Help designing 125khz passive inductance coil for T5577

[Satur9]

@Taggart

Correcting those conversions in the 66philip calculator gives ~17 turns

17 turns would give you 12.4uH not 12.4mH. Off by a factor of 1000

Assuming you have 28AWG magnet wire which is 0.32mm thick, and you wind a coil that is 29 turns wide and has 29 layers stacked, you would get this

That’s gonna be a huge pain to get precise though. Rings are not really ideal for this because of their shape. They’re inherently long relative to their diameter, and they have to be made of durable materials which kinda rules soft metals like ferrite out. Check out the second post in that thread I linked to see what factors affect inductance:

@Satur9

So Inductance is:
L = (u * N² * A) / l

u is the magnetic permeability of the core. If it’s air it’s constant. If it’s different grades of iron you can multiply the inductance simply by winding it around different stuff

N² is number of turns. You can see it’s exponential, so double the turns means 4 times the inductance

A is area. A wider coil linearly increases the Inductance

l is length, and it’s in the denominator. A shorter coil linearly increases the Inductance

As a result, a perfectly flat wide disc coil wound around a flat disc of ferrite would have a really high inductance. A straight wire is the exact opposite of that and has a very low Inductance.

or, you could just come to the same conclusion that everyone here has and decide that wearables are dumb and you should just get an implant. Not sayin, just sayin.