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Stepper motor driver voltage.

Discussion in 'Sensors and Actuators' started by zokka, Mar 14, 2010.

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  1. zokka

    zokka

    11
    0
    Mar 9, 2010
    hello,

    I want to control a stepper motor. I have driver but its output is 5V :confused:
    I need higher voltages.
     
  2. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Well, can't you just apply a higher supply voltage to the driver you have?
    If you don't know then please at least tell us the name of your driver.
     
  3. zokka

    zokka

    11
    0
    Mar 9, 2010
    Unfortunately, it isn't with me. I made hobby CNC, but it is too slow. i want to use bigger stepper motors. My stepper motor driver provides 5V, but i want to use 60V.
     
  4. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Ok. Well, there are surely hundreds of driver IC's available to choose from..
    Do you need it to be an IC or can you make do with transistors?
    What configuration is the steppers you have in mind?
     
  5. zokka

    zokka

    11
    0
    Mar 9, 2010
    i can do it with transistors, but i don't know which transistor is useful for it?
    old circuit is working, can i upgrade it with transistors?
     
  6. zokka

    zokka

    11
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    Mar 9, 2010
    I want to use 60V DC - 6A stepper motor
     
  7. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    The easiest thing to do is to buy a stepper motor driver module. If you want to build a driver yourself, there are a number of driver ICs that can drive the MOSFETs that drive the stepper. 6A/60V may be too much for integrated ICs, but some may exist.

    ---55p
     
    Last edited: Mar 14, 2010
  8. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    Let me ask a question that I seem to be the only one interested in: What is your goal? I mean your big picture goal?

    Is your goal to upgrade your manual mill to a CNC mill and you are building the stepper motor controller because that is required to achieve your goal? Or is your goal to learn about stepper motor drivers and the CNC mill happens to be what you chose to apply that knowledge to? That is an important question and the path I recommend for you will be based on your answer.

    In short, if your goal is to make yourself a CNC mill, I would recommend that you look at buying a stepper motor driver or maybe even a full controller. Doing a 60V, 6A driver does not require black magic, but it is not trivially simple either. If learning to build one is not your goal, you may want to consider buying.

    Before you talk about the cost of buying one, think about the big picture cost. If your controller is not really well designed, it may miss a step when over-loaded. What is the cost to you if you are a little aggressive in your feed rate and one of the axes skips a step and you end up having to scrap the piece? What happens if the tool chatters and the table is not able to feed correctly because the motor is unable to handle the additional load and you have to scrap the piece? Those concerns are much less if all you are doing is wood and much worse if you are planning on doing steel.

    And to answer your question, you will not be able to just upgrade the transistors in your current circuit and apply a higher voltage. You will need drives that can drive the higher voltage transistors and you will really have to consider switching from transistors to MOSFETs because at 6A current, a MOSFET makes a lot more sense than a transistor.

    ---55p
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,363
    2,758
    Jan 21, 2010
    Further to 55p's comment, upgrading from bipolar transistors to mosfets in a typical output arrangement for these devices, you have to consider the dead time between switching one mosfet off and switching the other one on.

    With bipolar transistors this pretty much takes care of itself, but mosfets switch in a different way and it often happens that when switching one off and another on that both remain on for a brief period. This results in effectively shorting out the power supply very briefly. Working designs at moderate to high power levels need to take this into account.

    There are mosfet drivers available that are driven by logic levels, and I would not be surprised if some have some ability to introduce dead time. Since your existing voltage level is 5V, it would not be too hard to use one of these to drive power mosfets. I'm not sure if 60V exceeds their voltage ratings, but you could go shopping...
     
  10. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    The NPN/PNP transistor arrangement that guarantees no shorts is horribly inefficient and not appropriate for anything other than very low currents.

    Almost all decent bridge drivers guarantee dead time between switching, as long as the driver is properly sized for the MOSFET. But if you use independent high side and low side drivers, then you are responsible for providing dead time. As Steve has pointed out, if you mess up on that one, the whole driver can melt down in a hurry. The use of the expression "melt down" is not an exaggeration or figure of speech.

    60V is well within the scope of driver chips. Chips are usually rated on the drive voltage for the MOSFET so if you are running a 60V power supply, you want to start with a 80V or higher driver chip.

    The problem that may be encountered for this application is that most of the drivers use a technique called bootstrapping to get the drive voltage for the top MOSFET, which has to be 10V to 20V higher than the power supply voltage. Bootstrapping counts on the MOSFET being off for a certain percentage of time to recharge the bootstrapping capacitor. This will impose a lower limit on the minimum speed of the motor. If the motor moves at all, it has to do xx steps pers second. That can be overcome by adding more functionality in the controller so if the speed is too slow, the controller turns off the phase briefly then resumes at the same phase. It is all doable, but it is these little gotchas that make the design complicated and make the difference between something that works most of the time and one that works all the time.

    ---55p
     
  11. mpx96

    mpx96

    8
    0
    Mar 25, 2010
    I agree with 55pilot's comments. Having worked with many custom stepper controllers over the years, companies like copley have really done their homework to match the impedance and phasing of the exact motor your using to the control system. You'll pull out your hair designing circuits that stall, burn up, or don't have enough current to do what you want. The controllers these days available have features like electronic gearing, pulse up/down, velocity, or PWM input, current limit, stall detection (important), and simple motion command profiles that more than pay for themselves in the long run. Good Luck on your project.
     
  12. zokka

    zokka

    11
    0
    Mar 9, 2010
    i'm sorry i haven't been here for a long time.

    i bought a new driver card (it offers 40V 3Amps) and i am satisfied with it.
    Additionally, i researched some documents about stepper motors and drivers and i understand crucial points to control them. I also read your all beneficial advices and information.

    thanks for all explanations.
     
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