Flyback Driver circuit.

Picture of Flyback Driver circuit.

This is a instructable that contains scematic and pictures of a single transistor flyback driver.

stuff's used:

1x breadboard
1x NPN transistor (with heat sink and a fan)
1x 22 Ohm resistor
1x 220 Ohms resistor
1x transformator (or round ferrite core) with same amount of windings
1x flyback transformator
1x 12 - 15V Powersupply ( i use a battery that gives 15 volt, 400 mA)

And some wires.
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Step 1: Scematic of the driver

Picture of Scematic of the driver
After i tryed the flyback driver with the primary and feedback windings on the flyback's ferrite core, i thought: *why not try t o use a tiny transformator with same amount of windings to oscillate the process, and so i found out i would try it, and  i got 10 - 15Kv More from the flyback transformator by doing this, so i figured i would make an instructable.

i think the picture is somewhat blurry cause of the size, so il point out the important stuffs here:

* The transistor must have a heat sink.

* Before you put 12 volt in, test the circuit with 3 - 6 volts, and make shure that the transistor doesn't get overheated
(I currently run the circuit with 15 V , 400 mA, and still i cannot feel any sign of heat on the transistor)

i get around 50 Kv from this.

If you have any questions, just ask.

Step 2: Pictures & setup

Here you can see my setup.

Step 3: Sparks

Picture of Sparks

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my wookie28 days ago

if you want to simplify the schematic:

flyback driver.png
Mahitchima (author)  my wookie28 days ago

Thanks =)
True ! simple is good! =) (y)

Dillon123 5 months ago

just a tip, if your transistor heats up high, chances are you need higher ohm resistors

OVERLOADED2 years ago
So basically you found that a 1:1 transformer acts like a feedback so you have now an external feedback to drive your transistor but how does this improve it ? is-int the feedback in the FBT good enough? also are you using the primary of the FBT or did you wind your own? I have found that if you put a wire between the return and the wire that goes to the voltage divider it improves the arc also another discovery I made to drastically improve your arcs( brighter, bigger, longer,louder) is to hook up a capacitor in parallel between your output wires I made a small simple homemade one and am now getting about 90kv.

basically you have more room to build a bigger primary

hooking a capacitor across the output should only give Fatter thicker sparks not longer I believe.. really strange if you got longer sparks are you sure?
Mahitchima (author)  leviterande1 year ago
i didnt get longer sparks, just loud and strong.
i made a capacitor from a bottle of salt in water solution, + aluminium foil on the outside, powerfull, not that long lasting though.
hmmm well mine was a glass tube a few inches long and about 3 mm thick and i ligned the inside of the tube with Al foil and put a spring coil on the outside and made my connection ( HF out to coil with another wire from coil end to HF output point and HF return attached to iner foil with another wire attached to foil and leading to return end for HF return ) and it gave me what i described and never dies down,i use it all the time
Mahitchima (author)  OVERLOADED1 year ago
Ey, that's a smart one =) i'll try that one next time i gotta make myself a cap ! =)
yup they got fatter brighter and def longer that was the second thing i noticed ,,i think adding a cap boosts the voltage
Mahitchima (author)  OVERLOADED2 years ago
I found that the whole circuit was easier to wire up with a 1:1 transformer, i also Noticed that wiring both feedback and primary on the flyback transformer didnt always become perfect, i also beleive using a 1:1 transformer makes it all a bit more stable.

However, it might be that my turns on the flyback ferrite core was bad, although they seemed pretty perfect and tight.

i am happy with the results from this circuit =) the 1:1 transformer also made it easier to test if the process oscillated, by hearing the high frequent sound, before i just hooked up the flyback on my breadboard in series with the primary on the "1:1" and flyback.

i wound my own feedback and primary on the flyback, before i tested the "1:1"transformer, now i have only wound the primary on it.
i was not happy with the built in windings, the flyback started making weard noises after a while.

I have also tested my homemade capacitor on the output, dangerous powerful sparks coming out from it ! ^^
if you put a powerful capacitor on the output of the flyback, you will get strong bright loud sparks, but you dont get that high frequent non stopping spark though.
Yes I guess it depends how you want to run it, most ppl do preffer to make there own external winds as they can adjust them to there liking, its a good way to experiment, I have tried making 10p and 4f ext on my FBT and used a 2n3055 but it did not work, in fact i had to end up using the FBT feedback in order for it to work with my other transistor, the 2n3055 just never worked for me?. right now I usually run my FBT from CFL circuit it works great and adding a homemade cap really gave awsome high rep rate sparks that look like the ones used in a tazer.
Mahitchima (author)  OVERLOADED2 years ago
You can also make own windings around a round ferrite core ( a round one because it takes less time) = )
i guess the normal is 4f and 8p, if i am not wrong ^^
i got no experience with the "2n3055" however, a friend of mine used this transistor with my scematic, and got it to work though. :)
yep but I like to see what can be done with the winds in FBT itself, I like to see what they can do with simple transistor drivers, CFL or electronic ballasts, have you ever tried hooking an EB to the primary of your FBT? they produce great results because they output about 500-600VOC with the right freq to run the FBT I think around 15KHz in a square wave pattern and since they are self resonating you dont need to hook any feedback , simply hook it directly into your mains and into primary of FBT, but make sure the FBT you use has at least 11 pins on the bottom, they only seem to work well with those types.
Mahitchima (author)  OVERLOADED2 years ago
What's an EB?
EB is what I use short for electronic ballast
Mahitchima (author)  OVERLOADED2 years ago
I havent tryed that yet = ) but why should i since my circuit gives just as great result =)

remember the VOLTAGE in this circuit is not that important.
it is the Current that get's turned into voltage that's important.

Ofcourse you need voltage but:

More current in = more voltage out
thats ok im happy your good with what you got, but if you want even longer purple arcs then get a FBT with only 11 pins on bottom (10 in U and 1 outside) and hook it to an EB either a CFL circuit with high wattage or you can buy EB it gives about 600V .5-.9A with proper square wave pattern, feed this to you primary and your in business. dont run it long as it may heat FBT , one guy had his in oil.

well you should use at least 12-18volts if not more depending what your circuit or transistor can handle and about no more than 2 amps since FBT are limited to about that anyways or was it 2-4A ??? more amps means a hoter quiet purple arc, not sure if more amps means more voltage on output? but if you pass it thru cap youd get amaizing sparks (fat,long,brighter, louder and depending on cap high rep rates looks continuous.

Yergaderga6 months ago
Very cool. I'll have to try this as soon as I can find a heat sink mounting kit for my transistors.
strange I tried it with 2n3055 and yes its not fried, I tried all combinations but nothing works.. nada.. hmm... could you possibly know why?
Mahitchima (author)  leviterande1 year ago
I've never used 2n3055, The reason i started electronics and making things with it, is cause i have my whole live salvaged parts & components from broken electronics, so i ended up having lots and lots of components stored in boxes, thinking "Let's see if i can make use of it and make some cool things".

If you want this to work, go google the 2n3055, learn how it works, you should be able to know where to put things, and atleast knowing how the transistor works, which pin is what, without having to try all the combinations (hope you have a multimeeter)

In your case (since you tried all the combinations), i think it's not the transistor that is wired wrong, i think maybe there is something else, maybe you have wired the 1:1 transformer in a way that the magnetic fields doesnt work together.

1. Draw the scematic on paper.
2. Find the right pins on the NPN-transistor (mark them)
3. Wire it up using the scematic.
If it does not work, try switching pluss and minus on the transformer.

Remember the transformer's (and the resistors) task is to make the NPN "shortcircuit", turning it on and off, and if the magnetic fields dont work together it will not "shortcircuit".

By the way, Now as i look back at this scematic, i'm not quite shure that i've drawn it completely right (according to my head right now).

Look at the comments below, "daone1" used 2n3055, he made it work, if you can't make it work, you could ask him maybe?
BTW, what was the spark length before and after your 1:1 adding? (not voltage as its always guess but length in mm or inches or cm) if you remember that is? :)
Mahitchima (author)  leviterande1 year ago
1Kv = 1mm.
50 Kv = 50mm

Through air that is.

Before i added the 1:1 i had trouble keeping a constant spark, i could not drag it that long.

achieved more stability using the 1:1 trafo.
Hi again, Alright, so I took a real good look at the schematic and now I believe it is wired wrong and should never give any sparks. Its strange how anyone got sparks if they wired the schematics exactly as in the pic. I wired it a little differently and it worked . I got with 12v only 15mm sparks opposed to the original 20mm with original setup. But here is how I wired it and I am almost sure this is how you really wired it too as it seems to be the only way with a 1:1 oscillator:

1-Connect one winding to B and voltage divider
2- connect the other winding to the + and to one end of the primary. the other end of the primary goes to C

And that's it for anyone outthere. Anyway, I got 15mm sparks instead of 20mm from original feedback on the flyback
Mahitchima (author)  leviterande1 year ago
You are right, i think i drew the scematic a bit wrong, didnt feel right when i looked at it yesterday (felt a bit fuzzy after being up for over 24 hours wiring different stuff maybe) haha =)
guess i have to fix it ;)

I'm glad it worked for you!
Looks like you didnt improve anything with using my scematic though, i however got big improvements compared to the feedback on flyback.

Happy sparkin!=D
Hehe inge problem :), I wonder though how some got any sparks out the schematic, hehe, magic must be in business!
Mahitchima (author)  leviterande1 year ago
hehe, Yeah, magic ! ^^
The main objective though was to include the 1:1 trans, cause i kinda ruined 2x flyback ferrite core's trying to wind xD they break so easily!
Hi Thanks, Indeed I have been working with NPNs and know how they work. By trying different combinations , I meant the connections to the inductors and primary.. Hmm so you think something may not be right in the schematic, that's a possibility, it would be appreciated if you maybe could tell me that little detail if you remember :) . I Asked that guy but I didn't get any reply .. Thanks
can this kill you? id like to use 4 aa batteries can it kill you with that as the input voltage? reply asap.
thank you for the simplicity!!!!!!!!

Mahitchima (author)  jacobbrunberg1 year ago
10mA through the heart is enough to kill.
yes, especially if you decide to lick it...
samaddon1 year ago
Which NPN transistor i am supposed to use?
Mahitchima (author)  samaddon1 year ago
Well, you could make yourself an oscillating circuit of almost any NPN transistor, with 2 resistors and 1x 1:1 transformer, and ofcourse a power supply.

Which one you need to use is one who does not get burning hot, and one you can mount on a heat sink, you need to read and learn, or just learn by doing, trying, and failing.
OK! Thanks for advice ! i am new learner and not have much experiance so i asked you to tell me so !
Mahitchima (author)  samaddon1 year ago
the scematic in this instructable is fairly easy to follow, if you know or learn how to read scematics and have the components at hand, this will be easy =)

Check this out:

you might have something to learn there =)
OK! Thanks for advice ! i am new learner and not have much experiance so i asked you to tell me so !
samaddon1 year ago
Which NPN transistor i am supposed to use?
daone12 years ago
your circuit didn't work with 2n3055
so i changed a few things in the circuit (still kept 1:1 trans) and it work perfectly
i could drive a plasma globe at 18W input (9v, 2a) which was impossible before
that's amazing with 1:1 trans
happy sparkin~
I am currently using a 2n3055 for my flyback and I am considering trying this instructable. What exactly did you change? It would really save me some trouble if you could tell me :) thanks
OVERLOADED2 years ago
Your FBT looks big is it two of them or just a big one? it looks like it may be one of those that have internal cap.
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