Add to Wish List

A4988 Stepper Motor Driver Carrier

Rating:
100% of 100
SKU: POLOLU-1182 Brand: Pololu
This breakout board for Allegro’s A4988 microstepping bipolar stepper motor driver features adjustable current limiting, over-current and over-temperature protection, and five different microstep resolutions (down to 1/16-step). It operates from 8 V to 35 V and can deliver up to approximately 1 A per phase without a heat sink or forced air flow (it is rated for 2 A per coil with sufficient additional cooling). This board ships with 0.1″ male header pins included but not soldered in.
$18.20 AUD, inc GST
$16.55 AUD, exc GST

In stock, ships same business day if ordered before 2PM
Delivered by Fri, 19th of Aug

Quantity Discounts:

  • 10-25 $15.88 (exc GST)
  • 25+ $15.39 (exc GST)
- +

9 from local stock, 1 supplier stock; your order will dispatch between Dec 1 to Dec 10. And yes, stock levels and lead times are accurate!

Favourite product

Shipping:

  • $6+ Standard (5+ days*, tracked)
  • $10+ Express (2+ days*, tracked)
  • FREE Pickup (Newcastle only)

Shipping costs may increase for heavy products or large orders.

Exact shipping can be calculated on the view cart page.

*Conditions apply, see shipping tab below.

A4983/A4988 stepper motor driver carrier with dimensions.

This product is a carrier board or breakout board for Allegro’s A4988 DMOS Microstepping Driver with Translator and Overcurrent Protection; Pololu therefore recommend careful reading of the A4988 datasheet (1MB pdf) before using this product. This stepper motor driver lets you control one bipolar stepper motor at up to 2 A output current per coil (see the Power Dissipation Considerations section below for more information). Here are some of the driver’s key features:

  • Simple step and direction control interface
  • Five different step resolutions: full-step, half-step, quarter-step, eighth-step, and sixteenth-step
  • Adjustable current control lets you set the maximum current output with a potentiometer, which lets you use voltages above your stepper motor’s rated voltage to achieve higher step rates
  • Intelligent chopping control that automatically selects the correct current decay mode (fast decay or slow decay)
  • Over-temperature thermal shutdown, under-voltage lockout, and crossover-current protection
  • Short-to-ground and shorted-load protection

This product ships with all surface-mount components—including the A4988 driver IC—installed as shown in the product picture.

This product ships individually packaged with 0.1" male header pins included but not soldered in; Pololu also carry a version with male header pins already soldered in. For customers interested in higher volumes at lower unit costs, Pololu offer a bulk-packaged version without header pins and a bulk-packaged version with header pins installed.

Note that Pololu carry several stepper motor drivers that can be used as alternatives for this module (and drop-in replacements in many applications):

  • The Black Edition A4988 stepper motor driver carrier is available with approximately 20% better performance; except for thermal characteristics, the Black Edition and this (green) board are interchangeable.
  • The MP6500 carrier can deliver up to 1.5 A per phase (continuous) without a heat sink and is available in two versions, one with a pot for controlling the current limit and one with digital current limit control for dynamic current limit adjustment by a microcontroller.
  • The DRV8825 carrier offers approximately 50% better performance over a wider voltage range and has a few additional features.
  • The DRV8834 carrier works with motor supply voltages as low as 2.5 V, making it suitable for low-voltage applications.
  • The DRV8880 carrier offers dynamically scalable current limiting and “AutoTune”, which automatically selects the decay mode each PWM cycle for optimal current regulation performance based on factors like the motor winding resistance and inductance and the motor’s dynamic speed and load.

Pololu also sell a larger version of the A4988 carrier that has reverse power protection on the main power input and built-in 5 V and 3.3 V voltage regulators that eliminate the need for separate logic and motor supplies.

Some unipolar stepper motors (e.g. those with six or eight leads) can be controlled by this driver as bipolar stepper motors. For more information, please see the frequently asked questions. Unipolar motors with five leads cannot be used with this driver.

Included hardware

The A4988 stepper motor driver carrier comes with one 1×16-pin breakaway 0.1" male header. The headers can be soldered in for use with solderless breadboards or 0.1" female connectors. You can also solder your motor leads and other connections directly to the board. (A version of this board with headers already installed is also available.)

Using the driver

Minimal wiring diagram for connecting a microcontroller to an A4988 stepper motor driver carrier (full-step mode).

Power connections

The driver requires a logic supply voltage (3 – 5.5 V) to be connected across the VDD and GND pins and a motor supply voltage (8 – 35 V) to be connected across VMOT and GND. These supplies should have appropriate decoupling capacitors close to the board, and they should be capable of delivering the expected currents (peaks up to 4 A for the motor supply).

Warning: This carrier board uses low-ESR ceramic capacitors, which makes it susceptible to destructive LC voltage spikes, especially when using power leads longer than a few inches. Under the right conditions, these spikes can exceed the 35 V maximum voltage rating for the A4988 and permanently damage the board, even when the motor supply voltage is as low as 12 V. One way to protect the driver from such spikes is to put a large (at least 47 µF) electrolytic capacitor across motor power (VMOT) and ground somewhere close to the board.

Motor connections

Four, six, and eight-wire stepper motors can be driven by the A4988 if they are properly connected; a FAQ answer explains the proper wirings in detail.

Warning: Connecting or disconnecting a stepper motor while the driver is powered can destroy the driver. (More generally, rewiring anything while it is powered is asking for trouble.)

Step (and microstep) size

Stepper motors typically have a step size specification (e.g. 1.8° or 200 steps per revolution), which applies to full steps. A microstepping driver such as the A4988 allows higher resolutions by allowing intermediate step locations, which are achieved by energizing the coils with intermediate current levels. For instance, driving a motor in quarter-step mode will give the 200-step-per-revolution motor 800 microsteps per revolution by using four different current levels.

The resolution (step size) selector inputs (MS1, MS2, and MS3) enable selection from the five step resolutions according to the table below. MS1 and MS3 have internal 100kO pull-down resistors and MS2 has an internal 50kO pull-down resistor, so leaving these three microstep selection pins disconnected results in full-step mode. For the microstep modes to function correctly, the current limit must be set low enough (see below) so that current limiting gets engaged. Otherwise, the intermediate current levels will not be correctly maintained, and the motor will skip microsteps.

MS1 MS2 MS3 Microstep Resolution
Low Low Low Full step
High Low Low Half step
Low High Low Quarter step
High High Low Eighth step
High High High Sixteenth step

Control inputs

Each pulse to the STEP input corresponds to one microstep of the stepper motor in the direction selected by the DIR pin. Note that the STEP and DIR pins are not pulled to any particular voltage internally, so you should not leave either of these pins floating in your application. If you just want rotation in a single direction, you can tie DIR directly to VCC or GND. The chip has three different inputs for controlling its many power states: RST, SLP, and EN. For details about these power states, see the datasheet. Please note that the RST pin is floating; if you are not using the pin, you can connect it to the adjacent SLP pin on the PCB to bring it high and enable the board.

Current limiting

One way to maximize stepper motor performance is to use as high of a voltage as is practical for your application. In particular, increasing the voltage generally allows for higher step rates and stepping torque since the current can change more quickly in the coils after each step. However, in order to safely use voltages above the rated voltage of a stepper motor, the coil current must be actively limited to keep it from exceeding the motor’s rated current.

The A4988 supports such active current limiting, and the trimmer potentiometer on the board can be used to set the current limit. One way to set the current limit is to put the driver into full-step mode and measure the current running through a single motor coil while adjusting the current limit potentiometer. This should be done with the motor holding a fixed position (i.e. without clocking the STEP input). Note that the current you are measuring is only 70% of the actual current limit setting, since both coils are always on and limited to this value in full-step mode, so if you later enable microstepping modes, the current through the coils will be able to exceed this measured full-step current by 40% (1/0.7) on certain steps; please take this into account when using this method to set the current limit. Also, note that you will need to perform this adjustment again if you ever change the logic voltage, Vdd, since the reference voltage that sets the current limit is a function of Vdd.

Note: The coil current can be very different from the power supply current, so you should not use the current measured at the power supply to set the current limit. The appropriate place to put your current meter is in series with one of your stepper motor coils.

Another way to set the current limit is to calculate the reference voltage that corresponds to your desired current limit and then adjust the current limit potentiometer until you measure that voltage on the VREF pin. The VREF pin voltage is accessible on a via that is circled on the bottom silkscreen of the circuit board. The current limit, IMAX, relates to the reference voltage as follows:

IMAX=VREF8⋅RCS" role="presentation" style="position: relative;">IMAX=VREF8·RCSIMAX=VREF8·RCS

or, rearranged to solve for VREF:

VREF=8⋅IMAX⋅RCS" role="presentation" style="position: relative;">VREF=8·IMAX·RCSVREF=8·IMAX·RCS

RCS is the current sense resistance; original versions of this board used 0.050 O current sense resistors, but Pololu switched to using 0.068 O current sense resistors in January 2017, which makes more of the adjustment potentiometer’s range useful. The following picture shows how to identify which current sense resistors your board has:

Identification of original 50 mO sense resistors (left) and 68 mO sense resistors (right) introduced in January 2017.

So, for example, if you want to set the current limit to 1 A and you have a board with 68 mO sense resistors, you would set VREF to 540 mV. Doing this ensures that even though the current through each coil changes from step to step, the magnitude of the current vector in the stepper motor stays constant at 1 A:

ICOIL12+ICOIL22=IMAX=1A" role="presentation" style="position: relative;">I2COIL1+I2COIL2-------------v=IMAX=1AICOIL12+ICOIL22=IMAX=1A

If you instead want the current through each coil to be 1 A in full-step mode, you would need to set the current limit to be 40% higher, or 1.4 A, since the coils are limited to approximately 70% of the set current limit in full-step mode (the equation above shows why this is the case). To do this with a board with 68 mO sense resistors, you would set VREF to 770 mV.

Power dissipation considerations

The A4988 driver IC has a maximum current rating of 2 A per coil, but the actual current you can deliver depends on how well you can keep the IC cool. The carrier’s printed circuit board is designed to draw heat out of the IC, but to supply more than approximately 1 A per coil, a heat sink or other cooling method is required.

This product can get hot enough to burn you long before the chip overheats. Take care when handling this product and other components connected to it.

Please note that measuring the current draw at the power supply will generally not provide an accurate measure of the coil current. Since the input voltage to the driver can be significantly higher than the coil voltage, the measured current on the power supply can be quite a bit lower than the coil current (the driver and coil basically act like a switching step-down power supply). Also, if the supply voltage is very high compared to what the motor needs to achieve the set current, the duty cycle will be very low, which also leads to significant differences between average and RMS currents.

Schematic diagram

Schematic diagram of the A4988 stepper motor driver carrier (both green and black editions).

Note: This board is a drop-in replacement for Pololu's original (and now discontinued) A4983 stepper motor driver carrier. The newer A4988 offers overcurrent protection and has an internal 100k pull-down on the MS1 microstep selection pin, but it is otherwise virtually identical to the A4983.

Dimensions

Size: 0.6" × 0.8"
Weight: 1.3 g1

General specifications

Minimum operating voltage: 8 V
Maximum operating voltage: 35 V
Continuous current per phase: 1 A2
Maximum current per phase: 2 A3
Minimum logic voltage: 3 V
Maximum logic voltage: 5.5 V
Microstep resolutions: full, 1/2, 1/4, 1/8, and 1/16
Reverse voltage protection?: N
Bulk packaged?: N
Header pins soldered?: N4

Identifying markings

PCB dev codes: md09b

Notes:

1
Without included optional headers.
2
Without a heat sink or forced air flow.
3
With sufficient additional cooling.
4
Male header pins are included for the board's 16 holes, but they are not installed.

File downloads

Recommended links

Product Comments

Exact shipping can be calculated on the view cart page (no login required).

Products that weigh more than 0.5 KG may cost more than what's shown (for example, test equipment, machines, >500mL liquids, etc).

We deliver Australia-wide with these options (depends on the final destination - you can get a quote on the view cart page):

  • $3+ for Stamped Mail (typically 10+ business days, not tracked, only available on selected small items)
  • $6+ for Standard Post (typically 6+ business days, tracked)
  • $10+ for Express Post (typically 2+ business days, tracked)
  • Pickup - Free! Only available to customers who live in the Newcastle region (only after we email you to notify your order is ready)

Non-metro addresses in WA, NT, SA & TAS can take 2+ days in addition to the above information.

Some batteries (such as LiPo) can't be shipped by Air. During checkout, Express Post and International Methods will not be an option if you have that type of battery in your shopping cart.

International Orders - the following rates are for New Zealand and will vary for other countries:

  • $11+ for Pack and Track (3+ days, tracked)
  • $16+ for Express International (2-5 days, tracked)

If you order lots of gear, the postage amount will increase based on the weight of your order.

Our physical address (here's a PDF which includes other key business details):

Unit 18, 132 Garden Grove Parade
Adamstown
NSW, 2289
Australia

Take a look at our customer service page if you have other questions such as "do we do purchase orders" (yes!) or "are prices GST inclusive" (yes they are!). We're here to help - get in touch with us to talk shop.

Have a product question? We're here to help!

Write Your Own Review

Videos

View All

Guides

The Maker Revolution

The Maker Revolution celebrates the creation of new devices and the modification of existing ones - ...
The Maker Revolution celebrates the creation of new devices and the modification of existing ones - ...

Motor Drivers vs. Motor Controllers

If you’ve ever built a robot with wheels, or any motorised parts really, you’ll have com...
If you’ve ever built a robot with wheels, or any motorised parts really, you’ll have com...

Projects

MakeCode STEM Arcade Machine

This project came about for a number of reasons. Firstly, we wanted a real showpiece for the sc...
This project came about for a number of reasons. Firstly, we wanted a real showpiece for the sc...

Backyard Birdcam

IntroductionI had been thinking about how best to capture clear close-up photographs of some of the...
IntroductionI had been thinking about how best to capture clear close-up photographs of some of the...

Smart Watering System

Introduction This began as an idea after building a very basic single-channel unit. Commercial sma...
Introduction This began as an idea after building a very basic single-channel unit. Commercial sma...
Feedback

Please continue if you would like to leave feedback for any of these topics:

  • Website features/issues
  • Content errors/improvements
  • Missing products/categories
  • Product assignments to categories
  • Search results relevance

For all other inquiries (orders status, stock levels, etc), please contact our support team for quick assistance.

Note: click continue and a draft email will be opened to edit. If you don't have an email client on your device, then send a message via the chat icon on the bottom left of our website.