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.


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