Re: Mini-coils?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Hi Chris,

Interesting idea for a power supply for a dinky little coil (which I just 
built a couple weeks back). Something on the order of 0.5" x 3.5" at 296 
turns of #30. I wound it on one of those CD trays which hold 50 blank cd's. 
It should be in the range of 8.6 MHz given the topload used. Everything's 
finished except the power supply for it (primary is on and 2nF MMC is built).

I drive right by EMCO about once a week (I try to take a trip up the hill 
once a week to keep an eye on our pcb/cable assy group located in the 
Sierra's). EMCO is near the top edge of the foothills near Jackson, CA. It 
seems to be a relatively small building, but given the small transformers, 
they may not require much space. I'll try to stop in the next week sometime 
(maybe I can talk to their design engineer and get his view on their 
capability).

Take care,
Bart

Tesla list wrote:

>Original poster: Chris Roberts <quezacotl_14000000000000-at-yahoo-dot-com>
>One thing that I've always looked at to build one of these micro coils are 
>these mini HV power supplies from EMCO: 
><http://www.emcohighvoltage-dot-com/>http://www.emcohighvoltage-dot-com/ If you 
>look at the "Q series" they are these puny little DC to HVDC converters. 
>The current coming out of the really high voltage models is pretty small, 
>but should work on that small of a coil. You could then run the thing off 
>of 3 1.5 volt batteries - probably C cells or something. I've always 
>wanted to build a coil this small, but so far my large coil keeps killing 
>parts, and replacing them isn't cheap. =( Good luck!
>
>Tesla list <tesla-at-pupman-dot-com> wrote:
>Original poster: The MCP
>
>This was a cute little thing I thought about a while back. I was considering
>taking some batteries for power, one of those little step-up switching
>transformers you find in portable fluoresent lights, and using it to power an
>ultra-tiny tesla coil (secondary maybe 1-2 inches tall, .5 or so dia).
>Methinks it'd be a cute demonstration coil.
>
>The problem I see is creating a good secondary. If you shoot for 750 turns,
>that comes out to 350 turns per inch, which would require *42 gauge* magnet
>wire. Not only will you be using something far smaller than hair and rather
>ductile, but the 100 feet of wire used would have almost 160 ohms of
>resistance (The same as my coil). I can't imagine this having a good effect
>on performance. On the other hand, if you can stand to settle for a mere 500
>turns! on the secondary :) then the resistance drops to 86 ohms.
>
>I went to the new version of JavaTC, and it says that this baby coil will
>resonate at 4.86Mhz, and has .91pF of self-capacitance.
>
>I did a little theorizing on the primary coil, and (if you use a 12.5nF cap)
>it should be a single 1-inch diameter turn at the center of the coil.
>
>I haven't quite figured out what to use for a power supply (Current-limited +
>wall plugin or batteries + mini switching supply) and I was wondering if it
>would be possible to use a high-speed power transistor to switch it.
>
>Well, that's my cute idea for the day. My idea for the setup is to keep the
>electronics in a box, about 4" long, 2" wide, and maybe 1" tall. Then mount
>the coil horizontally above that, and just rise the 1-turn coil out of the
>box. Attach the ends of the coil to a pair of little balls on movable mounts.
>BANG, instant miniature tesla coil. Or no?
>
>The idea occured to me when al! l my friends were amazed by the coil I already
>built (No one recognised the term "tesla coil" so I ended up calling it a
>"lightning machine." Sigh...), underperforming as it is. So why not make a
>cute little coil to play with?
>
>Plus, since it is (except for the transistor) a real tesla coil, you can use
>it to explain how they work. Ok, I'm done talking now.
>
>
>
>-Chris