Re: Newbie on a learning curve
Graham Armitage, Mon Jul 16 2018, 10:08PM

My best suggestion is to become very knowledgeable on the electrical principals of TCs and resonant circuits. Then understand the components needed before putting one together. There is a wealth of information on this forum to get you going. Getting a TC working well is not simple and requires a pretty deep understanding.

Re: Newbie on a learning curve
klugesmith, Mon Jul 16 2018, 10:38PM

Applause for the slinky spring toroid!

Probably seen before, but not by me. I bet the electrical and magnetic properties of spring steel won't be a significant issue, if most turns are electrically connected in the middle. Is your Slinky "clamped" by a wire, string, or elastic cord threaded along its axis (before the slinky bend was made)? What's the electrical path between the secondary winding and the slinky turns?

Re: Newbie on a learning curve
Andy Kay, Mon Jul 16 2018, 11:25PM

Thanks for the applause klugesmith, but undeserved I'm afraid. When I have a novel requirement I hunt around for something that might do the trick, and on this occasion the hunt turned up an old slinky spring that had been knocking around for a few decades. Seemed like it might fit the bill. You make a good point, though... all I did was hot glue it to a plastic cap from a can of fly spray, and connected onto it at a single point. I will definitely update that now.

Re: Newbie on a learning curve
Gordon, Tue Jul 17 2018, 10:57AM

Congrats on wanting to experiment with a tesla coil, definitely a hobby to learn about resonate circuits. I would say definitely try a Spark gap coil yeah you have to tune it constantly but that's the fun of it. Just always remember safety. Keep your left hand in your pocket just as a precaution when going to touch anything after using the coil make sure your caps have resistors at least upwards for 5 mohms. You probably know this but feels better to just say it just in case. What are your questions about a spark gap coil or the slayer exciter version. Have you used the



To get an idea of what your coil parameters are.
For sparks have you added a break out point like a thumb tack on the outside of the slinky or a clothes hanger sticking out. Also top load comes into play too big of a top load will effect if it can produce a spark.

Re: Newbie on a learning curve
Andy Kay, Tue Jul 17 2018, 11:23AM

Thanks for the reply Gordon, and for the link (looks like a site that's worth more investigation). I've been playing with Marx generators so I'm quite familiar now with the way that even small capacitors can store enough energy to get you "conditioned" so to speak (I spend a lot of time with horses and have become just as conditioned to avoid electric fencing as they are!) Speaking of SGTCs, from what read the spark gap itself can be a big problem (wear and cooling)… got me wondering if the spark plug from an internal combustion engine might be a good choice. Anyhow, I'm looking forward to spending more time on the TC stuff (real life is getting in the way), so very happy to have found this site and will be back for more advice in due course.

Re: Newbie on a learning curve
Gordon, Tue Jul 17 2018, 02:36PM

Never thought about a spark plug but I'd be afraid of the current melting and blowing the electrode off. Most people use bolts and a set up they can change easily yeah they do corrode but nothing a quick hit with a brillo pad can't fix. The best so far I have found is brass to be quite resistant to corrosion. But with a SGTC you can get some pretty good archs and it's a great feeling of achievement after tuning it. Check out this out

Re: Newbie on a learning curve
Andy Kay, Tue Jul 17 2018, 04:48PM

Another great link! Thanks Gordon.

Re: Newbie on a learning curve
Gordon, Tue Jul 17 2018, 04:56PM

Here's mine using saltwater capacitors with 12 beer bottles in a 5 gallon bucket gave me 12.5 uf but not efficient but worked

Re: Newbie on a learning curve
Gordon, Tue Jul 17 2018, 04:59PM

Here are some cheap capacitors that work they haven't blown up yet but they work they ship from China so it takes awhile to get here but using these you have to parallel resistors to each capacitor.
TOOGOO(R) 100pcs CBB Metallized Polypropylene Capacitors 104J 0.1uF 1600V Font color white, black random

Re: Newbie on a learning curve
Andy Kay, Tue Jul 17 2018, 09:40PM

That's awesome. I like the mini-streamers where the aluminium foil is kinked... looks cool.
I already have a pack of those waiting for me to engage in earnest. Gathering all the bits together always seems to make the actual task seem less daunting. I also have a 200 pack of 1W 1mohm resistors that I've been wiring 4 in series and then covering in heat-shrink to get the voltage tolerance up. They work well in the Marx generator, which is driven from a TV-style flyback transformer so I'm guessing upwards of 20kV.

Re: Newbie on a learning curve
Fumeaux, Wed Jul 18 2018, 06:34PM

I think i have an idea for you. First you can approximate the frequencies with an online tesla coil design software (I can recommend http://www.classictesla.com/java/javatc3d/ javatc3d.html for that purpose). Secondly you can tune most tesla circuits in a certain range. This is true for SGTC (tapping the primary coil) and most solid state can be tuned too (for an SSTC I think this might be a solid starting point http://uzzors2k.4hv.org/projectfiles/pllsstc1/PLL% 20Half-bridge%20SSTC%201.GIF).

If you want to go the SGTC route, you need a HV-transformator and caps. The easiest thing is probably to gut some microwaves for the transformators and hv-caps.

I hope that helped a little.

Re: Newbie on a learning curve
Andy Kay, Wed Jul 18 2018, 11:46PM

Thank you for this... that is a really interesting circuit. It took me a little while to work out what is going on but now the penny has dropped it looks really inviting. Incidentally, I have two MOTs and HV capacitors and I would like to get around to building a SGTC eventually, but the SSTC you suggested looks more enticing right now. (I have to admit that I was a little disappointed to find that the power transistors used are MOSFETs, since I'm intrigued by these IGBTs that are available nowadays and was hoping to get a chance to play with some, but I'm sure their time will come.)

Re: Newbie on a learning curve
Andy Kay, Thu Jul 19 2018, 04:56PM

@Fumeaux:
I'm very enthusiastic about this little circuit! I've ordered all the parts and I'm looking forward to trying it out. Thank you so much.

Re: Newbie on a learning curve
Fumeaux, Sat Jul 21 2018, 02:49PM


No problem, but there 2 more things I want to tell you. First, the capacitor on pin6 & 7 sets a certain frequency range. You can read more about this in the datasheets of the cd4046. Second, I wrote some extra information for you. I recommend to build the green and red sectors on different breadboards inorder to upgrade the TC in the future.

PS: As it is only halfwave rectified you dont have to worry about overcurrent, but if you use fullwave in the future you will need to build an interrupt curcuit.
And the last thing: Make sure to have a big enough heatsink for the mosfets.

And the really last thing: think ahead and protect your mosfets (zener diodes, flyback diodes,.. like here http://rpsx.eu/upload/U3RBsZAI.png) or buy plenty before you play around/ or get a variac

Re: Newbie on a learning curve
Andy Kay, Sat Jul 21 2018, 03:48PM

Thanks for the extra guidance. I already have experience of gate sensitivity from playing around with Marx generator drivers, so I have plenty of 15V TVSs and Zeners. And I already have a 50A full wave rectifier that I considered using, so it would be good to know more about this "interrupter circuit" that you mention.

Re: Newbie on a learning curve
Fumeaux, Sat Jul 21 2018, 05:44PM

Think of it like pwm. The frequency of the pwm is an audible frequency and with the width you controll the power.
An interrupter sends a pwm to the ucc-chips and turns them on&off (pin3).

For the diagram, there is a lot of them on google. But generally, there are simple ne555 timer ones or musical interrupters.

Re: Newbie on a learning curve
Andy Kay, Sat Jul 21 2018, 11:53PM

Ah... okay, so you seem to be saying that replacing the rectifier diode with a bridge rectifier will mean that some method of current limiting is required, and the interrupter circuit fulfils that role, right?

Re: Newbie on a learning curve
Fumeaux, Sun Jul 22 2018, 07:58AM


Yes kinda. But you limit the power in the mosfets. The biggest reason is: you can maximise the arclength (voltage in) without burning up the mosfets. And lets be real. A musically interrupted TC is awesome.

Without interrupting it is called CW-mode
looks like this: https://www.youtube.com/watch?v=4lyhIyLlTug
this is demanding on the mosfets

And here are some interrupters from kaizer:
ne555: http://kaizerpowerelectronics.dk/wp-content/ gallery/2009_07_22_-_Kaizer_SSTC_III/ KaizerSSTCIIIdriver.gif
musical: http://kaizerpowerelectronics.dk/wp-content/ gallery/2016_09_03_-_music_modulator/ musicmodulator.gif
both in configuration: http://kaizerpowerelectronics.dk/wp-content/ gallery/2009_03_15_-_kaizer_SSTC_II/ KaizerSSTCIIdriver.gif

Re: Newbie on a learning curve
Andy Kay, Sun Jul 22 2018, 05:52PM

Yes, I can see how the 555 is used here as a kind of PWM "volume control". The musical coils I will leave for now. I'm assuming that the four secondary coils in the last .gif file are for driving a full bridge MOSFET configuration... I like that idea. For now I'll work with the simplest of the configurations you gave me, and I'll let you know how I get on (though it may take a while). Thanks for all your encouragement and advice Fumeaux.