What does these errors mean and how to get rid of them?
You are running into a safety feature of Kicad. Some pins of packages such as the GND and V+ pin are so called input power pins. They need power in order to function.
There are also symbols like a 9V battery or a barrel jack or an LDO which supply power. Those things have power output pins.
Every power net needs one power output pin attached. Than Kicad knows that you have your power supply and that every chip with power input pins will be fine.
However. If your power supply comes from a screw terminal than Kicad cannot possibly know that power comes in on that screw terminal. For all Kicad knows you want to use that screw terminal to supply power to something else instead.
In order to keep the DRC happy. You can attach a PWR_FLAG to your power net. With this you tell Kicad that your net will be supplied with power. You can find this symbol among the power symbols. In your case your GND and V+ net each need a PWR_FLAG attached.
There is also a separate error for when you attach 2 power output pins to the same net. Parallel power supplies aren’t safe most of the time so Kicad will warn you about that as well.
Regards,
Bas
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Thanks, It’s not easy to understand this, but somehow I now managed to fix all them power errors thanks to you suggestions though I don’t get what the “PWR_FLAG” really means, even if I added it on a few places.
It means “there is a power source in this net”. One - and only one - of the pins in the net can be defined as “power output”. If there is no power output in some component symbol, the power flag can be used to indicate that some unidentified pin works as the power source. Again, there can be only one power source in one net, and it is either a component pin or a power flag.
In reality even the power flag is just a symbol whose pin is “power output”, so this can be generalized: only one pin in each net can be defined as power output.
The only reason why this is needed is to keep the ERC check happy. If there are one or more power consumers, i.e. “power input” pins in the net, it needs exactly one “power output”. Otherwise the ERC complains.
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PWR_FLAG tells ERC: “There is a power source at this net even you (KiCad) don’t see it”.
ERC is not intelligent tool. It only checks if no power output pin is connected to the net to which power input pin is connected than it is Error.
If between power output pin and power input pin you will have filter with L then ERC will not get that power is going through L. On both L sides there are other nets and each net is analysed separately.
Edit:
After sending my post I noticed that this question was just answered.
Thanks, very kind and well explained!
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