tesla coil with 555 timer troubleshooting help

[toonamo]

I attempted to build a tesla coil with a 555 timer but seemed to have failed some where.

Perhaps you could take a look and give me some hints on what to try in order to make it work. I attached some pictures as well.

I made the secondary coil on a 1/2 (.875 OD) pvc pipe with a 10 to 1 ratio (8.75 inches tall) with 28 gauge Magnetic wire.
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The primary i only free handed it, and perhaps that's where i went wrong, but did 9 large coils slowly geting larger as it went up.
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I made a 555 timer based schematics found at tacashi.tripod.com. I tested battery voltage when on (drops from 12 to 11). I didn't get any voltage comeing out though. Is it possible i reversed the source and drain? The trainsiter gets really hot in the few seconds i run voltage. I am not sure how to test the square wave so i don't really know.
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To be honest i am not 100% positive i installed the transistor properly either. I looked up npn mosfet transitors and read about the source gate and drain and attempted to figure out what E C B stood for.

Here are more angles of the board
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Here is the schematic is used
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[DerStrom8]

I see many problems, but the first I see is that you don't have a transformer! A standard Tesla coil requires a high voltage ( greater than 7,000 volts) in order to run. You also need a spark gap and a high voltage tank capacitor. Once you find those and get it to the point where the transformer is sparking, I'll continue with things like the wire diameter, winding height, coupling, tuning, etc.

 

[toonamo]

I am tring to get a dc source with a square wave using a 555 timer with a MOSFET transistor to up the voltage. I just need to double check the transistor and get some tips one the coils.

 

[DerStrom8]

I am tring to get a dc source with a square wave using a 555 timer with a MOSFET transistor to up the voltage. I just need to double check the transistor and get some tips one the coils.

Yes, the 555 will give you a DC square wave, but a MOSFET does not "up the voltage". It is only a switch. Also, what you have (the NTE331) is not a MOSFET. It is a bipolar transistor (current-controlled, not voltage controlled like a MOSFET). Anyway, you can use a transistor to connect a higher voltage (absolute maximum of 100v according to the NTE331 datasheet, though you should keep it well under that), but that is nowhere near enough to drive a Tesla coil. You need over 7000 volts, because (assuming you're building a regular SGTC) you'll need a spark gap. Tesla coils run on the theory of resonance, which is achieved by connecting a capacitor to an inductor (primary coil). But you need there to be a very high voltage on the primary in order to have good power transfer from the primary to the secondary. You're missing your entire tank circuit, which is absolutely critical for a proper Tesla coil to operate. You CAN NOT run a Tesla coil from a simple square wave. You need a very high voltage, high frequency, alternating current, which you get using a high voltage transformer (such as an ignition coil from a car or flyback transformer from a CRT TV), high voltage capacitor, and spark gap. Without these things, set up properly, and tuned properly, your Tesla coil WILL NOT WORK. Period.

 

[shortbus=]

You CAN NOT run a Tesla coil from a simple square wave. You need a very high voltage, high frequency, alternating current, which you get using a high voltage transformer (such as an ignition coil from a car or flyback transformer from a CRT TV), high voltage capacitor, and spark gap. Without these things, set up properly, and tuned properly, your Tesla coil WILL NOT WORK. Period.

But, they did it on YouTube.

 

[DerStrom8]

But, they did it on YouTube.

They also made a perpetual motion generator using a cat and a piece of buttered toast

 

[jpanhalt]

I see many problems, but the first I see is that you don't have a transformer! A standard Tesla coil requires a high voltage ( greater than 7,000 volts) in order to run. You also need a spark gap and a high voltage tank capacitor. Once you find those and get it to the point where the transformer is sparking, I'll continue with things like the wire diameter, winding height, coupling, tuning, etc.

Not all of them require an HV transformer and spark gap: https://www.electro-tech-online.com/custompdfs/2012/06/sstc10_manualrev3.pdf

I hope toonamo will post his schematic so we can better address the failure points.

John

 

[DerStrom8]

Not all of them require an HV transformer and spark gap: https://www.electro-tech-online.com/custompdfs/2012/06/sstc10_manualrev3.pdf

That's why I specified "standard" Tesla coil, which I defined earlier as a "spark gap tesla coil"

I hope toonamo will post his schematic so we can better address the failure points.

Yes, that would help. I'm just starting with the very basics, because there are so many things wrong with this setup I figured once he gets all the necessary parts, THEN we'll talk about what goes where

 

[cr0sh]

Should we (ok, "you" - I have no experience with Tesla coils or HV) be giving advice on how to build such a device with potentially lethal voltages to someone who is clearly out of their element (and possibly needing to learn the basics first)...?

 

[DerStrom8]

Should we (ok, "you" - I have no experience with Tesla coils or HV) be giving advice on how to build such a device with potentially lethal voltages to someone who is clearly out of their element (and possibly needing to learn the basics first)...?

You know, that's a question I come across a lot, as I tend to gravitate towards Tesla coil projects and other high-voltage devices (what can I say? It's in my nature ). The decision I've come to is that if we (the people with knowledge) don't help him, he's going to try to do it anyway, quite possibly with bad information. I think that would be far more dangerous than helping him do it the RIGHT way. Wouldn't you agree?

 

[cr0sh]

You know, that's a question I come across a lot, as I tend to gravitate towards Tesla coil projects and other high-voltage devices (what can I say? It's in my nature ). The decision I've come to is that if we (the people with knowledge) don't help him, he's going to try to do it anyway, quite possibly with bad information. I think that would be far more dangerous than helping him do it the RIGHT way. Wouldn't you agree?

Point taken; do you consider Tesla coils to be a safer HV project than other, potentially simpler-to-build HV projects (Jacob's Ladder, spark coils, etc) that could be encouraged to study first?

To me (again, no experience with HV - other than getting zapped by a running automobile's spark coil once at Burning Man), a Tesla coil seems like an advanced project, something that should be worked up toward by studying lower principles (spark coils, voltage doublers/triplers, resonant circuits, etc) - not something to be done "first". If I were wanting to build a Tesla coil, that is how I would approach things; this is how I approach most things in life, by studying the first/lower principles and creating a base knowledge set - so that I will have a better understanding for my ultimate goal (including the dangers and safety measures I should take to mitigate problems).

I guess that's just the "scientist/engineer" part of me (well, that and self-preservation)...

 

[DerStrom8]

Point taken; do you consider Tesla coils to be a safer HV project than other, potentially simpler-to-build HV projects (Jacob's Ladder, spark coils, etc) that could be encouraged to study first?

To me (again, no experience with HV - other than getting zapped by a running automobile's spark coil once at Burning Man), a Tesla coil seems like an advanced project, something that should be worked up toward by studying lower principles (spark coils, voltage doublers/triplers, resonant circuits, etc) - not something to be done "first". If I were wanting to build a Tesla coil, that is how I would approach things; this is how I approach most things in life, by studying the first/lower principles and creating a base knowledge set - so that I will have a better understanding for my ultimate goal (including the dangers and safety measures I should take to mitigate problems).

I guess that's just the "scientist/engineer" part of me (well, that and self-preservation)...

Normally I would agree with you completely--that a Tesla coil should be studied extensively, worked up toward, and should be a project for a more experienced person. However, it so happens that a Tesla coil was my very first project as well I built one even before I learned how to use a 555 timer, so I know how some of these guys feel

 

[jpanhalt]

Normally I would agree with you completely--that a Tesla coil should be studied extensively, worked up toward, and should be a project for a more experienced person. However, it so happens that a Tesla coil was my very first project as well I built one even before I learned how to use a 555 timer, so I know how some of these guys feel

I built one way before there were 555 timers -- used a broken fluorescent light bulb for the HV coil form. In those days, one could buy mercury at the local drug store. Miraculously, I survived.

The safety issue keeps going round and round. The problem is, there is nothing that is fool proof. I like the openness here rather than some crazy fuzzy rules that are applied inconsistently and capriciously.

Leave it to individual judgement. If one is in the United States, he might might consider being more circumspect about explaining how to do something to a fellow American than, for example, someone in Japan or GB.

John

 

[tcmtech]

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[trash]

The decision I've come to is that if we (the people with knowledge) don't help him, he's going to try to do it anyway, quite possibly with bad information. I think that would be far more dangerous than helping him do it the RIGHT way.

Damn Straight !

I see the full spectrum of questions as well. Some people it is clear do not have a clue and will not progress past rubbing two sticks together to create fire.
There are some who of course will become arsonists when you do whether you help them or not.

Anyhow, there are a whole range of high voltage generators that are safe to build and operate even for the most complete novice.
One of my favourites is a Kelvin generator.

With tesla coils there is a lot to learn. Starting small and simple is the way to go.
Obviously anybody playing with a tesla coil should be aware that you can get seriously hurt and some points in the circuit contact with them can be lethal.
Just be aware that as a newbie, you're in the deep end without floaties so your own safety is your own concern and it should be priority.

The rest of us will give you enough information to make the next step as you learn what you need to get to each step.

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Tesla coils are more than just a transformer. Like a radio they are a tuned circuit.
There are many ways to run a tesla coil, but like the other guys that have suggested the simple methods are often the best.

A high voltage circuit which generates a spark is the simplest method, and it is not much different from a circuit one would use to run a jacobs ladder.
This is where a lot of your experimenting should begin. You want to be able to generate a spark which you can control and adjust the striking rate.
The simplest is to just have a spark gap which you can adjust with a screw. Another is to have a spark wheel which the spin rate can be adjusted.

I've seen many different ways to generate the voltage required for the spark. Ordinary power transformers used as isolation transformers and run above their primary voltage rating. There's obviously a little bit of an overhead, but I have seen that combination flash over.
Two microwave oven HV transformers used back to back. Damn scary but one of the best generators I've seen operated.
Walton-cockcroft multiplier is another I've seen used and of course TV flyback transformers, neon transformers, ignition coils and my personal favourite, the photocopier HV transformer.

The primary and secondary coils of the tesla coil look ok to start with. You'll refine them yourself later.
I'm not sure what that wire is coming down from the top of the secondary coil, you want to keep that end of the coil as much as an open circuit as possible.
Which then I have to ask, where the hell is the (supposedly) grounded end of the coil going ?

Think of a what I said about a tuned radio circuit. Open coils and sloppy wiring are not good RF practice, even if it is 500KHz.
While you might not have a nice dome for the top of your coil, you can still scrunch up some aluminium foil and sit it on top of the coil former with the wire tucked in under it. At least a fine high tension wire won't be flicking around trying to grab anything at ground potential.

Another thing to consider is the HV capacitor. A lot of coils I've seen running use a fixed value capacitor. I prefer to build mine so it is tunable.
My first coil was not much different from yours, but smaller. About 30cm tall and I used a TV flyback transformer. I learnt a lot on how to get a tesla coil to work. It used a fixed capacitor and an adjustable spark gap made from some tin cans nailed to the wood base. It would throw sparks about 5cm.

Tesla coils are addictive. If you build a small one, you always want to build something bigger !
My second coil was about double the size of the first. 60cm and before I tuned it the sparks were about 10cm long. I was really unimpressed and I did some careful reading (in the days before internet) down the local library. Used a small variable capacitor from an old valve radio. I had to make some modifications to it removing some of the plates so it wouldn't flash over. I also added more fixed capacitance in parallel to get a value close to what I wanted.
I tuned the coil with it running, and that moment of clarity came when it was sitting on the bench and a spark about 40cm long jumped off the top of the coil and stuck me fair and square on the forehead. I had that moment of clarity with the bright white flash which I saw not with my eyes !
It was something like god saying, "Congratulations idiot ! you got it right !" Later I used a photocopier transformer and there was no way I was going to be struck by it with that thing running it.

Lucky it was only a small coil. My third coil was not built well and was a failure. It worked, and I learnt a lot from it, but it wasn't any better than the second.
The fourth was over a metre tall. It was a brute. It wasn't so much about the coil, but more about what I could do with it. That kind of vandalism I'll leave for somebody else to discover on their own.

My last coil was also a failure. I have not attempted to build one since. It was 2.3 metres tall. I was using a cardboard former which I had wrapped in duct tape. (I was trying to avoid PVC). The coil only worked for a short time before it set fire to the cardboard. I didn't try to get it running after that. I gave the coils to a friend who also set fire to it. He later rewound the coil on a new plastic former.


I can think of reasons why I would not use the 555 circuit you're using. But then at a later stage after I had worked out some simple basics I would consider going back to it with what you have learned from ye olde tesla coil circuit.

 

[tcmtech]

The thing is when designing a proper Tesla coil there are a lot of calculations that have to be made and they all relate to what ends up being a very specific coil design that has to have the exact right length of wire and the exact resonance to hit the frequency that has a wavelength exactly 4 times the length of that wire as well and that has to be done for both the primary and secondary coils.


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[audioguru]

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