I know number 3 is definitely ok. But what's the downside of using No. 2? Can No. 2 meet the design requirements? Because I want to achieve the best results while keeping costs in check. As you all see, I still have a lot to buy.
I've also seen iron core inductors like size 1 used on some projects by others, as Paul.C said, you can choose any type of inductor! The question is, is number 1 ok? If it is used, what is the disadvantage compared to the No. 2 hollow coil?
Although the copper wire of No. 1 in the picture is only 1.2mm, I can also find 1.6mm 5mH iron core inductors, and their internal resistance should also be less than 1Ω.
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