Experiment Guide for the SparkFun Tinker Kit

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Experiment 9: Driving a Motor with an H-Bridge

Introduction

How could you make a motor spin in different directions? With an H-Bridge! In this experiment you will use the H-Bridge to control the motor’s direction and speed.

Parts Needed

You will need the following parts:

  • 1x Breadboard
  • 1x SparkFun RedBoard
  • 1x SN754410 H-Bridge IC
  • 1x 48:1 Geared Motor
  • 12x Jumper Wires

Didn’t Get the Tinker Kit?

If you are conducting this experiment and didn’t get the Tinker Kit, we suggest using these parts:

Breadboard - Self-Adhesive (White)

PRT-12002
$4.95
36
Hobby Gearmotor - 200 RPM (Pair)

ROB-13302
$3.95
Jumper Wires - Connected 6" (M/M, 20 pack)

PRT-12795
$1.95
2
H-Bridge Motor Driver 1A

COM-00315
$2.35
1

DEV-12757
127 Retired

Introducing the H-Bridge

The SN754410 is an Integrated Circuit (IC), called an H-Bridge, that makes controlling motors easier. An H-Bridge allows you to control both the direction and the amount of an electrical current being supplied to a motor. You can think of it as a smart valve that allows you to change the direction of the current passing through the motor.

To switch the direction of the current, you use two pins to toggle pins on the board either HIGH or LOW. If the two direction pins are both HIGH or LOW at the same time, that causes the board to brake the motors. If one pin is HIGH and the other is LOW, the motor spins in one direction. If you flip-flop the states, the motor spins in the opposite direction. The IC is also powered separately with 5V supplied to pin 16 on the IC, and up to 36V for the motor voltage on pin 8 of the IC.

WARNING: You will be using voltage that may be higher than the limit of the circuitry on your RedBoard allows! Make sure you keep motor voltage (MV) isolated from other circuitry! Accidentally using MV to power other circuitry may cause irreparable damage to your RedBoard!

You can control up to two motors with a single IC. You can use this diagram as a reference for pin numbers in conjunction with the table below.

Image courtesy of ITP at NYU

Hookup Table

1 PWM signal for controlling the speed of motor A
2 Direction pin 1 for motor A
3 Motor A connection 1
4 Ground / Heat Sink
5 Ground / Heat Sink
6 Motor A connection 2
7 Direction pin 2 for motor A
8 Motor supply voltage
9 PWM signal for controlling the speed of motor B
10 Direction pin 1 for motor B
11 Motor B connection 1
12 Ground / Heat Sink
13 Ground / Heat Sink
14 Motor B connection 2
15 Direction pin 2 for motor B
16 Chip voltage (5V)

Hardware Hookup

Ready to start hooking everything up? Check out the wiring diagram below to see how everything is connected.

Pay special attention to the component’s markings indicating how to place it on the breadboard. Polarized components can only be connected to a circuit in one direction.
Note: It is possible that you may need to bend the legs of your H-Bridge in slightly for it to line up with the breadboard. You can do this by using a table top as a flat surface and gently "roll" the IC using the table to bend the pins until they are vertical.

Wiring Diagram for the Experiment

alt text

Having a hard time seeing the circuit? Click on the wiring diagram for a closer look.

Open the Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit.

You can type out or copy and paste the following code into the Arduino IDE. Hit upload, and see what happens!

language:cpp
/*
SparkFun Tinker Kit
Example sketch 9

SparkFun Motor Driver

Use the SparkFun Motor Driver to control the speed and direction of a motor

This sketch was written by SparkFun Electronics,
with lots of help from the Arduino community.
This code is completely free for any use.
Visit http://learn.sparkfun.com/products/2 for SIK information.
Visit http://www.arduino.cc to learn more about Arduino.
*/

//define the two direction logic pins and the speed / PWM pin
const int DIR_A = 5;
const int DIR_B = 4;
const int PWM = 6;

void setup()
{
//set all pins as output
pinMode(DIR_A, OUTPUT);
pinMode(DIR_B, OUTPUT);
pinMode(PWM, OUTPUT);
}

void loop()
{
 //drive forward at full speed by pulling DIR_A High
 //and DIR_B low, while writing a full 255 to PWM to 
 //control speed
 digitalWrite(DIR_A, HIGH);
 digitalWrite(DIR_B, LOW);
 analogWrite(PWM, 255);

 //wait 1 second
 delay(1000);

 //Brake the motor by pulling both direction pins to 
 //the same state (in this case LOW). PWM doesn't matter
 //in a brake situation, but set as 0.
 digitalWrite(DIR_A, LOW);
 digitalWrite(DIR_B, LOW);
 analogWrite(PWM, 0);

 //wait 1 second
 delay(1000);

 //change direction to reverse by flipping the states
 //of the direction pins from their forward state
 digitalWrite(DIR_A, LOW);
 digitalWrite(DIR_B, HIGH);
 analogWrite(PWM, 150);

 //wait 1 second
 delay(1000);

 //Brake again
 digitalWrite(DIR_A, LOW);
 digitalWrite(DIR_B, LOW);
 analogWrite(PWM, 0);

 //wait 1 second
 delay(1000);
 }

Code to Note

language:cpp
digitalWrite(DIR_A, HIGH);
digitalWrite(DIR_B, LOW);
analogWrite(PWM, 255);

The Motor Driver uses a control logic that works by pulling certain pins HIGH or LOW (pins 4 and 5 in this case) to change the direction of the motor’s rotation and then send a PWM signal to pin 6 to control the speed. This chunk of code runs to motor in one direction at full speed.

language:cpp
digitalWrite(DIR_A, LOW);
digitalWrite(DIR_B, HIGH);
analogWrite(PWM, 150);

This chunk of code is similar, but changes the direction by flipping the direction pin’s state and setting the PWM pin at a slower speed.

language:cpp
digitalWrite(DIR_A, LOW);
digitalWrite(DIR_B, LOW);
analogWrite(PWM, 0);

This final chunk of code demonstrates the logic for stopping or “braking” the motor by pulling both direction pins to the same state. In this case we used LOW, but both set to HIGH would produce the same results. In a brake, the PWM level doesn’t matter. We set it to 0 as more of a formality than anything. If not, see the Troubleshooting section below.

What You Should See

You should see the motor spin in one direction at full speed for one second, then brake (stop) for one second, and run at a slower speed for a second in the opposite direction and and then repeat.

Tinker Kit Circuit 9

Troubleshooting

Motor Not Spinning

Make sure that you have the enable pin as well as the logic and PWM pins wired correctly. It’s easy to make a wiring error, as the names of the pins of the board are on the bottom.

Motor Spinning in Only One Direction

Double check your code. You may not have inverted the logic pin’s state to reverse the motor.