555 flyback driver. / Projects / Forums

Forums

4hv.org :: Forums :: Projects

« Previous topic | Next topic »

555 flyback driver.

1 2 next

Move Thread

LAN_403

Arcstarter

Sun Nov 23 2008, 05:41AM

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

Well, it is the same as my old 555 flyback driver, but now it is mounted on a piece of plywood(5 ply, if you must know). Just a normal 555, with 2.2kohm duty cycle resistor, and a 1kohm resistor in series with a 100k pot(for wide frequency range). It is made on a small pc board from radioshack. The wood i mounted it all on has a small 12 volt 1 amp transformer smoothed with 150uf cap(two 75uf caps paralleled) and a 2200uf cap. It is messy, but it is good because if i need to change components, it is all just opened. I also use a resonant cap, it is about .80uf(better than 1.20uf performance wise) tantalum. It is too small, and heats up quite a bit. At first i used a 20 volt 1.8 amp regulated transformer, but it died, and then i used 24 volt .8 amp transformer, but it died too. I used an irfp460 mosfet on a small heatsink. It got pretty warm, but once it got to that temperature, it stayed that way. I was getting very nice arcs, they where hot. But then, i decided to bring out the big guns. I got my 30 volt rewound MOT, put a 4 amp 600 volt bridge rectifier on it and an 8000uf smoothing cap and fired it up. The sparks where just absolutely incredible. Just huge. It had to be at least 800 watts, because when i drew the arc, the lights dimmed quite a bit. It was a huge amount of current, and probably 20kv. Well, the mosfet heatsink was too hot to touch after 30 seconds of switching it on and off. I gave it a little rest, and when i got back i decided to lower the frequency just a little bit. That was about the highest voltage i have EVER seen from a dc flyback. The spark literally ignited 4-6 inches away, and at that point the sparks where still huge flaming arcs. Just incredible. I went and got my camera and let the poor little irfp460 cool, and tried to fire it back up, and i got one tiny arc, and she died. Not catastrophic failure, but just shorted to mot. I disconnected the mosfet, and the mot pulled no current, so the bridge rectifier and cap are all right. The 555 is all right too. I put my 60 amp 600 volt IGBT on it but it died after one tiny little spark. It was sad, but when this junk box arrives, i will take one good mosfet or igbt, and try it again. The flyback is still alright, i think. I am shaking, because it was shocking (no pun intended)to see what kind of sparks could be created with a simple 555 driver. Once again i will say, just huge. It turned my alligator clip that i had on the ground connection on the flyback red in 2-3 seconds. After a few more seconds it sparkled and dripped hot metal.

The best highest voltage flyback driver i have ever had, and i don't really want any more voltage than this, because you must use a chicken stick. It was only 30 volts in, so i figured i would just hold it by the wire high up, and i felt a slight little prickle, because it went through the insulation(not completely, just a tiny bit).

jovica

Sun Nov 23 2008, 08:08AM

Registered Member #1790 Joined: Fri Oct 31 2008, 10:10AM
Location: Sydney, Australia
Posts: 40

sound like an intresting experiance.

In what way did you place the resonant capacitor S to D or parallel with primary ?

Hmm 800watts ?

wouldnt the bridge rectifier have to be rated at like 20 amps minimum.

If your are placing the res cap across primary, you need to make a little mod to the gate, it is just a resistor and fast diode to ensure there is a fast turn off, and a slow turn on which protects the mosfet from dying in this application.

--TL--

Arcstarter

Sun Nov 23 2008, 08:18AM

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

Hmmm, i was off by a long shot. It was around 250 watts at higher frequency, but probably alot more at the lower frequency because the voltage is pretty freakin' high. I just took a video, i will download it tomorrow, cause it is 2:17 am here. *sigh*

Dr. Dark Current

Sun Nov 23 2008, 09:15AM

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

Arcstarter wrote ...

Hmmm, i was off by a long shot. It was around 250 watts at higher frequency, but probably alot more at the lower frequency because the voltage is pretty freakin' high. I just took a video, i will download it tomorrow, cause it is 2:17 am here. *sigh*

Nice. The problem's that this driver is very inefficient, and it is by no means "the best flyback driver". It can easily burn close to half of your input power in the FET.

Arcstarter

Sun Nov 23 2008, 08:34PM

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

Dr. Kilovolt wrote ...

Nice. The problem's that this driver is very inefficient, and it is by no means "the best flyback driver". It can easily burn close to half of your input power in the FET.

Agreed, if you want high power and great efficiency use the ZVS. But since i cannot get my zvs driver working(a scope would sure be nice for that) I ripped the mosfets out of it to use for the 555. But it is cool to have large audio modulated flyback sparks. In a few seconds the heatsink is pretty warm, so it is very inefficient. Well, i burned my last two mosfets and i am out of 555's. I took a video, i will upload in a minute. The audio modulation actually sound very very clear, i just didn't set the radio good on the video, so it was staticy and had a high pitched wine to it.

Chris Cristini

Mon Nov 24 2008, 03:30AM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Cant wait to see the video.

Arcstarter

Mon Nov 24 2008, 05:08AM

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

The arcs look so much smaller on the video, but maybe they are not so impressive, or really at all. I guess i was just excited that i got sparks that big. Anyway....

Chris Cristini

Mon Nov 24 2008, 01:37PM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

they look good to me.

Zenador

Mon Nov 24 2008, 02:34PM

Registered Member #1733 Joined: Thu Oct 02 2008, 03:17PM
Location: Hamilton, ON, Canada
Posts: 100

Thats better than I'm pulling with my flybacks. Sound is better too. Other than short run-times because of the FET heating up, that's the result I'm looking for with my setup. 2 days of playing with my 555 setup and I can only pull 12mm arcs. I'm so jealous.

Z

Chris Cristini

Mon Nov 24 2008, 03:20PM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Try to build one of these it works good for me at 5 to 30v use a large inductor and a .22uf 250v capacitor.

1227540004 1749 FT57869 Flyback Modifacations

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob