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Re: Carrying a Full Load (fwd)



---------- Forwarded message ----------
Date: Sat, 1 Aug 1998 17:33:00 EDT
From: Alfred A Skrocki <alfred.skrocki.sr-at-juno-dot-com>
To: tesla-at-pupman-dot-com
Subject: Re: Carrying a Full Load (fwd)

On Fri, 31 Jul 98 16:35:08 PDT Dave Lochhaas
<lochhaas-at-computerland-dot-net> wrote;

>Hi to the List from Mid-Missouri,

Welcome to thelist Dave!

>These are my questions:
>
>1.  I have a beefy old bug zapper that's spent the last fifteen years 
>in the garage in storage so it didn't suffer much when I took it 
>apart.  It has a transformer that will draw about a quarter inch arc 
>across a gap.  Can I build a small Tesla coil with this?  I've search 
>all the websites but can't find any reference this.

Sure Dave the transformers in most "Bug zapers" are rated at 5KV at 9ma.
Small for driving a Tesla coil but workable. I'm not sure if these
transformers are current limited so I would use a current limiting choke
in tesla coil usage. Remember these things don't normaly spark
continously but are designed to have occasional discharges.

>2.  The secondary of the above transformer has a red stubby 
>cylindrical component that is marked with:  MDC     10000M     Z5R     
>18KV.       What is this thing?

It's a high voltage capacitor it enables the transformer to put more
energy into the occasional spark that jumps when a bug gets in the path.

>3.  I've read that spark gap arcs, like arc welding arcs, emit harmful 
>UV.  Does a Jacobs ladder also do this?  What is the physics by which 
>UV is produced in arcs such as these?

Yes, spark gaps put out a lot of short wave U.V., Jacobs ladders but out
a little U.V.
but not as much as a high current spark gap! The physics is the same as
for almost all light generation, the atoms in the air get bombarded with
high speed electrons nd this causes their outer electrons to jump to a
higher orbit and when they snap back to their origional lower energy
state they release the extra energy as light in th U.V. band of the
spectrum. The factors that determine the frequency of the light emited
are the particular energy level to which the atom is raised to.

>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?

The operating principle of almost all flourescent lamps are pretty much
the same.
Inside the flourescant tube is a heater and a conductor at each end of
the tube, the tube is under a partial vacuum and there is a little
mercury put in before it is sealed. the inside of the tube is covered
with phosphors which when exposed to U.V. emit the desired colors of
light. Now when the tube is started the heaters are energized and they
vaporize the mercury in the tube and the thermal switch (what you thought
was a neon bulb) disconnects the heater and connects the line voltage
across the tube through the inductor
this causes a kick back from the inductor which puts a momentary high
voltage across the tube and a plasma arc is started. this mercury vapor
arc emits strong U.V radiaion which strikes the phosphors and is
converted to the desirable wave lengths of light. Now this arc has
negative resistance and would keep pulling more and more power untill the
tube would explode, but instead the inductor limits the current flowing
through the tube and it stays lit at a safe power level. BTW the better
"Bug zappers" like the ones made by "Stinger" use the primary of the High
voltage transformer as the current limiting inductor for the flourescant
tube.
                               Alfred A. Skrocki
                          Alfred.Skrocki.Sr-at-JUNO-dot-com
                 Visit my Do-It-Yourself Aquarium WEB page at:
                  http://WWW.GeoCities-dot-com/CapeCanaveral/6251

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