Homing with the AccelStepper library and a limit switch
In this video I show you an alternative way for homing using the AccelStepper() library. I use a TB6600 to drive a NEMA17 stepper motor and I use a microswitch/limit switch for the homing task. To have a full understanding of the AccelStepper() library and the TB6600 driver, please check my video on that topic.
Arduino source code
#include <AccelStepper.h> long receivedMMdistance = 0; //distance in mm from the computer long receivedDelay = 0; //delay between two steps, received from the computer long receivedAcceleration = 0; //acceleration value from computer char receivedCommand; //character for commands /* s = Start (CCW) // needs steps and speed values * o = open (CCW) // needs steps and speed values * c = close (CW) //needs steps and speed values * a = set acceleration // needs acceleration value * h = homing // goes back slowly to the origin. Origin should be determined manually as well as all the parameters! (speed, dir, acc...etc) * n = stop right now! // just the 'n' is needed */ bool newData, runallowed = false; // booleans for new data from serial, and runallowed flag const byte ledPin = 4; //led status pin, just to get a visual feedback from the button const byte interruptPin = 2; //pin for the microswitch using attachInterrupt(); // direction Digital 9 (CCW), pulses Digital 8 (CLK) AccelStepper stepper(1, 8, 9); void setup() { pinMode(interruptPin, INPUT_PULLUP); // internal pullup resistor (debouncing) attachInterrupt(digitalPinToInterrupt(interruptPin), stopMotor, FALLING); //If you choose FALLING, make sure that the switch connects the pin 2 to the GND when it is pressed. //You can change FALLING but make sure that you connect the switch to GND or +5V accordingly! //LED pins, OFF by default pinMode(ledPin, OUTPUT); digitalWrite(ledPin,LOW); Serial.begin(9600); //define baud rate Serial.println("Testing Accelstepper"); //print a message //setting up some default values for maximum speed and maximum acceleration stepper.setMaxSpeed(2000); //SPEED = Steps / second stepper.setAcceleration(1000); //ACCELERATION = Steps /(second)^2 stepper.disableOutputs(); //disable outputs, so the motor is not getting warm (no current) } void loop() { checkSerial(); //check serial port for new commands continuousRun2(); //method to handle the motor } void continuousRun2() //method for the motor { if (runallowed == true) { if (abs(stepper.currentPosition()) < receivedMMdistance) //abs() is needed because of the '<' { stepper.enableOutputs(); //enable pins stepper.run(); //step the motor (this will step the motor by 1 step at each loop) } else //program enters this part if the required distance is completed { runallowed = false; //disable running -> the program will not try to enter this if-else anymore stepper.disableOutputs(); // disable power Serial.print("POS: "); Serial.println(stepper.currentPosition()); // print pos -> this will show you the latest relative number of steps stepper.setCurrentPosition(0); //reset the position to zero Serial.print("POS: "); Serial.println(stepper.currentPosition()); // print pos -> this will show you the latest relative number of steps; we check here if it is zero for real } } else //program enters this part if the runallowed is FALSE, we do not do anything { return; } } void checkSerial() //method for receiving the commands { //switch-case would also work, and maybe more elegant if (Serial.available() > 0) //if something comes { receivedCommand = Serial.read(); // this will read the command character newData = true; //this creates a flag } if (newData == true) //if we received something (see above) { //START - MEASURE if (receivedCommand == 's') //this is the measure part { //example s 2000 500 - 2000 steps (5 revolution with 400 step/rev microstepping) and 500 steps/s speed runallowed = true; //allow running receivedMMdistance = Serial.parseFloat(); //value for the steps receivedDelay = Serial.parseFloat(); //value for the speed Serial.print(receivedMMdistance); //print the values for checking Serial.print(receivedDelay); Serial.println("Measure "); //print the action stepper.setMaxSpeed(receivedDelay); //set speed stepper.move(receivedMMdistance); //set distance } //START - OPEN if (receivedCommand == 'o') //OPENING { //example o 2000 500 - 2000 steps (5 revolution with 400 step/rev microstepping) and 500 steps/s speed runallowed = true; //allow running receivedMMdistance = Serial.parseFloat(); //value for the steps receivedDelay = Serial.parseFloat(); //value for the speed Serial.print(receivedMMdistance); //print the values for checking Serial.print(receivedDelay); Serial.println("OPEN "); //print the action stepper.setMaxSpeed(receivedDelay); //set speed stepper.move(receivedMMdistance); //set distance } //START - CLOSE if (receivedCommand == 'c') //CLOSING - Rotates the motor in the opposite direction as opening { //example c 2000 500 - 2000 steps (5 revolution with 400 step/rev microstepping) and 500 steps/s speed; will rotate in the other direction runallowed = true; //allow running receivedMMdistance = Serial.parseFloat(); //value for the steps receivedDelay = Serial.parseFloat(); //value for the speed Serial.print(receivedMMdistance); //print the values for checking Serial.print(receivedDelay); Serial.println("CLOSE "); //print action stepper.setMaxSpeed(receivedDelay); //set speed stepper.move(-1 * receivedMMdistance); ////set distance - negative value flips the direction } //STOP - STOP if (receivedCommand == 'n') //immediately stops the motor { runallowed = false; //disable running stepper.setCurrentPosition(0); // reset position Serial.println("STOP "); //print action stepper.stop(); //stop motor stepper.disableOutputs(); //disable power } //SET ACCELERATION if (receivedCommand == 'a') //Setting up a new acceleration value { runallowed = false; //we still keep running disabled, since we just update a variable receivedAcceleration = Serial.parseFloat(); //receive the acceleration from serial stepper.setAcceleration(receivedAcceleration); //update the value of the variable Serial.println("ACC Updated "); //confirm update by message } //HOMING if (receivedCommand == 'h') //homing, this movement will be interrupted via the attachInterrupt() triggered by the microswitch. { runallowed = true; //allow running Serial.println("HOMING"); //print action stepper.setAcceleration(100); //defining some low acceleration stepper.setMaxSpeed(100); //set speed, 100 for test purposes stepper.move(-1 * 20000); ////set distance - negative value flips the direction //distance should be larger than the length of the whole path. //I don't think that this is a safe way of homing. if the switch fails, the motor will keep running anyway } } //after we went through the above tasks, newData becomes false again, so we are ready to receive new commands again. newData = false; } void stopMotor()//function activated by the pressed microswitch { //Stop motor, disable outputs; here we should also reset the numbers if there are any runallowed = false; //disable running stepper.setCurrentPosition(0); // reset position Serial.println("STOP "); //print action stepper.stop(); //stop motor stepper.disableOutputs(); //disable power Serial.println("Pressed."); //feedback towards the serial port //This part might not work properly. digitalWrite(4,HIGH); //turn on LED delay(2000); //wait a bit digitalWrite(4,LOW); //turn off the LED }
