Tesla Coil Build Thread

[Sigurthr]

Forgive the double post: My phone can't load the above post in entirety in the edit window, so I can't just edit it.

I started winding the secondary today. %$#@ it is a pain in the ass! Wow.. next coil will need to have a winding jig made or some kind of gear driven coil winder bought. This is nuts, lol. Anyway I finished a little over 15 inches of winding, which means I've surpassed the 1000 turn mark in one night. Hardest part has been preventing and correcting slippage which causes the turn I'm laying down to lay over a previous turn and displace it. I've corrected every slip so far with only minimal unwinding needed each time, but I am taping the coil down every 3/4" or so, so I can't lose too much progress.

Tomorrow I head to the hardware store and pick up the plexiglass insulating sheets and pvc endcaps (and various other bits, including the urethane coil sealer).

Will update with pics tomorrow.

 

[Seoul_lasers]

Pretty good looking primary coil. Now for the fun part. Mounting the coil.

For this I recommend PE cutting board and or 1/2" white PVC pipe and zip ties. For the power you are running, I think you may skip the strike rail as your sparks will not be big enough to warrant one just yet. If you were running 12Kv +60-120mA I might be concerned. You'll be lucky if you get +20" from a low power coil like this.

 

[Sigurthr]

Okay! I finished the coil tonight! Man it was hard work but it came out nice! Tomorrow I fire her up for the first time and tune her up.

Note: NO HV points are touching any wood at all. I used Nylon 1/4-20 bolts and nuts for all HV connections and tie downs. There is a sheet of plexiglass under the primary, and the stationary primary lead (for the first turn) is inside a 1" PVC tube. The spark gap is now in a 2" section of 1" pvc tube for increased airflow and HV insulation. The HV terminal on the secondary is never routed inside the coilform to avoid interal arcs/streamers. The LV RF Ground side is only present inside the coilform via the head of a single screw that holds on the stress relif RF ground terminal.

Primary is tapped at the predicted 13.8 turns from javaTC modeling. Up to 14.75 turns are supported. Topload is only resting on the top cap for easy removal. Secondary is removable for easy transportation/storage.

Predicted resonant frequency: 150kHz
Predicted primary peak current: ~200A (way down from the 1500A my smaller coil was pulling)

Pics:

Video: SGTC V2.0 - YouTube


That smaller secondary I had fell apart last night. It got VERY cold because we were expecting 70+ degree weather today from the local news, but they goofed, and it was in the 40s during the day. At night it got down to the 30s in my office as I left the window open. We had turned off the huose furnace to save money and to not get too hot. I woke up to find the coil in a mushy slump on the surprisingly black coilform with lots of carbon tracking. I scrapped the entire thing. DO NOT BUY FROM KR_SCOTT ON EBAY. HE DOES NOT SEAL HIS COILS OR WIND THEM TIGHLY AND USES BAD PVC.

 

[Seoul_lasers]

DO NOT TURN ON THE TESLA COIL!

There are some fatal errors I can see already.
If you turn it on expect racing sparks.

1) the TC primary needs to level with the bottom 1-2 turns of the secondary!!!!!!!!!!
2) The inner turn closest to the coil is tapped from below the coil. It stays static!
3) The ground of your secondary coil is ALSO tapped from below the coil!! **NEVER** have it near the vicinity of the primary or it will cause problems with the magnetic field. (theres a whole bunch of stuff that can happen, none pleasant.)

YOu're going to have to fix these things before getting your coil running. If you decide to run the coil like this, you'll destroy your secondary from racing sparks.

 

[Sigurthr]

Don't worry I haven't turned it on yet!

Re:
1) I disagree; the coupling efficient would be too high if this were the case in this coil. Modeling has shown that having the secondary one to two inches above the primary results in a coupling coefficient of 0.1 to 0.13, which is the ideal range. If I lower the secondary (effectively raising the primary) the coupling coefficent soars to over 0.15. In my little coil I got racing sparks at anything over 0.14. Everything I've read says racing sparks are from overcoupling, not undercoupling.

2) Yes, the inner most turn is static and doesn't move. Magnetically the wood/plexiglass is not there so how does having it come out from below the secondary and go across differ from coming out above and go across? I don't have the money, tools, or materials to make a two layered TC base. I haven't seen anything that says a single layer coil can't be done and I've even seen coils run at teslathon videos that are single layer. If I'm wrong on this please show why, because it just looks like a convention and not a rule.

3) This I CAN change rather easily. I can tie the RF ground lead from the secondary to the bolt that holds on the bottom pvc cap and route the ground from underneath. It would be actually closer to the primary than it is now though, except underneath the acryllic and wood instead of over it. Would this really make a difference?

Update: Just fixed number 3 as follows:

Will proceed on to testing now on low power.

Update:
I tested it out and it took forever to figure out that I can't use a topload with this coil. For some reason the self capacitance of this secondary is through the roof. I removed the topload and tapped the primary at the very end of the spiral (14.75 turns) and I was able to get 4" to 5" sparks. They don't look like very hot sparks though, thin and wispy, like from a CW multiplier. Overcoupling definitely isn't an issue now, and I've only got one thing left to try to raise the coupling... removing the bottom pvc cap and setting the secondary down right on the acryllic base. I'll have to be careful not to have the RF ground arc to the primary, but it may help. This the last thing I can think to do. It's freaking 55ft of primary coil. If this doesn't work I give up on SGTCs until I have a proper work space and live in an area where building materials are available. Heck I'll just save up for EVR's MicroBrute and be happy with it.

 

[Seoul_lasers]

Actually, you can get racing sparks from both situations. Any mismatch in coupling and it can cause problems. I guess you aren't at the power where this can occur, good thing. Your sparks are puny because "as you said it yourself"you are severely undercoupled. The primary has got to be raised so that it is flush with the bottom 1 or 2 turns of your secondary. Also the new primary's innermost turn has got to be about ~2" away from the coil. You need a 2" gap so that you won't be over-coupling once you move the primary up. The inner turn of your primary doesn't move. the outside leg does.
Check the 2 pics out carefully.

I agree. loose the monster end cap. It's FAR too big. IF it can't be removed you're going to have to drop the secondary down a few inches. That will involve cutting a hole in the board.
Primary needs to be widened out. 2" clearance and you are also going to have to make sure you have 0.8" clearance between each turn. Otherwise you're going to arcbite your primary. interarc between turns.

 

[Sigurthr]

I concede. However, please understand that I put my faith in JavaTC from the advice of the big names in the field, only to have my faith misplaced.

I removed the end cap and it didn't seem to help any, though it only raised the secondary by 1/2" or so. I also raised the primary nearly an inch by stretching it, which also didn't seem to help any.

I noticed something though: the work table I had it on while testing outside was interfering with the primary magnetic field. It has steel in it under the top. I moved it off the table and on to the concrete floor and it heavily shifted the tuning point. I have to rebuild the tap connection, I had used solid core 10ga wire and it broke from all the movement.

So, I'll be trying it inside on a plastic table and trying to work things out a bit more.

I'd like to raise the primary, but I don't have any way of cutting a 5" hole in the acryllic I'm using as insulation for the primary, nor do I have anything insulative for the primary to rest on instead. Any ideas?

The only thing I can think of now is to use a conical primary, like the first image in your post #68. This copper should be hard enough now to be self supporting until I can work out a more secure method.

 

[Seoul_lasers]

I concede. However, please understand that I put my faith in JavaTC from the advice of the big names in the field, only to have my faith misplaced.

I removed the end cap and it didn't seem to help any, though it only raised the secondary by 1/2" or so. I also raised the primary nearly an inch by stretching it, which also didn't seem to help any.

I noticed something though: the work table I had it on while testing outside was interfering with the primary magnetic field. It has steel in it under the top. I moved it off the table and on to the concrete floor and it heavily shifted the tuning point. I have to rebuild the tap connection, I had used solid core 10ga wire and it broke from all the movement.

So, I'll be trying it inside on a plastic table and trying to work things out a bit more.

I'd like to raise the primary, but I don't have any way of cutting a 5" hole in the acryllic I'm using as insulation for the primary, nor do I have anything insulative for the primary to rest on instead. Any ideas?

The only thing I can think of now is to use a conical primary, like the first image in your post #68. This copper should be hard enough now to be self supporting until I can work out a more secure method.

I know Java TC well as I used it to build all of my gallery TC's. Please be aware, that Java TC
calculator assumes you have the right setup and spacing of the primary. It is meant as theory.
In practice the losses and slight primary imperfections, supply wires, sparkgap efficiency will change your numbers that you've used for the calculator.
Still, conical primaries inner most winding still requires a coupling from the bottom turns of your secondary. You can't get around it. Sorry.

 

[Sigurthr]

Hmm. Do you think having the TC on that table with the steel could have effectively reduced the inductance of the primary? This would have given me the impression of the secondary having too much capacitance. If so, then I can use a very small topload and adjust the primary coil for more spacing and more coupling as suggested.

Do you think I'll need all 14.75 turns of the primary?

If I cut off the extra coilform on the secondary's base and remove the bottom cap I can get it the same height as the primary by shimming up the primary short bit.

I can then cut one or two of the innermost turns of the primary out to get the needed 2" spacing. This of course means I would only have 12.75 turns of te primary though. This would also let me route the primary feed under the primary as well.

Sound like a plan?

 

[Seoul_lasers]

Hmm. Do you think having the TC on that table with the steel could have effectively reduced the inductance of the primary? This would have given me the impression of the secondary having too much capacitance. If so, then I can use a very small topload and adjust the primary coil for more spacing and more coupling as suggested.

Get away from the steel table. most certainly it could be interfering with your magnetic field.

Do you think I'll need all 14.75 turns of the primary?

If I cut off the extra coilform on the secondary's base and remove the bottom cap I can get it the same height as the primary by shimming up the primary short bit.

No, probably not. I don't think you'll be needing all 14.75 turns unless you plan on making a really huge toroid. 9.5-10 turns for a 14" toroid should be plenty. You'll have to experiment.

I can then cut one or two of the innermost turns of the primary out to get the needed 2" spacing. This of course means I would only have 12.75 turns of te primary though. This would also let me route the primary feed under the primary as well.

Sound like a plan?

Yes, you can cut the inner turns until you have 2" space between the secondary and primary.

 

[Sigurthr]

UPDATE!

WHOO HOOO!

It was just the $%#^ing table. My models were fairly close to correct. The secondary does have higher capacitance than formulae predict, but it isn't as bad as I thought. I put on a modest topload with a break outpoint and easily tuned the coil by tapping right at 13 turns. I didn't even adjust the coupling yet (and I don't have much desire to now that the coil works well), it is still set up how it was last night where I stretched the inner turns of the primary up a little bit. So, it is undercoupled, but not seriously. Maybe 20% under norm.

10 inch streamers at fairly often intervals, most at 9 inches, some at 11 inches. I AM HAPPY!

I will update this post (or thread) with pictures and video shortly!

P.S.: Seoul_Lasers, thank you very much for all the insight and help. At times my tone may have seemed unreceptive and unappreciative, and I apologise for that.

 

[Seoul_lasers]

UPDATE!

WHOO HOOO!

It was just the $%#^ing table. My models were fairly close to correct. The secondary does have higher capacitance than formulae predict, but it isn't as bad as I thought. I put on a modest topload with a break outpoint and easily tuned the coil by tapping right at 13 turns. I didn't even adjust the coupling yet (and I don't have much desire to now that the coil works well), it is still set up how it was last night where I stretched the inner turns of the primary up a little bit. So, it is undercoupled, but not seriously. Maybe 20% under norm.

10 inch streamers at fairly often intervals, most at 9 inches, some at 11 inches. I AM HAPPY!

I will update this post (or thread) with pictures and video shortly!

P.S.: Seoul_Lasers, thank you very much for all the insight and help. At times my tone may have seemed unreceptive and unappreciative, and I apologise for that.

Welcome to the world of real tesla coils!! :wave:
As I said earlier you can double that spark length with proper coupling. 1/2 coupled.

When your coil is properly tuned expect 19-20" peaks to possibly 22- 23".
Welcome.

Glad my years of building classic TC's for installation pieces has given you some direction and help. :beer:

 

[Sigurthr]

Haha, thanks!

Aye, I'll wait to really iron out the kinks until I can REALLY do it RIGHT next time. Basically I need the capability of machining some plexiglass/acryllic into a real primary coilform/supports.

Here's the Pics and Video!

I present; Sigurthr's Spark Gap Tesla Coil (SGTC V2.0) - YouTube



Also; I've ordered the parts to make my first SSTC; Steve Ward's SSTC-6 (aka the "MicroSSTC"). I'm not really looking forward to winding another secondary though, haha, but it is a labor of love. At least I have all the coilform needed for it now and plenty of both primary and secondary wire. Since it is a super low power SSTC (it runs on rectified 25V AC) and uses very high coupling I can literally wind the primary ON the secondary and not worry about dielectric breakdown of the primary insulation. It'l be a nice little desktop TC that is completely safe.

 

[Seoul_lasers]

You don't need acrylic supports for the Primary. Just use some white PVC pipe.
That what I use for my gallery coils. it is
1) far cheaper than acryllic
2) easier, I find to work with.

Looks like you'll be needing some 1" dia PVC piping. Do a measurment from bottom winding of TC to the board surface. 1"? 1.5"? ...

Cut the inner turns of the primary 2 turns and bend the inner most turn down so that you can connect it under your board.

Also, make short fat connections to your primary circuit. thicker the better. Those tiny wires are providing some significant resistance.

NExt thing you need to do is make a smooth toriod. Taurus shaped. Also you need a proper terminal connection for the top of your secondary coil.

No TC is, unless very low wattage is completely safe. You are dealing with HV at HFreq. Your nerves can't feel that frequency but I assure you it can (potentially) do damage.

 

[Hiemal]

Sig, not to hijack your thread, but I think I might give a shot at winding a secondary again...

You've given me a bit of inspiration and I want to give it a try.

I'll let you know how it turns out. In either frustration or happiness.

 

[Sigurthr]

Roger roger. Aye, new topload is definitely on the list. Being that I am so close to the end of the tuning range I am concerned with picking too large of a toroid right now though. I've seen some right small ones (say... 2" ring on 6" total diameter) which have a nice breakout point at the center being used by the pros but I can't find any for sale. I can't remember the fellow's name but I saw it on 4HV archives and the TC mailing list archives (I'm not a member of the list) frmo posts back in the early 2000's that he made some really fantastic toroids. His site seems to be defunct now and most of the other "where to find toroids" links on the archives are also defunct. I contacted Information Unlimited about toroids as they can produce them now but was told they only stock 2 sizes and the rest are all expensive custom orders. As is, the two they stock are a bit pricy, and not all that small.

Also you need a proper terminal connection for the top of your secondary coil.

What method would you recommend? I have read in many, many places to NOT drill in to the top cap of the coilform (or the coilform) as it can lead to internal arcing between HV out and RF ground. I was thinking soldering the 30ga wire to a bit of copper with a 1/4"-20 bolt soldered to it and epoxying the copper piece to the top of the coilform. This way the toroid has a secure mount and no strain on the 30ga wire.

You're right about the pvc pipe for supports. While in the planning stage I had considered bisecting some 4" pvc (so that it stands 2.25" high and doesn't roll) and notching the round side for primary placement ridges but I couldn't find anyone around with a bandsaw. There's no way I could do that with a 5" handheld coping saw. I figure if I could cut 8 pieces of 3.5" long 1" dia pvc pipe I can use them as standoffs for the acryllic sheet I have there. But I'd still need a way of cutting the circle in the acryllic. This acryllic is weird, I've worked with plexiglass before and it always cut easily without fracturing or shattering. This stuff breaks so easy. It is quite brittle. I actually bought two sheets and was going to cut the second, but it shattered when I tried to cut it with a very fine tooth blade sawing by hand with it well supported.

I wanted to use 8ga wire for the high current side but I can't buy anything larger than 14ga locally. It's a real bummer.

Re the TC safety, yup I know. But the SSTC I have planned is less than 36VA on the primary side with the transformer Steve Ward specifies. With the transformer I'll be using initially it will be only 24VA. Hammond manufacturing makes the transformer Steve Ward uses and they don't have any in stock at the retailers so it'l be a few weeks lead time, so I'll use my 24V power supply instead (the difference is about 12V DC, enough that the mosfets will still have the minimum needed on voltage, but no more really) until the Hammond transformer comes. RF burns.. sure. You can get RF burns from 1W. Stop your heart? No. That's my definition for safe. If you know of the "slayer exciter" his MicroSSTC is similar to that. It is even less output power than the EVR SSTC1.0, just enough to light a fluorescent and give some nice corona, no streamers.


Update:

That is AWESOME Jared! Hehe, this thread is for EVERYONE's TC builds, not just mine. I'm just the main contributor right now is all. If you need any help at all or suggestions on how to wind a secondary by hand in the most insane mind numbing method possible, feel free to ask! I pretty much worked out the method for a flawless hand-wound jig-free secondary. By all means though build a freaking jig if you can, haha. My brain still feels like mush... and I'm going to wind another coil for the SSTC soon!