Author Topic: I bought a stepper motor without a datasheet  (Read 1492 times)

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Offline Clear as mud

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I bought a stepper motor without a datasheet
« on: July 16, 2013, 03:02:59 pm »
I see there is a topic from a few days ago "Would you buy a stepper motor without a datasheet?"  Apparently I would, because I did.  But I am not sure I can figure out all the wires.
http://www.allelectronics.com/make-a-store/item/SMT-118/16-WIRE-STEPPER-MOTOR/1.html
It's a surplus motor, apparently designed in the 1970s.   I bought three of them, and the one I examined closely had a date of 1984 stamped on it.
Made in Belgium# PD 12. Code number : 9904 112 12001. 3 Deg. 45' step angle. 175mA. 150 g/cm torque.
All that information is directly from the label on the motor.  I figured out the 3.75 degree step means 96 steps per revolution.  if I turn the shaft by hand, with everything disconnected, I can tell it has 96 detents per revolution.  Feels like detents, but maybe it is due to magnetic forces?  The one user comment on the All Electronics site where I bought it says two things:
1. This is a 8-phase unipolar stepper motor.
2. This is listed in the Philips Data handbook CM6 04-77 (1977).
I looked for that handbook and was unable to find it.  I found a Google Books listing for it, but no text.  I found it listed on the LibraryThing website, as being in someone's personal book collection, but I get no results on a WorldCat search.  Does anyone know where I might be able to find this book and look at the pages that list data for this motor?

The 16 wires are clearly in eight pairs, each with one solid color and one white with a color stripe.  I checked with a multimeter, and I get about 24 to 30 ohms between each pair, and no continuity between wires of different pairs.  So, the unipolar 8-phase thing seems correct, but how do I know the sequence to drive them?  If I hook up any one of the eight pairs to 5 VDC (which should not exceed the rated current too much, based on my resistance measurements), the motor shaft jumps.  Then I hook the same pair up backwards, and the shaft jumps again.  I hook it up backwards again, and it jumps again.  Each jump is always in the same direction, for the same pair of wires (but I think it is different, for different pairs), and each jump takes the shaft 3 degrees and 45 minutes around the circle.  This is not exactly what I expected.  If the step size is 3 degrees and 45 minutes, then I expected each pair of wires to take it eight times that distance.  I thought I would have to hook up the next phase and then the next one, to go another 3.75 degrees each time.  Well, actually, I guess I am going twice the step size before I hook up the wires the same way again, but it's still less of a jump than I expected.  And again, how do I tell the difference between the eight pairs?  If the difference between them is so tiny, and the motor already has 96 detents, am I just landing back in the detents when I disconnect the wire, no matter which pair I use?
I think disassembly of one motor might be required, to see how the windings are arranged.  And then I'll have to order more of them if I can figure it out, and if I have to destroy the one to get it apart.
 


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