Can anyone confirm this old IDE Seagate 180MB HD stepper motor config?

[lasermaster1977]

I've been scrounging through my old stock piles of electronics "stuff" to see what might be reusable and repurposed. I disassembled this 180MB Seagate HD of mine, an oldie for sure, targeting the platter stepper. Here are some pics and wiring data. From my testing, this neat little motor ohms out like it is a 3-wire, 3-phase stepper even though it has 8 wires. But only two 5 ohm coils exist and have one end of each coil tied together, the other 5 wires are not interconnected (open circuits) when the 8 pin plug is disconnected from the PCB. (see wiring diagram)
All of my web research indicates this is a very early HD platter motor implementation by Seagate with no information available.

Connecting a 5V PSU between the common coil wires and either coil end does cause the spindle to move (bump or slightly rotate) and draw about 1 amp briefly. Manually rotating the spindle one can tell there are 24 magnetic "steps".

HD Model info


Stepper Motor Wiring-Side


Stepper Motor Platter-Side (platters removed)


Motor flexible PCB leads and dual 4-pin male plug


Pin-out Wiring determined by Ohm Metter


Does anyone have operational insights for driving this little guy. I'm just interested in seeing if it can be used as a variable speed motor.

Thanks in advance.

[laserist]

3600RPM probably 12v. The "steps" are probably what's called cogging

[lasermaster1977]

3600RPM probably 12v. The "steps" are probably what's called cogging

Thanks laserist. Yep 3600RPM confirmed. 24 cogging positions are very subtle. This drive was probably from one of my Win3.0 systems long, long ago.

The extra wires may be for Hall effect position sensors (or something similar) but there aren't enough wires for there to be the usual three sensors.

I just found this but is just a partial of the full specs: https://stason.org/TULARC/pc/hard-dr...HH-IDE-AT.html

This URL has lots of device specs but with ads weaved throughout.

made by SWIFT for Seagate:

S W I F T 9 4 3 5 4 - 1 8 6 IMPRIMIS
NO MORE PRODUCED Native| Translation
------+-----+-----+-----
Form 3.5"/HH Cylinders 1272| 636| 742| 636
Capacity form/unform 164/ 186 MB Heads 7| 14| 12| 9
Seek time / track 15.0/ 4.0 ms Sector/track 36| 36| 36| 56
Controller IDE / AT Precompensation
Cache/Buffer 32 KB Landing Zone
Data transfer rate 1.250 MB/S int Bytes/Sector 512
6.000 MB/S ext
Recording method RLL operating | non-operating
-------------+--------------
Supply voltage 5/12 V Temperature *C 10 50 | -40 70
Power: sleep W Humidity % 8 90 | 5 95
standby W Altitude km -0.305 3.050| -0.305 12.192
idle W Shock g 2 | 50
seek W Rotation RPM 3600
read/write 11.0 W Acoustic dBA 43
spin-up W ECC Bit 32,56
MTBF h 150000

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