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A4988 Driver and Its Onboard Potentiometer


#1

I am able to start my project anytime now and am getting a little concerned that I may not have fully understood the roles each segment of the hardware plays in producing the motion that I am looking for.

A powered Arduino Micro deliver pulses in time to the A4988 driver that is powered by a clean 5v coming out of the Arduino. The driver is also powered by an external power source of a voltage in the range of 8 to 35 volts in order to drive the 10v, 0.5A/Phase stepper motor.

The driver has a potentiometer onboard that can control/limit the output current to the stepper in order to allow me to exceed the stepper’s rated voltage so that I can drive it faster (at a higher step rate).

The pulse modulation signals of the controller are controlled by the user and through the programming of the controller.

If I program the controller for 1 step per minute, and if I don’t care about micro-stepping and thereby leaving the MS1, Ms2, and MS3 LOW 9disconnected), and if I don’t mess around with that Potentiometer, and if I deliver motor power in the specified range and through the driver, will I get the motor to turn at the speed that I want, 1 step per minute, 1.8 degrees per minute?

Can someone please help me understand what this means exactly: “Adjustable current control lets you set the maximum current output with a potentiometer, which lets you use voltages above your stepper motor’s rated voltage to achieve higher step rates” and since this is advertized as a useful feature of the driver, how can I be sure what speeds are produced if I use it?

I have a 12v, 3A external power supply which is in the range specified for the driver and am trying to accurately run a 10v, 0.5A/phase motor.

Would anyone recommend a more simpler driver for a beginner?

Thanks in advance,

Farzad


#2

I am not sure what you are asking, but it sounds like you might not understand that the speed the stepper motor steps at is determined by the speed of the pulses that you apply to the STEP pin on the driver. I do not know of a stepper motor driver that is easier to use, but this thread has a guide on getting started with the A4988 that might help you out.

-Claire


#3

Hi,

So I am wondering after soldering the headers onto the A4988 (driver) what do you recommend as a test process to ensure the board hasn’t gotten fried by me? Is there a check of soundness of the board? I wonder if a pre-soldered version might be available. Always order two, I say!

Thanks.

Farzad


#4

Hello, Farzad.

I have moved your post to this thread because it seems like your questions are still about getting started with using your A4988 stepper motor driver carrier. You might just try getting started with the basic connections shown in the minimal wiring diagram on the product page and following the guide in the link provided by Claire. If you are not sure that your soldering joints are making good connections, you could post a picture, and I would be happy to take a look.

By the way, we do not sell the stepper motor driver carrier pre-soldered, but some of our distributors do. For example, UltiMachine sells them pre-soldered for an additional fee.

- Grant


#5

[quote=“Claire”]I am not sure what you are asking, but it sounds like you might not understand that the speed the stepper motor steps at is determined by the speed of the pulses that you apply to the STEP pin on the driver. I do not know of a stepper motor driver that is easier to use, but this thread has a guide on getting started with the A4988 that might help you out.

-Claire[/quote]

Clair,

I thought my question was clear. I was hoping someone would tell me the meaning of the statement I had quoted about how the driver can help achieve higher steps rates (speeds?) out of motor, and I had also shared my understanding that the controller determined the step and step speed while the driver communicated that speed to the motor. Then what is this about being able to drive the motor faster with a higher voltage and limiting Amp?

I do appreciate your directing me to another conversation. I was hoping to get help here instead of gong out searching within other conversations. I am reading, and honestly, it is more confusing.

I am not sure what the purpose of the potentiometer is on the driver if the speed is to be controlled by the controller.


#6

The speed of the stepper motor is controlled by the microcontroller in your system. However, a stepper motor can only step so fast. By increasing the voltage applied to a stepper motor you allow the current through the coils of the motor to increase faster, which can help the motor reach higher maximum step rates.

The potentiometer on our stepper motor drivers is used to set their current limit. It does not control the speed of the stepper motor, though in general the more current the stepper motor is allowed to draw the faster the maximum step rate for the motor will be. The higher the voltage you apply to a stepper motor, the higher the current it will try to draw. The rated voltage of a stepper motor is just the voltage at which the motor draws its rated current. When using a voltage higher than the rated voltage of your stepper motor, it is important to set the current limit at or below the rated current of the motor to prevent damaging it by drawing too much current.

-Claire


#7

Thanks, Claire. That makes it very clear.

Farzad