What to know when buying inductors - Page 1
Forum section: electronics / beginners

author: watchmaker
author_rank: Unknown
timestamp: November 15, 2023, 01:37:19 pm
content: While I am studying, I am also creating a stock of parts for experimentation and future projects.All non surface mount.I have pretty much everything but a good range of inductors (what I have is in my AD2 parts kit).What do I need to know as I look for a range of inductors? New vs old? Brands? Values? Power ratings?I do not see RF projects in my future. My timer will likely go "ding" before I get there.Regards,Dewey

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: November 15, 2023, 03:22:55 pm
content: Hi Dewey,....depends on your applications.Frequency-range, kHz? MHz? GHz?AC only, or will there be DC-current?Too much DC saturates the core (if any) and makes the inductor a resistor.Good luck

author: Terry Bites
author_rank: Super Contributor
timestamp: November 15, 2023, 04:34:21 pm
content: Not all indcutors are born equal, so its important to use the right part for the job.Inductors have quite a few non-ideal charcteristics. Series resistance and saturation current come to mind as does self resonance caused by the interwinding capacitance.Voltage ratings, thermals and shielding all play a part in your selection.Vendors such as Coilcraft, Würth Elektronik and Murata provide selection toolseghttps://www.coilcraft.com/en-us/tools/rf-inductor-and-choke-finder/#/searchandhttps://www.coilcraft.com/en-us/tools/power-inductor-finder/#/search

author: janoc
author_rank: Super Contributor
timestamp: November 15, 2023, 08:14:47 pm
content: Quote from: watchmaker on November 15, 2023, 01:37:19 pmDon't. Waste of time and money because inductors are both fairly rarely used and when they do need to be used (e.g. filters, power supplies, RF circuits, etc.) you need to buy or build one that fits the purpose of that circuit - and the requirements are vastly different for each. So keeping various assortments and such without specific project in mind is pointless - it takes up space and you are pretty much guaranteed to never have the part you need.This is very different compared to resistors, capacitors or some common jellybean parts where keeping some basic stock is a good idea.TL;DR - buy inductors for specific projects when you know what exactly you need.If you only want to play around get an old computer board and scavenge some from the DC-DC converters there. There will be quite a few and they are likely one of the few things worth desoldering because power inductors can get pricey fast (copper costs money!).

author: watchmaker
author_rank: Unknown
timestamp: November 15, 2023, 10:04:21 pm
content: Quote from: janoc on November 15, 2023, 08:14:47 pmThank you. OK. I am only starting RC ckts analysis so I will not worry past the coild in my AD2 ADPLAP 2000 parts kit. These should follow the course.Regards,Dewey

author: radiolistener
author_rank: Super Contributor
timestamp: November 15, 2023, 10:56:28 pm
content: Quote from: watchmaker on November 15, 2023, 01:37:19 pmit depends on applications. The main parameters are: inductance, Q-factor, resonant frequency and max current.

author: MarkT
author_rank: Frequent Contributor
timestamp: November 15, 2023, 11:18:12 pm
content: Quote from: radiolistener on November 15, 2023, 10:56:28 pmAnd gapped/non-gapped - having a gap in an inductor's core stabilizes all the parameters at the cost of reducing inductance, because air has close to ideal magnetic performance.You can get pot cores, bobbins and magnet wire and make your own inductors as and when needed, perhaps more flexible than being limited to catalog values.

author: Dan123456
author_rank: Regular Contributor
timestamp: November 16, 2023, 01:12:05 am
content: I asked a similar question a while ago and the answer I got was basically “don’t bother stocking them. Buy them as you need them”I figured that, like resistors, capacitors, ICs, etc., there would be a few “common” ones worth always having on hand but came to learn that is not the case at all and you really should buy them as you need them for a specific projectI’m still new to the world of inductions but have learnt that the physical size of the inductor matters, the value matters, the amperage value matters, the core material matters, etc. so you kinda have to know those details first then pick an inductor to suitHope that helps

author: fourfathom
author_rank: Super Contributor
timestamp: November 16, 2023, 06:00:19 am
content: Quote from: Dan123456 on November 16, 2023, 01:12:05 amI agree with that, generally. I do a lot of RF design, mostly low-power in the HF and low-VHF range, so I do stock a decent assortment of iron powder and ferrite toroid and binocular cores, in the appropriate sizes and formulations. I can get most any inductance or transformer ratio I need by winding my own inductors.Also for RF, I do keep on hand a stock of surface-mount inductors in the 10nH - 10uH range. But these tend to be more specialized, and unless you have specific plans you probably don't want to spend money on this. Lately I've been designing and building a range of filter projects so having these on hand makes sense for me. Do realize that (for example) 1uH surface-mount inductors come in all sizes and designs, and each has a different DC resistance, Q at a particular frequency, and self-resonant frequency. So stocking these "just in case" probably isn't worth it.For power designs (switching regulator, etc) I just buy what I need when I need it.You might want a small variety of ferrite choke inductors, either beads you can string on a wire, or surface mount parts. These are useful when you want to filter or isolate power connections in RF or sensitive analog designs. You only need a few varieties here, at least until you get to higher-power levels.

author: rteodor
author_rank: Frequent Contributor
timestamp: November 16, 2023, 08:10:16 am
content: Quote from: watchmaker on November 15, 2023, 01:37:19 pmIt depends on what projects you have in mind. Do search a bit deeper on that because that would hive you some hints.For example, I do keep small amounts (a few pcs. of 22, 68 and 100uH SMD and TH) for occasional DCDC converter. It is very handy to have something around because I do not have to overcalculate and search for a proper inductor - I just oversize it.But if you have a hunch that you need inductors for oscillators or filters then you need an exact part and what janoc and other forum colleagues said above applies.