Beginner - simple circuits


#1

Hello all,

I want to know if this is a good program to draw and simulate RLC and Transistor circuits, and then on to more complicated networks?

Does KiCad have a built in oscilloscope?

Thank-you.


#2

Run the simulation and then use the probe button to view a node.

Some links, a tutorial
http://ngspice.sourceforge.net/ngspice-eeschema.html

and the manual
http://docs.kicad-pcb.org/5.1.0/en/eeschema/eeschema.html#simulator


#3

Allright I will try to.

KiCad seems to have many subprograms.

How many programs are involved in simply turning “on” a circuit and watching a transient voltage?

I have not yet understood the process. Is it all in “eschema”?


#4

KiCAD is primarily intended to be a tool for laying out circuit boards. Its ability to run simulations is a “bonus” feature. To be strictly accurate, KiCAD doesn’t run simulations itself, but it processes a KiCAD schematic into a form (i.e., a SPICE netlist) that can be sent to the “ngspice” program - an independent, open-source project in its own right. From monitoring traffic on this Forum I get the impression that KiCAD’s ability to run simulations is still rather limited.

If your interest in circuit simulation is primarily focused on learning the basics of electronic circuit theory, then (in my opinion) there are several low-cost or no-charge simulation programs, with greater capability and friendlier user interfaces than the KiCAD simulation feature. If you are mainly interested in actually constructing circuits on PCB’s, then KiCAD’s simulation capabilities may provide a quick verification of the circuit’s basic operation.

Dale

P.S. - Circuit simulation programs are more likely to use the terms “waveform viewer” or “waveform plotter” rather than “oscilloscope”.


#5

At CeBit messe in previous century I got CD with PSpice. It is limited version, but I never needed to simulate big circuits so from time to time I use it mainly to simulate power supply filters (L,C with parasitic elements).
Few years ago I used LTSpice (free, not limited, supported by Linear), but only one, or two circuits simulated - no skilled in it. I think it is mainly destined to simulate Linear DCDC converters but can be used to simulate any circuit.
ngspice - I hear first time - as open-source can be worth to look at.


#6

5 posts were split to a new topic: Discussing the finer points of free software (libre vs. gratis/ free beer vs free speech)


#7

After a my first attempts in KiCad, I myself began to wonder if this is really dedicated to PCB’s.

I understand.

I am now simulating in LTspice.

Thank-you anyways.


#8

I suppose that if someone who reads this is interested in simple circuits in LTspice,

I hereby share this link I found:

http://denethor.wlu.ca/ltspice/#ground


#9

I’d say that’s a wise move. LTSpice won’t help you create a BOM. LTSpice won’t help you lay out a PCB. LTSpice won’t produce documentation that satisfies most commercial drawing standards.

But as a pure electronic circuit simulator, LTSpice beats the pants off high-priced commercial programs.

There is a LTSpice User’s Group, quite independent of the program’s publisher, at LTSpice User’s Group . It operates much like this Forum. You can find helpful people there, as well as SPICE models, example circuits, links to tutorials. etc.

Dale


#10

For me spice simultion and PCB design are completelly different tasks. I don’t see the need to have both these tasks in one programm as my schematics to simulate were always completelly different from schematics for PCB design.


#11

(Emphasis added.) Yes! I seldom simulate an entire PCB Assy - I look at subsections. E.g., the power supply, an amplifier, signal conditioning circuitry, timebase generator, etc. For each subsection I may use simulation to investigate things like high supply voltage, low supply voltage, high temp, low temp, tolerance stack skewed in one direction, tolerance stack skewed in the opposite direction, active components at the high end of their specification, active components at the low end of their specification, etc.

As you say, what you simulate is seldom the same circuit you lay out the PCB for. That’s why integrating NGSPICE with KiCAD has little attraction for me. It is a nice feature to catch people’s attention on a Datasheet or sales brochure, but for many of us working folks there is little benefit.

Dale


#12

I do not think the intention is for people to simulate the full board. The main benefit for this cooperation between kicad and ngspice is that ngspice now gets a nicer user interface for entering circuit information. And also a very large and helpful community.

On the other hand kicad users benefit as they now get a free circuit designer that uses an interface that they already know. (Yes they still need to learn a bit as there are now new features that they did not have in the past, but it is definitely less to learn then using ngspice directly from the command line.)


#13

That I see as the only important benefit for KiCad users.
I don’t know ngspice, I never tried to use simulation in KiCad.
I don’t simulate a lot. I really don’t remember how many years ago I used PSpice last time.
The first thing I would check if I will try to use KiCad to simulate circuits would be if I can assign a subcircuit to symbol. For me it is the key feature that I can put at schematic a capacitor and give to it the neme of certain part and behind that symbol there is the whole defined by me schematic with parasitic elements ot that part.
Do KiCad have it?


#14

Yes this is called a hierarchical sheet :wink: (Only thing that would be nice is having custom symbols for hierarchical sheets. Simulation would be the main place where i can see a benefit to such a feature.)


#15

Do that means that each capacitor and inductance in simulated power filter I have to replace with hierarchical sheet? Do that schematic will look still like a filter schematic? In PCB desing I don’t use hierarchical sheets so I don’t feel the consequences.


#16

You asked for subcircuits. I gave you the kicad way to make them. I am sure there is also a way to do this with spice commands.


#17

Is there a possibility for large-scale collaboration between the KiCAD and ngspice projects, to develop a common schematic-entry program, and a common file format for representing an electronic schematic, that simultaneously meets the needs of both tools?

  • A program that associates each symbol with not only its footprint, but also (optional) supplier information, as well as simulation model files.

  • A program that allows easy copy/paste operations between multiple documents - so I can grab a piece of my board schematic, then paste it into a separate document for simulation. After simulation - when topology adjustments are final and values optimized - I can copy a chunk of the simulation schematic, and paste it back into my board layout schematic.

Now, THAT would increase the efficiency of the design process!

Dale


#18

The current Eeschema - ngspice interface has been defined three years ago and has not seen any update since then.

In my view it is a good idea to start a new thread discussing user friendly improvements.

So once I (not being a PCB designer) had the view that one might add an additional layer in Eeschema that allows to encircle a portion of the complete schematic. And only this portion is to be simulated. The circle crossing any interconnect line would cut it. Then either an extra input to this line is to be set or the line allows a measurement, acting as output.

I guess many other, better ideas might surface up, perhaps not under the current header “Beginner - simple circuits”