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Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Once you are certain you have everything wired correctly and it's working you can remove the light bulb, but until we know everything is correct it will prevent any more 2N3055's from blowing, or at least, it should do.
You won't get much output from the flyback, if any, with the current limiting bulb in place.
EDIT: Here's one of my home made 'overkill' heatsinks for a 2N3055. I use two PC fans on it, one either side, one blowing and the other sucking. I've never blown a 2N3055 using these heatsinks. I do have a MK2 in the pipeline, which won't require so much heatsink paste. Once the fans are fitted, I wrap the whole thing in plastic sheeting to make sure the air flow only goes where intended (through the heatsink).
Registered Member #4465
Joined: Wed Apr 18 2012, 08:37AM
Location: Bucharest, Romania
Posts: 145
Well, it’s seems you need to do some changes in the circuit wiring.
The direction of the winding, or as its called the phasing of the feedback coil could be opposite of the primary coil and thus be driving it 180 degrees out of phase, try to switch the feedback connections around. Because in practice, for various manufactures transformers, there’s different phasing on the high voltage output, you need to rewire the circuit for the two possibilities, as described in the attached pictures, in order to obtain the maximum arcs strike.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I suspect RF is correct here.
If the feedback winding is 'the wrong way round' then it 'could' still blow the 2N3055 even with over current protection, if the base is over-volted, which could happen if the feedback winding is 'adding' volts to the base, rather than subtracting them. I can't remember offhand what the max voltage to the base is for the 2N3055. (This 'possible scenario' could be avoided by adding a zener diode of the correct voltage between the base and emmiter, but make sure you get it the 'right way round'. A 'stud zener diode' would be best, as long as it's a fairly fast one)
(EDIT: $5 for 37 of them here, in USA, 6.8V +-20%, 10W, a few of these could be paralleled, if you check they are of the same tolerance:- These are only good for 1.3A according to the datasheet, which seems a bit low to me, considering the package size, and they require a heatsink. Not sure why the ad says 20%, the datasheet says either 1%, 2% or 5%)
As pointed out, if the primary is 'the wrong way round' then you will get no output, but you will probably get a huge voltage spike in the primary, which 'could' also damage the 2N3055, but a current limiting light bulb 'should' prevent this. (The voltage attained is largely dependant upon the impedance of the load, and a reversed diode presents a pretty much infinite impedance. This high voltage on the secondary is 'reflected' onto the primary, according to the 'turns ratio', as it has no-where else to go, but has to go somewhere.)
EDIT I'd also start with a ten turn primary and a four turn feedback winding.
Some have found that more than ten turns is best (I remember someone here who was surprised that 13 turns gave the best results with his setup when he originally believed that reducing the turns to lower than ten would give better results, as he thought the greater turns ratio would give a higher voltage, but a flyback is a 'coupled inductor', not a true 'transformer', and works in a different way. ).
(The 'turns ratio' of a flyback is important as the reflected voltage can't be higher than the max allowable voltage accross the 2N3055, 60V, if I remember correctly, but there are other factors that determine max output voltage, such as impedance of the load. I seem to remember that there are other factors that also affect 'reflected voltage', such as leakage inductance, which is why it's always best to put the primary under the secondary, although in this case you can't do that without using a thinner core, which would seriously reduce the output.)
EDIT: I think the above is pretty correct. If anyone has anything to add, or can see any 'mistakes', or has any further questions on any of the above, please feel free to comment.
Registered Member #54664
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I'll modify again the circuit as soon as possible, since I don't have much free time in this period.
Meanwhile, I discovered that you can also power the circuit using a ballast. Basically, you connect the output of the ballast to the input pins of the transformer, you submerge it in mineral oil for insulation and it should work. See I found a 1 x 36W ballast on Amazon (technical specs: ). What do you think?
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
it speaks well that you havent given up yet. im thinking of mailing you a circuit board etched, then have you populate it with components. its most important you understand the paths between the components. im sick at the moment and trying to read through the previous help others have offered.
Above all, i want you to learn, and not do all of the work for you.
These circuits - the flyback, ignition coils, and strobe-trigger-like transformers are all important and the easiest to learn. you must figure these out before any thing more advanced. So your doing good.
EDIT: Just out of curiosity, can you measure the voltage between the 12v and ground wires of your ATX while your circuit is operating.
Registered Member #54664
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Patrick wrote ...
it speaks well that you havent given up yet. im thinking of mailing you a circuit board etched, then have you populate it with components. its most important you understand the paths between the components. im sick at the moment and trying to read through the previous help others have offered.
Above all, i want you to learn, and not do all of the work for you.
These circuits - the flyback, ignition coils, and strobe-trigger-like transformers are all important and the easiest to learn. you must figure these out before any thing more advanced. So your doing good.
EDIT: Just out of curiosity, can you measure the voltage between the 12v and ground wires of your ATX while your circuit is operating.
Thank you so much. I'm still a student, not an electronics engineer, so I'm trying to learn as much as possible. Your help is very appreciated. The voltage on the 12v rail of the PSU is of about 12.6V.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
jaggions wrote ...
Meanwhile, I discovered that you can also power the circuit using a ballast. Basically, you connect the output of the ballast to the input pins of the transformer, you submerge it in mineral oil for insulation and it should work. See I found a 1 x 36W ballast on Amazon (technical specs: ). What do you think?
Overcomplicated. Avoid these ideas of submerging something in oil. This is not necessary for the voltages that a common flyback transformer can generate. You can use the circuit of a compact fluorescent lamp.
Registered Member #54664
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I finally did it! It works guys!! I'm really happy, thank you all for your help. Photo:
However I noticed some sparks between some of the transformer pins: . Is this ok? Or should I submerge it into oil? Maybe insulate the pins with some hot glue? Thank you again!
Registered Member #1565
Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159
jaggions wrote ...
However I noticed some sparks between some of the transformer pins: . Is this ok? Or should I submerge it into oil? Maybe insulate the pins with some hot glue? Thank you again!
Not the common advice; but try connecting the arcing pins. On the orginal board no isolation was needed, so why should it be needed now?
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Flyback transformer questions
