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Existential Angst

"Ned Simmons" wrote in message
...
On Wed, 10 Feb 2010 13:17:53 -0800 (PST), wrote:

On Feb 10, 1:30 pm, "Existential Angst"
wrote:
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.

--
EA

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.

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.

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
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.

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

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.

http://www.freepatentsonline.com/7462991.pdf

--
Ned Simmons