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Steve Conner

Sat Jul 15 2006, 06:45PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

wrote ...
But once you grow up, where is the fun

Meh, I'm practically middle-aged, have a mortgage, and I'm still having fun. I heard the fun really stops when you have kids. >.<

Gate drive is much easier if you use a resonant drive circuit that puts out a sinewave like Richie did. I believe BP is using resonant gate drive now since he replaced the gate resistor with an inductor. The only danger is getting so much drive voltage through resonant rise that you blow up the MOSFET.

I don't think there is any drawback to using the primary itself as a choke like you're doing. Richie probably never thought of it. I think he was just thinking of commercial RF power amps. They need a separate DC bias path because they have to give an output from a socket to drive whatever load you plug in. The only thing you must remember is to put an RF bypass capacitor from the "Cold" end of the primary (the end connected to the DC supply) back to the place where the MOSFET source pin and Class-E snubber cap join. This completes the RF circuit and stops your power supply wiring being part of it.

I think it'll be impossible to match to an unloaded coil, since it's practically all reactive with hardly any actual real resistance. The resistance is what you're trying to match.

BP: Build a small DRSSTC then.

Marko

Sat Jul 15 2006, 10:12PM

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

After I put the coil in faraday cage waveform repaired and the coil drew much less power, same as with breakout.
I blew my last IRFP450 having only 150's left, and input voltage is limited to some 30V, but I can still observe all the effects happening.

I tried to compesate this loading with bigger cap (22nF 100V from old fluke insrument, unknown construction) and less primary turns but that was the point where I blew the mosfet up

Could be tons of reasons, but anyway it's interesting to work on toploaded class-E coils

I'l keep you informed, now some more spark pics with various topload-toppings..

ragnar

Sat Jul 15 2006, 11:08PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Some shorter exposures or videos would be nice =)

Marko

Sun Jul 16 2006, 01:39PM

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

The first is done by putting some cotton on the topload. Arcs ignite it and streamers emanate from tips of the flame.

Even at short exposure (200ms) and lowered ISO it dazzled my camera. I didn't try this again as carbon was ruining my topload.

Second pic is steel wool, wittingly taken using 8 second exposure for sparkles a la Richie Burnett style

I also finally had some sucess with bigger (22nF) cap but some 15nF would be more preferable

I'm using 2 primary turns now and I minimised all inductances, but frequency of the LC still seems to be edgy low. May prove good for compensation of big streamers and loading..

PS.
I added a modulator to the coil, modulating inhibit pin of '4046. It worked nicely, lowered power draw but didn't help much making longer sparks.

Interesting is that at higher powers coil breaks out from topload on 'multiple places' like a small SGTC would do.

One bizzare thing I discovered is some dim 'modulation' of interrupter signal at about 2Hz.
It can be easily heard from a small streamers and from mains transformer.
I'm completly unsure what causes it another 'mystery' from this coil.

ragnar

Sun Jul 16 2006, 01:49PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Got waveforms and circuit pics? :P

</hassle, hassle>

Marko

Thu Jul 20 2006, 08:07PM

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

This coil is really endless source of trouble, and I can never tune it for best output without ruining class E operation.

With new 15nF MKP cap(s) mosfet runs even hotter than before. I tried 2,3 and 4 turns with varying capacitance but I still did nothing good.

Top winding of my secondary is still burning out, causing trouble with measuring and I'l probablly never fully fix that.

Now I tried to shoot some waveforms but they tend to oscillate with variation of load due to spark, 50Hz ripple, arcing connections inside the resonator and massive heating of mosfet and it's surroundings :p

But it does resemble class E operation in somewhat.

more pics

I coated the board with solder to prevent rusting of copper. Regulator will be in buck-boost mode to provide power to all the electronics regardless of input voltage.

I get a opposite polarity output but I don't thnk it's a big deal, since unregulated input won't appear in the circuit anyway.

ragnar

Sun Jul 23 2006, 01:34PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Just posting my latest pics here -- these are from a different (nicer) camera, and are crisper and (I find) a truer description of the coil and discharge.

The last few pics are a premature announcement of first light of my UOMFGSTFUHFSSTC which runs at 9.5MHz.

1153661646 63 FT12529 Radiofrequencyburn

1153661646 63 FT12529 Tribreakoutdetail1

Marko

Sun Jul 23 2006, 01:59PM

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

You can put pics in rows to save some space, looks neater =)

9,5Mhz is nice but I doubt you'l beat some spark recods with that :/

I think you can improve Q and sparks by using uber thick or multifilat wire, the acrylic secondary you had would be great.

And try not to fry yourself with that thing :p

ragnar

Sun Jul 23 2006, 03:08PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

U stands for uber.

...

Sun Jul 23 2006, 05:17PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Any thoughts of putting that uber 1337 anticoil resonator on your Uber Oh My F***ing God Shut The F*** Up High Frequiency Tesla Coil

Or could it the the Uooh Ouch My Finger Got Struck by The Flaming Uber High Frequiency Tesla Coil

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