Medium size DRSSTC - Primary Flat or Helical
Killa-X, Fri Jun 08 2012, 03:53AMMy DRSSTC currently features a Helical primary. It's climb height is about 5 inches, and maintains 3 inches from the secondary. As it sits, i never had issues with it flashing over to the secondary. However, I want the best out of this coil, and I see a lot of the large DRSSTCs using flat primary coils instead of helical or cone. Steve wards for example. I just want peoples suggestions on if i should keep mine as is, a Helical coil, or change it into a flat coil. Changing isnt a problem. I just have to cut out 8 new peices of acrylic that attach to my clamps that extend outward.
Let me know what you guys think.
I have had tuning issues in the past.
PrimaryThanks for your time. My last setup, a CM300 halfbridge, peaked at 7ft sparks for the power I gave it. This round, its CM300 fullbridge. I'll do proper tuning, but I want to make sure my primary is best suited for operation. Also ... I will get a better clamp for primary tap :D
Re: Medium size DRSSTC - Primary Flat or Helical
Goodchild, Fri Jun 08 2012, 06:07AM
Flat hands down for any DR. There is really no reason to do a helical primary in my opinion. With a flat primary you get a coupling in and around 0.2k which is more than plenty for most DRs and it is out of the way much less likely to be hit by racing sparks and toroid to primary flash overs. And on top of all of this flat is also way easier to build.
I used a helical on a DR once, my first DR, never again....
The only time I have really needed a helical primary is with my QCW where a coupling of 0.3k and greater was needed for proper operation and the top voltage was low enough that flash overs were not a problem, <70Kv in my case.
EDIT:
Also looking at your photo tuning was not the only problem, your coupling had to be insanely high with the secondary all the way down in the helical primary.
Goodchild, Fri Jun 08 2012, 06:07AM
Flat hands down for any DR. There is really no reason to do a helical primary in my opinion. With a flat primary you get a coupling in and around 0.2k which is more than plenty for most DRs and it is out of the way much less likely to be hit by racing sparks and toroid to primary flash overs. And on top of all of this flat is also way easier to build.
I used a helical on a DR once, my first DR, never again....
The only time I have really needed a helical primary is with my QCW where a coupling of 0.3k and greater was needed for proper operation and the top voltage was low enough that flash overs were not a problem, <70Kv in my case.
EDIT:
Also looking at your photo tuning was not the only problem, your coupling had to be insanely high with the secondary all the way down in the helical primary.
Re: Medium size DRSSTC - Primary Flat or Helical
Steve Conner, Fri Jun 08 2012, 07:45AM
To my understanding, the tighter the coupling the better your coil will perform, until you reach the point that it starts flashing over because the gap between primary and secondary is too small. The flat primary doesn't have the optimum coupling coefficient, it just has about the highest coupling possible without flashovers in a high-powered coil. I think DRSSTCs would perform even better if this limitation could be overcome, perhaps by filling the coil system with oil or SF6.
I had this problem once, and rather than rebuild the primary, I rewound the bottom 2" of the secondary (which had been burnt up by the flashovers anyway) with a heavier gauge of wire.
Steve Conner, Fri Jun 08 2012, 07:45AM
To my understanding, the tighter the coupling the better your coil will perform, until you reach the point that it starts flashing over because the gap between primary and secondary is too small. The flat primary doesn't have the optimum coupling coefficient, it just has about the highest coupling possible without flashovers in a high-powered coil. I think DRSSTCs would perform even better if this limitation could be overcome, perhaps by filling the coil system with oil or SF6.
I had this problem once, and rather than rebuild the primary, I rewound the bottom 2" of the secondary (which had been burnt up by the flashovers anyway) with a heavier gauge of wire.
Re: Medium size DRSSTC - Primary Flat or Helical
Uspring, Fri Jun 08 2012, 10:46AM
What about using a conical primary? Seems like a compromise between flat and helical ones. JavaTC will do the math, e.g. coupling for you.
Uspring, Fri Jun 08 2012, 10:46AM
What about using a conical primary? Seems like a compromise between flat and helical ones. JavaTC will do the math, e.g. coupling for you.
Re: Medium size DRSSTC - Primary Flat or Helical
Dr. Drone, Fri Jun 08 2012, 02:31PM
Dr. Drone, Fri Jun 08 2012, 02:31PM
Re: Medium size DRSSTC - Primary Flat or Helical
Goodchild, Fri Jun 08 2012, 02:48PM
Well there is a way to overcome this limitation turn that DR into a QCWDR and get those top volts way down.
In that case I'm all for high coupling and helical primaries!
Also Dr. Spark I almost smashed my screen thinking there was a bug on
Goodchild, Fri Jun 08 2012, 02:48PM
Steve Conner wrote ...
To my understanding, the tighter the coupling the better your coil will perform, until you reach the point that it starts flashing over because the gap between primary and secondary is too small. The flat primary doesn't have the optimum coupling coefficient, it just has about the highest coupling possible without flashovers in a high-powered coil. I think DRSSTCs would perform even better if this limitation could be overcome, perhaps by filling the coil system with oil or SF6.
I had this problem once, and rather than rebuild the primary, I rewound the bottom 2" of the secondary (which had been burnt up by the flashovers anyway) with a heavier gauge of wire.
To my understanding, the tighter the coupling the better your coil will perform, until you reach the point that it starts flashing over because the gap between primary and secondary is too small. The flat primary doesn't have the optimum coupling coefficient, it just has about the highest coupling possible without flashovers in a high-powered coil. I think DRSSTCs would perform even better if this limitation could be overcome, perhaps by filling the coil system with oil or SF6.
I had this problem once, and rather than rebuild the primary, I rewound the bottom 2" of the secondary (which had been burnt up by the flashovers anyway) with a heavier gauge of wire.
Well there is a way to overcome this limitation turn that DR into a QCWDR and get those top volts way down.
In that case I'm all for high coupling and helical primaries!
Also Dr. Spark I almost smashed my screen thinking there was a bug on
Re: Medium size DRSSTC - Primary Flat or Helical
brandon3055, Fri Jun 08 2012, 03:11PM
Well there is a way to overcome this limitation turn that DR into a QCWDR and get those top volts way down.
[/quote1339168145]
What is a QCWDR?
brandon3055, Fri Jun 08 2012, 03:11PM
Well there is a way to overcome this limitation turn that DR into a QCWDR and get those top volts way down.
[/quote1339168145]
What is a QCWDR?
Re: Medium size DRSSTC - Primary Flat or Helical
Dr. Drone, Fri Jun 08 2012, 04:56PM
Dr. Drone, Fri Jun 08 2012, 04:56PM
Re: Medium size DRSSTC - Primary Flat or Helical
Goodchild, Fri Jun 08 2012, 08:13PM
A QCW is a DR the full name of the coil is a QCWDRSSTC. A QCW is DRSSTC with a high tank impedance and control over the current envelope. Same basic principles as a DR apply.
Goodchild, Fri Jun 08 2012, 08:13PM
Destroyer of mosfets wrote ...
Well there is a way to overcome this limitation turn that DR into a QCWDR and get those top volts way down.
[/quote1339168145]
What is a QCWDR?
Well there is a way to overcome this limitation turn that DR into a QCWDR and get those top volts way down.
[/quote1339168145]
What is a QCWDR?
A QCW is a DR the full name of the coil is a QCWDRSSTC. A QCW is DRSSTC with a high tank impedance and control over the current envelope. Same basic principles as a DR apply.
Re: Medium size DRSSTC - Primary Flat or Helical
Killa-X, Sat Jun 09 2012, 12:46AM
Well, Is it suggested that I rise my DRSSTC secondary so its not so far deep into my helical, or is it best I just rebuild the primary flat, and adjust coupling from there. I can do either. Obviously it be easier to keep the current design, and just rise the secondary, but, If flat primaries seem to run performance better, then I maybe should just build things that way..?
Killa-X, Sat Jun 09 2012, 12:46AM
Well, Is it suggested that I rise my DRSSTC secondary so its not so far deep into my helical, or is it best I just rebuild the primary flat, and adjust coupling from there. I can do either. Obviously it be easier to keep the current design, and just rise the secondary, but, If flat primaries seem to run performance better, then I maybe should just build things that way..?
Re: Medium size DRSSTC - Primary Flat or Helical
Steve Conner, Sat Jun 09 2012, 06:47AM
I don't think it would make a huge difference. Coupling is coupling. The flat primary is maybe slightly better, but I'm not sure if the improvement is worth the hassle of rebuilding it, compared to just raising the secondary.
The last coil I made had a 45 degree conical primary, which is kind of a compromise.
Also, NACOLIAKNSSTC (Nowadays Any Combination Of Letters Is A Kewl New SSTC)
Steve Conner, Sat Jun 09 2012, 06:47AM
I don't think it would make a huge difference. Coupling is coupling. The flat primary is maybe slightly better, but I'm not sure if the improvement is worth the hassle of rebuilding it, compared to just raising the secondary.
The last coil I made had a 45 degree conical primary, which is kind of a compromise.
Also, NACOLIAKNSSTC (Nowadays Any Combination Of Letters Is A Kewl New SSTC)
Re: Medium size DRSSTC - Primary Flat or Helical
Killa-X, Sat Jun 09 2012, 11:53PM
Sounds good, raising will def. be better than lowering. Right now the first turn on my primary matches the first turn on my secondary, roughly 1" off the ground. I have 8 turns to find my resonance, so, reality it climbs about 5 inches up my secondary. 24awg wire, so you can do the math to estimate how many turns.
Killa-X, Sat Jun 09 2012, 11:53PM
Sounds good, raising will def. be better than lowering. Right now the first turn on my primary matches the first turn on my secondary, roughly 1" off the ground. I have 8 turns to find my resonance, so, reality it climbs about 5 inches up my secondary. 24awg wire, so you can do the math to estimate how many turns.
Re: Medium size DRSSTC - Primary Flat or Helical
brandon3055, Sun Jun 10 2012, 01:38AM
When people refur to the tank cap in an DR do they mean the large input filter cap (as I have always thought) or do they mean the cap in seirise with the primary
brandon3055, Sun Jun 10 2012, 01:38AM
When people refur to the tank cap in an DR do they mean the large input filter cap (as I have always thought) or do they mean the cap in seirise with the primary
Re: Medium size DRSSTC - Primary Flat or Helical
Sigurthr, Sun Jun 10 2012, 12:41PM
They mean the cap in series with the primary as this forms the "tank" circuit. It does cause confusion for non native english speakers or people new to electronics from time to time. Filter caps are also called "energy storage" caps. What does a tank of fuel do? Store liquid energy, so don't feel bad about the confusion.
Sigurthr, Sun Jun 10 2012, 12:41PM
They mean the cap in series with the primary as this forms the "tank" circuit. It does cause confusion for non native english speakers or people new to electronics from time to time. Filter caps are also called "energy storage" caps. What does a tank of fuel do? Store liquid energy, so don't feel bad about the confusion.
Re: Medium size DRSSTC - Primary Flat or Helical
brandon3055, Sun Jun 10 2012, 01:18PM
Aah now it all makes sense the reason I was confused is because most Sstc's also have a series cap on the primary but don't often have a large fillter cap so then I guess the difference between an Sstc and a Dr is just that in a Dr the tank circuit is tuned to the same frez as the primary
brandon3055, Sun Jun 10 2012, 01:18PM
Aah now it all makes sense the reason I was confused is because most Sstc's also have a series cap on the primary but don't often have a large fillter cap so then I guess the difference between an Sstc and a Dr is just that in a Dr the tank circuit is tuned to the same frez as the primary
Re: Medium size DRSSTC - Primary Flat or Helical
Sigurthr, Sun Jun 10 2012, 02:57PM
A SSTC doesn't need any capacitor in the primary circuit... you're "hard" driving the pulses going in to the primary at the frequency the secondary is resonant to, a kind of forced systemic resonance (the primary is never in resonance at all).
A DRSSTC is a SSTC where you add capacitance to the Primary so that it forms its own LC circuit which you set the resonance point to be the same (or close to, in reality) as the secondary's self-resonance frequency. The DR in DRSSTC means "dual (or double) Resonant" since there are now two resonant circuits; 1) the primary + tank cap, and 2) the Secondary.
In an ideal theoretical (not real world!) Tesla Coil you would choose components so that one resonant circuit feeds another, which then feeds another. With a simple SGTC this would be descibed as where the first circuit is the input transformer and the primary capacitor, the next would be the tank capacitor and the primary, and then it is coupled to the secondary, which is its own resonant circuit. Everything would be operating at the same frequency. This of course doesn't work in real life as resonant rise would destroy real world components. The DRSSTC is just a "chip off the block" so to speak in that it strives to achieve resonance in every viable subsystem of the device.
Sigurthr, Sun Jun 10 2012, 02:57PM
A SSTC doesn't need any capacitor in the primary circuit... you're "hard" driving the pulses going in to the primary at the frequency the secondary is resonant to, a kind of forced systemic resonance (the primary is never in resonance at all).
A DRSSTC is a SSTC where you add capacitance to the Primary so that it forms its own LC circuit which you set the resonance point to be the same (or close to, in reality) as the secondary's self-resonance frequency. The DR in DRSSTC means "dual (or double) Resonant" since there are now two resonant circuits; 1) the primary + tank cap, and 2) the Secondary.
In an ideal theoretical (not real world!) Tesla Coil you would choose components so that one resonant circuit feeds another, which then feeds another. With a simple SGTC this would be descibed as where the first circuit is the input transformer and the primary capacitor, the next would be the tank capacitor and the primary, and then it is coupled to the secondary, which is its own resonant circuit. Everything would be operating at the same frequency. This of course doesn't work in real life as resonant rise would destroy real world components. The DRSSTC is just a "chip off the block" so to speak in that it strives to achieve resonance in every viable subsystem of the device.
Re: Medium size DRSSTC - Primary Flat or Helical
Killa-X, Sun Jun 10 2012, 08:15PM
Actually, All of my SSTC's (full bridges) feature a 1.36uF in series with the primary...
Killa-X, Sun Jun 10 2012, 08:15PM
Actually, All of my SSTC's (full bridges) feature a 1.36uF in series with the primary...
Re: Medium size DRSSTC - Primary Flat or Helical
Steve Conner, Sun Jun 10 2012, 09:53PM
The story goes that in the first radio transmitters, around the turn of the 20th century, the tuning capacitor consisted of a stack of metal plates immersed in a tank of oil. Hence the name tank capacitor, and tank circuit for the LC resonant circuit.
Later on, Tesla coil builders borrowed the term from radio hams.
Steve Conner, Sun Jun 10 2012, 09:53PM
The story goes that in the first radio transmitters, around the turn of the 20th century, the tuning capacitor consisted of a stack of metal plates immersed in a tank of oil. Hence the name tank capacitor, and tank circuit for the LC resonant circuit.
Later on, Tesla coil builders borrowed the term from radio hams.
Re: Medium size DRSSTC - Primary Flat or Helical
brandon3055, Sun Jun 10 2012, 11:52PM
So do just about every Sstc h bridge circuit I have ever found including mine so I guess most of the Sstc's out there are actually DRSSTC's that gust need a tune up (it think they use it as current limiting)
brandon3055, Sun Jun 10 2012, 11:52PM
Killa-X wrote ...
Actually, All of my SSTC's (full bridges) feature a 1.36uF in series with the primary...
Actually, All of my SSTC's (full bridges) feature a 1.36uF in series with the primary...
So do just about every Sstc h bridge circuit I have ever found including mine so I guess most of the Sstc's out there are actually DRSSTC's that gust need a tune up (it think they use it as current limiting)
Re: Medium size DRSSTC - Primary Flat or Helical
Sigurthr, Mon Jun 11 2012, 01:22AM
I am far from an expert or pioneer who coined the terms but it seems to me that it is not the case that a SSTC cannot have a capacitor in the primary circuit, just that the primary circuit is by definition NOT RESONANT. As soon as the primary circuit enters resonance with the secondary it becomes a DRSSTC.
So it seems it would be more correct to say a SSTC doesn't need a primary circuit capacitor but a DRSSTC does and it must be selected for resonance.
Though if you're going to put a capacitor in the primary circuit why not go all the way and make it a DRSSTC? I suppose you would need to implement a controller/interupter since DRSSTCs cannot run CW mode, but they're not that hard to do, a simple PWM 555 into an enable pin is all it takes. It seems to me that a nonresonant tank capacitor is just going to hurt performance by creating parasitic oscillations at the primary LC's Fres, which depending on the feedback method used could get in to the drive circuitry and compete against the secondary's feedback.
Sigurthr, Mon Jun 11 2012, 01:22AM
I am far from an expert or pioneer who coined the terms but it seems to me that it is not the case that a SSTC cannot have a capacitor in the primary circuit, just that the primary circuit is by definition NOT RESONANT. As soon as the primary circuit enters resonance with the secondary it becomes a DRSSTC.
So it seems it would be more correct to say a SSTC doesn't need a primary circuit capacitor but a DRSSTC does and it must be selected for resonance.
Though if you're going to put a capacitor in the primary circuit why not go all the way and make it a DRSSTC? I suppose you would need to implement a controller/interupter since DRSSTCs cannot run CW mode, but they're not that hard to do, a simple PWM 555 into an enable pin is all it takes. It seems to me that a nonresonant tank capacitor is just going to hurt performance by creating parasitic oscillations at the primary LC's Fres, which depending on the feedback method used could get in to the drive circuitry and compete against the secondary's feedback.
Re: Medium size DRSSTC - Primary Flat or Helical
Killa-X, Mon Jun 11 2012, 01:25AM
Verdict is, I'll try leaving it as a helical and see how things go. I have kicked 7ft out of it in the past, but i figured my tuning was horrible because it flashed over so much from the topload to the primary, racing sparks (its hard to tell if that bolt hits the ground, from a peice of wiring that was poking out, or if it was on the secondary)
No visual burns though, shiny poly still.
I figured it was bad tuning. Then when i clicked on burst mode, it went to HELL and i HAD to turned it off! X_X
Could have been the secondary...or my wires.
In this video i tried burst mode at 1:50 but it really REALLY hated that...
Killa-X, Mon Jun 11 2012, 01:25AM
Verdict is, I'll try leaving it as a helical and see how things go. I have kicked 7ft out of it in the past, but i figured my tuning was horrible because it flashed over so much from the topload to the primary, racing sparks (its hard to tell if that bolt hits the ground, from a peice of wiring that was poking out, or if it was on the secondary)
No visual burns though, shiny poly still.
I figured it was bad tuning. Then when i clicked on burst mode, it went to HELL and i HAD to turned it off! X_X
Could have been the secondary...or my wires.
In this video i tried burst mode at 1:50 but it really REALLY hated that...Re: Medium size DRSSTC - Primary Flat or Helical
Goodchild, Mon Jun 11 2012, 07:13AM
Oh my.... Please tell me that's not how you had your secondary wired to the toroid?!?!?!
That wire is probably half your problem. Tuning is also not as big a deal as your issues with your coupling, resolve the coupling and that wire first and you will stop have problems with flashovers. Tuning comes second.
EDIT
I can see the spark coming off the tip of the wire in your photo and racing down the secondary...
Goodchild, Mon Jun 11 2012, 07:13AM
Oh my.... Please tell me that's not how you had your secondary wired to the toroid?!?!?!
That wire is probably half your problem. Tuning is also not as big a deal as your issues with your coupling, resolve the coupling and that wire first and you will stop have problems with flashovers. Tuning comes second. EDIT
I can see the spark coming off the tip of the wire in your photo and racing down the secondary...
Re: Medium size DRSSTC - Primary Flat or Helical
Killa-X, Mon Jun 11 2012, 03:47PM
Seeing I had to build it with low cost materials, i had to connect the copper rings and the conduit using thin copper wire that I just twisted around each ring maybe 10 time, and secondary wire just connects to it. I had no better ideas, other than just take that wire and shove it up :P
I tried a solid AL topload, not at full power but, sparks were 100% the same as my topload in terms of length to power. If anything my topload (a little bigger) had better kick.
Mind these pics are from the halfbridge days, taken like 5 months ago
[Edit: Oversize picture]
Killa-X, Mon Jun 11 2012, 03:47PM
Seeing I had to build it with low cost materials, i had to connect the copper rings and the conduit using thin copper wire that I just twisted around each ring maybe 10 time, and secondary wire just connects to it. I had no better ideas, other than just take that wire and shove it up :P
I tried a solid AL topload, not at full power but, sparks were 100% the same as my topload in terms of length to power. If anything my topload (a little bigger) had better kick.
Mind these pics are from the halfbridge days, taken like 5 months ago
[Edit: Oversize picture]
Re: Medium size DRSSTC - Primary Flat or Helical
Kizmo, Mon Jun 11 2012, 04:25PM
Flashovers like that are classic symptom of bad tuning and overcoupling.
Higher coupling you have, more precise your tuning has to be.
Kizmo, Mon Jun 11 2012, 04:25PM
Flashovers like that are classic symptom of bad tuning and overcoupling.
Higher coupling you have, more precise your tuning has to be.
Re: Medium size DRSSTC - Primary Flat or Helical
Killa-X, Mon Jun 11 2012, 08:38PM
Is there a typical rule of thumb of how high you want your first secondary turn to be from the first (lower) primary turn? Or should I just make 5 woods blocks, 1/2" thick, 12" diameter, and stack one at a time, until the coil seems to perform best?
Killa-X, Mon Jun 11 2012, 08:38PM
Is there a typical rule of thumb of how high you want your first secondary turn to be from the first (lower) primary turn? Or should I just make 5 woods blocks, 1/2" thick, 12" diameter, and stack one at a time, until the coil seems to perform best?
Re: Medium size DRSSTC - Primary Flat or Helical
Dr. Drone, Mon Jun 11 2012, 09:57PM
Dr. Drone, Mon Jun 11 2012, 09:57PM
Re: Medium size DRSSTC - Primary Flat or Helical
Killa-X, Tue Jun 12 2012, 04:19AM
Thanks for the tips. Sounds like something I'll have to do down at the lab where I have space to blast arcs big enough to flash over hehe. But i got things to do before then. Such as a better primary tap. Right now, I have a bent copper 1/4" hook, just resting on a tap. Rather sucky isnt it :D
Killa-X, Tue Jun 12 2012, 04:19AM
Thanks for the tips. Sounds like something I'll have to do down at the lab where I have space to blast arcs big enough to flash over hehe. But i got things to do before then. Such as a better primary tap. Right now, I have a bent copper 1/4" hook, just resting on a tap. Rather sucky isnt it :D
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