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How to troubleshoot the mazzilli flyback driver?

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Robert2

Sun Mar 15 2009, 03:14PM

Registered Member #1773 Joined: Tue Oct 21 2008, 06:56PM
Location: Poland
Posts: 93

How change zeners diode for 7812 ?

cavemen

Sun Mar 15 2009, 05:25PM

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

What variable on the diode's datasheet tells me if it is "slow" or "fast"

Capacitance or specified frequency? Or what else?
Most of the diodes are "general purpose rectifier diodes".

theju

Sun Mar 15 2009, 06:05PM

Registered Member #1445 Joined: Tue Apr 15 2008, 01:25PM
Location: Germany
Posts: 24

you need "fast diodes" like most of the byv types, or uf400*
mur460 or most of the other mur diodes will work fine

an the recovery time tells you if the didoe is fast or slow ;P

Dr. Dark Current

Sun Mar 15 2009, 06:48PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

cavemen wrote ...

What variable on the diode's datasheet tells me if it is "slow" or "fast"

"General purpose rectifiers" are generally slow.

The parameter you are looking for is called Reverse recovery time (or similar), as I said earlier. If the datasheet does not state this, then you can be pretty sure that the diode is slow.

Commonly used cheap fast recovery diodes are the BA159 and the UF4007 (which is extremely fast at 75ns). Both are 1kV and 1A rated.

cavemen

Sat Mar 21 2009, 02:33AM

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

Thanks for replies.
I broke my computer, so i could not tell that
i changed the diodes to HER305 high efficiency rectifier diodes with... 50 to 75ns Trr.
I also removed the zenders.

For some reason, the spark was only 1cm long and MOSFETS felt cool to touch, but I GOT A SPARK!

I don't know if i install the zenders, and decrease the primary windings, would it make the circuit more powerful?
And the inductance coil was designed to be around 50uH. Is that OK?

I had no choice, but to use a car battery as a source of high current 12V

Is there any way I can get power from the electric socket?

If I build a rectifier without a transformer, I'll get 55v DC?

If I build a transformer - type power supply, where do I get such powerful transformer?

How else can I power it?
How do I use driver's full potential. It is really tempting to see a real plasma spark.

MRacerxdl

Sat Mar 21 2009, 03:30AM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

The LC Circuit generates much higher voltage than supply, and the diodes conduct the high voltage to mosfet gates, so you will blow your mosfets in not much time... The zeners regulate the voltage to get 12 or 15V at the gate, and they also made the voltage divider (the two resistors) give the correct voltage for the gates at startup;

50uH might be ok, I use 80uH, that will depend much of the flyback and the cap that you use.

Direct from eletric socket is not good, because it make MUCH noise for the mains line and you arent insulated, so if I high voltage reaches one part of the circuit, it will reach the mains line and might burn something on your house.

For the transformer, you can use something like me, a Microwave Oven Transformer with the secondary removed, get a 2,5mm wire and made how much turns it fit on the core, you should get arround 24V at 20A capacity (or 200A short circuit)

cavemen

Sat Mar 28 2009, 03:02AM

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

The circuit had worked fine. Except instead of long plasma sparks i had a barely noticeable blue line between the outputs.

Then the tragedy had happened. A wire fell of source of one of the mosfets and I had a meltdown.\
I replaced the mosfets, diodes, EVERYTHING except the capacitor, zenders and the resistors.
I don't know how to test if zenders got fried or not.
They are rare parts. Diode on the side that melted during a meltdown got fried obviously, because it started to conduct electricity both ways.

Again I have a problem that one mosfet heats, but the other one does not. Nothing works. Why is that and how can I fix that?

I checked the voltages on the zenders at different supply voltages and there is no difference. Is there a need in zenders at all?

I cannot diagnose the difference between two halves of this circuit.

I am starting to doubt that this circuit can work properly.

After the meltdown i started to limit the current with a 1 ohm homemade power resistor and i use PC CPU.

Arcstarter

Sat Mar 28 2009, 03:32AM

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

Hmmm, use a different transformer. I used a SMPS from a laptop power supply, and it only pulled like .5 amps at 44 volts! I got an arc, but it didn't pull enough. Try a rewound MOT or some other transformer power supply. No need to regulate. Just use a bridge rectifier and a large smoothing capacitor.

cavemen

Wed Apr 01 2009, 03:16AM

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

Now it works well.
If u blow on the spark it looks like the one on the photograph.

Thanks for help.

cavemen

Thu Apr 09 2009, 04:16AM

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

How do i make it more efficient?
I am not sure if i have the right coil.
Does that change anything?

If I get even faster diodes?
If I decrease the number of turns on the primary?

I feed it with 12V 10A or 24V 3A. I regulate A to get
different spark length.
I only get 8 millimeter spark.
More current means a bigger spark?

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