Homemade ferrite cores

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Homemade ferrite cores Anonymous 12/18/14 (Thu) 03:39:16 No.35

Ok /DIY, here is what's up: So I recently made an overpowered as fuck plasma speaker but unfortunately the flyback transformer couldn't handle the current. I'm wondering, would it be possible for me to make my own ferrite cores using some PVC, resin, iron oxide(fe3o4), and a few other additives? I know most commercial ferrite cores don't have any iron compounds in them but that's what I have to work with. Any fellow Anons have any suggestions?

Anonymous 12/18/14 (Thu) 07:43:45 No.36

File: 1418888625289.webm (3.25 MB, 480x360, 4:3, Thunderstruck.webm)

>>35
Winding a flyback transformer type coil will be almost impossible without -really- good tools. For that matter any high voltage windings would be impractical to make for most /diy/ers, with the exception of the air core kind that are found in tesla coils.

But for that matter, if you wanted to go way overkill you could make a solid state tesla coil speaker for fairly cheap.

This guy has a decent and cheap schematic/parts list for a simple sstc.
>http://www.stevehv.4hv.org/SSTC5.htm
Once you have that you'll have to throw your sound amplifier into the interrupter. I can't say exactly how the circuit would look because I'm not sure of the setup your using now.

Do you have any other pics? Or a schematic?

Anonymous 12/18/14 (Thu) 15:20:40 No.37

>>36
I understand the difficulties of building one but I have built numerous ones before so I have an idea of what to do. What I am planning on doing is this:
1.getting some pvc pipe
2. cutting it so that it forms 2 c cores
3. from there I'm thinking of filling and packing the tubes with pure Fe3O4 and then sealing the tubes. This will give me a decent inductor with very strong high voltage insulation to the core.

Im hoping that from this I can make a pancake coil and put that on it. I might even make multiple pancake coils and put them in series with each other to keep their individual voltages down but have the overall voltage be very high.
For this im planning on each pancake coil having an output voltage of about 13000 volts so 3 of them in series would give a healthy 39000 volts at pretty high current. I'm not entirely sure what the core size will be but i'm planning on making it big enough to house at least 5 pancake coils. For the wire, i'm planning on using 28 gauge wire(i have a ton of it and also in other sizes) This will all be run off of a high power zvs driver that is capable of handling over 1000 watts.

Anonymous 12/18/14 (Thu) 22:05:09 No.38

>>37
Fe3O4 is conductive though and I'm not sure what you are trying to gain by using it in the first place instead of a cheaper iron core. Also keep in mind that at those higher voltages things that typically would not be conductive can pass voltage. 30kV for instance is plenty to pass through pvc. But even before that the air itself will breakdown and you'll begin to leak voltage to the atmosphere. You will not get the kind of voltage you're expecting and certainly will not get high current from it with homemade windings, for HV you want dense windings to improve coupling.

Adding voltages from high voltage sources does not work like your thinking. Adding 3 coils together will not triple your voltage output because before that happens if the coils cannot individually handle the total voltage they will break down. It's really odd when it happens because it seems like it ought to work but then it doesn't.

If you're going to make high voltage coils you have to pot them in something with a really large dielectric breakdown voltage. In industry they use mineral oil for this but parrafin wax can also be used if you want something slightly less messy. This will insure that you aren't leaking voltage to the atmosphere.

Honestly if you are wanting those kinds of voltages at high current (>15mA) you should buy a neon sign transformer. You can find them used for under $50 dollars or so. Otherwise you'll run in to all kinds of problems just to have it not work in the end.

If you're wanting a large plasma speaker I would seriously consider the tesla coil option, everything else will be painful.

Anonymous 12/19/14 (Fri) 03:41:33 No.39

>>38
30kv will not go through PVC. Trust me, I've tested it.
Second I NST runs on 60hz, which will produce an annoying buzzing noise in the arc. I'm not concerned about the high voltage portion so just try to focus on the core. That is what trying to find more info on.
And as for just using an iron core, the one required for my purposes would have to be huge. Also, iron(especially the laminated cores) have very high hysteria losses at frequencies that my driver operates. So any form of solid iron core is out if the question.
What I'm planning on doing is taking fe3o4 which is ferrimagnetic and powdered, and putting into a PVC tube and adding some type of cougulant to solidify it. It wouldn't be perfect or super efficient, but it should be able to operate in the frequency range of my ZVS driver.

Anonymous 12/20/14 (Sat) 02:38:44 No.40

>>39
That might work. I'm not too sure though, I know for the really high frequency stuff the tendency is to go with air core solenoids to prevent the hysteria losses.

For the core then you'll want to go with some kind of two part epoxy.
The kind they use for fiberglass should work.
http://www.westmarine.com/buy/west-system--g-flex-650-liquid-epoxy-8-oz-one-4-oz-bottle-of-resin-one-4-oz-bottle-of-hardener--9223132
You could probably get away with mixing the first part with the fe3o4 then stirring in the second part. It takes a while to set and should pour into the molds nicely. It will get incredibly hot though so you might consider pouring into something other than PVC.

Anonymous 12/20/14 (Sat) 04:08:15 No.41

>>40
Yeah that sounds like a good idea, I saw a video on youtube where the guy used plaster of Paris instead of an epoxy.
I tested some of the material in the zvs driver(basically an induction heater) and if really didn't heat up all that much so that's a good sight. The fe3o4 has about the same magnetic strength of the ferrite so that is also good.
Additionally, I was looking up some recipes in the depths of the internet, and one went something like this: 85%fe 6%al 5%carbon 4% zinc. All of these I have and in thinking about mixing up a batch of this and mixing it with a bit of epoxy(probably make it into a rod) and then I'll test it to see if it works. I'll post my results in the thread whenever I get the chance to.

Anonymous 04/30/15 (Thu) 12:40:31 No.108

Cores should be made out of layered metal.

With a solid core, the effect of AC will make the current concentrate on the surface of the core, causing inefficiency and overheating.

Anonymous 05/29/15 (Fri) 23:06:32 No.118

I'm someone who isn't OP that has a similar want. I've been experimenting with oscillators and I want to make a dirt cheap diy for my circuit. But a reasonably high permeability core large enough to put several hundred winds on is a rare thing if you try to find it in the scrap pile and an expensive thing if you special order it.

So maybe someone could help me out? A cheap diy 5" toroid or something, bonus points for being made out of commonly available ingredients.

Anonymous 10/06/15 (Tue) 01:16:44 No.161

here's my 2¢

ferrite cores are used when high frequencies are involved because…

a. you want the high permeability and magnetic flux density for power transfer otherwise you'd be air-core

b. you want low hysteresis for the quick reversals of the magnetic field

it's always a trade-off between permeability and low hysteresis

c. you want electrically isolated small particles to reduce eddy current losses

I would suggest experimenting with ferric /ferrous oxides and silicates as fine powders mixed with epoxy resins.

the reason I say use some form of binder is the one thing you must avoid is allowing any part of the core material the ability to move because it will and violently. the number of transformers I've seen that were unusable because of loose core material or a cracked core is not zero. loose core material causes noise at the very least. the commercial high frequency cores I've seen have all been sintered, that is to say made using heat and pressure and molded into a solid monolithic piece.

best of luck with your project