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Re: Source of NSTs and bombarders (fwd) A bombarder is... (fwd)
---------- Forwarded message ----------
Date: Thu, 16 Jul 1998 15:56:04 -0500
From: Eric Davidson <edavidson-at-icva.gov>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Source of NSTs and bombarders (fwd) A bombarder is... (fwd)
Jim:
ALL fluorescent lamps used in lighting applications are HOT cathode
lamps. The 40 watt 48" rapid start types have an electrically heated
filament. The 'slimline' 72 watt 96" single pin lamps have their
filament heated by the impact of the electrons flowing through the
tube. A heated electrode enhances electron emission, and lowers the
operating voltage of the tube. Cold cathode lamps are different from
fluorescent lamps. They are very similar to neon (sign) lamps. The
tubing used in cold cathode lamps is larger in diameter than that used
in neon signs. Since that tubing is larger, more current can and must
flow through the tube. The electrodes used in cold cathode lamps are
not heated at all. Yes, there is some heating from the current flow, but
it is not required for correct operation of the tube, it is merely a
result of the tube operating. Also, the electrodes in cold cathode lamps
are NOT filaments as in fluorescent lamps, but are hollow metal
cylinders or cones, depending on the manufacturer. Both neon and CC
lamps may be considered 'fluorescent' when they are pumped with
argon/neon (1050) and a phosphor coated tube is used. All green, blue,
purple etc colors are the result of a phosphor coated tube. Even neon
can, and often is, placed in a phosphor coated tube. The UV that the
neon emits excites the phosphor and makes orange or pink etc. ALL 'neon'
sign type lamps are cold cathode. Cold cathode lamps are not used very
much anymore. Most of them are found as lighting inside large
commercial 'K-Mart' type signs. Cold cathode transformers would be
quite desirable for TC use, usually 12-15 kV 120+ mA, but new, they are
quite expensive and used ones are very hard to find. Hope this helps.
Eric
Tesla List wrote:
>
> ---------- Forwarded message ----------
> Date: Thu, 16 Jul 1998 07:57:58 -0700
> From: Jim Lux <James.P.Lux-at-jpl.nasa.gov>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: Source of NSTs and bombarders (fwd) A bombarder is... (fwd)
> > Greg
> A cold cathode transformer is used to drive a "cold cathode tube", of
> course, which is another name for a fluorescent lamp. There are two
> general flavors of fluorescent lamps: hot cathode and cold cathode, and
> sort of a cross between the two. A ccft uses a HV spike to ionize the
> gas inside the tube, which then emits UV which makes the coating glow. A
> hot cathode tube heats up a couple of filaments first, then strikes the
> discharge, then, usually, turns off the filaments. Probably the most
> common application of small CCFTs and HCFTs is in backlights for LCD
> panels. However, they are also made (by neon sign shops for instance)
> for applications much like neon signs. I had a couple of CCFT halos (as
> for an angel) made once. The advantage is that you can put a whole
> variety of phosphors in the tube to get different colors or get a nice
> white (try and get white, with neon) (or paint the outside of a white
> tube), and they run at lower voltages, generally (less than 100 volts
> for my halos, once the discharge was started). The CCFT backlights run
> at even lower voltages (tens of volts).
>
> What you can't do with a CCFT is make a long tube (many feet), whereas
> with neon you can.
--
Have a good day!
Eric Davidson
edavidson-at-icva.gov