OVERVIEW
Welcome to this multi part tutorial on how to control different stepper motors using a rotary encoder.
In this first part we will use the inexpensive and popular stepper motor that comes with it’s own control board. The 28BYJ-48 stepper motor with the ULN2003 board.
The 28BYJ-48 motor is not very fast or very strong, but it’s great for beginners to start experimenting with controlling a stepper motor with an Arduino.
We will write some code to have the motor move in the direction that we turn the rotary encoder, and will also keep track of how much steps we have taken, so that we can have the motor move back to the starting position by pressing down on the rotary encoder switch.
In the next tutorial we will use a Nema 17 stepper motor and the EasyDriver board.
PARTS USED
Breadboard Power Supply
Rotary Encoder Module
Stepper Motor
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CONNECTIONS
We are using 4 pins to control the Stepper and 3 pins for the rotary encoder module.
Pin 8-11 are controlling the Stepper motor and pin 2-4 are receiving information from the rotary encoder.
We connect the 5V and Ground from to UNO to the rotary encoder and as a precaution, use a breadboard power supply to power the Stepper motor since it can use more power that the UNO can provide.
We also connect the UNO Ground to the breadboard to serve as a reference.
THE CODE
We are using the “Stepper” library to control the stepper motor.
The “Stepper” library is included by default with the Arduino Software install.
We are using some variables to store the current position, since we want to keep track of the position of the stepper motor so we can make it move back to the starting position.
We also included some error checking code to make sure that the rotary encoder is not missing steps, since that would make our motor position inaccurate.
As always, please check out the tutorial video to have more information.
#include "Stepper.h"
#define STEPS 32 // Number of steps for one revolution of Internal shaft
// 2048 steps for one revolution of External shaft
volatile boolean TurnDetected; // need volatile for Interrupts
volatile boolean rotationdirection; // CW or CCW rotation
const int PinCLK=2; // Generating interrupts using CLK signal
const int PinDT=3; // Reading DT signal
const int PinSW=4; // Reading Push Button switch
int RotaryPosition=0; // To store Stepper Motor Position
int PrevPosition; // Previous Rotary position Value to check accuracy
int StepsToTake; // How much to move Stepper
// Setup of proper sequencing for Motor Driver Pins
// In1, In2, In3, In4 in the sequence 1-3-2-4
Stepper small_stepper(STEPS, 8, 10, 9, 11);
// Interrupt routine runs if CLK goes from HIGH to LOW
void isr () {
delay(4); // delay for Debouncing
if (digitalRead(PinCLK))
rotationdirection= digitalRead(PinDT);
else
rotationdirection= !digitalRead(PinDT);
TurnDetected = true;
}
void setup () {
pinMode(PinCLK,INPUT);
pinMode(PinDT,INPUT);
pinMode(PinSW,INPUT);
digitalWrite(PinSW, HIGH); // Pull-Up resistor for switch
attachInterrupt (0,isr,FALLING); // interrupt 0 always connected to pin 2 on Arduino UNO
}
void loop () {
small_stepper.setSpeed(600); //Max seems to be 700
if (!(digitalRead(PinSW))) { // check if button is pressed
if (RotaryPosition == 0) { // check if button was already pressed
} else {
small_stepper.step(-(RotaryPosition*50));
RotaryPosition=0; // Reset position to ZERO
}
}
// Runs if rotation was detected
if (TurnDetected) {
PrevPosition = RotaryPosition; // Save previous position in variable
if (rotationdirection) {
RotaryPosition=RotaryPosition-1;} // decrase Position by 1
else {
RotaryPosition=RotaryPosition+1;} // increase Position by 1
TurnDetected = false; // do NOT repeat IF loop until new rotation detected
// Which direction to move Stepper motor
if ((PrevPosition + 1) == RotaryPosition) { // Move motor CW
StepsToTake=50;
small_stepper.step(StepsToTake);
}
if ((RotaryPosition + 1) == PrevPosition) { // Move motor CCW
StepsToTake=-50;
small_stepper.step(StepsToTake);
}
}
}TUTORIAL VIDEO
DOWNLOAD
Copy the above Sketch code in your Arduino IDE software to program your Arduino.
We are using the “Stepper” library which is included by default with the Arduino IDE Software install.