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I need to run 15 stepper motor simultaneously with different duty cycles for a mechanical study. However as a mechanical engineer my knowledge on the electronics is not much more than none. Could you please guide me how I should approach this problem?

Stepper motor:

According to my estimations stepper motors called 17HS4401 will work for me. The link below shows the datasheet for these motors. It has a rated voltage of 3.6 V and a rated current of 1.5A/phase

https://m.media-amazon.com/images/I/71ZPjYkgxwL.jpg

Motor Driver

I am planning to use one driver for each of the stepper motors as each of them will rotate in independent and variable speeds. The one I am planning to use is A4988. The datasheet is available in the link below. It says it has a maximum current of 2A.

https://www.pololu.com/file/0J450/a4988_DMOS_microstepping_driver_with_translator.pdf

Power Supply

I haven't decided on the power supply yet.

My questions:

  1. I am planning to feed the motor driver with a 12V supply. Will the motor driver be sufficient for the stepper motor I will use? (I don't know how much current the stepper motors can draw at max with this voltage, that's why I cannot make sure)

  2. Generally for this motor driver it is suggested to use an electrolytic capacitor between VMOT and GND. They say if it is not done spikes can be a problem. Does it mean that it will damage the driver or can it have other impacts? And does it have to be an an electrolytic one? The electrolytic ones I was able to find was SMD and I don't know how to fit them.

  3. I have found a CNC shield for Arduino Uno. But the shield has sockets for only 4 drivers. It seems that I will need to run 4 Aurdinos at the same time. Do I have any other option? If not is it possible to run 4 of them properly (as my laptop does not have 4 different USB ports I will need to use a splitter)?

  4. I am planning to use a 12V power supply. How much total current should I expect at max? I need to choose the current capacity of the power supply.

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  • \$\begingroup\$ Do you need to coordinate multi-dimensional movements between all of the motors as something like a multi-axis CNC machine would? If the movements are independent or only in small fixed groups, you could probably use several copies of "3d printer electronics" which are basically Arduino Megas outfitted with those or comparable stepper chips to run 4/5 motors each and minimal if any firmware modification. If you do need multi-dimension motion planning you may be in a real pickle requiring some careful realtime coding on a fast MCU, or a simple MCU controlling a tiny FPGA. \$\endgroup\$
    – Chris Stratton
    Commented Dec 3, 2020 at 16:22
  • \$\begingroup\$ Thanks for your comment. What I want to do is to generate a database. Each motor will have a long shaft and each will have plates on them. I will blow air through these plates and will record the pressure profile of the air behind the plates. For this purpose I need to run the motors in different speeds for many times (i.e. Case 1: M1=100 rpm, M2= 250 rpm, ..., M15= 50 rpm, Case 2: M1=150 rpm, M2=200 rpm, ... M15 = 100 rpm). \$\endgroup\$
    – Zalajbeg
    Commented Dec 3, 2020 at 17:42

1 Answer 1

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Well, it seems that you are looking for some general guidance, instead of presenting a real electronic engineering question. Most of folks here don't like this kind of question. But, anyways, I can say something about your doubts...

1 I am planning to feed the motor driver with a 12V supply. Will the motor driver be sufficient for the stepper motor I will use? (I don't know how much current the stepper motors can draw at max with this voltage, that's why I cannot make sure)

It's impossible to know for sure, since you didn't described your application. For most general uses, A4988 should be sufficient for this kind of stepper motor.

Steppers controlled by chopper drivers are somewhat weird: the applied voltage is not so much important as the current. For most general uses, 12 V are ok.

2 Generally for this motor driver it is suggested to use an electrolytic capacitor between VMOT and GND. They say if it is not done spikes can be a problem. Does it mean that it will damage the driver or can it have other impacts? And does it have to be an an electrolytic one? The electrolytic ones I was able to find was SMD and I don't know how to fit them.

Yes, spikes can damage the driver. Or something else can happen, and even if the driver is not damaged, the circuit may not work as desired. A4988 datasheet specifies 100 uF, so, follow what the datasheet says. Yes, it has to be an electrolityc capacitor. There are electrolictical SMD capacitors, aluminium-can type.

3 - I have found a CNC shield for Arduino Uno. But the shield has sockets for only 4 drivers. It seems that I will need to run 4 Arduinos at the same time. Do I have any other option? If not is it possible to run 4 of them properly (as my laptop does not have 4 different USB ports I will need to use a splitter)?

Simply don't use Arduino Uno, it is somewhat slow and has few outputs. There are a plethora of microcontrollers available that could fit your project better, whatever your project is (you didn't described it). 15 steppers in one circuit is not a trivial solution and probably you will not find a ready-made board to install those drivers... This is also a somewhat crytical design to fit in breadboards. Probably it would need a custom PCB.

4 I am planning to use a 12V power supply. How much total current should I expect at max? I need to choose the current capacity of the power supply.

As I said about question 1, it's impossible to know, since you didn't described your application. If the motor draws 1.5 A per phase, and each motor has two phases, there will be a theoretical maximum of 3A per motor, 45A total for 15 motors.

Maybe the total current drawing will be lower, but this it is not a reason to save a few bucks in a 30A or 40A supply. The price difference is insignificant (knowing that you will spend a lot in motors and drivers), so, go for a 50A or even a 60A or 70A 12V power supply.

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    \$\begingroup\$ Thanks a lot for your comments. You are right about the concept of the question. Unfortunately I don't know about the electronics good enough to present a real electronic engineering question. Your answer contributed a lot and I have marked it as the accepted answer. In general you can consider my projects as shafts rotated by the stepper motors and have plates on them. I want to observe the impact of different combinations. I will run maybe hundred of scenarios in which each motor will have an independent speed. \$\endgroup\$
    – Zalajbeg
    Commented Dec 3, 2020 at 17:46

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