What matters is electronic design. The "electronic" thing is the easy part; most any college will teach you the mechanics of that in four years, more theory than you're likely to need. The hard part is "design", which involves branching out, exploring strange possibilities, understanding a lot more than the theory, riffing on silly ideas in all directions, alone or with others, hoping to evolve or stumble on a gem.
Namely, design involves doing the things you consider to be "intentionally devious" and "bobbing and weaving."
I totally agree with your second stage design. When I stated "60 Hz hat", I meant the core material can be 60Hz material but the corner frequency is still up at maybe 30KHz with low parasitic capacity to get the required
200KHz attenuation. As we both stated 60Hz THD requirements must be meat with loop design. Wima caps are a good alternative but cost will start to soar. As for air cores, I do not disagree with anything you have stated above. but size matters to further this discussion. The current levels are very high, wiring loops areas must be keep as small as possible so they no not act as primaries nor secondary windings. In so doing the inductor is in very close proximity with many other windings with no room for shielding. I would be very interested in the size of the air core inductor compared to the gapped ferrite which is about a three inch cube. The self resonate frequency, which I will calculate for the ferrite, would be an interesting data point.
--
Not at all, and unless you\'re very naive, you know very well that\'s
not what I\'m talking about.
What I consider to be intentionally devious is when you make a
statement like, "Namely, design involves doing the things you
consider to be "intentionally devious" and "bobbing and weaving." in
order to try to save face and steer the discussion in the way you
want even though you know there\'s no truth in what you say when you
try to make it seem like being intentionally devious and bobbing and
weaving are part of the design process.
It isn\'t, and that\'s not for me.
As far as I\'m concerned, design is the search for truth and
deviousness and bobbing and weaving have no welcome place along that
path.
YMMV, since you seem to define deviousness and bobbing and weaving
in terms other than those generally accepted.
As I said, what I consider to be the design process is what you seem to define as "intentionally devious", which you have now further morphed into "ill-gotten." This gets better and better.
We design and build electronics. We have specs, manuals, and a price list. If people want to buy our stuff, they can; if they don't like the price, they can shop around for a better deal. If they want to try a loner, to see if it works as claimed, we provide one. If anything goes wrong, we fix it fast. If the customer isn't happy with one of our products, we take it back and refund all their money. If they ask a question, we tell them the truth.
The design part is a lot more "devious", but that's not the customers concern. The customer pays for a product that performs a function. Since we never sell designs, only products, so the customer has no reason to see the process.
But I'm excessively proud of myself today. I learned how to mud sheetrock, and it came out pretty good.
Does an air-core toroid make any sense? I don't think I've ever seen one. Micrometals does have a no-op core material, u=1, made out of phenolic or something.
Yes, but I believe the advantage is small enough that it seldom outweighs the additional complexity of implementing the winding. In an air-core solenoid coil, it's rather interesting how low the coupling is between the first and last turns in "typical" RF coil geometries--where the coil length is commonly equal to or greater than its diameter.
Hey Tom, are you going to give us a size and SRF estimation of the air core inductor needed in the above filter. I have calculated the SRF of the ferrite inductor to be 5.75MHz +/-20%. It would be nice to have a Rac at
200KHz number also, the ferrite should come in at Rdc< 8.0mR and Rac< 15mR. Isat is >75A for the ferrite. What say you, Harry
Yep, I agree size does matter. I should perhaps clarify what I said before about it being unlikely I'd actually build a supply like that with an air core coil: if I did, it certainly would be a one-off experiment, and not something I'd contemplate putting into production. Since in some of my spare moments I'm playing with a supply at about the 2kW level and about half the OP's supply voltage, I may try pulling out my toroid inductor and putting in an air core coil. I'm sure I'll learn a thing or two from the 'speriment. ;-) And of course, the times I learn the most are when I discover the error of my ways -- so when I try things that "shouldn't work" I do tend to learn a lot.
I only have an easy way to calculate expected resonances for single- layer solenoid coils, but for a 10uH 20 turn coil of 12AWG 1.665 inches long (about 3 mils between turns; essentially close-wound enameled magnet wire), the predicted first parallel resonance is
39.3MHz and the first series resonance is 62.6MHz. 1.62pF effective parallel capacitance. The closeness of the turns is probably pushing the program beyond where it's intended to be used, so that may be in error some.
I looked through the quoted material in your posting that I've replaced with "..." above and didn't see an inductance. What inductance did you do that estimation for? You've perhaps seen my estimate for a particular coil which is probably not very close to what you've estimated, so in the interest of comparing apples and, um oranges instead of apples and hedgehogs, ...
The 10uH coil I mentioned in my other recent posting would be about 12 milliohms DCR; I expect Qu in a coil that size and at that frequency, wound with optimal Litz wire, to be around 150. "Isat" doesn't have much meaning for an air core coil, though losses-->heat will limit the maximum operating current. I'm curious enough about this now that I'll see if I can hack a coil and do a quick-and-dirty measurement tonight--at low power, of course. I do wonder at your Rac a bit; if it's for a 10uH inductor, it implies a Q of over 800 at 200kHz. Seems a bit high.
--
Of course that\'s not what I meant, as you well know, and your
attempt to redefine "intentionally devious" into an acceptable
design process is disingenuous, at best.
But that seems to be the defense mechanism you employ in order to
try to deflect commentary which you consider to be damaging.
For example, what I was referring to wasn\'t the design process, it
was your response to criticism, which you generally respond to by
changing the subject or responding to the criticism flippantly in
order to try to make the criticism also seem flippant.
Damaging? How the hell could you ever damage me? Don't be absurd.
I reserve the right to make fun of anybody or anything. You can reserve the right to be as prissy and grim as pleases you. Fair enough?
I figured out a long time ago that, if you sell engineering, you only get paid for it once. If you design and sell products, your manufacturing people can replicate hundreds, or in some cases thousands, of copies, and you get paid for every one. It's like what the military call "force multiplication."
My body will be unsuited to sheetrocking long before my mind is unsuited to design. As far as the sheetrock thing goes, my body is over the hill already. But my wife has decided to start her own business, and rented an unfinished space to start up in, so we're doing it up...
formatting link
This is owned by a lady from Seattle who constructs buildings with a few hundred small offices each, and rents them out month-to-month. They provide power, security, wi-fi, parking, and a really cool environment. It's a bare room that you finish and decorate however you want. It's mostly artistes and startup small biz, so I suspect there's a lot of turnover. It would be ideal for a very small electronics startup or something like that. This should be fun.
But as far as fallback goes, that's another advantage that selling products has over selling design. If I quit today, my company could keep selling what we have for 5, maybe 10 years.
Yup, as long as you will get paid for every copy, forever. That's actually better than manufacturing copies of your IP... let somebody else do it. We license two products, one an electrical power metering/datalogger box, and one an eximer laser controller. Support is minimal, and the checks keep coming in.
Yup. The tools and toys that are available nowadays, like right out of the Digikey catalog, are astounding.
They're cheap because it's generally impossible to get them to meet their original specs the second time. Still, 1000x better than nothing.
We're getting around to building a new buliding (it keeps getting moved out based on revenue :-) ) and we figure we'll be lucky to get anyone to take it for free, since by then it'll be the third assembly.
Did you see the thread on that very topic a few weeks back? This guy -->
formatting link
seems to be a really good value if don't need ever last bit of programming already done for you by, e.g., National Instruments. If you're feeling a little more flush we have a few of the NI USB adapters (something like $400/ea?) that we've never had any problems with. We also have one NI Ethernet->GPIB converter, and unfortunately it isn't fully compatible with all of our instruments.
Oh, I cheat. I certainly would not want to try to think about the physics. ;-) I use a program written by John Mezak called "AirCoil" or something like that. But you can do as well using the calculator on
formatting link
The basic idea is to think of the coil as a helical transmission line; if one end is open, the other shows a series resonance at odd quarter- waves.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.