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 #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
The secondary is so high impedance that the 100 ohm resistor is damping it. Try connecting the generator straight to the primary, and the scope to the secondary. But be careful, if your transformer is really good it could blow up the scope
Food for thought: 40kV/0.3mA = about 120M ohms Input impedance of 10:1 scope probe: 10M ohms
The scope probe is a 12 times heavier load than you specified the transformer to drive
The secondary is so high impedance that the 100 ohm resistor is damping it. Try connecting the generator straight to the primary, and the scope to the secondary. But be careful, if your transformer is really good it could blow up the scope
Food for thought: 40kV/0.3mA = about 120M ohms Input impedance of 10:1 scope probe: 10M ohms
The scope probe is a 12 times heavier load than you specified the transformer to drive
is there a safer way to do it with out having to turn on the HV to find out the correct frequency that I should run it?
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
you can drive the primary with the sig-gen and monitor the output voltage by capacitive coupling; earth/ground one end of the secondary and hold your 'scope probe near to the secondary output wire, you should be able see the resonance of the un-loaded secondary.
Now add capacitance to the output to simulate your load (or add the actual intended load) and see the new lower resonant frequency that your circuit will have to operate at.
you can drive the primary with the sig-gen and monitor the output voltage by capacitive coupling; earth/ground one end of the secondary and hold your 'scope probe near to the secondary output wire, you should be able see the resonance of the un-loaded secondary.
Now add capacitance to the output to simulate your load (or add the actual intended load) and see the new lower resonant frequency that your circuit will have to operate at.
so if I do this instead of blowing up the mosfet I would burn the signal generator, :)
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Andre wrote ...
the pulse generator is on the secondary in parallel with a 100ohms resistor
I'm sure I said in series, not in parallel. I assumed you'd set the sig. gen. to sine wave, not square wave. The 100 Ohm series resistor is to protect the sig. gen.
(I'm no expert, but that is what I'd do.)
EDIT: I've a hunch you may need to short the primary, but ask the experts.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
so if I do this instead of blowing up the mosfet I would burn the signal generator, :)
no, every sig-gen I've come across can withstand a short circuit on the output, and there is no external source of power into the sig-gen output. If you're concerned put the recommended load resistance in series with the output,
Another way is to just apply an impulse to the primary (battery with series resistance) and watch the resulting 'ringing' on the secondary at it's resonant frequency.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Sulaiman wrote ...
no, every sig-gen I've come across can withstand a short circuit on the output, and there is no external source of power into the sig-gen output. If you're concerned put the recommended load resistance in series with the output,
My si. gen. has a reccommended load of 60 Ohms, but I use 100 Ohms for the series resistor just to be on the safe side.
When finding resonant frequencies in LC circuits, I assume the voltage can rise as in any other resonant LC tank circuit (I've seen this on my 'scope), so some protection for the sig. gen. may be advisable?
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.
burning Mosfets
