Help with Easy Driver Example 1.7

Robotics
1

I am trying to use the Easy Driver with and Arduino Uno and a multiple Key LCD to control a syringe pump that someone else programmed based on other hardware. I used Example 1.6 to check the motor would move in two directions when different buttons were pressed and I got them to work. My motor has 200step/rev and a 360 degree revolution is 3200 microSteps of the stepper motor.

http://www.schmalzhaus.com/EasyDriver/E … mples.html

Now im trying to get the flowrates I need programmed by using the delay() for example I want the syringe to inject at 50 mL/min. My syringe is 300mL and has a barrel length of 155mm.

Since I don’t know how to code this I am following example 1.7 in the link above

I am trying to understand how to calculate the speed at which the stepper is moving the syringe. I realize the example is slightly different since it gives the RPM and what I am try to calculate is the RPM required for the flowrate but maybe if I can understand how the delay is calculated I can work backwards

I don’t understand how they got these two lines( not in correct order )

delayMicroseconds((MICROSECONDS_PER_MICROSTEP * 0.9)/2);

#define MICROSECONDS_PER_MICROSTEP (1000000/(STEPS_PER_REV * MICROSTEPS_PER_STEP)/(RPMS / 60))

thank you

Example1.7 code:

/* This example assumes a step/direction driver with Step on pin 9, Direction on pin 8
 * And an input switch on pin 3. The switch is a switch to ground, with pin 3 pulled
 * high with a pullup resistor. When the switch is turned on (closed, i.e. goes low)
 * the the sepper motor steps at the rate specified (104 RPM in this code, with
 * 1/8th microstepping of a 200 steps/rev motor)
 */
 
#define RPMS                104.0
#define STEP_PIN                9
#define DIRECTION_PIN           8
#define GO_PIN                  3

#define STEPS_PER_REV         200
#define MICROSTEPS_PER_STEP     8
#define MICROSECONDS_PER_MICROSTEP   (1000000/(STEPS_PER_REV * MICROSTEPS_PER_STEP)/(RPMS / 60))

uint32_t LastStepTime = 0;
uint32_t CurrentTime = 0;

void setup() {                
  pinMode(STEP_PIN, OUTPUT);     
  pinMode(DIRECTION_PIN, OUTPUT);
  digitalWrite(STEP_PIN, LOW);
  digitalWrite(DIRECTION_PIN, LOW);
  pinMode(GO_PIN,INPUT);
}

void loop() {
  if (digitalRead(GO_PIN) == LOW)
  {
    CurrentTime = micros();
    if ((CurrentTime - LastStepTime) > MICROSECONDS_PER_MICROSTEP)
    {
      LastStepTime = CurrentTime;
      digitalWrite(STEP_PIN, HIGH);
      delayMicroseconds((MICROSECONDS_PER_MICROSTEP * 0.9)/2);
      digitalWrite(STEP_PIN, LOW); 
      delayMicroseconds((MICROSECONDS_PER_MICROSTEP * 0.9)/2);
    }
  }
}
2

The following are good resources to read into for more information on the subject:

https://learn.sparkfun.com/tutorials/mo … ly-precise

https://youtu.be/bkqoKWP4Oy4?t=127