milo@ndmath.UUCP (Greg Corson) (01/16/88)
I recently read about a computer company using a neon tube (bent in
a serpentine pattern behind diffusing glass) as a backlight for it's
portable computer LCD screen. Their reason was supposedly lower power
requirements than an Electroluminescent pannel.
Is this correct? How difficult would it be to make a power supply that
would run off 6-12 volts to drive such a neon tube.
Also, two other question regarding gas discharge lighting...
1. If you created a glass sandwitch with a thin space in between and
placed electrodes along two opposite (thin) edges. When the thing was
powered up would you get an even light across the entire sandwitch?
(say the thing was around 6x6 inches.
How about if you used transparent electrodes covering the entire sheet
of glass, front and back? Even lighting or would you be likely to have
hot spots.
2. If you have a large volume (say about a square foot) with the proper
gas mix for a neon light and you put a number of small electrodes at
various places in the box, would you end up with streamers of light
between positive and negative electrodes or would a fairly large volume
of space light up? How about if you used two large flat electrodes
on opposite sides of the box? Would the whole thing light up?
Greg Corson
19141 Summers Drive
South Bend, IN 46637
(219) 277-5306 (weekdays till 6 PM eastern)
{pur-ee,rutgers,uunet}!iuvax!ndmath!milo
gwyn@brl-smoke.UUCP (01/16/88)
In article <636@ndmath.UUCP> milo@ndmath.UUCP (Greg Corson) writes: >How difficult would it be to make a power supply that >would run off 6-12 volts to drive such a neon tube. Shouldn't be hard at all. Use a multivibrator circuit as a fairly high-frequency oscillator and a transformer to step up the voltage. Xenon flash attachments for cameras do something like this (they actually charge up a capacitor rather than continuously powering a light).
max@trinity.uucp (Max Hauser) (01/16/88)
In article <636@ndmath.UUCP> milo@ndmath.UUCP (Greg Corson) writes: >I recently read about a computer company using a neon tube (bent in >a serpentine pattern behind diffusing glass) as a backlight for it's >portable computer LCD screen. Their reason was supposedly lower power >requirements than an Electroluminescent pannel. >Is this correct? How difficult would it be to make a power supply that >would run off 6-12 volts to drive such a neon tube. Sounds reasonable; glow tubes are efficient, cool, diffuse. How difficult? Depends on the required voltage, which you need to find out. A neon tube inches long could require kilovolts, which would be a pity, since up to a few hundred volts there are simplified, reasonably-efficient (30%-50%) high-voltage generator circuits from batteries, using a transistor with an inductive collector load. If you want to be unreasonably efficient, up to 85% or so, you must use a transformer designed for the purpose, with a proper drive circuit. Middlebrook (?) at Cal Tech has refined this to an art, and I believe he has a book out. Sorry that I can't provide hard details about the tubes themselves; my experience is with the DC-DC conversion part, which I have used successfully for small (100v) neon bulbs and xenon flashtubes (200-300v). Max Hauser / max@eros.berkeley.edu / ...{!decvax}!ucbvax!eros!max "For every complex problem, there is a solution that is simple, neat, and wrong." -- H.L. Mencken (as quoted by Ron Ueberschaer)
jimc@iscuva.ISCS.COM (Jim Cathey) (01/20/88)
In article <636@ndmath.UUCP> milo@ndmath.UUCP (Greg Corson) writes: >1. If you created a glass sandwitch with a thin space in between and > placed electrodes along two opposite (thin) edges. When the thing was > powered up would you get an even light across the entire sandwitch? > (say the thing was around 6x6 inches. > How about if you used transparent electrodes covering the entire sheet > of glass, front and back? Even lighting or would you be likely to have > hot spots. > >2. If you have a large volume (say about a square foot) with the proper > gas mix for a neon light and you put a number of small electrodes at > various places in the box, would you end up with streamers of light > between positive and negative electrodes or would a fairly large volume > of space light up? How about if you used two large flat electrodes > on opposite sides of the box? Would the whole thing light up? With DC/Low frequency AC excitation I would expect hot spots since neon gas has a hysterisis effect (different turn-on and turn-off voltages). Once one path was found through the gas, I would expect most of the current to flow along the first path found, thus loading down the power supply and preventing more paths from starting. With high-frequency (like radio) excitation things can get 'weird' (what with inductance of plasma paths and so on), so you might get acceptable results this way. Of course, high-voltage RF generation isn't trivial, and might have some drawbacks. (Can _you_ say FCC? Sure, I knew you could!) +----------------+ ! II CCCCCC ! Jim Cathey ! II SSSSCC ! ISC Systems Corp. ! II CC ! TAF-C8; Spokane, WA 99220 ! IISSSS CC ! UUCP: uunet!iscuva!jimc ! II CCCCCC ! (509) 927-5757 +----------------+ "With excitement like this, who is needing enemas?"