Building the poor-mans mini tesla coil ( slayer exciter)

Picture of building the poor-mans mini tesla coil ( slayer exciter)

A slayer exciter is basically a small solid state tesla coil, usually a one transistor design. The circuitry for it is simple. One of the first things anyone who has built a joule thief will notice, is that the circuitry is very similar. The biggest difference is that the small transformer or inductor has been replaced with a primary/secondary tesla coil configuration, and that the feedback is capacitively coupled. (There is a good abount of capacitance between the 'top' of the coil, and ground.)

There are many awesome thing these exciters can do!
they can:


  • neon lights!-----------------------------------------(several feet away)
  • florescent tubes!----------------------------------(within about a foot)
  • CFL's!-----------------------------------------------(within about a foot)
  • EL wire---------------(it does not work well for me. If anyone tries it, please tell me your results!)
  • LED's!-----------------------------------------------(across the room if done right)
  • and even small incandescent lights! -------(with an L3 coil)
  • paper with pencil markings -------------------(before it catches fire!)

Burn and ignite:

  • candles
  • wood (pencils)
  • human flesh (now my fingers smell burnt)
  • paper


  • crappy / half dead LED's
  • bacteria
  • sensitive electronic equipment (phones, computers, SD cards, CD's, blu rays, flash drives)
  • someone else's stuff


  • ion wind motors
  • the coolest lantern or light on earth
  • fires
  • plasma cutter

►Make following electronic equipment go crazy:

  • calculators
  • watches
  • digital clocks and alarms
  • devices with capacitive touchscreens (PlayStation VIVA, smartphones, feature phones, tablets)
  • UHF remotes

Transmit wacky sounds (loads of EMI) to:

  • AM radio
  • FM radio
  • shortwave radio
  • HAM radios possibly
  • TV interference

Here is how to make a my version of the more powerful exciter (These videos were made awhile after this intructable, so the only issue with it is thermal management.) Please do not get the instructions in this video confused with the instructions for the later TO-92 one in the further steps. Different bias resistor values should be used for either of these 2 versons.

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JasonP17 made it!1 month ago

Well Took me a minute to get it right and tuned, but my 1st Slayer exciter ..

Wrapped on a CD spindle,#30awg wire 250t s, 5t p .. 9v battery setup.. (not very powerful but works..)

#2 / 3 & 4 all work well with this circuit.

using 3 TIP29c transistors (had them in my box) paralleled

#2 ~~ #30awg wire, 540t s, 3t flat spiral primary, 1.5" former

#3 ~~ #30awg wire 720t s, 4t primary (horizontal setup for playing with Tesla's magnifying transmitter setup). 1.5" former

#4 ~~ #40 awg wire (complete pain in the arse to wind without errors)

2000t secondary, 20t primary Bifilar wound, 1.5" former.

#5 ~~ #40awg wire 750t s, 8t primary, 3" former..

I gave #1 to my nephew (10y/o) to play with and get excited as it only runs on batteries.

Overall, good tutorial! I really want to throw sparks though... I made the fat one into a sgtc, would not breakout on its own but 4" lightning when getting ground probe close to topload breakout point .. :/


Also for those looking for small easy toploads, Soda cans work well, and can be taped together for larger loads..

-max- (author)  JasonP171 month ago

If you REALLY want to throw some large sparks of at least 4 inches, and avoid the noisy SGTC, I recommend this circuit, if you have the parts already laying around.

This is actually where the development of the original slayer exciter circuit has led me. I initially replaced the NPN transistor with a MOSFET, since they are better suited for switching applications*, and it was in a easy package type (TO-247) to mount, and already mounted to a large heatsink. I suspect because the input has some significant enough input capacitance, has a really high input impedance, and since MOSFETs need a relatively high gate voltage to turn on, the standard circuit didn't work.

My next thought was to use a comparator as a buffer, but I did not have any of those, then I found some even better dedicated MOSFET driver chips, designed for that very purpose! I used the DS0026, which is what I had on-hand! Some messing around to make the oscillation stable and strong, I came up with the first design below in the pictures. I was able to power this without issue up to 50V.

In the 2nd version, I simply added a "interrupter" to PWM the power rail of the DS0026 so that way the RMS power draw was less, and since I am no longer loaded down my transformer, the voltage has risen to 40-50V across the power rails. Consequently when the circuit kicks on and runs for the short duration, I get incredible arc length!!!!!

The interrupter that I choose was simple a astable 555 since practically that is the easiest oscillator for me to make work and breadboard up quickly. I'm driving an emitter follower transistor which turns on and off the DS0026 which in turn mean that the circuit only works 10-20% of the time, allowing some down time for the capacitor to charge back up and gives the small poor transformer and MOSFET a break. The duty cycle is of course 10-20%, while the frequicy is about 10Hz-100Hz depending on the capacitor.

Solid State Tesla Coil Slayer Exciter rev 2.pngSolid State Tesla Coil Slayer Exciter.png

i bought all the parts and im going to start building now. its going to be powered off 170 vdc, so i should have a 10 inch spark.

-max- (author)  PlasmaGuy10122 days ago

170V!? I barely had any success at 50V. I predict that this circuit will just blow up everything and possibly blow a circuit breaker. Start at 12V for this circuit and work your way up to 24V, 36V, 48V, etc.

At voltages higher than 36V, you will NEED to replace the "12V regulator" made with a zener diode and some resistors with a switch-mode regulator or DC to DC converter. Also you will NEED to get much higher power transistors, I have blown all of my IRFP250's, so my plans for making a video of the circuit are delayed.

ok, i have a big 21-42 volt 5amp psu that i can power it with. the irfp250 is rated at 200v so why won't it work at 170vdc?

-max- (author)  PlasmaGuy10121 days ago

Is the PSU a SMPS (Switch Mode Power Supply)? one of the lighter smaller ones (with tons of circuitry and lots of small transformers, inductors, and capacitors) Or is it a linear type (the simple kind usually made up of one huge heavy iron core transformer and a few diodes and huge capacitors.)?

You may run into issues with "foldback current limiting" and "short-circuit protection" sh*t kicking in and abruptly causing the output of the power supply to shut off. I have been using a modified (hacked) xbox power supply which is a SMPS but all that protection has been bypassed with some mod wires.

its just a huge 42v transformer with a rectifier and 65v 33000uf smoothing capacitor

-max- (author)  PlasmaGuy10119 days ago

Good! You shouldn't have any issues with it! With that you should be able to get very similar results to me. What chip are you using as a substitute for the DS0026?

how long is you arc?

the mc33151pg, it's a direct replacement for the ds0026

i know, when i draw an arc off my normal exciter for too long the 30v smps will shut down.

-max- (author)  PlasmaGuy10121 days ago

Questions like that make me feel you are going to struggle a bit with getting this to work and will burn out quite a few parts, but I do wish you the best of luck. You should look into some theory of inductors and how the voltage across them relates to the current through them and such before you start building and debugging the circuit. Watch these videos:

Long story short, you need to make sure that the inductive spiking does not destroy the transistor. If it is in its OFF state, and the current that is attempting to continue to flow will need a path to go somewhere, otherwise the voltage will rise up and up and up until it forces it's way through the circuit somewhere. You need to prevent this from happening, and I found that using a capacitor can help with this. The solution in the above videos is not suitable as it will greatly diminish the output of the coil and greatly reduce efficiency.

I plan to make a similar video soon once I learn more of the math (or at least familiarize myself with it) and stuff, (like maxwell's equations etc.)

i forgot about inductive reactance. can't i just put a reversed diode in parallel with the drain and source of the FET?

if you look at the irfp250 datasheet you'll see the fet has a built-in diode

-max- (author)  PlasmaGuy10119 days ago

You can, it will severely limit the performance at <50V. However, at low voltages, we use that reactance to our advantage with a resonant capacitor (C1) to allow high voltage ringing on the primary, which translates to really super high voltages on the secondary, which is what we want. However, at 170V, I suppose we no longer need to rely on that ringing to get those high voltages, However, I have not tested the circuit on such a high voltage supply.

I would recommend using at least a IRFP460 or better and calculating the correct capacitor to use for C1. There are tesla coil calculators online to make it much simpler.

oh BTW im not using an interrupter

-max- (author)  PlasmaGuy10121 days ago

Then 5A may not be enough to power the circuit above 30 or so volts, it may be demanding more. My reason for the interupter is that it gives it a tesla-coil like output, much longer sparks, and significantly reduces current draw.

-max- (author)  JasonP171 month ago
Nice output!
JasonP17 -max-1 month ago

thanks.. I have a nice 8" tall aluminum sugar jar I use as topload to extend my range with the 2kt coil.. I get about 2ft with cfl, I can also open Outlook express on my pc from 10ft at certain spark lengths... lol..

I was also thinking of a Mosfet approach, I have a ton of logic lvl 900v fast switchers.. gth 2-5v most came from pc psu's, as well as all the shotsky diodes.

How do you think a 2SK2611 or 2SK2749 would do? They perform rather well with a ZVS setup on flyback limited with 3.1v zener. Maybe I'll try to drive them via 555 since they are logic lvl.. I try not to buy parts but recycle from craigslist items, ie: tv's, printers etc...

2SK2749 : RDS: 1.6ohm, VDSS 900v, VDGR 900v, Vth 2min 4max ..

150w dis.

2611 is very similar lower rds : 1.1

Only thing I dont have is a fet driver .. I wonder how hard it would be to try and incorporate a zvs mechanism, as they are extremely efficient..

-max- (author)  JasonP171 month ago

I was not able to get any reasonable output with a ZVS driver I think because it is too slow of an oscillator, if that's possible. I will maybe give it another try some day, but we need an oscillator that can work well into the MHz. The standard ZVS circuit I see is generally in the 15-60 KHz range, perfect for large ferrite transformers.

SKtesla9 days ago

Thanks for the great instructable max! I got my exciter working and I can get a consistent arc without a top load. With a top load on I am able to draw arcs as well as light a CFL. When I tried to light an incandescent, I was able to see a small arc from the filament but it is nowhere near as impressive as your video.

This is my setup:


12V 5A power supply

1K pullup resistor.

100nF 500V ceramic caps (2 in parallel)

4 turn primary and a big secondary.

I wanted to ask how I can up the power on this coil. Also, could you please put up an Instructable on making the MOSFET version? I'm already looking for bigger sparks! :D

-max- (author)  SKtesla9 days ago
When I perfect my MOSFET version, I will make a video instead. I like the video format better. I just bought some another pack of 10 brand new shiny IRFP250N MOSFETs to burn though while prototyping.

To up the power, use the TIP3055 connected to a huge fan-cooled heatsink, use some large film capacitors or MKP capacitors (around 1uF or more) as well as some electrolytic 1000uF or more all in parallel with the power supply, and have the connections between the all the points in the circuit as small as possible. Alligator clips are not the best, they are a little too long.

Adding a really low value (10's of picofarads) high voltage ceramic or similar capacitor across the coil and adjusting the value of it as well as the turns ratio of the primary is needed to get the best performance. Getting this right is critical. Too much capacitance and too many turns and your circuit may not work at all. Too few and it will not be very powerful.

Cranking up the voltage to 24V will also make the output WAY more powerful, at the cost of using a LOT more power and greatly increasing the chance of killing the transistor.
SKtesla -max-9 days ago

Thanks a lot. I am looking forward to seeing the video soon

I have ordered a 5-pack of MJE3055Ts. I will try them out before going for the TIP3055. How do these two compare in your experience? I also have a 2N3055 I can try though I don't like the TO-3 package. I don't have a heatsink yet so I've been running the exciter for very short durations since the transistors get really hot. I will be buying a heat sink along with a barrel jack so I can wire everything neatly on perfboard. What do you think of this heatsink. Too small? I will get some caps while I'm at it and try what you suggested. I don't have a 24V supply on hand now, I will buy one if it seems necessary.

I was also curious, is it possible to audio modulate the slayer exciter? Also, does the MOSFET version provide superior performance even at 12V? I am working on a proper SSTC but I want to run this with my current setup meanwhile. I only have a 12V power supply now though.

-max- (author)  SKtesla5 days ago

I can't really tell if the MOSFET is much better or not, the performance of the circuit really depends on how well it is tuned, there are many variables that determine whether or not it is tuned, including how close things like your hand are to the circuit. In general though, yes. I want to say it is also more efficient, but I have no quantitative or measured evidence.

The most obvious way to modulate such circuits would be to modulate the voltage of the supply rails. The difficulty of doing so will vary depending on what power supply you choose. This might be easy with a simple linear voltage regulator by interfering with the negative feedback loop injecting audio "noise" to it. On my ZVS driver, I audio modulated it by adding a lot of turns of wire to the big inductor in series with the primary, and injected audio into that forcing the voltage to the circuit to be modulated.

ElectroBOOM has a much better schematic that already supports such modulation in a much more integrated manner.

SKtesla -max-5 days ago

Thanks. I will look for a bigger heat sink. I am collecting the parts to build a SSTC based on Steve Ward's SSTC 5 or the Kaizer SSTC 2. I will be able to modulate that. I have seen the ElectroBOOM one (love his videos) but the parts used are not easily available for me. BTW, do you know of any good source of 30AWG magnet wire with international shipping? EBay doesn't seem to have any options.

-max- (author)  SKtesla5 days ago

I bought my wire from eBay, so I really can't tell you much in regard of buying wire. Others often salvage wire from large transformers and even motors.

-max- (author)  SKtesla5 days ago

Yes, that heatsink is way t0o small if you want tesla coil results (one inch arcs or longer.) You basically need a CPU heatsink, and a way to mount the transistors firmly. I now use a heatsink ripped out of an old Xbox rather than the one used in my old slayer exciter video. You can see the size of the heatsink in my more recent flyback transformer video. If you want one about as powerful as the TO92 version (in the 'able with 3 2N3904's in parallel), then the heatsink you found online is plentyful.

Djnix12 days ago

I have a question, Im trying to build your mosfet driven one, but when i turn it on, it barely does anything. The most I can get out of it is lighting up a small part of a florescent bulb. The transistor also heats up rapidly. What do I do?!

-max- (author)  Djnix5 days ago

Make sure you built it correctly, and spend many weekends tuning it, playing with the number of turns, the resonant capacitor value, etc. Try removing the resonant capacitor and slowly increase the pF rating of it. A variable capacitor would be nice way to do this. Otherwise many large ceramic low value capacitors in series work well.

If you want less vague advice, can you give me more details about you're construction?

pjkim9 days ago

Two questions: First is why this circuit doesn't have a flyback or snubber diode. A diode is usually (always?) required when switching any significant inductive load to protect the collector voltage from going too high and damaging the transistor.

Second, why two LEDs on the base? I can understand the need for a diode to prevent large negative voltage swings, but what is the purpose of two LED drops, ~3 to 4 volts?

-max- (author)  pjkim5 days ago

The 2 LEDs are not necessary, either. At least not with the 2N3055 version. Often what is used is 2 normal diodes, each with a drop of 0.6V, so -1.2V of reverse polarity protection. I just went ahead and used 2 white LEDs instead not really considering the difference of the voltage drops of them. I find that the LEDs are actually not going much, and often just burn out shortly with such abuse.

-max- (author)  pjkim5 days ago

Honestly I am not sure. The common SEC circuits I found online rarely include one, and I have not had issues without using one on the NPN based circuit here, so inductive kickback does not seem to be a major issue. Using something like a TVS diode would certainly be a good idea though.

That said, with my modern design using MOSFETs, I did find that relatively high voltage FETs were needed to prevent kickback, and I also ended up using some resonant tank capacitors in series with the primary. These seem to serve 2 purposes: It allows the coil to resonate, thus creating a considerably stronger output, and it limits the maximum voltage transients as the voltage gets spread out over time.

i8051 month ago

hey max

i have read and watched your wonderful indestructible many times

i have a problem. I've been working now for days but haven't figured it out

the circuit works fine with a signal transistor like bc337 h945 (6AA=7.5,weak cells)

but when i replace it with a power transistor for more power it just refuse to work

when i crank the bias resistor(lower it) the transistor get's hotter and hotter but the led stays off(different power source 5V/12A,12V/3A/ from a psu)

the power transistors are d13007k ,c4242,5027s,i pulled them of a computer power supply i've checked them all in a simple led circuit they all made the led lit with a bias resistor

i can't get ANY salvaged transistors to work, its really strange. i found a TIP42c PNP in a fan speed controller, to use pnp transistors you just have to reverse the power supply.

-max- (author)  PlasmaGuy10121 days ago
I also have a lot of trouble with getting savaged transistors. That is why I recommend buying them instead. They are not that expensive, and you have a much higher level of confidence that they work. if you are really inso salvaging transistors, look into building a transistor-tester project, or buying one on eBay or something. They used to be super common, when transistors were very very expensive. Now no one wants them and you can pick them up pretty cheap. I literally got one for $0.50 (absolutely nothing) at an auction!
-max- (author)  i8051 month ago

Weird, maybe recheck the pinout of your specific transistor in the datasheet, the pinout between different package styles (TO-92 vs TO-220) is very annoying.

If they came out of a PSU, they are likely power FETs. High power NPN transistors are becoming increasingly rare to find in the "wild." Although it seems like the transistors you listed are in fact NPN, so I guess you already researched them.

If you still cannot get them to work, build up a quick and simple transistor tester to see if they are good. If you salvaged them from a dead PSU then it was probably dead for a reason. Worse case, order a few MJE3055s.

i805 -max-1 month ago
the pinout are BCE like all power tra as i've noticed even mje3055s.
they are not fet the datasheet tells they are npn tra.
the tra tester verified they are ok.

i dont have access of buying parts and even if i did what would be the fun of it :)

i'll try them on a joule thief
or maybe the joule thief which is oscillator can work the coils, just a thought
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