# Flyback Driver Circuit.

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## Introduction: Flyback Driver Circuit.

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

stuff's used:

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

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.

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## 90 Discussions

why do I need resistors? if I have the right power supply can I skip the resistors?

No =) resistor's is good, you should use them, we are only using interference to turn the transistor on and off, it would not improve anything not using resistors, only hurt or burn your transistor. (as i think the transistor gets fully saturated anyway, you could do some math on voltage dividers and transistors).

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

Very cool. I'll have to try this as soon as I can find a heat sink mounting kit for my transistors.

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.

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?

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

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

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.

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.

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