will yell. Event the power symbol. This is why, it very hard to find the reason for using this Power Output type.


#14

I thought GND was a PWR_FLAG by definition? No?

Goz


#15

I don’t think so. No exception for any power symbol including GND. Sofware treat all the same kind of symbol.


#16

No it is different as explained above.


#17

I simply think the benefits of having power pins on a separate unit outweigh the downsides. If you design such a part properly then you can overlay the power pins with your normal unit and get the same result as if you have it on a single unit. But you gain the massive advantage of being able to have all of your power stuff consolidated in a particular place.

The main downside is that kicad does not check if you have all units of a multi unit symbol placed.

Hopefully the new file format will be more flexible in this regard.


#18

Oh dear, now I’m confused. From your “above” Rene, I’m assuming you mean the link you sent. Well there it states the following:

image

So the GND flag is actually a “power input” meaning it could be able to be connected to a “power output” OR a “power input”, which makes sense. As such, I think my problem lies with the fact that EEschema can’t deal with two modules having the same power input and ground pins for both modules, as both you and SembazuruCDE have both commented.

However not connecting the power and ground of one module, brings yet more problems:

Goz


#19

Got it. Thanks. I’m using a duff schematic from the standard library :frowning:

Kann mal passieren.

Thanks again.

Goz


#20

I would say depend. I had try both styles, I end up that conclusion. It help my coworker review schematic much easier. When I have about 10+ such part on the schematic, I very hard to not make a dump mistake (not connect power to the part). So I like to have power pins on every units (there are always exception to this).