Hi, donated some money, downloaded and installed KiCad 8.
Added a voltage source of 10V DC and a resistor 100 ohm in the schematic diagram.
I run the simulation, and ground is not zero. It is -10V.
But ground has to be 0V.
What am I doing wrong?
Use the simulation 0 symbol as Mark says, or use the GND symbol. Ngspice treats those as interchangeable, but not earth.
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In addition. GND and Earth have different meanings in electrical installations (electronics).
“Ngspice treats those as interchangeable, but not earth.”
What on earth (pun intended) is the use of the earth symbol then? I thought KiCad used a different naming convention, that’s why i picked it. BTW, I am rather knowledgeable regarding electronics.
And more in general, “Earth” is not much used in electronics, but only in electrical installations. In electronics “GND” is often just some local reference which is used as a convenience, but nothing more.
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This is an ngspice thing, not a KiCad thing. See section 2.1.4.5 “Ground Node” in the ngspice manual.
I remember from 90s one TI telecomunniaction application book. In the RS485 chapter there were schematic where at each side RS485 transceivers were connected to their local PCB GNDs so allowing up to 7V difference between those GNDs. But each of these GNDs were connected to Earth through 100 ohm resistor. External disturbances generate the voltage difference between Earth connection points at both ends and such connection allowed for bigger than 7V difference between these both Earths. Transceivers having integrated ESD protection make most of disturbance pulse voltage be released at these resistors giving the whole solution better disturbance immunity.
In such cases use of earth symbol is perfectly logical for me.
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Because schematics != simulation.
The majority of people do not draw schematics to simulate. In schematic drawings, using different ground symbols is normal and part of documentation and even regulatory requirements in some cases. Earth is in particular one of those special notations for a ground and is usually associated with power systems.
In simulation land, things are different, you need to draw schematics specifically for simulation because simulators don’t understand everything. If you have “earth”, what does that mean? Should it be a real earth as-in a 60hz noisy building ground, the chassis of a box or some screw terminal that nobody uses?
Instead simulators like you to tell them this ground is 0V and that’s it. Base all your simulations going outwards from that 0V.
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In such cases use of earth symbol is perfectly logical for me.
To me too, having read your post, thank you!