NE-2 I-V Curve ??

Of course tanh is single-valued, unlike the I-V of a NE2.

Cheers

Phil Hobbs

Unless you are clever, like me >:-}

Look back over my piece-wise-linear curve-fitting posts, using TANH, with all derivatives existing and finite.

In this particular case, as I envision it, there are not even any break-points involved.

What I seek right now is a reasonably accurate I-V curve. ...Jim Thompson

The typical curves we all know and despise assume just enough supply volt age to produce breakdown, enough current available from the supply to suppo rt sufficient conduction to produce visible light, and enough added series resistance to keep it out of the arc region (to prevent destruction from ov ercurrent).

Breakdown voltage depends on the gas mixture (usually a Penning mixture,

All of that also assumes you're feeding it fairly well regulated DC. Feed it AC or even RF and things change. Also the breakdown point is affected b y external illumination (granted you need bright, short wavelength light to see much change, but the effect is there).

If you get outside any of those parameters the curve can vary wildly from the "standard" or the bulb may not light at all or may not go out between cycles of AC or RF. What's your application? If it's nothing weird you can just go with the typical curve and over-spec the resistance a bit to keep f rom blowing up the bulb.

Mark L. Fergerson

There is a basic V-I (think curve tracer) curve. What you're referring to is what happens when you add other elements. ...Jim Thompson

Thanks, John, that looks like a good starting point. Thinking TANH

do is specify the peak and valley currents and voltages and one (or maybe 2) I,V points out on the "tail", though my gut feel is that the tail slope should intercept 0,0 until you start to smoke it. ...Jim Thompson

LT Spice already has neonbulb as a component.

(snip)

Well, those "other elements" really do matter in establishing the basic c urve for a given NE-2.

I'm getting old, I guess. I useta have a book from Glow-Lite (or somebody ) that started with the basics and went into variations, and that's where I remember the basic curve(s) from. I never thought I'd have to find a relia ble *modern* reference. Nowadays you can Google yourself silly and find not hing but unattributable made-up stuff.

Here's an old article that starts with the basics and goes into some deta il:

Caveat- it's written by Forrest Mims.

This guy actually does curve tracing with RF:

Bottom line, it's a plain vanilla "s" type negative resistance curve (bef ore the arc region) but the important points on the curve(s) vary from bulb to bulb.

Mark L. Fergerson

As do I, recently posted here. But I'm on a "crusade" to make Spice models that don't have convergence issues.

What are the topmost complaints we see here about Spice models?

(1) Doesn't match the behavior of the real part (2) Won't converge, or very slow simulating.

I aim to change that, and make some money from model-making, while I'm at it. ...Jim Thompson

Hey! Don't you know, his highness has proclaimed, "Math and simulation are both crutches"? ...Jim Thompson

Accurate I-V curve? There is no such thing, actually, except possibly under lab conditions. To design reliable circuits, you need a handful of parameters, and the curves are useful only for the general pattern of response. Gaseous conduction devices are not at all like semiconductors in the details, although thyratrons are similar to thyristors.

First is breakdown voltage. This is measured in the dark, but is lowered by UV (sunlight, fluorescent lamps, ...) If I recall, it's around 70 volts.

Before breakdown, impedance is essentially infinite. After breakdown, voltage drops to a fraction of the breakdown voltage. The higher the current the lower the voltage.

There is a current below which the glow will extinguish. One must remain below this current for a finite time, so all the ions have decayed or wandered away, before reapplying voltage.

There is a lot of information available:

..

The standard text on the physics was "Gaseous Conductors - Theory and engineering Applications", 1941, by James Dillon Cobine. This book was available from Dover for many years.

Cobine, James Dillon, Gaseous Conductors: Theory and Engineering Applications, Dover Publications, New York, 1958. paperback, xx+600 pp,

Joe Gwinn

That's what I need right now... get the core model right, then embellish with ambient light, etc.

(I'm very aware of ambient light issues... once turned off my monster tube amplifier while I went on vacation. It was located in a dark attic... and utilized OA2's for regulating various grid potentials. When I returned and powered it up... KABOOM... electrolytic gunk everywhere :-D

...Jim Thompson

So, who's going to pay you big bucks for a better model of an NE-2?

Neons are famously erratic. Local electric fields, ambient light, radiation will change the striking voltage. And they sputter away their own gas over time, eventually failing.

If you build an RC relaxation oscillator with two neons in parallel, small changes in the mentioned parameters will shift the discharge from one lamp to another.

LEDs are better behaved.

It's true. You get into all sorts of trouble simulating stuff that you don't understand. And I do mean *you*.