Building a Sonar System
I’ve always wanted to do an
ultrasonic ranging project. So,
guess what we’ll be talking about
and building up this month?
Ultrasonic ranging is a great way
to add eyes to your mechanical
animal. I’ll bet you didn’t realize
that there is an off-the-shelf
ultrasonic ranging product out
there that allows you to tune
those “electromechanical eyes”
to your robot’s environment.
by Fred Eady
If you scan the pages of SERVO carefully, you’ll come
across a company called MaxBotix. They produce a line
of ultrasonic ranging devices that take the hassle out of
implementing a viable ultrasonic ranging application. Each
of MaxBotix’s LV-MaxSonar rangefinders has a differing
beam pattern that results in a unique detection pattern.
This allows you — the ultrasonic ranging system designer —
to pick an LV-MaxSonar that is right for your application.
Ultrasonic rangefinders with wide beam widths
are better suited for “eye” applications. An eye application
FIGURE 1. This illustration makes it easy to comprehend
the differing detection patterns of the line of MaxBotix
LV-MaxSonar ultrasonic sensors. The really cool thing is that
all of the LV-MaxSonar sensors have the same ranging data
interface. This set of lobe shots demonstrates the ranging of
various diameter dowels on a one foot grid.
LV-MaxSonar®-EZ
beam patterns
Detection pattern
to a 1/8 inch
diameter dowel.
Detection pattern
to a 1/4 inch
diameter dowel.
Detection pattern
to a 1 inch
diameter dowel.
Detection pattern
to a 3 1/4 inch
diameter dowel.
5V
3.3V
V+ supply voltage,
(Distances overlaid on a 1 foot grid.)
42 SERVO 06.2008
EZ0™ EZ1™ EZ2™ EZ3™ EZ4™
may need to detect obstacles, avoid collisions, or sense
the presence of a humanoid. Wide beams also are very
good at detecting small objects due to their higher
sensitivity.
MaxBotix offers LV-MaxSonar ultrasonic rangefinders
that produce a narrow beam. These narrow beam
rangefinders are good for ranging and room mapping. A
narrow beam LV-MaxSonar rangefinder will do a better job
at operating in cluttered and “high noise” environments as
its beam is a bit less sensitive in the center. However, you
can use a narrow beam ultrasonic rangefinder to do the
work of a wide beam ultrasonic rangefinder if that’s what is
right for your application.
The LV-MaxSonar ultrasonic rangefinder line is
composed of five models. As you can see in Figure 1, the
EZ0 is the wide beam ultrasonic rangefinder model and is
the most sensitive. The EZ1 emits a narrower beam than
the EZ0, which makes it more suitable for sensing humans.
The MaxBotix LV-MaxSonar-EZ2 produces a beam that is
even narrower than the EZ1. The beam width narrows
progressively from
PHOTO 1. The LV-
MaxSonar-EZ0 you see
here is a combination
of the MaxBotix
MaxSonar-UT ultrasonic
transducer and the
proprietary circuitry
you see in Schematic 1.
Another reason for not
getting too deep with
the inner workings of
the EZ0 is that there
is no technical
information available
from MaxBotix for the
ultrasonic transducer.
