Electronics > KiCad

KiCad 8.0.4 didn't catch swapped power pins

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davep238:
In the schematic editor, I accidentally connected the VCC pin of a part to GND, and the GND pin to VCC. I ran ERC, and KiCad didn't flag that as an error. I even tried it with a KiCad library part (74x04), instead of my own. No error. I'm an idiot for not seeing my error, but I'm disappointed that ERC was OK with it.

Long ago, I used EAGLE, and I sort of recall that EAGLE asked if I wanted to connect a part's VCC pin to a 5 volt net. But, I'm guessing that KiCad is OK with connecting a part's power input pin to any power output pin.

Other than having other people look over my designs before I send them to a board house, is there anything that I can do to keep me from doing this again? I did find 2 other bugs that I made, plus changes I want to make, so I need to respin the board again, anyway.

Thanks
-Dave Pollum

ataradov:
There is no distinction between power types. This does not even make sense in all cases. Opamp power pins can have all sorts of voltage level combinations. And for negative logic, your "ground", may have higher potential than the  power.

And you can have arbitrary number of power rails in general. There  is no sane way to check for this.

djsb:
You should get a ERC error, "Error:Both GND and VCC are attached to the same items; GND will be used in the netlist". Maybe this should alert you to a possible problem, unless this is your intention?
I'm running 8.05, so maybe there was a bug in the earlier Kicad versions. Have you checked?

davep238:

--- Quote from: djsb on September 09, 2024, 06:04:55 am ---You should get a ERC error, "Error:Both GND and VCC are attached to the same items; GND will be used in the netlist". Maybe this should alert you to a possible problem, unless this is your intention?
I'm running 8.05, so maybe there was a bug in the earlier Kicad versions. Have you checked?

--- End quote ---
David,
It was a multi-gate part, so there was a separate power symbol, which I had upside down. I had the GND pin connected to VCC, and the VCC pin connected to GND, so they weren't connected to the same net.
Thanks.
-Dave Pollum

Doctorandus_P:
Such mistakes are easy to make, especially with all those different names for power pnis of symbols, Vee, Vdd, Vss, Vdd, etc. But I don't know how KiCad can prevent this. In one of my projects I used an LM7905 and an Atmega to build a light dimmer, because of the 3 quadrant thing of most triac's. There is not anything special about "GND". For ERC it is exactly the same as any other power net.

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