Making Robots With The Arduino part 1.pdf

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Making Robots

With The

A RDUINO

Part 1

By Gordon McComb

Twenty years ago, I began work on my ultimate home robot. Its brain was

an Intel 80286-based PC motherboard, running at a whopping 8 MHz. The

robot used a floppy disc drive to load the operating system and programs,

and custom prototype boards for external interfacing.

the battery alone weighing some 15 pounds, I

needed a sturdy frame to keep everything together.

Constructed of aluminum, the robot measured 18

inches square by almost three feet high, and required heavy

duty and expensive gear motors — all this just to meander

down the hallway and scare the &@%! out of my cat.

Five years and over $1,500 later, I put “Maximillian” to

rest, pulling its parts to use in other projects. Robot

electronics were shrinking, and that meant robots

themselves were getting smaller. Innovations like the BASIC

Stamp made it much easier to experiment with low cost,

self-contained microcontrollers — perhaps the ideal robotic

brain. Microcontrollers are now so commonplace that you

have your pick of hundreds of makes and models; from the

super simple, to the confoundedly complex. Somewhere in

the middle is the Arduino — a small and affordable

microcontroller development board that’s fast becoming

something of a superstar.

handle the most common things microcontrollers can do.

And let’s not forget that some of its fame has to do with

price: the standard Arduino costs about $30, assembled

and tested. Even less if you want to build it from a kit.

Then there’s its free programming software. Using a

standard USB cable, it lets you easily connect the Arduino

to your computer — Windows, Mac, or Linux — and begin

working in minutes. The programming editor is simple to

use and comes with several dozen examples to get you

started.

What’s really made the Arduino a darling of geeks the

world over is this: Both its hardware design and software

are open source. That means others are able to take the

best ideas and improve on them, all without paying

licensing fees. This has created something of a cottage

industry of fans and third-party support.

Though the most popular version of the Arduino is

made by a company in Italy (where the board was originally

developed), many others offer compatible designs in one

form or another. Add to this a growing body of add-ons

that maximize the Arduino, and free resources for

programming examples, code libraries, and step-by-step

tutorials.

Why the Popularity?

Sure, the Arduino is a capable little critter able to

56 SERVO 11.2010

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T he beast needed a hefty battery for power, and with

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www.servomagazine.com/index.php?/magazine/article/november2010_McComb

Introducing Arduino Robotics

So, it makes sense to look at ways to leverage the

Arduino to build robots. That’s exactly what we’ll be doing

in this article and several more to follow in the months

ahead. I’ll show you how to build, program, and use an

economical and expandable autonomous desktop robot

— the ArdBot — that’s powered by an Arduino. Cost of the

project is under $85 — even less if you already have some

basic components like a solderless breadboard and hookup

wire.

The robot base is simple to build and can be

constructed out of a variety of materials; no special tools

are required. I’ll demonstrate a version made of expanded

PVC plastic, but you can use heavy cardboard, foam board,

picture frame mat board, or most any other material you

like. (For your convenience, you can get the robot chassis

precut with all the hardware; see the Sources box for more

information.)

I believe in robot designs that let you explore and

experiment, and the ArdBot leaves plenty of room for

expansion and independent discovery. You can use the

robot for line or wall following, maze solving, or general

meandering around in a room. (Cat scaring optional.) You

can also take the concepts presented here and design your

own version of the ArdBot — bigger or smaller, wheels or

tracks — your choice.

In this installment, you’ll learn all about the Arduino:

what it’s made of, how to connect it to your computer, and

how to start developing robot projects for it. You’ll also be

introduced to the ArdBot chassis, including where to get its

main parts. In coming installments to this series, you’ll

explore programming the robot to do interesting things,

and extending its features with sensors and other add-ins.

FIGURE 1. The Arduino Duo is a compact microcontroller board

based on the Atmel ATmega328 chip. It’s available from a

number of sources at about $30 average retail.

number of Arduino boards that had been manufactured by

that time; many more have been made since).

The Uno, Duemilanove, and Diecimila are what might

be called main or core board designs. These all share a

common form factor which is a PCB that measures 2-1/8”

by 2-3/4”. All contain a power jack for a 2.1 mm (center

positive) barrel connector, as well as a USB Type B jack for

hooking up to a host computer.

A series of 28 female pin headers allow connection of

external devices to the Arduino. The headers are separated

into three groups as shown in Figure 2 . The groups are:

power, analog input, and digital input/output. Of the 28

pins, 20 are devoted to input and output. There are six

analog input pins which can also serve as general-purpose

digital I/O. The 14 digital input/output pins include six that

can be used to generate PWM (pulse width modulated)

signals; these are useful for such things as controlling the

Arduino Under the Hood

First introduced in 2005, the Arduino has gone through

numerous iterations, revisions, and

improvements. As I’m writing this, the

Arduino team just released their newest

version: the Arduino Uno (see Figure 1 ).

Like its predecessors, the Uno is an all-in-

one development board. It contains an

Atmel AVR microcontroller — specifically

the ATmega328 — a USB-to-serial

interface, five volt voltage regulator, and

various support electronics.

Previous iterations of the Arduino

have included the Duemilanove (which

means 2009 in Italian) and the Diecimila

which means 10,000 (a reference to the

FIGURE 2. Points of interest on the Arduino

board include the USB and power jacks,

function and power LEDs, and rows of

connection headers.

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Table 1. Arduino at a Glance.

hardware like switches, motors, lights, relays, sensors, and

LEDs. At the heart of the Arduino is an Atmel AVR

microcontroller. The exact version of AVR controller

depends on the version of the Arduino. For example, the

older Diecimila and the first Duemilanove versions used an

AVR ATmega168; the second generation Duemilanove

(referred to as 2009b) as well as the Uno, use the AVR

ATmega328. The ‘328 is physically identical to the ‘168 but

it contains more memory space. See TABLES 1 and 2 for

details on variations between the controller chips used.

The bulk of the components on the Arduino are

surface-mount, but on most Arduino boards the AVR

microcontroller is provided in a dual inline pin (DIP)

package. This permits easy replacement should that ever be

needed. A new AVR chip costs maybe $5 or $6; that’s a lot

cheaper than replacing the entire Arduino board.

Keep in mind that the AVR provided in commercially

manufactured Arduino boards comes with a bootloader

program pre-installed in its Flash memory. This bootloader

allows you to program the Arduino by using a USB

connection to your PC. When replacing the AVR

microcontroller of an Arduino, you need to either purchase

a chip with the bootloader software pre-installed, or if you

have the proper hardware setup — like an Atmel STK500

programmer — you can do it yourself. Instructions for

downloading bootloader software into an AVR chip are

provided on the main Arduino information page.

Arduino Version

Microcontroller

Supports Standard

Expansion Shields

Uno and

Duemilanove

(2009b)

ATmega328

Yes

Duemilanove

(pre-2009b) and

Diecimila

ATmega168

Yes

Mega 2560

ATmega2560

Nano, Mini,

LilyPad, others

ATmega168 or

ATmega328

Table 2. Microcontroller

Specifications.

ATmega168 ATmega328 ATmega2560

Flash memory

16 KB; 2 KB

used by

bootloader

32 KB; 0.5 KB

used by

bootloader

256 KB; 8 KB

used by

bootloader

SRAM

1 KB

2 KB

8 KB

EEPROM

512 bytes

1 KB

4 KB

Clock speed

16 MHz

Many Variations on a Theme

speed of motors. Through its I/O pins, the Arduino

supports the basic inter-communications standards: TTL

serial, SPI, 1-Wire, and I 2 C. Two of its pins (digital I/O lines

2 and 3) support hardware interrupts that via software

trigger on a LOW value, a rising or falling edge, or a

change in value.

Like any microcontroller, the Arduino is basically a small

single-board computer designed to interface to external

The core board designs of the Uno, Duemilanove, and

Diecimila are perhaps the most common and popular of the

Arduinos, but there are numerous other variations. Here are

just some of the standardized Arduino boards you’ll

encounter. The Arduino BT and Fio are intended for wireless

applications. The BT contains a Bluetooth module; the Fio

has a built-in Zigbee radio. (You can also readily add

Bluetooth and Zigbee to an Uno or other core board using

“shields” detailed below.)

The Nano is a compact stick-shaped board made for

breadboard use. It has all the main features of the Uno and

others (including built-in USB jack), but measures only 0.73”

x 1.7”. It uses only surface-mount parts.

The Mini is even smaller, and is ideal for very small bots

with limited space. The Mini lacks its own USB jack, and

requires the use of a USB adapter or serial TTL connection

to the host PC for programming. The Mini has four analog

input pins instead of the six or eight of the other versions.

The Mega2560 is based on a larger AVR chip, and it

offers over three times the number of analog and digital

I/O lines (see TABLE 3 ). Memory and program space are

bigger, too. The Arduino Mega2560 contains 256 KB of

Flash (by comparison, the Uno has 32 KB), as well as more

RAM and EEPROM space. Use this for the bigger jobs.

Several Arduino resellers (such as Solarbotics and

Adafruit) offer their own custom offshoots of the Arduino

— these typically go by different names such as Boarduino

Table 3. Arduino Pin Resources.

Arduino Uno, Duemilanove, and Diecimila

Digital I/O Pins

14 (of which six provide

PWM output)

Analog Input Pins

Nano

Digital I/O Pins

14 (of which six provide

PWM output)

Analog Input Pins

Mega 2560

Digital I/O Pins

54 (of which 14 provide

PWM output)

Analog Input Pins

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or Freeduino to differentiate them from the original Arduino

designs. The Adafruit Boarduino (available in kit form for

under $18) is like the Arduino Nano. It uses thru-hole

components for ease of soldering.

Some variations of the Arduino depart from the

standard form-factor of the Uno, and are not designed for

use with expansion shields (discussed below). A good

example is the LilyPad — a special Arduino layout

engineered for making (among other things) wearable

microcontroller projects. Think Borg implants, only more

friendly looking. The flower-shaped LilyPad has a flat profile

and can be sewn into fabric. It has connection points on

the ends of its 22 petals.

With so many variations of the Arduino floating

around, it’s easy to get confused. For the ArdBot, we’ll be

using an Arduino Duo, but you can readily substitute just

about any of the other versions. If you already have an

earlier Duemilanove or even Diecimila, you can use it with

the ArdBot. The only catch is that you’ll need to make sure

you have an up-to-date Arduino programming environment

installed on your computer. I’ve tested everything with

version 0019 of the Arduino programming IDE (discussed

later), so with that version or anything later you should be

good to go.

the Arduino Duo and related core boards support on-board

USB. You merely need to connect a suitable USB cable

between the Arduino and your computer. The cable even

provides the power to the board. The necessary USB drivers

are provided with the Arduino software. In most cases,

installation of the drivers is not fully automatic, but the

steps are straightforward and the Arduino support pages

provide a walk-through example.

The Arduino accepts a standard USB Type B connector.

Your PC probably uses the larger Type A connector, so you

need a Type A to Type B USB cable. Keep in mind that

some PCs and laptops may use Mini-A or Mini-B connectors,

so check first before purchasing a cable for use with the

Arduino.

Operating voltage of the Arduino circuitry is five volts

which is supplied either by the USB cable when it’s plugged

into a USB port on your computer, or by a built-in linear

regulator when the board is powered externally. The

regulator is intended to be powered by 7-12 VDC; a nine

Main Components

This is a SELECTED list of North American sources for the

main components for the ArdBot.

Ready Expansion Via Shields

Arduino Duo or Duemilanove

Source

Item or SKU

The Arduino is an example of the KISS principle. Its

simple design helps keep costs down, and makes the

Arduino a universal development board adaptable to just

about anything. While there are more expensive specialty

versions of the Arduino made for robotics applications, the

basic board lacks connectors to directly attach to motors,

sensors, or other devices.

The Arduino itself has no breadboard area, but it’s easy

enough to connect any of the inputs or outputs to a small

breadboard via wires. For an application like robotics, you’ll

want to expand the Arduino I/O headers to make it easier

to plug in things like motors, switches, and ultrasonic or

infrared sensors.

One method is to use an add-on expansion board

known as a shield. These stick directly on top of the core

board designs (Uno, Duemilanove, and Diecimila). Pins on

the underside of the shield insert directly into the Arduino’s

I/O headers. Two popular expansion shields are the

solderless breadboard and the proto shield; both provide

prototyping areas for expanding your circuit designs.

Of course, you don’t absolutely need a shield to expand

the Arduino. You can place a breadboard — solderless or

otherwise — beside the Arduino, and use ribbon cables or

hookup wire to connect the two together. This is the

approach we’ll be using with the ArdBot described in this

series of articles.

Adafruit

HVW Tech

28920 (Freeduino SB)

RobotShop

RB-Ard-03

SparkFun

DEV-09950

Solderless breadboard, 170 tie-points

Source

Item or SKU

Adafruit

HVW Tech

21380

Parallax

700-00012

RobotShop

RB-Spa-139

Continuous rotation servo (Futaba spline)

Source

Item or SKU

Parallax

900-00008

Pololu

1248

RobotShop

RB-Gws-23

Solarbotics

36000

SparkFun

ROB-09347

2-1/2” or 2-5/8” rubber wheels

(Futaba spline)

Source

Item or SKU

Adafruit

167

HVW Tech,

Solarbotics

Parallax

28109

USB Connection and Power

Pololu

226

RobotShop

RB-Sbo-86

To allow the easiest possible means of programming,

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separate four-cell AA battery holder is used for servo

motors and other components that don’t require voltage

regulation.

Indicator LEDs are provided on the Arduino for testing

and verification. A small green LED shows power; two other

LEDs show serial transmit and receive activity and should

flash when the board is being programmed from your

computer. A fourth LED is connected in parallel with digital

I/O line 13 and serves as a simple way to test the Arduino

and make sure it is working properly. We’ll use this feature

in a simple example later on in this article.

Programming the Arduino

FIGURE 3. The Arduino integrated development environment (IDE)

provides a centralized place to write, compile, and download

programs to the Arduino board.

Microcontrollers depend on a host computer for

developing and compiling programs. The software used on

the host computer is known as an integrated development

environment, or IDE. For the Arduino, the development

environment is based on the open source Processing

platform ( www.processing.org ) which is described by its

creators as a “programming language and environment for

people who want to program images, animation, and

interactions.“

The Arduino programming language leverages an open

source project known as Wiring ( wiring.org.co ). The

Arduino language is based on good old-fashioned C. If you

are unfamiliar with this language, don’t worry; it’s not hard

to learn, and the Arduino IDE provides some feedback

when you make mistakes in your programs.

volt battery is ideal. Anything higher than 12 volts is not

recommended as it could cause the regulator to overheat.

For robotics, I think it’s best to power the Arduino from

its own battery. The ArdBot uses a split supply where the

Arduino is powered by a nine volt transistor battery; a

Sources

HVW Technologies

www.hvwtech.com

Reseller of Arduino products and manufacturer

(with Solarbotics) of the Freeduino SB .

Adafruit Industries

www.adafruit.com

Arduino resellers and custom shield projects. Convenient

premade nine volt battery clip and 2.1 mm barrel connector

(see product #80), and nine volt battery holder with switch

(product #67).

Parallax

www.parallax.com

Not resellers of Arduino, but they offer continuous rotation

servos, wheels, and sensors.

Pololu

www.pololu.com

Wheels, continuous rotation servo motors.

Arduino

www.arduino.cc

The main Arduino site provides downloads, tutorials,

references, design schematics, and other information useful

for learning about and using the Arduino family of boards.

RobotShop

www.robotshop.ca (Canada); www.robotshop.us (US)

Full service retailer carrying most all of the official

Arduino lineup, plus servo motors, solderless breadboards,

and sensors.

Atmel

www.atmel.com/products/AVR

Manufacturers of the AVR microcontrollers used in the

Arduino. See their site for datasheets (in PDF format).

Solarbotics

www.solarbotics.com

Continuous rotation servos, five-cell AA battery packs

with attached 2.1 mm barrel connector, Arduino, and

Arduino-clone boards.

Budget Robotics

www.budgetrobotics.com

Custom machined decks, servo mounting hardware, and

assembly hardware for the ArdBot.

SparkFun Electronics

www.sparkfun.com

Reseller of the Arduino and manufacturer of custom

Arduino-like hardware.

Freeduino

www.freeduino.org

Home of the Freeduino collaborative project.

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