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 #1694
Joined: Sat Sept 13 2008, 09:13AM
Location: Australia
Posts: 108
Hey all,
I've been trying to think up a good way to fire an electrothermal gun without the need for massive SCRs or heavy duty switches. Inside the firing chamber of an ETG, there are two electrodes. If these electrodes had 400v between them and they were say 5mm appart, current would not flow since you would need at least 10kV for the air to breakdown. If I put in two more electrodes which were almost touching and then discharged a smallish capacitor (about 50uF @ 400v) through them, this would create a spark & ionise the air inside the chamber. Ionised air is conductive and would allow the main capacitor bank to discharge.
By doing this, you would only need a relatively small/easily obtainable SCR to trigger the 50uF cap.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
If done correctly it will work. A triggered spark gap is a perfectly sensible solution to your problem. If you read a bit about them you will most likely find a design that suits you.
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
Triggered Spark Gaps are hard to space, especially in an enclosed chamber. You only need 3 electrodes, small cap +, big cap +, and common ground. The problem with this,especially in a ETG, is the corrosion, which makes it hard for a consistent spark.
Registered Member #179
Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287
I was using a triggered gap to fire my 24kj bank. The trigger was a 10kv ignition transformer to create an arc between the electrodes in open air. 100% successful operation over hundreds of discharges, until the aluminum vaporized from the current overload.
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
I'm assuming youre discharging capacitors so turning off the gap isnt an issue, 400V is close enough to whats used in disposable cameras, so I would get a disposable camera body from a 1 hour developer and take the small cap and pulse transformer from one of them.
In the ones I was usually harvesting parts from, the cap was ~ 22nF, and is charged up though a resistor, and when the trigger contacts are shorted, the current gets dumped over the pulse transformer, providing a few kV for triggering the flash tube.
If anything you can make a proof of concept before you move on to more expensive parts.
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.
An idea . . .(triggered spark gap)
They exist?! 
