DC motor with L289N driver cannot set RPM lower than 130

Question

My setup is using an Uno r3, and the motor driver is an L289N.

I am going to set it to run at a lower RPM, but when adjusting enA or enB to set to below 130, it won't spin.

// connect motor controller pins to Arduino digital pins
// motor one
int enA = 2;
int enB = 7;
int in3 = 5;
int in4 = 6;
int in1 = 3;
int in2 = 4;

void setup()
{
  // set all the motor control pins to outputs
  pinMode(enA, OUTPUT);
  pinMode(enB, OUTPUT);
  pinMode(in3, OUTPUT);
  pinMode(in4, OUTPUT);
}
void demoOne()
{
  analogWrite(enB, 130);
  // turn on motor B
  digitalWrite(in1, LOW);
  digitalWrite(in2, HIGH);
  delay(500);
  digitalWrite(in1, LOW);
  digitalWrite(in2, LOW);
  delay(5000);
  // this function will run the motors in both directions at a fixed speed
  // turn on motor A
  // set speed to 200 out of possible range 0~255
  analogWrite(enA, 130);
  // turn on motor B
  digitalWrite(in3, HIGH);
  digitalWrite(in4, LOW);
  // set speed to 200 out of possible range 0~255
  delay(100); //this function to set masa untuk rotation
  // now change motor directions
  // now turn off motor
  digitalWrite(in3, LOW);
  digitalWrite(in4, LOW);
  delay(5000);
  digitalWrite(in3, LOW);
  digitalWrite(in4, HIGH);
  delay(200);
  digitalWrite(in3, LOW);
  digitalWrite(in4, LOW);
  delay(5000);
  digitalWrite(in3, HIGH);
  digitalWrite(in4, LOW);
  delay(200); 
  digitalWrite(in3, LOW);
  digitalWrite(in4, LOW);
  delay(5000);
  digitalWrite(in3, LOW);
  digitalWrite(in4, HIGH);
  delay(100);
  digitalWrite(in3, LOW);
  digitalWrite(in4, LOW);
  delay(5000);

  analogWrite(enB, 130);
  // turn on motor B
  digitalWrite(in1, HIGH);
  digitalWrite(in2, LOW);
  delay(400);
  digitalWrite(in1, LOW);
  digitalWrite(in2, LOW);
  delay(5000);
}

void loop()
{
  demoOne();
  delay(3000);

}

score 1 · Answer 1 · answered Jul 08 '18 at 09:29

Looks like you are controlling two motor outputs via the H-bridge, where the logic inputs are in1,in2 and in3,in4. First of all, you need

pinMode(in1,OUTPUT);
pinmode(in2,OUTPUT);

One reason why the motors may not spin for analogWrite value less than 130 is that, coincidentally, the voltage output is too low and motor stalls. Test this two ways: does (1) changing the motor supply voltage or (2) changing the argument of analogWrite actually change the speed?

If no, it may be that pinMode(enA,OUTPUT); sets the output as digital and should be removed. In that case a number less than 128 gets interpreted as a logic 0 and the motor will not spin.

P.S. your code can be neatened up using port syntax and bitwise operators.

digitalWrite(in1,HIGH);
digitalWrite(in2,LOW);

can be written on a single line with

PORTD |= _BV(in1);

Also

digitalWrite(in1,LOW);
digitalWrite(in2,LOW);

becomes

PORTD &= ~(_BV(in1) | _BV(in2));

score 0 · Answer 2 · edited Jul 10 '18 at 07:18

0

On an Uno, D2 and D7 (enA and enB) do not have true PWM (analogWrite) capabilities- they will be 100% on at values of 128 or higher, and off at 127 and lower.

You will need to use 3, 5, 6, 9, 10 or 11 for PWM (i.e. your enA and enB) on the Uno.

See Arduino Reference - analogWrite() for more info on PWM pin availability on Arduino boards.

edited Jul 10 '18 at 07:18

Greenonline

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answered Jul 10 '18 at 06:26

user85471

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DC motor with L289N driver cannot set RPM lower than 130

2 Answers2