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  1. #1
    Join Date
    Feb 2015
    Posts
    113

    choose driver

    Hello everybody, I need your help choosing driver for my new machine..
    What is the best option ?
    I have 4 stepper motors (LAM TECHNOLOGIES- M1343031), I was thinking to buy one of the 3 choice I have:
    1) Leadshine (EM806)
    2) GECKO(G203V)
    3) DMS-781 (WWW.CNC-PLUS.DE)
    I need 4 drivers (for x axis I will use 2 motors - slave).
    Appreciate your help

  2. #2
    Join Date
    May 2005
    Posts
    1397

    Re: choose driver

    You can't go wrong with a gecko. If you want to save some money and if you are good at building electronic kits, my THB6064AH kit is also a good choice. DON'T buy /anything/ from China.
    James hosts the single best wiki page about steppers for CNC hobbyists on the net:
    http://www.piclist.com/techref/io/steppers.htm Disagree? Tell him what's missing! ,o)

  3. #3
    Join Date
    Feb 2015
    Posts
    113

    Re: choose driver

    Thank you James,
    I already ordered the DMS-781, they seems to be good as gecko (manufacturing in Poland - German seller), they guarantee a Good Quality and technical support if needed, and 3 years warranty. The price is the same as gecko ... So it's worth a try.
    Thank you

  4. #4
    Join Date
    Jun 2009
    Posts
    251

    Re: choose driver

    Your choice is Ok but Gecko or even better LAM Technology drives would have been better. I have and use several of Gecko (G540, G212, G320 8 in total) and LAM Tech. (5 on 2 machines) and the verdict is as folows:
    Gecko are without a doubt very high quality drives, easy to set up and use, and they can take a lot of beating.
    LAM are indestructible!!! they have just 1 flaw : to set them up, you have to use a DUP adapter they manufacture or you will end up using the drives at a factory setting of 1A and by 4 microstepping. But at 28 euro (30 $), all is good.
    Tom

  5. #5
    Join Date
    Feb 2015
    Posts
    113

    Re: choose driver

    Hello and thank you for replaying, i need help choosing power supply for my cnc machine, i already have :
    1 Breakout Board PMDX-126
    4 drivers DMS-781 ( 7.8 amperes and 100 VDC )
    4 LAM Technologies 2 phase stepper motors ( 7.1 A, 1.85 V, 0.26 Ohm, 2.2 mH (each phase))
    I need power supply to run this kit, but I don't know which one to use ! How much output voltage and amperes I need ?!

  6. #6
    Join Date
    Jun 2009
    Posts
    251

    Re: choose driver

    To drive those you are going to need a power supply with 48-80V and at least 10A, preferably 15A.
    The BOB has it's own power supply so all is good.
    Something like this would do nicely:
    https://cnc-plus.de/en/CNC-Electroni...supplies-.html

    https://cnc-plus.de/en/CNC-Electroni...e-output-.html

    For transformer choose 2X24V 600W it comes at 62 euro plus 32 for the rectifier. At 94 euro, it is a nice rugged power supply that lasts much longer than smps ones. All fuses included.

    Or this:
    Schaltnetzteil MW SP320 48V - Schrittmotoren Shop von mechapro - Ihr Spezialist f
    but you would need at least 2 for your setup.
    Tom

  7. #7
    Join Date
    May 2014
    Posts
    182

    Re: choose driver

    Quote Originally Posted by assadi View Post
    Hello and thank you for replaying, i need help choosing power supply for my cnc machine, i already have :
    1 Breakout Board PMDX-126
    4 drivers DMS-781 ( 7.8 amperes and 100 VDC )
    4 LAM Technologies 2 phase stepper motors ( 7.1 A, 1.85 V, 0.26 Ohm, 2.2 mH (each phase))
    I need power supply to run this kit, but I don't know which one to use ! How much output voltage and amperes I need ?!
    A typical approach to sizing voltage for a stepper motor is to look at it's rated voltage and multiply that value by 20-25. 1.85V x 25 = 46.25V. Meaning that would not power the motors with more than a 50V power supply. In fact, these were probably intended to be used with a 48V power supply.

    Use an unregulated power supply if you can. They accommodate back EMF much much better than switching power supplies. The voltage will decrease on an unregulated power demand increases, meaning that a 48V unregulated power supply is probably perfect.
    Unregulated Linear 960W/ 48 VDC/20A Toroidal PSU (KL-4820) | Automation Technology Inc (whatever you can find that's close to that in Europe).

    20A will be plenty for your motors as you will not be drawing full current from them at all at one time (in fact, very very unlikely).

  8. #8
    Join Date
    Feb 2015
    Posts
    113

    Re: choose driver

    CNC-Plus told me that I need 2x24 600w transformer and 4 rectifier !!! And the problem with unregulated power supply that they weight too much for shipping, I actually can get a lot of TDK lambda power supply
    Model: FPS1000-48,
    Nominal output voltage: 48V,
    Output voltage adj. range: 48V to 58V,
    Nominal: output current 21A, output power 1008W
    Is this power supply plenty for the motors & drivers ?
    What would happen if I use more voltage up to 72 ! I need a more torque at high speed .
    Thank you
    Murad

  9. #9
    Join Date
    Jun 2009
    Posts
    251

    Re: choose driver

    Yes it is plenty and you can use a 72V power supply.

  10. #10
    Join Date
    May 2014
    Posts
    182

    Re: choose driver

    Lam provides torque curves (you have to register first)

    they indicate that you can go provide up to 150V to the motor from the motor driver - so I take back my statement regarding 50V max. This is quite against a convention I am used to have and have read in multiple places.

    There may be other intended consequences of running this high of voltage/current through your motor (you may need active cooling or something). I would contact LAM about your application just to ensure you have everything covered.

    Another thing to check is if the driver (DMS-781) current is rated in Arms or Max. It says it provides 7.8amps, but does not distinguish if that is max etc. The Lam stepper motor is 7.1arms, if your driver is 7.8amps peak, then you could be slightly underpowering it.

  11. #11
    Join Date
    Feb 2015
    Posts
    113

    Re: choose driver

    I sent CNC-Plus e-mail to make sure if the 7.8 is arms or peak, as i know the current rating of the motor should be less than or equal to the current rating of your motor driver. The M1343031 Motor are 7.1arms and my driver are 7.8 amp (if it's peak) So I only would get 75% of the motor torque ?!!! 7.8amps×0.707=5.5146Arms
    (5.5146/7.1)×100= 77.67%
    And I was thinking to use maybe tow TDK LAMBDA power supply (48v×2)=96v.... But to run the DMS-781 in the maximum current*and voltage all the time i think it's not good idea !!

  12. #12
    Join Date
    Feb 2015
    Posts
    113

    Re: choose driver

    I contacted with LAM and CNC-Plus and this what they told me ...

    LAM :
    To obtain the nominal torque from the motor, you need to supply the motor with 7,1Arms that means 10Apk. I don’t know if your drive supplies rms or pk current, our drives are professional units and supply rms current, so if you use for example our DS1078 you simply need to set it to 7,1Arms.
    CNC-Plus :
    For the DMS-781 driver 7.8A is peak. However, the driver makes 6.5 RMS. You can set up your motor for 7.8A. The drivers are digital. They work also slightly different. The stepper motors have more power with our control.
    A customer has 8.0A motor - he is very satisfied.

  13. #13
    Join Date
    May 2005
    Posts
    1397

    Re: choose driver

    Does that reply make any sense to you? I'm having a hard time understanding what they are saying...
    James hosts the single best wiki page about steppers for CNC hobbyists on the net:
    http://www.piclist.com/techref/io/steppers.htm Disagree? Tell him what's missing! ,o)

  14. #14
    Join Date
    Feb 2015
    Posts
    113

    Re: choose driver

    Actually*I didn't understand anything, but I decided to buy the LAM drivers

  15. #15
    Join Date
    Feb 2015
    Posts
    113

    Re: choose driver

    But the DMS-781 drivers seems to be a good as the gecko (based on the specification), and thank you all for replaying

  16. #16
    Join Date
    May 2014
    Posts
    182

    Re: choose driver

    They are saying that the motors are rated for 7.1Arms, and that the driver is rated for 7.8 peak current. In order to appropriately size a driver to the motor, you want a driver that supplies 7.1arms. Mostly all drivers are rated for peak current output.

    A peak output of 7.8 amps equates to ~5.52arms (7.8 amps peak/1.41 = 5.5armss, or 7.8*.707=5.5), or about ~23% less current than the max rating of your motor. Motor torque is linearly proportional to the current you are providing it; if you provide it with 77% of the current of the current/phase value, then you will receive 77% of the rated torque. Supplying the Lam M1343031 stepper motor with 5.5amps (rms) will give you 741.5oz-in of torque from the motor (with the motor being rated at 963oz-in at a full 7.1arms supplied).

    It's counter-intuitive (maybe slightly deceptive?) that a driver current rating would be max current value while a motor current rating is specified at RMS current values.

    In short, to receive the fully rated torque values, use driver/motor combinations with the following ratings:

    ~3amp (2.82) peak driver for a 2arms stepper
    5amp peak driver for a 3.5arms stepper
    7amp peak driver for 5arms stepper
    10amp peak driver for 7arms stepper


    Most drivers wont tell you if it's a peak current value or an amps rms value - but I imagine that most would err on the "peak current" side for marketing purposes. You should always contact the manufacturer if it is not stated.

    This is why I will be using closed-loop stepper drivers (they servo the stepper motor). 5amps peak continuous (3.5amps rms continuous), and 7amps (5amps rms continuous) for my nema34 motors. I have the option of buying steppers rated anywhere from 3.5arms to 5arms, and either underpowering the 5arms and getting percentage of their torque value and 100% torque when needed, or using the 3.5arms stepper motors and getting greater than >100% torque when needed. Either way, current is only applied when it is demanded (encoder position change as feedback loop) so it will be much more energy efficient and should extend the life of the motors.

  17. #17
    Join Date
    Feb 2015
    Posts
    113

    Re: choose driver

    learning from failure, actually it's not failure (just 77% of the rated torque), now I will buy the LAM DS1078 driver rated 4.0-10.0A (RMS) respectively 5.6-14.1A (peak) each phase. I guess the PMDX-126 witch I already have will work with these drivers and motor, but I still have a doubt about the power supply that I will use and as I already paid the CNC-Plus so I will buy the power supply from them.. But I still need help choosing the plenty one, and again thank you guys your help is greatly appreciated
    Murad assadi

  18. #18
    Join Date
    Feb 2015
    Posts
    113

    Re: choose driver

    Hello,
    Again I contacted LAM after I decided to use their drivers DS1078, and I asked which power supply they recommend and they answered me " we suggest you to use a power supply with 80Vdc output voltage and 12A output current. You can use a 1KVA transformer with 60Vac output voltage if use DS1078A" so my question is : do I need 4 power supply with 80vdc and 12amp output for each motor or they mean 1 power supply for the 4 axis ?!

  19. #19
    Join Date
    Jun 2009
    Posts
    251

    Re: choose driver

    Safer would be to have two power supplies, although one should do the job but would be working at an upper limit. All 4 drives set at 7A should draw about 8-10A from power supply at 80V but it will go higher when motors start moving. In one machine i have 4 LAM drives at 4A each and a power supply of 48V 8A and it never even gets warm.
    Oh and do NOT forget to order a DUP programmer for LAM drives or you will be stuck at 2A per drive. it is only 28 euro but you can not program anything on the drives without it.
    Tom

  20. #20
    Join Date
    Feb 2015
    Posts
    113

    Re: choose driver

    Thanks tommy for your help, I didn't mean to ask almost the same question in different posts ... It just happened from the reason that I'm new to CNC machine and I don't want to damage the motor or driver.
    Have a nice day

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