PWM with arduino and L298N

[jasontit]

Hey

I'm trying to control 2 DC motors by using Arduino and L298N and something strange happens.
I'm writing same PWM values in the Arduino PWM pins (3 and 6), but the voltages that I see in the output pins (which is the pins that connect to the motors) of L298N are different (the motors moving in different speed).

I am not understand why. Same PWM voltage from the Arduino leads to different output of the L298N.

Best regards.

// Two Motors DC With L298 

#include <Servo.h>


//FLAME SENSORS
#define Left 8      // left sensor
#define Right 9    // right sensor
#define Forward 7  //front sensor ###

//MOTORS
#define LM 11      // left motor - FRONT 
#define LM_CONST 10
#define RM 13      // right motor - FRONT 
#define RM_CONST 12
#define EN_RM 3      // right motor - FRONT 
#define EN_LM 6       // left motor - REAR

//WATER PUMP
#define pump 4  // ###

//Servo
#define servoPin 5

Servo myservo;

int motor_speed = 60;  // PWM
int pos = 0; // ANGLE

//General
int i;
char state = 0; //Variable for storing received data  
boolean fire = false;

void setup() {
  pinMode(Left, INPUT);
  pinMode(Right, INPUT);
  pinMode(Forward, INPUT);
  pinMode(LM, OUTPUT);
  pinMode(LM_CONST, OUTPUT);
  digitalWrite(LM_CONST, LOW);  
  pinMode(RM, OUTPUT);
  pinMode(RM_CONST, OUTPUT);
  digitalWrite(RM_CONST, LOW);  
  pinMode(pump, OUTPUT); 
  analogWrite(EN_LM, motor_speed); // analogWrite(pin, value) // Enable
  analogWrite(EN_RM, motor_speed); // analogWrite(pin, value) // Enable
  myservo.attach(servoPin);     // servo.attach(pin) 
                          // servo.attach(pin, min, max)
  myservo.write(0);      // set servo to mid-point
                              

}

void loop() {

  if (digitalRead(Left) == 1 & digitalRead(Right) == 1) {
        digitalWrite(LM, HIGH);
        digitalWrite(RM, HIGH); 
        myservo.write(90); 
  }

  else if (digitalRead(Left) == 0) {
        digitalWrite(LM, LOW);
        digitalWrite(RM, HIGH); 
        myservo.write(180); 
        delay(5000);
  }
  else if  (digitalRead(Right) == 0) {
      digitalWrite(LM, HIGH);
      digitalWrite(RM, LOW);  
      myservo.write(270); 
      delay(5000);   
  }     
}

[ruilviana]

How did you measure this voltage? With a DVM?

The Arduino has different PWM frequencies.

One, Nano, Mini pins 3, 9, 10, 11= 490 Hz,
pins 5 and 6 = 980 Hz

If you use a common DVM, you will find different voltage values for the same PWM value.

And step motors are going to have different speeds.

[theeccentricgenius]

Please don't duplicate Topics it is strictly banned.... Your other topic has been flagged.

Please refer to this for more info.

@PerryBebbington

Only ask your question once, in one category of the forum

We know you are anxious to get an answer to your problem, but re-posting the same question to multiple categories of the forum causes duplicate effort, and divides the focus on your problem. You'll get a better answer if everyone can discuss it in one place. Asking the same question multiple times is called cross-posting. Cross-posting is very annoying to people trying to help you. If you cross-post, the moderators will delete your extra posts, and you will get a warning. Save all the hassle, and just post the question once. It will be noticed.

If you aren't sure which category to post in (Programming Questions, General Electronics, etc.), make a guess. Don't cross-post "just in case".

Thank You.

[gcjr]

@jasontit

I am not understand why. Same PWM voltage from the Arduino leads to different output of the L298N.

can you post a link to the specified shield you're using and which pins on the arduino and shield were connected together?

[johnerrington]

As we dont all know EVERY part that can be connected ato an Arduino its always best to post a link to the ACTUAL components you are using. Like this

In-Depth: Interface L298N DC Motor Driver Module with Arduino

@ruilviana

If you use a common DVM, you will find different voltage values for the same PWM value.

I'd not expect that, I guess it depends on the dvm? I'll have to test it.
But the problem is easily solved with a CR low pass filter.

[GolamMostafa]

Probably these are the drivers:

[GolamMostafa]

Try using same frequency PWM (DPin-3, 11: 490 Hz).

Figure-1:

If the above does not solve the problem, then measure the speeds of both motors using IR sensor (Fig-2) and then modulate the PWM signals to keep the same speed for both motors.

Figure-2:

[Ron_Blain]

@jasontit

Hey

I'm trying to control 2 DC motors by using Arduino and L298N and something strange happens.
I'm writing same PWM values in the Arduino PWM pins (3 and 6), but the voltages that I see in the output pins (which is the pins that connect to the motors) of L298N are different (the motors moving in different speed).

I am not understand why. Same PWM voltage from the Arduino leads to different output of the L298N.

You want to control the speed of two motors using PWM with a L298 motor controller. Why am I seeing a bunch of code aimed at a Servo motor? What am I missing and where did this code come from?

Ron

[gcjr]

@GolamMostafa

Probably these are the drivers:

maybe.why guess?

but is it one that has a dir and step pin or one with in1, in2 and en

and which arduino pins are connect to which pin on the driver board

[noweare]

Motors have reactance and if the frequency is too low the motor may not be able to support the voltage which will cause your different dvm readings if the periods of the two channels are different.
I have seen this using a scope, crappy wave forms and whinning from the motor.

[gcjr]

@noweare

I have seen this using a scope, crappy wave forms and whinning from the motor.

would you expect the voltage to be different if the two motors are the same?

[noweare]

The voltage can be different because of the two different frequencies.

[GolamMostafa]

Currently, I have been preparing to drive a 4-wheel Robot Car using L298 driver. If you want I can answer to your questions of post #10.

[gcjr]

@jasontit

//MOTORS
#define LM 11      // left motor - FRONT 
#define LM_CONST 10
#define RM 13      // right motor - FRONT 
#define RM_CONST 12
#define EN_RM 3      // right motor - FRONT 
#define EN_LM 6       // left motor - REAR

@GolamMostafa

If you want I can answer to your questions of post #10.

i don't understand why there are 3 pins allocated for each motor?

the h-bridge chips typically have IN1, IN2 and EN. but driver boards may just have Dir and EN(?).

which board is the OP using?

[GolamMostafa]

@gcjr

which board is the OP using?

@jasontit

I'm trying to control 2 DC motors by using Arduino and L298N and something strange happens.

From his post it is clear that OP is using L298N Motor Driver Board (post #7).

@gcjr

i don't understand why there are 3 pins allocated for each motor?

Referring to Fig-1, I am making this tested Functional Table using ENA, IN1, and IN2 pins for 1st Motor.

ENA     IN1     IN2       Function               +VS (Vcc)        V(OUT1-OUT2)
5V      5V      0V        Forward Rotation       6V               +4.3V
5V      0V      5V        Reverse Rotation       6V               -4.3V
5V      PWM  0V           Forward variable speed 6V               changing

Figure-1:

PWM Test Sketch:

byte dutyCycle = 255;

void setup()
{
  Serial.begin(9600);
}

void loop()
{
  analogWrite(3, dutyCycle);
  dutyCycle -= 20;
  Serial.println(dutyCycle);
  delay(1000);
}

[gcjr]

@jasontit

  else if (digitalRead(Left) == 0) {
        digitalWrite(LM, LOW);
        digitalWrite(RM, HIGH); 
        myservo.write(180); 
        delay(5000);
  }

then why does he control the direction of each motor by just changing one pin?

@gcjr

the h-bridge chips typically have IN1, IN2 and EN. but driver boards may just have Dir and EN(?).

[gcjr]

could it be this driver card?

[GolamMostafa]

@jasontit

Please, post the picture of your L298N Motor driver board.