Hi, I feel stupid even saying this out loud because I'm not sure this can be right, but Ferroxcube, TDK, Epcos etc make U/I ferrite cores - but no bobbins?!? How the hell does anyone from hobbyists to production lines get around this "problem"? Any help appreciated, and sorry if I've got this wrong.

 

https://milesplatts.co.uk/products/coil-bobbins-for-ferrite-cores

 

Hi, thanks for that - all a bit small but nice to know. I'm going to use PP sheet, heat bend that into shape, then make a wooden blank the size of the U-core, wrap my folded PP shape around, and then wind onto that. Then hopefully slide it off the wooden "leg" and onto the U-core leg. Quicker/easier if I had a 3D printer, but what the hell. Thanks again

 

I suggest that the TS examine some transformers prior to any building efforts.
Bobbin materials may be available from actual electronic parts distributors.

 

https://fair-rite.com/

https://fair-rite.com/engineering-kits/


Check this company- they also offer core and bobbin kits for Ham radio and DIY design projects.

 

https://milesplatts.co.uk/products/coil-bobbins-for-ferrite-cores

MilesPlatts are a weird company to deal with. They are the most generous with samples, but when you have proven your design and want to buy 100, you'll find that the MOQ is 1000, and you have to wait while they make them.

Finding bobbins is often a matter of terminology. Quite a lot of distributors call them "coil formers" and a search for "bobbins" draws a blank. Often typing the size into the search box, e.g. EF25 will show both cores and bobbins.

https://powermagnetics.co.uk/shop/ will sell you small quantities.

On a similar note, for a long time I believed that RS Components didn't sell presets, but they call them trimmers, and searching for presets draws a blank.

 

I suggest that the TS examine some transformers prior to any building efforts.
Bobbin materials may be available from actual electronic parts distributors.

I even contacted Ferroxcube, Epcos & TDK direct and they all admitted to not making anything for U/I ferrites above a small few sizes, and I wanted 28x216 or 20x20, so it was "make your own"

https://fair-rite.com/

https://fair-rite.com/engineering-kits/


Check this company- they also offer core and bobbin kits for Ham radio and DIY design projects.

Tanks for the lead, my problem is it's experimental work leading to a patent, so it's messy, buts here, a change there so I think it'll be DIY

 

MilesPlatts are a weird company to deal with. They are the most generous with samples, but when you have proven your design and want to buy 100, you'll find that the MOQ is 1000, and you have to wait while they make them.

Finding bobbins is often a matter of terminology. Quite a lot of distributors call them "coil formers" and a search for "bobbins" draws a blank. Often typing the size into the search box, e.g. EF25 will show both cores and bobbins.

https://powermagnetics.co.uk/shop/ will sell you small quantities.

On a similar note, for a long time I believed that RS Components didn't sell presets, but they call them trimmers, and searching for presets draws a blank.

I think my problem is I want them for larger (28x16 and 20x20) core sizes which are usually power units, so normally only need a few turns and so are wound direct over tape onto the leg. Not my situation but I'm trying 0.6-0.8mm PP sheet and heat bending it this week, it seems the quickest and easiest way to go. Thanks again

 

I think my problem is I want them for larger (28x16 and 20x20) core sizes which are usually power units, so normally only need a few turns and so are wound direct over tape onto the leg. Not my situation but I'm trying 0.6-0.8mm PP sheet and heat bending it this week, it seems the quickest and easiest way to go. Thanks again

How about the ETD range. They are easy to get both in cores and bobbins:
https://www.mouser.co.uk/c/passive-...n/ferrites/ferrite-cores-accessories/?q=ETD29
Or PQ shape
https://powermagneticsstore.co.uk/shop/coil-formers-bobbins.html?cat=13
https://powermagneticsstore.co.uk/shop/ferrite-cores.html?cat=23

 

This is how I used to make transformer bobbins, 60 years ago. The pieces interlock. I then used a tight-fit wooden former with threaded rod through the middle for winding. I wound a few 240V power transformers using this method.

 

This is how I used to make transformer bobbins, 60 years ago. The pieces interlock. I then used a tight-fit wooden former with threaded rod through the middle for winding. I wound a few 240V power transformers using this method.

View attachment 358183

If you draw that on KiCad, your favourite pcb company makes your bobbins. The smarter ones might even ask why there aren’t any tracks.
Actually, if you’re careful and avoid shorted turns you can add some copper pads so that you can solder it all together