GK-A4988 geeekus A4988 Stepper Motor Driver Module with Heat Sink for 3d Printer CNC Machine

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The geeekus A4988 Stepper Motor Driver is an ideal solution for building applications that require precise and reliable stepper motor control, such as the movement control of beds, heads, and assemblies in various CNC plotting, milling, 3D printer designs, etc.

If your project calls for single-stepper-motor applications, a driver like the L298N is acceptable.If you want to build your own CNC machine or 3D printer, you’ll need a dedicated stepper motor driver like the A4988. It's also great that it only requires two pins to control the speed and direction of a bipolar stepper motor like the NEMA 17. At the heart of the module is a microstepping driver from Allegro – A4988. Despite its small size (0.8″x0.6″) it has an output drive capacity of up to 35V and ±2A. This allows you to control a bipolar stepper motor, such as the NEMA 17, at up to 2A output current per coil. Also, the output current is regulated, allowing for noiseless operation of the stepper motor and the elimination of resonance or ringing that is common in unregulated stepper driver designs.

The driver has a built-in translator for easy operation. This reduces the number of control pins to just two, one for controlling the steps and the other for controlling the spinning direction.

The driver offers five different step resolutions: full-step, half-step, quarter-step, eighth-step, and sixteenth-step. In order to ensure reliable operation, the driver has additional features such as under-voltage, shoot-through, short circuit, overcurrent, and thermal protection.


  • 1.Only a simple step and direction control interface;
  • 2.Five different step modes: full, half, 1/4, 1/8 and 1/16;
  • 3.Adjustable potentiometer can adjust the maximum current output, resulting in a higher step rate;
  • 4.Automatic current decay mode detection / selection;
  • 5.Overheat shutdown circuit, undervoltage lockout, cross current protection;
  • 6.Ground short circuit protection and load short circuit protection.

Setting method of working mode

a4988 working mode

Adjusting Driver Current

1.When you use the A4988 to drive the stepper motor, turn the potentiometer on the A4988 module to adjust the upper limit of the output current.
2. The calculation formula of the current upper limit is I=VREF/(8*Rs)
3. Rs is the reference resistor; the reference resistor for this module is 0.05Ω. VREF=I*8*0.05=0.4I
4. The current limit of the module is 2A, so VREF=2*0.4, that is, 0.8V.  

a4988 driver current

The voltage between the marked potentiometer and GND is VREF

Connection Diagram

It needs to connect DC 8-15V between motor power VMOT and GND

a4988 connection diagram


a4988 Pinouts

Sample Code

int dirPin = 7;
int stepperPin = 8;
void setup() {
pinMode(dirPin, OUTPUT);
pinMode(stepperPin, OUTPUT);
void step(boolean dir,int steps){
for(int i=0;i<steps;i++){
digitalWrite(stepperPin, HIGH);
digitalWrite(stepperPin, LOW);
void loop(){
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