NEMA 17 + UNO + A4988 + Button: motor moves randomly in small steps, could it be noise?

Other Hardware Motors, Mechanics, Power and CNC
1

Hi all,
I have a system where I am controlling two NEMA 17 motors using an Arduino UNO. One motor controls a linear actuator via an UP button and a DOWN button. The other rotates constantly in the same direction when a switch is on. Here's the code:

#include <AccelStepper.h>

// Defines analog-in pin for UP button
#define BUTTON_A_PIN 8
// Defines analog-in pin for DOWN button
#define BUTTON_B_PIN 9

// Defines analog-in pin for spindle ON/OFF switch
#define switchPin 10

// Defines microstep pins for A4988 stepper motor driver
#define MS1_PIN 7
#define MS2_PIN 6
#define MS3_PIN 5

// Defines Linear Actuator stepper 
AccelStepper upDownStepper(1,1,2);
// Defines Spindle rotation stepper
AccelStepper spindleStepper(1,3,4);

// Variable to track switch state
int prevSwitchState = HIGH;
 
// Variables to track button states
int prevButtonAState = HIGH;
int prevButtonBState = HIGH;

void setup() {
  pinMode(MS1_PIN, OUTPUT);
  pinMode(MS2_PIN, OUTPUT);
  pinMode(MS3_PIN, OUTPUT);

  // Set microstepping resolution to 1/16 step (MS1=HIGH, MS2=HIGH, MS3=HIGH)
  digitalWrite(MS1_PIN, HIGH);
  digitalWrite(MS2_PIN, HIGH);
  digitalWrite(MS3_PIN, HIGH);

  // Set maximum speed and acceleration values for the stepper
  spindleStepper.setMaxSpeed(1000);
  spindleStepper.setAcceleration(500);

  // Set the initial position of the stepper motor
  spindleStepper.setCurrentPosition(0);

   // Set up the button pin
  pinMode(switchPin, INPUT_PULLUP); // Set the button pin as input with internal pull-up resistor

  // Set up the stepper motor
  upDownStepper.setMaxSpeed(1000); // Set the maximum speed of the stepper motor in steps per second
  upDownStepper.setAcceleration(1000); // Set the acceleration of the stepper motor in steps per second squared
}
void loop() {
  
// UP/DOWN ******************************************************************************

// Read the state of button A
  int buttonAState = digitalRead(BUTTON_A_PIN);

  if(buttonAState == LOW) {
    upDownStepper.setSpeed(100);
  // Step the motor with a constant speed previously set by setSpeed();
  upDownStepper.runSpeed();
  }
  else {
  upDownStepper.stop();
  upDownStepper.setCurrentPosition(0);
  }

  // Read the state of button B
  int buttonBState = digitalRead(BUTTON_B_PIN);

  if(buttonBState == LOW) {
    upDownStepper.setSpeed(-100);
  // Step the motor with a constant speed previously set by setSpeed();
  upDownStepper.runSpeed();
  }
  else {
  upDownStepper.stop();
  upDownStepper.setCurrentPosition(0);
  }

  //SPINDLE ROTATION ******************************************************************************

  // Read the state of the button
  int switchState = digitalRead(switchPin);

  // Check if the button is pressed and the previous state was not pressed
  if (switchState == LOW) {

  spindleStepper.setSpeed(500);
  // Step the motor with a constant speed previously set by setSpeed();
  spindleStepper.runSpeed();
  }
  else {
  spindleStepper.stop();
  spindleStepper.setCurrentPosition(0);
  }
}

The UP/DOWN motor rotates randomly in several small steps in one direction the several in the other. Completely random. I think it may be a noisy connection with the driver board. Or it may be that my code is buggy. Any help is appreciated.

Cheers,

2

Post an annotated schematic showing exactly how it is wired. Note any leads over 10"/25cm. Be sure to show all power sources.

3

Are PinA and PinB floating when not grounded with a button press?
I don't see an INPUT_PULLUP pin mode setting and the default is INPUT.
Do you have external pull up resistors?

4

Pin 1 is, normally, the hardware serial transmit pin, Even though you have not started the serial port, i wonder if the USB to serial chip might not be doing some weird stuff causing the random motion. Maybe try another pin?

5

I added an INPUT_PULLUP for BUTTON_A_PIN and BUTTON_B_PIN, this solved the issue. Thank you very much!

6

Thanks for your suggestion, I switched from a breadboard to a CNC shield so the stepper is now upDownStepper(1,4,7);

7

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