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Benj

Sun Aug 07 2011, 04:32PM

Registered Member #4050 Joined: Sun Aug 07 2011, 04:06PM
Location: France
Posts: 17

Hi all, i've built my first ZVS driver, thanks to this great website:

I'm using a 12V-2.1Ah lead-acid battery to power the whole thing.
Yet, i'm a bit disappointed by the results: I can get some nice arcs ( 2 cm long i'd say ), but it takes 11s to charge a 2270 ÂµF capacitor bank to 300V ( more or less 10 W output ). I've read on the internet that 50W power output is possible with such a design .

So i'm thinking about some improvements:
-I was thinking of winding my own transformer. For now I am using an old CRT transformer ( like this one

). Is the effort worth the price?

-I used N4007 rectifiers in stead of UF4007 rectifiers ( 300ns recovery time against 50-70ns). Is this a cause for concern?

-I used two 2.2Âµf 250V mylar capacitors for the equivalent resonant capacitor.

I'm looking forward to reading your comments & suggests.

Thomas W

Sun Aug 07 2011, 04:35PM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

Hi,
im no leading authority on this type of thing but i think it would be alot better to take the ferrite out of the current secondary and wind a few turns of heavy gauge wire on it until you get ~ the voltage you want then rectify it and try it out :D

BTW: wecome to the forums :D

haxor5354

Sun Aug 07 2011, 04:54PM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

12v input is not enough, 36 volts would be nice.
but if you want some VERY long arcs from a modern DC flyback, pump in 48 volts. (it may fry your flyback transformer)
heres a video of my flyback with 50v input

careful when drawing long arcs, that b*tch bit me yesterday and it died on me as well :(

Benj

Sun Aug 07 2011, 05:00PM

Registered Member #4050 Joined: Sun Aug 07 2011, 04:06PM
Location: France
Posts: 17

Hi Tom, thank you for the answer. Just to make sure i understand what you say: Do you mean i should withdraw the ferrite core from the plastic surrounding it ( to make something like that

The fact is that i do not want to damage the core...

hi haxor,
well, it sounds great, but making arcs is not my goal here ^^ ( the real one is to charge capacitors rapidly). I was thinking about using two 12V batteries, thus getting a 24V equivalent battery, but first i would like to "debug" my work .

Forty

Sun Aug 07 2011, 05:35PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

if it's for charging caps, then you definitely want to wind your own transformer. soaking the flyback in acetone for a few hours usually loosens up the core so it can slide out.

you should use the uf4007 diodes instead.

Benj

Sun Aug 07 2011, 06:51PM

Registered Member #4050 Joined: Sun Aug 07 2011, 04:06PM
Location: France
Posts: 17

Thanks forty, i'll try this tomorrow. BTW, does acetone dissolve electrical insulation on copper wires?( scavenged from a transformer)

Benj

Mon Aug 08 2011, 06:56PM

Registered Member #4050 Joined: Sun Aug 07 2011, 04:06PM
Location: France
Posts: 17

Hi all, acetone soaking worked great, so i made my own transformer this afternoon:
-I made a 4+4 primary. The secondary is approximately 240 turns.
- the results are: The sparks are less than a centimeter long, but the thick copper wire I use to make sparks turns red within 2 seconds. I haven't tried to charge a capacitor yet as the current is still unrectified. So i think it's a success.

Forty

Mon Aug 08 2011, 08:39PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

i have yet to have the acetone eat through wire enamel (or even the tape on E-core transformers.) if you're charging caps to ~300 volts then a large spark is not what you're after. you want a tiny, very hot spark, as that would indicate a lower voltage, but a lot of current. 240turns/4 turns =60, 60x12v=720v (i know this math doesn't work for this topology but it gives a ballpark estimate)

i would double your primary turns before you charge anything. and build your own rectifier out of fast diodes instead of using a full bridge chip.

Benj

Mon Aug 08 2011, 09:08PM

Registered Member #4050 Joined: Sun Aug 07 2011, 04:06PM
Location: France
Posts: 17

Thanks for the advice = ).

How fast should be the rectifiers? Because I'm not sure my that usual retailer sells UF-4007-like rectifiers.

Forty

Mon Aug 08 2011, 10:43PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

i think anywhere under a couple hundred nanoseconds should work fine. vishay and fairchild will sample you some, and digikey always has just about anything you might need.

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