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Home > IoT & Hardware > Single Board Computers > Learning Lego Mindstorms EV3
Learning Lego Mindstorms EV3
Learning Lego Mindstorms EV3

Learning Lego Mindstorms EV3: Build and create interactive, sensor-based robots using your LEGO MINDSTORMS EV3 kit

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Learning Lego Mindstorms EV3

Chapter 2. Mechanical Design

In this chapter, we will build and program several models to demonstrate the basic principles of mechanical design. We will:

  • Explore the idea of mechanical advantage
  • Learn how you can increase either speed or torque using different combinations of gears
  • Build gearboxes with motors
  • Use the spur gears, beveled gears, and worm gears
  • Write a program to spin the motors a set number of rotations
  • Use the display on the EV3 brick

All of the models in this chapter can be built with both the EV3 Home Edition and EV3 Educational Edition kits.

Mechanical advantage

When designing a robot, sometimes we may want to build a fast robot that needs to get to its objective quickly. At other times, we may want a powerful robot. For instance, maybe the robot needs to push a heavy object, push another robot, or climb a steep hill. When it comes to a robotic arm, we might be trying to lift a heavy object slowly or lift a small object quickly.

However, we cannot have both speed and power. There is a trade-off here—if you increase one, you decrease the other. This trade-off is called the law of conservation of energy.

Mechanical advantage

LEGO bricks allow us to use several types of simple machines. The simplest would be the lever arm. You can easily create a lever with LEGO beams and pins. To balance a seesaw or a lever, the amount of torque or rotational force must be the same on either side of the seesaw. In the preceding image, we see a LEGO balance with unequal forces but equal lever arms. The longer the lever arm, the less force we need to rotate...

Motors

The EV3 kit comes with two large motors and one medium motor. Beyond the packaging, there are some other important differences between the large motor and the medium motor. The following list compares the features of the large and medium motor:

  • Large motor maximum speed 170 rpm
  • Medium motor maximum speed 250 rpm
  • Large motor torque when rotating 0.21 N∙m (Newton-meters is a unit used to measure torque)
  • Medium motor torque when rotating 0.08 N∙m
  • Large motor torque at standstill 0.42 N∙m
  • Medium motor torque at standstill 0.12 N∙m
  • Large motor mass is 76 grams
  • Medium motor mass is 36 grams

The large motor will be excellent to power the drive train of our robot, and if you need the extra speed, you can always gear the motors up. If you need more torque, you can gear down. The medium motor is about half the mass of the large motor. The medium motor actually spins about 50 percent faster than the large motor. The torque of the medium motor is only a fraction of the large...

Large motors and gears

We will be building a simple gear train with two gears powered by the large motor. The gears we are using are double bevel gears. Normally, when you think of a gear, you are thinking of a straight or a spur gear. The LEGO double bevel gear is essentially a spur gear in the middle, with beveled edges on both sides. Not only does this allow you to combine two double bevel gears aligned parallel to each other as we are in this section, but you can also combine them at right angles, as we will see later in this chapter. I chose this particular set of gears because they are included in both the Home Edition and Educational Edition kits. However, you could build a gear train like this using any set of dissimilar gears. The small gear has 12 teeth, and the large gear has 36 teeth. The motor will power the larger gear. We will find that every time the large gear spins once, the small gear will spin three times. So we are gaining speed, but at the cost of losing torque. This...

Writing a program

After we attach the cables, we will be ready to write a program to make the motor spin. Connect the motor to port D on your EV3 brick. Turn on your EV3 brick by pressing the dark gray button in the center of the brick.

After you start up the EV3 software, navigate to File | New Project | Program. This will start up a new program. You could easily start one of the many LEGO tutorials at this point. We will start with a blank sheet. The startup menu you see in the following screenshot is the main difference between the Home Edition version of the software and the Educational Edition. Additionally, the Home Edition does not allow you to do experiments.

Writing a program

You will see several icons at the bottom of the screen on the green Action tab of the Programming Palette. Drag a Large Motor block (encircled in red in the following screenshot) onto the Programming Canvas and place it next to the Start block.

Writing a program

Although not required, you can add a Stop block at the end of the program. You can...

Bevel gears at right angles

In the next example, we are going to build a gearbox using a 12-tooth bevel gear along with the large 36 tooth straight gear with double bevels. These gears actually rotate at right angles to each other. Since the motor drives the smaller gear, the output of our gearbox is actually slower than the motor. However, we will gain torque in this system, so we have a mechanical advantage of 3. We will be using the medium motor in this model.

Bevel gears at right angles

In the following five steps, we will build a gearbox with two gears at right angles:

  1. First attach two friction pins to the medium motor.
    Bevel gears at right angles
  2. Next, attach the open frame to the motor. The open frame is essentially our gearbox.
    Bevel gears at right angles
  3. Next, place the 8-mod axle (with stop) and the beveled gear into the medium motor. Make sure the axle fits into the motor.
    Bevel gears at right angles
  4. Now, insert the large gear and an axle into your gearbox. The teeth of both the gears should interlock.
    Bevel gears at right angles
  5. Finally, add a flag so you can see the rotations of the large gear.
    Bevel gears at right angles

Next, write this simple...

Mechanical advantage

When designing a robot, sometimes we may want to build a fast robot that needs to get to its objective quickly. At other times, we may want a powerful robot. For instance, maybe the robot needs to push a heavy object, push another robot, or climb a steep hill. When it comes to a robotic arm, we might be trying to lift a heavy object slowly or lift a small object quickly.

However, we cannot have both speed and power. There is a trade-off here—if you increase one, you decrease the other. This trade-off is called the law of conservation of energy.

LEGO bricks allow us to use several types of simple machines. The simplest would be the lever arm. You can easily create a lever with LEGO beams and pins. To balance a seesaw or a lever, the amount of torque or rotational force must be the same on either side of the seesaw. In the preceding image, we see a LEGO balance with unequal forces but equal lever arms. The longer the lever arm, the less force we need to rotate the lever...

Motors

The EV3 kit comes with two large motors and one medium motor. Beyond the packaging, there are some other important differences between the large motor and the medium motor. The following list compares the features of the large and medium motor:

  • Large motor maximum speed 170 rpm

  • Medium motor maximum speed 250 rpm

  • Large motor torque when rotating 0.21 N∙m (Newton-meters is a unit used to measure torque)

  • Medium motor torque when rotating 0.08 N∙m

  • Large motor torque at standstill 0.42 N∙m

  • Medium motor torque at standstill 0.12 N∙m

  • Large motor mass is 76 grams

  • Medium motor mass is 36 grams

The large motor will be excellent to power the drive train of our robot, and if you need the extra speed, you can always gear the motors up. If you need more torque, you can gear down. The medium motor is about half the mass of the large motor. The medium motor actually spins about 50 percent faster than the large motor. The torque of the medium motor is only a fraction of the large motor. This makes the medium...

Large motors and gears

We will be building a simple gear train with two gears powered by the large motor. The gears we are using are double bevel gears. Normally, when you think of a gear, you are thinking of a straight or a spur gear. The LEGO double bevel gear is essentially a spur gear in the middle, with beveled edges on both sides. Not only does this allow you to combine two double bevel gears aligned parallel to each other as we are in this section, but you can also combine them at right angles, as we will see later in this chapter. I chose this particular set of gears because they are included in both the Home Edition and Educational Edition kits. However, you could build a gear train like this using any set of dissimilar gears. The small gear has 12 teeth, and the large gear has 36 teeth. The motor will power the larger gear. We will find that every time the large gear spins once, the small gear will spin three times. So we are gaining speed, but at the cost of losing torque. This...

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Description

This book is for the hobbyists, builders, and programmers who want to build and control their very own robots beyond the capabilities provided with the LEGO EV3 kit. You will need the LEGO MINDSTORMS EV3 kit for this book. The book is compatible with both the Home Edition and the Educational Edition of the kit. You should already have a rudimentary knowledge of general programming concepts and will need to have gone through the basic introductory material provided by the official LEGO EV3 tutorials.

What you will learn

  • Design a robot for optimum navigation and place sensors for optimal calibration
  • Control multiple robots through a master robot
  • Decipher the advanced programs developed by LEGO
  • Account for weight and balance issues in your design
  • Calibrate the sensors using buttons on the robot
  • Utilize core programming concepts such as loops, case structures, calculations, variables, and arrays
  • Enhance your programs with proportional and PID control

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Jan 27, 2015
Length: 284 pages
Edition : 1st
Language : English
ISBN-13 : 9781783985036
Vendor :
Lego
Category :
IoT & Hardware
Concepts :
Single Board Computers
Tools :
Lego Mindstorms

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Product Details

Publication date : Jan 27, 2015
Length: 284 pages
Edition : 1st
Language : English
ISBN-13 : 9781783985036
Vendor :
Lego
Category :
IoT & Hardware
Concepts :
Single Board Computers
Tools :
Lego Mindstorms

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Learning Lego Mindstorms EV3
Learning Lego Mindstorms EV3
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Jan 2015 284 pages
Full star icon 4.1 (14)
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Building Smart LEGO MINDSTORMS EV3 Robots
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Building Smart LEGO MINDSTORMS EV3 Robots
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Table of Contents

13 Chapters
1. Engineering Notebook Chevron down icon Chevron up icon
1. Engineering Notebook
The engineering design process
Content Editor features
New pages and page actions
Computer-aided Design and building instructions
Commenting on your code
Summary
2. Mechanical Design Chevron down icon Chevron up icon
2. Mechanical Design
Mechanical advantage
Motors
Large motors and gears
Writing a program
Bevel gears at right angles
Worm gear
Using wires and parallel threads
Summary
3. Drive Train and Chassis Chevron down icon Chevron up icon
3. Drive Train and Chassis
Chassis
Skid-bot with the Retail kit
Caster-bot with the Educational kit
Tread-bot with the Retail kit
Tread-bot with the Educational kit
Programming the robot to move forward
Summary
4. Sensors and Control Chevron down icon Chevron up icon
4. Sensors and Control
Using sensors
Programming blocks
LEGO EV3 sensors
Third-party sensors
Summary
5. Interacting with EV3 Chevron down icon Chevron up icon
5. Interacting with EV3
Push buttons
IR remote buttons
Bluetooth control
Smart device control
Wi-Fi control
Summary
6. Output from EV3 Chevron down icon Chevron up icon
6. Output from EV3
Display
Image Editor
Display data
Brick lights
Legacy NXT/RCX lights
Sound
Music
Summary
7. Advanced Programming Chevron down icon Chevron up icon
7. Advanced Programming
Loop and the Motor Rotation sensors
Loop and the Gyro Sensor
Switch or two-level controller
Three-level controller
Subroutines or My Blocks
Arrays
Summary
8. Advanced Programming and Control Chevron down icon Chevron up icon
8. Advanced Programming and Control
Distance controller
Infrared versus Ultrasonic
Proportional algorithm
Line following using the Color Sensor
Setpoint for line tracking
Two-level or bang-bang controller
Proportional line follower
PID controller
Gyro Sensor
IR sensor navigation and beacon tracking
Tracking a circle
Triangulation
Summary
9. Experiment Software and Data Logging Chevron down icon Chevron up icon
9. Experiment Software and Data Logging
Data logging software
Improving dead reckoning
Analyzing gain constants
Graphical programming
Other bang-bang controllers
Summary
10. Other Programming Languages Chevron down icon Chevron up icon
10. Other Programming Languages
LabVIEW
RobotC
Summary
11. Communication between Robots Chevron down icon Chevron up icon
11. Communication between Robots
Enabling communication
Messaging
Summary
12. Advanced Robot – Gyro Boy Chevron down icon Chevron up icon
12. Advanced Robot – Gyro Boy
Concept of a balancing robot
The Gyro Boy model
Programming bugbears
The main program
The control program
The RST My Block
The gOS My Block
The GT My Block
The GG My Block
The GM My Block
The EQ My Block
The cntrl My Block
The CHK My Block
Summary
Index Chevron down icon Chevron up icon
Index

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Rating distribution
Full star icon Full star icon Full star icon Full star icon Half star icon 4.1
(14 Ratings)
5 star 50%
4 star 28.6%
3 star 7.1%
2 star 7.1%
1 star 7.1%
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Marc Helfman Jul 15, 2019
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I've been doing Lego Robotics ever since the original RCX kit came out in 1998. They finally got the software right with the EV3 and the more you delve into it, the more you'll appreciate it. This book does an excellent job of exploring all the EV3 has to offer.
Amazon Verified review Amazon
Csaba Csanaki Mar 23, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This is a very in-depth, detailed book how to discover, learn and work with EV3.The book contains lot of codes, plans from simple to complex.
Amazon Verified review Amazon
Glenn Nov 02, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Walks you through from the basics to the advanced level,on programming and provides inspiration to go farther.
Amazon Verified review Amazon
steven Mar 18, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This is a great book explaining how to learn to work with Lego Mindstorms EV3 with lot's of code explanations and building plans! This is a MUST HAVE for every EV3 user out there... for both Retail and Education owner!
Amazon Verified review Amazon
I. Luv Sushi Jul 10, 2018
Full star icon Full star icon Full star icon Full star icon Full star icon 5
For anyone wishing to take the Mindstorm EV3 beyond the realm of a toy, this is an excellent book. Using the knowledge gained I was able to build a custom robot utilizing all the sensors.Highly recommended.
Amazon Verified review Amazon

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About the author

Profile icon Garber
Garber
Gary Garber teaches physics, math, and engineering at Boston University Academy. Gary is the president of the New England Section of the American Association of Physics Teachers and has led dozens of professional development workshops in education at both the local and national levels. Gary runs the Boston University FIRST Robotics program. He has run and hosted numerous robotics workshops in VEX, Tetrix, and LEGO platforms. He has run dozens of LEGO robotics tournaments and spoken on robotics education at both local and national conferences. His robotics team has worked with Engineers Without Borders, NASA, and the National Science Teachers Association on a variety of engineering and education projects. He is currently an educational consultant, working to develop new software tools for the classroom, at the Tufts Center for Engineering Education and Outreach, which is a pioneer in LEGO Robotics Education. He is the author of Instant LEGO MINDSTORMS EV3, Packt Publishing. He currently resides in Massachusetts, US. When he is not playing with LEGO, robots, or toy trains, he enjoys spending time with his wife, Catalina, and their two children, Alejandro and Leonardo.
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