NE-2 I-V Curve ??

Or get 100 volts across it without splattering glass on the floor.

That's an NE-2T, the Thompson Bulb, filled with hot air instead of the usual neon mixture.

Definition of conductivity: the motion of charge per second divided by voltage 'gradient' across the terminals. Think in terms of conductivity coming into existance...seems easy enough to model, NOT! Wait! you can use your tanh functions, right?

"Massaging the math". Now that's funny.

It's a lot sharper in a gas.

Cheers

Phil Hobbs

It'll be interesting to see how small a leakage current is enough to help LTspice, anyway. Convergence problems _are_ a huge pain.

Cheers

Phil Hobbs

If you build the classic neon RC oscillator, it runs very slowly in LT Spice. If you keep hitting escape, it sort of nudges it along.

--sp

John Fields scribbled thus:

As Alan Sugar said many years ago "Stack them high & sell them cheap"...

I wonder why John Larkin thinks that. He's probably never had to do it.

Mathematicians say "?Give me four parameters, and I can fit an elephant. Give me five, and I can wiggle its trunk". I think the quote goes back to Cauchy, but I can't find a reference. The process of getting the parameters to give you the curve you want can be interesting. For my Ph.D. work I used a non-linear multi-parameter curve fitting program to do the last step of the job.

Do you want it to converge or do you want it to behave like an NE-2?

Both. If you will note in the above thread...

"The post was just my first pass to demonstrate a negative resistance region can be done in a way that doesn't choke any Spice with convergence issues."

Most Spices, LTspice included, throw up on the usual negative resistance modeling.

I think I solved the way to simply input VP, IP and VV, IV (peak and valley numbers) over lunch, on a napkin ;-)

But it'll be a few days before I can write it up into a subcircuit... design review time. ...Jim Thompson

Don't forget to simulate the noise.

Ralph, Every time I see a post by you, I think I should know you from somewhere. Were you ever at Motorola? ...Jim Thompson

--- Perhaps your 'classic' oscillator is different from mine, which seems to work just fine:

Version 4 SHEET 1 880 680 WIRE -272 208 -320 208 WIRE -160 208 -192 208 WIRE -48 208 -160 208 WIRE 48 208 -48 208 WIRE -48 224 -48 208 WIRE -320 240 -320 208 WIRE -160 240 -160 208 WIRE -320 336 -320 320 WIRE -160 336 -160 304 WIRE -160 336 -320 336 WIRE -48 336 -48 320 WIRE -48 336 -160 336 WIRE -320 384 -320 336 FLAG -320 384 0 FLAG 48 208 OUT SYMBOL Misc\\neonbulb -48 272 R0 WINDOW 0 40 1 Left 2 SYMATTR InstName NE1 SYMATTR Value2 Vstrike=80 Vhold=60 SYMBOL cap -176 240 R0 SYMATTR InstName C1

SYMBOL voltage -320 224 R0 WINDOW 123 0 0 Left 2 WINDOW 0 44 56 Left 2 WINDOW 3 31 87 Left 2 SYMATTR SpiceLine Rser=0 SYMATTR InstName V1 SYMATTR Value 150 SYMBOL res -176 192 R90 WINDOW 0 -33 58 VBottom 2 WINDOW 3 -32 58 VTop 2 SYMATTR InstName R1 SYMATTR Value 10meg TEXT -272 360 Left 2 !.tran 0 10s 0 0.01s uic TEXT -272 392 Left 2 ;NEON RELAXATION OSCILLATOR TEXT -272 424 Left 2 ;JOHN FIELDS, 19 MARCH 2014

John,

Opening the FULL schematic with LTspice, got an error message about not valid schematic, then LTspice would abort.

Little window, before closing: "Aborting ...unknown schematic syntax"

But, after removing the above section LTspice had no problem, expect had missing neon symbol, ...and characteristics. I then added from misc my own neonbulb and labeled per your description, [80V 60V] and found only these three lines describing the neonbulb, not four. Examining the list, they appeared identical, except:

SYMBOL Misc\\neonbulb -48 272 R0 SYMATTR InstName NE1 SYMATTR Value2 Vstrike=80 Vhold=60

Note: WINDOW line is missing, so I went back and removed that single line from your list, making it supposedly identical to mine, and STILL got the abort message ??!! Anybody else experience this?

YES, this thing is fast analysis.

This one worked:

Version 4 SHEET 1 880 680 WIRE -272 208 -320 208 WIRE -160 208 -192 208 WIRE -48 208 -160 208 WIRE 48 208 -48 208 WIRE -48 224 -48 208 WIRE -320 240 -320 208 WIRE -160 240 -160 208 WIRE -320 336 -320 320 WIRE -160 336 -160 304 WIRE -160 336 -320 336 WIRE -48 336 -48 320 WIRE -48 336 -160 336 WIRE -320 384 -320 336 FLAG -320 384 0 FLAG 48 208 OUT SYMBOL Misc\\neonbulb -48 272 R0 SYMATTR InstName NE1 SYMATTR Value2 Vstrike=80 Vhold=60 SYMBOL cap -176 240 R0 SYMATTR InstName C1

SYMBOL voltage -320 224 R0 WINDOW 123 0 0 Left 2 WINDOW 0 44 56 Left 2 WINDOW 3 31 87 Left 2 SYMATTR InstName V1 SYMATTR Value 150 SYMATTR SpiceLine Rser=0 SYMBOL res -176 192 R90 WINDOW 0 -33 58 VBottom 2 WINDOW 3 -32 58 VTop 2 SYMATTR InstName R1 SYMATTR Value 10meg TEXT -272 360 Left 2 !.tran 0 10s 0 0.01s uic TEXT -272 392 Left 2 ;NEON RELAXATION OSCILLATOR TEXT -272 424 Left 2 ;JOHN FIELDS, 19 MARCH 2014

No. The closest I came to that was when the local Motorola rep dropped by my university and handed out some bare 68000 dies to the EE students. I'm pretty sure I've never met anyone from this newsgroup in the flesh.

Mine's essentially the same except for parts values.

LT Spice can run fast or slow with tiny changes of values or parameters. I have one circuit that never converges if I do a 50 us transient analysis run, but runs instantly if I sim it for 51.

I really liked the old Dos simulator ECA. It was fast and always converged somehow. It would occasionally say "divide by zero" or something, but it kept going. Dumb rectangular integration or something.

Hey, plug in Jim's TANH version and see how well that oscillates.