Re: PULSE default rise and fall times (Trise=0 Tfall=0) (was: ISL70444SEH declaration issue?)
Andy, your model here does work all the way down to 1fs.
But:
- It’s much slower as-is, so
- I deleted the SIN source, V2/B
Now, it runs as fast as before, as far as I could sense (didn’t compare runtime in the logs), but no longer works below 10ps!
?
Dave
?
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From: [email protected] < [email protected]> On Behalf Of
Andy I
Sent: Sunday, July 16, 2023 12:58 PM
To: [email protected]
Subject: EXTERNAL: Re: : Re: [LTspice] PULSE default rise and fall times (Trise=0 Tfall=0) (was: ISL70444SEH declaration issue?)
?
For grins, here is another one to try.? It shows one way to control SPICE's internal timestep while not imposing a harshly small Maximum Timestep across the whole simulation (which would make it crawl):
V1 A 0 PULSE(0 1 4m {Trf} {Trf} 1m 2m)
V2 B 0 SIN (0 1 1000T 4m 0 0 1000)
.step param Trf list 1f 10f 11f 20f 50f 100f 1p
.meas T0 WHEN V(A)=0.01 rise=1
.meas T1 WHEN V(A)=0.99 rise=1
.options plotwinsize=0
? ? ?1 1.01915e-015? <-- 1.02 fs
? ? ?2 9.80032e-015? <-- 9.8 fs
? ? ?3 1.07796e-014? <-- 10.8 fs
? ? ?4 1.95998e-014? <-- 19.6 fs
? ? ?5 4.90007e-014? <-- 49.0 fs
? ? ?6 9.79997e-014? <-- 98.0 fs
? ? ?7 9.8e-013? <-- 0.98 ps
Andy
|
Or with a resistor, capacitor, and a 90V “B” battery, for a relaxation oscillator flasher!
?
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From: [email protected] < [email protected]> On Behalf Of
Jerry Lee Marcel
Sent: Sunday, July 16, 2023 2:08 PM
To: [email protected]
Subject: EXTERNAL: Re: [LTspice] Neon
?
Neon pilot lights were always used with a series resistor.
Le 16/07/2023 à 22:26, Andy I a écrit?:
John wrote, "...?because it would probably explode due to excessive current if it ever reached striking voltage."
Interesting point.
But I think it would depend on the impedance of the source of the overvoltage.? If it's a transient overvoltage, presumably the source of that transient does not have the same low impedance as the mains supply itself.? (Unless it was something like the HV wire
falling and shorting to the regular mains wire.)
I'm not trying to advocate putting a gas discharge tube directly across an AC mains line without a fuse or breaker.? I'm just playing the "what-if" and wanting to understand what goes on.
Andy
|
Neon pilot lights were always used with a series resistor.
Le 16/07/2023 à 22:26, Andy I a écrit?:
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John wrote, "...?because it
would probably explode due to excessive current if it ever
reached striking voltage."
Interesting point.
But I think it would depend on the impedance of the source of the
overvoltage.? If it's a transient overvoltage, presumably the
source of that transient does not have the same low impedance as
the mains supply itself.? (Unless it was something like the HV
wire falling and shorting to the regular mains wire.)
I'm not trying to advocate putting a gas discharge tube directly
across an AC mains line without a fuse or breaker.? I'm just
playing the "what-if" and wanting to understand what goes on.
Andy
|
In testing for immunity to
transients, the transients are really quite energetic, and are
supposed to be representative of transients that occur in real
life.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-07-16 21:26, Andy I wrote:
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John wrote, "...?because it
would probably explode due to excessive current if it ever
reached striking voltage."
Interesting point.
But I think it would depend on the impedance of the source of the
overvoltage.? If it's a transient overvoltage, presumably the
source of that transient does not have the same low impedance as
the mains supply itself.? (Unless it was something like the HV
wire falling and shorting to the regular mains wire.)
I'm not trying to advocate putting a gas discharge tube directly
across an AC mains line without a fuse or breaker.? I'm just
playing the "what-if" and wanting to understand what goes on.
Andy
|
John wrote, "...?because it would probably explode due to excessive current if it ever reached striking voltage."
Interesting point.
But I think it would depend on the impedance of the source of the overvoltage.? If it's a transient overvoltage, presumably the source of that transient does not have the same low impedance as the mains supply itself.? (Unless it was something like the HV wire falling and shorting to the regular mains wire.)
I'm not trying to advocate putting a gas discharge tube directly across an AC mains line without a fuse or breaker.? I'm just playing the "what-if" and wanting to understand what goes on.
Andy
|
Re: PULSE default rise and fall times (Trise=0 Tfall=0) (was: ISL70444SEH declaration issue?)
For grins, here is another one to try.? It shows one way to control SPICE's internal timestep while not imposing a harshly small Maximum Timestep across the whole simulation (which would make it crawl):
V1 A 0 PULSE(0 1 4m {Trf} {Trf} 1m 2m)
V2 B 0 SIN (0 1 1000T 4m 0 0 1000)
.step param Trf list 1f 10f 11f 20f 50f 100f 1p
.meas T0 WHEN V(A)=0.01 rise=1
.meas T1 WHEN V(A)=0.99 rise=1
.meas Td param T1-T0
.tran 0 10m
.options plotwinsize=0
Measurement: td
? step t1-t0
? ? ?1 1.01915e-015? <-- 1.02 fs
? ? ?2 9.80032e-015? <-- 9.8 fs
? ? ?3 1.07796e-014? <-- 10.8 fs
? ? ?4 1.95998e-014? <-- 19.6 fs
? ? ?5 4.90007e-014? <-- 49.0 fs
? ? ?6 9.79997e-014? <-- 98.0 fs
? ? ?7 9.8e-013? <-- 0.98 ps
Andy
|
It;s a matter of simple
observation that neon lamps flicker because they go dark at
low voltages. If you attach one to a 1 metre cable and swing
it in a vertical plane you can see the pattern of bright and
dark regions.
You wouldn't put a gas
discharge tube directly across an AC supply because it
would probably explode due to excessive current if it ever
reached striking voltage.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-07-16 19:41, Andy I wrote:
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Tom wrote, "The gas tubes respond in several microseconds."
That's nothing compared to 8.33 milliseconds, unless your
definition of "several" differs from mine.? Therefore the arc
should extinguish between one half-cycle and the next.? If the
next half-cycle also has a large over-voltage event, then of
course it would trigger again, and again ... as expected.
All the comments about limiting the current during an over-voltage
event are of course valid but that's true for any
device that limits an over-voltage condition, whether a gas
discharge tube or anything else.? Of course.? It's common sense,
but it's unrelated to it being a gas discharge tube.
I still do not see why one should "never use a gas discharge tube
across an AC ... line."? I do not believe that is a correct
argument.? Once they fire they will self-extinguish before the
next half-cycle begins.? Now if it was a DC line, that's another
thing.
Andy
|
Re: PULSE default rise and fall times (Trise=0 Tfall=0) (was: ISL70444SEH declaration issue?)
Dave wrote, "... I found an effective lowest limit in defining Tr and Tf, of >10ps." I think you meant 10fs. But try this:
V1 A 0 PULSE(0 1 1m {Trf} {Trf} 1m 2m)
.step param Trf list 1f 10f 11f 20f 50f 100f 1p
.meas T0 WHEN V(A)=0.01 rise=1
.meas T1 WHEN V(A)=0.99 rise=1
.meas Td param T1-T0
.tran 3m
.options plotwinsize=0
Measurement: td
? step t1-t0
? ? ?1 1.0388e-007
? ? ?2 9.8001e-015? <-- 9.8fs
? ? ?3 1.07802e-014? <-- 10.8fs
? ? ?4 1.96002e-014
? ? ?5 4.89999e-014
? ? ?6 9.8e-014
? ? ?7 9.8e-013 And then this:
V1 A 0 PULSE(0 1 1p {Trf} {Trf} 1p 2p)
.step param Trf list 0.000001f 0.001f 0.01f 0.1f 1f
.meas T0 WHEN V(A)=0.01 rise=1
.meas T1 WHEN V(A)=0.99 rise=1
.meas Td param T1-T0
.tran 0 3p
.options plotwinsize=0
Measurement: td
? step t1-t0
? ? ?1 9.8e-022? <-- 0.00000098fs
? ? ?2 9.8e-019? <-- 0.00098fs
? ? ?3 9.8e-018? <-- 0.0098fs
? ? ?4 9.8e-017? <-- 0.098fs
? ? ?5 9.8e-016? <-- 0.98fs
Your experiment differs (fails) because you didn't control LTspice's internal timestep.? What you measured in the fastest edges was LTspice's relaxed internal timestep, which plowed right past the requested 1fs and 10fs risetimes.? The pulse would have had the faster risetimes you requested, but the timestep was too large to reveal it.? Even my first case above misses the 1fs case because its internal timestep is too slow.
If you use Mark Data Points, you can see that your fastest edges produced no datapoints along the edges.? The other (slower) edges had multiple data points along each edge.
Man-handling SPICE/LTspice to control its internal timestep is a science all its own.? Sometimes it's simple; sometimes not.
For SPICE or LTspice to throttle its own internal timestep, it has to determine that a point it just simulated had failed because its error estimate was too great.? But if the point it simulated (after the rising edge) matches the requested waveform 100%, it has no reason to back up and try a smaller internal timestep.? Therein lies part of the problem.
Andy
|
Tom wrote, "The gas tubes respond in several microseconds."
That's nothing compared to 8.33 milliseconds, unless your definition of "several" differs from mine.? Therefore the arc should extinguish between one half-cycle and the next.? If the next half-cycle also has a large over-voltage event, then of course it would trigger again, and again ... as expected.
All the comments about limiting the current during an over-voltage event are of course valid but that's true for any device that limits an over-voltage condition, whether a gas discharge tube or anything else.? Of course.? It's common sense, but it's unrelated to it being a gas discharge tube.
I still do not see why one should "never use a gas discharge tube across an AC ... line."? I do not believe that is a correct argument.? Once they fire they will self-extinguish before the next half-cycle begins.? Now if it was a DC line, that's another thing.
Andy
|
Re: PULSE default rise and fall times (Trise=0 Tfall=0) (was: ISL70444SEH declaration issue?)
I think you might need to mind
your p's and f's.?
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-07-16 18:43, Bell, Dave wrote:
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Under lTspice 17.0.36, I found an
effective lowest limit in defining Tr and Tf, of >10ps.
?
Very simple model, only one V source:
?
;PULSE(0 1 4m {Trf} {Trf} 1m 2m)
.step param Trf list 1f 10f 11f 20f 50f
100f 1p
.meas T0 WHEN V(A)=0.01 rise=1
.meas T1 WHEN V(A)=0.99 rise=1
.meas Td param T1-T0
?
Log:
?
.step trf=1e-015
.step trf=1e-014
.step trf=1.1e-014
.step trf=2e-014
.step trf=5e-014
.step trf=1e-013
.step trf=1e-012
?
?
Measurement: t0
? step???????????? v(a)=0.01
???? 1???????????? 0.00400001
???? 2???????????? 0.00400001
???? 3???????????? 0.004
???? 4???????????? 0.004
???? 5???????????? 0.004
???? 6???????????? 0.004
???? 7???????????? 0.004
?
Measurement: t1
? step???????????? v(a)=0.99
???? 1???????????? 0.00400056
???? 2???????????? 0.00400056
???? 3???????????? 0.004
???? 4???????????? 0.004
???? 5???????????? 0.004
???? 6???????????? 0.004
???? 7???????????? 0.004
?
Measurement: td
? step???????????? t1-t0
???? 1???????????? 5.537e-007
???? 2???????????? 5.537e-007
???? 3???????????? 1.07796e-014
???? 4???????????? 1.95989e-014
???? 5???????????? 4.90007e-014
???? 6???????????? 9.79997e-014
???? 7???????????? 9.8e-013
?
Anything 10ps or shorter results in
554ns, but 11ps works within 3%
?
Dave
?
|
Re: PULSE default rise and fall times (Trise=0 Tfall=0) (was: ISL70444SEH declaration issue?)
Under lTspice 17.0.36, I found an effective lowest limit in defining Tr and Tf, of >10ps.
?
Very simple model, only one V source:
?
;PULSE(0 1 4m {Trf} {Trf} 1m 2m)
.step param Trf list 1f 10f 11f 20f 50f 100f 1p
.meas T0 WHEN V(A)=0.01 rise=1
.meas T1 WHEN V(A)=0.99 rise=1
.meas Td param T1-T0
?
Log:
?
.step trf=1e-015
.step trf=1e-014
.step trf=1.1e-014
.step trf=2e-014
.step trf=5e-014
.step trf=1e-013
.step trf=1e-012
?
?
Measurement: t0
? step???????????? v(a)=0.01
???? 1???????????? 0.00400001
???? 2???????????? 0.00400001
???? 3???????????? 0.004
???? 4???????????? 0.004
???? 5???????????? 0.004
???? 6???????????? 0.004
???? 7???????????? 0.004
?
Measurement: t1
? step???????????? v(a)=0.99
???? 1???????????? 0.00400056
???? 2???????????? 0.00400056
???? 3???????????? 0.004
???? 4???????????? 0.004
???? 5???????????? 0.004
???? 6???????????? 0.004
???? 7???????????? 0.004
?
Measurement: td
? step???????????? t1-t0
???? 1???????????? 5.537e-007
???? 2???????????? 5.537e-007
???? 3???????????? 1.07796e-014
???? 4???????????? 1.95989e-014
???? 5???????????? 4.90007e-014
???? 6???????????? 9.79997e-014
???? 7???????????? 9.8e-013
?
Anything 10ps or shorter results in 554ns, but 11ps works within 3%
?
Dave
?
|
In a simulation I have for a power oscillator, I use a green neon bulb as a bias adjustment indicator.
|
Many of the "Neon" bulbs you could buy in the old days aren't readily available anymore. You could buy blue, red, yellow, orange..etc. They are filled with different gas mixtures other than
Neon and some have a radioactive isotope added to lower the ionization voltage. One could buy bulbs screened for voltage/current ranges for use in protection and regulator circuits.
Neon bulbs are still used in AC power strips and as cheap surge protectors for signal and RF lines.?
|
The gas tubes respond in several microseconds. For AC line voltages, they will effectively be a short during each half cycle. If one doesn't have an inline fuse, both wiring and spark gap could suffer damage.
Varistors are the preferred device for use across AC lines but they have their own issues. If the surge event causes catastrophic failure of the varistor, it can catch fire and damage equipment. Varistors should have a thermal fuse in-line to avoid possible fire hazard. Three lead varistors have a built in thermal fuse.?
|
Re: .FERRET directive does not work.
I've never used ferret before, but I thought I'd try it.
My observation is the same as yours: it works in LTspiceIV and
LTspiceXVII 17.0.36, but not in 17.1.9.
This is new bug. It should be reported.
--
Regards,
Tony
On 16/07/2023 00:57, skyraider2 via
groups.io wrote:
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I have tried to
use the ".FERRET" directive in LTspice XVII version (X64): 17.1.9
and I get an error message saying trouble downloading file.
It works in LTspice IV.
Am I missing something or is this a bug?
* 02_sample-tran-ferret.asc
V1 Vout 0 1
.tran 10m
.ferret
.backanno
.end
For reference see
|
Re: .FERRET directive does not work.
Did you try to download more
than once? Any download may fail for no apparent reason. If
the problem persists, please report it to ADI at the email
address in the Help.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-07-15 23:57, skyraider2 via
groups.io wrote:
toggle quoted message
Show quoted text
I have tried to use the ".FERRET" directive in LTspice XVII
version (X64): 17.1.9 and I get an error message saying trouble
downloading file.
It works in LTspice IV.
Am I missing something or is this a bug?
* 02_sample-tran-ferret.asc
V1 Vout 0 1
.tran 10m
.ferret
.backanno
.end
For reference see
|
Re: Regarding basic simulation of ACST
jagdish, I narrowed it down to these two main problems, and a possible third one: (1)? The model file st_ACST.lib that you uploaded has a few internal models that are defined in the wrong place, outside of the subcircuit that they should have been part of.? As Tony found, they used parameters that were undefined outside of the subcircuit, and that caused errors. I moved the ".ENDS" line down several lines to include the model definitions, and that fixes that problem. (2)? You made a mistake when you auto-generated your symbol.? Don't use that symbol anymore.??The library file contains several subcircuits, and the one you should have used was this one: ? ? .subckt ACST310-8FP A K G
NOT this one, which you used:
? ??.SUBCKT ACST A G K PARAMS:
That one was for an internal subcircuit.? Consequently, your symbol had the pins in the wrong order (but more on that below), and it had the wrong name, and it had a whole string of parameter definitions which should not be there at all.
But you did not need to auto-generate your symbol.? LTspice has a normal TRIAC symbol already.
However, if you use LTspice's TRIAC symbol, there is one more problem.? The symbol expects the pins to be in this order: A-G-K.? But the model for your ACST310-8FP were in this order: A-K-G.? So I edited your .lib file to change that pin order.? (For some strange reason, half of the models in the file used the A-K-G order, and others used the A-G-K order.? I fixed them all.)
I uploaded my corrected version as ACST310-8FP_AI.zip.? Use the modified .lib file.
Andy
|
.FERRET directive does not work.
I have tried to use the ".FERRET" directive in LTspice XVII version (X64): 17.1.9 and I get an error message saying trouble downloading file. It works in LTspice IV. Am I missing something or is this a bug? * 02_sample-tran-ferret.asc
V1 Vout 0 1
.tran 10m
.ferret www.analog.com/media/jp/technical-documentation/data-sheets/j1028fc.pdf
.backanno
.end
For reference see
|
Don't have time for words, but all very good things to consider.?
|
The discharge concept becomes simpler if instead of thinking about the electric field between the electrodes which is the driver for the discharge process. Of course the shape and distance between electrodes determine the electric field, but the the electrons are only driven by the electric field. Putting in the geometry at this point only confuses the issues.
Consider this, a free electron will travel along the electric field from the negative electrode to the positive electrode and gather energy in the process.
If there is neutral gas along the path, the electron can bounce off of a gas molecule while transferring some of its energy to the molecule. If the electron has an energy less than the ionization energy of the gas molecule, that is all that happens (e + i --> e+ i). If the electron has more than the ionization energy of the gas molecule, then the electron will give up some of its energy to the molecule causing an electron from the molecule to be ejected. The result of this is? e + i --> 2e + i. We then have can have an avalanche process producing huge number of electrons which will result in a high current between the electrodes.
What determines the probability of an electron colliding with a neutral molecule and ionizing it?? 1) the electron has to have energy greater than the ionization potential of the particular type of gas molecule? 2) The probability of a electron-molecule collision. This probability is very roughly the area of the molecule (cross-section) and the number density of the molecule in the gas times the path length between the electrodes. Pc ~ A x Nd x L. More commonly this is expressed as a distance = mean free path (MFP) for the electron molecule problem.? If the MFP is shorter than the distance between electrode there should be a ionizing collision. If the MFP is much smaller than the inter-electrode spacing there will be many collisions.
Now, if the energy acquired while traveling one MFP is greater than the ionization potential of the gas, then the electrons ejected from the ionized gas can, themselves can gain enough energy to ionized even more gas molecules. Anotherwords, we have self-sustaining discharge highly dependent on the inter-electrode voltage, the gas pressure and the gas type.
How do we get the first electron that we need to trigger the discharge?? It can come from a cosmic ray, a radioactive element in the chamber, a UV light source. Also, a high enough voltage across the electrodes (producing a high electric field) can cause: 1) electrons to be torn directly from the molecules or electrons can be torn away from the metal electrodes (field emission).??
This is the qualitative basics. Real world is a bit more complicated, but these concepts might give you a qualitative understanding of the principles involved. Certainly, look at the Paschens Law information.
BTW? If an electrode has a sharp point, like a needle, that geometry results if a high electric field near the point. That's how field emission electron sources are made.? If you heat the electrode hot enough, the electrons in the metal can get hot enough to be ejected from the metal; i.e., thermionic electron sources.
--
jlballe
|
Bell, Dave
John Woodgate
Tony Casey