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Making neons conduct with 0 volts DC

PostPosted: Tue Dec 20, 2011 1:16 pm
by Doug Coulter
I can generally count on Joe Sousa to come up with things from left field, either things no one has ever thought of, of that have become arcane and obscure. He's busy, but he sent me some interesting email, reproduced here on some tests he's made recently on simple neon bulbs.

> On Mon, 2011-12-19 at 21:08 -0500, Joe Sousa wrote:
> > Doug, this may be of interest:
> > http://www.radiomuseum.org/forum/rf_tri ... _bulb.html
> > -Joe
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At 11:50 PM 12/19/2011, Doug Coulter wrote:
Yes, that's really interesting, also interesting because if I understand
> right, the R goes up with voltage...constant current, sort of?
>
> That might be true till the voltage got higher anyway, then you'd have
> the onset of regular discharge I'd guess.
>
> I would also guess that RF frequency had an effect. You might find that
> during parts of the cycle, the thing is turned on hard, but less so
> during zero crossings of the RF current. Duty cycle modulation...
>
> And DC across the bulb should phase shift the effective RF ionization.
>
> However, ion recombination times are on the slow side in a neon bulb, so
> I'd expect to see more effect lower than 1 mhz, from what I've seen in
> plasmas here. To get to the mhz region of interesting effects in plasma
> with a 3" spacing, I'm running 50kv. For neon tubes, the range of
> interest is 60 hz (really 120) gives them time to recombine, but 10's of
> khz not, as they found out with HF ballasts with not-50% duty giving ion
> migration issues.
>
> I'd guess you're coupling some RF into the neon terminals common mode,
> so some circuits would have issues with that.
>
>
> Can I link this on my boards for discussion?
>
> Doug
>
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Doug:
Sure, you can link the page for discussion, but I just asked one of the RadioMuseum admins to move the page under the newly created NE-2 tube page. Wait a day or too to see if it moves, or update your link if it dies.

You hit every concept on the head, including the gentle saturation effect where the resistance at 0V is about 2k, while it is about 20k at 30V. It appears that RF-excited neon gets depleted. This is the case with many three-legged amplifying devices.

I attached some measurements I did a few years ago on how long it takes for the trigger voltage to recover it's full value after current to the bulb is turned off. This a deionization profile of sorts. The attached plot suggests that oscillation above 4kHz would be a struggle as only 6V out of the 20V histerisis loop has recovered. The measurements show results for the NE-2 and for the Russian INS-1. On a related topic I attached results for burn-in of the INS-1 bulbs over a week at 1.5mA. This shows how poisoned cathodes can clean up.

Dan Sheingold pointed out the K3-J integrator as using the RF controlled NE-2, so I just took some photos of my unit and uploaded it. The original data-sheet for the K3-J came from scans of your Philbrick material. See http://www.philbrickarchive.org/k3-j_in ... ponent.pdf

-Joe

I'll try to keep up if the link moves. Here's the stuff he sent me directly:
INS-1_NE2_TriggerVoltage_recovery.gif

INS-1_Burnin_1week_at_1500uA.jpeg



I am now wondering what those conduction vs voltage curves over at radiomuseum are really trying to tell us. Space charge, ion collection at one terminal due to DC, what? And wondering how this information might apply to our fusor plasmas. His de-ionization profiles are useful, but we need to remember that they are also gas density and temperature dependent. Neons have a lot more gas in them than a fusor does...

Re: Making neons conduct with 0 volts DC

PostPosted: Wed Mar 26, 2014 9:22 am
by David McKee
This effect could be used to make a neat and simple little lightning detector...

Re: Making neons conduct with 0 volts DC

PostPosted: Thu Mar 27, 2014 9:47 am
by vmike
I experimented making lightening and radiation detectors with various neon bulbs several years ago. I biased the bulbs to just below the strike voltage, using them essentially as "miller effect" detectors. Worked.

mike

Re: Making neons conduct with 0 volts DC

PostPosted: Fri Mar 28, 2014 7:41 am
by David McKee
vmike, that sounds cool - if you got any pics or schematics I would like to seem them! I live in a pretty active lightning area and so this would be a neat little project. (because I don't have enough already! :lol: )