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 #7222
Joined: Sat Oct 13 2012, 06:04AM
Location:
Posts: 18
Hi Guys,
I'm in the middle of building my first ever Solid State Tesla Coil. • I'm using a modified version of Steve Wards Micro tesla coil. o Using a 12 Turn GDT like his MINI using a Single UCC37322 o Single IRFP460 to do the power switching o 75VDC primary (Using a doubler from a 250watt 24ac transformer) o Using a Feedback Transformer instead of an antenna → cleaned up by a 74hc14 hex inverter.
TESTING suitable Cores I have tested a variety of cores and picked one, which I though was suitable (out of a microwave oven filter circuit I have no idea what material it is but believe it to be ferrite)
How I tested the Cores: • I used a oscope probe hooked up to the function generator to the primary side of the GDT to be tested • I then used another oscope probe into my CRO to look at the resulting waveform.
I Believe it wasn’t the best way to test a GDT as of the impedance of the probes? is this correct ?
Testing Driver board with GDT I've constructed the driver board and have now run into some problems with the GDT. After switch on the amplitude of the resulting waveform increases for a few seconds, then swings massively, overshooting the limits of my cro's screen. At this point either the UCC37322 or GDT becomes audible and the chip gets hot fast :/ and I think it when poof too :(
• Testing was done with the output of the GDT to a 10ohm (and on another occasion with a 2.7 ohm resistor in parallel) with the probes of my scope across these terminals. • My function generator can only achieve 200khz although I believe the 555 timer kicks Ucc37322 into oscilation at about 300khz.
Is the Core Reaching Saturation? How should i go about testing for issues ?
Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276
I have had similar things happen to be. This will be because you are using the incorrect core. You want a ferrite one and i do believe this is iron powder.
I cannot, however, remember what core everyone uses more or less...
Registered Member #30656
Joined: Tue Jul 30 2013, 02:40AM
Location: UK
Posts: 208
Core in the pics looks like ferrite, but the best way to test is to try and use a file on it. Iron powder will be easily cut by the file, ferrite will chip (it's a ceramic) and if you keep going will blunt the file.
Registered Member #42796
Joined: Mon Jan 13 2014, 06:34PM
Location:
Posts: 195
That core looks like a EMI suppression core which is not suitable for that frequency but people managed to pull it off with even worse cores....
From your description and pictures i see a logic signal (0 - Vcc) fed into the gdt and since there is no DC blocking cap between the ucc and gdt a DC component is always present which is saturating the core and causing all the problems described.
Easy fix pace a 0.1uF or higher polypropylene or ceramic (better) capacitor between ucc and gdt - C6 on Steve's mini SSTC schematic
Registered Member #30656
Joined: Tue Jul 30 2013, 02:40AM
Location: UK
Posts: 208
element14 (formally known as Farnell) is worth looking at, I know they stock some FairRite cores, though not at amazing prices. Other than that, try RS (also likely to be expensive but with low shipping cost), or do a bigger order at Mouser or Digikey to get the free shipping.
As an aside, I feel your pain over shipping costs, NZ is just as bad, and our GST threshold for imports is a lot lower too (400 NZD vs 1000 AUD).
Edit: For the record, I've gotten away with using EMI suppression ferrite toroids for gate drivers (didn't have anything better on hand) - seemed to work fine, but isn't ideal. I just wound 10-12 turns of CAT5 though it and was away laughing. The DC blocking cap is important!
I believe you have access to Digikey down under, a good friend of mine mentioned ordering from them and he lives in NSW.
I use these cores in all my SSTC work, and they perform flawlessly up beyond 1MHz and down to 30Hz. I've driven large capacitive gates quickly with no issue or sign of saturation.
Registered Member #30656
Joined: Tue Jul 30 2013, 02:40AM
Location: UK
Posts: 208
Sigurthr wrote ...
I believe you have access to Digikey down under, a good friend of mine mentioned ordering from them and he lives in NSW.
Yeah, we can get parts from Digikey/Mouser fairly quickly and easily, it's just not always cost effective for small orders. If we use the US site (in USD) we pay $30 USD for flat rate shipping, and if we use the local NZ/AUS sites the prices are 10-15% higher but with free shipping on orders over ~100USD.
$30 USD is actually very reasonable for fedex express (fedex can get well into the hundreds shipping small-medium boxes to AUS/NZ), but if you just want to quickly grab a few parts it's very frustrating.
Those cores look good by the way, thanks for the info!
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.
GDT HELP
