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Tesla Coil Design issues.

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Ken M.

Sat Mar 31 2007, 06:58PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

I'd like to start by saying Hello to everyone in this forum group. This is kinda my first and ongoing attempt to get an actual operating tesla coil up and running.

I have a:
Primary: Helical 12AWG speaker wire with 16 turns wrapped around a 2" diameter PVC pipe with ~1/2" space between it and the secondary.

Secondary:
Height: 6" (From bottom winding to top winding)
Diameter: 1.25"
Wire AWG: 36 enamled copper wire
Coil form: Plastic florescent light case thingy
# of turns: ~1015

top load: Spun aluminum toriod 1" ring diameter and 6" overall diameter

Heres a picture of it:

Anyways my issue is that I have tryed various designs and setups with coil, everything from Jan's DRSSTC design to standard SGTC design and a design that used a HVDC power supply (From a flyback) to power this and I cna never seem to get it to work, With the exception of the HVDC power supply design which produced a 1/4" ultra thin arcing from top bolt with no topload on it. At least until the MMC tankcaps became a light show.

So I'm just wondering if could get some info maybe if it should have a bigger secondary? What kinda of driver circuit, i.e SS. DRSS, or the good ole fashioned SG. Any suggestions are greatly appreciated.

HV Enthusiast

Sat Mar 31 2007, 07:20PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

well, i guess the first question to ask what is your calculated (or measured) fres of the secondary. I'm guessing the resonant frequency is pretty high on that thing based on my gut feel.

Ken M.

Sat Mar 31 2007, 07:25PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

From what Teslamap 5 says its about 811.02K, but from what I gave that simulator\calcualation program only figures For a SGTC, but i'd kinda prefer to go wit heitehr SSTC or a DRSSTC if at all possible. To go along with that it'd be nice to be able to have it running with only perhaps 60v max AC or DC to drive the coil, considering I'm just after a coil that will produce visible arcs, say maybe 3-6 inchs max would be nice long would be cool but, for now I'll set my goals small.

Marko

Sat Mar 31 2007, 07:35PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Yep, Fres is going to be really high, about a MHz. I would either go with a small SSTC sucha s this one

or a small flyback powered SGTC. For a SGTC, you need way lower coupling; definitely a primary redisign, to flat or archimedas spiral and with something you can tap... 3mm full copper wire would be OK.

What caps are you using for your MMC?

Ken M.

Sat Mar 31 2007, 08:01PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

Before the light show I think....they were a 3x3 of 2.2nF 7500v as for right now nothing, just because I was kinda looking for a suggestion towards what type of TC go with and it looks like it'll be a SSTC.

Marko

Sat Mar 31 2007, 08:18PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Capacitor type is very important. They must be polypropylene, at leas foil or foil+ metallization.

I also think small SSTC with Steve's circuit would definitely be a good start for it...

Ken M.

Sat Mar 31 2007, 09:08PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

Yea I tried that design "Slightly" But a few different parts and it was a bad.

A new question popped into my mind while searching for the parts since I didn't have most of the major parts for that design, With the amount of RF and noise produced by a coil what would be an operation MAx distance for the antenna to be away from the coil, and still get the stacato effect?

Bennem

Sat Mar 31 2007, 10:33PM

Registered Member #154 Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260

800khz secondary is too high for a DRSSTC,
Derek Woodroff has a small coil working at around 500khz,
my smallest DRSSTC runs at 400khz and
that was rather challenging!

Ken M.

Sun Apr 01 2007, 03:22AM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

well...I was kinda thinking\ try to find a way to test some parts of mine out, and so I decided to try another of Steve's (Ward) DRSSTC designs out namely

with all the same stuff with the exception of his power supply, only because I have some PC supplys sitting around and they have a fair amount of current available. When I first tryed it I didn't think the 555 timer wouldn't matter untill I burnt out a hrz445 and had my PSU shut down several times, so I added the timer with a reduction of the the 10k resistor just before c5 and swapped the fet with the last high current 100v fet I had... To my amusement i was able to draw an arc only about 1\16th an inch I believe heres a few pics mostly just for my own proof that i'm making HV and just getting lucky.

If ur wondering, I'm running it off the 12v out of the PC PSU for this aside from upping the voltage and other suggestions, would be terrific!

Ken M.

Tue Apr 03 2007, 09:50PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

Ok, well after having Fet failure at 12v (Fet was rated for 55v at 20A) and getting unacceptable arc lengths I decided to revise my secondary,

Old secondary: 1.25in Dia
5-5.5in tall
~1000 turns of 36AWG Magnet wire

Fres: ~800KHz

New Secondary: 2in Dia
~8in tall
~1500turns
New Fres: ~400KHz

I did this to seeif it would increase the output and allow the fet/fets to run a little bit smoother instead of pumping high Frequencies and current into it. Anyone have any ideas how much this will improve my output with a 12v in, or even upto ~30v in? P.S. Winding a secondary by hand with 36AWG wire sucks!

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