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IndustryArena Forum > CNC Electronics > Stepper Motors / Drives > Problems with Japan servo KY series stepping motors
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  1. #1
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    Problems with Japan servo KY series stepping motors

    I recently bought 4 of these, older models, new in the box never used, but have a strange problem.
    They have 4 coils, 8wires but apparently I can't find the correct wiring.
    I can get them to turn but they step at 1.8 degrees and the sticker says 0.9 degrees... , also it looks like they don't produce the correct torque.
    Can't find more info on the web, googled for hours: nothing, only their recent models.
    Is there anybody out there with a wiring diagram or even better: a datasheet?

    Sticker info:
    Type: KY56RM1-551
    DC 3V
    0.9 deg/step
    They are Nema23 and 80mm long

    It would be a waste of money and time if I can't get them working properly so any help is very much appreciated, would really like to use them.

    Thanks,
    Luc.

  2. #2
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    Are you running uni or bi polar? (ie: 6 or 4 wire) What driver and voltage are you using?

    The torque rating is usually for bipolar parallel since the number is the highest. It is not hard to figure out the correct wiring. If you cant find specs, I can help once you give more details. One word of warning, if you incorrectly hook up the bipolar parallel config, you might damage the motor and driver.

  3. #3
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    Bipolair series on Picstep at 33V 1.5A in fullstep mode but want to use them in bipolair parrallel and microstepping.
    I found several wiring combinations wich seem to work, wires are marked on the sticker:
    A A-
    B B-
    C C-
    D D-
    Coil 1 driver to A, A- to B, B- to driver and coil 2 driver to C, C- to D, D- to driver works and also:
    Coil 1 driver to A, A- to C, C- to driver and coil 2 driver to B, B- to D, D- to driver.

    But the motor steps at 1.8 degrees iso the 0.9 marked on the sticker.
    This makes me think there's something wrong although the motor spins with reasonable force.

    Thanks in advance for your help.

  4. #4
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    Since your voltage is quite low, you will get MUCH better speed when you switch to parallel.

    You will need a 3-5 volt power supply, or a power resistor to limit you current to .5-2 amps.

    1. Energize coil A momentarily. The coil will step into position. Keep track which is wire got the + and - from the supply.

    2. To find the proper coil to parallel, power the other 3 coils, one at a time. The proper coils (and power polarity) is the one that results in NO change of rotor position when energized. If the rotor moves, repeat step 1 before going to the next coil.

    3 If all 3 coil fails, reverse the polarity try all 3 coils again. BUT, MAINTAIN THE ORIGINAL POLARITY ON COIL A!

    4 When the coil is found, hook it in parallel with coil A. If you failed to find one, you done something wrong.

    5 Now pick one of the remaining 2 coils and repeat step1. Then energize the other coil. If the rotor moves, reverse the polarity on this coil. Tie them in parallel.

    6 At this point you have a bipolar parallel motor.

    7 To double check, energize one phase. The rotor will lock place. Move the supply to the other phase. Once again it will lock. If either fail to lock, you done something wrong. WARNING: do not proceed to step 8 if either fails to lock. You could kill both the motor and driver.

    8 Hook motor up to your picstepper.

    9 Open large can of beer and promptly empty contents into mouth.

  5. #5
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    Really weird motor

    H500, thanks for your detailled post, I did most of it when I received the motors several weeks back and did everything again this morning hoping to arrive at this:

    Quote Originally Posted by H500
    9 Open large can of beer and promptly empty contents into mouth.
    But no luck.

    I used a 3V power supply limited at 2 Amps and kept the "A" coil under power while trying the combinations of the 3 other coils.
    There should be one out of the 6 combinations wich doesn't move the motor, well not on this one.
    To clearly see the movement of the motor I put a 8cm lever on the shaft and it always steps away for all 6 combinations, some combinations more than others.
    There are 2 coils where the motor slightly steps in one direction and when polarity is reversed it makes a bigger step.
    The 3th coil gives an equal step in both directions when reversing polarity.

    I did the sequences 3 times to eliminate mistakes, same result.

    Could this be a special motor? Certainly looks like it.

  6. #6
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    Why don't you try driving it as bipolar 1/2 winding. It should still be much better than the series mode you're using. Set the picstepper to full step and see if your steps are all equal. If some steps are bigger than others, then you might have an unusual motor.

  7. #7
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    It looks like I figured it out :wee:

    Almost all 8 wire steppers are bifilar wound and can be used as unipolar, bipolair series or parallel.
    I removed the rear endcap and had a peek inside the motor without disassembling it.
    It didn't look like bifilar windings to me but more like monofilar as an ordinary 4 wire bipolar motor and that each winding was split in half.
    This would mean that it can't be used as unipolar but still has the options of bipolair series or parallel. Still appeared very strange as I never heard or read about a motor like this.

    But why did I obtain those strange step patterns, this still didn't make sense. I tried to find it out by using an 8 pole hybrid diagram and it did not yet correspond with my practical results, sigh.......
    There had to be something, then I remembered that this motor had 16 poles and now I could see why it acts like this.

    I won't try to explain in detail, it would take a lenghty post (unless somebody wants me to AND has a nice drawing of a 16 pole hybrid stepper, I couldn't find one).

    The way to identify the matching coils for an 8 wire stepper wich H500 (and others on the net) describe here are true for:
    - bifilar wound motors.
    - monofilar 8 pole motors.
    - But for monofilar 16 pole motors: well it depends on how the windings are split.

    I know this is probably a very rare motor but hope this will help someone in the future.

    Have to rush now, will post the correct connections after I tested the motor in real life on a machine.


    Edit:
    H500: you replied whilst I was typing this.
    I did have steps of different sizes but managed to find the correct wiring resulting in good steps.
    If you want more details, let me know.

    Thanks and regards,
    Luc.


    Oops, almost forgot: :cheers: :cheers: :cheers: :cheers:

  8. #8
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    Interesting..... Since each coil have a different detent position, are you able to parallel them without the fields fighting against each other?

  9. #9
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    I didn't work it all out in detail, what the exact pole positions are for each combination of the 4 coils, nor am I sure that the motor is driven as it should be to obtain it's best performance. Also it still doesn't step at 0.9 deg.
    The more I think about it: it could very well need 4 H-bridges, then it will step at 0.9 iso of 1.8 as it does now.

    Here's a basic explanation for the 4 coils haven 4 different detent positions.
    Have a look here at figure 1B on page 2.
    http://www.clickautomation.com/PDF/c...%20Catlog).pdf

    This shows a bipolair 8 pole motor in a position where only the A winding is actvated, and that only the teeth on the Acc poles are aligned with the rotor theet.
    My motor has 16 poles, they are smaller (3 teeth) and they are between the ones on the drawing, leave the A's where they are, shift every B 22.5 degrees CCW and insert a C and D pole in the created gap to obtain A B C D A B .......
    There's a seperate winding for each of the 4 poles, let's also call them A..D

    Now if I you activate the A winding only: still only the 2 Acc poles are aligned but every additional activated coil will create some step (different size) of the motor.
    This explains the strange test behaviour.

    Activating the A and B winding at the same time and same polarity generates 2 adjacent poles wich act like a single big one, same for C and D: the net result is an 8 pole motor like on the drawing.
    One more detail: the drawing has a "missing" teeth between every stator pole, mine does not, so the A and B together act like a complete pole with the 2 center teeth perfectly aligned with the rotor.

    I use it like this, it's creating equal step sizes but still at 1.8 degrees.
    Its probably not the ideal or intended way for this type of motor, maybe 4 H bridges are required to get the most (and the 0.9 deg.) out of it.
    If we want to know for sure we'll need the datasheet of this (or a similar) motor.

    Hope you understand what I try to explain, a 16 pole drawing would make it easier but my CAD skills don't allow it.

    Do you see any flaws in all this?

  10. #10
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    I would expect all teeth on the closest stator coils to line up with any energization sequence, but I could be wrong.

    Perhaps the easiest way to determine if your configuration is optimal is thru experimentation. Hook it up one way and then see what your max rpm is, then try the others.

    By combining microstepping with the proper mechanical ratios, you step resolution should easily exceed the mechanical capabilities of your machine. My motors are 2 degree and still, resolution has been the limiting factor on my mill.

  11. #11
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    I have been working on and off on this but no improvement, it looks like I can use these motors with a normal bipolair driver but nowhere near their potential. The max speed is OK but torque is not compared to similar size and age motors.

    H500: Maximum 2 teeth can be aligned at any one time because the stator has 48 and the rotor 50. so only the 2 opposite teeth align. And this is even only the case in some step sequences, when microstepping is used they are almost never fully aligned.

    @ All: I really would like to have some more info on these type of steppers so that I can use them properly and not have waisted a bit of good money on 4 now useless motors.
    If I made a mistake by buying these, so be it: lesson learned, but I would still like to know the details, theory behind it for education....

    Any takers? Mariss..?

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