Chapter 10 - Exploring Stepper Motors (28-BYJ-48) with an Arduino

Summary

Este script ofrece una introducción a cómo controlar el motor paso a paso 28BYJ-48 con Arduino, una herramienta popular para proyectos de electrónica. Se discute la estructura del motor, su alto torque a baja velocidad y su uso en aplicaciones que requieren control preciso de posición y velocidad. Se explica cómo se organizan las bobinas en fases y cómo se activan secuencialmente para mover el rotor. Se presenta un diagrama esquemático del controlador ULN2003 y cómo se conecta a Arduino. Además, se incluye un ejemplo de código para controlar el motor, así como una discusión sobre la precisión y especificaciones técnicas del motor, incluyendo su relación de reducción de engranajes y el ángulo de paso. Finalmente, se menciona la biblioteca de Arduino para steppers y se comparan las secuencias de 4 y 8 pasos, así como se habla de las placas de motor (shields) como una alternativa para controlar motores.

Takeaways

• 😀 El video es una introducción al control de motores paso a paso 28BYJ-48 con Arduino.
• 🔧 Se utiliza un motor paso a paso popular y ampliamente disponible para demostraciones.
• 📚 Se recomienda revisar capítulos 4, 5, 8 y 9 para comprender mejor este resumen.
• 🤖 Los motores paso a paso son útiles para aplicaciones que requieren posicionamiento preciso y control de velocidad.
• 🌀 Estos motores ofrecen alto torque a baja velocidad, pero tienen menos torque a alta velocidad y consumen corriente constante.
• 🪢 El motor 28BYJ-48 es unipolar, con cuatro bobinas asociadas a cables de colores que se controlan mediante un driver ULN2003.
• 🔌 El controlador ULN2003 utiliza transistores y diodos para conectar las bobinas al motor y se controla con señales de Arduino.
• 🔋 Se debe verificar la especificación de voltaje y corriente del motor para asegurarse de que Arduino pueda manejar la carga.
• 📝 Se muestra cómo conectar los pines de Arduino al controlador y un potenciómetro al pin analógico para control de velocidad.
• 🔄 Se discuten las secuencias de pulsos necesarias para mover el motor en sentido horario e antihorario.
• 🎛 El ángulo de paso del motor y la relación de reducción de engranajes son clave para la precisión en el posicionamiento del motor.
• 🔄 Se menciona la posibilidad de desalineación o 'slippage' debido a la complejidad de los engranajes internos del motor.
• 📚 Se presenta la biblioteca de Arduino para motores paso a paso, que simplifica el proceso de control del motor.
• 🛠 Se mencionan alternativas como las shields de motor que facilitan la conexión y control de motores con Arduino.

Q & A

¿Qué es un motor paso a paso y cómo funciona?

Un motor paso a paso es un tipo de motor DC que se puede controlar para moverse en pasos discretos, lo cual es ideal para aplicaciones que requieren una posición y control de velocidad precisos. Funciona a través de múltiples bobinas organizadas en fases que, al ser electrificadas secuencialmente, hacen girar la motor en pasos sucesivos.

¿Por qué se usan motores paso a paso en lugar de otros tipos de motores?

Los motores paso a paso son útiles debido a su alta precisión y control de posición y velocidad, además de ofrecer un alto torque en precisión a bajas velocidades, algo que no es típico en los motores DC comunes.

¿Cuáles son las desventajas de usar motores paso a paso?

Los motores paso a paso tienen menos torque a altas velocidades, consumen corriente constante independientemente de la carga, lo que significa que no son tan eficientes, y a diferencia de los servos, no tienen un mecanismo de retroalimentación para determinar su posición.

¿Qué es el controlador de motor ULN2003 y cómo se utiliza con un motor paso a paso?

El controlador de motor ULN2003 es un chip que contiene transistores y diodos útiles para electrificar las bobinas múltiples de un motor paso a paso. Se utiliza para controlar la dirección y velocidad de la rotación al determinar la secuencia utilizada para llevar a tierra cada una de las bobinas.

¿Cómo se conecta un motor paso a paso 28BYJ-48 a un Arduino?

El motor 28BYJ-48 es unipolar, y sus cables naranja, rosa, amarillo y azul están asociados con cuatro bobinas diferentes. Se conecta a un Arduino utilizando el chip de controlador de motor ULN2003, donde los pines de Arduino se conectan a este chip para controlar qué bobina se electrifica.

¿Qué es la relación de reducción de engranajes y cómo afecta el motor paso a paso?

La relación de reducción de engranajes se refiere a cómo el eje del motor gira las salidas de engranajes. En el caso del motor 28BYJ-48, una relación de 1 a 64 significa que 64 revoluciones del eje del motor giran un eje de salida completo.

¿Cuál es el ángulo de paso del motor paso a paso 28BYJ-48 y cómo se calcula?

El ángulo de paso del motor 28BYJ-48 es de 5.625 grados por paso en una secuencia de 8 pasos, resultando en 64 pasos por revolución. Se calcula dividiendo 360 grados entre el ángulo de paso por paso.

¿Cómo se puede controlar la dirección y velocidad de un motor paso a paso con Arduino?

La dirección y velocidad de un motor paso a paso se pueden controlar mediante la secuencia y el tiempo de los impulsos en los pines de Arduino que están conectados al controlador de motor ULN2003.

¿Qué es la biblioteca de motor paso a paso de Arduino y cómo se utiliza?

La biblioteca de motor paso a paso de Arduino permite construir objetos de tipo 'Stepper'. Al definir estos objetos, se le indica el número de pasos necesarios para una revolución en el eje de salida del motor y los pines de Arduino que están conectados al motor. La biblioteca proporciona funciones como 'step' para inducir rotación.

¿Qué son las placas de motor y cómo facilitan el uso de motores con Arduino?

Las placas de motor, o motor shields, son hardware que se puede adjuntar a un Arduino que maneja todos los transistores, diodos y puentes H,简化了布线工作。 Proporcionan bibliotecas personalizadas que simplifican la escritura de programas para tus proyectos.

¿Cómo se puede corregir el error de la posición del eje de salida debido al deslizamiento rotativo en un motor paso a paso?

El deslizamiento rotativo puede introducir un error de hasta tres grados en la posición del eje de salida. Para corregir esto, se puede calibrar el código agregando pasos adicionales, como se menciona en el script, para alcanzar los ángulos deseados.

Outlines

00:00

🤖 Introducción al control de motores paso a paso con Arduino

El primer párrafo presenta una introducción al control de motores paso a paso 28BYJ-48 utilizando Arduino. Se menciona que la presentación se basa en recursos en línea y es la última en una serie de 10 capítulos para un espacio de hackers en Tucson, Arizona. Se sugiere que los capítulos 4, 5, 8 y 9 sean revisados para comprender mejor este resumen. Los motores paso a paso son DC que se controlan en pasos discretos, ideales para aplicaciones que requieren posicionamiento preciso y control de velocidad. A pesar de su alto torque en bajas velocidades, presentan desventajas como menor eficiencia a altas velocidades y la falta de un mecanismo de retroalimentación de posición. Se describe cómo funcionan los motores paso a paso, con múltiples bobinas organizadas en fases que, al ser activadas secuencialmente, hacen girar el motor. Además, se introduce el uso del controlador de motor ULN 2003 para gestionar la activación de las bobinas.

05:02

🔌 Configuración y conexión del motor paso a paso a Arduino

Este párrafo se enfoca en la configuración y conexión del motor paso a paso al Arduino. Se discuten las especificaciones de voltaje y corriente que soporta el motor, indicando que no se necesita una fuente de alimentación externa si no hay carga significativa. Se describe el proceso de conexión de los pines del Arduino al controlador del motor y el uso de un potenciómetro conectado a un pin analógico para controlar la velocidad del motor. Se sugiere el uso de un código de ejemplo y se ofrece un enlace al mismo en el sitio web del presentador. Se detalla cómo se encierra todo en una caja para una demostración más práctica y cómo se realiza la conexión entre los pines del Arduino y el controlador del motor, así como el potenciómetro.

10:04

🔄 Funcionamiento y control del motor paso a paso

El tercer párrafo explica cómo funciona el motor paso a paso y cómo controlarlo. Se describe el proceso de generación de un campo magnético al aplicar corriente a las bobinas, lo que induce el movimiento del rotor. Se ilustra cómo se puede controlar la dirección y velocidad del motor variando la secuencia y el tiempo de encendido de los pines del Arduino. Se detalla el código utilizado para inducir movimientos en sentido horario y antihorario, y se muestra cómo se activan las bobinas a través de los pines del Arduino. Además, se menciona la utilización de LEDs en el controlador del motor para visualizar el funcionamiento del motor.

15:04

📏 Precisión y especificaciones del motor paso a paso

Este segmento se centra en la precisión y especificaciones técnicas del motor paso a paso. Se discute el concepto de relación de reducción de engranajes, que indica cómo muchas vueltas del eje del motor son necesarias para una vuelta en el eje de salida. Se calcula que 64 pasos del eje del motor resultan en una vuelta completa del eje de salida. Se describe el ángulo de paso del motor, que es la cantidad de rotación que produce cada paso en el eje del motor, y cómo esto se traduce en pasos necesarios para una vuelta completa del eje de salida. Se realiza un cálculo para determinar la cantidad de secuencias de pasos que deben ser llamadas para obtener una vuelta completa o parcial del eje de salida.

20:05

🔍 Solución de problemas y consideraciones adicionales

En este párrafo, el autor narra su experiencia al enfrentarse a un problema de precisión en el motor paso a paso. Después de varias pruebas y ajustes, se descubre que hay un margen de error debido al deslizamiento rotativo en el eje de salida, lo que puede introducir una diferencia de hasta tres grados. Esto llevó al autor a calibrar su código añadiendo pasos adicionales para alcanzar ángulos precisos. También se menciona la biblioteca de motores paso a paso incluida en el software de Arduino, que simplifica el proceso de construcción de objetos 'stepper' y el control de los mismos, aunque utiliza una secuencia de cuatro pasos en lugar de la secuencia de ocho pasos que se había estado utilizando hasta ese momento.

25:24

🛠️ Uso de shields de motor y conclusiones

El sexto y último párrafo habla sobre los shields de motor, que son piezas de hardware que se pueden adjuntar a Arduino para manejar transistores, diodos y puentes H,简化布线过程. Se hace hincapié en la importancia de revisar las especificaciones y limitaciones de potencia de cualquier shield que se considere, y se comparan opciones de proveedores confiables con clones más baratos disponibles en línea. Se concluye la serie de 10 capítulos desarrollada para el hackerspace, animando a los espectadores a dar like y suscribirse para futuras demostraciones y códigos asociados con las invensiones del presentador.

Keywords

💡Arduino

Arduino es una plataforma de prototipado de hardware de código abierto que permite a los diseñadores y artistas crear proyectos interactivos a través de la programación de circuitos electrónicos. En el video, Arduino se utiliza para controlar un motor paso a paso 28BYJ-48, mostrando cómo este dispositivo puede ser utilizado en proyectos de electrónica para lograr movimientos precisos y control de velocidad.

💡Motor paso a paso 28BYJ-48

El motor paso a paso 28BYJ-48 es un tipo de motor que se mueve en pasos discretos, lo que lo hace ideal para aplicaciones que requieren una posición y control de velocidad precisos. En el video, se detalla cómo controlar este motor utilizando un Arduino, destacando su popularidad y disponibilidad para proyectos de electrónica.

💡Unipolar

Un motor unipolar es aquel en el que todas las bobinas están conectadas a un solo tap central de voltaje común, a diferencia de los motores bipolares que tienen bobinas separadas. En el video, se menciona que el 28BYJ-48 es un motor unipolar, lo que significa que para activar una bobina se conecta su extremo a tierra, un concepto clave para entender cómo se controla el motor.

💡Controlador de motor ULN2003

El controlador de motor ULN2003 es un chip que contiene transistores y diodos, utilizados para controlar la conexión de múltiples bobinas en un motor paso a paso. En el video, se describe cómo este chip permite el control del motor 28BYJ-48 desde un Arduino, mediante señales que activan los transistores y, por ende, la secuencia de bobinas energizadas.

💡Potenciometro

Un potenciometro es un dispositivo de control analógico que varía la resistencia en una circuito a medida que se rota o se desliza. En el contexto del video, se utiliza un potenciometro para controlar la velocidad y dirección del motor paso a paso, permitiendo al usuario ajustar la velocidad de rotación del motor a través de un Arduino.

💡Resolución de paso

La resolución de paso se refiere a la cantidad de pasos que un motor paso a paso puede realizar para dar una vuelta completa. En el video, se discute cómo la resolución de paso varía entre secuencias de 4 y 8 pasos, afectando tanto la precisión del movimiento como la torque del motor.

💡Relación de reducción de engranajes

La relación de reducción de engranajes es la proporción entre las revoluciones del eje del motor y las revoluciones del eje de salida. En el video, se explica que una relación de reducción de 1 a 64 significa que se necesitan 64 revoluciones del eje del motor para obtener una revolución en el eje de salida, lo que es crucial para entender cómo se traducen los pasos del motor en movimientos más amplios.

💡Secuencia de paso

Una secuencia de paso es la forma en que se activan las bobinas de un motor paso a paso para lograr un movimiento. En el video, se describen dos tipos de secuencias de paso: la secuencia de 4 pasos y la de 8 pasos, donde cada una tiene implicaciones para la resolución y el torque del motor.

💡Biblioteca de motor paso a paso de Arduino

La biblioteca de motor paso a paso de Arduino es un conjunto de funciones predefinidas que facilitan el control de motores paso a paso sin necesidad de programar cada paso manualmente. En el video, se menciona cómo esta biblioteca simplifica el proceso de control del motor 28BYJ-48, permitiendo al usuario enfocarse en la lógica del movimiento en lugar de los detalles de hardware.

💡Placa de motor

Una placa de motor, o motor shield, es un accesorio que se puede conectar a un Arduino para facilitar el control de motores. En el video, se discuten las ventajas de usar una placa de motor, como la simplificación del proceso de conexión y la inclusión de bibliotecas personalizadas, aunque también se advierte sobre las posibles limitaciones de potencia y calidad en diferentes marcas.

Highlights

Introduction to controlling the 28BYJ-48 stepper motor with Arduino.

Stepper motors are suitable for precise positioning and speed control applications.

28BYJ-48 is a unipolar stepper motor with four coils controlled via a common 5V center tap.

ULN2003 motor driver chip explanation for managing multiple coils in stepper motors.

Wiring the Arduino to control the stepper motor direction and speed.

Explanation of stepper motor phases and how they induce motion in the rotor.

Use of a potentiometer to control motor speed in the demonstration setup.

Demonstration of the stepper motor's rotation and control using Arduino code.

Understanding the gear reduction ratio and its impact on output shaft rotation.

Calculating the number of motor shaft steps needed for a full output shaft revolution.

Difference between 4-step and 8-step sequences for stepper motors.

Adjustments needed for using the Arduino stepper library with the 28BYJ-48.

Practical demonstration of the stepper motor making full and half revolutions.

Issue of rotational slip in stepper motors and its effect on precision.

Using motor shields for simplified stepper motor control with Arduino.

Recommendations for purchasing motor shields and considerations for specifications.

Conclusion of the 10-part series on Arduino with a call to action for feedback and subscription.

Transcripts

hello and welcome to this introduction

to Arduino in this chapter I'll

demonstrate how to control the popular

and widely available 28 byj 48 stepper

motor with your Arduino this

presentation borrows from many online

sources so thanks in advance to all of

you who posted your own research online

to help me reverse engineer how these

little motors work this is the final

chapter in a 10 part series developed

for local hackerspace here in Tucson

Arizona if you haven't already I

recommend reviewing chapters 4 5 8 and 9

in order to get the most out of this

summary but if you're short on time

don't worry too much about it so this is

the setup that I'll be using throughout

this presentation to demonstrate

steppers these are just DC motors that

can be controlled so that they move in

discrete steps and for this reason

they're great for applications that

require precise positioning and speed

control they also offer hight torque in

precision at low speed which is not

typical of common DC motors on the

downside they have less torque at

high-speed draw constant current

independent of load so they're not as

efficient and unlike servos have no

feedback mechanism for determining their

position also understanding and

programming these can be a little tricky

which is why broke steppers out from

chapter 9 on motors and servos in order

to help the move in discrete steps

stepper motors have multiple coils that

are organized in groups called phases

surrounding magnets on a rotor by

energizing each phase in sequence the

motor will rotate one step at a time

here's a simple conceptual model of how

these steppers work in this simple

demonstration we have a magnet on a

rotor adjacent to a coil that has no

current flowing through it as such

there's nothing to induce motion of the

magnet however if we apply current to

the coil the magnetic field generated by

that coil will attract the magnet

attached to the rotor until the magnetic

fields are aligned

now if we Orient many of these coils

around our magnet you can see how we can

pulse those coils to induce continuous

movement in the rotor these are two

examples of how we might drive a stepper

motor each method has its benefits and

limitations as we'll discuss shortly I

haven't seen stepper motors included in

most starter kits so if you'd like to

play with 128 byj 48 stepper is a good

place to start these appear to be quite

popular for use with Arduinos and

there's plenty of documentation online

on how to do the same the 28 byj 48 is a

unipolar stepper in this stepper the

orange pink yellow and blue leads are

associated with one of four different

coils as shown in the schematic on the

right all of the coils are attached to a

common 5 volt Center tap which is what

makes this a unipolar stepper with this

stepper we can determine which coil to

energize by pulling the terminal end of

a coil of interest to ground

as will demonstrate shortly we can

control the direction of rotation by

determining the sequence used to ground

each one of these coils

so how do you manage which coil to

ground

well this stepper usually comes with a

ul n 2003 motor driver chip this chip

contains a series of transistors and

diodes useful for grounding the multiple

coils in your stepper motor as was

described in chapter 9

specifically by pulsing transistors with

signals from your Arduino pins

here's a schematic of the uln 2003 with

some annotations to help explain how the

current flows on the left you can see we

have four Arduino pins attached to the

motor driver chip you can use any GPIO

pins on your Arduino for the same on the

right we have for motor coils attached

to a common 5 volt tab the common tab is

the design used for unipolar motors

although these coils have a 5 volt

potential the coils cannot ground

because of the transistors in the uln

2003 as such there's no current flowing

through the coils we can change this by

sending some current to the transistor

vo one of the Arduino pins this allows

the potential running through the coil

to ground thus inducing current flow

through the respective coil the

resulting magnetic field in the coil

will induce movement in stepper motor we

can control the direction and speed of

the stepper depending on the sequence

and timing for the firing of those

Arduino pins as will be demonstrated

shortly

when exploring the stepper with Arduino

we should check the specifications for

the voltage and the current draw for

this stepper we can expect maximum

current draw of three hundred and twenty

milli amps which is just under what we

can pull off our five volt pin when

running our Arduino off a USB cable so

assuming nothing else is plugged into

our dwee no and we're not putting a

significant load on the motor we

shouldn't need an external power supply

although many online references may

recommend using auxiliary power which is

fine to demonstrate stepper logic

I'll use this code source to one of the

forums on steppers source to the Arduino

Creative Commons website this along with

other sketches will demonstrate our copy

to my own website in the description of

this video first let's go over how to

wire things up

notice that will be using pins 8 9 10

and 11 of your Arduino to control the

stepper through the controller board and

will also be using a potentiometer wire

to analog pin number 2 also notice that

the control board power input is wired

to the 5 volt pin on the Arduino which

can provide us with up to 400 milliamps

when running off USB or 9 hundred

milliamps when plugged to an auxiliary

power supply for my demonstration I've

encased this whole thing in a box hot

glued some piano wire to a motor shaft

and added a template that lets me follow

the angle of rotation of the motor this

isn't necessary but it's a relatively

inexpensive way to create something

concrete that you can use to play with

over time if you're interested in

reproducing some of the demonstrations

that are coming up you can download the

code and the template for the 360

degrees circle from my website found in

the description of this video

the Arduino is conveniently hidden

inside the box and the wiring to the uln

2003 is fed through a hole in the back

of the box

this shows how we wire the Arduino

digital pins to the motor driver and

this shows how to wire a potentiometer

to analog pin 2 on this particular

Arduino if your Arduino doesn't come

with the second 5 volt pin like this one

you may have to attach things through a

breadboard as was shown in the original

wiring diagram a few slides back

next let's break down the sketch right

at the top of the sketch is where we

define our global variables

we build these variables for controlling

our steppers specifically through pins

eight nine ten and eleven on the arduino

and as we mentioned previously we have

our potentiometer wired up to analog pin

number two

and finally we have two variables motor

speed and pot value that will help us

set the speed of the motor as well as

store data from our potentiometer

and here's our setup block here we're

defining the Arduino pins attached to

the motor driver as output pins these

pins will engage the transistors in the

motor driver chip resulting in specific

coils being grounded in much the same

way we were grounding the DC motor coil

in our chapter 8 demonstration by

grounding the coil will induce a

magnetic field that induces the motor to

turn and here's the loop part of our

sketch the first thing we do is check

the value of our potentiometer and store

it in the variable pot value we then use

a conditional to see if pot value is

greater than or less than 535 which

determines whether to call the clockwise

or counterclockwise function

the variable pot value is also used to

calculate a value for the variable motor

speed

as mentioned earlier the sequence of

pulses on the stepper motor coils will

determine the direction of rotation here

we can see how to induce a clockwise

motion on the stepper by pulsing the

four color-coded leads coming off the

motor our sketch will induce the

sequence by setting those leads attached

to our dueño pins

8 9 10 and 11 either high or low where

the dashes in this table indicate high

and the blanks indicate low

and this is the code where we'll do that

I'll also include a snapshot of our

motor pin definitions so we know which

leads are being pulled high or low as we

go through this sequence finally I'll

also add a physical diagram of the

stepper motor itself so that we can see

how coils are being energized to induce

motion on the rotor before we walk

through this just take notice that this

function uses the motor speed value we

calculated in our loop to calculate a

delay between each step this gives us a

way to control how fast that stepper

motor turns as it's moving clockwise

here you can see that the first step of

the sequence shows that will only be

setting motor pin for high which is

attached to the orange lead and coil

number four in the stepper the other

pins will be kept low by creating a

magnetic field in coil for the steppers

rotor is induced to move next will

engage both motor pins four and three

this continues the clockwise motion in

the stepper now let's continue firing

the noted pins in the half step

switching sequence to keep that motion

going

you

and here is the total sequence shown in

the table for the half step switching

sequence for clockwise rotation

well that's fine for clockwise rotation

but what if I want to induce

counterclockwise rotation for this let's

move the clockwise function to the side

and compare it to the counterclockwise

function here you can see that the

counterclockwise function is essentially

reversing the order that those pins are

being fired in essence this is the same

as starting with a step seven in our

step sequencing table and essentially

what we're doing is running that

sequence backwards and by running a

clockwise sequence backwards this will

induce a counter clockwise sequence in

the Stuber

and here's the example stuffer one

sketch we've just outlined in action as

mentioned in my description of the code

you can see here that I'm controlling

the direction and speed of the stepper

motor using the potentiometer a really

nice thing about the uln 2003 motor

driver chip that comes with the steppers

that we can actually see the pins that

are being said I via suite of LEDs a

nice bonus for exploring out these

steppers work and if you listen closely

it almost sounds like like a little

motorcycle or the closest automotive

analogy I can come up with is it's kind

of like a rotor under a distributor cap

that's essentially making contact with

the spark plugs in an engine just kind

of cool

and this is the example stepper to

sketch here I've set the motor speed to

a large constant and this increases the

pause between each steps so that you can

see which pins are firing via the LEDs

on the motor driver chip well that's

fine for turning things forwards or

backwards but what about all that

precision positioning that steppers are

known for in order to take advantage of

that capability we need to delve a

little deeper into the stepper

specifications for this motor the specs

indicate a gear reduction ratio of 1 to

64

well what does this mean to understand

this it might help if we take the motor

apart

gear reduction has to do with the way

the motor shaft drives the output shaft

via a series of gears one two sixty four

means that sixty-four revolutions of the

motor shaft translates to one revolution

of the output shaft if you study the

gears you can kind of see how multiple

turns of the motor shaft would be needed

to create one revolution of the output

shaft but there's an easier way to

visualize this

effectively the work of all those gears

is the same as having a small gear

driving a larger gear via chain although

this drawing is not to scale you can see

that it would take many revolutions of

the small gear to generate one

revolution of the larger gear in the

case of our stepper motor it takes 64

revolutions of the motor shaft gear to

generate one revolution of the output

shaft

in order to control the motor precisely

we also have to understand the step

angle for our stepper the specifications

indicate that each step generates five

point six to five degrees of rotation on

the motor shaft in an eight step

sequence resulting in 64 steps per

revolution now that's a lot of

information so in order to understand

how this might translate to other Stuber

motors let's break this down a little

further

specifically this means that each step

in an eight step sequence will generate

five point six to five degrees of

rotation in our stepper motor shaft for

this particular sequence

since five point six to five degrees is

a fraction of the total 360 degrees

needed for a full rotation the next

question is how many of those five point

six to five degrees steps do we need to

complete one full revolution of the

stepper motor shaft

well we know that one revolution of the

motor shaft is equal to 360 degrees and

we're also told that each step produces

five point six to five degrees of

rotation if that's the case then 360

degrees can be divided by five point six

to five degrees per step and that gives

us 64 steps so that tells us that

sixty-four steps will result in one

revolution of the motor shaft which

matches the specification given for this

particular motor

well now that we understand how to

control the motor shaft we'll next want

to understand the number of motor shaft

steps it takes to generate one

revolution of the output shaft this is

important because anything we attach to

the stepper will be via the output shaft

not the motor shaft here we can see it

takes 4096 steps of the motor shaft to

generate one revolution of the output

shaft that's fine but again it really

helps to understand how they come up

with these numbers if we want to

understand how to control other steppers

outside of this one

well we know it takes 64 revolutions of

our motor shaft to generate one

revolution in our output shaft let's

write that down as our first term as we

just calculated we also know it takes 64

steps to generate one revolution of our

motor shaft if we multiply these two

terms together we get 4096 steps

necessary to generate one revolution in

our output shaft as per the given motor

specification

while that's fine for calculating the

steps I need to induce a full 360 degree

turn of my output shaft but in my sketch

I have this sequence of eight steps

embedded in a function so it's necessary

to ask how many times do I have to call

this full sequence to generate a full

revolution of the output shaft well I

know that 4096 steps will generate one

revolution of the output shaft and I

also know that one half step sequence is

made up of eight steps so if I do the

math on this this means that I have to

call this sequence 512 times to generate

one revolution of the output shaft

okay so that's fine for a full turn but

what if I wanted just a half a turn or

180 degrees on the output shaft here's

the math for that one I already know

that I need five hundred and twelve

sequences to generate one revolution of

my output shaft if I only want half a

revolution of the output shaft I just

multiply it accordingly when I do the

math I get 256 sequences so that's the

same as calling that clockwise function

256 times in my program and here's some

code to test the math you can see that

in the first for loop

I'm calling the clock wise function 512

times which should generate a full 360

degree turn in my hub foot shaft in a

clockwise motion and then I call the

counterclockwise function 512 times

which should bring the pointer on my

output shaft all the way back to 0 and

then I test the same clockwise and

counterclockwise functions using 256

which should cause a 180 degree turn

forward clockwise and then bring it back

to 0 so now let's demonstrate the

example stepper 3 sketch which includes

those 4 loops that I just summarized the

first thing I'm gonna do is try to get

this thing lined up I'm gonna reset it

and uploading and there goes my first

for loop clockwise and here it comes

back now something interesting is going

to happen you'll notice it didn't come

back all the way back to 0 here's the

180 forward here's the 180 back so that

seems a little short to

so this really bugged me because after

all I mean we just walked through all

these calculations and talked about how

precise these stuffers can be and how

you can control them with a great deal

of precision so really rack my brain to

figure out what was going on here so

what happened first it took note of this

little disclaimer that shows that the

gear reduction ratio is actually smaller

than 1 to 64 but if this were the source

of the error the step angle would be

larger and my code should be

overshooting the full and half circle

not undershooting it specifically if you

do the math with more precise gear

reduction ratio you're going to get 510

sequences instead of 512 for a full

circle and yet the code I tested has 512

and still wasn't closing the circle so

this isn't the source of the problem

well I checked the wiring in the event

coil wasn't firing correctly or in the

right order that was ok then I tried

slowing down the motor speed by an order

of magnitude in the event the coils were

firing too quickly and skipping a step

that didn't help so then I even tried

testing a second stepper and controller

board to ensure there wasn't something

wrong with the one I had set up

originally I didn't have any luck so

something else must be going on

finally I came across this thread by an

individual who tested several variations

of these steppers most important he drew

my attention to the fact that because of

all the gearing in this motor there's an

opportunity for what's known as

rotational slip in the position of the

output shaft as such this can introduce

plus or minus three degrees of error

this prompted me to calibrate my code

and after many tests I observed a need

to add four additional steps to get very

close to what I was expecting for my

half and full circle so this is just

something to keep in mind when playing

with this particular stepper if you're

trying to land on a specific angle with

your code next let's briefly talk about

the Arduino stepper library included

with our Arduino software this library

lets us construct objects of type

stepper when we first define these

objects note that we need to tell it the

number of steps needed to generate one

revolution in our output shaft in this

case we've already calculated that to be

4096 we also need to specify the Arduino

pins that are attached to our stepper

motor by using this library and the

stepper constructor to create a my

stepper object we now have access to

functions like step for inducing

rotation when using this function we

just need to indicate how many steps the

object my stepper should take when we

execute this line of code having such a

library eliminates us from having to

write complicated functions since these

are already included in the stepper dot

H library but it certainly doesn't hurt

that we went through the code since now

you have a better understanding of how

these little Stoppers are controlled

and reviewing the stepper motor

specifications notice that we're given

the heads-up that the Arduino stepper

library uses something known as a four

step sequence rather than the eight step

sequence we've been experimenting with

up to this point

so what's the difference well when

running the eight step sequence

sometimes we're grounding one coil

and sometimes we're grounding too this

gives us the ability to produce a

smaller step angle and thus greater

resolution but we do lose some torque

relative to the four step sequence we'll

discuss next

when using a four-step sequence we're

always firing two coils this improves

our torque and speed performance but at

the expense of greater power demand and

a lower stepping resolution

so instead of using the 8 step sequence

specifications we need to follow the 4

step sequence which results in double

the step angle from five point six to

five degrees to eleven point two five

degrees because the step angle has

doubled we only need half as many steps

to make a full revolution of our output

shaft or 2048 steps rather than 4096

steps

in fact you can find an example sketch

in the arduino ide called stepper one

revolution but we'll have to make a few

modifications to get it to work with the

28 byj 48 stepper for starters we need

to tell the sketch how many steps we

need per revolution of our stepper

output shaft here you can see that 200

is defined but for our stepper running

in 4 step sequence the steps will

actually be 2048 also the library

included with the arduino software

expects the stepper to be wired a little

differently so we'll need to modify this

as well as shown

finally the speed is much too high

relative to what the stepper can handle

so we want to make sure that the speed

is set to 12 or less I've saved this

code as stepper 1 revolution

2 for download from my website let's

save this code and give it a spin

finally we can't close out our

discussion of motors without mentioning

motor shields this is hardware that you

can attach to your Arduino that takes

care of all those transistors diodes and

H bridges thus saving you the trouble of

having to do much of the wiring yourself

if you're purchasing from reputable

dealers like Adafruit or spark fun

you'll get the added benefit of custom

libraries that greatly simplify writing

sketches for your inventions

one thing that you want to pay attention

to are the general specifications and

power limitations of the shield that

you're investigating for this one

offered by Adafruit you can see that we

have 1.2 amp power limitation per Bridge

it allows up to 3 amps for brief periods

of up to 20 milliseconds but you

certainly wouldn't want to exceed that

or you'd risk burning out your equipment

you can find clones at a much lower cost

on sites like eBay but don't count on

getting the great customer service

online form support or the satisfaction

of knowing that you're supporting

innovative companies like out of fruit

or spark fun having said that I'll admit

I sometimes purchase from eBay but make

sure to pay close attention to

specifications of what's being purchased

for instance here you can see that this

shield only supports half the peak

current of the board sold by Adafruit so

I hope this chapter in the series has

given you enough information to start

playing with steppers and exploring this

stepper library that comes with your

Arduino software this concludes the 10

part series developed for 0 craft so if

you found this series helpful please

give this video a thumbs up thanks for

watching and please consider subscribing

for future demonstrations and code

associated with some of my own

inventions until next time

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