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Re: some questions about tc design

Hi Alex,

At 02:25 AM 8/6/99 -0700, you wrote:
>i was foolin around on the internet one day, and i came across a home brewed 
>tesla coil page. it immediately caught my fascination, and for the past few 
>weeks i've been cruising the tesla coil webring, reading all the information 
>i possibly could, and i almost think i'm about ready to start designing my 
>own coil.
>
>I worked alot around high voltage when i was in the navy (as an electronics 
>technician), and finally i might be able to put some of that education to 
>use ;). I'm going to start small, but i'd like to throw a few ideas, and get 
>some information, or some links.

Neat!  You sound like the perfect coiler candidate!

>
>first up, before i even think about starting construction, i need to think 
>about protecting my mains :). This is one area that i haven't been able to 
>find a whole lot of information on, just a few ascii-sketches. does anyone 
>have any circuit schematics for keep the RF away from the power supply? I'd 
>like to find a few circuits that have been tested, and are known to work 
>before i try designing my own (and find that i've just blown up every 
>electrical appliance in the house).

A GOOD question.  Tesla coils are not too deadly on the AC line side.  You
can very adequately protect from bad things going back down the AC line.
However, the output arcs need careful attention.  Tesla coils can arc
through walls and hit the coax for the TV, phone lines (I did that, bye bye
answering machine :-O) or the AC line.  AC wiring is pretty robust and low
impedance but if anything sensitive is near, it could do damage.  Many of
us have hit light fixtures and such with no effect.  You should find a spot
without TVs, computers, and other expensive or sensitive electronic stuff
nearby or on the same circuit.  Then find a GOOD ground.  The ground rod
thing is pretty good or a close copper/steel water pipe.  I don't like the
house wiring grounds for TC grounding.  The coil ground is meant to protect
you, first of all, from getting electrocuted!  Then worry about getting a
good RF ground.  Tesla coils like to drive about 10 amps of say 250kHz RF
into the ground.  So you need some pretty good strap or something to carry
that current.

Of course, be careful that an arc cannot hit some none electronic things
too.  Cans of spray paint, the gas can for the lawn mower, propane
cylinders, the dog, the kids...  can all lead to "unpleasantness" if they
get torched up!

>
>For the power transformer, i have several old computer monitors laying 
>around. i was curious if anyone has/had hacked one up and use the flyback 
>transformer inside as a supply.

If you want to go for things like that.  I would opt for car ignition coils
with driver circuits or microwave oven  transformers.  They are far better.
 Neon sign transformers are almost the standard these days so that would be
best...  Pole pigs and the "BIG stuff" are for a second or third system
when you REALLY know what you are doing.   Mistakes with equipment like
that are usually your last...

>
>for the capacitor, i was thinking about going with a plate-style design 
>(since i dont have a fish tank laying around). any recommendations on 
>materials? right now it looks like heavy-duty ziplock storage bags, aluminum 
>foil, and a whole mess of mineral oil.

You may want to see the archives at www.pupman-dot-com and search on MMC caps.
These are not too expensive and are fast becoming THE standard these days.
They have vast advantages over the bags and oil systems.  If "cheap" is
required, those beer bottle caps may be the way to go.  They are far from
perfect but the effort and cost is very low.  Tesla's own coil used that
system...  Personally, I am not and advocate of those "oily caps"...

>
>i dont think my spark gap is going to be that fancy (for my first project 
>anyways). possibly some of the 1" copper tubing i've got laying around, in 
>series. when i manage to free up some funds (and i've got my first coil 
>working), i wouldn't mind trying to replace the gap with a hv circuit (maybe 
>with a few power fets or something). i'd like to talk to anyone whos done 
>this, mainly about aquiring the components. I doubt radio shack carries a 
>ton of HV components :).

The simple gap will be fine for now.  People always "talk" about FETs but
the people actually using them....  Digi-Key (www.digikey-dot-com) has may
things that can be used for coiling and I use their stuff a lot.  They are
not that cheap though...

>
>I still have yet to design the primary/secondary. I'll do that this weekend 
>(hopefully i can get my hands on some of that software to help me out). any 
>thoughts on a good diameteter/length for a small coil project? i was 
>thinking 4" dia and 16-18" long. dont have any materials for the primary 
>laying around unfortunately, so it'll have to be store bought *sigh*.

I would go for about 24 inches and 22 or 24 gauge wire...  That is about
the best for the first coil.  4 inch diameter is very common...

>
>I'm not going for any kind of spark length on this one. if i can get the 
>thing working, i'll be happy. once its working, i'll upgrade/redesign 
>components as needed to get to an impressive spark length.

Be careful here!  Don't needlessly do something to limit spark length.  The
FIRST thing I hear when someone finally has some sparks is "how do I make
them longer"...

>
>anyways, nothing is down on paper yet (i plan on doing that this weekend). 
>hopefully before the end of the month i'll be almost finished constructing 
>the individual components, and on my way to putting them all together and 
>tuning it. *joy*.

That is actually pretty easy.  One thing you should do is keep track of
dimensions, part values, number of turns and other technical details like
that.  If you get stuck, people, like me, need that technical stuff to
figure out what's wrong.  So try to collect and keep track of as much
technical data as possible.

>
>any thoughts/ideas/useful links would be appreciated,although i've read 
>about 1000 tesla pages (yes, about a thousand...i've been reading up for 
>about the last week about 6-8 hours a day), and all of them provided a 
>little more insight into construction, but most just had pictures (which 
>make me drool at the thought of being able to do that myself ;)) and some 
>stats on the persons coil.

You sound like a true coiler already!!  You have probably already seen and
have a good idea for what is out there...

>
>after i get this coil finished, i think i'm going to do some work on 
>experimenting with uses for it (and getting it down as small as possible, 
>eventually). the mad scientist inside of me is screaming that there must be 
>thousands upon thousands of uses for a few megawatts of power ;).

The usual path is to make them as LARGE as possible :-))  It is interesting
the Tesla coils really have no common uses other than making cool sparks...

>
>and so another eccentric soul joins the world of high voltage fun (god, my 
>girlfriend is gonna freak out *insert insane cackling here*).
>sorry for the long post, but its usually not till i'm about this hit the 
>"SEND" button before i look back and it says 'message size : 8k' and realize 
>i've written a small book :).
>
>btw...anyone use thier tesla coil to power various HV devices? rail guns, 
>lasers, etc? just curious :).

Florescent tubes and those pinwheel motors...  don't expect to get too much
practical out of coiling.  However, that mad scientist thing will be very
satisfied...  If others don't seem impressed, I always tell them "The
closer you get the "better" it is!" :-))

Cheers,

	Terry


>
>-Alex
>(alex-at-xecu-dot-net if you want to send an email to me)
>
>
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