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
To answer your first question: No you can't connect what you call the "-12V end" of the secondary straight to ground. That would be a half wave rectifier with no flywheel diode, it would blow up. You have to use a four diode bridge like I already said twice.
If you do that, you'll get the same current as was available from the +12 but twice the voltage. As pointed out, the "negative" windings don't have thinner wires because there are no negative windings. The whole thing is symmetrical about the centre tap, and the two ends take it in turns to be positive and negative.
Re breaking the centre tap: I've done the opposite, take two windings that were in parallel and bodge them in series, to convert a 5v power supply to 12v.
Registered Member #4357
Joined: Thu Jan 19 2012, 05:32PM
Location:
Posts: 8
m4ge123,
Wow!! Do I really come across as that much of a noob (maybe because I'm a "yank", I'm also a wanker...big grin ;) I do understand that the output of the xformer is an AC kind-of signal (certainly not pure sine wave), and that the + and - voltages could be generated from pretty much any of the taps or "ends". I was using "-" and "+" mainly to provide a reference to the windings.
Thanks for confirming that windings on both "sides" of the CT can carry the same amounts of currents.
Steve,
Either my question is being misunderstood, or I'm making the mistake of treating the xformer secondary of a switching supply as I would the secondary of a xformer for a linear supply. I thought they were similar in function and nature except for the frequency.
Re: "flywheel diode"...I thought those were typically used in buck and boost circuits. My sense is that the "flywheel" action takes place on the primary side in a switching supply. The secondary then delivers a high frequency (>>60 Hz) alternating voltage/current and the secondary diodes create the DC. Then the series inductors and caps smooth out the noise. Maybe I'm missing something here again.
Re: Breaking the CT. Yeah, I've bought xformers that provide 2 separate but same secondaries: Series - double the voltage, parallel - double the current.
Again, thanks for your patience and for confirming winding current capacities and voltage modification results.
Registered Member #4357
Joined: Thu Jan 19 2012, 05:32PM
Location:
Posts: 8
Hi all,
I just figured out how much of a doofus I've been :) I was having difficulties understand why some of the feedback and comments seemed sort of...non-sequitur....
I had examined SMPS schematics that weren't ATX style and the secondaries of those were typically half-wave rectifiers. I didn't take a closer look at ATX-style designs until last night and I realized the DC outputs use a full wave DC rectifier circuit. Explains some of the comments about shorts and less power available, etc. (In one of the postings someone mentioned mixing up 1/2 wave vs. full-wave...I should have taken a lead from that).
Anyway, it now all seems much more clear (now that I'm on the straight and narrow :) Just need to figure out what I want to do and sort thru the best way to get there.
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.
Hacking an AT/ATX power supply....
