The A4988 is a complete microstepping driver for bipolar stepper motors, built around the Allegro A4988 chip on the standard StepStick footprint used by RAMPS, CNC shields and most 3D printer controllers. A simple STEP and DIR interface handles motion, an onboard trimpot sets the current limit, and five resolution modes take you from full step down to smooth 1/16 microstepping. Each board ships with a self-adhesive heatsink and pre-soldered headers, ready to drop in.
- Drives one bipolar stepper (NEMA 17, NEMA 14 and similar)
- Up to 2A per phase with the heatsink fitted and airflow
- Full, 1/2, 1/4, 1/8 and 1/16 microstepping via MS1/MS2/MS3
- Simple STEP / DIR control from any microcontroller
- Adjustable current limit through the onboard trimpot (VREF)
- 8-35V motor supply, 3-5.5V logic supply
- Built-in over-temperature, over-current and short protection
- Heatsink and pre-soldered headers included
Specifications
What's in the box
One A4988 driver module with pre-soldered headers and one self-adhesive aluminium heatsink. Stepper motor and controller board sold separately.
Great for
Getting started
- Wire the power and motor
Connect your motor supply (8-35V) to VMOT/GND and your stepper's two coils to 1A/1B and 2A/2B. Always fit the 100uF bypass capacitor recommended for your supply.
- Connect logic and control
Feed VDD/GND from your 5V logic and drive STEP and DIR from your microcontroller or control board. Set MS1/MS2/MS3 to pick the microstep resolution.
- Set the current limit
Measure VREF at the trimpot and adjust it to match your motor's rated current before running under load. This is the single most important step for cool, reliable operation.
- Stick on the heatsink
Peel and press the included heatsink onto the A4988 chip so it can run harder without thermal shutdown.
Common questions
Does it come with a heatsink?
Yes. Every board ships with a self-adhesive aluminium heatsink and pre-soldered headers.
How much current can it really handle?
About 1A per phase with no extra cooling, and up to 2A per phase with the heatsink fitted and some airflow. Always set the VREF current limit to your motor, not the maximum.
Is it compatible with RAMPS and CNC shields?
Yes. It uses the standard StepStick pin layout, so it drops straight into RAMPS 1.4, CNC shields, and most 3D printer and GRBL control boards.
What is the difference between the A4988 and DRV8825?
The A4988 does up to 1/16 microstepping and around 1-2A per phase, while the DRV8825 pushes higher voltage and current with up to 1/32 microstepping. The A4988 is the classic, well-supported choice for most 3D printers and light-to-medium steppers.
Can it run a unipolar motor like the 28BYJ-48?
No. The A4988 is for bipolar (4-wire) steppers such as NEMA 17. Small unipolar motors like the 28BYJ-48 use a different driver such as the ULN2003.
Do I need a capacitor across the motor supply?
Yes, it is strongly recommended. Fit an electrolytic capacitor (typically 100uF) across VMOT and GND to protect the driver from voltage spikes when the motor moves.
Good to know: Set the VREF current limit before running your motor under load, and never connect or disconnect a stepper while the driver is powered, as this can destroy the board. Every driver is checked before it ships from our Te Awamutu stock.