Hi All, I found a bunch of tutorials covering basic topics, looking for a tutorial that steps through to making a board layout. I have some steps wrong. Tried a first very simple schematic: it only has one trim pot, and one resistor (actually I need this utility board). I got the schematic ok, put foot prints on the resistor and trim pot. When I go to the PCB I can see the parts. So far so good. I wanted to put 3 solder pads on the board and connect the pads to one side of the resistor and 2 remaining trim pot pads. I first put the solder pads onto the PCB, but when I try to draw the traces from the solder pads to the resistor or trim pot, it looks like only one side is connected and the net is screwed up. The net seems to want me to connect the solder pads together, it won’t let me connect a solder pad to the parts. Im sure I have something backwards, or missed a step in the schematic software. I went back to the schematic, but I could not find solder pads there. its like the solder pad footprint is there, but not the schematic part. Thanks, MP
A screenshot of both the schematic and pcb would help us understand what you have created.
As a new user you are limited to one image per post so simply split them up in separate posts.
You can add pads/footprints directly to the PCB but I don’t know if you can assign a net if it isn’t in the schematic. I always find some symbol to use in the schematic so I can assign it a footprint and net. I even put the mounting holes down in the corner of the schematic. I am just a lowly home hobbyist hack so not sure if that is acceptable to you.
Thanks. I have been modifying the schematic to try to find a way to get pads on it. Haven’t found yet. Id like to put wire pads at the end of the 3 wires.
So I think I have the overall workflow down: create schematic, assign footprints to parts, generate net, load into PCB, connect traces. I think I don’t know how to get the right parts on the schematic.
Look in the connector_generic library. Just use conn_01x01. That’s one pad, one row. Then you can assign it a footprint.
Hi Hermit, yeah, I think that’s what I have wrong. I have the pads on the PCB but there’s no representation on the schematic.
Maybe a more general question: I looked around on the web and found “wire_pad”. Its not a schematic library, but a set of foot prints. I more or less understand how, say, resistor footprints get associated with the resistor schematic symbol, but I don’t understand at all how to make, or find the association between the wirepad foot print, going backwards to find what schematic part I need to put on the schematic. I can see the wire_pad foot prints in the pcb editor, but can’t find what schematic parts they are associated with. I have put the 1 x 1 connector, but when I go to “assign footprint” the list doesn’t have wire pads in it. Thanks.
The default workflow of KiCad is always from schematic to PCB. If you want to add something to the PCB you should add it to the schematic and then update to the PCB. What hermit was advising you to do is add three conn_01x01 symbols to the schematic, one at the end of each of the dangling wires you have. Reannotate the schematic to assign unique reference designators to the new parts. Assign the solder wire pad footprint you want to use to the new symbols Push the change to the pcb (you can use the “Update PCB to Schematic…” item in the tools menu of either eeschema or pcbnew).
Flow is always from schematic to pcb. I rarely use the Add Footprints tool in pcbnew, but when I do it is either to pull up the footprint browser to look at footprints, or to instert non circuit items that I don’t bother to put a schematic symbol for (like logos, fiducials, etc.). Note, the manually added footprints you add may be removed next time you push changes from the schematic to pcb.
First a bit of reading material for you:
- What is the difference between footprints and symbols?
- How does KiCad know which symbol pin represents which pad of the footprint?
From kicads point of view a symbol fits a footprint if both of them have the same “pins”. So in theory you could have a symbol with two pins and no other graphical element and connect that to any two pad footprint (so for example a resistor or capacitor or even a connector with two pins.)
Everything else apart from pins is there to communicate the design intent (the function of the part) Meaning it depends a bit on your preferences in some cases. (This includes the graphics, symbol name, additional fields for bill of materials creation, …)
The reason why @SembazuruCDE suggested the use of the generic connector symbol is because this is one option for a fitting symbol. (After all a wire pad is a place where you connect a wire to the pcb) If you would prefer a different symbol then you can do that.
It might be that you will not find the perfect symbol for everything. This means you will need to learn how to make your own symbols.
For this we also have a tutorial here: Tutorial: How to make a symbol (KiCad v5.1.x)
Thanks Sembazz. (Also, thanks to everyone for your patience with my very newbie questions). Major progress. I didn’t realize I had to load the wirepad footprint lib into the list where the schematic selects the footprints. Got that. And was able to get the wirepad (although the wrong ones) footprints wired into the schematic and now the PCB editor sees them. I removed the old traces, and its able to trace to the right places. Thanks!! Now all I have to do is find the right wirepad (single pad).
Thanks Rene!!! Reading …
I tend to add those at the end and I think you can lock them.
I recently found this website which has the whole process documented via simple example projects.
it also has a nice image about the KiCad workflow.
you can navigate each project via the table of content in the right
A little note to let you know there are commercial standards for class letters and doing reference designations. For class letters there is IEEE 315, Clause 22 (specifically Clause 22.4) and for assigning reference designations there is ANSI/ASME Y14.44. I don’t know why the developers (and users) aren’t aware of these?
Resistors use the class letter “R” and it doesn’t matter if the resistor is fixed value, variable/adjustable (as for a potentiometer or a rheostat), settable, or multi-element. The class letter(s) “RV” stand for a symmetrical varistor or voltage-sensitive resistor.
For an attachment point for a wire, whether a plated through hole or a surface mount technology (SMT) pad, I use the symbol for a “splice”, which is a connection dot. Reference designators are only used for individual items, not anything that is part of a PCB. However, for modern day schematic capture programs you have to handle them as if they were parts, but, of course, they would not appear on a parts list (PL). The class letter(s) I use for a plated through hole is “PTH” (for a non-plated through hole I would use “NPH”) and for an SMT pad I would use “PAD”. The land pattern/footprint assigned (in Cvpcb) for each reference designator is then whatever is appropriately needed.
For a short course on assigning reference designators see below:
Reference Designation of Electronic Parts
For the latest on reference designation of electronic parts see my blog posts at <www.txplore.com/blog>. Dr. Peter Dalmaris has kindly posted my seven articles on his Tech Explorations website out of Sydney, Australia. There is a main article and six appendices listed as follows:
(7) “Reference Designations For Electrical And Electronics Parts And Equipment”
18 September, 2018
(1) “Appendix A. List of Pertinent Applicable Standards”
20 September, 2018
(6) “Appendix B. Class Designation Letters”
20 September, 2018
(5) “Appendix C: List of Nonconforming Class Letters”
20 September, 2018
(4) “Appendix D. System Subdivision”
20 September, 2018
(3) “Appendix E: KiCad Anomalous Handling of Suffix Letters”
20 September, 2018
(2) “Appendix F: Scenario Questions and Answers”
20 September, 2018
You should look at the main article , Nr 7, first and then the appendices. The reason the numbering is out of sequence is because the newer dated material is first, followed by the older dated material, and in order of posting. As you go down through the blog postings you will run across Appendix A first followed by Appendices F, E, D, C, and B. The main article “Reference Designations…” is last.
On the symbol for a rotary control potentiometer you should mark which end is the clockwise (CW) end in accordance with what you are adjusting. That is for a volume control increasing resistance would increase the volume but if you were adjusting the base bias of a BJT in order to set the collector current, you would want to decrease the resistance to increase the base current and thus increase the collector current, thus preserving the clockwise<–>increase sense.
Or maybe most of the KiCad users just don’t care. I don’t.
We are aware of that and are working on better symbols. But we have not yet found the time to do it. (There is an issue somewhere on github about this.)
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