Re: [DIYbio] Re: HV Power Source

I should note that my argument against pulling flyback circuits from CRTs is based around the fact I've always seen the flyback driver either epoxied onto the side of the CRT itself or built in line with a larger circuit board somewhere inside the casing - out of many attempts over the years, I've never managed to slice it out of a larger board or break it free of the CRT without damaging the circuit beyond repair, so my efforts to recycle flyback transformers have always involved pulling the flyback transformer itself and then sticking it in a network analyzer to find the resonant frequency and building a suitable drive circuit - so it's not my personal preference - but if you are able to remove the complete circuit in-tact then it might be a better option for you.  I do like the ion generator recycling idea as well, but I don't have any lying around and I can't see one breaking without the flyback circuit being broken, so I would expect $40 to be better than the $100 I typically see the things sell for.

On Monday, March 12, 2012 7:57:18 PM UTC-4, Cory Geesaman wrote:

Doubling circuits become too lossy for practical use around v*64 where v is the starting voltage so flyback transformers are a better choice for most high voltage applications in equally small form factors (still require AC).  I'm trying to get into the MV range for some experiments so I'm just using the 7KV-8KV flyback circuit from ebay as the injector for a liquid Van De Graaff generator.  I think flyback transformers can also handle a bit more energy/time than a doubling circuit (without getting into extremely high capacitances that also support high voltages [on the order of v*32 from the original voltage v]).  As a comparison, to get 7KV-8KV you would need a starting voltage of 109.38V-125V without accounting for losses, you would probably be safe going straight from mains in a doubling circuit, but I like the added safety of using a transformer to limit the overall current that can go through the circuit, especially so for things that can push harmonics back through the generator and change it's natural resonance/rate of charge.  A flyback circuit provides an oscillator that is usually separate from that of mains (usually of a much higher frequency than 60Hz), which provides the added buffer against undesirable surges of power when coupled with the saturation of the flyback transformer itself.  You could get around the safety issues and get a bit more of a variable energy/time by adding a mosfet-based drive circuit with an oscillator behind the input of the multiplier circuit (able to avoid being a passive circuit and detune from resonance to lower the throughput from it's maximum [determined primarily by the charge/discharge time of the capacitors]), but then you end up with something about as time consuming to put together as a drive circuit for a flyback transformer.  I just like the one from eBay because it's a cheap flyback circuit that comes pre-tuned and has a variable resistor to detune it if needed - no need to determine the resonance of a flyback you pull from a CRT or build any of the drive circuitry.

On Monday, March 12, 2012 5:17:12 PM UTC-4, Mega wrote:

This http://mosfetkiller.de/?s=kaskaden
describes a cascade.

It's used for doubling, (depending on how much condensators u use...
*2 *4 *8 *16 ....) input voltage....

the only things you need are such condensators as shown and strong
diodes. Using two 9V Batteries -> 18V * x



On 12 Mrz., 21:00, Mega <masterstorm...@gmail.com> wrote:
> There is a forum called Mosfetkiller. There they discuss the best
> sources and cicuits and applications for HVoltage.
>
> Unfortunately, it's only german I think.
>
> On 12 Mrz., 13:48, Cory Geesaman <c...@geesaman.com> wrote:
>
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> > I'm playing around with a fluid-based Van De Graaff generator and needed a
> > KV level HV source - since the subject has come up on here a bit in the
> > past I thought I would post this link, as it seems pretty good ($40 with
> > shipping to avoid the hassle of making your own drive circuit for a flyback
> > transformer scavenged from a CRT or similar):http://www.ebay.com/itm/MXA028-HIGH-VOLTAGE-DC-GENERATOR-BOARD-9-15-V...

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