Limit Switches for stepper motor

Using Arduino Programming Questions
1

Hello,

I am currently using two limit switches (https://www.amazon.com/Lysee-Printer-Parts-Accessories-Mechanical/dp/B092TLSZC1/ref=sr_1_5?dchild=1&qid=1626198847&refinements=p_n_feature_two_browse-bin%3A9648512011&s=industrial&sr=1-5) to limit the motion of a stepper motor along a linear driver. I am using a cnc and arduino uno with the limit switches connect to x+ and x- of the end stop pins

#include <AccelStepper.h>

//Pins
const byte limitSwitch1 = 9;
const byte analogX_pin = A1;

AccelStepper stepperX(1,2,5);


//variables
int analogX = 0;  //x-axis valueint 
int analogX_AVG = 0; //x-axis average value (middle)

void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(analogX_pin,INPUT);
pinMode(limitSwitch1,INPUT);

InitialValues(); //calculating the middle/average value for three analog pins 

//stepper parameters 
stepperX.setMaxSpeed(5000);
stepperX.setAcceleration(1000);
stepperX.setSpeed(500);
delay(500);
}


void loop() {

readAnalog();
stepperX.runSpeed();

}

void readAnalog() {
//reading from joystick position

analogX = analogRead(analogX_pin);

//if value is at least 25 away from the average value with allow the update of speed and moving to pointed direction
if(abs(analogX - analogX_AVG)>25) {
//if limit switch is  clicked, do not run the motor 
 if (digitalRead(limitSwitch1) == LOW) {
    stepperX.setSpeed(0);
    Serial.println("switch is clicked");
 } else {
  stepperX.setSpeed(5*(analogX - analogX_AVG)); 
  Serial.println("switch is not clicked");
}
}
else { //the analog value is less than 25 so do not run the motor yet 
  stepperX.setSpeed(0);
}
}
  
void InitialValues() {

  float tempX = 0; //set temporary x value to 0 

  //read the analog value initial 50 times and get the average to have accurate middle value 
  for (int i=0;i<50;i++) {
    tempX += analogRead(analogX_pin); 
  }
  analogX_AVG = tempX/50;   
}

Everything seems wired correctly and by printing simple messages (switch is clicked/switch is not clicked), it seems that the code is working. When I am using the joystick and clicking the switch the correct message is printed. Nevertheless, the motor actually doesn't rotate and move. It makes a weird sounds but holds still. Would you know possible reasons for this?

I have tried controlling the motor just with joystick and no limit switch and works perfectly so the issue arises when I add the limit switches!

Thanks!

2

One possible reason is that you are sending steps too fast for the motor. The runSpeed() function does not use acceleration so the maximum speed that you can start the motor with is limited. I would print the value of setSpeed() each time that it is calculated.

What is connected to the analogX_pin?

3

You have

pinMode(limitSwitch1,INPUT);

How is your limit switch wired? I'm wondering if the input is bouncing and causing that behavior.

4

The analogX_pin is the connection between A1 from the arduino and the VRX pin of the joystick.

5

So I have one limit switch going to x+ end stop of cnc shield v3 and the second limit switch going to x- end stop of cnc shield. Signal from the limit switch is connected to white pins of cnc shield and ground to black, the power is not connected. I read that both x+ and x- of cnc shield connect to pin 9 of arduino, so I am just initialising one limitSwitch variable, maybe this is the mistake?

6

You have the limit switch wired right. Pin 9 is for both X+ and X-. But you need a pullup resistor on the switch pin. That can be an external pullup (10K) or, better, enable the internal pullup with pinMode(pin, INPUT_PULLUP);.

7

What groundFungus said. Try that first.

Also, is your limit switch wiring shielded? That could cause false triggers. I had that issue on my CNC machine.

8

I do not see in your code where you enable the steppers. The CNC shield V3 disables the steppers by default, at least the ones that I have do. Pin 8 is the enable pin. Make pin 8 an output and set it to low (in setup()).

9

With the input pullup the code works fine and limit switch do what expected.Thanks

10

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