I've managed to acquire this from a known-good 12V PC
exhaust fan, and would like to modify it as shown in
Imhotep's tutorial videos, although as of yet I'm not
exactly certain whether the coils need to be bifiliar.
Is there any way to tell how these coils are wound
without removing the circuit board? I'm guessing that
if they turn out to be singly-wound, the desired effect
can not be achieved?
It's a very nicely-running fan, so naturally I'd prefer
to keep it in working order unless its candidate for
this project -
These fans are never bifilar wound coils. Why should they be?
They are not (usually) transformers. What they do is often share
a pin to create an magnetic coil asymmetry when the power is first
turned on so that when they first start to spin they turn in the correct
direction. They use an IC hall-effect switch that not only detect the
index points from the rotor magnets put also the absolute (N/S) polarity
of the magnetic poles passing the IC.
Bedini uses bifilar wound coils to implement a magnetic mirror circuit,
sensitive to AC pulses but there is no asymmetry on startup hence the
bedini will not self start. Bedini overlaps a bifilar sense and drive coils
to make winding easier.
The Bedini Fan uses these separate coils to implement the magnetic
mirror circuit because this circuit can work with separate coils too.
So you would first have to convince me that a fan motor would ever
use bifilar wound coils.
:S:MarkSCoffman
A descript analysis, thank you.
It appears that I've left out a certain detail about
these coils... the ones clockwise from the power leads
seem to be connected with double wires as indicated.
The instructions that follow are confusing me a bit.
If the upper coil has two wires, then it must be the
common ground, as I've recently learned. Each of the
coils with one wire attached must then be the ones
ending the wrap, while the others from the upper coil
mark the beginning?