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 #4361
Joined: Fri Jan 20 2012, 12:46AM
Location:
Posts: 11
Help please. I have need to produce a single pulse of 15kV or more. I know how an automotive ignition coil works and thought i could simply pass current through the primary and interrupt it, and get the pulse out when the field collapses.
I connected one terminal of an ign coil to 12-volt power supply (20 A capability). I grounded the other terminal with a clip lead and disconnected it. I expected full output, enough to jump a spark plug but I only get 1 kV or so.
Registered Member #3883
Joined: Fri May 13 2011, 06:30PM
Location: Norway
Posts: 87
You need a small capacitor in parallel with the switch, this will prevent arcing at the primary when the current is interrupted. It also keeps the voltage down to the intended range. Start with a .2uF, rated at 200V minimum. The larger the cap the lover the voltage, so you can easily tune the coil to the correct output.
Registered Member #4361
Joined: Fri Jan 20 2012, 12:46AM
Location:
Posts: 11
Fulmen: thanks for the tip; i'm getting HV pulses now. I'll likey replace the mechanical switch with a FET; then I'll play with the cap values to get the right voltage.
Registered Member #4361
Joined: Fri Jan 20 2012, 12:46AM
Location:
Posts: 11
Thanks but I've got that solved. I used a IRF644 FET and protected it with a P6KE200 overvoltage protection zener (cathode to FET drain, anode to FET source). Normal zeners can't handle the pulse energy. Just to test it, i ran the coil without a cap. I'm puzzled now whey i couldn't get any pulses out earlier. I think the first coil may have been defective. Thanks for your help; you got me on the right track. I can now generate arcs about 2 cm long. Charts suggest this should be >20 kV. Good enough for my experiments. Now i'll add a monostable 555 pulse to drive the gate and it will provide consistent results..
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
It isn't possible for an ignition coil to output a single pulse - what you will get from a single input pulse will be a train of damped waves from the output, as we are talking L, C and R here.
You could sharpen this up a bit by placing a spark gap in series with the load if you wanted to.
Registered Member #3883
Joined: Fri May 13 2011, 06:30PM
Location: Norway
Posts: 87
If you tried to switch a coil mechanically without a capacitor you will loose most of the energy in the arc formed between the contact points. As the current is interrupted the voltage will increase instantaneously towards infinity, causing an arc at the low resistance primary side.
Registered Member #4361
Joined: Fri Jan 20 2012, 12:46AM
Location:
Posts: 11
Fulmen: I'm sure that explains the early failure I had. The addition of the capacitor you suggested made it work. Then the FET made it better. That also explains why a capacitor ("condenser" in US autos) allows an auto distributor to fire properly.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
Alternatively you can use 'capacitor discharge' to make a single pulse Charge a capacitor to about 300 to 400 Vdc then discharge it into the primary (You could use rectified ac mains (cautiously), a camera flash charger etc.) A thyristor would be a good switch for this purpose, a relay contact would work but wear out quite quickly.
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.
Need single pulse from ignition coil
