2n3055 flyback transformer driver for beginners
10 Steps

## Step 3: Putting the circuit together

Connect all of the components together as shown in the images above.

I would recommend using alligator clipped wires for now so that you can check that the circuit works before you solder it all together.
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mopuccino says: May 14, 2013. 8:46 AM
hey alex ,just wondering ,do you know what is the voltage and amps of the output of this device?(using 12v input) does it work with 9v?(square battery?)
dmytro509 says: May 5, 2013. 4:06 PM
Are there any other resistors I can use for this driver?
Alex1M6 (author) says: May 5, 2013. 4:34 PM
Why what sort of resistors do you have?
dmytro509 says: May 6, 2013. 6:44 AM
I have the same value resistors that are required in this build. They're just rated at higher wattages. Like I have a 20 ohm 20 watt resistor.
Alex1M6 (author) says: May 6, 2013. 1:56 PM
That is fine. Using higher wattage resistors is fine, it just means they can handle more heat (20 watts of it in your case).

If you put a quarter watt resistor in there though it would be a different story (small resistor + lots of heat = flames lol).
dmytro509 says: May 5, 2013. 4:06 PM
Are there any other resistors I can use for this driver?
vivabrdi says: Apr 23, 2013. 10:14 PM
Help! Thanks, your's is the best simple driver posting - but, I can't get it to work!
Tried 3 different flyback transformers, 2 transistors, two different windings (7 x 11 and 5 x 20), powered from both 2 x 6V dry cells in series and also a car battery, triple checked continuity and resistance on all parts, but.... no spark! Not only no spark, no heating of the transistor, no noise, nothing. Is this a hoax?

How does this circuit create a high frequency oscillation? Why does mine create neither sparks, no noise, no noticeable heating of any component? Components: radio shack 2n3055 transistors, 220 and 22 ohm 5 watt ceramic resistors, tried with and without the diode. Any ideas?
Alex1M6 (author) says: Apr 24, 2013. 7:48 AM
Have you tried reversing the primary and feedback coils polarity? Do them one at a time as it will only work in a certain configuration.

No this is not a hoax, with it working when you first apply power to the circuit current flows through the potential dividers and into the base (which the potential dividers bias it to at around 0.8v). As the transistor begins to turn on current starts flowing through the primary coil (storing energy in the core) into the transistors collector, out of the emitter and then to ground.

But since there is the feedback winding sharing the same core current will be induced onto that too. This is why it needs to be connected in the correct polarity so that the current induced onto this winding turns the transistor off. When it does turn the transistor off the voltage across the primary coil will be now ring up to many times that of the original input voltage, and so will the secondary coil thus causing the HV.

This is also where the fast recovery diode and maybe a small capacitor help to protect the transistor.

Have you checked each individual component out of circuit? A good transistor should show about 0.7v drop between the Collector-Base and Base-Emitter junctions. If you used magnet wire for the coils then check for continuity there as sometimes not scraping enough enamel away makes for a bad connection. Also when winding the coils it can be easy to accidentally scrape of some of the enamel with the core edges and that can create shorts between windings.

Check the current draw too of the circuit and the voltage of your power sources when under load.

Hopefully you'll get it working ( :
TheNickmaster21 says: Apr 18, 2013. 11:38 AM
Why can you not just connect the batteries to the transformer? I'm new to this :P
Alex1M6 (author) says: Apr 18, 2013. 8:42 PM
The transformer needs high frequency pulsing DC to work, if you just connected batteries directly to the primary coil you will just short out the batteries and nothing will happen.

You could get some small sparks though by manually pulsing the battery through the primary coil (although they would be very small and hard to see).

This circuit self oscillates and gives the primary coil the high frequency pulsing DC it needs to function (plus the flyback "back emf", that is the real reason for the high voltage).
ii_awesum says: Sep 25, 2011. 7:24 AM
(removed by author or community request)
ii_awesum says: Sep 25, 2011. 5:18 PM
Sorry about that, posted on the wrong article! Oh the joys of having so many browser tabs open ;)
Alex1M6 (author) says: Sep 25, 2011. 8:37 AM
Ok, thanks.

But this instructable has nothing to do with disposable cameras.
sconner1 says: Sep 26, 2011. 12:05 PM
Cameras use a charge pump circuit to get a high voltage for the flash bulb from a low voltage battery.
So it's kinda related, if you just need a low current high voltage source.