How to Use md20b: Examples, Pinouts, and Specs

The MD20B, manufactured by Pololu, is a compact and efficient DC motor driver designed to control the speed and direction of DC motors. It is equipped with built-in protection features, including overcurrent and thermal overload safeguards, ensuring reliable operation in demanding environments. This motor driver is ideal for robotics, automation systems, and other applications requiring precise motor control.

• Robotics and mechatronics projects
• Automated conveyor systems
• Remote-controlled vehicles
• Industrial automation
• Educational electronics projects

The MD20B motor driver is designed to handle a wide range of DC motor control tasks. Below are its key technical details:

The MD20B features a simple pinout for easy integration into your circuits. Below is the pin configuration:

1. Power Supply: Connect the VIN and GND pins to a DC power supply within the range of 6 V to 30 V. Ensure the power supply can provide sufficient current for your motor.
2. Motor Connection: Connect the motor terminals to the M1+ and M1- pins.
3. Control Signals:
   • Connect the PWM pin to a microcontroller or PWM signal generator to control motor speed.
   • Use the DIR pin to set the motor's direction (HIGH for forward, LOW for reverse).
   • The EN pin must be set HIGH to enable the motor driver.
4. Fault Monitoring: Optionally, connect the FAULT pin to a microcontroller input to monitor fault conditions.

• Heat Dissipation: The MD20B may generate heat during operation. Ensure adequate ventilation or use a heatsink if operating at high currents for extended periods.
• Current Limits: Do not exceed the continuous current rating of 20 A to avoid damage.
• PWM Frequency: Use a PWM frequency between 1 kHz and 20 kHz for optimal performance.
• Logic Voltage: Ensure the control signals (PWM, DIR, EN) are within the 3.3 V to 5 V range.

Below is an example of how to control a DC motor using the MD20B and an Arduino UNO:

// Define pin connections
const int pwmPin = 9;  // PWM signal pin
const int dirPin = 8;  // Direction control pin
const int enPin = 7;   // Enable pin

void setup() {
  // Set pin modes
  pinMode(pwmPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
  pinMode(enPin, OUTPUT);

  // Enable the motor driver
  digitalWrite(enPin, HIGH);
}

void loop() {
  // Set motor direction to forward
  digitalWrite(dirPin, HIGH);

  // Gradually increase motor speed
  for (int speed = 0; speed <= 255; speed++) {
    analogWrite(pwmPin, speed);  // Set PWM duty cycle
    delay(20);                   // Wait 20 ms
  }

  // Hold maximum speed for 2 seconds
  delay(2000);

  // Gradually decrease motor speed
  for (int speed = 255; speed >= 0; speed--) {
    analogWrite(pwmPin, speed);  // Set PWM duty cycle
    delay(20);                   // Wait 20 ms
  }

  // Set motor direction to reverse
  digitalWrite(dirPin, LOW);

  // Repeat the speed ramp-up and ramp-down
  for (int speed = 0; speed <= 255; speed++) {
    analogWrite(pwmPin, speed);
    delay(20);
  }
  delay(2000);
  for (int speed = 255; speed >= 0; speed--) {
    analogWrite(pwmPin, speed);
    delay(20);
  }
}

1. Motor Not Spinning:

   • Ensure the EN pin is set HIGH to enable the motor driver.
   • Verify that the power supply voltage is within the 6 V to 30 V range.
   • Check the PWM signal and ensure it is being generated correctly.

2. Motor Spins in the Wrong Direction:

   • Reverse the DIR pin signal (HIGH for forward, LOW for reverse).
   • Alternatively, swap the motor connections on the M1+ and M1- pins.

3. Overheating:

   • Ensure proper ventilation or attach a heatsink to the MD20B.
   • Reduce the motor load or operating current if possible.

4. FAULT Pin is Active (LOW):

   • Check for overcurrent or thermal overload conditions.
   • Allow the driver to cool down if it has overheated.
   • Verify that the motor is not drawing more than 20 A continuously.

Q: Can I use the MD20B with a 3.3 V microcontroller?
A: Yes, the MD20B supports control signals in the 3.3 V to 5 V range, making it compatible with 3.3 V microcontrollers.

Q: What type of motors can the MD20B drive?
A: The MD20B is designed for brushed DC motors. It is not suitable for brushless motors.

Q: How do I reset the driver after a fault condition?
A: Remove the fault condition (e.g., reduce load or allow cooling), then toggle the EN pin LOW and HIGH to reset the driver.

Q: Can I use the MD20B for bidirectional motor control?
A: Yes, the DIR pin allows you to control the motor's direction, enabling bidirectional operation.