PC Fan Generator

[geotron]

This is where I'm thinking of going with it...

Having three coils to start out with so each
one collects a different polarity with the
N-S-N-S of the tops of the magnets.

mscoffman - I tested what you described, holding
some magnets close to the spinners to slow them
down and draw additional energy.

What I found was that the voltage stayed precicely
the same, while the current draw bumped up maybe
around 5mA - I was really slowing it down too.

The next step for me is to find some diodes to
work with, and a potentiometer to find the just
the right speed where the magnets are spinning
as fast a possible without flying away.

[mscoffman]

Move some of the magnets on the inside to additional outside positions
maybe like a square, hexagon, octagon. Actually you should alter the N/S
poles of each of these on the outside so the coil doesn't see one big
'N' or 'S' all the time. These additional "poles" will make your AC go
up in frequency per motor revolution.

Leds have a pedestal voltage before they turn on, so they
are not quite as good as pure loads as resistors are.

Ok, the motor control circuit can either increase current which
may be difficult for it if the voltage input is 5Vdc low. (your PS
supply should be regulated at 5Vdc). Or it has to let the motor slow
down. The generator function is proportional to RPM,s so it would
automatically cut the voltage, power and braking back as the rpm
drops. Allowing it to seek a steady state.

:S:MarkSCoffman

[geotron]

Hmm - in order to add additional magnets I would
have to retool it a bit to accomodate a large flat
disc to glue them on to. If I can get some preliminary
results tomorrow when I hopefully find some diodes,
then I'll have a go at it.

What I ought to figure out at this point is how to
change the resulting current output of the coils from
AC into DC.

I'm fairly certain there's a quick way to go about it,
but a bit of searching has left me without an answer.

Edit:  Alright, I get it now - the diode IS what turns the
AC into DC by blocking half the waveform...

[geotron]

...

[jadaro2600]

Alright, I get it now - the diode IS what turns the
AC into DC by blocking half the waveform...

Actually, if you take the fan apart, you've probubly got a circuit board on there which converts the DC to AC or pulses the coils on the fan board so that they alternate polarity.

The fan assembly usually consists of a cheap plastic shell, inside of which there is a soft ceramic magnet ( ring shaped ) which has two north and two south poles n-s-n-s around the rim, or north on one side and south on the other if there are three coils on the fan board.

It's not really practical to have brushes on these types of fan because they're intended to be run for long periods of time, so they use a controller board to create induction ....