NEW
Our∧ resident expert on all things
robotic is merely an email away.
roboto@servomagazine.com
Tap into the sum of all human knowledge and get your questions answered here!
From software algorithms to material selection, Mr. Roboto strives to meet you
where you are — and what more would you expect from a complex service droid?
by
Dennis Clark
Q. I’ve seen posts and even
some articles that use various
ways to create a wireless
connection from a robot to a
computer. How easy is it to configure
a wireless connection? I am easily
confused by the jargon and have
held off getting anything because
I don’t want to waste my money on
something I’ll never get to work.
— Paul Humour
A. You aren’t the first to feel
intimidated by the technology
and the terminology. Most
robotics hobbyists are not experts in
all things and can use a hand up on
occasion. I too have pondered the
mysteries of wireless communications.
Sometimes it just seems like magic.
Since you mentioned the word
Figure 1. Zoom Bluetooth USB adapter.
14 SERVO 04.2008
“money,” I’m going to assume that
cost is a factor in your choice of
wireless technology, so I’ll go into
detail about two very affordable
options for hobbyists that wish to
“unwire” their robots. The first is
Bluetooth and the second is Zigbee.
Both of these technologies are 2.54
GHz low power wireless radios. That is
to say that their power is in the 1 m W
to 60 m W range, which means we
can expect to get ranges from 50 feet
to 300 feet, depending upon where
we are. Inside, the ranges are less
than outside for a variety of reasons.
Since I doubt that you want to
hear about multi-path reflections and
dBm readings, I’ll focus instead on
how to configure them on your
computer and your robot. Along the
way, I’ll give the costs and options
that seem most affordable and that I
know work. Finally, I recognize that
not everyone uses a Windows PC;
some use Macs and some Linux. I
will show how to configure for the
Windows and Mac platforms; I don’t
have a Linux machine, sorry. There
are a LOT of steps in these procedures
below; even so, I left the most
obvious ones out and focused on
the steps that were either confusing
or hard to discover.
Using Bluetooth
The first wireless solution that
I’ll talk about is Bluetooth. Bluetooth
works by explicitly pairing a master to
a slave. This is what we want to do,
so that is fine by us. There are dozens
of ways to get Bluetooth on your
computer, so which should we
choose? If you have Bluetooth built in,
then your solution is complete on the
computer side. If you don’t, then you
need to get a USB Bluetooth adapter.
I looked at several and chose two
that were middle of the road in cost,
meaning $20 or less. The first one I
tested was the Zoom 4320AF model
which retails for about $20 (see
Figure 1). The second one I tested
was the Azio Bluetooth V2.0 + EDR
model for about $17.
Next we need to have a Bluetooth
device to connect to. The people at
www.sparkfun.com have several
reasonably priced units to choose
from. I chose the two lowest priced
ones that had what I wanted, namely
a simple connection interface. The
first one is the Bluesmirf WRL08332
board. They sell this for about $50.
Bluetooth says it has a 30M (100 feet)
range, indoors I’d give it about 50
feet. SparkFun has a longer range unit
— the Bluesmirf WRL00582 — that
sells for about $65 and has a 100M
(300 feet) range. Note that these
ranges are line-of-sight outdoors;
indoors you just don’t get that range.
These modules are super simple to
use. They have six pins: Power ( 3.3V
to 6V), Ground, Tx out, Tx in, RTS out,
and CTS in. You simply need to supply
power and ground, connect the Tx
in line with the Rx line of your robot
