Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Making your own winding for auxiliary supply
Making your own winding for auxiliary supply
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 3rd March 2008, 07:58 PM   #1
rtarbell is offline rtarbell  United States
diyAudio Member
Join Date: Sep 2005
Default Making your own winding for auxiliary supply

Hello all,

In the interest of saving $, I have a basic toroid (~200VA, +/- 25VAC secondaries) for a gain clone amplifier.

I would like to add a basic microcontroller with pushbuttons to my amp for things like volume control and other low voltage housekeeping, but I don't want to add an extra transformer just for this. I only need a ~6V supply that I would be regulating down to 3V logic level.

One option I have is to just buy a cheap AC-DC wall cube. Another option I have thought of is to wind a few turns of regular wire around the toroid core to make a third secondary - then I could rectify that voltage and make my DC supply from there. When I say "wind a few turns to make a third secondary", I mean just winding the wire over the existing toroid, NOT removing the transformer tape, or anything like that.

Has anyone tried this before? I am not sure how much current I would be able to get from the core in this manner because the windings of the third secondary would be further away from the core due to the thickness of the other windings, the transformer tape, etc., and hence bad magnetic coupling.
  Reply With Quote
Old 3rd March 2008, 09:23 PM   #2
mag is offline mag  Switzerland
diyAudio Member
Join Date: Jan 2008
Location: Chiasso
Hi if you need only some mA to power up logic stuff just wind
some wires around the toroid. No need to disassemble it, just wind them over the tape. You can even use a standard plastic insulated wire.

Start with 10 turns and mesure the AC voltage across the wire than adjust the number of turns to reach your desired voltage.

If you need 3V for logic stuff try to have something around 5-6V AC. For rectifying you can use a simple 1n400x diode and a 470-1000uF capacitor. It becomes 7-8V DC on the capacitor.
Then regulate that voltage using an LDO like LM317 or others LDO of your choice.

A small fuse on that winding will be a good idea, if you short it, even if it is not so tightly coupled with the primary you will have enough current to burn the wire....
  Reply With Quote
Old 4th March 2008, 08:36 AM   #3
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
Mooly's Avatar
Join Date: Sep 2007
Making your own winding for auxiliary supply
How about a "Watt-less Dropper". Use the reactance of small caps in place of resistors and run direct of the secondary. A couple of caps and diodes is all that is needed plus a regulator (3v3 zener ?) and a resistor or two. All depends how much current you need as to whether this is viable.
Regards Karl
  Reply With Quote


Making your own winding for auxiliary supplyHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
NICE; Custom 250VA Toroidal Power Transformers; 34vac/7a, plus an Auxiliary Winding dozer Swap Meet 0 19th January 2009 10:10 AM
ucd400: Hypex HXR12 Regulators vs. Input buffer auxiliary supply jdec Class D 1 23rd December 2007 06:52 AM
Using existing transformer winding to provide and additional supply BL21DE3 Tubes / Valves 3 23rd October 2007 12:56 PM
active crossover power supply pcb check before making mazurek Solid State 20 2nd May 2006 01:17 AM
Auxiliary power supply idea JohnG Solid State 4 29th April 2002 05:18 AM

New To Site? Need Help?

All times are GMT. The time now is 10:43 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio