Newbie Question! about common ground?

Hi, I am new to KICAD. Actually, I am working on a project where I need to measure the charging current as described on the circuit below. The idea is how can I make a common ground especially between the transistor, the fuel gauge BQ35100 and the microcontroller?

Another question is about the schematic itself, is it okey? or do I have to improve it a little bit more before I go to the routing part?

1 Like

Here is the circuit:

1 Like

Hi, I’m not sure I understand what your KiCad specific question is ?

This circuit uses differential-input for current sensing resistor. You should be able to connect all ground together without worrying about voltage drops on traces messing up the current measurement.
Then regarding the rest of the circuit:
Is Q1 supposed to be shorting the SP_PWR to ground? It also has no base resistor, so it will pull high current from the MCU output possibly damaging itself and the MCU.
You also have multiple labels tied to the same net, example: GE and GE_uc, there is no need to use different names for these, since the signal doesn’t pass through any components on the way to the MCU.
Jack J2 also seems to have the text labels swapped.
Overall a good-looking and tidy schematic, good job.

Thanks for your precious advises, much appreciated. Here’s the final version of my KICAD file in that case:

But the thing is that I am wondering how can I connect all the GND’s to each other, is there anyway to do that without connecting them one by one ? The schematic would be very cluttered.

Don’t you think that I should add a transistor between the emitter and the ground of the transistor to not shortcut the solar panel ?

The GND symbol acts as a global label, so it already connects everything together

I think it’s obvious that I am currently searching for a way (or option) provided by KICAD to connect all my grounds together!

Ah okey, thanks. How about the transistor and the resistance that should be added, do I really need to add that ?

Yes, unless there is an on-board resistor on the Rapsberry PI. I’m not familiar with it so you’re probably more knowledgeable about it.

It would be nice to see all the Refs. and Values with the same orientation.

There are a lot of unconnected wires (see small green boxes).

Placing everything in little boxes makes trying to read and understand the schematic an excessively time consuming chore. The purpose of wires is to connect symbols so the flow of the circuit can be understood easily.
I liken this style of Schematic as a page of writing where each sentence is in its own little box and those boxes are numbered, but scattered randomly on the page.

There are not many symbols, so why not join them together and create one big box?

1 Like

I mean that should be placed between the emitter and the ground, not the one that should be connected to the base of the transistor!

I don’t think you ever mentioned anything about an emitter resistor? If it’s a switching circuit, you should jus connect emitter to ground.

Is there anyway to add the make all the reference with the same orientation without doing that manually?
I can’t see any of the small green boxes… as you can see on the ERC, there’s no error!!

How would be joining them together in one box ? what should I join? all the green boxes under another bigger one ?

Select all symbols (ctrl+click) that you want to fix, and then right-click → autoplace fields. For me the keyboard shortcut for that is ‘O’ but I have a custom hotkey setup and might have changed it from the default.

@Dawid_Cislo “O” is default.

Some examples:

These don’t cause ERC errors

1 Like

It is why I didn’t tried to understand this schematic at all. I see nothing from it.
For me schematic is a language electronics speak with each other. But when in sentence you use right words but in random order it is no longer understandable.
I wonder why the elements in the sheet center are not also distributed one by one in separate blocks :slight_smile:

Yes, he did (post 6):

It is a designer decision depending on the transistor intended function. May be as a last over-voltage protection its task is to short something to ground to blow the fuse somewhere.
And this is certainly not KiCad function.


I Think since I’ve no error on the ERC, These are already connected using local labels… am I wrong ?

All the symbols.

On the schematic page: that is one big box.

ah do you mean that I need to join all the meaning of the symbols on the big box ?