Continuously Extend & Retract An Actuator Stroke With A Brushless DC Motor

1. Arduino Mega (Arduino Uno can be used as well).
2. LC-241.
3. PA-14 with brushless motor.
4. PS-13-12 power supply.

Linear actuator has 2 sets of wires coming out of it, one set is for the motor and the other set is for the limit switches. The schematic in the figure above shows how to wire the components together.

PIN SETUP CODE

int out_lim = 45; // outer limit switch pin

int in_lim = 53;  // inner limit switch pin

int run_f = 25;  // run pin on controller
int run_r = 30;  // reverse pin on controller

This part of code takes care of initialization of pins that will be used for receiving and sending data. All digital pins were used in this case, but analog ones can be used as well.

SETUP LOOP CODE

void setup() {

  Serial.begin(9600);  // initialize serial communication at 9600 bits per second
  pinMode(out_lim, INPUT_PULLUP); // configures pin 45 as input pin
  pinMode(in_lim, INPUT_PULLUP); // configures pin 53 as input pin
  pinMode(run_f, OUTPUT); // configures pin 25 as output pin
  pinMode(run_r, OUTPUT); // configures pin 30 as output pin

  retract(); // retracts the stroke on startup

  delay(500);
  }

The “setup” loop configures which pins will be used for output and which will be used for input. As it can be seen in the code, pins connected to limits witches will be used to read limit switch states and pins connected to “RUN” and “REV” on LC-241 will be used to write to it. Initially, the code also runs a retraction function to retract all the way in before starting.

FUNCTION DEFINITIONS CODE

void extend() // this function enables the motor to run

{
 digitalWrite(run_f, LOW);
 digitalWrite(run_r, HIGH);

 }

void retract() // this function reverses the direction of motor
{
  digitalWrite(run_f, LOW);
  digitalWrite(run_r, LOW);
}

void run_stop() // this function disables the motor
{
  digitalWrite(run_f, HIGH);
  digitalWrite(run_r, HIGH);
}

This part explains the functions used to control the motor power and direction. We will be enabling or disabling the motor by writing “0” or “1” to “RUN” pin and then the same commands to “REV” pin to reverse the direction of the motor.

MAIN LOOP CODE

Void loop() {

   int out_lim_state = digitalRead(out_lim);     // reads the limit switches and saves its value
  int in_lim_state = digitalRead(in_lim);

   Serial.print("outer limit switch value "), Serial.println(out_lim_state); // 0 -> limit switch is pressed
   Serial.print("inner limit switch value "), Serial.println(in_lim_state);  // 1 -> limit switch is not pressed

  if (out_lim_state == 0 && in_lim_state == 1) // if outer limit switch is pressed and inner is not (extended all the way)
   {
   retract(); // retract the stroke
   }

   else if (out_lim_state == 1 && in_lim_state == 0) // if inner limit switch is pressed   and outer is not (reracted all the way)
  {
   extend(); // extend the stroke
  }

The “loop” loop basically just reads the inputs from limit switches to check if the switches are pressed or not and then based on that it just changes the direction of the motor.

Most of the linear actuators in the market come installed with a brushed DC motor and so the duty cycle available with that motor makes it somewhat impossible to continuously run the unit. At Progressive Automations, we give our customers the freedom to opt for a brushless DC motor for our PA-14 model giving them even more options for their projects.