Mid-Sized SSTC

[Tetris]

Hello. I may seem like a new user but I've actually been part of the other forum, 4HV, for 8 years or so (I was known as TeslaGirl at the time). I attempted to build a SGTC at the time which didn't end up working because of how rather... ghetto the coil ended up being, since I was indeed 12 or 13 at the time and wasn't quite equipped to build things properly (and dad insisted on skimping on the caps, instead choosing saltwater caps in the beginning) which ended up delaying the project quite a bit.

I am rather familiar with the process of building tesla coils overall and the generic process behind it. But there are quite a few variables to consider with SSTCs I'm told, since there is apparently more than one way to build a SSTC.

I'm wondering which direction I should be pointed towards to start doing research for the purposes of my project. My father would like a list of materials and a generic plan within a week (i.e. by the upcoming Sunday). This is my current goal and the few questions I have.

I used to have a 7.5kv 30mA NST which was the transformer that powered the old failed SGTC(it failed mostly because I suck at winding secondaries). I am wondering that since I'm not a stupid kid anymore, I'd be able to handle higher powered things, and whether it's worth purchasing a 15kV 60mA NST or obtaining a few MOTs to power the SSTC.

My goal is to have a coil that "looks like a Tesla Coil" if that makes any sense. 16 inches tall, toroidal topload, mounted onto a proper thing that'll hold everything, rather than being sprawled across the floor. I know enough of F360 that I could 3D print parts if necessary (I'm not near campus right now but I have plenty of friends at campus who could get something printed for me). I'm wondering if it's wise to print the primary supports or if I can get by with using craft foam-board. My college's library only prints in PLA, so I'm not sure how that'll affect things.

I wish for it to be MIDI controlled, but I don't want to have my laptop anywhere near the running Tesla Coil obviously, so I would need a way for me to load the MIDI onto a flash drive, or even manually use some sort of micro to create the tones if it isn't possible for me to do this without buying a $100 part solely to audio modulate the coil.

There is no set budget. Dad merely said "If it is a couple hundred, it is ok, but not couple thousand for now." So I assume between $300-700 would be my budget to build the coil. I want it to look good and work. I'm capable of doing decently advanced math (I mean I doubt I'll need to manually use anything more difficult than integrals) so if I need to do any calculations I can do it.

Will I be able to build a mid-sized SSTC within that budget?

Thanks!
--
Fractal

[Mads Barnkob]

Welcome to HVF!

$300-700 is a very large budget for a SSTC, so money is not going to be a problem.

You should look at the Steve Ward SSTC2 and all the successive clones and enhancements: Steve Ward: https://stevehv.4hv.org/SSTCindex.htm or Mads Kaizer: http://kaizerpowerelectronics.dk/tesla-coils/ or Gao Guangyan: http://www.loneoceans.com/labs/sstc2/

Modifying the SSTC2 driver for a optical input, to have complete electrical isolation between your Tesla coil and computer is no problem. There is plenty of MIDI interrupters available, either to buy or build yourself. Dan/profdc9 has released many PCB designs for almost complete coils, so that is worth checking out.

You should not worry about PLA, check this study out: https://www.hindawi.com/journals/amse/2017/6913835/

To get a professional looking coil there is few steps really. Buy a spun toroid topload from ebay. Use lexan/plexiglass for the contruction and secondary coil tube. Install all electronics in a black box underneath. Use new wire bought specific for the primary winding.

Good luck and I look forward to hear more about the progress of your project

[Tetris]

Hm, it seems Steve Ward's coil, which I was thinking of following anyway, fits what I'm trying to do best (~2 feet arcs, although I'd prefer the arcs to come from the side of the topload rather than the top), but the Gao page has the best explanation of SSTC construction in general. I shall read into both over the course of the next few days and come up with a plan of action.

eBay puts those toploads around 50-150 bucks, so if this will still stay within budget I suppose it'll be good, but they have the breakout point at the top rather than the side. Will I be able to use aluminum tape to cover the top hole and affix a breakout point to the side? Or is that not a good idea?

As far as the MIDI interrupter, I suppose that's later on for me to research but how much do these usually cost?

Don't toploads add a certain degree of capacitance to the secondary which needs to be taken into account? Will I need a very specific size?

I'm really, really hoping this project will shine. The failure of my old coil is probably on my top 10 list of "biggest failures in my life" because I put so much effort and really wanted it to work. I cannot change the past, but there's no better time than the present to build the coil.

I'll come back in a few days with a better gameplan.

[Mads Barnkob]

My own rule of thumb for the SSTC topload is that the minor diameter is the same as the secondary coil diameter and the large diameter of the topload is the same as the winding length of the secondary coil. Use JAVATC to calculate the secondary coil with topload frequency etc.

profdc9's PCB pack contains a MIDI interrupter: https://highvoltageforum.net/index.php?topic=353.0

You could also just buy a cheap and limited function one from onetesla: http://onetesla.com/products/kits/interrupters-all.html

[oneKone]

Welcome to the forum.

Just thought i'd throw my 2c in.

For the driver i'd go with something more like Mads and Steve's driver vs Gao's. I've used both the ucc3732x pair and the ucc27425 in various sstc i've built, The ucc3732x pair is a much more capable arraignment as you can drive either a fullbridge or halfbridge... In no way am i discrediting Gao work though. For the fibre transmitter/receiver oneTesla sell both and also the cable cut to any size required.

As for the secondary i have messed around with different types of polyurethane and have found oil based in can form to be the best. With upwards of 10 base coats and sanding in between another 2-4 coats the finish can almost be mirror like. It's quite a bit of work but is definitely rewarding. This is one of my coils.   https://highvoltageforum.net/index.php?action=dlattach;topic=133.0;attach=1254;image

One seller i have found on ebay that sells toroids is the "highvoltageshop_com" I've only bought two toroids from them so far but both have been exceptional quality.

looking forward to seeing updates on your build.

[Spuriosity_]

In terms of getting the secondary 'good-looking,' it's well worthwhile to build a winding jig out of whatever you have available. Mine was made out of some of my old mecanno, equipped with with a janked-together 555 PWM driver for my crappy motor. I don't know how I would have done it without it (still took 3 nights' work for 1300 turns because the wire kept doubling back on itself)

https://drive.google.com/open?id=1l5J9wIa7gPZUM2VoQrz6x1FAlDG1QWEF

The important parts to it were:

• Clean the PVC pipe thoroughly, making sure to get rid of any stray fibers or dust particles. I didn't do this well enough, and my final coil has some small hairs jutting out that are very annoying and an arc-over risk. Do not wind next to a carpet like I did.
• Tape the start of the winding down securely
• Turn the winder on, keeping pressure on the wires to keep the windings tight together
• Do not let the wires cross over- undo a frew windings if you have to. Make sure to keep tension on the wire with your fingertips - if it goes loose and the wire expands off the coil form, there is no way to fix it other than unwinding and rewinding.
• If you have any kind of mechanical counter to keep track of how many windings, definitely use it. It's also possible to estimate based on how long the coil is.
• When done, tape the end wire down with a full ring of tape
• Keep the windings in place by applying some kind of lacquer. I bought some of this stuff https://au.rs-online.com/web/p/electronics-varnishes-lacquers/8232640/ and applied 3 coats of it as the thing turned on my winding jig. It's not really necessary to get specialist electronics lacquer, I just grabbed it for extra legit-ness.

[profdc9]

In the DRSSTC pcb pack, there is a board called "half-bridge-sstc" which is a simple SSTC driver based on the CD40106 hex schmitt trigger inverter.  This contains an overcurrent detector and optoisolation if you want to disable the bridge externally to implement sound control.

Dan

[pentode]

When I wound my secondary I found that one had less risk of the wire over running if your hand that is guiding the wire onto the rotating former is not too close to the former. 

[Mads Barnkob]

My DRSSTC design guide also has many parts of it that is general Tesla coil design, such as the secondary coil. http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/secondary-coil/

If you scroll down to "how to wind a secondary coil" there is both illustrations and pictures of how its done.