Author Topic: Neon Glow Lamps and Indicators - Short Life  (Read 531 times)
merc
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Neon Glow Lamps and Indicators - Short Life « on: October 26, 2016, 02:58:02 PM » Author: merc
It seems that neon lamps (at least modern ones) don't last too much. It also applies to indicators, that should be long life.
"Flicker flame" lamps are rated to 1,000 hours only.
I've got an E14 lamp that got visibly blackened after some hours of use (not sure how many - probably less than 100).

Most neon glow indicators start to flicker after some time of use. Also the one in our bathroom fan does so and the total hours of use could be a few hundreds at maximum.
With neon glow indicators in light switches is the random flickering more than obvious.

Why there's such a short life in case of the lamp that doesn't heat up much, it is small and low-pressure, hence leaks shouldn't be a problem?
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #1 on: October 26, 2016, 06:13:32 PM » Author: Solanaceae
I think that the thing is the lamps made today may have smaller resistor values than those of ye olde times. Also fill mixture, electrode material, and gas pressure could be factors.
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #2 on: October 26, 2016, 11:07:05 PM » Author: dor123
The neon indicator lamp that was at the illuminated switch of the boiler at my mother home, before she replaced it with a timer switch (This was long time ago), survived as long as LED indicators. This is all about quality.
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #3 on: October 28, 2016, 03:35:06 AM » Author: Medved
As far as I remember, the Neons had flickered and were blackening out all the time, it was just considered normal.
By the way it was the reason, why a lot of equipment had used just an underdriven incandescent as an indicator (mainly the heater based ones like water heaters, stoves, cloth irons,... - a low voltage incandescent was connected parallel to a short section of the heater; usually a 3.5V bulb was powered by about 2V or so, so its life became in high 10k's of hours).
All the Neons taken from any older equipment which was really in use were all the time pitch black.
So I don't think it is worse than it was, just we are more demanding even for these details now...
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #4 on: October 28, 2016, 02:02:43 PM » Author: hannahs lights
I have several of those 4 way extension leads with neon Indicators and the neons had very short lives even with relatively expensive sockets the neon in my ancient 4 way lead is still going strong
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #5 on: October 28, 2016, 04:13:56 PM » Author: Ash
It depends on something in the lamp, and possibly on drive current. Those lamps are very widely used in switches here. Some go Black after some years. Some others are in fairly good condition still from the 90s, and those are in stairs lighting switches, where they glow all the time except when the switch is pressed
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #6 on: October 28, 2016, 09:21:16 PM » Author: RyanF40T12
There are quite a few light switches with the glow lights in one of my church buildings, original for when the building was built back in 1978.  The neons burned out years ago, but they still spark and flicker every now and then, especially noticable when it's stormy outside.  Something in the atmosphere really excites those neon bulbs.  Same thing for a burned out neon bulb in one of my surge protector strips.  Been connected for over 25 years, and from time to time the neon bulb goes crazy yet the little red LED on the side of the strip to indicate that the strip has power is still going! 
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #7 on: October 29, 2016, 12:29:18 AM » Author: Ash
You mean, the fire hazard strip. Those surge protectors are a fire hazard even when new. Open it and cut out the MOVs
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #8 on: October 29, 2016, 02:47:03 AM » Author: merc
It depends on something in the lamp, and possibly on drive current.
So the electrodes diminish in the same way as those in fluorescents? That explains the blackening and possibly also flickering (similar to fluros that can't start at the EOL).
There's probably only a little difference in normal switchings and zero crossings 100/120 times per second because electrodes aren't preheated and aren't hot enough.

An interesting experiment could be operating a neon lamp in a freezer and the other at a room temperature for the same time.
Another one: Run one neon lamp on 50/60Hz mains and the other on a HF power supply. (As Medved once explained here, fluorescents on HF last longer thanks to keeping the arc during the very short zero crossing.)
« Last Edit: October 29, 2016, 02:51:55 AM by merc » Logged

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Re: Neon Glow Lamps and Indicators - Short Life « Reply #9 on: October 29, 2016, 02:57:34 AM » Author: Ash
The Blackening is from the electrodes, and it is the reason for brightness drop..



There is no intentionally added emitter as far as i know, so i guess there are other mechanisms at work in the lamps that go flickery and unstable :

Maybe they use Kr85 as means to kick electrons out of the electrodes, and when that depletes, the lamp starts to depend on photoelectric effect (no photons hitting the electrode after zero crossing, so no restrike untill exposed to outside light), so not restarting after zero crossing unless hit by outside radiation or a surge of higher voltage

Maybe some impurities in the electrode act as emitter, and when they deplete (atleast on the outside layer), the lamp begins to need higher voltage

Maybe the electrodes are outgassing and this contaminate the lamp atmosphere

Maybe the electrodes initially have sharp end (where they were cut) that concentrates the electric field and makes for an easy initial strking region. Then those places are sputtered the fastest and the electrode becomes rounded, so striking voltage goes up
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #10 on: October 29, 2016, 08:05:11 AM » Author: wattMaster
What about having a glow-in-the-dark area around the Neon indicator to make it look more consistent? Does this whole short-life thing also apply to Neon indicators with a phosphor?
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #11 on: October 29, 2016, 08:42:05 AM » Author: Ash
Glow in the Dark materials in common use today are Zinc Sulfide and Strontium Aluminate. They can glow in different colors when activated (doped in small quantity, in a similar way to semiconductors) with different materials. Anyway, the following applies for all Phosphors :

Wavelength of light that excites the Phosphor < wavelength of light coming out of the Phosphor

The ambient light must provide enough energy (in every Photon, i.e. the color matters, not the brightness) to excite the Phosphor, and the Phosphor must provide enough energy to make PE effect

Visible light energy is between 1.5 eV .. 3 eV

Work functions of metals are between 2.x eV .. 5.x eV

So, if we start with 3eV light (400nm) this is enough for photoelectric effect to happen in several metals. 400nm- is present in most light sources (including the Neon itself), so with electrodes made of Iron or the like the Neon lamp can keep itself up

With 400nm it can also excite many Phosphors out there. But the wavelengths the Phosphors glow with are longer, mostly Greenish colors, and i dont know whether this would be sufficient to ovrcome the work function of the electrodes. This might work provided that the materials chosen for the Phosphor provides enough energy for the material chosen for the Electrodes
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #12 on: November 17, 2016, 05:14:18 PM » Author: jrmcferren
Neons usually flicker before they die completely. In fact I was using a power strip, the neon flicked with dim light in the room (phone flashlight, phone/laptop screen), was nearly steady with the room light on, nearly perfect with a bright light pointed at it and totally dead when dark.

The failure of a Neon is twofold. The electrode material sputters against the walls of the lamp blackening it, at the same time that material leaving the lamp increases the gap between the electrodes making the ionization voltage higher. A discharge lamp can be ionized by sources other than the voltage across the terminals, even non-ionizing radiation such as visible light is enough to do this in some cases. Another common method (especially common in fluorescent starters) was to include a slightly radioactive gas in the mix inside. The ionizing radiation of this gas made the ionization of the gas inside the bulb easier and faster especially in a starter can where there is little to no light when the voltage is initially applied.

Neon Lamp manufacturing today no longer has to be done to as tight of tolerances as decades ago. These days neon lamps usually operate for the sole purpose of indicator lamps, in the past neon lamps were also staples of electronic circuits and repeatability between lamps was important. Neon lamps were used in relaxation oscillators and even early calculator and computer circuits. In addition special neon and argon tubes were made to operate as voltage regulators, but those were actual electron tubes and not simple lamps.
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #13 on: November 17, 2016, 05:22:23 PM » Author: Ash
Most NE2 derivatives (so all the Neons in indicators) are designed with striking voltage around 80V. The line peak voltage is 170V for 120VAC - thats 2X, or 310V for 230VAC - thats 4X the lamp's striking voltage. The thickness of the sputtered layer frm the electrodes is tiny, so the change to the gap width is nowhere near 2X

Maybe the real reasn is not as much the widening of the gap but that sharp ends on the electrodes (from cutting at time of manufacture) get sputtered faster and this makes them rounded, eliminating the sharp points
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Re: Neon Glow Lamps and Indicators - Short Life « Reply #14 on: December 06, 2016, 02:10:38 AM » Author: waterbug
Are you guys talking about this lamp?

Last time I hook it up to a 9w PL-S lamp ballast, and the thing grew so bright and after like 5 minutes the bulb cracked and no more fireworks Cheesy

Quite some fireworks though.
« Last Edit: December 06, 2016, 04:22:28 AM by waterbug » Logged
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