On 03/17/2014 01:27 PM, Tim Wescott wrote:
On Sun, 16 Mar 2014 11:20:38 -0700, Jim Thompson wrote:

On Sun, 16 Mar 2014 13:59:29 -0400, Phil Hobbs
wrote:

On 3/16/2014 1:39 PM, Jim Thompson wrote:
Anyone have an accurate I-V curve for an NE-2 neon indicator lamp?

(I think it's time I applied TANH to it ;-)

...Jim Thompson


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.

I can't tell if you're being purposely coy, or if you've missed Phil's
point.

Gas discharge devices like neon lamps have hysteresis: when they're on,
they'll conduct at a lower voltage than their turn-on voltage.

So a simple I-V curve doesn't cut it, unless you're only trying to
simulate the device in the on state, and leaving the user out to dry for
figuring out turn-on and turn-off behavior.


If you can model the off-state and on-state behaviour, then at speeds
slow compared with the recombination time, you can get by with a 1-bit
memory telling you which model to use. It's easy to patch that up with
a tanh or the equivalent to make the switch soft.

LTspice does that for you if you specify a negative hysteresis voltage.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net