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Safely add a Flyback Transformer to a an electrical fence transformer to make plasma? Answered

Hello, Just a few things you should know first: This is my first post on Instructables, and I am kind of new to electronics.

I have a very old outlet powered electric fence charger that I recently took apart because it was broken.  I took out the transformer and hooked it up to the wall (110v 60hz) bypassing a large resistor and capacitor and was able to get a stable arc of plasma about 1/4" long.  As best i could tell the transformer does not have an internal rectifier so the output was AC.  As for the voltage and the amps I can't tell, The limit of my multimeter is 500v and it went past that even with the resistor and capacitor hooked up to it and the output voltage is not labeled on it.

I am hoping to connect a Flyback Transformer to this to make a Jacob's Ladder and possibly experiment with some plasma. I do not yet have one but I am currently looking at a few on Ebay that are standard in Sony TVs.

So i guess my questions would be:  Is it safe to connect a flyback transformer to it? Is it even safe to hook up 2 transformers in that manner?  Would it burn it out? And what kind of Voltage could I expect out of it? Would that kind or brand work well?

Any help would be appreciated,



Best Answer 6 years ago

There are many ways you can connect transformers in series for more voltage or parallel for more current. although ive never tried combining a flyback and another one. its always best to combine the same type of transformers and not mix them, flybacks also require drivers because they operate at high frequencies (20kHz-80kHz) there is a fine ballance between voltage and current that allows you to draw an arc, there is also several factors like the air quality, whats in it, and the humidity. i have a 12kv 30ma NST that can start arcing when it is an inch away from its 0HV source on a moderately dry day. i have also seen several old school flybacks that can produce around 10,000 volts at about 200 ma and draw an arc about a foot long. (the total distance my lil transformer can go is about 4-5" What type of flyback do you have? is it like a big box shaped ferrite core with a huge winding and a small primary? 4 or 5 connectors? or is it one out of the TV's with several pins on the bottom? if its the latter of the two, most modern flybacks have many coils and share connections among pins. first you're going to want to take a continuity meter and find your sets of connected pins. there should be two different sets, and one or two pins with no connections. one of these (most likely the one with either 2 or 3 pins) that is going to be the primary coil. to test simply hook up the leads to the pins and find what configuration has about 1 ohm of resistance (might vary slightly) this is your primary. finding the secondary HV out is easy, its the big red wire at the top, to find the "ground" pin for that coil. you want to hook the positive end of your volt meter to the hv output (red wire), then the negative of your volt meter to the negative of a power supply, (any kind you have will probably do, make sure the current isnt too high) there are several instructables for making power supplies out of modded PC power supplies. then take your power supply and put it at 12-24 volts. then test each pin with the positive lead of your power supply and when you get a voltage reading you've found the 0v HV pin (you cant measure resistance because until you get a high voltage and high frequency going through it its resistance is several megaohms) next step is finding the polarity of your primary, because they have an internal diode, (since they use pulsating DC instead of ac in the newer ones) and a rectified output to get you hv pulsating DC. to find this, solder a few wires to your primary pins. hook your volt meter up to your secondary HV out and 0v HV pins, take a 9v battery, hold one of your primary connections to it and put the other over it and tap it with your finger rapidly to simulate pulsating dc. you'll see voltage spikes on the volt meter, (you might have to do it for awhile to get some good ones) then try reversing the batteries polarity. which ever produces the biggest spikes will be the correct polarity (the wrong one will not produce much at all, the right way maybe up to 60 v or so) now the feedback is the hardest to find (although if you make a PWM chip, or 555 timer driver instead of a mosfet or transistor driver you wont need a feedback) to find my feedback i hooked a freq square wave generator to the primary, found its best operating frequency, and used an osciloscope/volt meter to find the best "feedback coil" i dont really know many other ways :/ another thing you can do is wind your own primary/feedback on the exposed ferrite core on the outside of the plastic casing :) i'd say about 6-10 turns for the primary and about 2-4 for the feedback. they can be right next to eachother. look around on instructables for help with drivers and coil identification! hope this helps. also if you're looking on ebay and just want a simple thing you can plug into the wall and combine with your other wall plug transformer i'd try finding an old NST (neon sign transformer) without GFCI protection. although do not get the ones with oil soaked paper as insulation (for obvious reasons xD) get the one with the polymer plastic insulation stuff :P use that to play with high voltage for awhile :) flybacks are more specialized and go into much more depth, as well as require some electronical knowledge on digitial electronics components. look up grenadier or Electorials. for some good HV guides! hope this helps.


also, the best place to find good flybacks if you still want one of them, is going to a pawn shop or goodwill or thrift store or something and buying an old big CRT tv. you can get em dirt cheap, like 10-30 bucks. you can get the flybacks out of them as well as several other useful components (capacitors, resistors, mosfets, transistors, transformers, potentiometers, magnet wire, ferrite cores, exc exc) (since they're just about antiquated anyways) be very careful and read tutorials on disassembling them, the television tubes can store voltage for a long time and must be discharged and are implosive if you fracture them at all! but there is a weak spot from which they were blown where you can safely release the pressure. just look up instructables :P msg me with any more questions if you have them! :)

Thanks for your reply!
Since I asked this question I have been able to experiment with a few different setups. Currently I'm using a good sized fly-back that I salvaged out of a 24" CRT TV. Coincidentally it was from a cheep 15$ TV from Goodwill as you mentioned. :)
To drive it I made the "Improved Single Transistor Driver Circuit" designed by
Dr. Kilovolt at the 4HV Forums here:

I'm very pleased with this circuit as I can usually draw 1-2 inch arcs for several minutes at a time with the transistor not even getting lukewarm!!! I'm using the MJ15003 transistor and an old 24v VCR power-supply, the circuit draws about 2-4 amps.

Again, thanks for the reply, I might look into one of those 555 timer drivers that you suggested it sounds pretty interesting. :D

yepp, you can also do pwm drivers n such. its all about creating a high frequency DC pulse instead of an AC to drive the flyback :D ill show ya my plasma speaker when im done ^__^

If you've got arcing across 1/4" it's not going to be a good idea to hook that to a transformer that has pins at that kind of spacing.
Have you got any product specifications / details which you've not yet mentioned?


Thanks for the Reply, I never thought about that. I'm not sure if that will become an issue or not because to start the plasma arc i have to get the 2 out put wires about 1mm apart. Is it possible to insulate the wires from starting a spark just in case?

And for Product specifications I can't seem to find much other than its Sony Brand and its from a TV I looked around and can't seem to find basic specifications for it or any of the other ones listed.

if its for a TV it'll have the pins and such. but like i said i wouldnt mix the two types of transformers. i'd get two flybacks (preferably from old tv's you find on the side of the road or someone gives you got 10 bucks) and make drivers for them, and then hook them together :)