Ultraviolet rays are also good creating melanomas in your skin.
You should know enough to know the difference between UVA and UVB if you want to give useful advice, which is beyond NT's capabilities, if not perhaps beyond the capabilities he claims.
-- Bill Sloman, Sydney
If you have a fluorescent fixture that won't start, hold the output end up to the tubes. I've gotta replace the tubes and/or ballast eventiually, but the Zerostat (another kind of sparker) is still starting my basement lights at need.
Violet rays don't emit ultraviolet. Fool.
NT
For this application air-core coils would be best. They melt, but not saturate. You can minimise their count by tapping. 250uH made of 1mm wire is not very big, 4cm OD or so. I wound several of them for surge suppression. The small inductance ones can even be air-core toroids.
Best regards, Piotr
The compact nanoperm-based ones saturate at even lower currents than those wound on a ferrite core. This crazy permeability doesn't come for free. And their hi-freq permeability sucks even more.
}:->
Best regarads, Piotr
Obviously not. The violet end of the spectrum extends into the ultraviolet.
The violet band that you can see isn't exactly active, so the foolishness is all yours - as usual. More transparently so than usual.
-- Bill Sloman, Sydney
OK, I'll try some math on air-cores.
Looks like drum cores might work:
Lots of air gap, lots of cooling area, Isat>Irms. It will spray h-field in all directions, but that would be OK in my application. It's BIG.
I'm thinking about a single 1 mH coil, then synthesizing the rest of the inductance.
A couple of off-the-shelf toroids in series would hit 1 mH with that sort of saturation. Then I could offer 500uH or 1 mH as the switched "real" inductances.
Lots of inductors are like ceramic caps, only providing the specified reactance at a fraction of the rated voltage or current.
Although they make some that they claim higher saturation current (like up to 40mAt) for; or rather, a softer B-H curve.
There's also square B-H varieties for magamp use.
The HF permeability sucks in that it begins dropping at quite low frequencies: a half-corner ~10kHz, then a full corner ~1MHz.
It's overall better than any ferrite, particularly at low frequencies. And if you have a lot of noise to handle, Bmax is also much higher. Awesome stuff. :)
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
I've also used a drum. If you fill this with TIW 1mm, you'll get 250uH. This is 42mm in diameter, is it big? Don't know your criteria.
About the size of mine and the saturation current is only 6.5A. Is it worth playing with the ferrite at all? Double the number of turns of mine and you'll get your 1mH.
All non-air core ones are like this. Alloy powder are particularly notorious, but it is not a problem, if you design taking it into account. My last PSU uses one with 4:1 swing and this is even an advantage.
Best regards, Piotr
Working with one 2.5 mH coil of the Schaffner inductor, it loses about half its inductance at 90 mA DC. Not good enough for my application, but still an interesting part.
As a pulse transformer, 50:50 ohm rise time is about 200 ns! Could be a gate driver.
On a sunny day (Mon, 19 Aug 2019 10:22:20 -0700) it happened John Larkin wrote in :
they make pulse transformers etc..
time wasting idiot plonked
NT doesn't like being outed as a twit.
-- Bill Sloman, Sydney
My measurements of the 16mm cores indicate about this saturation current, so it is an experimentally confirmed value.
Have never been able to buy one for prototyping. The 3R1 is all I have, but my experiments show that low-signal magamps work tollerably well even with normal ferrites like the F938. Very forgiving technology.
Oh, so *that* is the reason! Makes sense, thanks!
Best regards, Piotr
You may have some and not know it! The old school ATX power supplies derived the 3.3V supply from the transformer's 5V taps, using one tap directly and the other tap controlled with a magamp and TL431. That's why the 3.3V is so damn accurate (within 10s of mV) while everything else is a sausage!
Typically the component is black ferrite, or plastic-cased nanocrystalline strip, 4-5 turns, and may be wrapped in heat-shrink.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
That's most likely the 3R1:
I would not expect a nanocrystaline ribbon in a Chinese PSU. Would probaby constitute a half of its price. :->
Best regards, Piotr
Maybe. Or maybe the supplies I took apart weren't sourced from China, who knows. Here's a few, with some other specimens for reference:
I don't think I have any square ferrites in here (actually, I probably do, but haven't measured them to be sure, and none that are obviously gooped with varnish), but I have a few beheatshrinked inductors in another box that appear to be ferrite, most likely the 3R1 or something closely related. I've seen both, definitely.
The amorphous/nanocrystalline cores can be easy to miss; the black one is thick and square and has a middle seam, but could easily be mistaken at a glance for black ferrite, especially with the varnish gooped on it.
That's probably a 15k mu ferrite, top left. Apparently they'll put ferrites in plastic boxes too (presumably for the creepage distance to core?). So I included that too, without the box obviously.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
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