Skip to content

(Some) Progress on the 3D printer

One of my work colleagues has an Arduino kit, that includes amongst other things a stepper motor driver, an ULN2003APG board,  and I convinced him to lend it to me.

ULN2003APG_front ULN2003APG_back

This weekend I had some time, so I played a bit with it. After reading it’s data sheet, and comparing some examples I found online with other motors; finding those motors data sheets and comparing their coils connections with my motor, I got to this schematic:


And with the tutorial code for stepper motors I got it working. I’ve initially done a revolution test, to make sure I got the number of steps, wiring and direction right. Also I’ve connected 2 multimeters to make sure I have a safe voltage and current. I’ve tested this with several speeds, using the LEDs on the driver board to check the steps order.

Once this was a success, I’ve moved on to connecting this driver to the prototype pillar I’ve made for the 3D printer. I ran the same code with 3 motor revolutions, to have it move the carriage on a longer distance.

After this I’ve noticed a few problems:

  • The motor is juddering
  • How do I control how much to go up or down?
  • The driver board was making it difficult for me to follow the wiring, so I removed the IC and placed it in the breadboard.

I went ahead to solve the second problem first.

I’ve hot glued 2 door switches at the top and bottom of the pillar, so the carriage pushes them when it gets to the top or the bottom. This would trigger a change of direction. I’ve done some tests with a couple of LEDs, to check if this would work. I’ve also added the option to stop the motor (both LEDs on) if both switches are pressed.

Of course I didn’t have the right value resistors (10k) so I used 2 *4 ,7k resistors for each button. Remember I’m building this from what ever scraps I find or can get my hand onto. Eventually, after some tests I got to this schematic:

test_motor_4_ULN2003APG_schemăI forgot to remove the LEDs after the test, so I left them there. No harm in that.

From the first run it was a success. I was thrilled.

Here’s the code I used:

const int stepsPerRevolution = 200;
Stepper myStepper(stepsPerRevolution, 9,10,11,12);

const int led_up   = 7;
const int led_down = 6;

const int btn_up   = 3;
const int btn_down = 2;

int btn_up_state   = 0;
int btn_down_state = 0;

enum State {

State currentState;

void stopMotor()
  digitalWrite(led_up,   HIGH);
  digitalWrite(led_down, HIGH);
  currentState = STOPPED;

void goUp()
  digitalWrite(led_up,   HIGH);
  digitalWrite(led_down, LOW);
  currentState = GOING_UP;

void goDown()
  digitalWrite(led_up,   LOW);
  digitalWrite(led_down, HIGH);
  currentState = GOING_DOWN;

void moveMotor()
    case STOPPED:
    case GOING_UP:
    case GOING_DOWN:

void setup() {
  pinMode(led_up,   OUTPUT);
  pinMode(led_down, OUTPUT);
  pinMode(btn_up,   INPUT);
  pinMode(btn_down, INPUT);

void loop() {
  btn_up_state   = digitalRead(btn_up);
  btn_down_state = digitalRead(btn_down);
  if (btn_up_state == HIGH && btn_down_state == HIGH)
  { // STOP the motor
  else {
    if (btn_up_state == HIGH)
    { // Go down
    if (btn_down_state == HIGH)
    { // Go up

Now onto solving the juddering problem.

Since the motor also seems to judger even if it’s not geared to anything, there must be a problem with either how I’m using the Stepper library, or with the library itself. It might be a problem just with this specific motor. I don’t know. I’ve started reading the inner parts of the library, and do some more research.

‘till next time!

Published inHardwareProjectsSoftware

One Comment

  1. Alin Alin

    Ține sus munca bună!

Lasă un răspuns

Acest sit folosește Akismet pentru a reduce spamul. Află cum sunt procesate datele comentariilor tale.