Beginner trying too simulate an coil ignition circuit ( resonant circuit, tank circuit,)

[basilwatson]

Hi there
Nothing of importance , Im just finding my feet with Kicad, I use it often to draw schematics for wiring on vehicles, ( its great for that )
But I thought I would give the Simulation a try, So I drew a coil ignition circuit, 12v source, points ( switch) through a transformer ( step up), which, when the current collapses, produces a current in the secondary winding that go through a spark plug cap resistor and a spark plug air gap ( resistor ) to earth, basically the secondary winding is a tank circuit with a capacitor, However I got the sim to run but I really don’t know what values to plug in where, Especially with the transformer. atm I am just making up numbers
Im using Kcad 9 on a linux system
I can up load the file just not sure how ,
Hope someone can help
Kind regards
Stephen

[paulvdh]

For a car ignition coil (transformer / bobine).

Primary inductance has be low enough so the right amount of energy is stored in the magnetic field in the short time available. (A few ms maybe?)

When the switch opens, the same current wants to keep flowing, or a current though the secondary coil divided by the turns ratio. And to keep the current flowing, the voltage rises to whatever voltage is needed, until either the switch, or the spark plug sparks. The ratio of voltages between the primary and secondary coil will be (approximately) proportional to the turns ratio, but there is voltage drop due to the current.

There is also a capacitor over the primary coil. This reduces the speed at which the voltages rise, so the switch is open further before the voltage get really high. And probably, at the moment the spark plug sparks, it’s impedance is very low, and the capacitor also dumps most of it’s energy in the spark, so you get a stronger spark.

That’s the best I know about ignition coils and spark plugs.

Also, spark gaps are real electronic components used to limit damage due to over voltages. There are probably spice models for these things available.

For the rest: This forum tries to limit itself to help with how KiCad works, and not to projects or electronic theory. But we also want to be friendly towards users, so there is a compromise to be found here.

The easiest way to get started with simulations in KiCad is to search this forum. There are several threads which each post over 30+ simulations that work in KiCad. And probably some of them use transformers too.

[basilwatson]

Thanks Paul
for the eloquent reply, As usual, I know what I want to say but between the brain and the fingers ,
Yes Its “how” kicad works is what I was after , I drew the circuit but I have no Idea what values to plug in where

I have been watching every Tutorial I can find , and ive got the Kcad manual and so while I can give a resistor a value and the capacitor a value … I have no Idea if Im even doing things correctly such as with the coil or transformer and example of that would be the ground , and the source, found that out!

any help greatly appreciated
Stephen

Is there A; a place where I can upload a file for someone to check
or B, any suggestions for keywords when searching,

[DaveL]

https://www.edn.com/555-ignition-coil-driver/

Model a Spark Gap in LTSpice

[paulvdh]

@basilwatson

Is there A; a place where I can upload a file for someone to check

Yes, you can just drag and drop a file into your post and it will be uploaded here.

@basilwatson

or B, any suggestions for keywords when searching,

Keywords for searching for what?

Yesterday I made an overview for:

Simulation: Getting started with ngSpice and other resources

There are quite a lot sources and resources for getting started with ngSpice in KiCad, so I thought to make a list with links instead of repeating the information again and again and again and… Text Tutorials First, of course the ngSpice website itself. The link below is to how to use ngSpice with KiCad, but there is lots of other info over there, from the official ngSpice manual (ngSpice is a separate project then KiCad), to (links to) downloadable libraries with models. Video’s If you prefe…

If you’re having trouble with getting to grips with the basics, then I suggest you forget your ignition circuit for a while, and experiment a bit with a few of the working simulations first. It’s a bit finicky to get your first simulations going, because there are a bunch of not so obvious things that can go wrong:

• You need to have a GND symbol or a “zero” node in the simulation.
• The models have to work, and be compatible with ngSpice.
• The pin mapping has to correspond with the symbols (Spice pin mapping is often different from real IC’s).
• You can not have open nodes (unconnected resistors or capacitors).
• You have to add what type of simulation you want to run.

[basilwatson]

you are not going to believe this , Amazon arrived today with lots of electronic bis and bobs , some of those bits were 555 timers

However Im going to take Pauls advice, while the circuit I want to model is simple , I will focus on just one component at a time , get to know that get the model working then add a bit , Btw ,I got LT Spice working ,but I have to agree with someone on the internet ! its an awful GUI "! and I just couldnt get Qspice to work on linux so!
keep goin Kicad , we need ya!

Stephen