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Registered Member #1900
Joined: Fri Jan 02 2009, 06:44PM
Location: Texas
Posts: 29
Hello all,
I am amazed how I have not been able to find this site before. I have been looking for people to run ideas past. I am currently a Junior in an ECE program and my goal is (surprise) power engineering. The junior design program, I believe, is not all that strict so my girl and I would like to build a medium sized SGTC before we move on to more complicated electronics in an SSTC. The most attractive goal for a year and a half from now (Senior design completion) would be to have a working audio modulated SSTC. This came after meeting the ArcAttack guys at Dragoncon and talking with them about it, however they seem to have cut off contact with me.
It looks like SGTC's are somewhat a thing of the past, considering the interest in solid state here, but I have supervised the building of a small SGTC before and I figure I should stick to what I know first.
I have a few questions. 1. Is the Ultimate Guide to TC construction a good resource? I have been using the book and design spreadsheets to design the coil and learn about its operation.
2. Are there any benefits of the rotary spark gap apart from control over the BPS?
3. It's difficult to find transformers for reasonable prices. Is there a good resource here that I have missed? I currently have had my eye on a 15kV 120mA NST to kick the project off, what kind of performance can I expect?
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
1. All I know about coiling is something I have read for free from various sites, most of them by users of this forum. Its all a great collection when you know them all and can put them together as a working collection.
richie burnetts site have good theory, deepfriedneon.com got some nice calculators and a rough design guide, and classictesla.com got my favorite complete tesla coil analyzer.
2. with rotary spark gaps you can gain longer sparks from the same input power as with a static spark gap, as you can time the shoots with the frequency of the NST.
3. 15kV 120mA is a big transformer, with 1800W input you could expect up to around 72" / 180cm sparks, might even be too big for a starting project as the safety measures raises with the power, also it might even be too large to build where you have the place.
Registered Member #1900
Joined: Fri Jan 02 2009, 06:44PM
Location: Texas
Posts: 29
Thank you MadsKaizer! To keep the input current low and avoid limiting available capacitance (I have read that higher spark frequency does this), I will probably get a rotary gap but stick with 120BPS.
Also, could I add some ballast to further limit the current in the transformer, if necessary?
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
If im not mistaken, 120BPS is not healthy as the resonant voltage rise in the NST due to it hitting every high/low in the cyclus will be so great the NST will selfdestruct. This is where you will meet the term LTR (larger than resonant) More reading here:
You could ballast with a lightbulb, heating element or a shorted transformer, but I do not know enough about this to go in further details, you have to do some more searching :)
Registered Member #1127
Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139
Angstrom wrote ...
Hello all,
I am amazed how I have not been able to find this site before. I have been looking for people to run ideas past. I am currently a Junior in an ECE program and my goal is (surprise) power engineering. The junior design program, I believe, is not all that strict so my girl and I would like to build a medium sized SGTC before we move on to more complicated electronics in an SSTC. The most attractive goal for a year and a half from now (Senior design completion) would be to have a working audio modulated SSTC. This came after meeting the ArcAttack guys at Dragoncon and talking with them about it, however they seem to have cut off contact with me.
It looks like SGTC's are somewhat a thing of the past, considering the interest in solid state here, but I have supervised the building of a small SGTC before and I figure I should stick to what I know first.
I have a few questions. 1. Is the Ultimate Guide to TC construction a good resource? I have been using the book and design spreadsheets to design the coil and learn about its operation.
2. Are there any benefits of the rotary spark gap apart from control over the BPS?
3. It's difficult to find transformers for reasonable prices. Is there a good resource here that I have missed? I currently have had my eye on a 15kV 120mA NST to kick the project off, what kind of performance can I expect?
Thank you.
Well in fact you can make a 12 kV high power unit by using 2 Microwave Oven Transformer units rather easily. This is a pulsed DC circuit rather than an AC one - but you can certainly power a Tesla Coil with it! All the components for your rectifying circuit can be found inside the microwave itself. MO diode bricks and two MO capacitors that are rated at 2 KV (AC) or 5 kV DC. The output from this device is nearly 0.5 A / 12 kVDC pulsed at 60 Hz.
Greg Hunter has the schematic on how to build one at this link:
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Angstrom wrote ...
Hello all,
I am amazed how I have not been able to find this site before. I have been looking for people to run ideas past. I am currently a Junior in an ECE program and my goal is (surprise) power engineering. The junior design program, I believe, is not all that strict so my girl and I would like to build a medium sized SGTC before we move on to more complicated electronics in an SSTC. The most attractive goal for a year and a half from now (Senior design completion) would be to have a working audio modulated SSTC. This came after meeting the ArcAttack guys at Dragoncon and talking with them about it, however they seem to have cut off contact with me.
It looks like SGTC's are somewhat a thing of the past, considering the interest in solid state here, but I have supervised the building of a small SGTC before and I figure I should stick to what I know first.
I have a few questions. 1. Is the Ultimate Guide to TC construction a good resource? I have been using the book and design spreadsheets to design the coil and learn about its operation.
2. Are there any benefits of the rotary spark gap apart from control over the BPS?
3. It's difficult to find transformers for reasonable prices. Is there a good resource here that I have missed? I currently have had my eye on a 15kV 120mA NST to kick the project off, what kind of performance can I expect?
Thank you.
If your specializing in power engineering, than you should definitely go the SSTC route. You'll learn a lot more pertaining to your field of study and the parts are more readily available too, especially for the newer DRSSTC type of coils.
Go for a entry level DRSSTC. Steve Ward has some nice plans and designs for a small DRSSTC and it can be built with readily available parts. No need for special high voltage transformers which are difficult to get these days or the need for mechanically complex spark gaps.
Or if you want to try some snazzy audio modulation, go for a small Class-E 4MHz SSTC. Richie Burnett and Reaching (another member here) have good plans for a nice class-E coil. This is super duper for your field of study as it teaches you a lot about resonant topologies. Reaching has a nice schematic for a simple class-e with a high-side linear modulator. Very easy to do.
Registered Member #1517
Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304
I have used the UTCG, I read it mostly for theory and for occasional tips on what to be doing and looking for. But honestly, building my coil consisted mostly of checking numbers on deep fried neon and imagining the parts together in my head. The book is excellent for tuning your coil, but lacks a bit in the construction guide, as it is sort of outdated.
SSTC's are the way to go, but if you have not yet built a SGTC on your own, it is a good idea to tackle that first.
Registered Member #1900
Joined: Fri Jan 02 2009, 06:44PM
Location: Texas
Posts: 29
Thanks all,
The DRSSTC is looking more and more attractive. Is it feasable to adapt an already constructed DRSSTC for audio modulation? I figure we should go one step at a time.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
About the SGTC.
A good starting point would be perhaps 2 inch diameter 10 inch tall secondary with a small neon transformer. I have a 6kv 30ma nst that i could sell for 20 bucks+shipping. The only this that is wrong is one of the primary screw terminals was cross threaded and it chipped the ceramic. Other than that is works fine.
The approximate capacitance you would want with a 6kv 30ma nst is 18nf. That is easily obtainable with 8 of those CDE .15uf 2000vdc capacitors. With that the dc voltage would be 16000volts, so they would be good for about 8kv without a safety margin. You of course want the safety margin, which you would have 4kv safety margin. For 10 of those capacitors it is something like 40 dollars, which is worth it because they work very well.
What i usually go by is not using arsg's unless it is dc resonate charging. The reason for this is that with arsg sometimes it will fire when the voltage is low due to the 50/60 hertz ac. So, right when it changes polarity it will try to fire, but it hasn't enough voltage to jump the gap, so it will miss a beat.
A srsg would be good, however a good blown static gap would be good enough.
A good topload would be something like a 4 inch diameter gazing ball, or a good smooth toroid.
The primary, since the wattage of a tesla coil like this is low, could just be some thick solid wire, or it could use some small copper tubing.
The theoretical spark length for this input is 22 inch sparks, but that is not easily obtainable.
That was just a starting point, if you are looking for something bigger, just ask and me or someone else can tell you dimensions.
Registered Member #1127
Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139
DRSSTCs can be quite costly. Finding the components can be tricky to - and then ~ pricing. Just a warning - SGTC's are an easier build.
You could build the killer power supply for much less than $20 bucks. About those capacitors - more on board = less heating. So I'd design the capacitor network for 2 - 3 X the voltage input rating. I'd certainly be concerned with heating with so few caps.
I'd go with a 4" diameter secondary wound with 24 AWG wire - say 1800 turns and a 3/8" copper tubing primary. With the MOT power supply running say 3 kVA - you'll hit 50" without too many problems. Your capacitance might be 70 nF --- it will be a wild coil!
Not sure if you are on a tight budget or not... but this was my starter coil some years ago. MOT's are very powerful beasts! If you need a schematic please feel free to send me a private message with your email and I'll send you easy to follow schematics.
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Design Project - SGTC
