How to Use A4988 Stepper Driver: Examples, Pinouts, and Specs

The A4988 is a microstepping driver designed for controlling bipolar stepper motors. It enables precise control of motor position and speed, making it ideal for applications requiring high accuracy and smooth motion. The driver features adjustable current control, over-temperature protection, and a straightforward interface, making it easy to integrate into a wide range of projects.

• 3D printers
• CNC machines
• Robotics
• Automated systems
• Camera sliders and gimbals

The A4988 stepper driver is a compact and versatile component with the following key specifications:

The A4988 has 16 pins, each serving a specific function. Below is the pinout and description:

1. Power Connections:

   • Connect the VMOT pin to the motor power supply (8 V to 35 V).
   • Connect the GND pins to the ground of both the motor and logic power supplies.
   • Connect the VDD pin to the logic power supply (3.3 V or 5 V).

2. Motor Connections:

   • Connect the stepper motor coils to the OUT1A, OUT1B, OUT2A, and OUT2B pins. Ensure the correct pairing of the motor wires.

3. Control Pins:

   • Use the STEP pin to control the motor's steps. Each rising edge moves the motor one step.
   • Use the DIR pin to set the motor's rotation direction.
   • Adjust the microstepping resolution using the MS1, MS2, and MS3 pins.

4. Current Adjustment:

   • Use the onboard potentiometer to set the current limit. This prevents overheating and ensures optimal motor performance.

5. Optional Features:

   • Use the ENABLE pin to enable or disable the driver.
   • Use the SLEEP pin to put the driver into low-power mode when not in use.

Below is an example of how to control a stepper motor using the A4988 and an Arduino UNO:

• Connect the A4988's STEP and DIR pins to Arduino digital pins 2 and 3, respectively.
• Connect the ENABLE pin to ground to enable the driver.
• Connect the motor power supply to VMOT and GND.
• Connect the stepper motor coils to the OUT1A, OUT1B, OUT2A, and OUT2B pins.

// Define pin connections
#define STEP_PIN 2  // Connect to A4988 STEP pin
#define DIR_PIN 3   // Connect to A4988 DIR pin

void setup() {
  pinMode(STEP_PIN, OUTPUT); // Set STEP pin as output
  pinMode(DIR_PIN, OUTPUT);  // Set DIR pin as output

  digitalWrite(DIR_PIN, HIGH); // Set initial direction (HIGH = clockwise)
}

void loop() {
  // Generate a step pulse
  digitalWrite(STEP_PIN, HIGH); // Set STEP pin HIGH
  delayMicroseconds(1000);      // Wait 1 ms
  digitalWrite(STEP_PIN, LOW);  // Set STEP pin LOW
  delayMicroseconds(1000);      // Wait 1 ms
}

• Cooling: The A4988 can handle up to 2 A per coil with proper cooling. Use a heat sink or active cooling for high-current applications.
• Current Limiting: Always set the current limit to match your stepper motor's rated current to avoid damage.
• Microstepping: Configure the MS1, MS2, and MS3 pins to achieve the desired microstepping resolution.

1. Motor Not Moving:

   • Check the power supply connections to VMOT and VDD.
   • Ensure the STEP pin is receiving pulses.
   • Verify the motor coil connections to the OUT pins.

2. Motor Vibrates but Does Not Rotate:

   • Check the DIR pin connection and logic level.
   • Verify the correct pairing of motor wires.

3. Driver Overheating:

   • Ensure the current limit is set correctly using the potentiometer.
   • Add a heat sink or active cooling to the driver.

4. Motor Moves Erratically:

   • Check for loose connections in the circuit.
   • Verify the microstepping configuration on the MS1, MS2, and MS3 pins.

Q: Can I use the A4988 with a unipolar stepper motor?
A: No, the A4988 is designed for bipolar stepper motors only.

Q: How do I calculate the current limit?
A: Use the formula: Current Limit = VREF / (8 * RS), where VREF is the voltage on the potentiometer and RS is the sense resistor value (typically 0.1 Ω).

Q: What happens if I exceed the maximum voltage?
A: Exceeding 35 V on the VMOT pin can permanently damage the driver. Always use a power supply within the specified range.

Q: Can I control multiple stepper motors with one A4988?
A: No, each A4988 driver can control only one bipolar stepper motor. Use separate drivers for multiple motors.