Hi I’m new to pcb design and have a few questions please… I’m designing a pcb for my hobby and wonder do I first HAVE to create a schematic or can I just wing it and free hand design the pcb?
Also if so how to I make a pad connect to GND on the ground plane?
Thank you and sorry If I’ve used the wrong terms I’m learning.
It is “possible” to create a PCB in KiCad without a schematic, but it is a really big nuisance to attempt to do so. Without a schematic and therefore also without a netlist, KiCad does not know which pads and tracks should be connected to each other, and which parts belong to different nets, and thus should be kept at minimum defined distances from each other.
The usual answer to the objection: “… but I only want very simple PCB’s” is: If your PCB is so simple, then drawing a schematic is also trivially simple. There is a Plugin called “Wire It” in KiCad that can help (a bit) with creating a PCB without a schematic, but it is still more difficult then just drawing the schematic first. Without a schematic you also can not use DRC (and ERC of course) and those are both great tools to help you detect wiring mistakes.
This is an excellent example of what a schematic and netlist can do for you:
If you have a schematic, then KiCad knows which pins are part of the GND net. So you just draw a zone (I usually draw it outside of the PCB outline), and tell KiCad that zone is part of the GND net. Then when you press the b Key, KiCad calculates all the zone boundaries, connects to the GND pads (and creates thermal spokes if you want) while also keeping a defined distance form all items (tracks, other zones, pads and even the PCB outline) that are not part of the GND net.
Note: Zone boundaries can also be regenerated automatically, but this takes too much time to do this for a big PCB)
You don’t, but then you use KiCad PCB as a simple graphic program loosing in my opinion more than 95% of help you can get from it.
In 70s I was designing my PCBs using squared paper and pencil (with no automatic netlist control of course) but since I had a chance to first time using PCB design program (about 86) I have never designed any PCB without drawing a schematic first. Even if pcb has two pads and a track between them (antenna) I have schematic with these two pads and one wire connecting them
I can also turn the question around. Why would you want to design a PCB without a schematic? Even if the schematic was just a visual reference, it’s always nice to have some documentation in your project.
I draw a schematic first, even if I’m just breadboarding. If you don’t have a schematic, even a handrawn one, how can you be sure the connections match the design? It’s too much to ask of your brain to keep dragging up details; that’s why clay tablets and paper were invented. Plus you can actually do some reasoning and calculations on the circuit with a schematic in front of you.
@Paul1966,
If you decide to try creating a schematic, you will find many of the commonly used symbols in the Kicad library named “Device”.
I did a board from a breadboard and it was a nightmare. First I tried to work from a picture he sent. He had small jumpers ‘neatly hidden’ beneath longer traces. He said next time he’d make notes. I said, “The schematic is your notes”.
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