A4988 with voltage regulators- low torque

Support Motor controllers/drivers and motors
1

Hello,

Absolute newb here. My setup: Arduino Uno R3, Arduino Ethernet Shield, Pololu A4988 with voltage regulators. 12V (.35 A/ phase) NEMA 17 Stepper. Here is the motor datasheet. [url]http://www.adafruit.com/datasheets/12vstepper.jpg[/url]

I am using a 12V adapter - [url]Pololu - Wall Power Adapter: 12VDC, 1A, 5.5×2.1mm Barrel Jack, Center-Positive.

My setup “works”, but I am getting super low torque. Barely enough to spin the motor with only a piece of e-tape attached to the shaft. I’m using AccelStepper library for testing. Here is my code:

#include <AccelStepper.h>

// Define a stepper and the pins it will use
AccelStepper stepper(1, 3, 2); // Defaults to AccelStepper::FULL4WIRE (4 pins) on 2, 3, 4, 5

void setup()
{  
    stepper.setMaxSpeed(200.0);
    stepper.setAcceleration(100.0);
}

void loop()
{    
    stepper.runToNewPosition(0);
    stepper.runToNewPosition(500);
    stepper.runToNewPosition(100);
    stepper.runToNewPosition(120);
}

Here are some pics of my setup.

grady_a4988_setup_1.jpg2592×1936 1.35 MB


grady_a4988_setup_2.jpg2592×1936 1.13 MB


grady_a4988_setup_3.jpg2592×1936 1.22 MB

I have many questions, but I’ll let you take a look at the setup first and see if anything seems wacky to you. I’m not exactly sure how to best go about adjusting the current trimmer pot, and the initial results I’m getting makes me suspect I have something really messed up in my setup.

Thanks in advance for any help.

2

I had my motor wired up incorrectly. The system works quite well now.

I have another question. Knowing these specs for my motor(s): 12V , .35 Amps per phase, 34 Ohms resistance per coil.

Can anyone help check my math to setting a good current for this setup (for all modes)? I am using a 12V, 1Amp power supply.

As a general test (which seems to work fine) I have set the limiter to a VREF of .16 V. This was my first test, in full step mode.

Current Limit = VREF × 2.5 -----> 0.4 A = .16 x 2.5

I’m pretty unsure of what the correlation is between my motor’s .35 Amps per phase rating and a good target for optimal performance. I’d love any help I could get in making an optimal current chart for this motor in each mode.

Thanks!

3

Hello.

You might take a look at the first FAQ on our stepper motor product pages. That FAQ explains more about the current limiting feature of the driver. I recommend setting the current limit of the A4988 carrier to 0.35A or slightly below for all step modes.

-Derrill