Book Image

Hands-On Robotics with JavaScript

By : Kassandra Perch
Book Image

Hands-On Robotics with JavaScript

By: Kassandra Perch

Overview of this book

JavaScript has an effective set of frameworks and libraries that provide support for embedded device programming and the robotics ecosystem. You’ll be able to put your JavaScript knowledge to work with this practical robotics guide. The book starts by guiding you in setting up an environment to program robots with JavaScript and Rasberry Pi 3. You will build beginner-level projects, such as a line-following robot, and then upgrade your robotics skills with a series of projects that help you get to grips with the Johnny-Five library. As you progress, you’ll learn how you can improve your projects by enabling advanced hardware components and programming concepts. You’ll even build an advanced AI-enabled robot, connect its NodeBots to the internet, create a NodeBots Swarm, and explore Message Queuing Telemetry Transport (MQTT). By the end of this book, you will have enhanced your robot programming skills by building a range of simple to complex projects.

Related Content you might be interested in

Current Title:

Small book image
Hands-On Robotics with JavaScript
Kassandra Perch
Aug, 2018 | 214 pages
Small book image
Practical Python Programming for IoT
Gary Smart
Nov, 2020 | 516 pages
Small book image
Internet of Things with Raspberry Pi 3
Maneesh Rao
Apr, 2018 | 248 pages
Small book image
Learn Robotics Programming
Danny Staple
Feb, 2021 | 602 pages
Table of Contents (19 chapters)
Title Page
Title Page
Dedication
Dedication
Packt Upsell
Packt Upsell
Contributors
Contributors
Preface
Preface
Free Chapter
1
Setting Up Your Development Environment
Setting Up Your Development Environment
Technical requirements
What is the Raspberry Pi?
How we will use the Raspberry Pi
Installing the operating system
Setting up your password and hardware interfaces
Installing Node.js, Johnny-Five, and Raspi-IO
Summary
Questions
Further reading
2
Creating Your First Johnny-Five Project
Creating Your First Johnny-Five Project
Technical requirements
Creating a project folder
Getting started with Johnny-Five and Raspi-IO
Wiring up an LED
Making the LED blink
Summary
Questions
Further reading
3
Building Interactive Projects with RGB LED
Building Interactive Projects with RGB LED
Technical requirements
Looking at the LED and LED.RGB API
PWM pins and GPIO expanders
Bringing in other node packages
The REPL – a powerful tool in Johnny-Five
Summary
Questions
Further reading
4
Bringing in Input with Buttons
Bringing in Input with Buttons
Technical requirements
Using inputs in robotics projects
The Johnny-Five button object
Wiring up buttons
Adding buttons to our RGB LED project
Summary
Questions
Further reading
5
Using a Light Sensor to Create a Night-Light
Using a Light Sensor to Create a Night-Light
Technical requirements
Using an analog sensor with the Pi
The ambient light sensor
Creating our night-light
Summary
Questions
Further reading
6
Using Motors to Move Your Project
Using Motors to Move Your Project
Technical requirements
More about motors
Preparing for a motor-driven project with Raspberry Pi
The Johnny-Five motor object
Troubleshooting your motorized projects
Project – cat toy
Project – using two gearbox motors and the motors object
Summary
Questions
7
Using Servos for Measured Movement
Using Servos for Measured Movement
Technical requirements
Differences between motors and servos
Getting a servo working with Johnny-Five
Project – two servos and the REPL
Project – light meter with the servo
Project – the continuous servo
Summary
Questions
8
The Animation Library
The Animation Library
Technical requirements
Animating movement
The terminology of the animation library
The construction of the animation object
Easing into your servo animations
Learning more about queuing and playing animation segments
Summary
Questions
9
Getting the Information You Need
Getting the Information You Need
Technical requirements
Why connect your NodeBots to the internet?
Getting weather data on our Pi with OpenWeatherMap
Building a weather dashboard with an LCD
Project – scraping data from websites with your Pi
Summary
Questions
Further reading
10
Using MQTT to Talk to Things on the Internet
Using MQTT to Talk to Things on the Internet
Technical requirements
IoT device communications
MQTT - an IoT PubSub protocol
Setting up MQTT on the Pi with AdafruitIO
Project – adding an LCD and button to see and send MQTT events
Project – social media notifier bot with IFTTT
Summary
Questions
Further reading
11
Building a NodeBots Swarm
Building a NodeBots Swarm
Technical requirements
Project – connecting multiple NodeBots
Expanding your NodeBots knowledge
Continuing on your NodeBots adventure
Summary
Assessments
Assessments
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10
Other Books You May Enjoy
Other Books You May Enjoy
Leave a review - let other readers know what you think
Index
Index

PWM pins and GPIO expanders

Before we wire up and run our RGB LED project, a discussion about PWM pins and GPIO expanders is warranted, because these are topics that will affect most Johnny-Five projects that you will complete.

How do PWM pins work?

You don't always want an LED to at its full brightness, especially in the case of RGB LEDs, where the brightness of each channel (red, green, and blue) determines the perceived color of the LED. The pins on most microcontrollers are digital: they are either HIGH at 5V or LOW at 0V. So how do you adjust the brightness of an LED with these types of pins? The answer involves the idea of average voltage and the speed at which we can flip a digital pin from HIGH to LOW. 

Pulse-width modulation, or PWM, pins operate by setting, effectively, the percentage of time that a pin is HIGH and LOW. The following screenshot shows an oscilloscope reading for the state of a pin running at 50% over a short period of time:

 

 

 

 

 

 

 

 

 

 

Oscilloscope reading for a 50% PWM...

Previous Section
End of Section 4
Next Section