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Messages - Magneticitist

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If I thought I could give a comprehensive explanation of the circuits I made using this topology I definitely would. I've been waiting for someone smarter than me to come along and really dig into this topology because it seems far too under-demonstrated. It seems like you've already fleshed out how it works. The most impressive iterations I saw were on Chinese websites (hard for me to even re-find again) and that's where I first saw the term Double-E. I've only described one of my coils as Dual Class E, or close to it, and it was more a random discovery than an intentional tuning. This was probably the 'dirty double hump' coil where the only reason I even got so curious was because I was wondering how the heck that thing was running the way it was without getting the mosfets hot. A video I saw of a nice little setup had a circuit that illustrated a choke and the series primary capacitor resonating. I think sometimes I would just use a primary capacitor to help adjust my feedback. A couple setups I tried dual tuning it just like I would a basic drsstc using secondary feedback. For me it was never really about Class E but just getting a higher pk to pk voltage on the primary for low voltage DC input setups that I realized could give nice sword spark outputs. At least, it would sort of appear that way given the spark length per input voltage and particular tweaking of the breakout point. I later realized I could land on a tuning that would allow me a good deal of adjustment on the primary coupling, where maybe just raising it a little higher could give me little swords, and lowering it would give me higher voltage branched output.

When it comes to the split primary circuit (Tefatronix/Skori) I always seemed to see about consistent results.. When switching to the single primary and 2 chokes I couldn't really say I ever saw a consistency. There just seemed to be too many ways to tune the thing. I've ran one of those at like 12-15V with a mason jar coil and single turn primary winding so loosely coupled that I could probably wrap it around my waist. I must have made and torn down about 25-30 of those things before finally settling on less than 10 I have left. When using gate driver chips instead of the feedback inductors I felt like I was kind of just unnecessarily complicating the circuit, but I don't think I tried any dual tuning then. The last one of these I made I thought worked out well and I meant to really get into scoping it and trying to figure out what variables were really coming into play relative to other similar builds I've made.. but then I kind of just shelved it IDK maybe just reaching a point where I thought "ok whatever good enough." I can easily get 6 or more inches of branchy arcs to my hand from it.. but then a similar circuit I could get longer arcs to the hand from and the output is all swords. Both are probably identical outside of the mosfets, pri/sec coils, and probably the drain-source caps or something like that. This is basically coming down to more of a real-world tuning to get the desired outcome as opposed to going straight from a simulation to success. I'm curious to know where your progress is at this point. MSLabs had maybe showed off his QCW setup since this post using a very nice little PCB he designed but I've never actually seen the circuit.

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Recommending a PLL setup also. I have found it to just be a really handy setup.
You have a VCO that is always running, if allowed, to make feedback easier to accomplish and running fixed frequency is also kind of nice with the chip because you can use trimmers to adjust a window of variation in your frequency range. I found that tuning for audio is almost as easy as just setting a range on this window of tuning where a compromise is found between volume and switching. You want the frequency to shift around enough to give you nice volume in the plasma but you don't want it shifting so much that it causes bad switching too much of the time. For me the smaller I tune this window the less I allow the VCO to shift relative to the audio signal which has been from a little battery powered bluetooth module+phone.

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Solid State Tesla Coils (SSTC) / Re: GDT doesn't output signal
« on: September 02, 2022, 12:32:50 AM »
You will probably read little to no voltage feeding the interrupter pins with this signal especially at such a low frequency.
You need to put the signal into the feedback pins and just have the interrupter pins tied high if needed. Use a higher frequency so the GDT doesn't just get ringing pulses. Do something in the hundreds of khz or something. Assuming a 50% duty cycle you can use the DMM to measure the gate driver output voltages and expect a DC reading of half the pk voltage at the time.

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Solid State Tesla Coils (SSTC) / Re: 120VAC Mains Ramped Builds
« on: February 25, 2022, 05:59:11 AM »
Yea the plastic roll is a solid idea I might have to try that. I've been using something I had a roll of someone gave me a while ago and it's some kind of rubbery trim but it's pretty thick so I don't have a lot of variation in the spacing. I also just ran out of it. I bet that shelf liner stuff might also be good for insulating diy foil caps.
And I agree that these tubes even the acrylic or pvc pipes are just too expensive and I can't just go to the hardware store and get any specific size of some cheap stuff I want so trusty brand of plastic roll I can cut down and form to size sounds real practical. It's funny how hard it seems to beat the streaking sometimes because apparently there is all this expensive stuff you can buy that is supposed to resist extremely high voltages but it's like it only really does it if you're super liberal with it, almost to the point where a cheap substitute is going to noticeably get the job done about the same. I remember I spent the money on some super high voltage insulating tape and went nuts wrapping a secondary with it thinking it would be some super layer of protection, but I saw no difference between it and just using electrical tape.

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Solid State Tesla Coils (SSTC) / Re: 120VAC Mains Ramped Builds
« on: February 23, 2022, 10:59:04 PM »
I've already wound a coil closer to 700khz for testing but planned on just winding a near identical coil to my first one. It's going to be about 3in x 3.5in using 36 AWG but I've been sort of slacking thinking about finding a perfect pairing of PVC pipes for insulation. For me 36 is about the smallest I can deal with winding and it seems to hold up well enough at high power. There's no way I could wind 45 so that's feat to say the least. The fact that you did it using a drill is actually really impressive lol. I go smaller than 40 I snap the wire every time and I have to do it by hand. I've got maybe one or two tiny coils using it but that baby hair thin wire can indeed throw some nice arcs.
I want to eventually do it the other way around and try coils with higher Q factor since swapping a 36 awg coil with a 32 awg coil of nearly the same dimensions got similar output. Maybe something like 32awg but with less than 400 turns. Over a foot with 45 and it being over 7x longer than the secondary is really close to expected QCW operation though so that's pretty awesome. If it can be condensed down that tiny it seems the best way to go. I think I'd have to search for prewound coils to buy for that though. With that small of a coil, no transformer, and some neat boards it seems like the whole thing could end up looking super tiny.

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Solid State Tesla Coils (SSTC) / Re: 120VAC Mains Ramped Builds
« on: February 22, 2022, 02:30:14 AM »
I had assumed that initial little spike was the capacitors discharging though I'm not sure on that. Maybe the caps are cycling a small feedback loop started by the rising edge of the interrupter and the cap discharges and kills the loop before the actual line voltage starts to rise enough to get it going again. I suppose a doubler could work but I don't think the ramp will be preserved well enough and the sparks would get branchy. I've gotten some decent little ramped swords off straight DC setups though so it's hard to say. Playing around earlier I was able to adjust a phase angle to where I got some nice branchy arcs that seemed more SSTC-like or even small DRSSTC-like with high on times and just tuning the knob again brought the swords back. I'm using 36awg again and the coil runs about 400khz yea. I need a nice little toroid but a properly sized one did make a difference. In my first half bridge setup I had a bootleg cylinder topload and by tuning the primary a little and adding a nice toroid which was a little smaller instead that was what improved the output to 16 inches. I have that same bootleg cylinder topload on my fullbridge so I need to replace it with a toroid like the other one.

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Solid State Tesla Coils (SSTC) / Re: 120VAC Mains Ramped Builds
« on: February 21, 2022, 02:58:43 PM »
Hey Zak I just happened to be free this morning browsing around and saw your post. Those are some nice boards you have there and probably the best way to do it with the dual gate driver and your ZCD circuit. I've had one of my setups sitting on a 'test table' for a while and haven't ran it but was planning on getting back into it now that I'm back in town with some free time. I remember getting the full bridge to spit 18 in arcs with a specific tuning but honestly after playing with it again some time later the arcs seemed to decrease in length again. I'm not sure if this was the result of just me messing with the potentiometers or what. At the time I tried to remember the way I tuned the phase angle by how hard it was switching at the lower voltages. That's what I meant by it was hard switching in the beginning, normally with how I see them running they will pull some decent amps at the lower voltage and I can feel some hard knocking in the variac, but when reaching full line voltage that knocking goes away and that current draw sort of 'levels out'. That is to say it just seems like the phase shift going on is causing it to lose some throughput. I noticed that by tuning it so at the lower voltages that hard 'knocking' was softened out a bit I had basically detuned the coil to have it get closer in tune at the higher voltages. I noticed that initial spike in the waveform would shrink slightly, and just about the point where I would feel the knocking go away was a sweet spot and any further detuning would start making the waveform funky. But yea I'm just looking at the voltage waveform to free air with my hanging probe. I've measured the DC blocking cap before but found free air voltage to be a good enough indicator.

So when I run no PLL and use the HC14 by itself I usually see this kind of operation where it seems to be switching fairly hard at low voltage. I crank the variac knob to 120VAC and all that goes away, but at the same time I feel like I've shifted the phase relation a bit at max voltage. So recently when tuning the PLL I tried to adjust it to account for this by making it so it has the best output at the max voltage and a fairly weak output at the lower voltages.

It's a little similar to tuning a DRSSTC for streamer length to some degree I think. I move my hand closer to the coil I see the output increase so it seems more accommodating to long streamers. Or it could be tuned the other way around where it has the best apparent output until I bring my hand close. I've found I needed to finely tune this in order to run a CW setup max voltage like that from the wall to keep it from pushing over 10-15A.

I still have some more coils to finish winding for the all ramped setups but I got the impression about 16 inches or so was going to be the consistent max I could reach at 120 but this has been the case for both the half and full bridges. Getting the full bridge to hit 18 again just seems like a pain. I was supposed to drive that with 240 so I still need to see how that goes.. was going to try some 60VAC transformer I had in reverse just for kicks. If something like that works for longer streamers I think it would be pretty awesome to still have everything in one 120VAC plug.

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Solid State Tesla Coils (SSTC) / Re: 120VAC Mains Ramped Builds
« on: January 22, 2022, 11:20:55 AM »
I've been grabbing Jamesco transformers since it seems difficult to source cheaper alternatives but on most all my coils I use a 15v gate drive in which case even with the full bridge I've seen only minimal current draw. I like to use a DC supply for testing and in most cases feeding a 15v 1.5A regulator with 20VDC or so I'm looking at around 100-200mA tops being pulled. This all depends on what kind of operation I'm running and if trying to run a full bridge CW I might want to beef up the gate drive. I've never done it because the two UCC drivers seem to chug along fine so far.

As for say unsmoothed half wave CW I just see the arcs as being the full ramping of the half wave upward and downward slopes with no breaks in between aside from the natural line frequency. Since staccato would just be trying to initiate a ramp at a lower break rate than 60hz I just picture it as being able to spit cleaner and possibly longer arcs. So that is to say 99% of the time I can look at the max output unsmoothed CW and see where the peaks reach out to, and assume I'll see those same peaks or maybe longer running staccato. In that regard it seems odd imagining a 4 inch coil spitting something like 12+ streamers in unsmoothed CW mode assuming it could handle it.

When it comes to 460's I wouldn't say I've had bad performance with them but I'd just prefer something more modern when possible. For example in the PLL circuit I recently got running better the 460's in there are working well and do not run warm or anything. I can't say however if they are part of the reason why I couldn't get great ramped performance from the coil they are running. The body diodes are slow to recover I believe and when you start running high power the dissipation is up there, but they do indeed get the job done as many coilers have shown. I see the 60N65's as better modern replacements when I plan on having a 500v+ ceiling and they are about the same price.

I can't say there is really an optimal frequency range for the ramps but it seems that you can notice the arcs start to become crooked and branchy once you start getting below about 300-350khz. At least 400khz or so is recommended for the straightest ones. I thought they were pleasing enough at around 230khz and still like to shoot straight upward but do indeed lose that true sword shape.

I agree that slight adjustments in the primary is a huge factor and something I seem to play a lot with on most coils. I probably wind about 10-20 different test primaries for a build after realizing such slight changes can make big differences. A single turn made a huge difference on my half bridge. So far the only commonality I seem to see is that a sweet spot is usually right on the edge of racing streaks. Often times I've brought it to that edge then just added more insulation to get rid of the streaks.
This is not something that would seem ideal if tuning for 120VAC then deciding to up to 240 as it will likely arc over.

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Solid State Tesla Coils (SSTC) / Re: 120VAC Mains Ramped Builds
« on: January 21, 2022, 07:36:07 PM »
No transformer would def make everything even handier. Even with it I think it's pretty nifty since one may use a transformer for powering the logic anyway so they can just reuse that one for the staccato. Overall this kind of setup does seem like a win win even for a first build but so far I haven't been able to really figure out what is most crucial to getting the longest discharges here. All I can really do is try to document exactly how I've built them and compare results with other variations.
For example I've taken some old half bridges I built and tried running them the same way with the same coils with poor results. They are old circuits I had thrown together without much care but seemed to work about average with the coils I wound for them. Similarly I tried the same coils out on an old PLL half bridge board I made which also seems to run ok on antenna feedback. Just another basic half bridge but poor results in comparison where everything runs clean but spits short arcs. On average I'd say with a half bridge build I might try staccato on, the sparks I'm looking at are going to be in the 6-8 inch region, maybe 12 inches or so if the coil is large enough.

I've gotten more comfortable with the PLL feedback though. Originally I was kind of iffy about messing with the knobs while the coil was running not wanting to blow the bridge but it seems unbothered when dialed in good enough. Seems maybe the best/easiest way to try shaping the discharges a little bit is to just run it at the max voltage then play with the phase angle. What I've noticed in some builds is there is a phase angle which detunes slightly and begins to try branching the arcs a little more the further shifted it becomes in that direction, however if only slightly adjusted the swords will retain their shape while becoming slightly longer. The VCO running also seems to just be a reliable way to ensure operation at any given time for switching into various modes.
I'd say my ideal setup would be trying to replicate the longish arcs somewhere around the 12 inch mark at 120VAC, but have it switchable between full wave/half wave/smoothed/mains synced. This would hopefully be easy enough to run reliably in all modes without a really beefy design.

What's interesting to me is when I look at the unsmoothed CW output and see those longest streamers breaking out past the "bush" I assume I'm looking at those 170VDC peaks. So if ran staccato I assume those peaks is only what I'll see. I remember on a different full bridge build the full wave rectified mains was looking pretty thick. It was about 6 inches of 'bush' with the peak streamers reaching to about a foot. This was a fairly powerful and large setup in comparison though so it was not surprising to see. I assume staccato operation of the same would result in something like the 12 inch streamers.

So when looking at a coil that is only around 4 inches tall or shorter, it's a little confusing to see output that reaches the same length or longer. It gives me the impression then that if you have 12in+ staccato arcs then from full or half wave rectified mains it should look like a big bush with streamers reaching out to 12 inches. My recent ramped setups will be overdriven in CW, but work well interrupted. Some older builds seem to work well in CW, but not so well interrupted compared to the recent ones.

At this point it doesn't seem like the PLL feedback is necessary since both of us got away without it in a build. You used mosfets and I used IGBT's so there's nothing special there. Your build likely has slight variations to mine and still seems to work about the same.. so what really are the most important factors to keep in mind?
I wish I could better try to rationalize what it would be so next time I build one I'm not just trying to copy what I did before exactly while hoping for the best.

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Solid State Tesla Coils (SSTC) / 120VAC Mains Ramped Builds
« on: January 21, 2022, 03:00:04 AM »
Got a lot of useful information reading this website so for what it's worth here are some pics and a little info about a ramped build I thought worked out pretty good. ZakW posted a lot more info about a similar build which has gotten great results. I'll probably try to rebuild mine and jack it all up so here is the breakdown.

I saw good results from the Loneoceans RSSTC and one shown on SciTubeHD's youtube channel so I basically tried to wind some coils with similar dimensions and resonant frequency. I also tried some other staccato interrupters already out there but Gao's seemed to work the best for me. I've found it difficult to exceed 12 inch arcs on an SSTC without upping the coil size so the budget QCW mains ramped approach seems like a really good setup and who doesn't like sword sparks.

They are based on Steve Ward's SSTC 5 driver (https://www.stevehv.4hv.org/SSTC5/miniSSTCfnlsch.JPG) with a "staccato interrupter" in place of Steve's 555. I'm running FGA60N65SMD IGBT's on it and still using a 1:1 GDT but using a 15v regulator to power the gate drivers and this just makes things simpler.
Other changes are things like the DC blocking capacitor value at the driver outputs (which should probably be experimental, I think I have like a 2uF ceramic) and the addition of a 1uF DC blocking capacitor in series with the primary (a few .33uF 1200V MKP caps I had).
I had a fairly large T37 core so I used that to wind a single GDT for driving both halves of the bridge. It allowed me to fairly easily wind 5 twisted wires. I have a CT for the feedback with about 30 turns. To add PLL feedback I put a 5v driven CD4046 in between the hex inverter and the gate drivers.

Below are the two builds I've tried with the half bridge on the left and full bridge on the right. They are both using very similar coil dimensions of 36 AWG on 9cm tall by 8cm wide formers (and run about 400khz). A 32 AWG coil of slightly larger dimensions seemed to work well also. The one on the left has the staccato and logic transformer inside the box and the one on the right currently uses an external logic supply and gets the mains sync from a transformer inside my interrupter box. I plan to get a nice toroid for the full bridge and hopefully hit that 20 inches. They are both more or less identical builds but with one using the full bridge and PLL feedback.


This is is a big universal interrupter box I went ham with trying to put everything I could into it over time. The interrupter circuit is isolated from the RCA plug with an optocoupler and 9v battery which I found almost necessary without 'getting lucky' dodging interference. I did the mains sync like that because I figured I'd want to be able to run any other builds I make mains synced without having to make a new circuit each time. I'm using Gao Guangyan's circuit seen here https://www.loneoceans.com/labs/sstc3/schema_sstc3_staccato.jpg but with C4 modified for the full 60hz half wave (quieter thicker arcs due to adding and shutting off after the downward slope).


Bridge and driver board. I believe there is about 2uF worth of film caps across the bridge and I stacked what I had at the time.
There are 15v, 12v, and 5v regulators, the 12v just being for the fan. There is a janky heatsink I used which was just a couple alu plates from somewhere I put together so it has this fan on a 40C N.O. switch. At ~8ms and highest BPS it appears to pull around 5A from the wall with the current tuning. I noticed the arcs were decent enough without the PLL though.


Using the two UCC2732x gate drivers which seem to run the full bridge ok in this operation but it's possible at ~8ms on times at highest BPS they will start overheating eventually. If I run it hard for a while to the point I can feel the heatsink getting more than just warm (with fan blowing) then the output seems to drop a little probably indicating the drivers and switches don't like it. Nothing gets too warm at the lower break rates it typically runs so it all kind of works out. I get them from mouser and Ebay/Amazon or something like that will always give you fake ones so don't do it.


A pretty basic layout that hasn't punished me for it but hey I'm not recommending a slack build or anything. This is the 2nd time I made a full bridge "test layout" like that I ended up just keeping in a final build, the other being a DRSSTC which uses the same kind of bridge layout, but to be fair might be getting saved by the snubber. I usually test with an isolated DC supply first, then low voltage AC, then full mains. So far with various coil testing these IGBT's have held up so they are pretty trusty.


A few shots of some ~18 inch arcs. I have a piece of foil above set to 20 inches from the breakout point which I could not get it to strike no matter how clever my insults were. When I had it set to 18 inches it would strike it every now and then but who knows what slight variations could result given environmental changes etc. I was originally struggling to get it to hit 16 inches before just messing with the primary a little bit and randomly testing various phase angle adjustments.




Here's a 16 inch strike from the half bridge catching mainly the tail end of the arc. I was pretty liberal with the size of the boards so in reality the spark to coil ratio could look much better after condensing the box down and everything looks smaller. I tuned that half bridge, got it to strike 16in, then was too excited about it to mess with it any further lol.


When it comes to the longest arcs from such a build it seems like it becomes a battle of finding a running frequency which is not too high or low, as well as trying to get it to form arc channels which don't branch on their way out as actual swords. That is to say I've seen tuning which seemed better in phase and probably had more power in the arcs but due to a tendency to branch more, a different tuning which pulled less power might yield longer discharges. I've kept fairly high coupling with these something around normal SSTC range and tried to keep the primary just out of streaking. There seems to be a certain science to 'encouraging' discharges to form just right as that voltage in the secondary starts to skyrocket. Slight changes in the breakout point length can for example make a big difference. A stuttering output with popping and clicking may indicate this energy trying to go somewhere and ending up in primary discharges you might not see in the light, where it may otherwise find its way out a longer breakout point, or one which is oriented to the side for example. I think using mosfets and an even smaller coil maybe closer to 600khz could get either the same arcs or longer. That's about all the insight I can personally offer into it so if you made it this far reading thank you for your sacrifice.

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Solid State Tesla Coils (SSTC) / Re: SSTC with push-pull configuration
« on: January 14, 2022, 08:47:43 PM »
Your mileage will most certainly vary but I tried the push pull setup using the gate drivers a while back using a GDT. The GDT isn't necessary unless you get too high in input voltage but I recall about the same performance as going direct feedback at the time. I remember thinking I had took a bunch of effort to make the thing run off logic feedback and I didn't have entirely ideal components but I tried to observe the difference using what I had when driven with the direct feedback and the gate drivers and hex inverter combo. It had its advantages for example running really low bus voltages like 5v or less if desired but it didn't seem worth all the extra components. Maybe I could have designed it a little better. I ultimately just substituted some knockoff IRFP250N's in the circuit and used the dual-choke setup to feed a single primary with a series capacitor across it. Trying to tune the switching a little with some drain caps and getting the series primary cap value just right (or primary and coupling) and it seems to run pretty well up to a tested 60VDC for me. This of course still requires a separate interrupter and gate voltage which I use a little battery pack for.
Alternatively I've tested the basic circuit as-is with higher voltage fets like 460s up to about 100VDC input before it seemed to start struggling (RC snubbers will FLAME)

That circuit to me has only truly been handy for the low voltage arrangements. I think it's perfect actually. If tuned right you can run it quite efficiently getting any range of output with 55V fets. Every time I tried to rework it into something that ran 120VAC it was a disaster.

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Solid State Tesla Coils (SSTC) / Re: Mains Ramped SSTC - Power Supply Issue
« on: December 24, 2021, 05:00:27 AM »
Awesome!!  Ever since I saw the PLL ramped setup on SciTubeHD's channel I knew I had to make one and it's a really cool SSTC to have. I still haven't figured out what causes all the kinks but a foot or so of arcs from 120VAC is a great deal to me. I'm still not sure why I got longer arcs from the half bridge instead of the full bridge though. I noticed depending on where I actually plug in my half bridge setup it will run differently.. something about the environment and the way the cord is sitting I guess. Using the PLL feedback addition everything seems more robust.

It doesn't surprise me there is an issue with a random step-down because a lot of my first tries at the circuit using different coils seemed to not work properly at certain voltage ranges using the variac. The addition of the CD4046 seemed to help this though.

Just for the sake of trying maybe you could play around with the breakout point using the step-down to see if maybe you can persuade the arcs to form a little quicker than when the breakout point is fairly short and pointing straight out the top. Maybe try a longer point hanging out to the side or something.

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Solid State Tesla Coils (SSTC) / Re: Chinese SSTC PeleusTech Question
« on: October 28, 2021, 02:50:02 AM »
Most of those builds seem to be designed around '220V' which makes sense being the residential line voltage in China.
You can tell if it's dual resonant or voltage doubled by identifying the capacitors. If there are caps or a cap in series with the primary and the value is well below 1uF or so then it's dual resonant. If there is a current transformer also on the primary wire this is another giveaway. If there are fairly large electrolytic caps in series on the bus it might be doubled but you'd have to confirm by seeing how the diodes are connected.

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I agree about using both IC's. Teslista555 and others have seemed to benefit from adding the schmitt trigger stage. This was going to be how I went about another PLL if I got around to it.

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My setup never locked onto bad frequencies but this is what I hear can happen as the IC looks to track the various dirty edges. It essentially confuses the chip as it tries to lock onto something it wont. Theoretically I suppose you don't need a dual resonant primary to use primary feedback but if you had some method of doing it by amplifying the feedback signal enough as well as filtering the really high frequencies the primary may want to ring at it CAN work. (right?) Assuming you had this ironed out I would imagine only phase shift issues could become evident if this shift became too much during loading.
I'm not really sure how you're going about this but I'd think secondary feedback would in fact do you a little better. Pulling arcs to ground has never seemed an issue to me with a good SSTC, more so a problem with a DRSSTC without any kind of OCD.

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I'd heard from others that the PLL can be real finnicky but I was surprised when playing with some cheap CD4046's I got from ebay. I could pretty much do anything with the antenna, it was unremarkable the location or orientation etc. It's just a short piece of wire poking out randomly now. I had a long antenna fall over and touch the secondary a little then just lay flat and still, I saw no change in output at the time. I'd never pulled arcs directly to ground with it but that's what I heard was problematic, not so much that it should inherently have trouble getting a lock back but that it could cause the chip to try locking onto all types of dirty edges way outside of the f range so yes the secondary feedback seems to be problematic there. I suppose you could do the phase shifting externally but I sort of just find the CD4046 kind of handy if I just want to run 12v logic using just that IC and a couple gate drivers for example. If you just want reliable feedback, using a CT on the secondary seems reliable enough. How you are implementing primary feedback currently may be your problem though. I would think unless you've actually got the primary running as an LC tank at a frequency close to your secondary resonance then there could be all kinds of phase shift issues. Gate drivers with enables like the UCC seem to reliably allow me to run secondary feedback and interrupt without a startup oscillator because of the enable pulse on the driver outputs. Likewise when running CW I can switch the enable high and the pulse will start the feedback loop so long as there is voltage on the bus to do it. As for your dropouts it's hard to say as I guess it depends on the PSU but I can say I've never really seen issues with running secondary feedback, a decent CT, and something like a 74HC14.

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There are varying levels of intuitive design when it comes to PLL circuits but the ones on the simpler side just require you set that frequency range and hope you can find the secondary resonance within it. I believe fine tuning how small a window this range is will allow you to fine tune the phasing better. If you've ever looked at PLL SSTC's and thought "wow that's nice fat output" it's probably because of the tuned phase angle which is allowing maximum power throughput. When I played with the basic PLL circuit (Scopeboy's) I found it very easy to use an antenna and just change the timing capacitor to give me something around maybe 150-200khz window with my secondary resonance fairly close to the middle.   

The VCO on the PLL will output a 50% square wave at all times with a frequency depending on the timing components. Tuning that in til it finds a lock by getting resonant feedback will then allow you to use the same potentiometer for frequency tuning to then adjust the phase angle. If for whatever reason it drops out of lock it may find it again but not necessarily during the time you're loading it causing it to drop out. I think for me I had to play with the values a little til noticing I was able to load the coil various ways while maintaining lock and was then able to crank full voltage. Before that tuning I could bring my hand close or something and it would drop out. Steve Conner and Steve Ward I think have both designed more intuitive PLL circuits that are robust enough to handle ground strikes and various loading without difficulty but those seemed pretty complicated to me.

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Solid State Tesla Coils (SSTC) / Re: SSTC - blowing up transistors problem
« on: September 07, 2021, 06:34:32 PM »
If you got that working well it would sort of defy any reason for people to be concerned over layout. At the very least I'd try to shorten the capacitor connections to each other with thick soldered leads instead of running a bunch of wires out to levernuts. Then you could at least just move them and the rectifier over closer to the bridge with much shorter and fewer jumpers.

19
555 would work fine. I'm careful with my potentiometer when using the TL494 and not limiting the max duty cycle, but have found some arrangements can handle temporary CW at lower voltages such as 5v-12v without needing an insane sized heatsink and active cooling. I have one I run in CW from a 30V 5A supply which in reality pushes about 33V at 6A or so. I keep the fets on a large heatsink and it can run indefinitely. As for the interrupter you may want to invert the signal with a small transistor so an LED indicator makes sense since the interrupter mosfet needs to be on all the time to force the push-pull fets low. I just wire my pot 'backwards'.
It's often easy enough to trial and error a couple primaries as far as coupling distance and then play with the height it sits along the secondary. A regular single conductor can be used for the primary. There seems to be certain phase-shift it tends to run at for longest arcs depending on the GDT used and for me they usually don't seem to reach out well til about 24V and higher. I made a couple using IRFP260's that would pull some nice hot arcs at only 12v or so and pulled about 10A in the process. Another thing to remember is to have the voltage divider on the mosfet gates set properly. You want to start at no voltage across them and slowly increase it looking for oscillation. Shielding can also be tricky with these so try not to create long leads and keep everything tight and short as possible. I've often tried to run wires to pots and the interference became a problem in the interrupter. 

20
Solid State Tesla Coils (SSTC) / Re: Mains synced sstc questions
« on: April 18, 2021, 02:36:34 AM »
/>
SciTubeHD's ramped PLL SSTC. He has his staccato output going to the enable pins. Beautifully simplistic overall circuit and results.

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