Tesla Coil Build Thread

[USAbro]

Unfortunately you being without a scope and a strong understanding of electronics there isn't anything we can really do to help you further than what we've said.

You kinda found a "goldilocks" arrangement of circumstances that cancel out the negatives and give you decent performance in those special cases. The real problem with that is as you said; you can't move the coil or it stop working. This is sufficient proof that you've got tuning issues (ones that can't be corrected by moving the tap alone). To "fix" the coil so it works reliably will involve considerable time and effort on your part. Primarily, you'd have to make or buy a large toroid, and retune as needed.

Since you're using salt water caps, don't forget to swirl the salt water to redissolve and redistribute salt that may have settled out.

You should know that I'm only using 5nf worth of caps, I need to make more. I'm supposed to be using 15nf worth of caps I think.

 

[Sigurthr]

Aha! No wonder!

Yes, you're not running at full power, far from it, AND you are at a "happy accident" tuning point. With 5nF only, you're well matched to the tiny sphere topload. When you upgrade to 15nF you'll need the larger topload as planned.

 

[USAbro]

Oh. Maybe I should have exposed this earlier I just haven't had time to make more. I'm only using 9 beer bottles maybe that is the problem.

Edit: What's the number I must multiply by for static gaps? I've searched and scoured the thread and can't find what you specified.

 

[Sigurthr]

1.618, a.k.a. Phi.

 

[USAbro]

So do you think running at full power will let me run it away from my work bench etc?

I have to wait until Monday for recycling to go out, or actually Tuesday because Monday is Martin Luther King Jr. Day, and the trash (Recycle) guys won't be around.

After I add more caps, (15 or 20 more) do you think the big toroid will actually work?

I seems like it doesn't scale right on the coil, it's just too big looking compared to the secondary.

Edit: It seems I need 14.864nf about so I need to add about 9.5 because right now I have 5.6nf.

 

[Sigurthr]

So do you think running at full power will let me run it away from my work bench etc?

Running at full power just means more power gets delivered to the resonator instead of being reflected back at the NST. The end result would be bigger streamers, which with things as they are would pull the system farther out of tune and cause the environment to consume even more power, resulting in no noticeable gain in performance. You'd have to fix the other problems first.

I have to wait until Monday for recycling to go out, or actually Tuesday because Monday is Martin Luther King Jr. Day, and the trash (Recycle) guys won't be around.

After I add more caps, (15 or 20 more) do you think the big toroid will actually work?

Yes, definitely.

I seems like it doesn't scale right on the coil, it's just too big looking compared to the secondary.

That's an old myth, really, that things had to be in a particular ratio of sizes. N. Tesla himself had a vast array of sizes and one of his best performers was a flat "pancake" style which was arranged "on edge" like a dinner plate facing a wall.

Edit: It seems I need 14.864nf about so I need to add about 9.5 because right now I have 5.6nf.

You can have slightly too much capacitance and not suffer too much of a loss too, there's a decent amount of wiggle room. I'd say between 14.5nF and 15.5nF will do just fine.

Interesting that quotes don't count as characters in a reply. It requires that I write something outside of the quote as well. Hmph.

 

[USAbro]

And what did we discuss I'd need to fix? Sorry for asking again but I couldn't find it in the thread.

 

[Sigurthr]

And what did we discuss I'd need to fix? Sorry for asking again but I couldn't find it in the thread.

1) Increase capacitance to 14.5nF to 15.5nF
2) Move the coil away from walls, ceilings, floors, tables, benches, chairs, etc as best as you can.
3) Place a smooth real toroid topload on top, somewhere around 14.5" x 3" iirc.
4) Retune as needed.
5) Make a ground rod, and use as thick of cable or as many wires in parallel as possible for the ground cable that connects the ground rod to the secondary bottom connection. An old extension cord with the three wires connected together on each end works well.

That's all I can think of, since you're the one that's supposed to keep track of this, lol.

 

[The Lightning Stalker]

Interesting that quotes don't count as characters in a reply. It requires that I write something outside of the quote as well. Hmph.

It's probably "dumb" to save database
overhead by not checking weather there are
actually any new characters in the quote.
What I do is wrap every piece of the quote
in its own quote tags, then reply on the
outside, like this.

Thanks, Mr. The Lightning Stalker. You are a really great guy.

Oh, you're welcome. It isn't as easy,
but it works and it looks better, too.

 

[Sigurthr]

Yeah I was wrapping each bit in quotes but it is tedious to have to add all the open/close quote html code so it stays attributed to the author, especially on mobile devices.

 

[Down with Umbrella]

How do spark gap tesla coils fair in the snow??
EDIT: I read a list of TC safety rules and it warned about condensation something I suspected might be an issue.
My parents are a little leery about me turning it on in the basement. The ceiling is about 5 feet above the top load and there is a computer on that side of the house up stairs.
My plan is to unplug the tvs, playstation, cable boxes and computers. Two 15kV/30ma NST shouldnt produce massive streamers.

I could either talk to them about firing it up in the basement or bring it outside. Luckily there isn't much snow out the back door where my ground is(6 inches maybe). I could maybe put the TC on a pallet and shovel.
Has anyone else had to do stuff like this?

Also I would like to review a few safety precautions.
I have a 10' lead from the switch box to the base of the TC

1: Most of you have seen photos of my setup in previous pages of this thread. My NSTs and blower are ground to the the mains ground. Strike ring, TF, and secondary to the RF gound bus.
There is no Exposed HV to wood unless you count some of the wiring but that insulated. Primary is in wooden braces :thinking: I've seen that in many TCs.

2: Now, one thing I don't like is how close the frame of the blower is to the spark gap. That same blower ground is connected via ground to the frame of my switch box. I feel like holded the box with welding gloves but like Sigurthr said that would prevent me from being ground.
I wonder if I could just let the blower float.
3: while tuning. After I unplug the TC when is it safe to touch the primary? Let's assume all my bleed resistors soldered connects are solid.

 

[Sigurthr]

Short the spark gap with an insulated screwdriver after unplugging, then the primary is safe to touch.

Snow actually helps performance, it forms a great counterpoise.

You do have to watch for condensation.

Your only safety faux pas is the wooden primary supports. Just keep an eye on it for sparks.

If run indoors simply unplug anything you don't want to replace. Don't forget the answering machine (telephone).

 

[Down with Umbrella]

Bahahaha it is alive!

tonight I was able to take the time to start tuning my coil! phew, so far all has gone well with no major problems. I started my tap point at 10 turns on my primary then gradually moved it closer to 11. I believe I haven't found the sweet spot yet but with some fine tuning I believe I will.
here are some videos and pictures. right now I am getting roughly 30-35inch streamers from a break point out. i noticed when i increased the turn tap the streamers were starting to contact the ceiling. (previously i had stated the ceiling was 5feet above the top load. that is not correct its maybe 3.) i cant have that so this is where it sits.

The terry filter safety gap rarely fires that I notice and after watching the videos I did see a few sparks shoot down my secondary. I might have to adjust the coupling slightly. the first turns are just about level to the primary.

My top load needs some work. its not as smooth as it could be.
This is my favorite shot with the coil next to my welded Effie tower and big ben(in progress)

A big thank you to everyone who has helped me on this thread. Sigurthr, Nospin, The lightning stalker, ionlaser555 and others.

 

[Sigurthr]

Haha, awesome results DwU! You've made me a proud instructor today, haha.

Those sparks down the length of the secondary are called "racing sparks" and typically indicate a tuning issue or too high of coupling. Generally if it is just an occasional spark you work on tuning first, then raise the secondary a few mm and retune. Racing sparks can prove fatal to a secondary, so don't let it happen if you can help it. Placing the topload closer to the top turn can help too, you can cheat at this by covering the exterior of the PVC top cap with Al foil tape, just make sure it makes good contact with the HV lead or the topload itself, else it will appear electrically as a shorted turn (very bad).

Btw, your video is marked as private.

 

[USAbro]

@DWU-You make me jealous!

Anyways, today I spent 3 hours making more beer bottle caps. I connected all of them with aluminum foil in parallel with 14.2nf capacitance.

Problem is, I just hear the caps humming, and the spark gap now has to be super small (3mm) to arc rather than big (1cm). Ouput from the ball is 1cm, and output from the big toroid is 1 inch. Horrible results. Very disappointed. Also, I bought a 6' copper tubing yesterday and pounded it into the ground. Wired it up and yesterday I was getting really good streamers, with the capacitance I had 5.6nf (5" streamers to ground).

So what could be going wrong, my wiring is good, nothing is shorted. Could my caps not be good. The first several I used AL tape, but for the rest, I just wrapped them in foi and rubber band them. I used saturated salt water, and uses AL foil rolled up into long strands to connect individual bottles. I placed them all in a milk crate and am operating on my kitchen table, with the coil elevated on top of the crate.

Not sure what my problem could be, I've been messing around to see what improves output, but right now I'm not even close.

@DWU-Really good job, one day maybe I'll build something similar. Was that your first coil? This is my first. Although I must say, my budget is extremely limited. To around $200 for the entire project.

 

[Sigurthr]

USAbro: it sounds like your caps are bad if they're humming. That's a clear sign of leakage or discharge. That's why the no-foil salt water type are the best.