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Controlling Twelve Steppers

Discussion in 'Sensors and Actuators' started by Holychachi, May 29, 2013.

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  1. Holychachi

    Holychachi

    4
    0
    Jul 12, 2011
    Hey guys,
    I am pretty much new to electronics so any and all advice you can afford me would be helpful and greatly appreciated!
    As you can tell from my title, I have a very ambitious goal, especially for a beginner. I know much of the advice I initially receive will be start with controlling one stepper and learn, then work your way up...which makes sense, and I don't fully intend to go full bore first go round.

    From what I've read so far it seems just about the only way to go about driving 12 steppers is to get 6 or 12 driver boards, depending on how many motors per board it supports. Is this the case? What about the breakout board sparkfun sells that is for multiple servos? Will that not work with steppers? Yes...laugh it up, but you were once in my shoes as well.

    I look forward to any help you guys can offer.
    Thanks so much!
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    Well, you'll probably need a 12 stepper program.
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    That was an awful pun, wasn't it?

    Seriously though...

    Think of the steppers as the arms and legs of your device, the drivers as the muscles, and the microcontroller as the brains. That pretty much describes the relationship and the function of the parts.

    Whether you need 1, 2, 4, 6, or 12 driver boards is not really the concern. You need a driver for each stepper motor. If they come with more than 1 on a board, then you need less boards.

    Stepper motor drivers and servo drivers are different beasts.

    The microcontroller will need to be able to communicate with all 12 drivers. Depending on how they're configured you may need a lot of outputs. Finding a solution that consumes the fewest number of pins may be a distinct advantage.

    As for laughing or criticising you, well, I wouldn't do that without walking a mile in your shoes (and you probably know the rest of that very old joke)
     
  4. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Steve,

    I can do even worse:

    12 steppers can only be controlled by a higher power.

    Bob
     
  5. Lord_grezington

    Lord_grezington

    124
    2
    May 3, 2013
    Hello

    With steppers, if you need all the steppers to do the same procedure you need to connect them all in parallel. This will allow all the motors to receive the same amount of current (as long as the length of wires between them are similar). In parallel all motors should follow the step sequence given by the driver. You need to ensure that the sum of all the phase currents of the motors are achievable by the driver. If you wire them in series the current will reduce proportionally from the first motor to the last depending on the phase resistance and Inductance of the motors. This means that the first motor will get much more torque than the last. (torque is proportional to the current).

    If the motors need to be controlled individually, things become much more complex. You will need individual controllers (or one master controller) to drive each individual motor. This is a large project and I would not recommend it for some one starting out as there is a lot to learn.

    Graham
     
  6. woodchips

    woodchips

    43
    0
    Feb 8, 2013
    Um, I am not convinced by simply connecting stepper motors in parallel.

    They are electromagnetic devices, and I can easily see how 11 motors could gang up on 1 motor and make it misstep due to different loading or similar. What you have in effect are 12 transformers with all sorts of circulating currents.

    I really don't see any solution but have as many stepper drivers as there are motors. If they are small motors, 1A or so, then this is just a single chip so no great cost or inconvenience.

    Bob
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    So you do actually want them all stepping in unison?

    Placing them in parallel would work as long as your driver provides a low impedance path to the source of power.

    However I wouldn't feel totally happy about it as a general solution.

    Are they all near each other? If not, separate drivers make even more sense.
     
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