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Stepper motor driver issues (Electronics Goldmine stepper motor G14197)

Discussion in 'Electronic Design' started by Vignesh Ganesan, Aug 7, 2006.

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  1. Hello,

    I'm having some issues getting this little guy to run:

    https://www.goldmine-elec-products.com/prodinfo.asp?number=G14197

    The site says this is a 2-phase bipolar stepper motor. Has anyone used
    this model before ? I've rigged up the schematic provided:

    http://www.goldmine-elec.com/pdf/g14197.pdf

    but it doesn't seem to work. I've double, triple checked the circuit,
    but the motor just won't work. It seems to me that there needs to be
    some sort of grounding or V+ applied to one of the windings of the
    motor ?? but I'm not sure...

    It would be great if someone who understands this stuff could take a
    peek and let me know if I need to add something to the circuit over and
    above what the schematic suggests.

    Thanks a lot !

    Best,
    Vignesh.
     
  2. The supply volts and ground come from the buffer 74HC365. You need an
    oscilloscope to diagnose this circuit; have you got one?
     
  3. Tim Wescott

    Tim Wescott Guest

    Well, the schematic of the motor that's embedded in the driver schematic
    is certainly wrong -- and I'm not too sure about what they're having you
    do with the 'bias current'.

    With five wires it's probably a unipolar stepper with a common center
    tap on the coils. The common center tap will prevent you from driving
    it as a bipolar stepper without more work than it's worth.

    I suggest you spend some time with an ohmmeter to figure out how it's
    hooked up, then spend some time with a battery and some switches to
    figure out how it works. Once you find common you should be able to put
    it through it's steps by switching each coil on in the right sequence.

    Then do some web searching on unipolar steppers to find the _right_
    driver circuit. You should be able to come up with a circuit pretty
    quickly.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
  4. Robert Baer

    Robert Baer Guest

    Lessee.... (1) photo shows 4 leads, (2) first part of "description"
    says 5 leads, (3) later part of "description" says 4 leads, (4) the PDF
    shows 3 leads, (5) the text mentions 2-phase, (6) the PDF shows 3-phase.
    I *do* like the consistency!
    So...*IF* it is indeed 3-phase, then there is only 3 leads as shown
    in the PDF and a true 3-phase drive is needed.
    On the other hand (or is that "on the other phase"), if it is a
    2-phase 4-lead motor, an H-bridge or equivalent is needed to drive each
    half (or coil if you insist) first one polarity and then the other with
    possible times of no drive current.
     
  5. The consistency is superb!... :)
    I'd suggest that if the original poster has an ohmeter, the best place to
    start, would be to try to work out the coil arrangement for themself.
    First question. How many leads are there on the motor?.
    Second question. How many leads go into the plug?.
    I think there are really two possible layouts, assuming that the plug is
    four pin. The first is that there is one 'common' pin, and three winding
    connections (as shown in the schematic). If so, with the meter attached to
    the 'common', the other three pins sould have almost equal resistances
    shown.
    However the description, and the look of the motor, fits with it being a
    normal bipolar motor (the sort used in many cases for the head positioning
    in old floppy drives), possibly with six leads at the motor, and only four
    connected to the plug (if it has got six leads, then it can be used with
    either bipolar or unipolar drives). If this is the layout, then there
    should be simply two 'pairs' of pins at the plug, with a winding between
    each pair.

    Best Wishes
     
  6. Hi Robert,

    Thanks for the reply !
    So then, assuming what I have a three phase motor, then is the
    schematic correct ? Or are you implying that this isn't the schematic
    for a "true 3-phase drive" ?
    Got it. I'm looking up the schematic for the h-bridge, will get to work
    on that this weekend !

    Thanks a lot !
    Best,
    Vignesh.
     
  7. Hi Tim,
    Neither am I !! That really threw me off !
    Alright. I'll do that and figure out what these leads are. Once that's
    done, I guess I ought to be able to come up with a unipolar circuit.
    Btw, is this a correct circuit for the unipolar motor ?
     
  8. There are 5 leads coming out of the motor -- R, Y, B, Wh and Bl.
    5 go into the plug. There are 4 points in the plug -- two of the leads
    (the Wh and Bl) go into the same point in the plug.
    I'll measure the resistances, sure.
    I guess if its got 5 leads at the motor and only four at the plug, that
    *still* makes it a bipolar motor ?

    Thanks,
    Best,
    Vignesh.
     
  9. Tim Wescott

    Tim Wescott Guest

    No. Frankly I'm not sure what motor it might be a correct circuit for,
    and if it is a correct circuit for some motor, if that motor could exist
    in this Universe.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
  10. Tim Wescott

    Tim Wescott Guest

    Well I'll be dipped.

    I'm sorry, I was steering you wrong -- I read as far as "five leads" and
    assumed that it was a unipolar stepper with a common ground -- but that
    would only make sense if they brought all five leads out to the connector.

    It may, indeed, be a 3-phase stepper. Although I've certainly never
    heard of such there's not reason it can't be done.

    If this is the case then:

    (a) The blue, yellow and red leads should all have about the same
    resistance from lead-lead. If it's a 'Y' connected motor then the black
    and white leads together will probably have about 1/2 that much
    resistance to each of the colored leads.

    (b) Their schematic should work. It's not really a three-phase driver,
    but it should work. I think you mentioned putting LEDs on the outputs
    -- if you slow the clock way down you could see them blink.

    (c) Jeeze that's a weird clock circuit!

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
  11. The more I think about it, the more I'm inclined to think this is a '3
    phase' motor, designed for something like an aircraft. There are 400Hz 3
    phase low voltage supplies, used in quite a few avionics parts. As such,
    it can probably be driven as a stepper, but is probably designed to really
    have three sinusoidal phases, rather than simple 'steps'...

    Best Wishes
     
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