Need help on identifying big BLDC motor from 5.25 HDD (hallsensors?)


I have a very nice 5.25 HDD spindle motor with (obviosly) built-in hallsensors (or probably other kind of sensors?). I tried already to find a datasheet, but no success. The 3 spindle coil connectors are easy to identify, but I have real trouble to find out how to connect the hall sensors that are built in. I tried already to put 5 V DC from my arduino to the red/black connectors, then measured several combinations on the remaining 6 connectors which I believe are the hall-sensors. But the signals coming back is not 0 or 5V like a hallsensor should do. I measure slight voltages going up and down when turning the spindle by hand, for some combinations the current is alternating between -200 mV and +200mV. It looks more like a sinuswave for me, but not from the spindle coils. It delivers only a signal when I connect 5V to the red/black connectors.
Unfortunately I can't open the spindle, dont want do damage it. The original driving circuit is missing, only housing, platters and spindle is left. Can anybody help to identify or how to find out about the sensors (6 pins + 1 black + 1 red). I also added 10k pull-up resistors, but no on/off effect when turning the spindle. The HDD is a FUJITSU M2266SA, the spindle is manufactured by Matsushita but google does not return anything useful on the part number(s) DIL-58B 3  or  B90L-1415-0021A. 

Any help to get this baby running is highly appreciated!

sort by: active | newest | oldest
rickharris5 years ago
It is almost certainly a head motor from a dismantled video recorder head.

It will need to be driven by a microprocessor or dedicated switching electronics as it is essentially a stepper motor.

(It's a 5.25 HDD spindle motor)
I agree with your comment on control.

I really should learn to look at the rest of the pictures. Your right of course.

I thought it looked too deep for a spindle motor hence the video head thought - still that same result though.
pocketom (author)  rickharris5 years ago
On first sight it looks really like a video recorder head motor. It's a full height 5.25 drive that occupies two slots, the spindle weighs 1.4 lbs :-). What I could findout meanwhile is that it does 3600 RPM, 60 frames/s should be enough for POV. I've crawled ebay for similiar models but full height drives seem to be rare. It's a shame that the circuit board has been salvaged, that would really help me. But I've found the actuator, another double-pounder ^^
I missed the POV end product - Lots are made from normal motors and have a hall effect sensor (none contact) to let the processor know when to start the message.

On a very light load most motors are quite stable when up to speed.
iceng5 years ago
I Think that you can pull the outside cylinder after marking the orientation
and undoing the six deep screws, since it is obviously a fixed inside out
wound stator, without fear of damage or sproinging.
You take excellent pics.

pocketom (author) 5 years ago
The three wires going inside are magnet wires, when connecting them to a DMM (I don't have an oscilloscope), it produces ~3-8V AC current, I also can measure the frequency with my DMM. No matter how I connect 2 of the 3 coils, it always produces AC, so I'm relatively sure it's a 3-phase spindle motor. I've already prepared a 3-phase power stage with some good diode protected HEXFETs, but without knowledge about the hallsensors I can't interface with my Arduino (do old HDDs have halls or are there other 'oldschool' sensors known?). Strange thing is that the connector has so much pins beside the A,B,C coils. Is it possible that this thing has 6 hallsensors?

I've added pictures from the 5.25 HDD, perhaps somebody knows a datasheet for a similiar model's spindle? It's curious that there seems to be nothing available on the net...
pocketom (author)  pocketom5 years ago
I've added a closeup of the connector and sketched in the relevant pin positions with their colors.
iceng5 years ago
Are the three wires plunging into the center well, magnet wires or is that an
insulated small gauge wire ?