inductor for HV flyback supply

• Almost blank page is not exactly conducive to learning...

Sure. They linked back to my old Dutch web-site that no longer exists.

I think I've fixed the duff links, but until my Australian IP up-loads the corrected files, probably in the next few hours, I won't know.

y, expensive, sub-optimal solutions.

ng than

ve never bothered to get your head around all the issues involved, and find yourself embarrassed when you have to discuss a transformer design in fron t of your subordinates.

size and core material, gapped or ungapped, and proceeding through turns ra tio and wire size, and choosing between plain wire and Litz, and on to wind ing configuration - bifilar or separate coils - plain windings or winding i n banks (for lower parallel capacitance).

thing all that close to optimal. The process of getting small runs of custo m transformers made by sub-contractors isn't all that demanding - no worse than printed circuit boards. It's nice if you can avoid it, but little more sensible than it would be to insist of building everything on off-the-shel f printed circuit boards.

True, you cannot beat the performance of a custom design.

But, for a given converter, you may be able to get so close performance wis e to the custom design using an COTS part, which will be a lot easier and m ay be cheaper

For low volume, the hassle and NRE cost of getting a custom part UL approve d part, often results in the selection of the COTS part

Cheers

Klaus

Usually, you can. You can generally get a product finished with standard parts for a fraction of the cost, in a fraction of the time. Needing custom magnetics may be a character defect, a lack of imagination. Or an irrational desire to design magnetics.

If you plan to build 30,000 power supplies, custom magnetics may make sense. If you are designing a complex instrument and need some transformers or inductors, try Coilcraft first.

Sloman loves custom magnetics, which explains why he has been working on his beloved oscillator for over a decade, and it still doesn't oscillate.

Tne reason I dislike custom magnetics is because I've done so many custom magnetic designs, probably 20x more than he has. The best inductor is cheap, multi-sourced, surface mount.

This one doesn't qualify:

Wow, Cthulhu the transformer. Now, too late, you know what strange and forbidden rituals those web monkeys were up to in the back of your shop. ;)

Cheers

Phil Hobbs

That looks complicated.

I'd worry that it gains consciousness and runs away.

Looks like a giant steel and copper octopus that lurks under your bed.

I do like the colorful trimmed wire bits, great to have around the house.

Yes!

Now, too late, you know what strange and

They finally gave up on the yet-another-social-thing-web-app, returned the remaining money to the investors, and got jobs. M is now the engineering manager of a cubesat company a few blocks away (there are two cubesat companies a few blocks away!), trying to inflict some order on them.

essy, expensive, sub-optimal solutions.

oring than

ou've never bothered to get your head around all the issues involved, and f ind yourself embarrassed when you have to discuss a transformer design in f ront of your subordinates.

re size and core material, gapped or ungapped, and proceeding through turns ratio and wire size, and choosing between plain wire and Litz, and on to w inding configuration - bifilar or separate coils - plain windings or windin g in banks (for lower parallel capacitance).

anything all that close to optimal. The process of getting small runs of cu stom transformers made by sub-contractors isn't all that demanding - no wor se than printed circuit boards. It's nice if you can avoid it, but little m ore sensible than it would be to insist of building everything on off-the-s helf printed circuit boards.

That's beating the cost of a custom design, not it's performance.

More likely the the lack of an irrational desire not to design magnetics, c oupled with with the intellectual capacity to do it.

Always worth doing, but expect to come up empty most of the time.

wise to the custom design using an COTS part, which will be a lot easier an d may be cheaper.

oved part, often results in the selection of the COTS part.

The oscillator project started - in a sense - back in 1986, and that oscill ator has been part of a single-crystal GaAs pulling machine ever since.

The wound parts got dumped last year when it became clear that even a well- gapped ferrite core was going to introduced harmonics 105dB below the funde mental.

If it will do the job you want. Most won't.

Looks like a power transformer. I've designed similar-sized power transform ers into arc-lamp power supplies, but we used used graduate students to man

-handle them onto the chassis.

We get "solderable" magnet wire from MWS. Stripped and tinned in a solder pot. Nice stuff.

George H.

llator1.htm

stitute ought to have a simple coil winder - there are cheap ones available from China if it doesn't - and you don't need much of a range of RM cores, formers, mylar tape and enamelled wire to do useful stuff.

ed circuit shop to get useful copper fill factors. I talked to one in the N etherlands, but didn't get to the point of having anything made - that woul d have been for a better electric piano keyboard, but I couldn't get the Li nux mechanical drafting program to do anything useful, and tossed it all in to the too-hard basket.

-lag today, and my wife won't be back until Monday, so I might get it done over the weekend.

le better in the next few hours.

I finally seem to have fixed all the links on my web-site. The obvious prob lem was that several of them were linking back to my old Dutch web-site, bu t when I corrected that I seem to have managed to get the file names subtly wrong - spaces where there should have been under-scores, and one file wit h the extension .html where I'd named it .hmt when I'd called it.

Nothing difficult, but tedious. And the better scan of the 1959 Baxandall a rticle is there too.

Win, small world--looks like I have a similar requirement.

I did a bit of magnetics-scrounging, finding hits under 'coupled inductors,' and 'flyback transformers.'

Interesting specimens: (DigiKey) Pulse PA0367A: 9x9mm (case) 12x12 footprint, SMD, 1:12, 18uH, 500V, $2 TDK ATB322524-0110-T000: 1210 SMD, 1:10.2, 7uH, 500V insulation, $1 qty 1

Other candidates: o CCFL transformers are quasi-interesting for forward converters. o Xenon strobe transformers are classic flybacks roughly in this ballpark. o Coilcraft Hexa-Path,

Cheers, James Arthur

I use aspirin to melt the enamel, and solder 0.1 mm wires no problem. It looks like you don't know that trick. (You must use acetyl salicic acid, the brand. just any pain killer won't do. No mixins.)

Groetjes Albert

Use Beldsol enameled wire. Just solder it with a hot iron.

I've a similar litze wire for my Boehm self built organ. Use Weller 8 tips instead of 7, and tin-lead solder. It was 17 guilders at the time (1980) for 90 meter. Boehm had all kind of secondary supplies (meters, resistors, etc.) for cheap, and unbranded. Maybe this was Beldsol. It is litze, enamelled and then wrapped in secondary isolation.

Got 61*10+61*10+30*10 solder points in that organ and then some. This clearly was for easy connection not wire for transformers, with small added benefit for soldering.

I still have a spool, which will last my life time, unless I dream up some weird project.

Groetjes Albert

How is that accomplished? How do you coat the wire with the aspirin? Do you melt the aspirin with your iron first? What is your process?

Thanks.

Beware reading posts on the internet about using Aspirin as flux, and they trying it out! I did those things, and the stink was incredible. I had a sore throat for a while after that. If you do try it, use fume extraction!

There are many brands of polyurethane insulated winding wire that can be soldered through, but it helps if the iron is a little hotter than usual. The hotter iron and longer soldering time can damage things if you are trying to simultaneously tin the winding wire and also solder it to a pin of a plastic coil former that can melt easily. Pre-tinning the winding wire would be one option. If the wire is thick enough that you can scratch the enamel with a blade before tinning it, that works more quickly as the hot solder can heat the copper of the wire directly. Also it is quicker to tin the end of a wire than the middle, because again the hot solder can contact the copper at the cut end and heat it more easily.

Beware the TDI (Toluene Di-isocyanate) from the burning enamel. It hurts your eyes and is generally nasty. Use fume extraction if you are doing a lot of it.

In the Netherlands similar wire was known as "Posijndraad", I'm not sure if Posijn was a manufacturer and where it was based. I made quite some digital circuits in the past with this wire and breadboard-type PCB (1/10" spaced holes with a copper island per hole). Indeed it was easy to solder with a number 8 tip, without having to pre-tin the ends of the wire. I just wrapped the wire 1 turn around the IC pin (continuing to the next pin when required) and soldered those junctions.