Controling two motors with 2 pots and an H bridge.

Projects Programming
1

I am trying to control 2 small dc motors using two joystick potentiometers but im having trouble with the code.

My code:

//Arduino control of two motors via an H bridge using two joysticks

#define enA 6 //Enable A on H bridge connected to 6
#define in1 4
#define in2 7
#define enB 5 //Enable B on H bridge connected to 5
#define in3 3
#define in4 2

int motorSpeedA = 0;
int motorSpeedB = 0;

void setup()
{
pinMode(enA, OUTPUT);
pinMode(in1, OUTPUT);
pinMode(in2, OUTPUT);
pinMode(enB, OUTPUT);
pinMode(in3, OUTPUT);
pinMode(in4, OUTPUT);
Serial.begin( 9600 );
}

void loop()
{
int Ain = analogRead(A0); // Read Pot A
int Bin = analogRead(A1); // Read Pot B

if (Ain < 505)
{
// Set Motor A backward
digitalWrite(in1, LOW);
digitalWrite(in2, HIGH);
motorSpeedA = map(Ain, 505, 0, 0, 255);
}
else if (Ain > 515)
{
// Set Motor A forward
digitalWrite(in1, HIGH);
digitalWrite(in2, LOW);
motorSpeedA = map(Ain, 515, 1023, 0, 255);
}

if (Bin < 505)
{
// Set Motor B backward
digitalWrite(in3, HIGH);
digitalWrite(in4, LOW);
motorSpeedB = map(Bin, 505, 0, 0, 255);
}
else if (Bin > 515)
{
// Set Motor B forward
digitalWrite(in3, LOW);
digitalWrite(in4, HIGH);
motorSpeedB = map(Bin, 515, 1023, 0, 255);
}

else
{
motorSpeedA = 0;
motorSpeedB = 0;
}

analogWrite(enA, motorSpeedA); // Send PWM signal to motor A
analogWrite(enB, motorSpeedB); // Send PWM signal to motor B

Serial.print(Ain );
Serial.print (" Motor A Speed ");
Serial.print(motorSpeedA);
Serial.print (" : ");
Serial.print(Bin );
Serial.print (" Motor B Speed ");
Serial.print(motorSpeedB);
Serial.println ();

}

The last Serial print lines are just there to see what's happening on the serial monitor.

the program almost works.
But motor A will only work if motor B is turning.
Motor B will work perfectly in both directions irrespective of motor A.
Its not wiring because Serial print shows no output on (motorSpeedA)
If I swap the sections of the script, so B is before A the symptoms are reversed.
A works perfectly but B only works when A is turning.

Any help or guidance appreciated

2

Please use the code button </> so your code looks like this - it makes it much easier to help you.

//Arduino control of two motors via an H bridge using two joysticks 

#define enA 6 //Enable A on H bridge connected to 6
#define in1 4
#define in2 7
#define enB 5 //Enable B on H bridge connected to 5
#define in3 3
#define in4 2

int motorSpeedA = 0;
int motorSpeedB = 0;

void setup()
{
    pinMode(enA, OUTPUT);
    pinMode(in1, OUTPUT);
    pinMode(in2, OUTPUT);
    pinMode(enB, OUTPUT);
    pinMode(in3, OUTPUT);
    pinMode(in4, OUTPUT);
    Serial.begin( 9600 );
}

void loop()
{
    int Ain = analogRead(A0); // Read Pot A
    int Bin = analogRead(A1); // Read Pot B
 
    if (Ain < 505)
    {
            // Set Motor A backward
        digitalWrite(in1, LOW);
        digitalWrite(in2, HIGH);
        motorSpeedA = map(Ain, 505, 0, 0, 255);
    }
    else if (Ain > 515)
    {
            // Set Motor A forward
        digitalWrite(in1, HIGH);
        digitalWrite(in2, LOW);
        motorSpeedA = map(Ain, 515, 1023, 0, 255);
    }
    
    if (Bin < 505)
    {
            // Set Motor B backward
        digitalWrite(in3, HIGH);
        digitalWrite(in4, LOW);
        motorSpeedB = map(Bin, 505, 0, 0, 255);
    }
    else if (Bin > 515)
    {
            // Set Motor B forward
        digitalWrite(in3, LOW);
        digitalWrite(in4, HIGH);
        motorSpeedB = map(Bin, 515, 1023, 0, 255);
    }
    
    else
    {
        motorSpeedA = 0;
        motorSpeedB = 0;
    }
    
    analogWrite(enA, motorSpeedA); // Send PWM signal to motor A
    analogWrite(enB, motorSpeedB); // Send PWM signal to motor B
    
    Serial.print(Ain );
    Serial.print (" Motor A Speed  ");
    Serial.print(motorSpeedA);
    Serial.print (" : ");
    Serial.print(Bin );
    Serial.print (" Motor B Speed  ");
    Serial.print(motorSpeedB);
    Serial.println ();
 
}

Note how i have also indented your code consistently so you can see what part belongs with what.

I believe the problem is that the ELSE on line 59 only applies to the IF on line 44. In other words the IF that controls motor B.

You should probably have a separate ELSE for each of the motors.

...R

3

What exactly are you trying to achieve ?
An h-bridge is typically used to drive ONE motor both forward & reverse with PWM.
Two Motors require two bridges, or a simple MOSFET each for single direction control.