Confused About VCC

So i’m trying to design a simple pcb. This is my first attempt at using this program. The board only consists of 8 resistors and two Dual op-amps. Unfortunately, I’m at a complete loss as to how I can create separate positive and negative supplies for my op-amps. Maybe there’s a better op-amp I could use but, the one I picked includes two single op-amp symbols with pins 1, 2 and 3 on one of them and pins 5, 6 and 7 on the other. Along with this is a box that has the V+ (pin 8) and V- (pin 4) pins on it. After some research, it’s my understanding that there is only the one symbol (VCC) that I can use as a supply. I figured this wouldn’t be an issue since this is not a simulator so, I attached one VCC to pins 4 of both op-amps and one VCC to pins 8 of both op-amps. Unfortunately, I noticed that these pins are all interconnected in the board editor. That is, pin 4 (V-) of op-amp 1 is connected to pin 8 (V+) of op-amp 1, which is then connected to pin 4 (V-) of op-amp 2, which itself is then connected to pin 8 (V+) of op-amp 2. Of course, this observation is based on them thin yellow lines that interconnect everything in the board editor. What’s confusing me is the fact that everything else mirrors exactly what I have in the schematic so, I don’t understand why only these supply pins are interconnected the way they are. I don’t know what to make of this. Can I simply ignore them thin yellow lines? Being everything about these lines makes perfect sense, except for the op-amp supply lines, I’m assuming it represents the actual connections of my components so, this shouldn’t be what it seems to be. Do I just connect everything as intended with the wire tool, regardless of how these yellow lines seem to interconnect everything? I have more questions about this but, this is of paramount importance at the moment so, any help would be appreciated. Thanks.

VCC is just a predefined representation of a net. That is, everything connected to VCC will be one network and therefore interconnected on the pcb as you described.

The solution (at least one possibility) is simple. Just rename one or both VCC symbols so they become two nets. (Properties of the symbol - edit the “value”)

For example your „pin 8“ network could be „+15V“ or „VCC“ and the „Pin 4“ network will be „-15V“ or something like this.

Thank you. I figured it out soon after I posted this but, I then discover the headers and set it up the way I was gonna do it anyway. I have another question coming up but, for now, check out the pic below.

I have another question regarding 3 similar DRC error messages that don’t make any sense to me. In particular, there are some yellow objects that show up when i click on the error message but, I have no idea where they come from. Once I click ok, the images disappear. Check out the following pics.

For reference, below are two pics of the wire traces, top and bottom. Unless i’m missing something, I don’t see what can be causing them error messages. Notice also how there aren’t any weird yellow objects to be found. I don’t know. Am I missing something?

Hm. This is strange indeed.

The yellow objects mark the area of concern.
But i dont see any problems with N9. I would first run the DRC again to check if the message persists. If so delete the (red) trace on the top layer from U2 pin 2 to R1 and redraw it.

I think there is an error around R7 which could cause the 3rd DRC warning: R7 pin1 is Part of N4, but connected to N8 (Blue trace) and R7 pin 2 Part of N7 and connected to N5. Pls check this first and run DRC again.

I also can’t see the reason for the DRC warnings from the screenshots. Please check the things mentioned by @sasmus and if the problem still persists, you may send me your project file (as a *.lppz export) either by uploading the file here or by mail to the address listed at Contact | LibrePCB. I’ll then check whether the problem is in the project or if it’s a bug.

That was it. The two traces coming from R6 to U3 pin 6 and pin 7 (on the bottom trace) were overlapping with the traces on the top and bottom of R7. I redid the traces and ran DRC and ERC a few times, and so far, all is good. I also discovered how to snap to grid along the way as well so, I snapped everything into place and redid the traces…, again. Only thing that’s kinda annoying me now is the fact that my resistors are no longer lined up with my op-amp pins like they were before. I know. I can be a bit anal retentive with some things. Lol! I tried not snapping to grid but, they still ended up off a little as you can see from the pics. Not a big deal but, it’d be nice to put them closer to where i’d like them. Whatever. No big deal but…, if there is a way to de-activate snap to grid that i’m missing, please let me know. Thank you again and I look forward to more (mis)adventures with this community. :slight_smile:

Nice! Good to hear that you solved the problem.
Regarding Grid: The “snap to grid” pushes the center of the package (marked with a thin grey cross) to the grid. That leads to the pads to be off-grid with your DIL8 -OPs. (Edit: with standard 2,54mmm grid spacing)

Workaround if you want your Resistors in line with the OP-Amp pads: change the grid to 1,27mm.

Bildschirmfoto 2023-12-30 um 16.43.28
…or F4

and then
Bildschirmfoto 2023-12-30 um 16.43.18

Nice feature here: you can use up/down arrows to half/double the grid spacing.

Addition: Your are aware that you can push traces with the mouse (whole segments or just one end if you point the mouse over a joint)? … because you wrote that you did the traces again after the “snap to grid” command

That worked perfectly. Changing the grid spacing to 1.27 mm has completely changed everything. Snapping is now exactly what I want, and moving them traces around is a lot more precise. Thanks again. I’m sure I will run into more issues as I go on with this project but, at least I have a good footing now. Now for the rest of the circuit.:slight_smile:

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