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Ooops ! I goofed (fwd)



---------- Forwarded message ----------
Date: Sat, 1 Aug 1998 18:46:42 EDT
From: RWB355-at-aol-dot-com
To: lochhaas-at-computerland-dot-net, tesla-at-pupman-dot-com
Subject: Ooops ! I goofed

Hi Dave,

 Hereīs Reinhard again. I goofed up something in my email. Please replace the
 section about FL-lights with the following section. I explained the starter
 system backwards. Sorry about that. I probably got hit by one to many sparks
 from my tesla coil.

Corrected version of answer to #4

4.  I got to examine the fluorescent tube circuitry in this bug zapper and
 realized I really don't know how this works.  What I've got is an iron core
 inductor in one leg of the AC feed that then goes to one pin at one end of the
 bulb.  The other pin at the same end goes to the starter (a neon bulb and cap
 in parallel) and then goes to one pin at the other end of the bulb.  And the
 other pin at this end goes to the other leg of the AC.  What's with this
 thing?

Answer:
All fluorescent circs work the same way. You have three basic parts: An
 inductor, a starter and of course the bulb (no dugh ?). 

What you call a neon bulb is really a bimetallic switch. When you throw the
 zillion volts house current into your F- lights the following happens: 110v is
 not enough to start up the lamp. Inside of the FL-tube are two filaments, one
 at each end, these are wired in series with the inductor and the starter. The
 current flows through the inducter, starter and filaments. The inducter surves
 two purposes. First of all it limits the current flowing thru the cold
 filaments (its like a bulb saver) and secondly it provides the start kick for
 the FL tube to ignite (really to ionize the gas as your bulbs donīt "burn").
 After the filaments heat up (the tube contains rare gases and a small amount
 of mercury. In a new tube that has never been used you can actually see the
 mercury drops if you look carefully.) some of the mercury vaporizes. As the
 electricity also flows through the inductor it stores energy in the
 windings/ironcore. (Inductor stores electric energy, once the applied current
 is removed the magnetic field collapses and induces a high voltage surge in
 the windings of the inductor)
The "neon bulb" switch also recieves current and the bimetallic strip heats
 up. After a  while the switch opens (I wrote closes in the first email, B.S.
 of course) and cuts off the current to the inductor. The stored energy is now
 released and placed across the tube (from one filament to the other side,
 where the second filament is) I donīt know how high the voltage is but a good
 guess is a couple of kVīs. This ionizes the gas inside of your FL- tube and it
 conducts (excited electrons). Presto you have light!. The rest of the mercury
 vaporizes and helps to keep the gas inside conductive. This is why FL-lamps
 need some time to reach their operating brightness. The high voltage is no
 longer necessary because the gas can be held ionized at a much lower voltage
 (110v). This is why FL-lights are called cold cathode lights or simply cold
 lighting (It is not the color temperature which gives these lights the name)
 The capacitor inside the starter is just there for good looks. No, really it
 saves the bimetallic contacts from burning up as it absorbs some of the energy
 of the inductor and prevents the contacts from oxidizing. The neon gas does
 the same and also heats (as it conducts) the bimetallic strip so that it stays
 open once the FL is started. This is also the reason why you canīt turn a FL-
 light off and instantly turn it back on. The bimetallic strip has to close
 (cool down phase) again before the inductor can be re-energized to give the
 tube its starting kick. (neon gas conducts in this space at about 70-90 volts)
 There is usually another cap connected directly across the mains to serve as a
 RF surpressor (interferance surpressor, so your neighbors donīt get pissed off
 each time you throw on your FL-lights).
Here is a small experiment you can try (to show you what energy is stored in
 the inductor): Take a small relay and connect its coil terminals to a low
 coltage source (5v are enough): Place your fingers across the coil and
 make/break the contact to your ps. You will be surprised as to what you feel.
 This experiment is not dangerous, so donīt worry. Now you know why
 professional circuits have a diode connected anti-parallel to the coil of the
 relay.
The common FL- circuit has some drawbacks, however. As the tube gets older, it
 becomes more and more difficult to start the lamp. You notice this in the form
 that your FL-lights start to flicker and take longer than usual to get
 started. In really bad form they even flicker when they are running. This
 means you have to renew you bulb. Modern circs have an electronic starter.
 This electronic starter has more than one advantage. The electronics in the
 starter can produce a much harder cut-off (of the current), so that the
 induced HV is much higher, therefore quicker starting. Older lamps start
 better, too. As they have no moving parts they donīt wear out as conventional
 starters do. Finally they have a safety circuit in case the lamp doesnīt
 start, they cut off the current until you flick the switch off & on again.
 This means dying lamps wonīt bug you with their annoying flicker and it keeps
 RF interference to a minimum and reduces wear and tear on the lamp (if itīs
 dead who cares) and more importantly on the inductor.
Using a FL-lamp in a tc circuit or in a battery powered light works somewhat
 different. These lamps usually have a HV / HF (>2kv-at-40 khz-at-low amperage)
 inverter powered with a transistor oszillator and a ferrit xformer. In these
 cases the gas inside gets excited (just like you, when you see your tc
 working) and gives off light (photon emission) as the electrons fall back into
 their stable state. I donīt want to get into physics right now. You can read
 about this in some kind of physics book. You donīt need the filaments in this
 circuit. This is why you can use your dead FL-lamp to test your tc. It just
 has to have a good envelope.
One last word. If you want to build big tcīs. Start out with a small one first
 and build up your experience and building skills. The FL-lamp tc test
 described above should only be used on small teslaīs (<1kVA input power).
 About 90% of the tc experiments described elsewhere can be done with any tc.
 The bigger ones are of course more interesting, but start small. For more
 information on why read the saftey FAQ from the TC-Ring.



bye,
Reinhard

As one of my favorite sayings go: If it doesnīt work throw another million
 volts across it (or use a hammer ?)
I did use an "electronic hammer" (editor) on this stupid mistake