+ Post New Thread
Results 1 to 19 of 19
  1. #1
    Full Member level 2
    Points: 2,048, Level: 10
    Achievements:
    7 years registered
    ismu's Avatar
    Join Date
    May 2009
    Location
    nil
    Posts
    141
    Helped
    0 / 0
    Points
    2,048
    Level
    10

    Doubt on stepper motor ratings

    hi am using SY57STH76-2804A stepper motor , which datasheet rating is
    3.2v , 2.8A and Coil resistance 1.13Ohms .

    1-so can drive thios motor with 12v/24V ?
    2-When i drive with 12V then current will be =12/1.13=10.6A
    3- what is the impact of coil inductance? what should i take care on designing?

  2. #2
    Advanced Member level 5
    Points: 12,988, Level: 27

    Join Date
    May 2015
    Location
    Melbourne, Australia
    Posts
    2,213
    Helped
    748 / 748
    Points
    12,988
    Level
    27

    Re: Doubt on stepper motor ratings

    The usual way to do this is to drive it with 12v/24v but with a current limited supply set to 2.8A (or less).

    The higher supply voltage will produce a very fast ramp up of current in the inductive motor windings, right up to the current limit value.
    This makes much faster stepping rates possible, and with higher torque when running fast.

    If you do not need the speed just run the motor at 3.0 volts.
    Cheers, Tony.


    1 members found this post helpful.

  3. #3
    Full Member level 2
    Points: 2,048, Level: 10
    Achievements:
    7 years registered
    ismu's Avatar
    Join Date
    May 2009
    Location
    nil
    Posts
    141
    Helped
    0 / 0
    Points
    2,048
    Level
    10

    Re: Doubt on stepper motor ratings

    what is the meaning of rated voltage 3.2v ? then how can give >3.2v?



  4. #4
    Advanced Member level 5
    Points: 12,988, Level: 27

    Join Date
    May 2015
    Location
    Melbourne, Australia
    Posts
    2,213
    Helped
    748 / 748
    Points
    12,988
    Level
    27

    Re: Doubt on stepper motor ratings

    hi am using SY57STH76-2804A stepper motor , which datasheet rating is
    3.2v , 2.8A and Coil resistance 1.13Ohms .
    Those are the CONTINUOUS ratings for drive with direct switched dc current.

    You can run it like that but it will be slow, and torque will fall off with increasing speed.
    Cheers, Tony.


    1 members found this post helpful.

    •   Alt11th March 2016, 05:47

      advertising

        
       

  5. #5
    Super Moderator
    Points: 228,812, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    39,443
    Helped
    12060 / 12060
    Points
    228,812
    Level
    100

    Re: Doubt on stepper motor ratings

    The usual way to operate a stepper motor at higher voltage is to apply PWM with current regulation.


    1 members found this post helpful.

  6. #6
    Full Member level 2
    Points: 2,048, Level: 10
    Achievements:
    7 years registered
    ismu's Avatar
    Join Date
    May 2009
    Location
    nil
    Posts
    141
    Helped
    0 / 0
    Points
    2,048
    Level
    10

    Re: Doubt on stepper motor ratings

    if i use 12v supply instead of rated 3.2v [datasheet rating is 3.2v , 2.8A and Coil resistance 1.13Ohms .]
    then how much should be the Driver chip H bridge driver current capability ?
    i have seen in some case rated volt is less still people are driving with high voltage, any reason?



  7. #7
    Super Moderator
    Points: 228,812, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    39,443
    Helped
    12060 / 12060
    Points
    228,812
    Level
    100

    Re: Doubt on stepper motor ratings

    The motor driver should implement constant current operation, maximum current is rated 2.8 A.



  8. #8
    Advanced Member level 4
    Points: 7,444, Level: 20
    Easyrider83's Avatar
    Join Date
    Oct 2011
    Location
    Tallinn, Estonia
    Posts
    1,328
    Helped
    315 / 315
    Points
    7,444
    Level
    20

    Re: Doubt on stepper motor ratings

    Just use fixed PWM duty cycle to get proper current.
    Love me or hate me. All infractions will be ignored.



  9. #9
    Advanced Member level 5
    Points: 12,988, Level: 27

    Join Date
    May 2015
    Location
    Melbourne, Australia
    Posts
    2,213
    Helped
    748 / 748
    Points
    12,988
    Level
    27

    Re: Doubt on stepper motor ratings

    A more simple and very crude way to do this is to fit external resistors to each winding.

    If its driven with 12v and you want 2.8 amps, then total resistance needs to be 4.285 ohms.

    The stepper already has 1.13 ohms, so add a 3.15 ohm resistor.
    3R3 would be about right.
    That's a huge 26 watts of power dissipation which really makes it impractical, but it is one possible solution.
    Cheers, Tony.


    1 members found this post helpful.

    •   Alt22nd March 2016, 22:53

      advertising

        
       

  10. #10
    Full Member level 2
    Points: 2,048, Level: 10
    Achievements:
    7 years registered
    ismu's Avatar
    Join Date
    May 2009
    Location
    nil
    Posts
    141
    Helped
    0 / 0
    Points
    2,048
    Level
    10

    Re: Doubt on stepper motor ratings

    Quote Originally Posted by FvM View Post
    The motor driver should implement constant current operation, maximum current is rated 2.8 A.
    you know any example circuit to get constant current to motor? and should be cheapest way

    - - - Updated - - -

    Quote Originally Posted by Easyrider83 View Post
    Just use fixed PWM duty cycle to get proper current.
    for driving bipolar stepper mototr ,we wrer using pulsed signed on A, A+ ,B, B+ terminal , then how can i make again PWM on this ? can you please draw a simple wave form for half drive signal with PWM ?

    - - - Updated - - -

    Quote Originally Posted by Warpspeed View Post
    A more simple and very crude way to do this is to fit external resistors to each winding.

    If its driven with 12v and you want 2.8 amps, then total resistance needs to be 4.285 ohms.

    The stepper already has 1.13 ohms, so add a 3.15 ohm resistor.
    3R3 would be about right.
    That's a huge 26 watts of power dissipation which really makes it impractical, but it is one possible solution.
    agree.... ! But am driving with 12v Source and motor rating is 3.2v ,,, will it damage?



  11. #11
    Advanced Member level 5
    Points: 12,988, Level: 27

    Join Date
    May 2015
    Location
    Melbourne, Australia
    Posts
    2,213
    Helped
    748 / 748
    Points
    12,988
    Level
    27

    Re: Doubt on stepper motor ratings

    agree.... ! But am driving with 12v Source and motor rating is 3.2v ,,, will it damage?
    Not if you use a 3R3 resistor.

    But the resistor is going to get mighty hot.
    Cheers, Tony.


    1 members found this post helpful.

  12. #12
    Advanced Member level 4
    Points: 7,444, Level: 20
    Easyrider83's Avatar
    Join Date
    Oct 2011
    Location
    Tallinn, Estonia
    Posts
    1,328
    Helped
    315 / 315
    Points
    7,444
    Level
    20

    Re: Doubt on stepper motor ratings

    Quote Originally Posted by Warpspeed View Post
    A more simple and very crude way to do this is to fit external resistors to each winding.
    That's not funny, man! You will reduce efficency 5 times. 2.8A * 20V will give 56W power lost on each!

    - - - Updated - - -

    Quote Originally Posted by ismu View Post
    for driving bipolar stepper mototr ,we wrer using pulsed signed on A, A+ ,B, B+ terminal , then how can i make again PWM on this ? can you please draw a simple wave form for half drive signal with PWM ?
    Just take a PWM frequency 10 times higher than expected step time. For example, if you planing to use 1ms step time, 1kHz per step, use 10kHz or higher PWM frequency. I suppose, 1/10 duty cycle will be good enought. But this is actual only for 'on hold' static mode. For movement PWM duty cycle have to be calculated according constand current law. But if you not planing to use variable frequency, just find a good value for duty cycle that gives you expected force and current. It can be lower than maximum rating shown on sticker.
    Last edited by Easyrider83; 23rd March 2016 at 07:49.
    Love me or hate me. All infractions will be ignored.


    1 members found this post helpful.

  13. #13
    Super Moderator
    Points: 42,951, Level: 50
    Awards:
    Most Frequent Poster

    Join Date
    Apr 2014
    Posts
    8,781
    Helped
    2117 / 2117
    Points
    42,951
    Level
    50

    Re: Doubt on stepper motor ratings

    Hi,

    External resistors make no sense because of their huge power loss = heating. But for sure it prevents the stepper from overload.

    A fixed pwm does not give the same benefit as a constant current source regarding stepper speed. But for sure it is a way to drice the stepper with 12V.

    There are a lot of stepper driver ICs with pwm controlled current source. All of them have different price .. and availability.

    You say "the cheapest way".
    With the resistor solution..the huge resistors may not be cheap. You need a power supply able to give the motor power and the resistor power, maybe heatsink, baybe fans. Is it cheap?

    The constant pwm solution...has good efficiency, so you need a smaller power supply, smaller heatsink, maybe no fan. Maybe this is the cheapest way.

    The constant current pwm IC solution is the most flexible. Good efficiency, high motor speed. Power supply is somewhere inbetween the above solutions, depending on motor speed. Small heatsink, maybe no fan.

    So it's on the OP to select the "best solution for him". I recommend to go to a distributor site for stepper motor driver ICs and find "cheap" IC with all the specifications, read through datasheets and compare them...
    (Try farnell, digikey, mouser ...)

    Hope this helps, although you need to spend some time.
    Good luck

    Klaus

    - - - Updated - - -

    Added to easyrider's post:
    I suppose, 1/10 duty cycle will be good enought.
    Just to safe the motor from overcurrent the max duty cycle is: (raw estimation)
    Motor_voltage / Supply_voltage = 3.2V /12V = 0.266 = 27%.

    For a true constant current it will move from 100% down to about 27% after each step.

    Klaus


    1 members found this post helpful.

  14. #14
    Advanced Member level 5
    Points: 12,988, Level: 27

    Join Date
    May 2015
    Location
    Melbourne, Australia
    Posts
    2,213
    Helped
    748 / 748
    Points
    12,988
    Level
    27

    Re: Doubt on stepper motor ratings

    I agree fixed resistors are an ugly solution.

    But some low impedance automotive fuel injectors still use series ballast resistors to achieve pretty much the same thing.
    Cheers, Tony.



  15. #15
    Advanced Member level 4
    Points: 7,444, Level: 20
    Easyrider83's Avatar
    Join Date
    Oct 2011
    Location
    Tallinn, Estonia
    Posts
    1,328
    Helped
    315 / 315
    Points
    7,444
    Level
    20

    Re: Doubt on stepper motor ratings

    Quote Originally Posted by KlausST View Post
    Just to safe the motor from overcurrent the max duty cycle is: (raw estimation)
    Motor_voltage / Supply_voltage = 3.2V /12V = 0.266 = 27%.
    My calculations for 24V
    Love me or hate me. All infractions will be ignored.



  16. #16
    Super Moderator
    Points: 228,812, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    39,443
    Helped
    12060 / 12060
    Points
    228,812
    Level
    100

    Re: Doubt on stepper motor ratings

    Constant pwm works like lower constant voltage and doesn't bring the advantage of constant current: faster phase current rise and thus higher speed. At best you get faster current decay in free wheeling which is restricted in a low voltage bridge driver.



    •   Alt23rd March 2016, 09:22

      advertising

        
       

  17. #17
    Advanced Member level 4
    Points: 7,444, Level: 20
    Easyrider83's Avatar
    Join Date
    Oct 2011
    Location
    Tallinn, Estonia
    Posts
    1,328
    Helped
    315 / 315
    Points
    7,444
    Level
    20

    Re: Doubt on stepper motor ratings

    Sure, for real device purpose there are a lot of difficult calculations have to be performed for proper accelaration and perfomance.
    Love me or hate me. All infractions will be ignored.



  18. #18
    Full Member level 2
    Points: 2,048, Level: 10
    Achievements:
    7 years registered
    ismu's Avatar
    Join Date
    May 2009
    Location
    nil
    Posts
    141
    Helped
    0 / 0
    Points
    2,048
    Level
    10

    Re: Doubt on stepper motor ratings

    Quote Originally Posted by Easyrider83 View Post
    That's not funny, man! You will reduce efficency 5 times. 2.8A * 20V will give 56W power lost on each!

    - - - Updated - - -


    Just take a PWM frequency 10 times higher than expected step time. For example, if you planing to use 1ms step time, 1kHz per step, use 10kHz or higher PWM frequency. I suppose, 1/10 duty cycle will be good enought. But this is actual only for 'on hold' static mode. For movement PWM duty cycle have to be calculated according constand current law. But if you not planing to use variable frequency, just find a good value for duty cycle that gives you expected force and current. It can be lower than maximum rating shown on sticker.
    thanks ,, understood



  19. #19
    Advanced Member level 5
    Points: 12,988, Level: 27

    Join Date
    May 2015
    Location
    Melbourne, Australia
    Posts
    2,213
    Helped
    748 / 748
    Points
    12,988
    Level
    27

    Re: Doubt on stepper motor ratings

    Jut try running the stepper motor at reduced current and see how it performs.
    It may have sufficient speed and power for your purpose at only half an amp.
    You will never know unless you try it.

    In that case, some 22 ohm resistors running off 12v might be all you need.
    Power would be about six watts which should be tolerable.
    Cheers, Tony.



--[[ ]]--