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 #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I had an idea for an ETG trigger mechanism, and after checking that stud diodes are available from Ebay for a few £'s each, with free postage, that are rated for 1200V and ~10,000Amps for <10mS, I sketched the circuit below:
C1 is a capacitor bank (electrolytics?), diodes are strings of the above, string length depends on breakdown voltage of 'spark gap'. C2 is a small value high voltage capacitor.
When switches S1 and S2 are closed, both capacitors charge up to the 'low voltage' supply voltage, then S1 and S2 are opened.
When switches S3 and S4 are closed, C2 charges up until breakdown voltage of the spark gap is reached, and C2 discharges through the spark gap. When C2 discharges, initiating breakdown, C1 is able to discharge through the spark gap, creating a 'HUGE' spark.
Can anyone see any problems with this idea? I realise I may want to add a resistor to the HV supply line. Any other reccomendations? Any other comments will be appreciated.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
There is no fundamental problem with it, other than conduction losses in the diodes and the risk of blowing them up.
You might also like to try a setup like a high pressure arc lamp ignitor or TIG welder HF unit. In other words, instead of putting diodes in series with the main power supply, you put an inductor in series and induce a high voltage pulse in it by transformer (or Tesla coil) action. An inductor may well be less lossy than a string of diodes.
I've seen both the diode method and the inductor method used for starting arc lamps.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Steve Conner wrote ...
There is no fundamental problem with it, other than conduction losses in the diodes and the risk of blowing them up.
You might also like to try a setup like a high pressure arc lamp ignitor or TIG welder HF unit. In other words, instead of putting diodes in series with the main power supply, you put an inductor in series and induce a high voltage pulse in it by transformer (or Tesla coil) action. An inductor may well be less lossy than a string of diodes.
I've seen both the diode method and the inductor method used for starting arc lamps.
Yes, we've discussed the HF TIG welder type circuit here before. I've a couple of questions regarding this. If I remove S3 and S4, along with C2 and the diodes, and place the HV pulse transformer where one of the diodes is, won't C1 'see' the voltage induced accross the transformer secondary? (I know I used HV capacitors and chokes when I built an HF TIG welder to keep the HV away from the lower voltage rated components.)
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I've looked at this again, and even if I put a transformer where C2 is, I still see the same problem, ie C1 will 'see' the transformer.
As I see it, any blocking inductors would impede the discharge of C1, although a 10mS pulse from C1 (the figure I quoted from the data sheet for the diodes) equates to one half cycle at 50Hz, I expect C1 to discharge much faster than this.
The original idea was for minimum parts count. Low voltage capacitor bank will be smaller than a higher voltage one, the only 'issue' is the string of stud diodes, although from what I've read in other threads on ETG's, spark gap size doesn't make much difference, so spark gap (and hence voltage) doesn't need to be that high, especially if the electrodes are designed correctly.
I'm not sure what voltage Neil's CCFL tripler is putting out here: , but this looks like a simple circuit for the HV, although I assume it runs from mains power. Maybe I should post a few questions in his thread?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
It doesn't matter that C1 sees the high voltage pulse. It is a short pulse so only contains high frequencies.
The inductor will slow the discharge a little, but this may not be a problem either. If you think of the inductor in a TIG welder HF unit, it is air cored with only about half a dozen turns.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Steve Conner wrote ...
It doesn't matter that C1 sees the high voltage pulse. It is a short pulse so only contains high frequencies.
The inductor will slow the discharge a little, but this may not be a problem either. If you think of the inductor in a TIG welder HF unit, it is air cored with only about half a dozen turns.
Ok, it only contains high frequencies, but I'd expect C1 to 'absorb' some of the energy. With an HF TIG welder it's usually DC (or 50-60Hz AC if welding aluminium), and DC is just 'smoothed' by inductance (50-60Hz AC shouldn't be greatly affected either, as long as the inductance isn't too great).
I suppose I should run some tests, but I do have a few other projects underway.
My TIG welder has ten turns on the air core transformer, slightly over an inch in diameter.
I should have some spare cash next month so maybe I'll order some of those stud diodes from Ebay.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Steve Conner wrote ...
C1 won't absorb any of the energy, it will appear as a short circuit to the high frequencies that the ignition pulse is composed of.
OK, I'll give it a try. My concerns were the ESR of a bank of electrolytics, although I can see that the HF shouldn't be a problem for the polarity of the electrolytics, as they won't actually be 'reverse charged'. I'll post an alternative circuit later. I'm assuming the transformer would need to be in series with C1 and the spark gap, rather than in parallel with them?
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.
ETG trigger
