Stepper motor driver

Discussion in 'General Electronics Chat' started by Dritech, Mar 28, 2014.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    Hi all,

    I was planning to use a DM556 module to drive two stepper motors (not at the same time). My plan is to connect SPDT relays at the output of the driver to select which motor to drive.
    Is this possible or will the driver trigger a fault when switching relays?
    Some told me that the driver can be damaged from inrush current every time I switch relays. To eliminate this problem I am planning to disable the driver before switching relays and then re-enable them. Will constantly disabling and enabling the driver cause any damage?

    The reason that I do not want to but two drivers is because I am limited with space and have limited budget.

    Your help will be highly appreciated.

    Driver datasheet: http://www.leadshine.com/UploadFile/Down/DM556m.pdf

    Thanks in advance.
     
  2. crutschow

    Expert

    Mar 14, 2008
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    I see no problem with switching the outputs with relays, and frequently disabling the driver will have no effect on its reliability. Note that you can use one DPDT relay for this purpose. You can switch one wire of the A-side and one wire of the B-side while connecting the other two A and B side wires in common.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    What you will have to be aware of is that steppers are non-closed loop servo's, so in switching back and forth with one drive disabled, if an axis is moved such as in a Z axis where the weight has to be held, it could be possible for the axis to move off position before being re-enabled and the system will not be aware of it.
    Max.
     
  4. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Thanks for the replies.

    I will be using a rotary encoder to monitor the position of the motor.
    Another quick question, is the DM556 suitable for driving the SY85STH80-4208A stepper motor?
     
    Last edited: Mar 28, 2014
  5. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    I don't think Max was talking about remembering position of the axis. the stepper motors in this, cnc, usually keep one winding energized to keep the axis from moving, while to axis are doing there thing. Without the one winding on the stepper can "freewheel".
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Personally if using an encoder on a stepper, you may as well go with a closed loop servo, (PID) loop, which is far superior.
    Max.
     
  7. Brainbox

    Member

    Nov 15, 2010
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    With the DM556 the two motors have to be exactly the same.
    This digital controller wil do a test for the low, mid and high range resonance and stores the results as parameters to avoid stalling.
    Two no indentical motors will have non indentical charactersitics.
    The controller can apply the wrong parameters to a different type of motor resulting a less smooth running.
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Possibly! It is a bad practice to keep turnign the power to a stepper motor driver module on/off all the time.

    I understand your point, but you are up for one relay or other device to turn off the power to the driver, and 2 more DPDT relays to select which motor it drives. The space to mount all that is significant, then you have to add in the time and complexity and risk of problems.

    How large are your two motors? Can you state the motor specs?

    There are a lot of small cheap stepper motor driver modules you can buy. Two cheap modules might be the best way to go.
    :)
     
  9. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    Hi THE RB,

    I was going to disable the driver using the MCU. The driver has a dedicated pin to disable/enable the driver (ENA+ and ENA- pin).

    For the motor selection relays, I think that one DPDT will do. As crutschow suggested, I can switch one wire of the A-side and one wire of the B-side while connecting the other two A and B side wires in common.

    The stepper motors which I will be driving are SY85STH80-4208A (2 pieces). I think there is no such small and cheap modules to drive such stepper motors.

    Thanks a lot for your replies and suggestions :)
     
  10. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Must be a pretty big cnc! Most home built machines use a NEMA23 instead of a NEMA34.
     
  11. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    To be honest I am not yet sure about which stepper motors to buy. Lets assume that I buy the GB24H288-40-4A (NEMA 24).
    On E-bay I found the
    M542 stepper driver which is much less expensive than the Leadshine DM556.
     
  12. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    There are tutorials online about choosing motors and drives. Without knowing what your making, only you can answer the questions. No matter what driver you end up with, don't make the mistake of using the motor 'name plate' voltage for the power supply. Use as close to the drive maximum input voltage level as you can get.

    Like the others said, I'd never try running two different axis on one driver with a switch/relay. You won't be happy with the results. What are you building that only has two axis?


    Do you know about - CNCZone.com ?
     
  13. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I'm pretty sure that pin is not designed to make the driver "safe" for you to disconnect the motor wires while it is still powered up.

    Disconnecting the motor wires on a live driver module is a very bad idea.
     
    shortbus likes this.
  14. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    Do you know of an easy to follow tutorial to determine the torque required please? I did find some online tutorials/online calculators but they were requesting data which I do not know.
     
  15. MaxHeadRoom

    Expert

    Jul 18, 2013
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  16. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    There are links in the forum at cnczone, do a search there. I lost all of my links when my other computer died. But like Max said, Gecko is as good a place as any to start -
    http://www.geckodrive.com/support.html
     
  17. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    Hi again,

    I bought the CW5045 driver (datasheet: http://cnc4you.co.uk/resources/CW5045.pdf ). Can someone explain to me how to change the stepper motor speed please?

    Do I change the speed by applying PWM to pin PUL+ ? If so, what determines the speed, the frequency or the pulse width?

    Thanks in advance.
     
  18. MaxHeadRoom

    Expert

    Jul 18, 2013
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    A stepper drive is controlled with a step and dir pulse, the frequency of the step pulses control the RPM.
    Max.
     
  19. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    Thanks for the reply. How to determine the frequency range please?
     
  20. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The limit is set to some degree by the voltage of the supply and the inductive characteristics of the motor, in this case it is 20v-50v is the voltage range, with a stepper motor, the mean voltage level is increased by the drive to overcome the increase in inductive reactance with pulse frequency.
    Some of the sites such as Gecko give approximate figures for performance expected for certain motor characteristics.
    Max.
     
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