Fluorescent bulb types...

[Existential Angst]

Awl --

I have a basic understanding of how these tubes work (iirc, they operate off the Franck-Hertz ionization), except for the single pin 8' jobbies, that you don't have to twist to install -- really neat.

I thought tubes needed a filament at each end, to get the thing started? Hard to have a filament with just one terminal, no?

Do these types compensate with a higher starting voltage, and thus don't need filaments?

In bulbs with filaments, once the whole bulb is lit up, those filaments are cold, right?

I have only seen single pin in 8' bulbs. Why is this?

Someone posted an inneresting link on all-that-is-fluorescent not too long ago. I looked at that link, very nice, but I didn't see this topic.

[stans4]

They don't have a filament because the ballast supplies a high-voltage pulse to start the arc. They've historically only been used in industrial settings where lighting was run off 208/240/440/480 and the magnetic ballasts could be heavier duty and more expensive. Shorter ones can do the same now with solid-state ballasts, the filaments are still there to provide backwards compatibility for older fixtures. You don't HAVE to have a filament to warm things up if you've got enough voltage to start the arc. That method works even if the filaments are busted.

On looking around, 6/30/2010 is the last date for manufacture of the older magnetic ballasts in this country. One of those "green" things that got passed without a lot of fanfare.

Stan

[Jon Danniken]

Thanks Stan, I wasn't aware of that. Doing a little digging, I found the following from

Jon

[Ned Simmons]

The "filament" in a fluorescent lamp is usually referred to as a cathode. The 8-foot single pin tubes have a tungsten cathode that's the same as those in bi-pin lamps; it's just connected in a loop rather than across the two pins. Once the lamp is lit, regardless of whether the lamp has one or two pins, the cathode has the same function -- it's the source of the discharge that excites the phosphors on the lamp envelope. The cathode has a heavy central core with a loose "basket" wound around it that enhances emission.

While looking for a picture of a cathode this patent caught my eye. I designed and built the feeding mechanism and high speed cutter described in the patent. I didn't realize 'til now the process had been patented.

[Lewis Hartswick]

Well not quite, they are pretty hot due to ion bombardment. ...lew...

[Existential Angst]

So the cathode is heated, right? Which means it needs TWO connection wires, right? Is that single pin somehow segmented/insulated for two conductors??

Once the lamp is lit, regardless of

Does this mean that the cathode(s) *stay* heated, while the bulb is operational? Or less heated upon steady-state? Or cold?

[Don Klipstein]

The cathode is heated only by the arc. Fluorescents with only one pin on each end can only work with a general class of ballasts that is called "instant start" in North America.

In instant start lamps, the cathodes are only heated by the arc. Fluorescent lamps in preheat fixtures, once they are started, have their cathodes heated only by the arc.

- Don Klipstein ( [e-mail])

[larry]

There are the lamps you mention, which always have a filament at each end, whose heat sustains the ionization. It may be preheated (voltage across the filaments) to help start the ionization of the mercury vapor, or very high voltage to start the ionization. Once operating, the current thru the vapor and filaments keeps them heated. hot metal makes a good electron emitter.

The other type of fluorescents are called "cold cathode" and don't depend on filaments. They use an electrode at each end and use a current limited high voltage supply, and a fine tuned blend of rare gases at specific pressures. These are long life and cool running, used in somewhat permanent installs like cove lighting and advertising signs.

Don's webpage has info on lighting devices and technologies- members.misty.com/don/f-lamp.html

-l

[whit3rd]

Well, relative to the service life of incandescent lamps (1000 hours more or less) they have a long service life. The collection of tricks for starting them, though, includes small amounts of radioactive gas with a few years half-life. Twenty years from now, an attic incandescent lamp will come on every time, your attic CCFL won't.

[Martin H. Eastburn]

I had those in my shop in the other house. This shop (sob) are monster

8' single/double - don't know yet - 20' in the air. Wish they were T16's. The small, green ended very long life types.

Mine won't start well if cold. Today I got them lit mid-day for use at dusk.

Mart> Awl --

[Richard J Kinch]

Oh, no. Another thing I have to hoard!

On the other hand, Diamond strike-anywhere matches seem to be back!

[Stormin Mormon]

I remember couldn't find strike any wheres for ages. Found them in an old country store, and bought more than one pack.

[Doug Miller]

When are you going to fix your newsreader configuration so it puts your sig at the bottom where it belongs?

[Don Klipstein]

CCFL is not CFL - single C is "Compact", double C is "Cold Cathode". Some units are both, usually with wattage in the 3 to 9 watt range, and most 9-watt CFLs only qualify for one C. :)

In general, CFLs having integral electronic ballasts (including over

99.7% of spiral type units and over 99.8% of spiral type units with screw bases allowing substitution for incandescents) appear to me to not have added radioactive isotopes or notably harmful radioactive materials in order to start. Electronic ballasts, "rapid start" ballasts, "trigger start" ballasts and "instant start" ballasts *at least generally* negate the need for "glow switch starters" which are the main usage of radioactive materials for fluorescent lighting.

- Don Klipstein ( [e-mail])