pc case fan (pm generator)

[Kwazai]

I popped open a large size case fan (pc) which is a permanent magnet type and found four poles and three wires hooked to the copper coils(poles). How do I rewire so I can use it as a generator- it also has the electronics to drive it as a 3-phase(2-phase?) motor. any help would be appreciated.

[drdongle]

Remove the P.C. board and connect a multi meter to the leads, then turn it and test for DC or AC output, if AC add a bridge rectifier to convert the output to DC.

[Kwazai]

I was expecting to find two wires-but found three instead. two of the wires go into the ends of the two of the coils, the third one goes into the side of one of the other coils. which two do I connect to?

I have a schematic for a rectifier(diodes). Do I use two diodes with this or three?

I was also planning on hooking in a small regulator (7805?).

tia

Mike

[ghurd]

First spin it and check for an AC or DC output between wires 1+2, 1+3, 2+3.

The 3rd wire may be the end of BOTH coils. The first 2 wires could be the starts?

Check the resistance between them all.  If the resistance of wire 1 to 3= 50, wire 2 to 3= 25, and 1 to 2= 75, then the 3rd wire is the ends of both or maybe a center tap.

G-

[Kwazai]

will do. It will be the weekend before I can get to it though.

tia

Mike

[(unknown)]

I'm pretty sure that PC case/fan motors are brushless DC motors.  If so, there is a little chip inside which pulses the DC to one or two phases to spin the shaft.  The third wire on a PC fan is typically a tachometer output.  In order to use them for generator use, you'll need to open them up and remove the controller circuit.  Output from the coils will be AC in either one or two phases.  If the latter, try series wiring the coils.

As an aside, I don't think you'll get anything at all if you hook a meter up to the external wires and spin the shaft.

Good luck!

[Kwazai]

The third wire was a cemter tap, total resistance on the coil was about 53ohm. pics below.

I put it into a piece of cardboard and blocked off my house chimney with dying coals and could not get enough airflow-but- after throwing about three or four pieces of junk mail in there, I was able to get 350millivolts AC out of it pretty consistently (spikes to just over a volt)-when the junk mail flared up.

[Kwazai]

I am wondering if hooking a couple of diodes (1n914?) will give me DC voltage, followed by a voltage regulator (7405?7805?). any body have a link or circuit sketch? I'd like to try to run a cpu fan with it- they typically take around 3volt. This big case fan is a 4watt, the cpu fans are 1watt. Does anybody know how to figure the amperage coming out of the casefan/genny??