What kind of light is this?

[RonM]

Does anyone know what kind of light (often seen in nightlights) has two rods that glow when energized? No filament. They seem to run forever w/o burning out.

Are these related to neon lights? What about their efficiency? I really need to know how they compare to LEDs and incandecents.

 

[The_LED_Museum]

These are NE-2 neon glow lamps.

The bulb is evacuated to vacuum and then filled at low pressure with 99.5% neon and 0.5% argon (the classic Penning mixture).

When a voltage greater than about 70V is present across the electrodes, the neon gas inside emits an orange to sometimes salmon tinted orange glow.

This lamp is a negative resistance device, meaning the more current passes through it, the lower its resistance becomes (eventually presenting itself as a dead short across the house wires), so it must always be used with a 100K series resistor when used at 120V line voltage. They explode with a loud pop if you forget the resistor.

Note: If connected to a DC voltage source, only one rod will glow.

They aren't terribly efficient, using 0.5 to maybe 1mA at 120 volts. Average power consumption for this type of bulb is around 150 milliwatts.

 

[RonM]

Thanks Craig. Helpful as always.

 

[Daniel Abranko]

Another fascinating thing to note is that as neon bulbs get older, the neon slowly escapes, and they begin to flicker. This in and of itself is not too interesting.
But the fact that the blinking is influenced by the incident light upon the bulb imparting energy to the neon atoms causing them to ionize more easily is fascinating!

In the dark the bulbs tend to stay dark and blink whenever a stray photon or few hundred hit them, but if you shine a bright light at them, they will continuously light...

-Daniel

 

[Chris M.]

But the fact that the blinking is influenced by the incident light upon the bulb imparting energy to the neon atoms causing them to ionize more easily is fascinating! In the dark the bulbs tend to stay dark and blink whenever a stray photon or few hundred hit them, but if you shine a bright light at them, they will continuously light...

Fascinating indeed. I have a green "mains-on" lamp just over there, see....oh no I forgot, just typing it...well anyway it`s got a NE2-G (same idea as the NE-2 but with a xenon/argon fill and a green-glowing phosphor coating on the glass) type indicator in. The silly thing is always flickering during the daytime, but doesn`t at night, just glows steadilly. I always wondered why, thought it was just due to the mains supply being more steady at night (due to less people turning stuff on and off compared to daytime).

Shining an Arc at it just now did not make it flicker, perhaps it needs full spectrum daylight including UV/IR content to do it....

 

[The_LED_Museum]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Daniel Abranko:
Another fascinating thing to note is that as neon bulbs get older, the neon slowly escapes, and they begin to flicker<HR></BLOCKQUOTE>

Used to be you could fashion a crude radiation detector out of a neon bulb.
You slowly increase the voltage across it until it *just begins* to fire, then back it off just until it goes out.
Then you just aim the thing at something radioactive, such as a piece of uranium ore, and the neon bulb will flash whenever it is struck by a few gamma rays.

 

[sunspot]

Also you can tie the leads on a CB radio antenna. It will light everytime you transmit.