DIY Flyback Transformer

[boylesg]

I made this with the ferrite core of a tv flyback transformer and some high voltage magnet wire from a microwave oven transformer - not really an ideal gauge for his sort of thing but it is what is available for $0.

Is there any source of free magnet wire of particularly long lengths and of a finer gauge that I should consider exploring? Perhaps washing machine engines or something like that?

Judging by the size of the tiny arc it produces, it is outputing in the vicinity of 5000V at 13kHz. I take these things have resonance properties and I can fiddle around with the frequency and possibly get a bit more out of it?

I have not bothered to wind it methodically with insulation layers between windings. Instead I just continually smeared petroleum jelly over the windings to exclude hopefully most of the air.

I am making several of these and intend to connect them all in series to possibly get similar output voltage to the manufactured flyback transformers.

By the way, what cause the tone (sound) when these things are running?

 

[FoxyRick]

The operating frequency makes a big difference, so it's definitely worth playing with. You could add a feedback coil to turn the driver transistor(s) on and off which will make it run closer to resonance.

I've never found a cheap source of usable fine wire either.

The sound is simply due to the coils (and core if not fixed) vibrating with the magnetic field, and the hiss is caused by the corona discharge.

I'm not sure connecting several together will work out. I would be interested in the results...

Be very careful not to breath the ozone gas that is created by the discharge - it is extremely poisonous. I've almost passed out from that before now, in less than a minute of having my head over a big arc. The odour of it is obvious.

To be honest, I always found using the salvaged secondary HV coils worked out better than my own wound ones.

Have (safe) fun! :-D

Edit to add: I use petroleum jelly to make quick firelighters (I do a lot of outdoors backpacking type stuff). I wonder what will happen to your coil if it gets a bit warm and the discharge hits some PJ vapour? :shock:

 

[boylesg]

I'm not sure connecting several together will work out. I would be interested in the results...

It seemed to work for a couple of car ignition coils. Linking their primaries and secondaries in series yielded an arc twice as big for a given frequency.

To be honest, I always found using the salvaged secondary HV coils worked out better than my own wound ones.

Not surprising but it is still fun to try.

Edit to add: I use petroleum jelly to make quick firelighters (I do a lot of outdoors backpacking type stuff). I wonder what will happen to your coil if it gets a bit warm and the discharge hits some PJ vapour? :shock:

It has crossed my mind. But I have read that people use mineral oil to emerse their xformers in, and that will burn if it gets hot enough.

I figure that if my diy xformer gets hot enough for the petroleum jelly to ignite then the fact that petroleum jelly vapour is flammable will be the least of my worries.

What is the boiling point of petroleum jelly anyway?

Once and if I get these things working I was going to also emerse the whole set up in oil of some sort.

 

[boylesg]

The resonant frequency of this transformer is some where around 1kHz.

I am making a similar one with slighltly finer wire, and hopefully a lot more turns, also salvaged from a microwave transformer.

What is the relationship between resonant frrquency and number of turns and size etc?