# Stepper driver RPM control

Hey guys,

So, I am currently working on a project that requires accurate RPM control.

I have JK86HS115-6004 stepper motor and JKD2060AC stepper driver. I set the driver to 800 pulses/revolution and I power it from a 60V / 6A DC power supply. It is going to be a part of a cnc I am building. The ball screws have 5mm lead which I take into account.

Here is the problem. Since it is a future cnc, I work with mm/min feed values. I set the feed to 5mm/min. Since the lead is 5mm, it should take the motor 1 minute to make 1 revolution. But that is not the case. It takes 25 seconds or less but it makes exactly one revolution. I calculate the needed values in the code (see below) such as frequency, RPM, period etc. What seems to be the problem is the period (pd), no matter what I do with it (I tried dividing, multiplying, setting the value manually) the revolution is always too quick. I read somewhere here that 10us delay is enough for the driver to send the pulse and for the motor to move. So I changed the code accordingly, but no dice.

What am I not seeing?

``````#define DIR 3
#define PUL 4
#define ENA 5

float freq;               //frequency
float p_rev = 800.0;      //pulses(steps) per revolution
float rpm;                //RPM
float s = 5.0;            //lead of the ball screw
float mm_min = 5.0;       //feed
float dist_mm = 5.0;      //the distance the nut should travel
float mm_step;            //the distance the nut travels with one step
int pd;                   //delay period
int stp;                  //number of steps the motor has to make

void setup() {

pinMode(DIR, OUTPUT);
pinMode(PUL, OUTPUT);
pinMode(ENA, OUTPUT);

}

void loop() {

rpm = mm_min/s;
freq = (p_rev * rpm)/60.0;
pd = ((1/freq) * 1000000.0)-10;
mm_step = s/p_rev;
stp = dist_mm/mm_step;

for(int i = 0; i <= stp; i++){

digitalWrite(PUL,HIGH);
delayMicroseconds(10);
digitalWrite(PUL,LOW);
delayMicroseconds(pd);
}

delay(2000);

}
``````

Read this: https://www.arduino.cc/reference/en/language/functions/time/delaymicroseconds/. 75 000 pulses can't be handled by an unsigned int.

Railroader: Read this: https://www.arduino.cc/reference/en/language/functions/time/delaymicroseconds/. 75 000 pulses can't be handled by an unsigned int.

That makes sense. Thank you very much.

Accurazy can’t be that important så You can scale down by a factor 1000 and use dely (milliseconds).

Maximum delayMicroseconds is 16383. https://www.arduino.cc/reference/en/language/functions/time/delaymicroseconds/

Correct according to Arduino reference, max 16383, 14 bits. An int can reach 32767 and un unsigned int 65535.