Author Topic: DIY toroid kits  (Read 3375 times)

emrr

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    • http://www.emrrecorders.com/
DIY toroid kits
« on: October 08, 2008, 06:31:25 PM »
Saw this bit on the Ampex list, and was intrigued.   Hadn't heard of them before.

Quote
I just received two torroidal power transformer kits... yes KITS,
from Torroid Corp of Maryland. They give you a pre-wound primary, and
instructions for putting your own secondary(ies) winding(s) onto the
core. No wire supplied for the secondary since that's load dependent.
Instructions are very complete, and there's tables to help you ensure
that your secondary will actually fit. Mylar tape to insulate the
finished winding(S) also included.

There are multiple core sizes available; you pick that when you
order. Price for an 80VA core was $30.

There is a 250v RMS voltage limitation between any two windings.
Quote

I have used the kits from both Plitron and TCM and they are both very good, BUT
they are still relatively expensive and if you want a B+ winding there are a LOT
of turns to put on.  It is much cheaper to tear the secondary off an existing
toroid and wind a new one on although it can require a little cut and try work
to figure out how many winds are on the primary.
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounded g


owel

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  • Nashville, USA
DIY toroid kits
« Reply #1 on: October 09, 2008, 12:23:01 AM »
Cool.

Found the link...
http://www.toroid.com/standard_transformers/transformer_kits/transformer_kits.htm

Quote
Each kit contains:

Transformer Kits Datasheet
    * A toroidal core of grain oriented steel
    * Mylar taped for insulation of secondary windings put on by the customer
    * Built-in thermal fuse rated at 130C
    * Manual with step-by-step instructions on how to design and wind the secondary windings.
    * Metal washer and 2 rubber pads for mounting the transformer
    * Guide to calculate proper wire size and length required to generate your calculated output data.


For $30 as a learning tool, it could be a fun and easy way to learn more about transformers and get my feet wet.... hmmm, electricity and wet feet, okay that doesn't sound right.

You know what I mean.

CJ

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  • California
DIY toroid kits
« Reply #2 on: October 09, 2008, 04:31:46 AM »
As much as I love DIY, and as much as I love transformers, I still would not buy that kit.
Why?

For one, it's always a little spooky when you mess with the mains

Two, power transformers are cheap

Three, you can wind a good transformer with that kit, but it will not be dipped in epoxy.

You need to pull a vacuum on a transformer to get rid of moisture that will corrode wire and insulation, then you need to do a modern varnish impreg, then you need to bake it.

Also, you want the power trans to have a company attached to it so you can sue them when your UL Listed xfmr burns up and takes down your apt complex.

Do you have renters insurance?

For just pennies more, Geico Direct can set you up....
If I can't fix it, I can fix it so nobody else can!
Frank's- www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar- http://tdsl.duncanamps.com/schematics.php

wtmnmf

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  • Berkeley,CA USA
DIY toroid kits
« Reply #3 on: October 09, 2008, 09:28:19 AM »
Sounds like a cool kit to me.

Vacuum and epoxy?  No problem.  Standard stuff in composites manufacturing. Lots of DIY sources for it.

Suing a transformer manufacturer?  Good luck with that!  I was buying isolation transformers from Xentek for a medical instrument that directly stimulated the human heart.  These guys mis-wired about half of the transformers that I received!  Some had 450v on the case  :shock:.  When informed, they just shrugged their shoulders.  They stuck every agency approval sticker on the things and signed off on the testing when they clearly were not testing the product before shipping.  BTW, it takes about 50ma at 60hz to stop the heart. The upshot is that they are still in business and have not lost a nights sleep over this sort of thing. I think a little apartment fire would trouble them even less  :roll:


I'd worry more about the unprofessional wiring that's hidden in the walls!  Now that's scary!

emrr

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    • http://www.emrrecorders.com/
DIY toroid kits
« Reply #4 on: October 09, 2008, 11:53:32 AM »
i just thought it was cool you could even buy such a thing.  Not that I have a need.
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounded g

Gareth Connor

  • Guest
DIY toroid kits
« Reply #5 on: October 10, 2008, 04:31:00 PM »
Why is it spooky to mess with the mains? If you are building equipment that is mains powered, you have to get involved with 110V / 220V at some point. I personally am more worried about putting mains on open PCB traces than winding transformers..... and my aversion to mains on PCBs applies to professional equipment as well as home-made.

Power transformers are cheap, but how many come with 2 x 18V, 1 x 8V and 1 x 45V secondary as standard? Custom toroids are also relatively cheap when buying 20+, but a one-off costs a bit.

What's the problem with un-dipped, non-epoxy transformers? There are MANY professionally manufactured transformers that are both - suppliers and website addresses will be provided on request.

"Moisture will corrode wire and insulation". In all honesty, this is a first for me! I have numerous reels of enamelled coil winding wire that have been in my workshop for anything between 1 year and 30 years, and so far none of them have any signs of corrosion.

A specific example of a DIY toroid: In 1987 I added two windings to a toroid to provide additional voltages to the 2 x 18V that it came with. This was a one-off for a briefcase-size portable mixer I made for a client. The mixer is still going strong (as is its un-varnished, un-dipped and un-epoxied transformer). Every couple of years the client brings the mixer in for a check-over, and as with any good, competent, thorough service, the power supply is tested for technical performance and safety...... it has never failed either.

Now, in 2008, the business has grown so that for several years I have not made 1-off toroids - not because of any safety issues, but because the cost in time is too great. It is cheaper to get a custom transformer made.

CJ

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DIY toroid kits
« Reply #6 on: October 10, 2008, 06:33:04 PM »
Stolen off the web:


"Examples illustrating the impact of
water on the lifetime of a transformer:
• Moisture increases in paper from 3% to 4% causes aging
similar to a 6 to 8°C temperature rise.
➔ A dry transformer can withstand more load without
reducing its lifetime.
• Indicative lifetime of insulation @ 80°C:
40 years if 1% moisture in paper
10 years if 3% moisture in paper"

Usually the noisiest chunk of iron on your DIY chassis will be the pwr trans
50 or 60 cycles is, as you know, is well within the audio range.
Another noise-producing phenomenon in power transformers is the physical reaction force between primary and secondary windings when heavily loaded. If the secondary winding is open-circuited, there will be no current through it, and consequently no magneto-motive force (mmf) produced by it. However, when the secondary is "loaded" (current supplied to a load), the winding generates an mmf, which becomes counteracted by a "reflected" mmf in the primary winding to prevent core flux levels from changing. These opposing mmf's generated between primary and secondary windings as a result of secondary (load) current produce a repulsive, physical force between the windings which will tend to make them vibrate. Transformer designers have to consider these physical forces in the construction of the winding coils, to ensure there is adequate mechanical support to handle the stresses. Under heavy load conditions, though, these stresses may be great enough to cause audible noise to emanate from the transformer.

I'm just sayin...
If I can't fix it, I can fix it so nobody else can!
Frank's- www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar- http://tdsl.duncanamps.com/schematics.php

AudioJohn

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  • Posts: 174
  • Exeter UK
    • http://www.orchid-electronics.co.uk
DIY toroid kits
« Reply #7 on: October 17, 2008, 02:31:25 PM »
We are probably very lucky in the UK with a fairly benign climate - think about the tropics - or the Carribean, or anywhere with  high humidity.

Apparently standard devices - such as FAX machines and copiers just do not last in this environment.

In this day and age of the need for cheap components - true vacuum impregnated varnished windings are not very common on the usual catalogue bought transformers.

I will be interested in the experiences of folks from less than dry climates and anyone who exports equipment for use anywhere in the world......

bitman

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  • Posts: 482
  • Keystone, Colorado
DIY toroid kits
« Reply #8 on: October 19, 2008, 06:09:39 PM »
Quote from: "CJ"
As much as I love DIY, and as much as I love transformers, I still would not buy that kit.
Why?

For one, it's always a little spooky when you mess with the mains

Two, power transformers are cheap

Three, you can wind a good transformer with that kit, but it will not be dipped in epoxy.

You need to pull a vacuum on a transformer to get rid of moisture that will corrode wire and insulation, then you need to do a modern varnish impreg, then you need to bake it.

Also, you want the power trans to have a company attached to it so you can sue them when your UL Listed xfmr burns up and takes down your apt complex.

Do you have renters insurance?

For just pennies more, Geico Direct can set you up....


You funny. You make a me laugh.  :grin:


 

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