This is a “I don’t know what I don’t know” question.
I’m recreating a PCB that sits inside a lever switch. The switch has 6 contacts that slide across the surface of the PCB in 3 regions. The switching logic / truth tables are adjusted by changing the regions of copper on the PCB.
I plan to trace the existing design to get the geometry, then modify to the logic I require.
How should I represent these copper areas in the schematic so that I can have multiple ‘areas’ on the PCB layout? I guess ERC won’t work as the contacts themselves won’t be on the schematic, so I’ll have to eyeball for correctness.
Simple schematic with two SMT resistors, and on the PCB I drew a rectangle over one of the pads, and this is all accepted by DRC. In the properties of the rectangle you can see that it has become a part of Net-(R1-Pad2), and that is also good. I also set it’s properties to Filled Shape and a line width of 0 (Which makes the corners sharp).
KiCad really does not like working without a schematic (And the netlist it creates). So I would create a schematic. Each net then just becomes two test points connected to each other.
After a bit more testing…
I drew a schematic in which the “extra pads” are also included:
For the “contact area’s” I used rectangles and polygons on the F.CU layer, and I added SMT pads to have placeholders t route the tracks to. Apparently that was not strictly needed, as the center of a filled polygon (on a copper layer) is apparently also an attachment point for tracks. But in that case you do have to set the net name manually.
I zipped up the partial project. I did it in KiCad V8.0.9. Opening this in KiCad V9 should not be a problem.
@paulvdh Brilliant - many thanks for taking the time to explain. I see there are multiple ways to achieve the same thing, but some ‘better’ than others. By labelling each copper region I can correlate the schematic to my truth table - which is a bit de-coupled from the geometric reality (eg, there are islands of copper that aren’t connected to anything, deliberately).
I’ll lay out my updated design and report back.
Other potential issues include getting the make before break behaviour done in the same way as the existing artwork (if there is any secret magic going on… e.g. the slanted regions and slightly differing horizonal / vertical sizes of region. I can only think that’s done on purpose.), and finding a cost-effective fabricator for hard gold finish.
