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How do I make a 47 to 200uH coil for the Mazzilli flyback driver?

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LAN_403

cavemen

Tue Mar 03 2009, 11:16PM

Registered Member #2008 Joined: Tue Mar 03 2009, 05:11AM
Location: USA, Frederick, MD
Posts: 118

I have no inductance measuring tools.
The coil without a core, that i can calculate using formulas, would be HUGE.
Can anyone tell me the description of there coil, so I can just copy-cat it?

Do I really have to use 2w resistors for 470 ohms?

Seems like I am in the right place.

Does it work to de-solder fly back transformers using a benzomatic blowtorch?
It is so windy that even if I get one, I won't be able to do it for a while. They blow out at high winds.

Arcstarter

Tue Mar 03 2009, 11:32PM

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

The inductor should be on a ferrite toroid core. I used about 100 turns of something like 16 gauge. I use 100 watt resistor for the 470ohm, and it gets a bit warm with 700 watts.

The blowtorch will indeed work, just dont let the flames hit anything. Just put the board above the flame, and hold it there.

101111

Tue Mar 03 2009, 11:37PM

Registered Member #575 Joined: Sun Mar 11 2007, 04:00AM
Location: Norway
Posts: 263

30 turns on a yellow SMPS filtering core will do the trick :)

...

Wed Mar 04 2009, 12:22AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

A ferrite core may work, but you would be using it in saturation (which doesn't seem to have an effect on performance, but if it doesn't work the first thing we would tell you to get a proper inductor), a much better idea is the yellow core out of a computer PSU. Again, 30 turns here will probably work, but will only give you on the order of 10-30uH, in my kits I have about 200 turns on a yellow/white core (t6 size, about what you find in a computer psu) which has been measured at about 100uH

cheers!

GeordieBoy

Wed Mar 04 2009, 12:28AM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

If it is a current-smoothing choke for the Mazilli oscillator then it should be wound on an iron-powder toroid (yellow/white colour toroid pulled from SMPS) or possibly a ferrite stick inductor. Definitely NOT a ferrite toroid as this will saturate due to the DC flux.

35 turns on one of those Yellow/White Micrometals Type-26 iron-powder cores should get you somewhere in the region of 100uH depending on whether its a T106-26 or T130-26 and also how much DC you're pushing through it.

As for the blowtorch, I can personally recommend investing in a soldering iron!

-Richie,

Dave47

Wed Mar 04 2009, 12:59AM

Registered Member #84 Joined: Thu Feb 09 2006, 01:06PM
Location: Dallas, TX
Posts: 47

Along these same lines, I was curious... I have access to an Agilent 4284A Precision LCR meter (20Hz to 1MHz). What is a good frequency to use when measuring the inductor for this project? Should it be measured at 20Hz (DC) or at the resonant frequency? Is it specified at 200uH at DC so the inductance drops to some still respectable size at the resonant frequency, or what?

Just curious. Thanks!

David

cavemen

Wed Mar 04 2009, 02:32AM

Registered Member #2008 Joined: Tue Mar 03 2009, 05:11AM
Location: USA, Frederick, MD
Posts: 118

1) My fly back driver device

2) The fly back transformer.
Did i wire it correctly?
I had followed some online technique.
And I tried to send a short DC impulse through the built-in primary.
The secondary core really made a small 1cm blue spark and shocked me and my friend.

I don't need the red wires?
All I need is the ground, the thick cable and the access to the core?

One of the legs of the transformer is missing but it seems to be one of those additional function legs.

Do I wind primary at the front, where I have access to the ferrite core? I had seen it on the examples on this site and somewhere else.

3)Is it tough enough? I need it to be able to stand 10 amps overall?

4) Is this the wire that I should use?
AWG 12
2.05mm approx. 41A

5)Should I take the left core or the right core?

Both are yellow.
How many turns?

I have a problem. When I warm one leg of the transformer up, the other ones cool and solidify back into the circuit board. This is why i am looking for a better way to do it.

Thanks.

Sorry for the multitude of pics. I cannot describe most of those things.

If I succeed, I will make a fancy step-by-step on this project.

PS
I deleted some things that i could find on-line myself.

Ultra7

Wed Mar 04 2009, 05:39AM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

Do you own a heat gun?
If you do then this is the perfect de-soldering tool around.

Hold the board to be stripped of all its components with a vice, solder side up, and heat it with your heat gun till the solder looks like it is good and melted, then, tap the edge of the board with a rubber mallet. Most of the components will just fall out, but some with bent tabs will require quick work with your needle nose pliers. Using a blowtorch will work, but the solder mask smells like hell when it vaporizes, and the phenolic will probably give you some form of cancer if you inhale the smoke. Better to just use a heat gun, if you have 12 bucks, I think they have a nice hot one at Radio shack.

Alexandre

Wed Mar 04 2009, 04:19PM

Registered Member #1228 Joined: Tue Jan 15 2008, 01:08AM
Location: Curitiba, Brazil
Posts: 162

I did about 18 turns in a ferrite core of power supply of PC (Yellow), worked perfectly.

KLH

Wed Mar 04 2009, 07:02PM

Registered Member #1819 Joined: Thu Nov 20 2008, 04:05PM
Location:
Posts: 137

A small caution: Watch out for the particular type of toroids you get. The 26 material toroids are mostly yellow with white on one side. A very similar looking material, the 6 material, is all yellow, but has a permeability of only 8, instead of 75. This is not a problem if you're just pulling from old PC supplies, but I have made the mistake of using a random toroid that was all yellow (6) and getting strange results.

The exact inductance depends on the size and material of your toroidal core. I would recommend that you buy cores straight from a supplier such as Amidon, since they provide you Al values (Caution: the Al values for the 26 toroids and quite a few others are given in uH per 10 turns last time I checked; I don't know why). Then again, I wouldn't recommend using either of those materials at all, since they are VERY lossy. (Also, their permeability drops severely with only a few Oersteds). But I don't know if the losses would be significant here.

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