Hello,
Interesting links.
I do want to mention, however, that when winding an inductor with a magnetic
core of any type there are many things to consider. Not only the initial
inductance value, but also the change of inductance with dc current
(sometimes called the 'incremental' inductance)
and max current.
This means that we need exact information about the core such as
inside diameter, outside diameter, height, width, and material composition.
Sometimes we can find info on the manufacturers site that made the core
which makes it a little easier.
Even so, sometimes problems come up, such as core saturation.
Core saturation occurs when the current goes too high, and this causes
the cores magnetic properties to drop to near zero. What this means
to the circuit is that we start out with a core with very good mag
properties and we end up with only an air core. This causes the
inductance to change quite a bit, and this means the impedance
decreases drastically and that means the circuit draws too much
current.
To help the situation, sometimes we can insert an air gap into the
magnetic path. This helps to prevent saturation, but means the
overall inductance comes down, and this means we have to add
more turns of wire. As we add more turns of wire we decrease
the coils ability to handle higher current because the core saturates
even more easily, but because of the air gap we have overall
increased the coils ability to handle higher current. Eventually
however we might fill up the cores inside diameter so that no more
wire can fit on that core, and so we find that we can not even use
that core, so we have to go to a larger diameter core.
This is a bit hard to acheive without some sort of procedure, but
it is in fact doable. The real problem though is how to form the
air gap.
If we use a ferrite toroid core we would have to cut
with a grinder or something, and try to get the gap to be the
right width. This is very hard to do unless you are a core
manufacturer with the equipment to do this kind of thing on
a regular basis.
There are however, other types of cores that can be used that
come in two parts...we simply provide some insulation material
to form a gap, and that gets us there too, provided we selected
the right size core to begin with.
There is a better way however, that gets us there much quicker.
That is, to simply *purchase* a coil that is already made to fit
the specifications. Since there are many many coils that can be
found at online parts stores this is the fastest and easiest way
to do it.
The only thing we have to know now is the coils inductance,
how much of a change in inductance is tolerable, and how much
dc current would be flowing, and the max current.
We could look up come coils on some parts store sites and find
a coil that matches what we need, and order one.
100uH coils are very common, and so are 1000uH coils. It should
be possible to find both of these somewhere online.