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flaming mini TC with single IRFP450

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ragnar

Tue Nov 06 2007, 02:36PM

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

wrote ...
Ooh, nice coil! How many turns are there on it? (Approx, of course)

It's wound with 0.15mm wire, I think there's around 350 turns on it.

wrote ...
Also, I have a question- Will this circuit: run a tesla coil? If it does, I'm going to try one really tiny one someday. I wonder if I can beat the size.

I haven't had a proper look at that one yet, but the comments seem to indicate it works great on low voltages; watch out for the difficulties that will arise with high frequencies (inherent with small coils!)

wrote ...
Though of course, the smallest is that 3cm one I saw some time back. Nanotess or something, I think!

Yep, those SSTCs with the driver electronics inside the secondary sure were cute... but I'm looking for proper amounts of breakout!

With a better driver circuit (give me another rainy evening and some more ammonium persulphate), there's a whole lot more performance to be had from this coil; I'll keep the secondary and the box exactly as they are; they're such a perfect match!

AndrewM

Wed Nov 07 2007, 05:01PM

Registered Member #49 Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362

nice!!

Compact, elegant. Nice tight coils, and good lookin box. I wonder, what it's performance like in the dark?

oh and the tesla coil is nice too.

ragnar

Wed Nov 07 2007, 05:48PM

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

Two good ideas come to mind tonight:

A) instead of the cliche'd LED always pointing at the camera, I should instead place it under the secondary so that it highlights the acrylic top.

B) it IS possible for me to fit a class-E amplifier in this tiny box; if I omit the matching network and associated magnetics altogether, I could put the primary in series with the drain, which, while naughty, works OK at lower frequencies with looser specs.

Firnagzen

Thu Nov 08 2007, 02:56AM

Registered Member #567 Joined: Tue Mar 06 2007, 10:55AM
Location: Singapore
Posts: 147

ragnar wrote ...

A) instead of the cliche'd LED always pointing at the camera, I should instead place it under the secondary so that it highlights the acrylic top.

Bad idea! It would wash out the spark, I think. Noooo good.

Make a tiny little torroid, or maybe buy a small spun aluminum one, maybe. That would look nice.

EDIT: Perhaps a screw cup, whatever that is. Like here:

ragnar

Fri Nov 09 2007, 06:42PM

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

Toroids are for wussies and not CW people

I might need a shoehorn to fit some more stuff in here...

Newdrv1

click to enlarge

Too much plasma is never enough -- I've already started V2 knowing I won't have to fit a matching network in there. Proper MOSFETs and Class-E here we come!

The secret at the moment is to keep all the semiconductors on the edges (and the universal grounding sure makes the single-layer board layout neat).

The potentiometers allow for frequency and duty cycle offsets. I'm hoping to only ever have to set them once, at which point I left the legs long enough to fold them down sideways out of the way (the next secret!)

After all that, I've just physically confirmed that the donut core I intend to use on the modulator will fit down into the semiconductor sandwich. I may get away with heatsinking the TL494's push/pull MOSFETs to the lid.

(Otherwise we could end up with a Chinese puzzle of screws which cannot be tightened because there's a lid in the way, but removing the lid removes the objects which one wishes to tighten. =P)

Long live the IXDD414, let's hope it never goes out of production.

Newdrv2

click to enlarge

Newdrv3

click to enlarge

Newdrv4

click to enlarge

...

Sat Nov 10 2007, 12:27AM

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

wow

That is amazing!

Although, I don't quite see why you need such huge transistors on the output of the tl494, shouldn't it be able to drive the the ixdd414 just fine without some huge transistors helping it? Or am I missing something...

Can't wait to see it working!

ragnar

Sat Nov 10 2007, 02:34AM

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

Woops, maybe I need to show higher-resolution photos where you can read the part numbers and see where the traces go more clearly --- this is a completely new design =) The TL494 doesn't exist yet!

There's a 74HC4046 in there; I scrapped the surface-mount regulators (because I am pulling more than 100mA).

So the packages you see are an LM7805, an LM7812, an IXDD414 and an IRFP450. =)

WaveRider

Sat Nov 10 2007, 09:45AM

Registered Member #29 Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500

Way to go Matt! It looks great! I think small coils are great too... Here is one that I am working on at the moment...

Keep up the great work Matt... It's great to see your girlfriend getting into coiling too....

ragnar

Sat Nov 10 2007, 04:50PM

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

WaveRider wrote ...

Way to go Matt! It looks great! I think small coils are great too... Here is one that I am working on at the moment...

Yours is bigger than mine... but one is supposed to argue about how you use it

I'm guessing that's where your DEIC420 and IXYS RF MOSFET are headed? :P

In order to screw the secondary down to the box, I had to modify this second PCB. Unfortunately, I drilled straight through the PLL chip without looking! WOOPS! Turns out I had *not* placed it off-centre as I had intended to. So I made another board with a few revisions, including allowing space for that screw in the middle.

Here's today's progress on the coil, including first breakout. After fitting in bypass and shunt capacitors, I can well and truly kiss that TL494 board goodbye. If I have to fit a single reactive component within the box, not to mention plugs/sockets, it quickly becomes impossible. I was too optimistic! =P

I'll take some photos of the drain waveform later.

Newdrvb1