ID:	4216
From:	Evan Foss <ev...@gmail.com>
Date:	Wed, 24 Jun 2020 15:14:13 -0400
Subject:	Re: [pcb-rnd] Off topic (maybe) - Spice simulator
in-reply-to:	4214 from gene glick <ge...@optonline.net>
replies:	4217 from gene glick <ge...@optonline.net>
Gene,
 
After you hit the V breakdown the plasma state of the gas becomes more
conductive. This is part of the trick to fluorescent light ballasts.
If it's an air gap, humidity changes all of this.
 
Evan
 
On Wed, Jun 24, 2020 at 1:06 PM gene glick <geneglick@optonline.net> wrote:
>
> Can't you take a zener diode model and crank up the breakdown voltage? Alternatively, make a voltage controlled switch that turns on at the needed voltage. I think a voltage dependent current source might also do the job.
>
> I'll bet there are many other ways to do this as well.
>
> On Wed, Jun 24, 2020, 12:22 PM Robin Laing <MeSat@telusplanet.net> wrote:
>>
>> On 23/06/2020 08:20, Anthony Tuttle wrote:
>> > LTspice has a neon lamp model that can work without being too prone to
>> > convergence issues. I have also used R={expression} as the resistance
>> > value in resistors to simulate switches and this may be workable for an
>> > improvised discharge model.
>> >
>> > There are spice models for GDTs, you may have to contact the
>> > manufacturer directly to gain access. They are never perfect but there
>> > has been some work on advanced GDT models.
>> >
>> > On Tue, Jun 23, 2020 at 1:41 AM stefan <stefan.schippers@gmail.com
>> > <mailto:stefan.schippers@gmail.com>> wrote:
>> >
>> >
>> >>     Hello,
>> >>
>> >>     I am involved with a project that will involve high voltage pulse
>> >>     circuit design and I am looking for a circuit simulator that will
>> >>     give
>> >>     us an accurate representation of a circuit.
>> >>
>> >>     Needs to work with spark gap technology as that is the present
>> >>     design.
>> >>     Maybe gas discharge tube as well.
>> >>
>> >>     Presently one member of the team is trying to use Multisim from NI
>> >>     but I
>> >>     am wondering if there may be a better package.
>> >>
>> >     NGSPICE developers are doing a good job,
>> >     ngspice netlists may contain capacitors, resistors, inductors with
>> >     arbitrary expressions about their value.
>> >     Moreover the 'B source' allows any type of voltage/current source
>> >     with arbitrary expressions.
>> >
>> >     Combining these elements a model for a gas discharge/breakdown can
>> >     be created.
>> >     The big issue is not the simulator itself, but the quality of the model:
>> >
>> >     1) ability to accurately describe the device.
>> >     2) simulator must converge to a solution.
>> >
>> >     Breakdown devices (devices with infinite resistance that start
>> >     conducting with very low resistance when a voltage threshold is
>> >     reached) are famous for giving convergence issues. This usually
>> >     happen due to poor model description. A current limit must be
>> >     included in the equations (no physical device can sustain 1e15 Amp
>> >     of current :-) ).
>> >
>> >     Stefan
>> >
>>
>> Thank you to all.
>>
>> The breakdown is where I ran into problems with a model years ago.  It
>> was quicker to just setup an test bed and try it.  Don't do enough
>> design work to take the time to learn the simulator.  Same reason that
>> Multisim is being used.
>>
>> Robin
>>
>>
>>
 
 
-- 
https://github.com/evanfoss
 
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