Easy SSTC, Slayer Exciter on Steroids!

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Introduction: Easy SSTC, Slayer Exciter on Steroids!

In this instructable, I'll show you how to build a REALLY powerful version of the slayer exciter circuit! This design is powerful enough to be considered an SSTC, or Solid State Tesla Coil! It can throw really hot electrical arcs of plasma over 3 inches long, and has the capability to be modulated! By modulating the circuit with a square wave with a frequency of around 60Hz and 10% duty cycle, you can achieve sparks that look like a small Vacuum tube tesla coil, and also greatly reduce power consumption!

If you prefer to watch my video tutorial, or just see what this thing is capible of, watch the video below:

https://www.youtube.com/watch?v=lPHHvVTVbwM

Step 1: The Schematics & Plans!

Compared to the normal Slayer exciter circuit, this circuit has some major changes. The biggest one that drove the rest of the design was switching out the normal BJT NPN transistor for a MOSFET. I used 2 IRFP250 MOSFETs in parallel to improve the current handling capability and thermal characteristics compared to the comparatively wimpy MJT3055. However, using FETs presented an issue with the gate-drive, as the gate could no longer be driven directly by the feedback. (Most likely due to a impedance-matching issue with the gate acting like a capacitive load) To fix this, I simply used one of the very many DS0026 MOSFET driver inverted buffers I had in the parts bin.

I also added a resonant tank capacitor across the primary to make use of the EMF flyback and help the circuit achieve resonance, and a 10K --- 100K resistor across the input and output pins of the DS0026 to increase stability and reliability of the oscillation. Since the input to the DS0026 is susceptible to the uncontrolled voltage transients from the feedback, I also added a few 1N4148 diodes to shunt voltages that go 0.6V above or below the supply rail. If these are not used, the DS0026 will die within seconds of operation.

Step 2: Choosing a Suitable Power Supply

To power this circuit, there are many limitations on the type of power supply that can be used. For starters, Linear or unregulated power supplies MUST be used. Most modern Switch Mode Power Supplies (SMPS) will often not work as inrush current and other current peaks will cause them to go into foldback current limiting mode, which basically means that they turn the output off most of the way as a form of short circuit protection until you reset power to them or when the load is disconnected. Therefore unless they are modified/hacked, they will not be suitable. and as for the small little wall bricks, FORGET about those. Even the older unregulated transformer based ones are simply not big enough.

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Now to achieve the results I did, you are going to need one beefy power supply. in my video, I used a few heavy transformer based power supplies configured to deliver between 30 and 50V. One of the transformer power supplies used was the 12V 10A beast shown in the picture, and this power supply was in series with another, smaller 12V 4A unregulated power supply, which was in series with yet another 24V 2A transformer. Under no load, I was achieving about 50V. However, under heavy load (peaks as high as 8A), the voltage would sag to 35V. and the smallest transformer would overheat, so I had to figure out how to make the circuit not draw so much current.

My solution was to only power the circuit 10% or so of the time. I did this by using a 555 timer to turn ON and OFF the power to the DS0026 very quickly. A small NPN transistor was connected on the HIGH side of the DS0026 so that the the 555 can directly control the voltage on the supply rail for the DS0026. To power the modulated circuit, you will need at least a 12V 4A power supply, but to achieve the same results as I did in my video, however you will need 50V 2A.

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At voltages higher than 15V, however, you need to consider that you will either need to use separate power supplies with a common ground (it is OK to use a small 12V wall wart for this supply), or use some sort of voltage regulator or buck converter to step main supply voltage down to 12V. I learned the HARD way 4 minutes into the video that a 7812 is NOT suitable to regulate a 50V supply. Killing my one and only 7812, I ended up using a dodgy Zener Diode Shunt Regulator. This solution is not ideal, and certainly not the way I implemented it. Only use this method if you are desperate like I was at the time. Regardless if that is the solution you plan to use, take a look at the last picture for the schematic.

Step 3: Prototype the First Circuit on the Breadboard

There is not a lot to say here, Just build up the circuit on a breadboard, connect the power, and see if it works! If not, troubleshoot and see what is wrong.

I recommend to start working on the power supply section first, in my case, that's building up the Zener diode voltage regulator. Make sure that can deliver 12V or so, and at least 100mA. Using a wall adaptor for this instead is fine, just make sure you pay attention to polarity and that the negative of that supply is connected to the common for the entire circuit. Use a large filter capacitor of least 1000uF as well as some smaller film or ceramic capacitors for better filtering of higher frequency components.

Once you verify the power supply regulation part of the circuit is working, you can move on to building up the DS0026 section and testing it. Once you make it, you can test it by connecting a LED to one of the outputs of the DS0026 and ground (paying attention to the LED polarity) and connect the input of the same buffer to ground and Vcc. The LED should light up when the input is grounded.

Step 4: Optional: Now Add the 555 Interrupter Portion!

Now just modify the circuit by adding the transistor between the power rail for the DS0026 MOSFET inverted buffer driver and the 555 circuitry to drive that transistor. Simple enough, right? (make sure there are no filter capacitors across the DS0026 itself, that defeats the whole purpose of modulating power to it on and off, since the capacitor will just smooth that out. But do keep the capacitors on the power rails themselves.)

Step 5: Testing, Troubleshooting, and Pictures!!!

The golden rule of troubleshooting electronics is Thou Shalt test voltages, according to Dave from the EEVblog! So make sure that the power supply's you are using are healthy and working as they should. Then make sure that the 12V output of the regulator or separate supply is also powering the circuit correctly. If you are using a regulated power supply, make sure you are not triggering some sort of short-circuit or overload protection. Many modern power supplies use foldback current limiting meaning that if the circuit pulls more than a certain amount of current for even a split second, the output voltage will drop to a tiny fraction of what it was before, and stop the functioning of this circuit.

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Triple check all your connections are secure and good, and that you did not goof up anything. If you choose to use slightly different parts, make note of those assumptions and make sure they are not whats causing the problems by trying the parts that I used.

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If you are using the 555 interrupted version of the circuit, make sure that the 555 is oscillating correctly. If you have an oscilloscope and a 10X probe, probe the output of the 555 while power is applied to just it, and make sure that it is in fact oscillating correctly. If you choose to use different parts for this, make sure that you are getting a square wave with a low duty cycle and about 10Hz-500Hz. If not, using a speaker connected to the output of the 555, you should hear some sharp annoying buzzing noise.
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Try reversing the polarity of the primary coil, or the number of turns to see if that makes a difference. Again make sure connections are solid. I have spent over half a day collectively with simple mistakes like these. Even in my video I pointed out in an annotation that the polarity drawn in the picture is wrong! I did not have enough time left over to fix the mistake.

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Make sure the tank capacitor is close to 500pF, do not assume that it is if you do not understand how to read values for capacitors. If the value is too low, the circuit will not work very well and will not give you spectacular results. Similarly if it is too high, then again the circuit will not work very well. There are some defining characteristics of the functioning of the circuit that you can really only learn by practice and building/messing with this circuit yourself.

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If things are still not working, than it is likely you can killed some parts. I would recommend replacing the MOSFET(s), the DS0026, the NPN transistor, and the 555 with new ones, or testing the parts in question to see if they still work. You may find that the DS0026 and the 555 died, as I did at least 10 times in my development of this circuit. It is really easy to let out the magic smoke, but half the time when chips die, they do not show any physical signs of failure.

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Hopefully by now your build is working, and you can achieve the same results as I have! All of the pictures are simply frames of the video, the last one having been modified by overlaying multiple frames to build up the spark density (so it looks more realistic) and reduce noise.

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4 Questions

Thanks for the quick answer ,but i am still confused about the secundary coil . Can you sent me a website or anything just to give me an idea how many turns it should have , what is the diameter of the coil or how thick it should be.

What should be the diameter of the coils and what wire I should use ? And if I have a laptop 20 V power supply could I just use voltage divider to get 12V ?

0

Resistor dividers are a terrible idea. Google Kirchoff's current and voltage law (KCL and KVL.) Also, Thevenin's theorem is also a VERY powerful tool which can help you gain intuition about circuits. This basic electronic theory should answer your question about using resistor dividers as voltage regulators.

The PSU question is more tricky. Oftentimes when subjected to electrically noisy circuits or loads that have a tendency to draw a great deal of inrush current. This will "trip a breaker" internally on the PSU, and it will shut down to protect the device it's powering. This is obviously undesirable when powering an SSTC. A "dumb" transformer and rectifier type power supply, or a nice lab bench power supply (with good voltage regulation and an adjustable compliance current) would be better suited for this task.

Can i use a 48v 8.3amp Switching Power Supply? Would be really Handy since i have it Laying around.

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I am able to use a 48V 2A supply and achieve results close to what was shown here. The important thing is that the supply does not implement foldback current limiting. If it does then what will likely happen is inrush current to the circuit will cause supply to effectively shut down until the load is removed.

Hey,

Why do you use an inverted buffer instead of just a regular buffer?

Thanks

0

Because it was the convenient MOSFET driver chip I had available. I do not recommend anyone building this project to use this obsolete part. Its hard to source and expensive. You can replace it with a push-pull arrangement of BJTs which performs essentially the same function. (It amplifies current greatly and makes the impedance of the MOSFET gate appear 1+ beta times bigger. (Beta being the current gain of the transistors, which sbould be about 50 to 300)

89 Comments

Hi Max,
How do I make that thing musical? I wanted to play music or use a funktion generator app to tune the frequency but i have no clue how to do that :( can u pls help me with that?

1 reply

Look at electroboom's videos

user

What can i use instead of ds0026?? Can u give me some models please?

followed your instructions to the letter and all that happened was the fist cap blew and there doesn't seem to be any power actually going to the coil could you tell me where i could have possibly went wrong?

1 reply

What is your depth of knowledge with electricity and electronics? This circuit although it looks simple on paper, it is actually amazingly difficult to get it to work well without really understanding how it works, how to optimize it, etc. You might want to head over to youtube and brush up on some electronics tutorials. I myself have posted a couple totalling 30 minutes. Here is a short list of some things I feel would benefit you:

* voltage / current / power / resistance / energy / ohms law / watts law,

* complex impedance of capacitors and inductors

* the concept of resonant or natural frequency

* Parasitic properties of components and construction methods (like different coil designs and such)

That is a lot, I hope it does not discourage you.

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"following my instructions to the letter" is actually not going to get you far with this very fiddly circuit. although that should honestly get you a working result. What assumptions did you make? Any substituted components? I need details to give you better advice.

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I assume you blew a capacitor which occurs when it is overloaded (more current through it that it's ratining would allow) or overvolted (you exceeded the Working voltage or WV rating of the capacitor) or got the polarity backward (if it's an electrolytic: the shittiest type of capacitor)

hi max what ca i use instead of a 555 transister?

1 reply

Assuming that you are referring to the popular astable multivibrator configuration; Only if you:

a) Get one that can oscillate well into the hundreds or thousands of KHz, depending on the construction of the secondary coil and topload (CMOS variants are faster I believe, but you need to take care with the construction to avoid parasitic loading effects on the output of the 555 timer and buffer the output with additional BJT buffer drivers.)

b) Are willing to precisely tune it to the resonant frequency of the secondary (the oscillation frequency of the 555 as well as the resonant frequency of the LC tank circuit between the primary and capacitors directly in parallel with it. And It's hard enough to tune one thing manually.

~OR~ develop a custom 555 circuit that utilizes feedback to create a oscillator that can track the resonant frequency of the secondary LC system.

Ow, ok thanks MAX ;D

for its power supply I used 5 ampere 15 v does not spoil everything ?? and whether they are efficient if I use the 5 ampere ??

1 reply

I think you might benifit from watching my 2 Tutorial Tuesday videos to get a better grasp on voltage and current.

In short, when you use a low impedance source (where the output voltage does not sag much with increasing current draw) then the load gets to decide the current draw.

The slayer exciter will draw more current when you apply more voltage to the input, and the power consumption increases substantally. You may find that your circuit attempts to draw greater than 5A, and your power supply may decrease the output voltage to almost nothing to protect itself. Depends on the supply.

Can I use 12 v ATX PSU to power this stuff up

My MOSFETs get very hot in the first few seconds of running, so i just unplug the power supply. I'm using 2 paralleld IRFP450s. What should i do?

1 reply

You should totally refer to my youtube tutorial and ask there! ;)

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jk. Assuming you tried everything in the tutorial section (DO THIS PLEASE) then there is a good chance your MOSFETs are dead or your driver is dead. Build up a basic test circuits and troubleshoot each component. Silicon tends to fail easily, so diodes, transistors, chips, etc.

Plenty of tutorials of how to test transistors and MOSFETs, The DS0026 or equivalent chip should produce an inverted output on an osciloscope compared to the input. The output should be able to drive a load with static voltages present on the input.

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You should have a read through this to understand why parallel MOSFETs is NOT a good idea if you don't know what you're doing.

http://www.irf.com/technical-info/appnotes/an-941....

Basically the gist is that because no 2 MOSFETs are identical, one will conduct way more current than the other when ON and especially in the linear region of operation. You need current sharing resistors on their drain and gate for reasons explained in that application note.

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p.s. If you plan to do much more electronics you gotta learn to read up on this stuff! It can get intense, I know. Look into picking up a copy of the Art of Electronics. It has almost everything you would need to know in it!

Great project! Actually, I have attempted to do this project once before, but the problem was the power supply. I would like to avoid buying a commercial power supply, and would much rather build one myself. Can I just use a few large, salvaged transformers?

Could I use an FGH60N60SMD IGBT instead of the IRFP250N mosfet?

What are the measures of the coil? and what is the thickness of the copper wire around it? I would also like to know what you used to the top. Thank you very much for the tutorial!

Hey Max,

Finally getting round to this circuit - brute power supply it is! those other ones I've been messing with are fine for smaller normal circuits but the slayer circuit has let smoke out of four psu circuits now, interestingly, the old workhorse psu i originally used is still cruising along at 25VDC but i'm moving on. I built full bridge rectifier and will use that on the hi voltage side, only problem(?) is I have 73VDC at the output. I have IRF540N MOSFETs, do you think these will be ok? I think they're ok for 100V but not sure about the driver chip getting excess feedback voltage given that i have 73VDC feeding it. Should i increase the value of R3 or will that still be ok do you think?

Just re-watched your video of this thing, OMG the sound it makes when the interrupter is added to it is just awesome! Sounds like such a beast, I can't wait to get this going :)

3 replies

Thanks! :)

No, IRFP540 MOSFETs are not close to good enough. :( This circuit will kill IRFP250N transistors at half that voltage. Consider picking up a few FDP33N25 MOSFETs, they are similarly spec'ed to the IRFP250N but half the cost at reputable electronic distributors like mouser or digikey (about $1.44 @ Mouser in 10's)

You have to remember when driving inductive loads like the primary of the tesla coil that you will get high voltage kickback that can be orders of magnitude greater than the supply voltage. My 24V flyback driver has up to 400V back EMF transient spikes on it without methods employed for snubbing.

Hopefully you don't plan on using a zener diode voltage regulator to take 70V down to 12V, cause that would be very VERY inefficient, and quite dumb, really. Might as well use an oven heating element for the resistor and zener diodes the size of bolts mounted on a car radiator for cooling, or you use a proper switching regulator. Any 12V wall adaptor would work.

I determined R3 experimentally, I do not know how it's value should change with respect to input voltage. Really when developing the circuit I found literally any value between 1 megaohm and 1k worked. I do not think it is that critical. It simply offers a slight bit of negative feedback which slightly reduces the gain I think.

Cool, I'll look into some of those, cheers for that. Will they handle 73VDC in your opinion? Are there any bigger or better ones you know of that would suit given the extra volts? If it means spending a little bit extra, and using extras in parallel so it doesn't go pop i'm thinking it's probably worth it, wife always gets upset with me when circuits explode or make flames on the kitchen bench, and there's been a couple lately :)

Yeah definitely wasn't planning on doing that, got a separate psu for the 12v side, I think is good for 2A, (not that it'll need that much but is nice little DC brick power pack so should be ok for the low side, wired it into my big power supply so is able to be one wall plug)

Do you think 73VDC is too much? The transformer is supposed to be 50V but i suspect its rating might be at 230V (and here it can be anywhere from 230VAC-250VAC at the wall and i have 250V at this place). I lived at place where it was 225V a few years back, just depends on the area. but i'm guessing (without doing the calculations) thats where the extra is coming from, the reason i bought that one was because it was big 3A or 6A if you use both outputs in parallel and 50V! (and on special) lol turns out I got a bonus model i guess haha :) now left wondering if it's too much.

I was gonna test the high voltage side on my trusty old 25VDC psu first before throwing the other one at it just in case anything goes wrong anyway just to be safe and to not blow it up :) so if all else fails i'll still be able to run it, just not at it's full potential

Let me guess: It is rated for a output of 50V AC, I can tell you that it is indeed very close to that, and is actually 51.6Vac, well within 5% tolerance. I will let you figure out why the rectified output is considerably higher. (hint: RMS vs peak voltage. Google that one.)