ROB-12859 - SparkFun Electronics

Big Easy Driver Hookup Guide

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Big Easy Driver Hook-Up Guide SparkFun Wish List

CONTRIBUTORS: TONI_K

Introduction

The Big Easy Driver gives you the capability to drive stepper motors that

pull up to 2A/phase. This driver defaults to 16 step microstepping mode,

and gives you control of motor speed and location.

Materials Required

To follow along with this tutorial, we recommend you have access to the

following materials.

Jumper Wires Premium 6" M/M - 20 AWG (10 Pack)

PRT-11709

Jumper wires are awesome. Just a little bit of stranded core wire with …

Screw Terminals 3.5mm Pitch (2-Pin)

PRT-08084

Screw Terminals with 3.5mm pitch pins. Comes in 2 or 3 positions an…

rduino Uno - R3

DEV-11021

This is the new Arduino Uno R3. In addition to all the features of the p…

Stepper Motor - 68 oz.in (400 steps/rev)

ROB-10846

These steppers are a great way to get things moving, especially when …

You can either solder screw terminals or standard headers for attaching

things to the Big Easy Driver. The best option for you will depend on your

application.

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Suggested Readin

If you aren’t familiar with the following concepts, we recommend reviewing

them before beginning to work with the Big Easy Driver.

• Installing the Arduino IDE

• How to Power Your Project

• Battery Technologies

• How to Solder

• Working with Wire

• Motor Basics

Hardware Overview

The Big Easy Driver is designed around the Allegro A4988 motor driver.

Each pin present on the board has two connection points. The first, which

are the pins closest to the center of the board, are spaced out to fit

standard 0.1" headers. The secondary connection points are closest to the

edge of the board, and are spaced to fit 2-pin screw terminals. You can use

whichever pin connections work best for your project. Functionality between

the two sets does not change.

Pin Descriptions

Several pins of the A4988 IC are broken out on the Big Easy Driver,

allowing direct connection to a bi-polar stepper motor, as well as a

microcontroller.

Board Top Pins

•Coil A+: DMOS Full Bridge 1 Output B. Half of connection point for

bi-polar stepper motor coil A.

•Coil A-: DMOS Full Bridge 1 Output A. Other half of connection point

for bi-polar stepper motor coil A.

•Coil B+: DMOS Full Bridge 2 Output B. Half of connection point for

bi-polar stepper motor coil B.

•Coil B-: DMOS Full Bridge 2 Output A. Other half of connection point

for bi-polar stepper motor coil B.

•GND: Ground.

•M+: Power supply. 8V - 35V.

Bottom Pins

•ENABLE: Logic Input. Enables the FET functionality within the motor

driver. If set to HIGH, the FETs will be disabled, and the IC will not

drive the motor. If set to LOW, all FETs will be enabled, allowing

motor control.

•MS1: Logic Input. Microstep Select 1 has a pull-down resistance of

100 kOhms. See truth table below for HIGH/LOW functionality.

•MS2: Logic Input. Microstep Select 2 has a pull-down resistance of

50 kOhms. See truth table below for HIGH/LOW functionality.

•MS3: Logic Input. Microstep Select 3 has a pull-down resistance of

100 kOhms. See truth table below for HIGH/LOW functionality.

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Microstep Select Resolution Truth Table

MS1 MS2 MS3 Microstep Resolution Excitation Mode

L L L Full Step 2 Phase

H L L Half Step 1-2 Phase

L H L Quarter Step W1-2 Phase

H H L Eigth Step 2W1-2 Phase

H H H Sixteenth Step 4W1-2 Phase

•RST: Logic Input. When set LOW, all STEP commands are ignored

and all FET functionality is turned off. The translator is set to the

Home state as well. This must be set HIGH to enable functionality of

the motor driver.

•SLEEP: Logic Input. When set to LOW, the A4988 enters sleep

mode, and disables functionality of the FETs, internal current

regulator and charge pump. When switching this pin to HIGH to wake

up the IC, allow 1 ms of delay before sending a STEP signal. The IC

will return the motor to the starting position upon receiving a HIGH

signal on this pin.

•VCC: Logic Supply.

•GND: Ground.

•STEP: Logic Input. Any transition on this pin from LOW to HIGH will

trigger the motor to step forward one step. Direction and size of step

is controlled by DIR and MSx pin settings.

•DIR: Logic Input. This pin determines the direction of motor rotation.

Changes in state from HIGH to LOW or LOW to HIGH only take

effect on the next rising edge of the STEP command.

Solder Jumpers

There are two solder jumpers present on the board.

•APWR - This solder jumper allows the user to use VCC as a power

supply for external devices. The Big Easy Driver requires 15mA to

operate, and the voltage regulator that outputs VCC can only supply

100mA. Keep this in mind when planning to power any additional

devices off of VCC.

•5V/3.3V - This jumper allows the user to set the configuration of VCC

between 3.3V or 5V. With the jumper open, VCC will be 5V. If the

jumper is closed, VCC is 3.3V.

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Potentiometer

The potentiometer on board is included to allow users the ability to select

the current provided to the motor. It ranges from 0mA to 2000mA (2A). This

will require you to be aware what current range your motor can handle -

check the motor’s data sheet for the current settings.

If you can’t find this information, have no fear – you can still find the proper

setting for the potentiometer. First, set it to the lowest setting of the

potentiometer. Keep in mind that the potentiometer is delicate, so be careful

to not force the potentiometer past the mechanical stops when turning it.

Once you have the motor being driven at a slow, yet steady speed, slowly

turn the potentiometer and pay attention to the motor’s behavior. You

should find a sweet spot where the motor doesn’t skip or jerk between

steps.

Hardware Hookup

Connect Motor Coil Wires

You will need to determine the wire pairs for each coil on the motor you

plan to use. The most reliable method to do this is to check the datasheet

for the motor.

Coil wire diagram from the datasheet for our 68 oz.in, NEMA -17 Stepper

Motor.

However, if you are using a 4-wire or 6-wire stepper motor, it is still possible

to determine the coil wire pairs without the datasheet.

For a 4-wire motor, take one wire and check its resistance against each of

the three remaining wires. Whichever wire shows the lowest resistance

against the first wire is the pair mate. The remaining two wires should show

similar resistance between the two of them.

For a 6-wire motor, you will need to determine which of three the wires go

together for one coil. Pick one wire, and test this against all other wires.

Two wires should show some resistance between them and the first wire

picked, while the other three will show no connection at all. Once the three

wires for one coil have been determined, find two of the three that show the

highest resistance between them. These will be your two coil wires. Repeat

for the second group of three wires.

Once you have determined the coil wire pairs, you will need to attach them

to the Big Easy Driver. The first coil pair should be plugged into Coil A+ and

Coil A-, while the second coil pair plugs into Coil B+ and Coil B-. There is

no polarity on the coils, so you don’t need to worry about plugging in a coil

backwards on the board. In our example, we are using a 4-coil motor. The

connections between the Big Easy Driver and motor are as follows.

Big Easy Driver → Motor

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•A+ → Red Wire

•A- → Green Wire

•B+ → Blue Wire

•B- → Yellow Wire

Note: Do not connect or disconnect the motor while the Big Easy

Driver is powered.

Connect a Power Supply

Once your motor is connected, you can then connect a power supply to the

Big Easy Driver. You can use any kind of power supply (desktop, wall

adapter, battery power, etc.), but verify that whatever choice you go with is

capable of providing up to 2A and falls in the range of 8V to 35V.

Connect the power supply to M+ and GND. REMEMBER to disconnect

the power before connecting/disconnecting your motor.

Connect a Microcontroller

For this example, we will be using an Arduino Uno R3. However, any

microcontroller that works at 3.3V or 5V logic and has digital I/O with PWM

capability will work for this example.

Here are the following pin connections for our example.

Uno → Big Easy Driver

•D2 → DIR

•D3 → STEP

•D4 → MS1

•D5 → MS2

•D6 → MS3

•D7 → ENABLE

• GND → GND

Final Circuit

Once everything is connected, your setup should look like this:

Arduino Code

Basic Arduino Example

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Now that you have the hardware hooked up and ready to go, it’s time to get

the code uploaded. Download the Arduino code here, or for the most up-to-

date code available, please check the GitHub repository. If you need a

reminder as to how to install an Arduino library, please check out our

tutorial here.

The first section of the sketch defines all of the pin connections between the

Arduino and the Big Easy Driver. It also sets these pins as outputs, and

puts them to the proper logic levels to begin driving the motor.

//Declare pin functions on Arduino

#define stp 2

#define dir 3

#define MS1 4

#define MS2 5

#define MS3 6

#define EN 7

//Declare variables for functions

char user_input;

int x;

int y;

int state;

void setup() {

pinMode(stp, OUTPUT);

pinMode(dir, OUTPUT);

pinMode(MS1, OUTPUT);

pinMode(MS2, OUTPUT);

pinMode(MS3, OUTPUT);

pinMode(EN, OUTPUT);

resetBEDPins(); //Set step, direction, microstep and enable

pins to default states

Serial.begin(9600); //Open Serial connection for debugging

Serial.println("Begin motor control");

Serial.println();

//Print function list for user selection

Serial.println("Enter number for control option:");

Serial.println("1. Turn at default microstep mode.");

Serial.println("2. Reverse direction at default microstep mo

de.");

Serial.println("3. Turn at 1/16th microstep mode.");

Serial.println("4. Step forward and reverse directions.");

Serial.println();

}

One thing worth noting is that the code also initializes the serial connection

at 9600bps. This enables the user (you!) to control the motor’s functionality

and debug your circuit if needed.

The main loop of the code is pretty simple. The Arduino scans the serial

port for input from the user. When it is received, it’s compared to the four

possible functions for the motor, which are triggered from user input. If no

valid input is received, the Arduino prints an error over the serial port. After

the requested function is completed, the pins on the Big Easy Driver are

reset to the defaults.

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//Main loop

void loop() {

while(Serial.available()){

user_input = Serial.read(); //Read user input and trigge

r appropriate function

digitalWrite(EN, LOW); //Pull enable pin low to set FET

s active and allow motor control

if (user_input =='1')

{

StepForwardDefault();

}

else if(user_input =='2')

{

ReverseStepDefault();

}

else if(user_input =='3')

{

SmallStepMode();

}

else if(user_input =='4')

{

ForwardBackwardStep();

}

else

{

Serial.println("Invalid option entered.");

}

resetBEDPins();

}

The first of the four functions this demo sketch enables is a basic example

to show the motor spinning in one direction. The direction pin is held LOW,

which for our sketch, we define as the ‘foreword’ direction. The sketch then

transitions the step pin HIGH, pauses, and then pulls it LOW. Remember,

the motor only steps when the step pin transitions from LOW to HIGH, thus

we have to switch the state of the pin back and forth. This is repeated 1000

times, and then the Arduino requests more user input to determine the next

motor activity.

//Default microstep mode function

void StepForwardDefault()

{

Serial.println("Moving forward at default step mode.");

digitalWrite(dir, LOW); //Pull direction pin low to move "fo

rward"

for(x= 1; x<1000; x++) //Loop the forward stepping enough t

imes for motion to be visible

{

digitalWrite(stp,HIGH); //Trigger one step forward

delay(1);

digitalWrite(stp,LOW); //Pull step pin low so it can be tr

iggered again

delay(1);

}

Serial.println("Enter new option");

Serial.println();

}

The reverse function works exactly the same as the forward function. The

only difference is that instead of pulling the direction pin LOW, we set it

HIGH, thus switching the direction of the motor spin. One thing you can try

on either of these first two functions is modifying the motor speed by

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changing the value in delay() . It is currently set to 1 microsecond, making

each step pulse take 2 microseconds. Increasing the delay will slow down

the motor, while decreasing the delay will speed up the motor.

//Reverse default microstep mode function

void ReverseStepDefault()

{

Serial.println("Moving in reverse at default step mode.");

digitalWrite(dir, HIGH); //Pull direction pin high to move i

n "reverse"

for(x= 1; x<1000; x++) //Loop the stepping enough times fo

r motion to be visible

{

digitalWrite(stp,HIGH); //Trigger one step

delay(1);

digitalWrite(stp,LOW); //Pull step pin low so it can be tr

iggered again

delay(1);

}

Serial.println("Enter new option");

Serial.println();

}

The third function shows off the different microstepping functionality that the

Big Easy Driver provides. To enable the motor to step in 1/16th microsteps,

we must set MS1, MS2, and MS3 HIGH. This sets the logic of the board to

1/16th microstep mode. If you want to have the motor step at a different

microstep mode, change the settings for one of the MS# pins. Check the

truth table in the Hardware Overview section, if you need a reminder of

what settings are enabled by the various pin states.

// 1/16th microstep foward mode function

void SmallStepMode()

{

Serial.println("Stepping at 1/16th microstep mode.");

digitalWrite(dir, LOW); //Pull direction pin low to move "fo

rward"

digitalWrite(MS1, HIGH); //Pull MS1,MS2, and MS3 high to se

t logic to 1/16th microstep resolution

digitalWrite(MS2, HIGH);

digitalWrite(MS3, HIGH);

for(x= 1; x<1000; x++) //Loop the forward stepping enough t

imes for motion to be visible

{

digitalWrite(stp,HIGH); //Trigger one step forward

delay(1);

digitalWrite(stp,LOW); //Pull step pin low so it can be tr

iggered again

delay(1);

}

Serial.println("Enter new option");

Serial.println();

}

The final motor function available shows how the motor can change

direction on the fly. The function works just as the forward and reverse

functions above, but switches between states quickly. This example will

step the motor 1000 steps forward and then reverse 1000 steps. This

allows you to precisely move something with the motor in one direction, and

return to the starting position exactly. Precise position control is a great

benefit of stepper motors!

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//Forward/reverse stepping function

void ForwardBackwardStep()

{

Serial.println("Alternate between stepping forward and rever

se.");

for(x= 1; x<5; x++) //Loop the forward stepping enough time

s for motion to be visible

{

//Read direction pin state and change it

state=digitalRead(dir);

if(state == HIGH)

{

digitalWrite(dir, LOW);

}

else if(state ==LOW)

{

digitalWrite(dir,HIGH);

}

for(y=1; y<1000; y++)

{

digitalWrite(stp,HIGH); //Trigger one step

delay(1);

digitalWrite(stp,LOW); //Pull step pin low so it can be

triggered again

delay(1);

}

Serial.println("Enter new option");

Serial.println();

}

Additional Examples

In addition to the example here, you can also install the AccelStepper

Library. There are some additional examples with this library that may be

beneficial to you for use with your Big Easy Driver. Download this and

install the library in your Arduino libraries directory.

Resources and Going Further

Going Further

Now that you’ve successfully got your Big Easy Driver up and running, it’s

time to incorporate it into your own project!

If you have any feedback, please visit the comments or contact our

technical support team at TechSupport@sparkfun.com.

Additional Resources

Check out these additional resources for more information and other project

ideas.

• Schmalz Haus Big Easy Driver Homepage

• GitHub Repository

• A4988 Datasheet

• The Great American Tweet Race

• Autonomous Vehicle Competition

• Arduino Controlled Ouija Board

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