If there is a resistance there, then you should not use a piece of wire. You should represent the resistance with a resistor symbol, even if it’s not actually a physical component.
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So if I put a resistor symbol, Kicad will understand in the PCB and not seperate the two wires ?
No, you have to use something like a net tie as there will be two nets.
I have to say I don’t understand the design. Why is it important to measure Rpin?
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I think Jonathan nailed it quite some posts ago.
In this section of the schematic:
The +9V net is connected to the GND net. There is no spice like behavior, for KiCad those are just labels naming nets, and KiCad merges nets together when labels are connected with a wire.
I can easily reproduce this. When I add this to a schematic:
Then the whole “GND” net is merged with the “+9V” and the “+9V” name has precedence (KiCad uses alfabetical order (Is there a “+” in the alfabet?)).
Also, when you run Schematic Editor / Inspect / Electrical Rules Check, then KiCad shows a warning about this.
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This design isn’t to read data from the card but it is designed to test its integrity.
The thing is, this part of the schematic was something I added to try and solve the problem (something I saw on the internet a while ago, that was supposed to be the solution to my problem).
So the problem doesn’t come from here but indeed it “recreates the problem”… But thanks for pointing that out
An effective, but tedious way to localize your problem is to:
- Make a copy of your project.
- Delete a part of the project.
- Determine if the problem is gone.
- If the problem is still there, go back to step 2 and delete another part.
- If the problem disappeared. press [Ctrl + z] to undo the last delete, and then delete a smaller part
By iterating over the schematic in this way, you can get very close to the problem, and it does not take very much time.
Another option is to use the net highlighting function, and then closely examine all locations where the faulty net is present. Sometimes shorts between nets are hard to spot. For example a wire can be drawn across a schematic symbol which makes it hard to spot. If you see a junction dot at a location where pin of a schematic symbol should be connected to a single wire, then you have a very suspicious location.
Another tricks is to use m to move an schematic symbol and then check if the wiring that is left looks ok. (and then put it back of course).
And last, you can zip up the project and post it here, and it’s likely someone is kind enough to spend some time to look at it.
I don’t think all this is necessary, although it’s a great technique for any problem to locate the area causing the error.
Now that I used the net tie as you guys suggested, GND appears in the netlist.
I put the net tie right there before the GND to force KiCad to understand these are two different netlists :
As you can see, when I highlight the GND netlist I don’t have A10 highlighted now !
The net tie only “fools” the schematic editor into keeping the nets separate. However on the board, net A10 will be grounded because there will be a track to ground. I don’t understand how your circuit works, but I don’t see how it possibly could with that net grounded. Your Arduino’s A10 will either read GND potential, or output into a short to GND, depending on the direction of that pin.
The principle stays the same: When you connect different labels, KiCad just picks one of the net names for the whole net. I also do not know what that “Rpin” text is. Is that a local label? Another thing that looks suspicios is a No Connect Flag on a Vss pin.
The most logical and normal way would be to just not add any other labels to the GND net.
That’s interesting because the circuit works on my breadboard. I mean, A10 measures a voltage and from the voltage divider bridge I can calculate the resistance Rpin between two pins.
But I’m not even sure I need to put GND here so I’m gonna run some tests without, see if the circuit still works
Rpin is just a text for me to remember where the resistance between my two SD pins is.
Basically, the circuit here is quite easy. I’m trying to determine the resistance between two SD pins with a voltage divider bridge. The first pin is connected before “Rpin” and the second is connected after.
But is A10 shorted to ground on your breadboard? If not, then your schematic does not reflect the breadboard circuit.
A better workflow is to design the schematic first, debug it mentally, or with simulation, then replicate it physically on a breadboard for verification.
Perhaps your breadboard had a poor connection to ground . . .
The way I understand it, it is just a schematic drawn in a confusing way. “A10” is apparently not an adress line, but some high impedance input to some kind of measurement device. Also, other global labels with names such as 22 or 25 are unusual and they do not convey much meaning, but they are not an error on themself.
From an overall view it looks like a beginner in electronics, feeding small snippets of a project onto this forum and leaving us guessing.
So in reality, my scheme should be :
But the pin 2 short circuited to the ground bothers me. But it works on the breadboard so… I guess this is the right way to edit the scheme
sorry for the confusion I don’t know how I missed this error for so long it was right under my eyes
I had another question : anyone knows how I can make KiCad understand I want to power my op amps with +/-9V ?
For the moment all my op amps are just connected to the inverting input, non-inv input, and the output… just like this :
On the schematic, op amp 1 is connected to +/-9V as shown here :
I used the LM358 symbol that is natively in the kicad library and just renamed it to LM258 (which are the ones I use on my breadboard).
Duplicate the symbol and change the new unit to Unit C, that gives you the power connections to the device.
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Thank you for the explanation!
But I don’t quite understand because now it gives me a second footprint on the PCB editor, with only +9V and -9V connected