Calculation always returns 0 serial print

Using Arduino Programming Questions
#1

Dear Arduinoers,

I have a potentiometer 10kOhm which I want to use to control a stepper motors (Nema 17 1.8 deg bipolar) RPM. I am using a TB6600 stepper driver. Serial print reads 0 - 1023 from the potentiometer as expected.

When I try to calculate the RPM however the calculation returns 0.

int Pot = A1; // Input pin for the potentiometer.
int RPM; // Declares variable for RPM

void loop(){
Pot = analogRead(A1);
RPM =(Pot/1023)*100

This probably has to do with integer. I don’t want to make it floating though since I use it later on in a formulea to calculate the corresponding delay for the steppermotor to get the required RPM.

  //Enables the motor direction to move in a certain direction.
  digitalWrite(dirPin,LOW);
  //Makes 200 Pulses for making one full cycle (1.8 degree stepper).
  for(int x = 0; x < 200; x++){
    digitalWrite(stepPin,HIGH); 
    delayMicroseconds(10^6/((RPM/60)*200*2));
    digitalWrite(stepPin,LOW); 
    delayMicroseconds(10^6/((RPM/60)*200*2));

Any advice on how to fix this problem?!

#2

Driez:

RPM = int(Pot/1023)*100

How much is Pot/1023 converted to an integer? What changes if you first multiply before dividing first cast to a long, then multiply, and then divide?

Also change int Pot = A1 to const int Pot = A1 and you'll discover another bug.

And "10^6" doesn't mean what you think it means. Bitwise operators

Pieter

#3

PieterP:
What changes if you first multiply before dividing?

You stand a good chance of discovering more weird stuff?

#4

PieterP:
How much is Pot/1023 converted to an integer? What changes if you first multiply before dividing first cast to a long, then multiply, and then divide?

Also change int Pot = A1 to const int Pot = A1 and you'll discover another bug.

And "10^6" doesn't mean what you think it means. Bitwise operators

Pieter

Dear Pieter, I have worked around the int problem by changing the RPM calculation into the following formula which also caps my RPM at around 100 RPM.

RPM =(Pot/10);

The Pot/1023 value will always be less then 1 so the integer makes it 0 that's why I knew it was an integer problem.

Why would I change the Pot to a const int?

Thank you, I changed 10^6 to 1000000

#5

Try RPM =(Pot * 100) / 1023;

#6

Try

RPM = (Pot * 100L) / 1023;

As AWOL alluded to, log2(102,300+1) > 15.

#7

PieterP:
Try

RPM = (Pot * 100L) / 1023;

As AWOL alluded to, log2(102,300+1) > 15.

Oh! Forgot about that important little detail.

#8

Cheers guys thanks a lot! I am almost there. Keep in mind it’s my first time programming anything so I really do appreciate all the help! I’ve been looking for this for more than 2 hours on google and forums.

Right now I have a setable RPM value with my potentiometer. I can continue to use this RPM to calculate the required corresponding delayMicroseconds. However I suspect there might be an easier way to do this?

Furthermore do I need to use an acceleration code or are the RPM’s low enough that this isn’t necessary (max 100RPM)?

This is my current code to drive the 17HS24-2104S nema 17 motor using the TB6600 stepper driver at 2A and 200 pulses per revolution.

I take the potentiometers input RPM and divide by 60 to convert it to RPS. Then I multiply this number by 10^6 (1000000) to convert seconds to microseconds. I divide by 200 to get the delay in microseconds per pulse and divide this by 2 to get the delay in microseconds per phase.

void loop(){
  Pot = analogRead(A1);
  //Serial.print(Pot);
  RPM =(Pot*100L)/1023;
  Serial.print(RPM);
  lcd.setCursor(0,0); //Defining position to write from first row, first column.
  lcd.print ("RPM"); // Showing the letters RPM
  lcd.setCursor(0,1); //Defining position to write from second row, first column.
  lcd.print (RPM); // Showing current RPM value
  
  //Enables the motor direction to move in a certain direction.
  digitalWrite(dirPin,LOW);
  //Makes 200 Pulses for making one full cycle (1.8 degree stepper).
  for(int x = 0; x < 200; x++){
    digitalWrite(stepPin,HIGH); 
    delayMicroseconds=((((RPM*1000000)/60)/200)/2);
    //delayMicroseconds(500);
    digitalWrite(stepPin,LOW); 
    delayMicroseconds=((((RPM*1000000)/60)/200)/2);
    //delayMicroseconds(500);
#9

Driez:
Cheers guys thanks a lot! I am almost there. Keep in mind it’s my first time programming anything so I really do appreciate all the help! I’ve been looking for this for more than 2 hours on google and forums.

Right now I have a setable RPM value with my potentiometer. I can continue to use this RPM to calculate the required corresponding delayMicroseconds. However I suspect there might be an easier way to do this?

Furthermore do I need to use an acceleration code or are the RPM’s low enough that this isn’t necessary (max 100RPM)?

This is my current code to drive the 17HS24-2104S nema 17 motor using the TB6600 stepper driver at 2A and 200 pulses per revolution.

I take the potentiometers input RPM and divide by 60 to convert it to RPS. Then I multiply this number by 10^6 (1000000) to convert seconds to microseconds. I divide by 200 to get the delay in microseconds per pulse and divide this by 2 to get the delay in microseconds per phase.

void loop(){

Pot = analogRead(A1);
  //Serial.print(Pot);
  RPM =(Pot100L)/1023;
  Serial.print(RPM);
  lcd.setCursor(0,0); //Defining position to write from first row, first column.
  lcd.print (“RPM”); // Showing the letters RPM
  lcd.setCursor(0,1); //Defining position to write from second row, first column.
  lcd.print (RPM); // Showing current RPM value
 
  //Enables the motor direction to move in a certain direction.
  digitalWrite(dirPin,LOW);
  //Makes 200 Pulses for making one full cycle (1.8 degree stepper).
  for(int x = 0; x < 200; x++){
    digitalWrite(stepPin,HIGH);
    delayMicroseconds=((((RPM1000000)/60)/200)/2);
    //delayMicroseconds(500);
    digitalWrite(stepPin,LOW);
    delayMicroseconds=((((RPM*1000000)/60)/200)/2);
    //delayMicroseconds(500);

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#10

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#11