This is a neophyte question. I apologize if this is obvious.
I have some panel mount components that I’m planning on just soldering wires from to TTH pads. I’m using a pretty simple guitar pedal as an exercise to learn analog circuits and the design process. I’m trying to do the “correct” thing, so this isn’t an ask for some hack. I don’t care about them showing up in my BOM, etc.
Originally I was including them in the schematic, but quickly realized that was a bad idea. Googling a bit and reading stuff here, showed me just to place mounting holes, and then I set values for them indicating their purpose in life.
My power source seems fine, since I have already have “power” symbols hanging out on that part of the circuit.
And my phono input has one mounting hole going to ground. But do I need to add a V (sub something) symbol or something to the wire coming off the signal side?
Also, how should I deal with the leads coming off a potentiometer?
Are you working off of a know design that you can share a link too? The software is mainly for designing boards so it does come down to what you want the board to look like and do.
A couple of hints: You can assign a different footprint than what the component would expect, e.g. you can give a potentiometer a footprint of a 3 pad connector; and you can hide components from the BOM. These will give you some flexibility.
Hermit:
The design is based around the old Tube Screamer overdrive circuit, closest to the one here under section 1.1.3. I’m still playing on a breadboard to finalize what specifically I want, playing with different tone control, filter, and clipping setups until it sounds “cool” to me.
And, I’m sorry Rene that I totally missed that page and feel a little foolish now. The document linked from there on how to connect a wire, with the extra NPTH holes for strain relief was what I had envisioned.
All of these sound like excellent ideas to end up with the PCB I want. I guess I was most going for a “proper” schematic or “best-practices” or something like that, but it sounds like I may have just been overly concerned. I’m walking through this one step at a time, and am trying to get the process for each right. I know my PCB will likely cause me to revisit the schematic, but I’m wanting the structure to be sound.
I should also note that my experience with KiCad has just been amazing. It’s been actually fun to use, once I got a hang of the keyboard commands (and being a vi user, that wasn’t too bad).
Errors are cumulative at best but usually exponential. @Rene_Poschl has done a lot of good work on the FAQ. It’s complex software so there is lots of FAQ material.
If you use board mounted pots, you won’t have to worry about leads & the PCB will be securely fixed as a bonus. See below for an example that is very similar to how the pots on a Tube Screamer are usually laid out. Also, there’s no law saying you can’t use that footprint for wiring a solder lug pot instead.
Here I’ve chosen a footprint with just one pad for Volume; leg 1 connects to that pad, leg 2 connects to ground (wire to power connector ground lug, for instance), and leg 3 is left unconnected.
That is awesome. Thanks for the amazingly relevant example. Board-mounting the pots will probably also help me save space in the enclosure and make the board more secure.
The “correct” way to ref des components on a (main) PCB and a panel, on one (system level) schematic is to use the Unit Numbering Method of ANSI/ASME Y14.44 that uses reference designation prefixes. For instance the main PCB might use A1 ref des prefix and the panel would use A2 ref des prefix.
For a potentiometer mounted to the panel with wires attached you would ref des as follows:
A2R1 The pot.
A2R1W1, A2R1W2, and A2R1W3 shown connected to the three lugs.
On the A1 PCBA you have some options as to ref des the plated through holes for attachment of the wires. Or use shouldered solder pins that would use class letter E.
For the PCB copy the system schematic diagram and then delete all the parts with the A2 prefix; and then delete the A1 prefix from all the A1 prefixed parts. You now have basic reference designations for all the PCBA parts.
–Larry
