Easy Driver Hook-up Guide

SparkFun Electronics

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Easy Driver Hook-up Guide
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Introduction
The Easy Driver gives you the capability to drive bipolar stepper motors
between 150mA to 700mA per phase.
Materials Required
To follow along with this tutorial, we recommend you have access to the
following materials.
Stepper Motor with Cable
ROB-09238
This is a simple, but very powerful stepper motor with a 4-wire cable a…
Female Headers
PRT-00115
Single row of 40-holes, female header. Can be cut to size with a pair
SparkFun RedBoard - Programmed with Arduino
DEV-12757
A
t SparkFun we use many Arduinos and we're always looking for the
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
You can either solder directly to the Easy Driver, or use headers for
attaching power supplies, motors, etc. The best option for you will be
dependent on your application.
Suggested Reading
Page 1 of 10
If you aren’t familiar with the following concepts, we recommend reviewing
them before beginning to work with the Easy Driver.
Installing the Arduino IDE
How to Power Your Project
Battery Technologies
How to Solder
Working with Wire
Motor Basics
Hardware Overview
The Easy Driver is designed by Brian Schmalz, and is designed around the
A3967 IC. This IC enables you to drive bipolar stepper motors that are 4, 6,
or 8-wire configurations. The board can either work with 3.3V or 5V
systems, making it extremely versatile. Two mounting holes on-board give
the user the option to mechanically stabilize the Easy Driver.
Pin Descriptions
Let’s take a look at all of the pins broken out from the A3967 IC on the Easy
Driver.
Board Top Pins
If you look across the top of the board, you will see several pins.
They function as follows:
Coil A+ - H-Bridge 2 Output A. Half of connection point for bi-polar
stepper motor coil A.
Coil A- - H-Bridge 2 Output B. Half of connection point for bi-polar
stepper motor coil A.
Coil B+ - H-Bridge 1 Output A. Half of connection point for bi-polar
stepper motor coil B.
Coil B- - H-Bridge 1 Output B. Half of connection point for bi-polar
stepper motor coil B.
PFD - Voltage input that selects output current decay mode. If PFD >
0.6Vcc, slow decay mode is activated. If PFD < 0.21Vcc, fast decay
mode is activated. Mixed decay occurs at 0.21Vcc< PFD < 0.6Vcc.
RST - Logic Input. When set LOW, all STEP commands are ignored
and all FET functionality is turned off. Must be pulled HIGH to enable
STEP control.
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.
MS2 -Logic Input. See truth table below for HIGH/LOW functionality.
GND - Ground.
M+ - Power Supply. 6-30V, 2A supply.
Bottom Board Pins
There are also pins across the bottom of the board. Their functions are
described below.
GND - Ground.
5V -Output. This pin can be used to power external circuitry. 70mA
max is required for Easy Driver functionality.
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SLP - Logic Input. When pulled LOW , outputs are disabled and power
consumption is minimized.
MS1 - Logic Input. See truth table below for HIGH/LOW functionality.
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. This will either be 0-5V or
0-3.3V, based on the logic selection.
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. This will either be
0-5V or 0-3.3V, based on the logic selection.
Microstep Select Resolution Truth Table
MS1 MS2 Microstep Resolution
L L Full Step (2 Phase)
HL Half Step
L H Quarter Step
H H Eigth Step
Solder Jumpers
There are two solder jumpers on board. These provide the following
features to the user:
3/5V - 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.
APWR - This jumper allows the user to source Vcc on the 5V/GND
pins to external hardware.
Potentiometer
The potentiometer on board is included to allow users the ability to select
the max current provided to the motor. It ranges from 150mA to 750mA.
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
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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 our NEMA 16 Stepper Motor with
Cable.
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 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.
Easy Driver Motor
•A+ Green Wire
•A- Red Wire
•B+ Blue Wire
•B- Yellow Wire
Note: Do not connect or disconnect the motor while the Easy
Driver is powered.
Connect a Power Supply
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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 6V to 30V.
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 the SparkFun RedBoard. 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.
RedBoard Easy Driver
•D2 STEP
•D3 DIR
•D4 MS1
•D5 MS2
•D6 ENABLE
Final Circuit
Once you have everything connected, your circuit should look like the
following:
Arduino Code
Basic Arduino Code Example
Now that you have the hardware hooked up and ready to go, it’s time to get
the code uploaded. First, download the example sketch.
EASY DRIVER DEMO SKETCH DOWNLOAD
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
Redboard and the Easy Driver. It also sets these pins as outputs, and puts
them to the proper logic levels to begin driving the motor.
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//Declare pin functions on Redboard
#define stp 2
#define dir 3
#define MS1 4
#define MS2 5
#define EN 6
//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(EN, OUTPUT);
resetEDPins(); //Set step, direction, microstep and enable p
ins 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 1/8th 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 RedBoard 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 RedBoard prints an error over the serial port.
After the requested function is completed, the pins on the 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 allow mo
tor 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.");
}
resetEDPins();
}
}
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 ‘forward’ 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 RedBoard 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
Page 7 of 10
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
Easy Driver provides. To enable the motor to step in 1/8th microsteps, we
must set MS1, and MS2 HIGH . This sets the logic of the board to 1/8th
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.
// 1/8th microstep foward mode function
void SmallStepMode()
{
Serial.println("Stepping at 1/8th microstep mode.");
digitalWrite(dir, LOW); //Pull direction pin low to move "fo
rward"
digitalWrite(MS1, HIGH); //Pull MS1, and MS2 high to set log
ic to 1/8th microstep resolution
digitalWrite(MS2, 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!
Page 8 of 10
//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 Easy Driver. Download this and install
the library in your Arduino libraries directory.
You can also find some additional examples on Brian’s Easy Driver page
here.
Resources and Going Further
Going Further
Once you’ve successfully gotten your Easy Driver controlling stepper
motors, it’s time to incorporate this into your own project! Will it be your own
CNC machine? Or perhaps a remote controlled turning art installation? Let
us know!
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 Easy Driver Homepage
GitHub Repository
A3967 Datasheet
The Great American Tweet Race
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Autonomous Vehicle Competition
Arduino Controlled Ouija Board
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