If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Well, i was not suggesting to use MO caps. I honestly wasn't. I was ust comparing my cap to them.
My cap is now dead, as well as a few hv diodes and a freaking MOT. I sure had fun. I crushed some cans, one was close to ripping apart. This was at 100 joules though, and 4kv. Capacitance does not matter that much with exploding stuff and crushing stuff. It all depends on discharge current. You can have a cap with a small capacitance(like my cap) and it can still do these things if it is charged up enough. So joules is higher energy, but it is how much energy over time. So you do not need like 1kj to explode stuff, just a highish voltage capacitor that is good and discharges very fast.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Billybobjoe wrote ...
MadsKaizer wrote ...
But its not worth the time getting them compared to finding some bigger lyttics or pulsecaps, atleast dont invest money in it.
I disagree with that statement. Have you checked the prices on pulse caps lately (even on eBay)? Electrolytics are cheaper but then you need a massive freewheeling diode and they're slow, even compared to MO caps. See Steve's page here (again): The ESL is pretty good considering the price.
Thanks to Steve Ward's idea I obtained 25 MO caps from a surplus site for $1 a piece. I'll get some pics of my setup later but it crushes cans and explodes wire like a champ. I've shot some 40 shots off with my bank (at between 6 and 7kv) and they are still holding strong.
Hmm maybe I should rebuild the setup he used then, but in your fashion as it sure sounds to work nicely. We just didn't have much luck with :(
Registered Member #396
Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176
I don't want to hijack this thread so if a mod wants me to move this to a new one I will be more than happy to.
Here you can see the switch. I wanted it to be fairly quiet it consists of two solid brass cylinders ~1cm. diameter soldered into two threaded bushings which are threaded into the PVC pipe fitting tee. These are separated by a distance that would allow an arc at normal atm. pressure, but not when the fitting is pressurized. Pressure is supplied by a small bicycle shock-pump which works well because the volume in the system is low. The pressure is released first with a handheld valve, which releases the pilot air which triggers the QEV (quick exhaust valve) to exhaust the tee as quickly as possible, firing the gap. It is fairly quiet because the sound of the pressure being released is nothing compared to an open spark gap firing at 650 joules.
These are the "charging resistors". They really aren't for charging, but provide overcurrent protection for the diodes from the reverse voltage spike when using and inductive load. I blew a lot of diodes before some members helped me out in this thread:http://4hv.org/e107_plugins/forum/
forum_viewtopic.php?20670.post
The bridge rectifier - uses 3 amp BY255's because they have a 200 amp peak rating so can handle the resistor dampened voltage/current reversal.
Long extension on the controls to permit firing from a distance.
High voltage probe, pressure gauge, filling valve (schrader style), charging switch w/neon indicator, and firing valve.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Billybobjoe that is a really nice setup you got there, and from your linked thread I can see we made the same mistake not having resistors to protect the diodes.
If you got 650J you are charging them to about 5.2kV, if they are combined at 24uF.
Are all the caps the exact same of did you just use 24 mixed ones?
I got 12x 1uF/2100Vac that exactly the same and an additional 8 mixed somewhere between 0.85-0.97uF 1900-2100Vac.
With the 12 I could get 381J at 5,6kV or with all 20 636J at 5,6kV, this is if I can use a small SSNST I got lying around 4kV/20mA. Rectified its around 5,6kV.
Really cool trigger mechanism, might be a thing to do after, when you said yolu used a chock pump, is that just a normal bicycle pump?
Registered Member #396
Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176
MadsKaizer wrote ...
Billybobjoe that is a really nice setup you got there, and from your linked thread I can see we made the same mistake not having resistors to protect the diodes.
If you got 650J you are charging them to about 5.2kV, if they are combined at 24uF.
Thanks. I figured something was wrong when I spent two hours setting up a full wave bridge rectifier rated for 20kv using 80 1N4007's only to have them killed in a few nanoseconds. The 650J was just an arbitrary number - the voltage I charge them to depends on what I'm trying to accomplish and how brave I'm feeling.
MadsKaizer wrote ...
Are all the caps the exact same of did you just use 24 mixed ones?
I got 12x 1uF/2100Vac that exactly the same and an additional 8 mixed somewhere between 0.85-0.97uF 1900-2100Vac.
With the 12 I could get 381J at 5,6kV or with all 20 636J at 5,6kV, this is if I can use a small SSNST I got lying around 4kV/20mA. Rectified its around 5,6kV.
Mine are all exactly the same - Aerovox 1.02uf 2200 VAC
I don't immediately see a problem with using two different kinds - if you keep the voltage relatively low like you plan then your chances of failure are somewhat lower.
MadsKaizer wrote ... Really cool trigger mechanism, might be a thing to do after, when you said yolu used a chock pump, is that just a normal bicycle pump?
A shock pump looks like this - (I think thats actually the exact one I have . . .) I used to use a regular pump until a friend gave me the smaller more portable shock one. With a full size bike pump and a low volume system, its difficult to get a specific pressure without going under/over - but to conclude if you already have a bike pump it probably wouldn't be worth getting a shock one as well.
Myke wrote ...
I think that most of the bleeders are 10Mohms so it would dissipate ~6.4W at 8kV. The bleeder resistor only dissipates .4W at 2kV.
This sounds correct but when I bought my capacitors I got an extra to do some initial testing on. I charged it repeatedly to 10kv then discharged it into a short. I had to do this with a chicken stick because the cap. would discharge by itself very quickly. After maybe 20 shots it did get fairly warm on the outside metal case, so I'd imagine the inside was even hotter. I wouldn't be surprised if this led to the failure of the capacitor in Steve Ward's test (mine never failed). I'd like to do the test again but the NST I used is now integrated into the can crusher shown above and that would require a bit of effort to free it up for use (I'd be happy to do it if anyone was really interested though).
Registered Member #396
Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176
MadsKaizer wrote ...
Its hard to tell, but I think your resistors are 3K5 330W, which seems rather big considering the math suggested in your thread.
R>Vmax/Ipeak during discharge Also R>V/Irms during charge
But it only means that I need to find a resistor bigger than what the calculations tell right? The bigger the slower it will charge the bank.
They are 1500 ohms (you do mean my reverse EMF protection diodes correct?) They just need to limit the current through the diodes to their peak rating (200 amps). My setup limits the current to 5.33A = 8000V/1500ohms (Assuming the reverse voltage is the same or less than the charging voltage when it rings down). There is definitely some leeway built into my system and that's generally a good thing.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Apparently around 20 microwave caps is enough to explode stuff?
