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Solid state Tesla Coil with a 1:1 transformer?

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Yergaderga

Member
Hi,
I recently decided that Neon Sign Power supplies are too expensive and dangerous for me, and I started looking into solid state after getting a small kit Tesla Coil. Instead of all of that circuitry, couldn't I just attach a 1:1 transformer to the wall with a couple fuses and connect that to the primary of my coil? I don't need to tune it incredibly well, just enough for decent arcs. I just thought, since the transformer outputs ac (right?) I could use it instead of rectifying it and making a complex oscillator using mosfets that output similar voltages. It doesn't need to be thousands of cycles a second. Anyway, thanks,
Yergaderga.
 
Absolute no-no. A Tesla coil operates at a much higher frequency (perhaps a few hundred kHz) as compared to the power line (50-60 Hz). That's the purpose of "all that circuitry", to generate the required high frequency. Thus you can't connect the Tesla coil to the low frequency power line and expect anything but a possibly blown coil. If you don't understand the fundamentals of a Tesla coil then you shouldn't be playing with them.
 
This is what I don't get- Tesla himself ran coils off of "pulsed DC," aka a Ruhmkorff/ induction coil. They oscillate really slowly. Also, spark gaps do not oscillate very fast either, I wouldn't imagine, and an NST sure sounds like a 60hz output. I researched oscillators for tesla coils with mosfets, and I'm trying to design one with two irf510 MOSFETs.
 
I don't mean to be rude, but you clearly don't know how a Tesla Coil actually works, especially the solid state types.

NSTs do have a 50/60hz output but the tank circuit (capacitor coupled with the primary coil) creates a much higher frequency (100s of KHz, usually) which is seen at the output. Solid State Tesla Coils still need this oscillation to function correctly, and in order to get any arc at all you really do need to tune it pretty well. Take my word for it, a lot of math, science, and physics goes into designing and/or building a Tesla Coil, and to be perfectly honest it doesn't sound like you're prepared to do that. I have built several Tesla Coils before--I am a huge fan of Tesla, myself (hence my profile picture)--and the difference between Tesla building coils and you building them is that he understood the math, science, and physics behind it.

Please don't try what you're suggesting, it's dangerous and could seriously hurt you or others around you, as well as damage property. Normally I encourage people to build Tesla Coils, but that is only if they know how they work. To be painfully honest, you are just asking for trouble.

Please take our advice and look for a different project. Either that or use an existing SSTC circuit design rather than designing one yourself. You don't seem to understand the level of knowledge that needs to go into the designs.

Regards,
Matt
 
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Thanks for clarifying, I'll read into this. I was also thinking about a flyback driven coil. I made "bucket capacitors," and I'm going to adjust them as needed. This was just something I was confused about. I'm still researching how they work before I start, obviously.
 
Thanks for clarifying, I'll read into this. I was also thinking about a flyback driven coil. I made "bucket capacitors," and I'm going to adjust them as needed. This was just something I was confused about. I'm still researching how they work before I start, obviously.

So you're building a spark gap Tesla Coil instead of a solid state one? "Bucket capacitors" are really only needed for SGTCs, not SSTCs.
 
Yeah! but he was a leader in his field!!!

Exactly! He KNEW the science and math behind it! And there was a lot more to those coils than this member seems to realize :p

EDIT: I'm sorry, reading this again it sounds very rude, I did not intend it to be that way. My apologies, Yergaderga.
 
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schemeit-project.png
I'm going to embarrass myself, but what can I do to improve this? I watched a tutorial on mosfet oscillators and I came up with this. I actually might use 9 volts input. The 5 volts is from a 555 timer. Does this work, and what should the resistor values be? It's really basic and will obviously need improvement. I just don't want to spend a lot on it.
 
By the way, yes, I know a flyback Coil isn't solid state. I'm not THAT stupid! It just seems that flyback drivers use less resources than an entire SSTC driver. I will use a spark gap, so it will NOT be solid state, but I'm starting to care less about that. I've been reading up on safety, etc.
 
Fair enough. And I was not trying to imply that you were stupid, simply that you may not understand the full extent of what you are doing.

The above circuit will work, somewhat, but it lacks important protection circuitry. If you run it as shown, there is a strong possibility that you will fry your low-voltage circuitry in an instant. Also, the signal sent from the 555 is very touchy, in order to drive a flyback transformer you'll need a duty cycle of about 20%, which is difficult to do with a simple 555 circuit. I recommend looking up a PWM circuit. I know rmcybernetics.com had a really nice one that I used for a long time that implemented a 555 and a 393 comparator to produce a signal with independent frequency and duty cycle adjustment. That is really what you'll need.

Again, protection circuitry is a must, for example flyback diodes (Schottky diodes are good, though 1N4007s will work as well). Might want an RC snubber too.

I am glad to hear you've been reading more about it. I would be more than happy to help you out, provided you do the research before trying it. Now that you're talking about a safer, more reasonable design I can certainly give you direction if needed. :)

Regards,
Matt
 
I get what you meant. By the way, I like the Douglas Adams quote. That's hilarious! I've only been interested in this since summer, so I have a lot to learn. For the longest time I didn't know what an oscillator was, so I kept searching "how to make AC from DC." Thankfully, I figured it out eventually, but I'm still struggling as to how to set it up. I just read a site explaining why they require high frequency. It explained a lot, but the author said Tesla Coils are "useless!" I disagree. Thanks for the help! I'll look into this soon!
:woot: <I have no idea what these emoticons are doing, but they look funny. >:grumpy:
 
I get what you meant. By the way, I like the Douglas Adams quote. That's hilarious! I've only been interested in this since summer, so I have a lot to learn. For the longest time I didn't know what an oscillator was, so I kept searching "how to make AC from DC." Thankfully, I figured it out eventually, but I'm still struggling as to how to set it up. I just read a site explaining why they require high frequency. It explained a lot, but the author said Tesla Coils are "useless!" I disagree. Thanks for the help! I'll look into this soon!
:woot: <I have no idea what these emoticons are doing, but they look funny. >:grumpy:

Glad you like the quote! I'm currently employed as a software developer, myself, so I know that no matter how "foolproof" I make my program, there's always someone out there who'll break it :D

Tesla Coils are useless in the sense that they have no practical use. However, I have found them to be a very fun project to design, build, and run. They are very educational, provided the builder knows how to create them safely, and they're fun to watch. Even if it has no practical use, I'd gladly pay ~$50-$100 to build one, provided I had the money to spare ;)
 
Do mosfets require a square wave or other oscillating input in the gate? I guess that is what makes the circuit oscillate, right? Thanks.
 
Do mosfets require a square wave or other oscillating input in the gate? I guess that is what makes the circuit oscillate, right? Thanks.

The mosfets are just transistors, so you can think of them as a switch. You turn on the switch by applying a current to the gate, and turn off the switch to stop the current (this is a generalization, different types operate differently--Whether dealing with N-channel or P-channel). I suggest reading up on FETs in general so you understand how they work.

The signal going into the MOSFET is a square wave produced by your 555 timer. It is on for a period of time, then off, then on again and the cycle repeats. This is what drives the flyback transformer to produce high voltage. The "oscillation" needed to drive the Tesla Coil is done in the capacitor and primary coil. Do you know how LC circuits work? If not it is imperative that you look it up, it is critical for your TC.

Once you can tell me what the capacitor and inductor (primary coil) do together, then I can explain the rest.

Regards,
Matt
 
Also before going too much farther, you should know that your schematic has an error with the mosfet gate. The mosfet at 5V on the gate will be more of a resistor than a switch. The mosfet you chose needs ~10V to fully turn on.
 
Also before going too much farther, you should know that your schematic has an error with the mosfet gate. The mosfet at 5V on the gate will be more of a resistor than a switch. The mosfet you chose needs ~10V to fully turn on.

Good catch!

You'll need a transistor to amplify the signal. You should be able to do this with another transistor (probably not a FET, though).
 
Good catch!

You'll need a transistor to amplify the signal. You should be able to do this with another transistor (probably not a FET, though).
Or use 12V for the 555 supply. The 555 also drops ~2V between input and output. So a better choice might be the 7555.
 
I have no idea when I started this topic. I actually just found it again a couple years later I guess on a Google search. Hm.... Oh well. I'm glad I didn't try some of what I was thinking of doing and researched because I probably would have killed myself by accident! I have found an NST and aborted the solid state for now, at least until I have the money for the components. Maybe I'll follow one of Steve Ward's circuits if I decide to, but for now I'm building bottle capacitors the redneck way and using a spark gap. Hey, Tesla used salt water, too, right? I'd like to thank DerStrom8 for recommending I research before I mess with this stuff. Haha
 
Hi Yergaderga! Nice to see you back in this thread :)

I am happy to hear you have done some more research and are pursuing a "safer" route ("safer" being a relative term). I always recommend that first-time Tesla coil builders stick with SGTCs instead of SSTCs.

In case you're interested, I now have a blog here following my design and build of a Dual Resonant Solid State Tesla Coil (DRSSTC). It's not quite finished, but it should give you an idea of some of what's involved in designing a SSTC:

https://www.electro-tech-online.com/blogs/building-a-dual-resonant-solid-state-tesla-coil.248264/

Regards,
Matt
 
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