ring cores color coded?

Yes. There is a ring core calculator available over at

Oookay. I have 3 yellow ones here, 2 small, 1 a little bigger, and a green one. What does that mean?

Thx. Maybe I'll try it with wine ...

Bernhard

Allot of information about toroids and magnetic is corporate secrets. You might find some information here:

or here;

Shaun

A couple of things I forgot to mention:

Measure the outside diameter of the toroid in inches. (eg. for one that is 0.255 inches is a T-25 core)

the size of the core determines in properties( microhenries per 100 turns) as does the material that makes it up. Those colors that you mentioned are common types. The information that you get off the net will be the material type and some properties and operating frequency.

I hope this helps

Shaun

Is colour significant on toroids salvaged from scrap motherboards?

They're often pale blue or yellow - I think I've seen red ones too.

There's no standardization for the color coding of toroids.

Decades ago, there was a certain consistency in hobby circles, because virtually all toroids that got to hobbyists were from the same source, and interestingly, that common source was not a manufacturer but a small business that had set out to be the middleman, since the manufacturers weren't wanting to sell in small quantities.

Then, toroids became a lot more common. Originally they'd only be seen in non-consumer radio equipment, but eventually they became common there (albeit just a few toroids per unit), likely dwarfing the numbers used for non-consumer radio equipment.

Once that started happening, there was all kinds of opportunity to find toroids at the surplus store, or in consumer electronics that begged to be reused. But, without any information about who made the core, the color coding meant nothing.

If it's in equipment, at least the context will provide some information (and most of the time, it will be low frequency use, mostly power supplies). A blank toroid at the surplus store doesn't offer such information.

One generally has to wind a coil on the toroid, do some measurements and then calculations with the results. The more detail you need, the more effort has to be put in the testing. And then likely you could have gotten an identifiable toroid direct from some company that wouldn't have cost that much.

Michael

Michael,

There must be some consistency because if I look at Amidon, a popular distributor, they carry products from 35 different manufacturers, and they use a standard color coding.

Shaun

The colour coding of iron dust cores marketed by Amidon are specifically those of Micrometals. Other manufacturers have other coding methods - the most common being labeling of the part, with core colour denoting the type of material (iron dust, 'high-flux', permalloy, molybdenum permalloy, sendust iron-silicon-aluminum, iron-silicon, or whatever) not the graded permeability of the composite mixture.

Coating of ferrites is an option - the colour coding here generally denoting both the coating material type and coating thickness (with characteristic voltage withstand and physical characteristics) specified by the mfr.

Amidon is not a manufacturer of cores.

RKL

I know Amidon is not a manufacturer, they are the distributor of 35 different manufacturers.

Shaun

legg wrote in news: snipped-for-privacy@4ax.com:

Interesting to me because Micrometals' name came up in searches for RF transformer cores recently. Anyone know the title of a good book on winding them? I can find cores fairly easily, good information on how to use them seems harder to find, possibly.

Micrometals supply app notes for it's products.

ARRL, RAC and RSGB members also offer tips and construction projects in current publications and all over the web.

RL

legg wrote in news: snipped-for-privacy@4ax.com:

Thanks, the Micrometals guides look useful. I asked for a book recommendation for two reasons though, 1, it's likely that the writer has enough knowledge to spare me the risk of getting confused (I have found a copy of Bernard Babani's book which I hope will help with that). And 2, a guy in a ham radio newsgroup specifically suggested finding a book, stating that it's a complex subject not reliably learned from postings online. I'm not competent to do the technical filtering of the good from the not-so-good found in posts and web pages when it comes to RF and magnetic core properties. One good book likely solves most of those risks because the publishers and writer hopefully do that filtering as part of the work they're getting paid for when we buy books. A book may also be better aimed at practical use by the public, than a data sheet or project aimed at people who know the subject in detail.

Doug DeMaw, who worked at the ARRL for many years, wrote "Ferromagnetic-Core Design and Application Handbook", it's not clear whether it's in print or not.

I've never seen it, but had the impression it was aimed at a market somewhere beyond the ham market. So the tone is probably more like a text book, but surely he'd have brought his long history with hobby radio to it too. The hobby books tend to be of practical matters, you need to go deeper in order to learn about outright design.

That's the only title that comes to mind, I'm unware of what else might be out there though surely other books exist.

Michael

Michael Black wrote in news: snipped-for-privacy@darkstar.example.net:

Thankyou. Is out of reach though, the Bernard Babani book on coil design cost me under £4 new and seems like it will get me through. It looks like I can easily expect to pay ten times that for a used copy of this other book by the time I got it shipped here. Looks like I can trust to try ARRL as a useful limiting guide in searches though. I got outbid on the receiver I was after anyway; despite the 'recession' people are bidding very high there right now, on lots of stuff. So it will be a while before I go into this now, after Christmas, at least. My (second-place) bid was generous too, I'm half expecting to get a second offer confirming my suspicion that I lost to a shill bidder! For now I'll wait till the eBay crazies settle down.

Offtopic rant about recessions follows:

It isn't one, really, In the one I remember (late 70's to mid 80's, in UK), I don't recall clubs doing a roaring trade, second hand gear on eBay getting top dollar, and patio heaters and marquees outside bars as a constant feature in street after street. Last time a RECESSION hit, unemployment was double what it is now, never mind the smaller population (thus greater than double percent) of that time, and instead of what I just described, I recall street after street of major dereliction, the city centre was a ghost town of the kind that inspired songs by the Specials and the Stranglers, and largely gave rise to punk in Britain, I myself was living rough for six weeks, and squatting for several months, and there were repeated riots in the city centre. I'll never forget seeing 600 policemen with weapons and shields packed so tightly on a green space that it looked like a scary movie, and being ordered off the streets by policemen who explicitly threatened to beat us up with three-foot batons if we did not comply. THAT was a recession, what we have now is just a big fat reality check for people who placed their sense of value in paper and property and other speculative nonsense at the expense of the rest of us. They've had it so damn good that the 'recession' is mostly just them complaining loudly, and I don't see an end to their conspicuous consumption either... Anyway, I'm just ranting because clearly people aren't really hard up or eBay used item prices wouldn't be driven close to new as greed to AVOID new forces crazy bidding depriving me of a sensible choice between used and new items... I'll stop now before the Monty Python Yorkshire Accent kicks in.