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hand-winding a flyback

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LAN_403

Alchemist

Thu Jun 09 2011, 04:27PM

Registered Member #3326 Joined: Sun Oct 17 2010, 09:49PM
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Posts: 8

Since only black and white TV flybacks are becoming more scarce all the time I have been trying to think of alternatives. I've disassembled a few broken plasma globes and Lumin Glass displays and the little tiny transformer in there is obviously not a normal flyback, but apparently functions the same way.

How would one go about winding one by hand, assuming you had access to a coil winder?

What dimensions would you need and what core material?

Proud Mary

Thu Jun 09 2011, 05:23PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Why not wind yourself a good old fashioned induction coil? It would be a lot more interesting than a monotonous diet of recycled TV parts.

the mad scientist

Thu Jun 09 2011, 06:11PM

Registered Member #3768 Joined: Tue Mar 22 2011, 12:46AM
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proud mary is right, flybacks get very boring after awhile, there is quite alot you can do with ignition coils, and hand would induction coils. and they are much easier to wire

Dr. ISOTOP

Fri Jun 10 2011, 02:47AM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

Using big U-cores from e.g. TSC International, it is fairly easy to wind HV ferrite transformers that are good for a lot (kilowatts) of power.

PresentTeck

Fri Jun 10 2011, 04:00AM

Registered Member #3922 Joined: Thu Jun 02 2011, 06:24AM
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i've seen people who have made extremely high voltage transformers by hand, but not many plans on how to do so. Is there a particular method to the madness? or are you just winding a TON of secondary coil?

Dr. ISOTOP

Fri Jun 10 2011, 11:41AM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

There's a reason the industry uses multipliers for ultra-high-voltage supplies; ultra-HV transformers are hard to insulate and messy.

Arcstarter

Sat Jun 11 2011, 01:51AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Well, must it be a 'flyback'? Or do you just mean HV transformer in general? Technically, when you drive a 'flyback' with the Mazilli driver or a bridge, it is no longer a flyback transformer

If you want flyback, you just have to use a suitable core material and you need a gap in the core. As for the actual winding, it can be pretty easy depending on the voltage. You pretty much just wind a layer, insulate it, and repeat. The higher the voltage, the more care you have to take in insulating it. You can use something like polypropylene film for covering floor while painting, or polypropylene copolymer (overhead transparencies). I have used both and they work well. I suggest putting it under something like mineral oil or vegetable oil (which can go rancid), because it will be high voltage *and* high frequency, which loves to make corona.

Most ultra high voltage transformers that i have seen are iron cored, but i have seen HF transformers up to 40kv or something.

That is the transformer i made a few years ago. It only took around 30 minutes to make, and it outputs around 6kvac im sure, and 700 watts. It is under oil. I will not be making any HV transformers that aren't under oil. It is not messy if you get the container right the first time, and it increases reliability *a lot*.

Alchemist

Sat Jun 11 2011, 04:49AM

Registered Member #3326 Joined: Sun Oct 17 2010, 09:49PM
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Posts: 8

I'm familiar with winding my own transformers, mainly for low voltage applications, but I am also working on winding a custom 15KV HV transformer (or rather a pair of 7500V transformers) on NST cores to hopefully be more robust than the then 6 or so NST's I've killed.

What I'm specifically interested in, however, is the extremely tiny transformers used in plasma globes and the like. Normally if I want to light up a bottle of Argon or something like that I'll just use a flyback driver, but I've recently gotten into prop-making for Sci-Fi conventions and haunted houses, and some of my ideas are for very low-power "wearable" plasma displays. (to be used strictly by me and nobody else.) Some of my ideas I can make work using flyback drivers, but other ideas need more compact transformers. for instance, I have a "Lumin disc" style plasma display that started life as a "plasma belt buckle". There are a few things I'd like to make it do, but all the circuitry is SMD chips with unreadable part numbers so i can't just jump in and start modifying the circuitry. I'd need to start from scratch. I suppose I could use the transformer that is already on the circuit board, but there is the possibility I might damage it removing it, plus i don't know what it's specs are. I could easily damage it. If I could figure out how to wind my own replacement transformer it would solve a lot of problems.

Dr. ISOTOP

Sat Jun 11 2011, 09:17AM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

I doubt there's any magic to winding tiny HV transformers; just use lots and lots of thin wire.

Alchemist

Sat Jun 11 2011, 04:31PM

Registered Member #3326 Joined: Sun Oct 17 2010, 09:49PM
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Posts: 8

bwang wrote ...

I doubt there's any magic to winding tiny HV transformers; just use lots and lots of thin wire.

Even considering the RF aspect of plasma display driving? I've always thought of flybacks as a "special kind of Tesla Coil" since their voltage rise is greater than the ratio of turns. I know how finicky some Tesla coils can be to get the tuning and everything correct, so I'd think winding a flyback might require some sort of extra planning as well. Am I wrong? Is it really as simple as just winding a small HV transformer?

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