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Howdy. Here's a basic question about the labeling of inductors (those that resemble small electrolytic capacitors), commonly used in switching power supplies. I searched the web on the answer to this but found no specific answer on inductors, only for capacitors.
Here's the situation, I have some lose inductors which are labeled 224C and I can't figure out their micro-Henry reading just by looking at that code.
Inductors labeled as such are present in circuits I have at hand (RW's 4LW and GeekKlok) and their schematics call for 220 uH (micro-Henry) parts, so I wonder if that's the correct inductor to be there in the first place.
The schematics of other circuits I have (standalone switching power supply, for instance) also call for inductors with a 220 uH reading, and the one actually installed in the unit is labeled 221 (which, borrowing from capacitors, I suppose could mean "22 and 1 zero", bringing it to 220, while uH would be the unit of choice).
But the labeling on the 224C inductor puzzles me a bit. Could it be that it means "22 plus four zeroes" - 220 thousand ***pico-Henries*** (which equals 220 micro-Henries)? If so, how to avoid this kind of confusion in the units used?
Thanks
Marco
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On Mon, Aug 2, 2010 at 11:36 PM, cagamba <cagamba@...> wrote:
Howdy. Here's a basic question about the labeling of inductors (those that resemble small electrolytic capacitors), commonly used in switching power supplies. I searched the web on the answer to this but found no specific answer on inductors, only for capacitors.
Hello, I understand that I'm not answering your question, however, I believe my comment is relevant. One of the best investments I have made into my test bench was buying an LC-meter. I got a relatively cheap one off eBay, I paid €40.21 for the device (free shipping), and am just happy about the meter I bought. The model is DM4070. Not that I'd discourage trying to decipher the component labeling, however, sometimes the labels are so cryptic that using a meter is much faster than endless googling. BR, Dmitri
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Howdy. Here's a basic question about the labeling of inductors ...
Thanks
Marco Depends largely on the manufacturer. For a 220uh inductor, you'll commonly find it labeled 221 or 224, for 'uh' or 'nh', respectively. See if you can make out the maker of the part, and refer to their datasheets. If you can't, then get hold of an LCR bridge or meter. If neither of these are an option, you can always learn a little basic electricity, and rig your own simple bridge. The calculation for inductive reactance (Xl) is Xl=2*pi*f*L, where Xl will be in units of ohms. Make a simple divider, using a small trimpot of 5K ohms, hook it up in series (tap to one side) with the unknown inductor. Feed a 1MHz signal to that divider. measure the voltage drop across each component, individually. Repeat while adjusting the trimpot, until the voltages are equal. Turn off the rig, and measure the DC resistance of the trimpot (tap to the side used above; tap aka wiper). That DC resistance will match the reactance of the coil at 1MHz. The 1MHz source, can be made using a logic inverter (7404, 74HC04 ...), a 1MHz xtal (crystal), and a pair of small caps, and a resistor (2M2 to 10M). You can google 'simple crystal oscillator', for the schematic. For a 220uh coil the reactance will be in the 1300 ohm area. If its under a couple of ohms, then its 220nh (nano-henries). It won't give you precise measurements, but at least you'll be in the 'ballpark'. I know a lot of people don't want to be bothered doing it the long way, but you'll learn something. A basic understanding of electricity, will often get you out of a bind. Understanding the 'fundamentals' (in any field) is worth a lot more than any fancy piece of equipment.
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One of the best investments I have made into my test bench was buying
an LC-meter. I got a relatively cheap one off eBay, I paid €40.21 for
the device (free shipping), and am just happy about the meter I
bought. The model is DM4070. Not that I'd discourage trying to decipher the component labeling,
however, sometimes the labels are so cryptic that using a meter is
much faster than endless googling. Or, if you don't have a RLC bridge you can do what I have done to measure hand wound coils. I use my function generator to drive a circuit at a known frequency and set up a voltage divider with the coil. Size the resistor appropriately for the drive capability of your function generator. Also, remember that a meter is typically 10MOhm, so if you limit the current with a 1MOhm or greater resistor, the meter is going to noticeably alter the measurement. If you don't have a function generator, you could use a low voltage transformer and work from your supply frequency (50 or 60Hz). Use Ohm's law and the reactance formula to get your value of L. XsubL (inductive reactance) = 2*pi*f*L OR L = XsubL / (2*pi*f) Where XsubL = E/I
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--- In NEONIXIE-L@..., "threeneurons" <threeneurons@...> wrote:
I know a lot of people don't want to be bothered doing it the long way, but you'll learn something. A basic understanding of electricity, will often get you out of a bind. Understanding the 'fundamentals' (in any field) is worth a lot more than any fancy piece of equipment.
Totally agree - your brain is the best test instrument you'll ever have. But if you want the fancy piece of equipment route, then get yourself one of these: Animal, vegetable or mineral, this thing detects which and quantifies the value with one button push. A very smart time saver. Cheers, Jon. PS No connection with the company beyond serial happy purchaser.
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On 8/2/2010 1:36 PM, cagamba wrote: Howdy. Here's a basic question about the labeling of inductors ...
Thanks
Marco
Marco, The 224 is indeed 22 followed by four zeroes, or 220,000 of whatever unit the manufacturer decided to label the part with. Often that's nanoHenries. You can tell at a glance which of nH (nanoHenries), uH (microHenries) or mH (milliHenries) a coil is by the number of turns and the wire diameter. A coil with some number of nH is wound with just a few turns of wire. These are used at radio frequencies, over 30 MHz typically. A coil with some number of uH is usually about the size of your fingertip and has many turns of wire, but the wire is big enough to see. These are used in switching power supplies at some hundreds of kHz. This is what you have, right? A coil with a large number of mH is bigger than your thumb, and/or is wound with so many turns of fine wire that you can't see the wires individually. These are used at audio frequencies, such as speaker crossovers or telephone signal coils. -- David Forbes, Tucson, AZ
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--- In NEONIXIE-L@..., David Forbes <dforbes@...> wrote:
The 224 is indeed 22 followed by four zeroes, or 220,000 of whatever unit the
manufacturer decided to label the part with. Often that's nanoHenries.
A coil with some number of uH is usually about the size of your fingertip and
has many turns of wire, but the wire is big enough to see. These are used in
switching power supplies at some hundreds of kHz. This is what you have, right?
That's right, Dave, I've got my metric conversion mixed up, sheesh. 220,000 nH - not pH - amounts to 220 uH. On the other hand, the "224" inductor is indeed the size of a fingertip (the 'pinkie', precisely :) and it is functional on the said equipment, so no way it could work if it was off 1000 times from the specs.
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--- In NEONIXIE-L@..., "jonellis32" <jon@...> wrote:
this thing detects which and quantifies the value with one button push. A very smart time saver.
Lovely little gadget, that meter is. Matter of factly, I love instruments in general, and how they are able to decypher things. One of my favorites is my digital caliper and I love to try to trick it - by setting it to zero, work with it a bit and slowly bring it back to the starting point. Amazingly enough, it goes nonchalantly back to zero, and if I put a mere piece of plastic film there, the sucker still shows 0.01. I have no idea where it gets its precision from, what type of component can measure such a small movement. Anyone knows what's in there? I once read it is based on capacitance. I also love to think of precision (and tolerances, for that matter) as a concept, almost as a value in itself, and find myself looking at everyday objects and trying to find the type of precision bourne in them. [And I completely agree with Mr. ThreeNeurons (but, boy, WHAT three neurons...) that your gray matter is the best equipment you can make use of.]
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Lovely little gadget, that meter is. Instead of buying a meter, how about making your own, 'old fashion' style LCR bridge, with a magic eye tube (to keep it somewhat on topic): That will be a nice 'retro' project (for an inductance bridge). Its comprised of a 1KHz oscillator, that feeds the same signal to two sides of a bridge (a divider per side). One side is a resistor and a pot. The other side is a set of reference inductors (switch selectable for range), and a the spot where the unknown component plugs in. When the ratio of both sides are equal, both the amplitude and phase, of the signals at both divider taps will be equal. Both of those signals can be fed to a differential amp, made from one dual triode (6J6, 12AT7, 12AX7 ...). The AC output when both signals match is zero. Rectify (6AL5) and filter that signal, then feed it to the (pre-biased) triode section of the magic eye (6E5, 1629, EM80, EM84, ...) and then feed that signal to the eye control itself, and there you have it. The eye's shadow should be smallest, when pot/resistor ratio matches the inductor side. You can use some known values for making a calibrated dial, for the pot.
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